I own two 1985 cars.

Euro
4.7l
16V
rated 310bhp
not tested but unlikely to put down any more than 310, if that
feels pretty powerful at higher revs, much less torquey

US
5.0l
32V
rated 288bhp
tested 316bhp
feels torquey, and I'd say could outperform the Euro all the way

So .... not that anyone asked, but I think a US 32V will trounce a Euro 16V everytime. At least, in my case.

 

My euro was definately not very torquey.

But it would really scream at high RPM.

It might be slower off the line, but it might do a good job of reeling in...

It probably also has a lot to do with how much smog stuff was added to the euro.
The US cars and the s4 in particular, were meant to have the same horsepower
regardless of what country they ended up in. But the difference between the
non-restricted, non-cat, true euro, and a smogged and bogged US car, is
a pretty big difference...

 

Put the same adjustable cam gears (tuned of course) and manifolds (or headers) on the Euro and see what it will do.

 

BC, both have the same nostrils.

 

Well, if all is equal, and you have more valves, and more displacement, it ought to be faster...

Since you have both, you should put them both on the dyno on the same day...

 

I have a 1984 928 S2 5spd and a 1990 928 GT. The S2 is as good as the GT. Ordinary S4 in manual or automatic form do not stand a chance...

The S2 engine is so rev-happy. Very similar to the GT in its characteristics - almost nothing below 4K and then it roars up to 7k rpm, trouncing odinary 32v.

The S2 is very, very sensitive to fuel. It needs RON 98 to get the full potential of the higher compression- 10,4:1. You also want the green wire (the RON selector) around the ECU unplugged. Then 32v cars will be seeing your numberplate on a regular basis...

The fastest 928 in the UK is a 928 S 5spd with the 300bhp engine - 13.6 for the 1/4mile... S4 manual or Autos are yet to go thru the 13sec / 100mph barrier...

 

Are both 5 speeds, or both autos?
Do you know the differential ratio for both?

I have driven a couple of '86 autos, and wouldn't think they would be in the same realm as my '80 Euro S (before racecar migration). I even thought my '82 US 5 speed (220hp) seemed quicker than the '86s with autos.

 

Stan both are autos. I believe the Euro auto for that year came in 2.36 or 2.54 rear end and we know the US has 2.2. I think taking into account the more aggressive gearing, the Euro should be tearing the road up from zero, but the revs just don't pick up as fast as on the US car, which is a large reason why I believe the US car is a more torquey engine.

 

Herr Heinrich,

Do you have your octane corrector connected?

 

Herr AngelicDude, vee shall checkkkk

 

Herr Heinrich,

That small single green wire with a plug somewhere in the vicinity of your 928 S2 ECU was added by Porsche to compensate for lower grades of fuel by tricking the EZK to retard the timing. Now, if you have 98 RON fuel readily available, you should unplug this wire and notice some gain

 

again, i had a 2 valve version of the 5 liter 85 US (with euro intake and heads) 293HPat the wheels
the Holbert S4 with 85 cams (gt like) did 285 with no cat and then 320-335 at the wheels with some minor mods and the level 2 devek headers (same on both)
thats both 5 liter, one with 2 valve, and both same headers. 293 vs 320ish hP, but keep in mind, thats the Holbert S4. most S4s are in the 298 to 305hp range. AND this is the S4, not the smaller valve, lower CR 85 US 5 liter 4 valve .
Lets face it, the cars same to same, are pretty close to the factory ratings. Most euro 85 owners get in the 250-260 rear wheel hp range, while most 85 owners get 250 at the rear wheels on the dyno.

your 316hp at the wheels for an 85 US is HUGE, and unheard of. there are only a few S4s that make this kind of hp at the wheels. heck, mine is in that range now! 316 to 320hp at the wheels after 3 seasons of racing.

also keep in mind, the 310 rating for a euro 85 is with only a 4.7 liter, while the 316hp for an S4 is with a 5 liter and the rating for a US 85 5 liter with the smaller valves and lower compression is 292hp (288hp). so, i dont know how you think a US 85 can trounce a euro 4.7 85, but if you have 316hp and its tested on a dyno , at the rear wheels, you have a rare fish! of all the S4s tested, most are in the 270hp at the rear wheel range and thats for about 50 that we all know of at dynos we trust.

MK

mk

 

Mark, those are bhp numbers, at the crank....

 

I guess part of the logic is, there are no Euro cars of which I have ever heard, tested at more than 310chp. However here is a US car tested at 316chp. And I've seen other US cars of same year at WAY higher .... like 290 at the wheels.

 

not to dive into that discussion again, but the gearing advantage will apply the hP differently depending on the speed ranges you are looking at. ingnoring 1st gear which is all about traction and wheels spin, the gearing can be a little of the factors. the main thing said a few times here, is that the car "revs better up high" etc. this is also only a factor if you use (race )the car inefficiently. meaning, if you want to test the max acceleration of the (any) car, run it at near max hp for as much of the time as possible. the 32 valve S4 has that resonant flap. its working in the 3500range and puts out HUGE torques comparatively to the 85 5 liter without it. however, between 4500rpm and 6400rpm, there is not much of a hp curve shape difference. meaning, the average hp difference,is pretty close to the max hp diff.

I want to know how a stock 85 US is getting 316 at the wheels!!!!!!

funny thing about the euro gears or the 2.75 or 2.72 boxes, is that scot and I did a highway race, and to my point, even though his pure 4.7 euro engine with Ljet, making about 260-270 rear wheel hp, vs my S4 with 320ish hp, he was pretty close right up to the point where he needed to shift into 4th at 80mph, where i was still in 3rd till 100mph beating him, but not by much. however, if the race was all the way to my redline, he would be quite a ways back (ie 115mph) all those trade offs in gearing you have to look at.

mk