Archives for : Uncategorized

Cruise Control: Finally!

I was hoping to get cruise control installed before our trip to Colorado in October.  It wasn’t strictly necessary, however, and I was still addressing a number of other handling-related issues.  After driving 1200 miles each way without it, I kept it on my TO DO list as a priority.

Today I finally got around to it.  I had purchased a replacement connector, thinking that I had cut it off by accident, and did the same thing I did with most of the fuel-injection related components.  For all the connectors I didn’t need, I cut them off and simply to taped the wires up, tucking them away in case I had a need for the circuits later.  It pays, before cutting off a connector, to ensure that you know what it’s for, first!

I spent a few hours yesterday digging into my wiring harnesses looking for a set of nine wires that would be connected to this ten-pin connector.  The first wire, and the easiest to identify, is the gray one that turns the power steering unit on.  Whenever I thought I had found it, I hooked up a voltmeter, flipped on my ignition switch, and toggled the cruise control on and off using the controls on the stalk.  After about three hours of looking, I gave it up last night.

With a fresh mind on my afternoon off today, I spent some time looking at a harness that goes back behind the engine, thinking it might be buried back there.  It was a painful process and I scratched up my arm on some sharp edges, but I didn’t find it.  Not all pain is gain!

Cruise Control Module

The Suburban’s original cruise control module was reinstalled.

I decided to start at the steering column and trace where these wires wend.  I could tell that the bundle was passing through the firewall on the vehicle’s left side by the convenience center.  I looked at the bundles on the outside of the firewall, identifying where each one went, knowing that I had missed something.  When looking at a few bundles going under the fuse/relay center, I found one that didn’t seem to be attached.  I pulled on it and found myself staring at the connector I thought I’d cut off!

So, I reinstalled the Suburban’s original electronic cruise control module on the firewall.  I chose to see if the original cable could be modified to work with the 4BD1T, rather than trying to build an entirely new one.  Recalling some aftermarket cruise control installations I’ve done in the past, I picked up some pull chain components from Rural King.  I also salvaged a part that attaches a pull chain to a bolt that

Pull-Chain and Cable Stops

Pull-Chain and cable stops were used to connect the cruise control linkage to the throttle. Note the angle-aluminum bracket used to hold the sleeve.

was still attached to the lower side of the bellcrank in the throttle linkage.  By flattening one side of a coupler and drilling a small hole in it, I was able to slip it over the stock cable and keep it from sliding off with a cable stop.  I used the bolt-to-chain coupler on the other end, using the cable stop that grabs the throttle linkage cable.  The pull-chain is a great idea, as it ensures that the cruise control system can only pull on the throttle lever, and cannot keep the driver from applying throttle when needed.

I also cut a piece of angle aluminum and made a square (12mm x 12mm) hole in it so that the cable sheath could snap in place.  When I got this together, I checked to see that the pull chain wasn’t long enough to droop and touch the glow plug rail.  I’d hate to have a short here!

This morning, when I was still at work I realized that I really needed to add a switch to this system.  Because the Suburban was originally equipped with an automatic transmission, I needed a switch that would sense when the clutch was being used and cancel the cruise control.  The brake pedal has two inputs to the cruise control system.  One is normally open, and the other is normally closed.  Either one will cancel when switched from the normal condition.  The normally closed one is what got my attention.  By running this through a second normally-closed switch, either switch will cancel the cruise control.

Clutch Switch

This is a clutch switch that matches the 2000 K2500 pickup clutch assembly I used. It snapped in place perfectly and provided normally-open and normally-closed connections.

My clutch assembly is from a 2000 K2500 pickup, so I looked for an appropriate switch and picked up this odd-looking device on my way home.  The white plastic piece pops off, and this switch snaps onto the clutch pushrod.  The white part snaps back into place to lock it on.  When I got under my dash with it, it was obvious how it would fit and it was a perfect match.  Connections on the end provide normally-open and normally-closed connections.

I spent a fair amount of time looking for the appropriate purple wire under the dash.  When I thought I had it (several times), I used a test light with a needle point that can dig through the wire’s insulation and a ground clip to check.  I was looking for a wire that would give +12V with the ignition on, but would shut off when I touched the brake pedal.  When I found it, I cut the wire, added some extending leads, and put the normally-closed portion of this switch in series with the brake switch.  Now touching either the brake or the clutch will result in an interruption of this signal, canceling the cruise control.

With these components installed, I went for a short test drive.  I got the Suburban above 30 mph, turned the cruise on, and hit the set button.  At first I thought it wasn’t working, but then I started climbing a hill and the vehicle maintained speed.  Clutch use canceled operation, brake use canceled operation, coast and accel/resume functions were working.  Mission accomplished!

-Time for some holiday travels to try it out!

Snow in the Boulder Foothills

The Diesel Suburban covered with snow in the Boulder, CO foothills

This morning the Diesel Suburban was covered with snow — creating an opportunity to check 4×4 functions.

We are still in Colorado on vacation with the Diesel Suburban. The warranty exchange on the steering box fixed the handling issues, and we’ve been driving this up and down the front range.  We took it to Wyoming to visit a friend’s missile silo north of Cheyenne, and topped off the tank on the way back.  Wyoming has lower diesel prices, probably due to lower taxation.  We checked, and found that we were still getting 25 mpg — even with trips to and from Boulder Heights where the elevation changes over 2,000 feet in only 4.5 miles.

It snowed six inches last night, and I took advantage of these conditions to check 4×4 functionality.  I can shift in and out of 4wd with no issues.  Traction is pretty decent in 2wd, too, thanks to a limited-slip differential in the rear.  I can sure tell the difference climbing steep snow-covered roads, though, when 4wd is engaged.  I can’t get into 4 Low, though, and will look at what other signals that system may be looking for.  1st gear in this NV4500 is pretty darn low, anyways, and this will certainly be adequate for the rest of the trip.

Family Trip: Boulder, Colorado

In a move that some might call crazy, I decided to take the diesel Suburban to Colorado. The whole purpose of this machine is to provide economical, comfortable transportation for my family.  So, if I didn’t take the Suburban on this trip, when would I use it?

Our run from Indiana to Colorado was mostly uneventful.  In areas where the speeds were in the 65-70 mph range, we got 25 mpg on the freeway — which is what we expected.  When we got further west and the speed limit popped up to 75 mph, and we were running in the 75-80 mph range, it dropped to 23 mpg.  Still not bad for a heavy, brick-shaped vehicle.

The trip ended in a climb into the foothills outside of Boulder where my parents live.  The 4BD1T pulled the Suburban up the hill just fine.  EGTs rose to around 1000F, which is within the acceptable range.  I’d like more boost and power, and I may do some tweaking while we are on the trip

We found one issue that needed to be corrected as soon as we got to my parents’ house.  The Suburban was wandering all over the road at highway speed due to a steering box that had way too much slop in it.  I had replaced this box for the same reason last weekend, and it felt better through the week.  As we got down the road, the thing loosened and driving became tougher than it should be.  At a (rare) fuel station stop, I had my wife wiggle the wheel while I looked at the output shaft on the box.  It was actually translating right and left within the deadband, rather than turning.

Swapping a steering box in my parent's driveway.

Swapping a steering box in my parent’s driveway, in the foothills outside of Boulder, CO.

So, when we got to my parents’ house, we did some visiting, and then I made my way out to the Suburban to start removing the box.  I had purchased the remanufactured unit from O’Reilly in Indiana with a limited lifetime warranty.  I didn’t have my receipt on the trip, but I gave them my phone number and gave me a fresh unit.  The slop was obvious, even sitting on their countertop.

This morning the box is reinstalled, the alignment was checked, and we’ll make a run to Denver to take the kids to the aquarium.

GT2259 Turbo Upgrade – Part Two

I posted this on 4BTSwaps.com, and thought I should share it here, as well:

I thought I should share some photos of the work in progress. This has taken a lot more time than expected. Isn’t that always the case, though?

First, here’s a side-by-side comparison between the GT2259 and the 4BD1T’s stock (non-wastegated) turbo. The compressor is noticeably larger on the GT2259.

The turbine looks tighter on the GT2259.

I wound up pulling the exhaust manifold and trial-fitting the turbo on the bench. I thought I might have to do some trimming, but my homemade adaptor gave me enough standoff that it wasn’t necessary. The left side in these photos is up when mounted on the engine. I didn’t like having the wastegate hose that close to the manifold, or having vent/drain hole on the wastegate valve pointing upwards, so I flipped this assembly.

Here’s the manifold back on the engine with the adapter installed. This is simply a pair of Ebay T3 Flanges welded back-to-back at 90 degrees, with some grinding to blend the edges.

Here’s the intercooler I’ve hung behind the bumper, below the radiator. It’s an MR2 style, small in frontal area, but 4″ deep. I’m working on cutting a hole in the bumper to get air to it. I’m also going to add a duct to ensure air goes through the intercooler, rather than around it.

After the hours I put into it on Monday, I thought I’d be done, but I’ve still got to at least cut the bumper hole and run my intercooler pipes before I can drive it. Perhaps tomorrow night I can get it together.

GT2259 Turbo Update

Time for a quick update on the new turbo I’m installing.  First, though, a couple gratuitous photos of this nice-looking machine and the current 4BD1T installation.

4BD1T Installation

The Isuzu 4BD1T installed in my Suburban.

Nice looking Suburban

Nice looking Suburban, if I say so myself!

Because this Hino version of the GT2259 has a T3 flange that’s rotated 90 degrees, I picked up a pair of T3 flanges from Ebay to make an adapter. Tonight I spent some time grinding away material from both of them so that there will be a smoother transition from one rectangle-shaped opening to the other. I’ll get a local guy to weld these together for me.

Makeshift adapter

The flanges have been ground to help smooth the airflow.  When these are welded together, I’ll have a makeshift adapter to deal with the Hino’s unusual T3 flange angle.

The turbo arrived, recently. It took longer than the Ebay estimate, and I saw that it was actually shipped directly to me from Taiwan. I don’t have a problem with buying stuff from overseas, but it would be better if the seller were up-front about it. It does appear to be a genuine Garrett turbo, though.

Genuine Garrett GT2259

This is a Genuine Garrett GT2259 from a Hino truck

I took some time this past weekend to reclock the unit, as the oil drain flange was at the wrong angle for how this will be mounted on my 4BD1T.

As I took this nice, clean remanufactured unit apart to re-clock it, I took some snapshots and measurements. As a wastegated GT2259, I expected a turbine aspect ratio of 0.67, but was pleasantly surprised to see that this (Hino application-specific?) housing has an aspect ratio of 0.47. This should make for a nice, early spool! The wastegate should help me avoid too much backpressure as engine rpms increase.

Turbine housing markings

The turbine housing markings indicate a 0.47 aspect ratio — good for spooling at low rpm.

Turbine impeller

While the turbine impeller was exposed, I took measurements, confirming that this turbo matches Garrett’s GT2259 specs.

The turbine specs are:

Inducer: 50.3 mm (confirmed)
Exducer: 43.2 mm (confirmed)
A/R: 0.47 (stamped on turbine housing)

There were no surprises with the compressor side.

Inducer: 42 mm (confirmed)
Exducer: 59.4 mm (confirmed)
A/R: 0.61 (stamped on compressor housing)

Compressor rotor

I also measured the compressor rotor, while it was exposed.

Because the compressor outlet came with just a flange on it, I picked up a coupler and installed it.

Reassembled, clocked turbo

After the turbo was reassembled and clocked a coupler was added so that a hose can be attached later.

The actuator on this turbo seems to be very tightly sprung and lacks any adjustment feature. I may wind up swapping this component for one that I can tweak. I need to find out if the Garrett actuators are somewhat universal.

That’s all for now.  I’ll post more as things progress.

–Putting the “engine” back in engineering!

Performance Upgrades: Turbo and Rear Bushings

A few weeks ago we took the Suburban to see family in Ohio. The highway mileage was pretty good at 25 mpg, but this trip highlighted two shortcomings for the vehicle’s current setup.

Garrett GT2259

The Garrett GT2259 has an ideal compressor map for a 3.9 liter diesel in the rpm range I’m using.

First, the Suburban had plenty of power at speed, but short uphill highway ramps made me uncomfortable. I especially don’t like the rather large step from 3rd to 4th gear in these situations. After the engine has been wound up to the point of diminishing returns, I make that 3-4 shift and find myself at some rpms that are too low for the turbo to produce much boost. The vehicle is accelerating, but s-l-o-w-l-y. The stock, non-wastegated Garret that came with this late-80s Isuzu 4BD1T is designed so that it never needs a wastegate. It never spools up enough to produce “too much” boost (so, it’s weak by definition!). It has a roomy case on the turbine, too, so that by the time it reaches the max boost of 12psi, it is at a point where the driver will be reaching for the next gear.

I’ve been staring at turbo compressor maps for awhile, and I’ve settled on a Garrett GT2259.  I fed Garrett’s Boost Advisor some information about my engine’s displacement and this turbo was the best recommendation it made.  I told it some things about my engine’s displacement, intercooler assumptions, my “mid-range” and “max” rpms, and my target of 200 hp.  If I reach my targets, this turbo will put out 22 psi, putting the pressure ratio at 2.6 on the map shown here.  The corrected air flow will vary with rpm from 17-22 lb/min — which puts it right in the upper-middle part of the map.  Some of the other recommendations I’ve heard for this engine (including others made by Boost Advisor and some on 4BTSwaps who recommend the Holset HE341) would put these points off the left side of the map, on the wrong side of the “surge” line.  This map is somewhat similar to the HX30 maps, but it’s stretched out to include higher pressure ratios and corrected air flows.  The HX30 is known to provide 20+ psi on these engines as low as 1500 rpm, but flow will choke at around 2500 rpm and the turbo won’t deliver any more air.  I think the GT2259 is a better match than the HX30 for onroad use, and I’ve found a wastegated, water-cooled, remanufactured turbo on Ebay that’s meant for use on a Hino truck.  When it arrives, I’ll start my next step in the diesel portion of this project.

The second shortfall with the Suburban was its handling.  I’ve driven a number of large vehicles over the years, including Special Transit buses in Boulder, CO during my college days.  I know better than to expect sports car handling in something as hefty as a Suburban, but it shouldn’t handle like a fish, either.  At low speeds the vehicle is fine.  At highway speeds, the vehicle slops around with the rearend moving left and right without immediately changing the direction of the vehicle.  It forces the driver to think further ahead and make more predictive corrections to keep the vehicle straight.  In a crosswind, or when passing semis, these behaviors make me uncomfortable.  I want this thing to be drivable by my wife, too, so that we can switch off on long trips, so the handling needs to be fixed.  I intend to fix the handling and do the turbo upgrade before our trip to Colorado this autumn.

With my initial build, I replaced the rusted-out shocks on the vehicle with some upgraded, larger-diameter units — so at least I knew that the axles wouldn’t be hopping around as I go down the road.  I suspected that with 152,000 miles on the odometer, the original rubber bushings might be worn out, but I thought I’d see how it handled, first.  Now that I knew the answer, I ordered a stack of polyurethane bushings online and started installing them this weekend.  I got the rear end done and got started on the front end.  I was hoping to do the whole thing, but I ran into some things that slowed my progress.  I’ll cover the front end in another posting.

In advance, I’ll apologize for the photos in this post.  My old camera died and I wanted to take better pictures than my camera phone will allows.  I also don’t want to expose my family’s “good” camera to the metal chips and other conditions that probably killed the last one.  So, I bought a waterproof Vivitar, thinking that being waterproof would also keep metal chips out.  I should have paid more attention to the reviews of photo quality, and this one is going back to Amazon!  It took multiple pictures of any scene and external lighting to get any useful pictures out of this thing.  I should have just used my Android to take these, as it provides better quality with less fuss.  When a phone takes better pictures, money has obviously been wasted on the purpose-built camera!

Rear axle unbolted from leaf springs

After the vehicle was properly supported, the rear axle was unbolted from the leaf springs and set onto smaller jackstands.

First, I put my floor jack under the Suburban’s rear differential and supported the vehicle’s weight while I loosened the lug nuts.  Then, I lifted the whole rear end as high as the jack would allow.  I put my larger jackstands under the rear frame, and slowly set the vehicle down onto them.  I removed the rear sway bar and end links, so that they’d be out of the way and could also receive some upgrades while they were off.

I removed the rear wheels and thought about the forces on the bushings from the weight of the hanging axle.  I realized that I would actually have to remove the springs to use my press, so I pulled the U-bolts that attach the rear axle to the springs on both sides.  I supported the axle with the jack and settled it onto a small jackstand on each side.  I didn’t want to mess with the brake lines, so I just let the rear axle sit on the stands during this work.

I did both sides, but please note that all photographs and discussion here are on the right-side assembly, in order to avoid any confusion.  Please also note that I recommend doing one side at a time on almost any component disassembly and reassembly efforts — because you can always consult the properly assembled components on the other side to avoid errors.

Cutting leaf spring bolts

Because the bushing sleeves had rusted onto the bolts in a few places, some of these grade 10.9 bolts needed to be cut.

I unbolted the front pivot and the point where the shackle meets the frame at the rear.  For the shackle, I was able to use a tie-rod tool to push the bolt out.  On the front pivot, I couldn’t fit the tie-rod tool, and smacking the bolt with a hammer / 2×4 combination wasn’t budging it.  When I rotated it, I found that the bushing’s inner sleeve was rotating with the bolt, so I knew I had a problem that I’d seen when doing a suspension lift on a Cherokee a couple years earlier.  These bolts pass through a sleeve that goes through the bushing’s ID.  There’s apparently never any grease on these bolts, so after a few years the bolts freeze to the sleeves — making them nearly impossible to remove.  I borrowed a friend’s reciprocating saw and wound up cutting this bolt (I had to cut two of them on the vehicle’s left side, as well).  These grade 10.9 bolts are pretty hard to cut and will dull a bi-metal steel-cutting blade very quickly.  So, I used a flat blade with carbide grit attached to it.  These are usually sold for cutting tiles and cast iron.  I learned this trick on the previously-mentioned Cherokee effort.  It takes awhile to cut through, but it works!

Using a hydraulic press to remove old bushings

Using a hydraulic press to remove old bushings.

After that, I pulled out my super-fabulous Harbor Freight hydraulic press and pushed out the old sleeves and bushings.  This sounds simple, but these leaf springs are heavy.  In the picture, you don’t see that the other end of the spring is supported by a wooden sawhorse.  I started off using a plastic, folding sawhorse, but the weight was too much for it, and I didn’t want to drop the spring on the concrete again.  That’s not the kind of excitement I’m looking for!  I had to use a combination of spacers, plates, sockets, and socket extensions to get these out.  I unbolted the shackle from the rear of the spring and used the same technique.  If I did it again, I’d apply some heat with a torch ahead of pressing–as this technique gets the rubber to unbond from the steel shells and has been very helpful on the front end!

After I got the bushings out, I used the reciprocating saw to make cuts in the shells so that they could be removed.  The polyurethane bushings are designed to be used without shells, in this case.  It’s important to be very careful on how deep these cuts are.  I nicked the spring steel in a few places, but I used a rotary tool to smooth/round out the resulting grooves–in order to avoid the progression of stress cracks at these points.

Inserting polyurethane bushings

Inserting polyurethane bushings — mostly by hand.

With the shells removed, I cleaned up the springs, wire-brushed areas with corrosion (especially inside the eyes), and hit all the external areas with rust convertor followed by some black spray paint.  When the paint was dry, I greased up my bushings and squeezed them into the spring eyes.  They are a tight fit, but I could insert them most of the way by hand.  I used a clamp to ensure they were bottomed out.  Next, I started the sleeves by hand, but had to use a C-clamp to get them fully inserted.

For the shackles, I realized my kit contained 1 3/8″ shackle bushings, rather than the 1 1/2″ ones I’d need.  Rather than wait another week to get this job done, I chose to go with the OEM style rubber bushings from Napa.  These included shells and took more force to insert.

I then bolted the shackle onto the rear side of the spring, after consulting the components on the other side of the Suburban to see (1) which side of the leaf spring was forward, which wasn’t immediately obvious, and (2) which way the shackle should point.

These leaf springs have plastic parts between the ends of the springs where they meet, and I can see that these parts rub on each other as the springs are loaded and relaxed.  I put a coating of Boeshield on these areas, thinking that the waxy/oily substance may provide a bit of lubrication and help inhibit further rusting of the components (I spray this stuff all over the place under the Suburban to prevent rust, and it also makes a good chain wax for bicycles).

Reinstalling leaf springs

Reinstalling leaf springs. After the front eye bolt and the shackle bolts were all inserted, it was time to torque everything down.

I then carried the heavy spring assembly back to the Suburban and put it in place.  I set it on top of the axle perch, being careful not to crush the brake lines nearby.  I bolted the front eye in first, using grade 10.9 M14 x 120mm bolts with a 2.0 thread pitch.  Unhappy with a purchase from an online GM seller that still hasn’t arrived (after over a week), I sourced these from Utterback Supply in Indianapolis (I really like doing business with these guys, and would link to them if they had a site!).  I didn’t torque them down right away, because it’s best to get all of the bolts in, first.  I bolted up the shackle in the rear, then I torqued everything down.  I also noticed that I’d forgotten to apply rust convertor and black paint to this shackle mount, and did that next.

At that point, I jacked up the axle on that side, aligning the hole in the perch with the bolt on the bottom of the spring, and reinstalled the U-bolts.  After double-checking my torques, I was done with that side.

While I was replacing bushings, I also chose to replace the rear sway bar bushings with polyurethane units.  I won’t go into much detail on this, but the kit included right and left sway bar bushings with new brackets and grease fittings.  The end links also got new polyurethane bushings.  I spent a lot more time on the leaf spring bushings, but this upgrade probably makes more of a difference in keeping the Suburban’s rear end well-behaved.  I’ve found that polyurethane sway bar bushings and end links will do a lot to flatten a car’s attitude in a corner.  Stock rubber bushings are often too soft in this location.  Much of the process in replacing the Suburban’s bushings was just a do-it-once maintenance activity.  The rear sway bar was bolted in after everything else was reinstalled and was the last step before setting the vehicle back on its tires.

Rear sway bar

The rear sway bar also received polyurethane bushing upgrades.

I should point out that I used marine bearing grease on all of the polyurethane bushings.  This is a bluish-green silicone-based grease that won’t wash off and won’t react with the polyurethane.  I’ve used it in a number of applications and it does a good job in keeping the squeaks at bay.

–Just because a vehicle is large and heavy, doesn’t mean it has to handle dangerously!

Tachometer Wiring

On the Diesel Suburban project, I should provide a couple updates and show how I got the tachometer working.

Since the diesel was installed, I haven’t driven the vehicle too much. I drove it to work for a few days to show off and check my mileage. I topped off the tank before the first day, drove it three days, topped it off again, and did the math. The verdict was that I was getting 22 mpg — which isn’t bad for mixed driving (EPA and Fuelly both show 1999 Suburbans as getting around 14 mpg in mixed driving).  We live southwest of Indianapolis and visited some family north of Dayton, OH a couple weekends ago.  I purposely topped it off before we hit the highway and checked the mileage when we were close to our destination.  Highway mileage was 25 mpg — which, again, isn’t bad for punching a hole through the air at 70-75 mph with a large brick-shaped object.  17 mpg is what would be expected with the 5.7 liter V-8.

Driveability isn’t bad, unless you really need to accelerate — such as on a short, uphill highway ramp.  The engine is still stock, other than backing out the power screw slightly.  The stock Garrett turbo is the version without a wastegate, and is purposely designed so that it’ll never spool up enough that one is needed.  Under normal driving conditions, I might see 5 psi on the boost gauge and 12 psi if I’m trying for maximum acceleration and wind up the engine to about 3,000 rpm.  In 5th gear at 70 mph, this engine is only turning 1900 rpm.  I need more boost and torque available in the mid-range rpms, so I’ve ordered an upgraded turbo.  I’ll cover that in more detail when I begin installing it.

I knew what my rpms would be at any given speed by doing some math, knowing my tire diameter, rear end gear ratio, and the ratio of the gear I’m in.  It’s a pretty simple calculation, at least once the unit conversions are straight.  In order to know what conditions I was exposing the engine to, I had already installed boost and pyro gauges.  I wasn’t able to actively monitor my rpms, though, until I installed a Dakota Digital DSL-1.

Because diesel engines don’t have a coil to provide an ignition signal for the tachometer to measure, we are forced to find other ways to get a signal that’s proportional to engine rpm.  One way to get a signal would be to use the “P” connection on the 140-amp (CS144) alternator’s “SFLP” plug.  The “P” connection sees the oscillations of a single stator and provides a signal that can be used.  The DSL-1 is essentially a frequency convertor that takes a signal at one frequency and either multiplies or divides that signal’s frequency by the right ratio to emulate a V-8 signal.

Sensor That Reads Pump Gear Teeth

The sensor with the blue goop on it to the left of the timing opening was to be used to drive the tachometer

I considered using the alternator’s connector, but thought it would be slick to use the sensor that was already on the 4BD1T.  This sensor is on the engine’s right side, mounted on the case in a position where it can measure the passing of injection pump gear teeth.  It is positioned just aft of the injection timing access cover.  I’m showing an old photo here, because I’ve mounted the air conditioning compressor over these items (it can be unbolted and moved out of the way when needed).  I’m not sure how the NPR truck used this sensor (for a tach, perhaps?), but I was determined to use it for my tachometer.

When I was removing the 5.7 V-8 from the Suburban, I carefully marked a number of wires that I thought would come in handy later for the few engine sensors this diesel would have.  I’ve previously discussed how I used the stock sensors from the V-8 to drive the temperature and oil pressure gauges in the Suburban.

Connector to Drive the Tach

This is the ignition connector that originally drove the Suburban’s tach.

It’s always best to use things in a way that’s consistent with their original design–even if you are altering a machine’s purpose to fit your will!  So, while I was taking the engine out, I was consulting a combination of Mitchell 1’s wiring diagrams and Rock Auto’s connector photos.  The white wire in this connector was believed to drive the tach.  (Sorry about the photo quality, my camera died and I took this one with my phone’s cheesy camera.)

Before I ran any wires through the firewall or did anything permanent, I tried this system out by running some jumper wires around in the engine compartment and hooking up the DSL-1 right there, feeding the device’s output to the ignition connector.

The connections required to make the DSL-1 work are relatively simple.  Naturally, the device requires power, so I fed it +12V and ground.  The sensor I was using had two wires, and I didn’t know which one should be “ground,” so I tried it both ways.  The DSL-1 saw and converted the signal both ways, so polarity wasn’t an issue.

I played with a number of modes on the DSL-1, trying to get the right frequency conversion to get the tach fairly close.  The flywheel tooth sensor mode was designed for flywheels that typically have over 100 teeth, so the tach would read way too low, even on the highest setting (this sensor will see 25 teeth for every revolution of the engine).  I changed the device over to the alternator mode, and quickly found that the output was way too high, even on the lowest setting.  I was thinking that if I could knock off a factor of two, everything would be OK.  Staring at the manual, I noticed that in addition to the 8-cylinder output I was using there was a 4-cylinder output.  Eureka!  I moved the output to the 4-cylinder output, and found that the tach was in the right range for how fast the engine was idling.

The Tachometer Input is Identified Behind the Instrument Cluster

The Tachometer Input is Identified Behind the Instrument Cluster

Then, I took all the jumpers off and started to install the DSL-1 for real.  It isn’t a sealed unit, or something that’s ruggedized for the under-hood environment.  It needs to be mounted inside the cab–preferably within reach of the driver.  After pulling the dash bezel and removing the instrument cluster, I found a “shelf” just below the instrument cluster that would be a good place to attach the DSL-1.  I marked that location.  I took a close look at the connector behind the instrument cluster and unsnapped it from where it is held down.  I found two white wires, so I did a continuity check and identified the correct wire.  I then cut it and ran the DSL-1’s 4-cylinder output to it.  After identifying a good ground and switched power wire from nearby cables, I used them to power the device.  I also ran two wires from the gear tooth sensor to this location and finished wiring the DSL-1.

DSL-1 Mounted Below Instrument Cluster

The DSL-1 was mounted below the instrument cluster.

I pulled out my spreadsheet for rpms at speed in the different gears, and saw that the engine should be turning 2000 rpm at 55 mph.  So, I took the Suburban for a drive without reinstalling the dash beze. I was able to use the UP and DOWN buttons on the DSL-1 to tune the tach.  I held my speed 55 mph, adjusting it to read 2000 rpm.  The speedometer’s accuracy had previously been confirmed using GPS — so I knew it would be accurate.

That all sounds really easy, doesn’t it?  Running the wires was painful, and I always get claustrophobic when working under the dash in a hot environment, but I’m quite happy with how this works!

–Putting the “engine” back in engineering!

Diesel Suburban MPG: not what I was hoping for

I drove the Diesel Suburban to work for the past few days to find out what fuel economy it gets. I also showed it off to perhaps a dozen coworkers and received many compliments on the installation.  A couple guys said it looked like it came that way from the factory, which was high praise!  Another guy said the installation looked better than the factory V-8 did.  The real question about the impressions at work: Am I famous for doing this conversion or notorious?!  I don’t really care, but it would be interesting to know…

Back to the subject of fuel economy: I topped it off on Sunday, reset the trip odometer, and topped it off again this morning.  The verdict: 22 mpg.

Certainly, as my coworkers pointed out, I’m hauling around a 6,000 lb machine with the aerodynamics of a brick.  I was also in stop-and-go traffic for a good chunk of it every day.  22 mpg combined really isn’t a bad figure.

This is a huge improvement over the stock 1999 K1500 Suburban.  Fuelly says people are only getting 14 mpg for real-world fuel economy, which matches the EPA combined rating.

This is not bad, but I know I can do better.  I’ll play with the direct-injection timing and check my valve clearances, but I expect that the real answer will be a better turbo and the addition of an intercooler.  Driving this around I’ve found out why people don’t like the stock turbo that came with the Isuzu 4BD1T.  This is not a high-rpm engine, but the turbo doesn’t spool much at low rpms — so it’s horribly mismatched.  I normally see perhaps 5 psi of boost, and haven’t seen it go above 12 psi.  12 psi is done at some high rpms for this engine, but I can’t tell you exactly what rpms because the tach isn’t set up yet.

I know there are solutions out there.  People talk about turbos that can reach 15 psi across the drivable rpm range.

Why am I talking about turbos, when I’m trying to fix a fuel economy issue?

Sounds crazy, doesn’t it?  Because I backed out the “power” (fuel-limit) screw 1 turn to get slightly better acceleration, I now produce some visibly sooty exhaust.  It isn’t the extreme cloud some of the diesel (mis-)tuners produce, but I can pick it out in the right mirror when I adjust it to view the right-rear corner where the exhaust exits.  This indicates unburned fuel, which can be corrected by adding more air.  I’ll go do my research and provide updates on what turbo/intercooler combination I use and post on the progress of installing them.  There are some family projects that require some attention right now, so it will take awhile.  I’ll keep blogging to provide details of the work I’ve already done, while covering some philisophical and self-reliance topics meanwhile.

–The quest for a 30 mpg Suburban continues!

So Close! Alternator Upgrade

I’ve been putting many hours into this project, lately. Because the Suburban looks like a Suburban, now, and because I’ve driven it.  I feel the need to get this thing into a condition where it’s practical for family use.

At the moment, I’m still messing around with a number of things.

I’m not happy with the brakes, even though I’ve got a good vacuum system in place. Under normal use they are OK. Hard braking, however, shows that things get mushy and fade fast. I think that the vacuum assist is OK, but I haven’t bled the system, yet. I’ll try that, and see whether that’s the issue.

I’ve got some clunks I’m sorting out, but these are getting cleared up. I’ve shifted the exhaust and intake a bit, but those self-tapping screws that I used to attach the shifter boot are a little too long. I might just pull them out and trim off the drill points.

Instrumentation for performance tuning

The pyrometer and boost gauges are necessary safety items, as I will be playing with the max fuel screw soon.

It’s a little anemic on acceleration, but I’ve instrumented the system to monitor EGTs and boost and will be tweaking the max fuel screw shortly (after I fix the brakes!).

This post’s main issue: Alternator Upgrade. One issue that I found last weekend, while charging the air conditioning, was that I was actually discharging the battery. This was caused by a number of factors, including:

  1. The engine’s idle was extremely low — much lower than a gasoline engine would ever be
  2. I was using a CS 130 alternator that came with the Suburban, but had maintained the Isuzu’s large 3 1/4″ diameter dual-belt pulley
  3. I had front and rear air conditioning units running full blast — a considerable load on the system
  4. Running the air conditioning triggers both 16″ fans in the radiator — another considerable load on the system
CS-130 alternator with a big pulley

Thanks to being a relatively small alternator with a big pulley, this CS-130 wasn’t keeping up with power demands at idle.

So, after messing around with things that afternoon, I found out that I had drawn the battery down to 9 volts, and couldn’t even start the engine.  I put the battery maintainer on it and did some calculations.  I don’t think the engine was idling at the normal 800 rpm (though I haven’t hooked up the alternator, just yet), but I did my calculations based on that rpm.  The engine pulley is 6 1/2″ and the alternator pulley is 3 1/4″.  So, at 800 engine rpm, the alternator would be spinning at only 1600 rpm.  The alternator curves I found online showed that these alternators don’t produce any current below 1200 rpm.  They also indicated that this CS 130 (a 100 amp alternator) would only produce around 35 amps at this speed.

It was time to look at another solution.  I looked at some overpriced 160 and 200 amp alternators and found some “overdrive” pulleys that were smaller and would increase the alternator rpm.  I decided to go with a remanufactured GM CS 144 alternator from Napa rated at 140 amps, combining it with a 2.6″ diameter pulley from Great Water.  In this case, an engine turning at 800 rpm would turn the alternator at 2000 rpm.  At this rpm, the CS 144 curves I found showed that this would produce a remarkable 90 amps at idle.

Alternator data sheet

This remanufactured alternator had produced 145 amps in testing — 87 of them available at 2000 rpm.

When I brought the unit home from Napa, I found out that the factory had tested the alternator after rebuilding it, and provided a data sheet showing the results.  They showed that this alternator had produced maximum of 145 amps at 6000 rpm, with 87 amps available at 2000 rpm.

CS 130 and CS 144 alternators

A size comparison between the CS 130 and CS 144 alternators.

I pulled the serpentine pulley from the larger alternator and put the Great Water pulley on it.  17mm shafts are standard on these, so there were no fit issues.  Here’s a comparison of the two alternators side-by-side — showing how much larger the CS 144 is.  The 144 is known for durability and reliability.  Though 130s can be wound for high output, the 144 will still typically provide more current at lower rpms.  CS means “charging system,” while the numbers indicate the armature size.  Note that even with the case size differences the mounting ears are in the same places–allowing many GM owners the ability to upgrade to a larger alternator.  My homemade angle-iron brackets required some modification to fit the larger case, but it didn’t take too long for me to get it mounted.

Mounted CS-144

The CS-144 was mounted, along with a smaller 2.6″ pulley. Testing of this alternator showed that it should produce 87 amps at idle.

Once I did, I was pleased to see that I could run front and rear a/c units on full blast and both of my 16″ radiator fans, while the voltmeter in the dash continued to read 14v.

–Putting the “engine” back in “engineering!”

Bringing the Suburban Up to Speed

The diesel Suburban has received a lot of attention over the past few days, because I’m determined to drive it to work this coming week. Everybody there has heard me go on and on about this, but they still want to see it! I haven’t been posting much, as I push through and achieve this milestone. Today my son and I took care of a few more things that needed to be done and took the Suburban for a ride into town. This is the first time that this “diesel” project actually entailed buying a substantial amount of diesel fuel. This thing has a 40 gallon tank — so if I get good fuel economy with it, the range will be truly remarkable.

Here’s some video from that ride (camera work by my son).

When we got back, we talked to a nice neighbor who helped us install the hood. The vehicle actually looks like a Suburban, again.

The next steps are to get the a/c working, wash the dusty machine (it’s been in my workshop for 15 months, so it has an excuse), and do a little performance tuning. The exhaust was never visible in today’s drive, so it’s time to play with the power screw.

-Putting the “engine” back in engineering.