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Mine is 310 bhp it says so in my owners manual so it must be true
I have heard different views on the interference issue but the fact mine has a belt tension light and the US ones don't i'm told, maybe suggests that they are. I have high lift cams so maybe this makes a difference.
I would love to know for sure
Never Dynoed mine, but I did bend some valves. So interference for sure. Make sure you are talking about a Euro S motor. There were also non S Euro 16V motors that were very close to US 4.5 motors in most ways.
After having my new 86.5 motor dyno'd I have learned the not all dyno's are equal. Also is the hp at the rear wheels. Do the Euro's have gobs of torque compared to US cars?
My understanding is that the high compression 310hp 4.7l M28/21 & 22 in the 84-86 S2 is clearly an interference motor.
The 300hp 4.7 M28/11 & 12 in the 80-83 Euro S (CIS injection) may or may not be, depending on who you ask. I had always heard that they were not, but some real experts have said on here that they are.
And everything I've heard and read indicates that they are an honest 300hp.
What I found interesting (and pointed out to me by Jim Doerr) is that Porsche lists a 1979 928S...didn't know that existed!
It doesn't. Its calendar year when first S were made. Production started in late summer 1979 for '80 MY. Same data also lists 1983 310hp LH-Jet which is '84 MY etc.
Interesting info. Unrelated, but the USA S models are listed as 242HP in that pamphlet as compared to the 234HP figure that I have repeatedly come across.
I'd definitely believe 310hp. No, the Euro motors don't make any more torque compared to the US engines. When I put the Euro parts on top of my US 4.7L I dynoed that car again on the same dynapac. The torque was identical, it just didn't drop off nearly as fast on the top end. Peak power moved from something like 4500rpm to 5700rpm.
I think I know from where mixup between 234 and 242 comes from. Several factory documents say 234 while some say 242. In WSM it says both, 242 DIN and 234 SAE HP. Normally difference between DIN and SAE is around one more DIN HP for each 100HP + 1HP. For example S4 has 320 DIN and 316 SAE, GT 330 vs 326 and GTS 350 vs 345 and so on. In case of 234 vs 242 they can't be both right for same engine. So one number is wrong or they must be for different type of engines. In any case US number is almost universally given as 234HP so its likely correct. If 242HP engine exists its likely some version which were not used in any production model.
SAE vs. DIN is interesting. An HP is still an HP but it's in the correction from measured ambient conditions (temperature and pressure) to the standard conditions where the difference comes out.
On the dyno, I always look at DIN because that's how Porsche spec'd the cars (mostly) and it'll be a little bit more.
When I dyno'd my manual Euro S (after sorting) on a Dynojet it came out at about 255 RWHP DIN which suggests 300 BHP. Of course, the dynojet numbers themselves are fudged to give higher numbers but the results felt good.
05-18-2016, 08:53 PM
