PRC GT-L Engine Questions
 

I've got a 97 engine and brain that I've replaced the varioram intake with that of a 95. This is the set up I'll originally put on the track. I know I could do better with a different brain (car) but, for now, I just want to get the car done and learn how to drive it.

I've also got a complete 91 engine. The plan is to rebuild this one with arp rod bolts and cross drill the crank to use as the track car's future engine. The 97 engine will then go into a street car and be used as a backup race engine.

I'd like to land up having both these engines built the same - aside from crank and rods. To do so, I'd have to trade out one set of heads to match the others. That is, if the performance difference would be noticeable.

What would be the preferred set of heads to use - the 97's or the 91's? The gearbox I'm using is a Wevo built close ratio 915.

As far as the brain(s) go, should I be looking for one from a 95?


Thanks-
Craig Backer

Craig,

My understanding is that the limit of the stock intake pretty much limits hp to about 300 at the flywheel and that the rest isn't critical. Mine was built with stronger rods, bearings and valves springs.

What control you use for the engine limits how you program it to get the most out of it. I chose to switch to MoTeC as that's what the folk at Jerry Woods were most experienced with to tune mine to get the most out of it. The '97 requires the box to be sent in to be flashed to program. A '95 allows a simple chip swap. Getting the programming for the flash or chip to match what can be done with a MoTeC is a bigger problem. I know of no one in the bay area that can do the chip or flash. Steve Weiner at Rennsport Systems is a good source. I believe he work with Jeff Gamroth (RothSport) to develop custom maps. You could try him.

Will you have it done for the season opener in March? I'm looking forward to having a few more cars in GTL this year.

Great suggestions/advice from Tom (your future competitor and a heck of a driver). By the way, do you have racing experience already?

Working with Jerry/Rich and Motec is not a bad choice. It is very spendy though. Gamroth favors DTA I think. Another resource you should consider is Mat Lowrance up at Sporthaus in Reno. He is getting cars to go really fast and run up front with a variety of innovative and cost-effective approaches. I am not sure what he'd recommend, but he has certainly given consideration to many of the variables you are considering.

- Mike
Porsche Racing Club #4

I may be weaving my way down to this class in short order and sell my PMO carbs to pay for the last round of repairs. I have a stock intake system from a '92 3.6 sitting on my shelf but would need to get 6 intake manifolds and rubber boots - shouldnt be too hard to find those. Then hook it up to Motec and tune it. I've been searching these forums to see what the absolute minimum of noodles will be required on the intake system and then eliminate/plug the rest. I noticed there's a flapper valve on the lower plenium that will need to be controled at some RPM/load. also, since I'm using motec, I presume I can eliminate the flapper air flow box as well.

Jeff

You don't need a flapper door or a hot wire... Mr. Motec can prolly just go off of throttle position. Partsheaven may have a plastic 3.6 intake maniforld still... I may be able to get a deal on it. But be aware that there are differences between the 964 and 993 versions, and I think the 993 version (what I have) is better. It's really easy to control the flapper door for more mid-range torque at certain rpms.

Also, don't forget GTL spec for header.

This class may grow really quickly in the next couple o' seasons.

- mm

I may have an extra 95 993 intake for sale. It doesn't have the injector blocks, boots, injectors, rails or maf sensor. I may need to use the isv from it so it may need that as well.

Craig Backer

95 993 was Varioram - I *used* to have one of those and sold all the injection parts from it years ago.... :(

At this point, I'm not into spending money, I'm into saving as much of it as possible, so I'm going to have to go w/ what I have which is the aluminum version. It's now all about being able to race at all, and finding someone to race with has never been a problem before... those Toyo Cars are going to be looking pretty fast... :)

Jeff

Varioram started in 96

right. I think I got the engine out of the first wrecked 1996 car that was sold in '95!

Jeff

I'm confused as to what you have. If it is cast aluminum, and is not varioram, is it from a 964? '95 993's had black plastic intakes that were similar to late 964's I think... except I think the flapper door chamber is a lil different.

I know there was one buried in the parts bins at Partsheaven a few months ago as I was "closely examining" it. In any case, it is good to try to use the flapper door, and Mr. Motec may allow you to switch it at selectable rpms. If he cannot do it (Mr. Haltec can't) , then a simple MSD window switch works. That's how mine is set up. I also have a simple magnetic switch fabbed into the throttle linkage so that the window switch only moves the flapper at a selectable throttle position (see pic below). You may be able to do all of that with Mr. Motec... I am not sure.

We will know more about what's possible in GTL once you are in... maybe Neil J. is headed that way, plus Skip, Rich and maybe even Mat. Plus maybe Karl and others from the NW.

Perhap PCA Club Racing should keep an eye on this concept for future classification considerations.

- Mike

http://forums.pelicanparts.com/uploa...1174941352.jpg

Yes, Motec can do all of that plus some. It has a TPS and can control various output switches based on RPM, TPS or combination. It's certainly the way to go and would be pretty easy to set all this up.

And the intake I have sitting on my shelf is a 964 aluminum version, not a 993 version.

Jeff

Here's the way I understand it.

1989 - 1991 1/2 = aluminum intake w/ afm (flapper door aka barn door)
1991 1/2 - 1994 = plastic intake w/ afm
1995 = 1.5mm larger diameter plastic intake w/ maf sensor
1996 - 1998 = varioram

I believe the afm and maf's are interchangeable between the early intakes and the 95's.

There are two types of flapper doors. Generally, the term is used to describe the air flow meter in pre-993 cars and others of their ilk. This to distinguish from later air metering systems which use a hot wire, like the 95 and later 993. That type of door is completely irrelevant here...

The flapper door to which I refer is the one in the intake system itself. This was first used in the 964 cars, and a different version in993's. This was a precursor to varioram. It is the control of that door that I am referring to.

- mm

oops