Dyno day tomorrow

I picked up a 99 996 last weekend and I have a bunch of parts in my living room ready to go on it. So tomorrow morning I head to the dyno to baseline the car in stock configuration and then I can start putting the parts on. Ive seen a lot of conjecture about gains & losses for this and that but I kind of like the idea of checking things out for myself. So the plan is to dyno the car after each mod goes on ie stock baseline then with / CAI / headers / Cats / Muffler. I should do a poll regarding the dollar cost per horse power gained (bearing in mind it could be nil !) The car is a UK 99 C2 6spd with 68.5K on the odo and the temp will be around 14C tomorrow. What are we guessing for the stock / baseline run. (Dyno dynamics dyno)? The parts list by the way for the subsequent runs is as follows: Fabspeed competition cold air intake Ebay cheapie headers Fabspeed 200 cell X cats Fabspeed Maxflow mufflers FWIW I have heard that the ebay headers have produced a power loss for other rennlisters but I haven't seen a corresponding dyno sheet, hence that is one of the things I am most interested to see for myself. Should that turn out to be the case I will swap the headers back to stock before carrying out the remaining dyno runs. This process will not be overnight by the way - especially if I get into strife with the header bolts which I am half (ok 95%) expecting. Cheers

Will follow this with great interest! And don't mind the haters who dismiss mods as universally useless. Value is certainly debatable, but potential effect isn't. Look at what Porsche does to get the last few percent from an engine, and guess what: revised intakes and ECU tuning often make the list. The Sport Classic is a recent example. This stuff isn't magic, but it has its place.

Really curious to see the results! My guess is no gain from any of that stuff. But it will no doubt be fun!

this will be good..... at the wheels I "guess" the baseline at 245 (see who yells at me, I just GUESSED!)

I actually want to dyno my car, too. I have no 'before' number for any of my mods, and I can predict the debate here with such precision that I think I could write the entire thread myself and spare everybody the trouble. But I think it would be a very cool addition to my car's little history binder, and some indication of a healthy motor if the number is in the ballpark.

I'm looking at X-Cats (either Fabspeed, Europipe or M&M) so will be following your progress...

I should be faster around the track because if nothing else, my wallet is considerably lighter.

baseline run....somewhere between 225 and 245. Post install.....240-255 Definitely curious to see how it goes as I'm looking at getting a full Fabspeed setup as well. BTW...make sure you do some hard runs after the install so the ECU "learns" to run full power.... sean

Sean MCR is right on the money. Baseline run 236.4 Hp Baseline plus Cold Air Intake (CAI) 241.4 Hp I've marked it on the chart but when I put the CAI on the car it was a case of removing the stock air box and just attaching the new intake pipe & filter, ie the CAI heat shield was not in place and so the intake was drawing in some warmer air. The most significant discovery was that the AFR became considerably leaner with the CAI installed and it may be the case that the ECU retarded timing due to the leaner mixture and warmer intake air. I won't run the car with the AFR as lean as it is so the stock air box is going back on for now. Not sure how much the ECU would adapt the fuelling over time, if it didn't then there would be a case for re-mapping the ECU to bring the AFR back into line with suitable ignition timing and that could reasonably be expected to produce a gain. Once the exhaust testing is done I'll put the CAI on again with all the shielding in place and see how the results look.

good thread..... thats a nice little gain.

This is fascinating. Thanks so much for sharing the process.

Here is the stock run.

I was a tad optumistic I see... i almost guessed 230 but thought I would be flamed.. quite interesting was the deck lid open or closed?

Yes, very interesting results so far I thought. The dyno dynamics will do a crank HP estimate as well but I don't think it is as useful a figure considering it is just an estimate. For what it's worth the DD crank estimate was 292.7HP for the baseline runs, so in this instance it was pretty close to the factory number for a 3.4L. So it looks like a 20% driveline loss for my C2 - I was expecting 15%. Oh and here is a pic of the Corten Miller workshop where the runs were done this morning. Those fans are amazing, they tlierally pull you off balance if you walk near them.

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Deck lid was closed for baseline runs and partially open for the run with the CAI since it was not properly fitted.

Interesting about driveline loss. It's always been Porsche lore that there is less with a 911 because it uses a transaxle rather than a driveshaft and differential. 15% is the number I'd always heard kicked around, too.

I am guessing that a new air filter was used with the new CAI, was a new air filter used for the stock baseline run also or a filter that had been on the car for awhile.

tough for me to imagine 5 hp with just a filter change too...I guess the numbers dont lie but it would be best to install proper and close the deck lid IMO - otherwise its still not apples to apples - the "urban theory" is that the CIA sucks heat out of the engine bay which is what causes the power loss, so with the lid open (even partialy) that was not tested IMO

The CAI issue you describe is real with open designs, like you see bolted on to the neighbour kid's Honda. Most of the aftermarket pieces we would use are complete replacements for the OE piece, so the engine-heated-air concern doesn't apply. FWIW, I would not obsess with the numbers, only with what makes a difference and at what magnitude. Peak HP numbers are for bench racing, and we've all seen guys put dyno charts up here and get beaten to a pulp with pedantry and skepticism. Personally, I'm just interested to see the effects he's having, and delighted to be able to do so with somebody else's money.

+1 Bruce..... +1 ! I am not trying to beat him up, I am thankful and passing an 03' Turbo @ the track in a bone stock 86' with all season tires is proof of what you are saying

I suspect the lean condition was caused by the lack of learning time the ECU had between the runs. If the ECU sees a lean condition it will adjust the fuel trim to compensate. The only concern would be if you had maxed out the fuel trim adjustment range of the ECU and were still running lean. -Shawn

Don't worry Ed I wasn't feeling beaten up...far from it. As I mentioned early in the post, I like to see for myself how things stack up and I don't mind sharing my findings (good or bad). In the process of doing so, I like to point out any factors that I recognise as being relevant (such as the heat shields not being present during the CAI run.) Rennlist is a pretty good resource and I think independant information like this is helpful for comparing with others findings and manufacturers claims. -Shawn, I was talking to the guys that run the dyno shop and they consistently see AFR shifts like that with other cars (WRX & EVOs) when they switch from stock intakes to large bore intakes. I have no idea what sort of learning rate the ECU has to bring the AFR back into line. I think I'd prefer to see the results for the exhaust components before I put the CAI back on. OneFastViking - the stock air filter has about 1500 miles on it, the CAI filter was brand new. Ed - My view is that these results for the CAI are more or less worst case considering the heat shield wasn't in place and the filter was sucking in warmer air (65c) as a result - and the ignition timing may not have been optimal considering the leaner than ideal AFR. Findings like this are what I find useful from having the car on the dyno as now I know what needs attention.

You should hang one of those fans over the roof blowing down the rear window to emulate actual driving conditions. I doubt the CAI had anything to do with the ECU leaning out the motor. What octane fuel were you running? My 3.4 went from 249whp with a CAI (OEM box w/BMC filter) and straight pipes to 282 whp with a GIAC flash, 98 octane, and 3.8 manifolds. Leanest I've seen is 13.0 unfortunately, I'd love to see 13.5 or 14....

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Gordon - A fan in that location would be nice but thats not a setup that is available. As far as the CAI not resulting in the AFR change, I'll have to disagree with you on that one as the CAI was the only thing changed between the runs. I'm no gas/aerodynamics specialist by any means but I suspect the change is related to the different bore size of the intake pipe at that point when compared to the stock intake pipe and/or the location of the MAF sensor. Whatever the cause, the change in AFR was clearly linked to the intake swap. The fuel here is 95RON. Going as lean as 13.5 - 14 seems overly lean to me but I am used to tuning at 12.2 under boost. Cheers,

Optimal AFRs for FI applications are quite different than for NA motors. You can speed up the learning process by clearing the existing/stored trim values. Disconnect the battery and allow it to sit for about five minutes. Then drive for a few days to get the new trim values established and re-test.

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Thanks for the tip on the ECU reset. With respect to NA AFR I would have figured about 13 is optimal rather than 13.5 - 14. Cheers,

I haven't played with my durametric in some time, but can't you force the ecu into "learning" mode with it? But yes.....I would have disconnected the battery, install the CAI, waited 10 minutes, then do 3 runs...with 2-3 minute pauses in between each run. Your 3rd run would be your strongest pull. I'm surprized the shop didn't advise you to do this. Where they short on time? Or do they charge you for dyno RUNS as opposed to dyne TIME? Well, when you get the exhaust put on...simplest thing to do is drive it for a few days and then dyno the car. Post results...and more pics

oh...and I don't really think you are losing 20%. That seems much too high. 1. your car has undoubtedly lost some power over the years to begin with. 2. their crank numbers are estimates...and estimates have variations...so you could very well be losing only 16%

Q: are the dyno run numbers corrected or uncorrect? -td

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There's a small notation on the bottom of the first sheet indicating the SAE correction was applied.

Roger. I see it now - corrected values of 236 and 241. Based on yesterday's weather close to the OP [58F and 26.67 Hg-in, it looks like correction factor was about 1.1. That puts the uncorrected values pretty low! [215HP and 220HP, respectively]. -td

Perhaps I'm missing something, but what conclusion you drawing from the uncorrected results? The whole point of the SAE correction is to attempt to allow comparison to other dynos taken under different atmospheric conditions. -S

Not really a conclusion overall, but on that day, at that time, the HP was pretty low. I get the point of correction. But I also understand actual values. [edit: aka, what's on tap when you leave. Having 220 at your disposal is probably much less than the average 996 owner expects] -td

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true, but not wrong..... just the fact is we hate admitting we dont have it - I dont mind...some do still its enough to push the car alot better than most cars on the road. How many stock cars are Dyno'd ? I bet some are really low compared to what people think they have

Agreed. Horsepower is a poorly understood currency in some circles. The valuable information in a dyno chart is in the shape of that curve, not so much what the peak number is.

Performance wise this 996 doesn't feel any different from other 996's that I've driven - It feels good. I'm hoping the weather holds up so I can take it to the track next Friday and see how it goes there as well. At the end of the day the fun factor with the car comes from how it feels on the road/track. The dyno is just another tool to check things out - of course I can say this now, knowing that there aren't any big HP numbers to get sexed up about I'm sure the most cost effective performance dollars to be invested in this car will be in the suspension department and some refinements in the brakes. SeanMcr6 - in answer to your question about the dyno charging rate it was time based. This is also the reason I only fitted the main part of the CAI and not the heat shield whilst the car was on the dyno. The evening prior to the dyno run I did a practise install of the CAI and I noted fitment issues that would take some time to get right, I didn't have time to sort that out the evening prior and I wasn't prepared to sort that out whilst the car was sitting on the dyno. In hindsight I'm glad I did the partial fitment as the results have given me more to think about (with respect to shielding the intake).