Carpokes Porsche Forum

Here is one the mist interesting things on the 944GTR.
The wastegate is referenced to the exhaust pressure and not the intake pressure……interesting
No idea why!

Not sure if @Gregbbrd is still around here, but he'd be the guy to know all of the 944 GTR mysteries....

Greg built my trans about 12 years ago. His shop was nearby, he's since retired and the shop moved. I believe his son took it over. They had a GTR in a clear bubble cover in the shop back then, pretty amazing. It was the same car at Rennsport about 10 years ago.

gpr8er wrote: Sat Jan 28, 2023 3:23 pm Greg built my trans about 12 years ago. His shop was nearby, he's since retired and the shop moved. I believe his son took it over. They had a GTR in a clear bubble cover in the shop back then, pretty amazing. It was the same car at Rennsport about 10 years ago.

I wrote an article for 000 magazine about that car. If you are into the 944 GTR, it's worth a read. Greg is the real deal around the front engine Porsches, and spent hours on the phone with me about that car... It's been a while, but if memory serves, the original motors were actually developed my McLaren Engines in Michigan before Andial took over. They were rated at 575hp, but most drivers said it made more. Either way, it had a higher power-to-weight ratio than a 918. I did a TON of research for that article, and talked to a lot of the people involved back in the day, including the McLaren and FABCAR guys, and a lot of the racers who actually drove them in the TransAm and IMSA series. Also dug up a number of parts lists and hand-drawn sketches showing some of the engine and chassis systems (reproduced in the article). No one knew the whole car better then Greg though.

https://000magazine.com/shop/008/

It makes sense if the boost to backpressure ratio is close to 1, which may well be the case on such an optimised engine.

A friend has now a higher boost pressure than exhaust back pressure, on a different type of engine though.

Thom wrote: Sun Jan 29, 2023 1:50 am It makes sense if the boost to backpressure ratio is close to 1, which may well be the case on such an optimised engine.

A friend has now a higher boost pressure than exhaust back pressure, on a different type of engine though.

Yes, that is very forward-thinking for the time. Porsche was aware of the issue in the days of the 951 as they specified stiffer exhaust valves to counteract exhaust back pressure, but the agricultural triple-K turbochargers and constraints of production and spool-up requirements meant they had to live with what they had.

The 944 GTR appears to have very "tuned" exhaust headers in addition to the ITBs and probably quite aggressive camshafts. I wonder what sort of wastegate spring would have been required for such a setup. Would be quite cool to pick the brain of the designer.

http://johnstraub.blogspot.com/2012/02/ ... g.html?m=1

Here is the link to the Alan Johnson GTR I have mentioned in past posts.

As far as I know I am the only person that used their chip in my 86 944 turbo back in 1993-95. MCL Porsche in Vancouver got it for me.

Tom not sure if you came across this in your research for you article.

I was just searching for information on the chip I once had.

Yes, I actually spent an hour on the phone with Alan Johnson. Good guy. He was not a fan of the car -- hated the transmission. I still have a transcript from that call (and other racers). Piecing together history from a old memories like this was interesting, since everyone witnessed/remembered events from their own, sometimes limited, vantage point. My guess is that chip was done by (or for) Andial, since the original McLaren-prepped motors used a Kugelfischer mechanical injection system.

That chip was far superior to the Autothority from same vintage.
Woke the 1986 car up significantly as the stock chip was acting funny due to removal of the restrictor in the wastegate line attached to the intercooler pipe.
Put on 50,000 miles using that chip.

Interesting thing about my 87 turbo that I purchased out of Japan with 40000 original km is it was originally ordered from a Porsche dealership in Southern California that closed down. It left to Japan with the person who bought it.

That information was directly from Porsche Cars North America. They actually sent me a letter with the factory history back in 2008.

I feel there is a good chance my 87 may have come from Alan Johnson Porsche dealership.

I haven’t reached out to Porsche since my initial research

According to John Broeck from MCL the factory chip documentation was used to make the new chip….. I am remembering what he said back in 1994.

Texas Porsche Dealership Asking $925,000 for 1981 Porsche 924 Carrera GTR

https://www.thedrive.com/news/30473/tex ... arrera-gtr

Another 2000 lb perfectly balanced analog sports car the 924 Carrera GTR, the new over weight supercars today don't compare.

To go racing in the Group 4 class at Le Mans, Porsche needed to homologate the company’s 924 race car. As such, Porsche built 406 road-going versions of the 924 Carrera GT to satisfy the FIA’s rules. Porsche being Porsche and looking to over-engineer everything, two subsequent evolutions of the 924 Carrera GT followed; a 924 Carrera GTS and the 924 Carrera GTR.

PORSCHE OF NORTH HOUSTON
Though you wouldn’t call the 924 Carrera GT’s production run of 406 plentiful, it’s practically omnipresent compared to the 17 only 924 Carrera GTRs Porsche produced. Of those 17, nine cars total qualified and/or raced at Le Mans. To get each car ready, Porsche took the standard 2.0-liter turbocharged inline four-cylinder engine and threw every ounce of motorsports engineering at the minuscule block. The end result was an engine that produced 375 horsepower and 299 pound-feet of torque.

1980 924 Carrera GTR 375 hp 0 to 60 2.9 sec. 9.95 sec 1/4 mile curb weight 2000 lb.

In 1981 the 924 Carrera GTR was the quickest car sold by Porsche.

With the 924 Carrera GTR’s power now set, it found itself a new intercooler, dry sump oil system, a stripped-out interior with full roll-cage, fully adjustable race-bred suspension, the brake system off of a Porsche 935, and side-exit exhausts. In race trim, the 924 Carrera GTR weighed in at a featherweight 2,050 pounds, which meant the cars were capable of hitting 180 miles per hour down the Mulsanne straight (before the chicanes were added) at Le Mans.

Porsche brought a handful of 924 Carrera GTRs to compete in the GTP class in the 1980 Le Mans 24 hour race, with the best car finishing sixth overall ahead of everything except prototypes.

The 924 had a great history in racing, in race trim the maximum power they got from the 2.0 litre Audi block engine (it originally was a Mercedes engine), was 550 hp,

later on using the new 2.5 turbo 944 engine in the 924 GTR...there was no 944 GTR.... it was a 924 GTR with the new 2.5 litre turbo Porsche engine used later in the 944 Turbo.... they got 750 hp from that engine.

At Le Mans the Porsche 924 GTR Carrera 2.0 litre Turbo was quicker then the 944 turbo engined race car when restricted to Le Mans engine power restrictions.

Later on the road going 944 used the wider body look of the 924 Carrera GT/GTS/GTR....

Trans-Am Sears Point 1985 Sears Point International Raceway
#36 Paul Miller (USA) Porsche 924 GTR Carrera Turbo, in practice set a new lap record 1:34,234 this record wasn’t broken till 1995.
550 hp, (trans am tune), 2050 pounds, faster then the American 650 hp V8’s it was racing against.