David Lane On Adding a Turbocharger

Date:	Thu, 7 Jan 1999 18:52:13 +0000
From:	"David Lane" <dlane@peabody.jhu.edu>
To:	"sherry vazirani" <fiero_85@hotmail.com>
CC:	mrmazda@gate.net

Sherry,

Felix Miata forwarded your request to me because I have had a Turbo-ized GSL-SE since 1987. I will do my best to answer your questions.

> I'm thinking about selling my '86 RX-7 NA, for an '85
> GSL-SE, and modifying it to an '86 13b, and then I would
> like to throw a turbo on it.

There have been aftermarket turbo kits for both models. CarTech made them, but they are no longer available from there. Redline Performance in California now has the rights to produce the kits, but they specialize in off-road turbo rotary machinery, so I do not know how far they have come along in developing a marketable kit for either car. Last I heard, they still considered it a low priority.

If you want to bolt a turbo onto either car there are pluses and minuses. The GSL-SE engine is actually a little stronger internally. It's apex seals are 3mm thick vs. 2mm for the '86 engine. This gives you marginally more protection from detonation. Thus, I don't think you would gain much by transplanting an '86 engine into the GSL-SE. The only exception would be that the '86 engine had four fuel injectors which can supply more fuel than the two (albeit larger) injectors in the '85. In either case, adequate fuel supply will be a key issue in the success of the turbo modifications.

On the other hand, putting a Turbo II engine into a 2nd gen has to be much easier than for the GSL-SE, and the 2nd gen chassis can more easily accept and handle the added power.

The only reason to stay with the GSL-SE is if you happen to be addicted to the way they look, or (as in my case) if you already have one, and have access to one of the earlier kits.

> Do you have any idea on what year of turbo I should put
> on it? Do you know of anyone who has done this? (If so,
> could you please give me their email address?) If I were to
> accomplish this project properly, would it be faster than
> lets say a '91 turbo RX-7? How about a '93 twin turbo?
> (probably not, I know)

I am not sure how difficult it is to shoehorn a T2 engine onto a GSL- SE. Certainly it will entail much custom (expensive) work. I know of no one who has transplanted a 3rd gen engine into a 1st gen. The problem with both situations is that not only must you deal with mechanical aspects, you must also deal with the electronic controls. Either you use the associated engine management system from the original car, or you must use an aftermarket set- up from Haltech, Motec, or Electromotive. All of these three are costly, and require customized instructions for your car.

> And, one more thing - do you know approximately how much
> I should save up before starting this project?

That is a VERY difficult question. With a GSL-SE you will have to start with a fresh engine, and a Mazda rebuilt engine will NOT have the strength to handle turbo boost. You could send the car to Tripoint in Canoga Park, CA, and they would charge you seven to ten thousand dollars to do the job right. If this doesn't give you a heart attack you can save a lot of money initially by doing it yourself--but only if you can fabricate the parts you need and only if you do not blow an engine while you are working toward the proper fuel/air mixtures. Any mistake will cost about $3,000 for a proper engine rebuild (including removal and installation).

My general recommendation for anyone wanting a fast 1st or 2nd gen RX-7 is to find a T2 (of any year) in good condition. Here's why:

  1. In stock form, that car will do 0-60 in 6.6 seconds. The cost of modifications to make it faster are very small compared to starting with an 8.5 second car. Get it down to the low fives and it will be as fast as the better turbo kits were for the GSL-SE or the non-turbo 2-gens. Look up the FC3S Turbo Performance web site for many examples and suggestions.
  2. The drive train is stronger for the T2s than any 1st or 2nd gen, so it will last longer.
  3. You will not have to spend money for upgraded wheels and tires to get the power to the ground.
  4. The limited slip differential on a T2 is much stronger than a GSL-SE's. If your GSL-SE's differential is not it top shape you will end up trying to deliver 260 bhp to the ground with only one tire.
  5. The T2 engine is already optimized for the turbo--with low compression rotors, etc.. This will make tuning a bit less critical, although for a daily driver there is something to be said for using lower boost with higher compression rotors.

I am giving you this information in a general sense because you did not go into a lot of detail about what you were looking for and why you wanted to put the turbo on a GSL-SE. It made sense to think about it in 1985. The car was new, the kits were available and there were a number of companies producing competing products-- not unlike the situation with the 3rd gens today.

Remember, you are looking to double the horsepower on a car that is already 14 years old. Imagine it is 2012 and someone comes to you saying s/he has a 1998 Miata and wants to put a turbo on it. No one makes any of the old kits any more, and you know that any 14 year old engine has to be a bit tired to begin with. At best it won't be easy. At worst it will be next to impossible, or at least far more expensive than practical for such an old car.

If you wish to discuss it further, feel free to email me directly with any questions and I will help you as best I can.

Best wishes,

David Lane <dlane@peabody.jhu.edu>
'85 GSL-SE (CarTech turbo)


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