Project status....
+1 on interesting thread. Assume they were capped at 2.5lt back then? But there was a later switch to 2.6lt in some of your race series over there at one point. (The smaller motor I had on loan a few years ago was apparently built to 2.6lt. It ran out to a tad over 8000rpm. ) Look forward to your assessment of this one Michael and further more to the development of this for the future. I remember seeing some video of it at Rennsport (2023?) and whoever was driving it was being pretty careful. Nice to hear that it's going to be used in anger again. Keep the posts coming!
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SirLapsalot
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Looks like HSR will be the support series this year for IMSA VIR in August. Running a half season of IMSA MPC, but VIR will be one of the events we'll miss. Bummer! Would have been a great opportunity to see in person!
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Thom
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Is it because of technical rules in the series where the 944 GTR raced that the 2V GTR head was designed and used in 1987 instead of the then "new" 4V head of the 944 S?
From the pictures of the head that I can remember the inlet ports were extremely ported out, which may explain a huge improvement in flow over a stock port. Do you remember the flow figures?333pg333 wrote: Fri Jan 12, 2024 10:43 pm(The smaller motor I had on loan a few years ago was apparently built to 2.6lt. It ran out to a tad over 8000rpm. )
'90 944 turbo
Yes, huge inlet ports. Probably too big really. Flow figures were 279 in / 211 ex .600 @28" Cam .595/.526". Sorry not meant to threadjack. Back to the GTR.Thom wrote: Sat Jan 13, 2024 10:07 am Is it because of technical rules in the series where the 944 GTR raced that the 2V GTR head was designed and used in 1987 instead of the then "new" 4V head of the 944 S?
From the pictures of the head that I can remember the inlet ports were extremely ported out, which may explain a huge improvement in flow over a stock port. Do you remember the flow figures?333pg333 wrote: Fri Jan 12, 2024 10:43 pm(The smaller motor I had on loan a few years ago was apparently built to 2.6lt. It ran out to a tad over 8000rpm. )
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michaelmount123
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A few notes and perhaps some clarification.
In the mid 1980's, IMSA GTO had to be based on a production model, in this case a 951. So 2.5L, a 2V head, and a single turbo was mandatory for Porsche's entry. There were no production turbo cars with the new 4V cylinder head. A turbo raised the displacement calculation by 1.4, so it fell into the over 3L category (GTO) rather than the under 3L class (GTU).
The 944GTR was an all-American effort, thanks to Al Holbert who headed up PMNA. Porsche had never done this before, and contributed many components to assist in the effort. The wheel hubs are 935/962, same with brakes. The bespoke engine case and cylinder head are Porsche's doing, and Bosch/Motronic was adapted from the 962 . The chassis was by Fabcar Engineering who had done chassis development for the 924GTR and impressed Holbert with their results. Engine development early on was by McLaren USA with MFI, but results (primarily longevity) were disappointing. Andial stepped in and brought huge improvements to the engine program. Performance became aligned with the front-runners in GTO. Although Andial continued with engine development, the program ceased with the demise of Al Holbert in 1988. Such a shame.
Yes, solid lifter camshaft reportedly by Dima Elgin, slip-in Nikasil 100mm cylinders similar to the modern Cup engine, Cosworth pistons, Garrett turbo (more info on turbo specs when available), balance shafts, billet 78.9mm crankshaft, Carrillo rods, dry sump lubrication with 2 scavenges in the oil pan, one on the turbo, and a pressure section feeding directly into the block's main oil galley. Oil filtration is in the return to the oil tank.
In the mid 1980's, IMSA GTO had to be based on a production model, in this case a 951. So 2.5L, a 2V head, and a single turbo was mandatory for Porsche's entry. There were no production turbo cars with the new 4V cylinder head. A turbo raised the displacement calculation by 1.4, so it fell into the over 3L category (GTO) rather than the under 3L class (GTU).
The 944GTR was an all-American effort, thanks to Al Holbert who headed up PMNA. Porsche had never done this before, and contributed many components to assist in the effort. The wheel hubs are 935/962, same with brakes. The bespoke engine case and cylinder head are Porsche's doing, and Bosch/Motronic was adapted from the 962 . The chassis was by Fabcar Engineering who had done chassis development for the 924GTR and impressed Holbert with their results. Engine development early on was by McLaren USA with MFI, but results (primarily longevity) were disappointing. Andial stepped in and brought huge improvements to the engine program. Performance became aligned with the front-runners in GTO. Although Andial continued with engine development, the program ceased with the demise of Al Holbert in 1988. Such a shame.
Yes, solid lifter camshaft reportedly by Dima Elgin, slip-in Nikasil 100mm cylinders similar to the modern Cup engine, Cosworth pistons, Garrett turbo (more info on turbo specs when available), balance shafts, billet 78.9mm crankshaft, Carrillo rods, dry sump lubrication with 2 scavenges in the oil pan, one on the turbo, and a pressure section feeding directly into the block's main oil galley. Oil filtration is in the return to the oil tank.
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michaelmount123
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Well, Porsche certainly thinks so. I never ran them in my own engines, primarily for simplicity. I never experienced any ill effects and every shift was at 8000rpm. I'm not going to buck Porsche nor Andial on this, however, and will keep them when rebuilding/upgrading the GTR engine.
I wonder if McLaren USA wasn't too used to working on huge displacement n/a V8s and found the little turbo 4 banger just a bit of a mystery? Amazing how many bespoke parts Porsche made for these front engine cars over the years. Even though the naysayers describe (berate) them for being parts bin cars.michaelmount123 wrote: Sun Jan 14, 2024 4:48 pm A few notes and perhaps some clarification.
In the mid 1980's, IMSA GTO had to be based on a production model, in this case a 951. So 2.5L, a 2V head, and a single turbo was mandatory for Porsche's entry. There were no production turbo cars with the new 4V cylinder head. A turbo raised the displacement calculation by 1.4, so it fell into the over 3L category (GTO) rather than the under 3L class (GTU).
The 944GTR was an all-American effort, thanks to Al Holbert who headed up PMNA. Porsche had never done this before, and contributed many components to assist in the effort. The wheel hubs are 935/962, same with brakes. The bespoke engine case and cylinder head are Porsche's doing, and Bosch/Motronic was adapted from the 962 . The chassis was by Fabcar Engineering who had done chassis development for the 924GTR and impressed Holbert with their results. Engine development early on was by McLaren USA with MFI, but results (primarily longevity) were disappointing. Andial stepped in and brought huge improvements to the engine program. Performance became aligned with the front-runners in GTO. Although Andial continued with engine development, the program ceased with the demise of Al Holbert in 1988. Such a shame.
Yes, solid lifter camshaft reportedly by Dima Elgin, slip-in Nikasil 100mm cylinders similar to the modern Cup engine, Cosworth pistons, Garrett turbo (more info on turbo specs when available), balance shafts, billet 78.9mm crankshaft, Carrillo rods, dry sump lubrication with 2 scavenges in the oil pan, one on the turbo, and a pressure section feeding directly into the block's main oil galley. Oil filtration is in the return to the oil tank.
It will be interesting to see the crankshaft among other parts.
