Andre The Giant

Where and how is the same 5.0 L engine found in the US MY 85 (s)and the one for the S4 produce different HP numbers, my MY 85 produces 288HP and the S4 produces 316 HP.

Is it mainly the intake that makes the difference ?

Tom in Austin

Entirely different designs, only 5.0 displacement is the same. One of the big differences was the resonant-intake manifold solution on the second-generation 4V engine, but many other things changed as well.

FLYVMO

The '85-'86 lacks knock sensors which requires a more conservative timing curve = less power. You can get really close to the S4 engine power with tuning and adding knock sensors. My '86.5 went from 240-ish RWHP to 275 RWHP with aftermarket ECU, knock sensors added and re-tuning. Can probably get close by adding some Porken chips and shark tuning the stock ECU.

Of course the intake is different, cams are more aggressive (similar to GT cams), computers are different.

Cheers!
Carl

davek9

Also a US 85/86 and 86.5 is/was actual rated at 292 HP and not the 288 HP (the 288 HP engines have 9.3:1 compression).

The biggest difference is the Computer timing/fuel and the Heads/Intake as already stated.
Compression at 10.0:1 is the same as the S4.

Dump the CATs or use Hi-Flow's, Refresh the Engine (all working as stock) and then add PKen's S300 chips and be happy

Dave

Vilhuer

Even block is different due to intake setup. Basically only interchangeable parts are crank and rods if factory is asked.

davek9

True and they changed from Studs to Bolts for the Heads

SMTCapeCod

Jeez, all this time with S3s and I didn't know that.... (292)...great thing about this resource.
Now, if I can after a couple decades, finally become adept at getting the whole (intake) apparatus sealed up tight, well that would be pretty great too.

bureau13

Where we the 288 hp engines sold? Were those the ones for Australia and a couple other places...Japan maybe? I know I read the S3 engines went somewhere other than the US, and that they were not as strong for whatever reason...

hwyengr

I think I saw once that the US engine was 288hp by the SAE method, and the low-compression Aussie/Swiss 32V was 288hp DIN. The 292 for high compression was also DIN.

The archived road test on C&D's website rates the 10:1 engine at 288hp, as does the '85 factory sales brochure (288hp SAE net (215kW)).

Vilhuer

M28/43 and M28/44 is 10.0:1 and 288 DIN = 292 SAE
M28/45 and M28/46 is 9.3:1 and 284 DIN = 288 SAE

Only difference is pistons. Low CR engine was available only in '86 MY.

M28/45 and M28/46 were sold:
214 C00 Germany
49 C10 Switzerland
2 C11 Austria
150 C23 Australia, all RHD

Japanise '85-86 used same high CR engine as US cars. All were LHD, 73 in '85 and 100 in '86.

The Forgotten On

Didn't the S3's also have smaller valves than the S4's?

Vilhuer

Yes and different heads, valve springs etc.

hwyengr

I still think you've got that backwards. 1 PS (DIN) = 0.986 SAE Net HP.

Andre The Giant

Wow, thank you all for this great info. I have learned more new info about my car, I thought it was 288 HP like Wikipedia says, but as I can see that was wrong. I guess I have a few options if I want more HP, get a GTS...lol I wish, install Pken S300 chip ( I don;t think I will since I want to keep the car original as much, install high flow cats, I might do this in combination with the X-Pipe, which should provide me around 27 to 29 HP extra which should bring me in the range of the S4.

Again thank you all, this forum is such a great resource to have, real experts.

Vilhuer

True, its other way round. German horses are smaller so four more are needed.