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Hi Noah,
It is not possible to build a 2.5L, 8V Porsche 944 NA engine to produce 200 hp on pump fuel. The 2478 cc displacement with the standard crankshaft and a Michael Mount prepped cylinder head with oversize intake valves, 1mm larger; competition valve prep; optimized porting does not have sufficient displacement for a fuel/air charge to make 200 hp.
I have no doubt that MM knows exactly what hes doing here, but doesn't it seem like he left significant performance on the table with a stock cam and intake system? Was this build on a specific budget or had a requirement to look stock externally?
I believe his goal was to see what was the potential HP output for the 944 8V engine built with stock Porsche engine parts. The only non stock part was the JE pistons. He selected 4 in bore because that is the stock bore for a Chevy 350 cu in small block. He had to determine the pin location for the piston and the design of the piston top to achieve 10.8:1 CR.
This is my build for the 944 2.8L stroker 8V NA engine. The 2.5L standard block '87.
1.The block cylinders were were nikasiled, cylinder walls had scouring; installed microsquirt piston skirt oilers, and milled windage openings between cylinders #1 and #3. Sent the block to LR who coordinated this work.
2. LR designed piston supplied by Wossner 12.5:1 CR and selected Pauter rods.
3. Installed windage tray, screening and crankshaft scrappers
by http://www.crank-scrapers.com/Porsche_944.html
4. Installed 944 Turbo oil pan.
5. Purchased 3.0L crankshaft, LR race prepped the crankshaft.
6. MM race prepped 8V cylinder head.
7. Current engine has stock crankshaft 9R.
8. Rogue Tuning MAF with Rogue Tune chip for 2.8L stroker engine.
9. Adjustable FPR mounted on 951 fuel rail.
10. FiveOSports modern Lucas FI's
11. Exhaust was Noah supplied Stahl header, thank you for selling it to be several years ago.
The Wossner dome pistons have relief for JM high lift 0.502" camshaft, in my possession but not installed. At the time, I did not have refurbished hydraulic valve lifters camshaft follower surfaces (need to find company name) COVID held up this project for 1-2 years.
Results from chassis Dyno 2022.
1. The max HP on chassis Dyno with A/F ratio of 12.3 was 149 HP at 5500 rpm or estimate engine and transmission losses of 30 HP yields 179 HP. A side note: Output HP would be higher if shaved A/F ratio. I wanted to keep A/F ratio conservative for reliability. Fuel was 100 octane.
3. JM higher lift camshaft should add 15-20 HP.
4. Other test results. Not sure how to convert chassis Dyno torque to engine Dyno torque.
But here it goes.
The chassis torque curve was flat from 3600 -5100 rpm at 160 +/- 4 ft-lbs. So maybe flywheel torque was 170 ft-lbs.
5. The significant improvements over a 2.5L 8V NA are
a. @ 4000 rpm: the HP is +30, torque is +40
b. @ 4500 rpm: the hp is + 28, torque is + 30
c. @ 5000 rpm: the hp is + 28, torque is +30
d. @ 5500 rpm: the hp is + 18, torque is +20
e. above 5500 rpm, the HP and torque advantage decrease
about +8.
My engine build vs MM engine build output difference is in the ECU tuning to optimize F/A ratio. Too high F/A ratio produces less HP while too low F/A burns the piston. My ECU cannot optimize F/A ratio for reliability and output
In my opinion, the best aftermarket tuning ECU is https://www.dtafast.co.uk/products/. The bins for fuel are up 900 bin matrix while Microsquirt is 256 matrix, a significant fine tuning advantage plus a box to change fuel inputs on the fly.
Last edited by T&T Racing; 08-06-2023 at 01:55 PM.
V2, I want ITBs because the n/a 8v intake manifold looks boring to me & ITBs are exciting to think about. My faves are the Milledge square body carbon intakes. JRP944's concept look amazing also. I want the "kick" of the ITBs & because they are sexy. I've never driven with them.
The nice thing with the ITBs is that you can pick a shorter runner length which will tune the manifold to make power at a higher rpm than stock. The fact that the throttle blade is in the runner doesn’t enhance power output by itself.
The problem with ITB is that any setup you look at will be $2k+. You can modify the factory manifold and shorten the runners 2-3” for less money.
the factory manifold isn’t really an impediment to making 200hp with other parts; it is a good casting, big holes, easily ported if needed, good runner length. But shortening the runners a little might be enough crutch to get over the 200 mark if your other parts fall short.
fwiw a while back I had a 210hp 8v engine. 103/88 bore/stroke (2.9L). Pro-ported head, milledge 8S14 cam, 12.5 compression. Stock manifolds. It was a ripper. Tuned on VEMS. I ran e85 because I could get it easily. If you’re building an engine then it makes sense to use the big crank. Even at a moderate 1hp/cu in, the 3L crank would be 20hp over a 2.5 crank, not bad for $900-1100 that the cranks go for
Will the 3l crank fit in the 2.5l block without mods for it to fit & will the 2.5 front pullies & flywheel fit? The vib damper is different, no?
Then what do you do for cylinders, pistons, rods? You can only use the 100mm holes if you be strokin', correct? No other options?
Spencer I was so impressed you installed that engine. I know your heart was set on 16v S2.
This is my build for the 944 2.8L stroker 8V NA engine. The 2.5L standard block '87.
1.The block cylinders were were nikasiled, cylinder walls had scouring; installed microsquirt piston skirt oilers, and milled windage openings between cylinders #1 and #3. Sent the block to LR who coordinated this work.
2. LR designed piston supplied by Wossner 12.5:1 CR and selected Pauter rods.
3. Installed windage tray, screening and crankshaft scrappers
by http://www.crank-scrapers.com/Porsche_944.html
4. Installed 944 Turbo oil pan.
5. Purchased 3.0L crankshaft, LR race prepped the crankshaft.
6. MM race prepped 8V cylinder head.
7. Current engine has stock crankshaft 9R.
8. Rogue Tuning MAF with Rogue Tune chip for 2.8L stroker engine.
9. Adjustable FPR mounted on 951 fuel rail.
10. FiveOSports modern Lucas FI's
11. Exhaust was Noah supplied Stahl header, thank you for selling it to be several years ago.
The Wossner dome pistons have relief for JM high lift 0.502" camshaft, in my possession but not installed. At the time, I did not have refurbished hydraulic valve lifters camshaft follower surfaces (need to find company name) COVID held up this project for 1-2 years.
Results from chassis Dyno 2022.
1. The max HP on chassis Dyno with A/F ratio of 12.3 was 149 HP at 5500 rpm or estimate engine and transmission losses of 30 HP yields 179 HP. A side note: Output HP would be higher if shaved A/F ratio. I wanted to keep A/F ratio conservative for reliability. Fuel was 100 octane.
3. JM higher lift camshaft should add 15-20 HP.
4. Other test results. Not sure how to convert chassis Dyno torque to engine Dyno torque.
But here it goes.
The chassis torque curve was flat from 3600 -5100 rpm at 160 +/- 4 ft-lbs. So maybe flywheel torque was 170 ft-lbs.
5. The significant improvements over a 2.5L 8V NA are
a. @ 4000 rpm: the HP is +30, torque is +40
b. @ 4500 rpm: the hp is + 28, torque is + 30
c. @ 5000 rpm: the hp is + 28, torque is +30
d. @ 5500 rpm: the hp is + 18, torque is +20
e. above 5500 rpm, the HP and torque advantage decrease
about +8.
My engine build vs MM engine build output difference is in the ECU tuning to optimize F/A ratio. Too high F/A ratio produces less HP while too low F/A burns the piston. My ECU cannot optimize F/A ratio for reliability and output
In my opinion, the best aftermarket tuning ECU is https://www.dtafast.co.uk/products/. The bins for fuel are up 900 bin matrix while Microsquirt is 256 matrix, a significant fine tuning advantage plus a box to change fuel inputs on the fly.
Tom,
I had no idea you went so deep into this. I'm not surprised, but impressed is all. I bow to your greater knowledge.
Not something to overlook is washer fluid regulated for n/a. Not my first wish but might bring 10 hp or something.
I think it would allow for extended periods at the rev limit & reduce cylinder head temps & bump the hp up.
Perhaps it's comparable to E85 when used with pump gas.
Low hanging fruit for $600 ish.
Will the 3l crank fit in the 2.5l block without mods for it to fit & will the 2.5 front pullies & flywheel fit? The vib damper is different, no?
Then what do you do for cylinders, pistons, rods? You can only use the 100mm holes if you be strokin', correct? No other options?
Spencer I was so impressed you installed that engine. I know your heart was set on 16v S2.
Noah,
A 3.0L crankshaft fits, with no modifications necessary, in 2.5L block. The standard 2.5L front timing and balance shaft gear fits on the front end of crankshaft. The standard flywheel is used. You can iron sleeve the 2.5L block to use a 4 inch (101.6 mm) piston.
Just leaving this here... There is no doubt the 16v is better for track racing but isn't there a sweet simplicity & to the single cam engine? I love this engine. And in the 2.5 size, some say the 16v was a disappointment when the 944 S hit the track.
Oh, does anyone know why JM would pick these square looking throttle bodies over the more common shape? Is it to hide details of the build?
Noah, those are roller barrel throttles instead of butterfly throttles like we're typically used to. No obstruction at all in the flow path since the whole inner barrel rotates open.
Alright, who was the Rennlister, in the lightweight weight-green dedicated race-car in Europe?
Didn't he dyno like 212 hp in a 2.5?
What are the details of his engine?
Alright, who was the Rennlister, in the lightweight weight-green dedicated race-car in Europe?
Didn't he dyno like 212 hp in a 2.5?
What are the details of his engine?
Not something to overlook is washer fluid regulated for n/a. Not my first wish but might bring 10 hp or something.
I think it would allow for extended periods at the rev limit & reduce cylinder head temps & bump the hp up.
Perhaps it's comparable to E85 when used with pump gas.
Low hanging fruit for $600 ish.
08-06-2023, 02:11 AM
