A Few Words On Turbocharging

A lot of people have been asking about turbocharging their non-turbo Isuzu automobile. The questions usually run along the lines of "I have a non-turbo Impulse/Stylus/Sunfire/Storm and I would like to just throw the exhaust manifold and turbine off of a junk yard car onto it and drive faster than spit. Will this work and how much would it cost?".

Well, I'm no expert on turbocharging, in fact March 17th, 1997, my neighbor took me for my first long ride in a turbo vehicle, his newly acquired 280Z (I have test driven a few Turbo Impulses in various states of disrepair). I have, however read a good bit on the topic in both the SA Motorbook texts and in the popular import car publications. I have a reasonable working knowledge of the theories and the equipment involved in turbocharging.

I would like to say first and foremost, turbocharging a vehicle is not as simple as throwing the manifold and turbine onto your engine and driving. There is a lot more involved in this if you plan on having dependible transportation that will last longer than the end of the drive way.

First, the engine you intend to turbocharge must not have a high compression ratio. The traditional compression ratio for a turbo four is 8.5 to 1. (Larry Schreib in the SA Book "Superpower" states that 8 to 1 is the maximum compression ratio for street use, but he discusses carburated V-8s. You can go a little higher with multi-point injection as in the Isuzus.) Most Non-turbo cars have 9 to 1 or higher compression ratios. You can get away with about 9 to 1 but beyond that, and the boost you add with the turbocharger will cause detonation and blow your engine.
Also, the higher the compression ratio, the less boost you can apply to the engine. Otherwise detonation and blown engine.
So you'll be rebuilding the engine with custom pistons or the pistons from the Turbo, to lower the compression ratio, and while you're at it, you'll be strengthining the lower engine to take the additional stress of the turbocharger.

Secondly, the whole computer system has to be changed over to the system from a junk yard donor car. You will need to change the the ECU, the engine wiring harness, all of the engine sensors, all of the solenoids and actuators and additional electronics which control the turbo system. If you don't do this, you'll be lucky if the car doesn't run so that you don't blow the engine and end up wearing most of it's internal components.

So you are basically buying a junked turbo car to strip for the needed components.

Next, the fuel system will have to be converted over. You'll need the higher flow rate injectors from that junked car, the higher pressure fuel pump and sub-pump, and a rising rate fuel pressure regulator.

Without the additional fuel, the engine will run too lean under the forced air charge of the turbo, and will detonate, and blow.

Now you're finally to the point where you can use those manifolds mentioned earlier. You have to convert the entire induction system over. Intake manifold, exhaust manifold, air plenum, waste gate, intake piping, and intercooler, all from the junk yard donor turbo.

Now you're done with the engine, it's time to look at all of the other changes you have to make.

The clutch is the most obvious, the turbo vehicle came with a stronger clutch. You'll burn yours out in short order with the extra power.

The tranny in your non-turbo is most likely not the heavy duty tranny on the turbo model, especially if you have the JR with the three link rear end. You may be replacing gear clusters on an annual basis if you don't swap yours out for a turbo model tranny.

The ring and pinion gears and differential in your non-turbo are most likely not as durable as those in the turbo model. You'll probably do some creative dentistry by removing teeth from all of these parts until you upgrade to the turbo parts.

I might also point out that many of the turbo models have air pumps so that they will pass emission tests.

So it becomes quite obvious that it is no small task to put a turbo onto a non-turbo car. This becomes a major rebuild if you intend to use OEM parts and put it together with the same reliability and durability as Isuzu did on the Turbo models. I many cases, it would be simpler to repair the junked car and lower the compression on your engine to swap into the rebuilt car. This would probably be cheaper too, I can't imagine that putting the turbo and accompanying parts ont your car would cost less than $3,000.

There is another option though. There are several companys who make and install custom turbocharging kits, and are willing to work on any vehicle, even those whose compression ratio is a little too high for the stock system changeover. This will involve lots of custom piping and some electronics that will be piggy-backed onto your ECU and sensors to trick the computer into thinking that your car is opperating within normal parameters. This still doesn't solve the drive train durability issues, but the end product will likely out perform the stock turbo counterpart and additional tuning for more power will be easier, because you are starting out with more flexible equipment which won't need to be upgraded from OEM to work with.

Best of luck with your turbocharging project.

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