63mpg in a 1986 Isuzu Trooper Turbo Diesel
 

I recently finsihed a project on my old 1986 Isuzu Trooper TD. It was a 2.3l Turbo diesel, hd no power to speak of compared to a gas motor Trooper, but averaged 28mpg in town, and 35 on the hiway. Great truck, excellent off road...better than most. BTW, did I mention it was 4x4?

I began my quest to simply gain more power in the mid range, and top end because the truck was such a PIA to tow even a little pop up with. When I tried to tow my 2000lb camper trailer to the lake once, it popped a fuel pump relay fuse! I did all the standard non computer diesel mods if any one is interested I can devilge my mods, but it went from having to literally have it floored on my way up my mountain road for the last 5 miles, to being at 3/4 throttle up that stretch. And from the traffic leaving me at the stop lights in town, to me leaving them....easily!

My hp gains were from a stock at my altitude (7500ft) of 104rwhp, to 154rwhp. And I didn't add a single peice of equipment except a simple turbo boost adjustment valve and a boost gauge and exhaust temp gauge to monitor what was going on and be able to adjust boost to suit conditions. I was able to easily tow the 2000lb trailer after that except for the fact it felt unsafe because of the weight.

I went from a max on the hiway of 35 to well over 55mpg and saw up to 63mpg on a long straight stretch when on a trip to California to pick up a motorcycle.

What kind of instrumentation are you using? Did you have a 63mpg tank or a 63mpg instantaneous readout?

I would love to see pictures of this beast. My parents both owned a Trooper from that generation and I know they had the gas version, so I would love to see pictures and methods for increases for the diesel. You could really help people to adjust thier diesels for optimum power and efficeincy!

Something does not add up. You can't just add more air and make more power, you have to add more fuel too, and the stock fueling system will only flow so much.

Careful with this DIY boost mod. Have you looked at the compressor efficiency map for your turbo? With increasing boost you have to carefully watch what you are doing. There's a reason the stock boost limit is where it was set at by the manufacturer. If you push it too much too early, or at too high rpm, you'll grenade your turbo, especially at your altitude.

The 55 mpg on the highway seems high. You should make a fuel log and look at the long term trend.

http://c3.ac-images.myspacecdn.com/i...b1ba2e3efa.jpg

the truck, and my Hybrid (wolf/Aussie) CaseyDog.

http://c1.ac-images.myspacecdn.com/i...e30c066b84.jpg

finished product!


The tyres helped, as in going from 31 10.5 mudders to 31 10.5 AT. Less rolling resistance.

And here's a list of what I performed,

Removed the stop bushing in the low speed primary part of the fuel pump (mechanical, low pressure side) and adjusted the richning on the low pressure side. This helped because it allowed the low side to run the truck a tad llonger before the transition to mid and WOT throttle.

installed the turbo boost adjustment valve, I used the one that allows adjustment in the cab.

Installed a 4in cold air intake system (custom designed and made by me) with only one gentle turn, and a huge conical K&N race filter.

3in exhaust from the header back with a free flow resonator.

With a careful eye on acceleration and boost and exhaust temp it was easy to see over 60mpg on a long stretch os hiway.

All computed by using a auxillary fuel tank I designed with a 3 gallon capacity and a accurate gauge I also designed. I would stop, switch over to the Aux tank, leave the entrance ramp, then drive till I had about 6oz of fuel and take a mileage reading from both GPS and the odo. All this was done on quality diesel from Shell and using Sea Foam additive, and Diesel Clean additive to manufacturers specs.

An Aux tank (3gal) and GPS and a adjusted and certified (by the state police) odometer. Basically after adjusting my odo speedo, I had a buddy who is NMSP take speed reding with both radar and pacing me in his car, and we checked the odo using both an exact 10 mile course and his odo over a 10 mile stretch.

BTW I sold the truck to a guy who is going to veggie it. He lives in Colorado, and I sold it for $3500.00 which is by far over blue book because of the mileage and condition mechanically of the vehicle. BTW not only did it get great mileage, but the TD troopers go for at least 500K is maintained, mine had 90K on it when I sold it.

This is a completely mechanical fuel system and adjustable, mechanically. You have to think in non computer terms here on the entire system, throw that out the window. There are no turbo timers because there is no computer. There is a massive mechanical fuel pump, and a turbo, and waste gate, and a motor. I increased fuel delivery by doing what I stated in the short blurb. Basically, I increased the timing the low speed circuit on the pump lasts so the transition wasn't as much of a lag between the low side and high speed circuit. I also removed a restrictor that disallowed the high speed part of the fuel circuit from giving the injectors max fuel flow. EVErYTHING stock on this truck was limited so the factory didn't have to replace yet more engines than they already did because of a bad original rod bearing design. In fact, my engine got replaced free by the dealer with a brand new factory motor in 1990. I had to do about 3 months of research on the net and asking a handful of people who had this truck or a car with this motor in it to find out what they did to increas hp. Plus, do you know anything about diesels? The first thing to do to build HP is un-restrict the air intake and exhaust. That alone even without touching the fuel delivery...or turbo will garner sometimes 10% increase in HP because of the stifled factory desigins for intake and exhaust noise.

Ill address the fuel mileage comment here. I did not ever say I got 63mpg average, or that I always got it on the freeway, and I also never mentioned my speed. I got a max of 63mpg on the hiway, going an average of about 50mph. Also, something I didn't mention. I got 80+ at slow speeds whilst hunting one weekend. But that was at an average of <10mph. Real world mileage after all mods averaged at least 45mpg. Which is killer siince stock they were supposed to average 28+

Whatever you do to the stock pump (short of swaping a bigger head) the nozzles will only flow so much once they reach max flow. I find it hard to believe stock nozzles could make 50% more power when "tuned" on the stock configuration. And even if the nozzles can flow that much fuel, I have never seen a setup where the stock turbo can safely push enough air to adequately sustain a 50% power increase. The turbo would be really oversized for the stock application if that was the case. When you floor it it must smoke like a freight train and EGT must reach critical levels pretty quickly. If not, well that truck was really an overly engineered machine in its stock form.

What turbo is in there anyway and what pressure are you pushing it at?

My first car was a 1990 VW Golf N/A diesel. I have owned 3 other VW diesels since then. All I ever owned was diesel vehicles. It doesn't mean I know anything, but I think I know a thing or two.