tmw157

My '97 C2S with 75K miles was rebuilt from main bearings up at 60K. 3.8 Mahle kit was installed at that time. I kept the heads and cams stock. We didn't rechip at the time. GHL exhaust, open airbox w/K+N

I recently decided to do a live remap and found that car did only 220 hp on a dynapack. Problems with the tuning software prevented the chip remap..(my mechanic uses an outside tuner with dyno for his track customers but for some reason he couldn't crack the code on my ecu-last 3 digits ending in 376)

Leakdown ranges were 0-2% and compression ranges were 215-218 (or close) I was just told.

My mechanic will be checking for codes tomorrow, but is at this time sort of at a loss to explain why a tight, rebuilt 3.8 is only doing 220 on the dyno. Given that when I finally do get this car remapped (I'll be sending the ecu out to Steve W., although I would have preferred the live remap) I may realize another 10%, isn't this still a pretty dismal result for this engine? Shouldn't it be doing a lot better even though it's ecu is still mapped for a 3.6? I haven't had any CEL issues since the rebuild.

Car runs pretty well otherwise, feels like a healthy 3.6. My mechanic is extremely talented as well as honest--very well thought of in the Porsche racing community out here and for good reasons... I may feel a bit awkward, but should I be asking him to run other checks on this car before I send the ecu out to Steve?

TIA

Steve Weiner-Rennsport Systems

I don't have any experience with Dynapak results so I cannot make fair comparisons with a Dynojet or Mustang dyno's. 220 RWHP seems low to me although there may be some setup issues with the dyno and I'd wonder gear the runs were made in.

Some thoughts,....

1) Since it sounds like the rings have seated (based on the leakdown figures), I would like to know what gasolines were used for the dyno runs.

2) Did anyone monitor knock sensor activity during the runs? This is related to #1.

3) Cam timing accuracy? (this is one that gets overlooked as its not easy to do this properly on these motors).

3) Did you record AFR's during the runs? Loo lean or too rich = less power.

Generally speaking, the 3.8 P/C's adds more torque, rather than power to a 3.6. For more overall performance and to take full advantage of those larger P/C's, we usually install RS cams and RS intake valves (along with ECU re-programing) to see the results that one expects for the expenditures. Most of our 3.8 RS spec engines make 310 HP and many do better than that, depending on exhaust system.

Hope this helps,

tmw157

Thanks Steve, I'll ask when I pick up the car later in the week. What is AFR?

Gas used (I assume) was the 93 Sunoco that was in the tank.

Should I get to the bottom of this low power issue before I send you my ecu?

thanks as always..

Steve Weiner-Rennsport Systems

AFR=Air Fuel Ratio.

I'd guess 93 as well but thats why I asked about any knock sensor activity. It tells me what the engine "thinks" about that particular batch of gas.

I would check everything out before you send the ECU to me so we both know what to expect.

schmidtwerk

That sucks! My first 3.8 Vram made 325hp on an engine dyno (not chassis) with RS cams, valves, headers, programming. My second 3.8 a stock real factory 3.8 RS Vram engine with full catalyst, stock mufflers, and stock programming made 301hp on the same engine dyno. Both results were on a standard atmosphere day. I would say something is wrong at 220hp at the wheels unless the test is performed in Denver on a hot day.

TheOtherEric

Like Steve said, you need to know afr's. Personally, I would have it dyno'd by someone who can measure AFR (which IMHO should be everybody owning a dyno). And I'd also get a Durametric and log Timing and RPM during the dyno run and also during some street pulls to see what the timing looks like. Steve can probably tell you what timing should be at WOT so you can see if it's being retarded.

If all this sounds completely foreign to you, well, strap in for a long expensive ride.

Let us know your progress, and good luck!

tmw157

What is durametric? log timing? I should add that oil consumption is about 1100mi./qt. Despite good leakdown and compression? Prior to rebuild it was about 500mi/qt.

If I don't get some good answers to the questions that have been asked so far, I may just bite the bullet and ship the car out to Steve after Thanksgiving.

TheOtherEric

Google is your friend.

www.durametric.com

I had some funky loss-of-power issues and used the durametric to see that my timing was being retarded.

But it doesn't sound like you have the interest or inclination to investigate this stuff yourself. Nothing wrong with that at all, just be ready to write a big check.

Whoa, are you saying you've driven 1,000+ miles with a 3.8L conversion and no re-tune, and no idea about your AFRs?? That sounds like a reeeeally bad idea.

tmw157

Sorry about not googling-you're right that was sheer laziness. RE: the "interest or inclination" remark. I'm not a mechanic, my interest and inclination at this time is in finding the right person to help figure this out. Life can get tricky and throw us a few curves as we age....tuning the 993 just hasn't been uppermost in my mind until very recently when things in my life settled a bit. The fact that I am still alive and able to enjoy my car is pretty good for right now...

I was told by the engine builder two years ago that it was OK to run with the ecu as is. I gather this is bad news? By the way, this is not the mechanic who dyno'd my car last week.

cheers

tmw157

I just realized something I wrote may have been misinterpreted. My comment:

" If I don't get some good answers to the questions that have been asked so far, I may just bite the bullet and ship the car out to Steve after Thanksgiving."

Is poorly written. I am so sorry--it was actually meant to say: "if I don't get good answers from my mechanic to the questions given me by the folks on this forum. "

Please forgive, I am extremely grateful for all of the responses I receive on this forum.

Steve Weiner-Rennsport Systems

You are an enlighted man,.....one's priorities and perspectives are altered by experience as we grow older (and wiser) and its important to focus on whats important and what isn't. The fact that you can enjoy your car and what pleasure it brings is truly the reward.

Generally speaking, major changes such as displacement, cams and certain exhaust configurations require different ECU mapping and thats why I inquired about your air-fuel ratios. Normally, a 3.8 upgrade requires changes to the fuel mapping to run safely, much less optimize for performance.

Raceboy

On 993, fuel map is ok even with 3,8 coversion as MAF measures real mass of air and ECU can compensate VE changes to some extent. But that doesn't include timing.

Ryan C

Some of the engines people posted for comparison all seems to have more than stock 3.6 heads and cams. Maybe the added displacement needs to breath a little more in order to make more power.

CarmG993

tmw157 - I have a 3.8l which was done by Andial ( I purchased car like this) I believe my HP came in at 321HP and 280 Trq on the chart that was provided.
My car had the stock ECU in it. I had my ECU done by Steve (RennSport) to a 3.8l shortly after I got the car.
Others who have driven my car say it is very strong.

NP993

I wouldn't think you'd experience much more than a slight increase in torque with a 3.8 piston & cylinder kit. All your car has is .2 extra liters of displacement -- a tiny fraction of the engine's total size. Without doing the rest of the RS 3.8 engine upgrades -- cams, valves, varioram manifold, injectors, etc -- I wouldn't be surprised if even after tuning the ECU you only recorded a very minor power increase.