jturbo

Does anyone have a dyno chart for the Cayman S?

FTS

http://www.caymanclub.net/topic.asp?...le=Cayman+Chat

Jim Michaels

Note the article by K-Man S (Ken) claiming at least a 13 rwhp gain (from 269 to 282) from removing the "restrictor plate" behind the driver's side air vent. There are several true believers there, but I'd like to see the test completed with dyno runs done the same day with and without the plate. Otherwise, the 5% differences in measured hp could be due to different test conditions, normal between-run variation in measurement, or the car having completed more break-in miles for the second test. If the same results are found in a complete ABAB experimental design, I'll remove the plate on my car, although I still wouldn't understand how removing the plate increases hp.

Doug&Julie

Interesting comment about the "true" horsepower possibly being well over 300!

Jim Michaels

Over 300 hp would be assuming a 15% loss through the drive-train. But someone reported finding only a 10% drive-train loss with the 997. If the loss is similar with the Cayman, that would place the measured hp around that advertised, but I woud certainly not be surprised to learn that some Cayman engines produced 300 hp at the fly wheel.

Doug&Julie

Ah...I wondered about that 15%. I mean, is that just and industry standard? ..or is that past Porsches? Anyway...I know the new motors and drivetrains are very efficient.

Helo Driver

Jim,

Realize that Ken ran his car only two days later with very similar conditions (temp, humidity, etc). He only drove 50 miles between tests. I personally believe that once you remove the restrictor plate, the car has to be driven about 50 miles so the ECU can re-learn and re-map the air/fuel settings. Therefore, a test done back to back may not yield as high of a horsepower increase.

Shane

Jim Michaels

Doug: The drive-train loss varies across car makes, and maybe even a little bit within a particular model, but many assume that the drive-train loss is likely to be somewhere between 12 and 15%. One could probably establish a rough estimate (within dyno error variation) for a particular engine and drive-train by bench testing the engine first (as most engine manufacturers do) and then again after it's installed in the car (which most manufacturers don't do, and Porsche suggests owners also not do).
Shane: You're assuming that removal of the baffle plate will require the ECU to re-map the air/fuel settings, but I think that's unlikely unless more air is forced into the throttle body (forced induction). I suspect the throttle body is already getting as much air as it can use.

Doug&Julie

Thanks.

Helo Driver

Jim,

Todays ECUs are constantly in a "learning" mode. They adjust to air temp, how hard the vehicle is driven, and the octane rating in the fuel. I don't know, but I'm assuming that removing the baffle plate would make a big enough change that there would be a noticeable difference on the reading that the MAF (mass airflow sensor) reads.

Bottom line is: I don't know. I was merely speculating.

Shane

Jim Michaels

What I mean is that I don't think that removing the baffle itself will cause the ECU to learn anything new or different. That's because I don't think there will be any new and different inputs for the ECU to adjust to. Several on CC have said that they can actually feel the extra 13 hp; that they can now spin a tire in 2nd, or power slide where they couldn't before. I suspect that this is the louder muffler effect, as a 4.4% hp gain would be very difficult to notice. I don't know either, so I'm speculating too. But after all we went through with the 964's (which could be helped by improved breathing) intake (cone filters, drilled holes, cut downs, and Cup air boxes) to get 4 or 5 more hp suggests that the probability of a 13 hp gain by removing a distant baffle would be very low. I hope I'm wrong, but I don't think so.

Helo Driver

I agree. 13 WHP from removing a restrictor plate seems nearly impossible. On my last car (Nissan), I removed a VERY restrictive air-intake-box and replaced it with a CAI (Cold Air Intake). I didn't get anywhere near 13 WHP nor did I expect it. 1 to 3 WHP maybe.

Shane.

PS. I hope that this modification does yield 13 WHP though. What a great mod that would be!

PorscheDoc

I was the one that ran the car for Ken on the dyno. It was done about 3 days apart, the weather was about the same. I was skeptical about the restrictor plate gains, but was quite suprised at what it did.

Jim Michaels

Welcome, Doc. Please get Ken in for a few more dyno runs with and without the plate to insure that the hp gain is due to plate removal and not something else. As you probably read, Scott Slauson claimed he could not get any gains from plate removal on the 3.4 or 3.8 motors, but some CC members are rejecting his claim in favor of your more favorable results. It's become a frenzy on CC, with plans to market a more professional looking grill to replace the baffle plate. I have no reason to doubt your numbers (other than the usual random error), but there is still good reason to doubt that the gains were due to the removal of the plate. Please don't give Scott reason to tell us about the pine-scented air freshener producing hp gains on the dyno again.

PorscheDoc

There was nothing else changed on the car, in fact it was the same tank of gas. Dyno results are there for general information, but no matter how you run the dyno, someone is going to disagree with your results, so it is impossible to please everyone.

Excuses I have heard:
You can't tell hp gains by the seat of your pants, you need to do a dyno run
Hm....car made hp....well, you ran the dyno wrong
You ran the dyno with the AC on
You ran the dyno with traction control on (not possible)
Your dyno reads Hi
Your dyno reads Low
You have the wrong kind of dyno
You don't have enough experience running the dyno
You have too much experience running the dyno and know how to manipulate the numbers
Your dyno is wrong, my butt dyno is right
Your fan putting out a 60mph head wind is not enough
Your fan putting out a 60mph head wind is too much
Your dyno software is biased
Your dyno software is not biased enough
You need to video the entire process so the rest of us can see that you aren't making everything up
Wow, you are really good at editing video to make it look like you aren't making everything up
You ran the dyno in 4wd mode
You ran the dyno in 2wd mode
You ran the dyno in hovercraft mode

My point, someone will always debate your numbers, even if they are standing right there in front of you watching you run the car. I had a customer in for a dyno war last weekend, his car was suppose to make 360 something to the wheels. He made 260 on 3 consecutive runs....and he concluded it was obviously due to my error and my dyno being wrong, even though the 9 cars I ran after him all made around where they were suppose to.

I will be happy to do as many runs as Ken wants for research purposes (on my dime), but it still will not make everyone happy. But that is ok, if the owner of the car is happy with the results, then I have done my job.