Strabo

I got to thinking about dyno results after a recent thread about RSA and C2 horsepower.

According to factory specs, my RSA makes 247 horsepower. I also have the results of a dyno test showing 244.3 maximum horsepower at the rear wheels. This did not make sense to me because power loss in the drivetrain should be much greater than 2.7 hp. 10-15% are common rules of thumb.

So I called the dyno people. The dyno man remembered my car and told me that they have tested "a ton of" RSAs and C2s. He said that they have found that C2s normally show 225-230 hp, RSAs about 245. They figure that about 30 hp is lost in the drivetrain in a 911. This is based on testing motors on both a chassis dyno and an engine dyno. So the average C2 motor would make about 255 hp and the average RSA motor about 275 hp.

The dyno man talked about what Porsche might have done differently with the RSA motors, but it was obvious that he was speculating about it. He was much more definite about the dyno results.

Strabo

LouZ

Our local PCA chapter, Riesentoter, is holding a "Dyno Day" on Saturday. I'm dynoing my '90 C2 because I want to confirm my seat of the pants HP and torque figures (it feels a lot more than 247 engine HP). I understood that the ratings from the factory were the absolute minimum that Porsche would allow out of the door.

While I'm there, I'll ask if anyone has a definitive answer about the RSA versus C2 motors.

Jim Michaels

The truth is out there. Until Fox Mulder discovers it, I'm going with the official Porsche answer. The 92/93 C2 and the RSA were reported to have the same engine type (M64/01), the same displacement, the same compression ratio, the same DME, the same fuel requirements, and the same hp and tq numbers at the same rpms. Even if the rumor about the stronger M64/01 engines going into the RSAs is true, that would probably mean no more than 4 or 5 extra hp on average for the RSAs. Would they really put the stronger engines in the cheapest 911s? The 92 RS Touring, Basic, and Carrera Cup USA cars had the M64/03 blue-printed engine with the more aggressive DME and were reported to have only 10 hp more than the C2 and RSA. If anything, I'm more ready to believe that the RS and Cup cars had more hp than advertised (as has been suggested in these discussions).

Because I've read it in so many usually reliable sources over the years, I am convinced that the official Porsche power figures are on the conservative side, and that their official power figures apply more accurately to the lower hp engines than to even the average hp engines.

LouZ: Please let us know your dyno results.

Jeff Curtis

RSA and "regular" C2 HP figures are same same...period.

There is a rumor out there that the higher performing motors were slapped in RSAs and Cup cars, I dunno about that one.

You figure there may be a deviance of ~10HP at most with these motors?? ...coming out of the factory, that is.

Strabo

Well, I certainly have no no real knowledge of this, and I an not sure it is important. I was intrigued by having a dyno test result that showed almost no difference between factory specs at the flywheel and measured hp at the rear wheels. But how I manage my car on the street or track is way more important than a hp or torque number.

Does anyone have good estimate of how much power is lost in the gears?

Strabo

Myles

Strabo,

I agree with Jeff that the HP output of the RSA and C2 is identical. There is some information out there that the Cup cars were given the "pick of the litter" engines at the factory and put out about 10HP more than the stock 247.

Dyno results vary greatly from machine to machine and depend on the ability of the operator to properly account for atmospheric conditions. I just had my car dyno'ed after a complete rebuild (including a bunch of internal upgrades) indicate 236HP at the rear wheels. Pre-rebuild the stock motor (on the same dyno) had 216HP. The shop, Cyntex, indicated that C2's typically put out 216HP on his dyno.

Myles

Jim Michaels

Interesting new input on the hp question was recently posted on the "RS America or not?" thread at this forum. Go to page 3 in that thread and read Rennman's (Don's) lengthy post. The red "RS" mark on the engine certainly fuels the speculation on the hp question.

Adrian

I have posted on the other thread as well but it is time to have a few facts on the table before a new and exclusive engine is invented.

1/. Porsche give the same HP and torque figures for the series of M64/01 engine from 1989 to 1994 despite the fact that major changes were made to the engine and engine management system.

2/. Comparisons presented in such general terms are in my opinion totally invalid. If somebody says that they tested their 1993 RS America against a 1990 C2 I would expect the HP to be higher. Let us lok at some of the differences,
a). The RSA does not have a power steering pump.
b). The RSA has a plastic intake system which provides for less restriction to the air.
c). The RSA has the most up to date DME installed of the 964 series and not the original 911 series.
d). The RSA has the new engine temp sensor which provides for better timing control.
However a 1993 C2 has all these as well except it has a power steering pump.
My point on this comparison issue is let us compare oranges with oranges. General statements like those above are off the mark.

To the specially selected engines. Porsche run a production line. I doubt if the engine test cell results get anywhere near the production line. Plus I believe the RSA engines would be delivered to the test cell in the ready to install condition which means the power steering pumps are not installed. I somehow doubt that Porsche would finmd a better engine and then strip parts of it to intall it into a RSA. Remember that unlike the RS series and the Carrera Cups that the RSA was "cheaper" than a standard C2.

Now to a RS fact without giving too much away. I was involved in an experiment where DMEs from a RS and Carrera Cup were installed into a C2 and tested. The results were suprising to myself in a very positive way. Knowing what I know about this experiment I am not surprised that many 964s will show higher HP epsecially those with the -03 DME installed.

The red RS marker on the engine tells the production line that it is for the RSA. Why mark it? Simple, no power steering pump. The RS was the same so they used the same marker because the engine line is not like the actual production line. The RS had its own special place in the early days because the bodies had to be brought up to 1993 spec but the engines were 1992 series.
Summary: The RSA is not an X-file. It is what it is, a lightweight cheaper version when built of a C2 coupe. There should have been more of them. The ROW never got one of these cheaper versions.

Ciao,
Adrian
911C4

Jeff Curtis

Man oh man...I couldn't have said it better myself!!

I like the "X-files" reference, I'll have to use that one day. <img border="0" title="" alt="[Wink]" src="wink.gif" />

J richard

Adrian brushed on my thinking; how many HP does it take to run the power steering pump at rated rpm?
Seems to me it could easily be 5 hp of parasitic loss just to provide static pressure. Anyone have a good guestimate? That alone could be the difference (and a real difference) between the RSA and the C2...

Regards

LouZ

I just posted our full Dyno Day results under the post "C4 Dyno Question".

Two 964's ran, my stock 90 C2 Tip put out 207.5 HP and a modified 94-964C4 hit 217 HP (it has been chipped, with intake and exhaust mods).

Adrian

Dear Lou,
I wonder how much money the C4 owner spent for a whole 10 HP. I do not suppose your know exactly what modifications that were carried out. MAF? etc.
Ciao,
Adrian
911C4

Christer

Adrian

I went from 207rwhp to 225rwhp with a complete exhaust change. The cost was I guess around £2000 by the time it was imported and fitted. If my engine was producing 250fwhp in the first place, JZ Machtech said that they would be fairly confident of getting up towards 300fwhp with their chip (they get around 20-25hp with their chip and decat). As my engine was showing around 237fwhp they told me that it was probably not worth doing the chip. More usefully, my torque went from 231.1 to 250.0 lbft.

Not cheap though per hp.....!

chris walrod

didn't the RS engine have a single fan/alt belt hub instead of the dual system?

Jeff Curtis

Are you referring to the "RS" or the "RSA"??

The RSA pulley lineup is EXACTLY the same as a C2/C4.

The RSR pulley is probably what you are referring to...it is an aluminum hub, no bearing, one pulley.

As for what assembly the European "RS" uses, I'm not sure on that one.