Dyno run - 987.2 S - Page 2 - Boxster/Cayman - PistonHeads UK

Hi All Just had a dyno run completed just out of interest and to make sure everything is running well. 09 Cayman S with 43,000 miles and totally stock. I have run through a can of BG44K and a bottle of Redline Si recently as well as adding Archoil 9300 nano ceramic. The result... 336bhp. Just wanted to share this as I thought folks might be interested I'm happy with the result. Thanks. James.

Shock news: dynos tend to over-read. It might be running at 320, but over 330 is extraordinarily unlikely.

My 996 GT3 ran twice on a dyno - about 4 weeks apart. First read 354 bhp (should have been 380) which got me worried. Second read 401bhp! Average suggest it was producing what it should, but my experience suggests you can take a one off reading with a pinch of salt (unless you do mods and use same machine to re-check so comparing like with like.

It was Noble Motorsport at Chesterfield that I used, supposed to be one of the most accurate around. My personal opinion is that the Porsche factory figures err on the side of caution. The main reason for getting it done was to understand if there was anything untoward happening I didn't really care if it chucked out 315 or 335bhp. Lambda was bang on 1.0 on partial throttle and dropped to circa 0.88 at full throttle/higher revs. Interesting little thread from a while back though at the same place: http://www.planet-9.com/porsche-dyno-charts/33778-... Cost £45 if anyone else in the vicinity has an enquiring mind like myself

anonymous said: [redacted] Not from me but another Google result, you can tell it's raining and I'm bored Like I said, it was just to get a rough idea on how its performing and for any glaring issues. 'They actually make an attempt to measure the losses by doing a "coast-down" at the end of each power run. This is by no means a 100% accurate method (you can't possibly accurately measure losses accurately) but at least it's an attempt to measure them, unlike others who just quote a percentage which is totally unrealistic. If anything, the coast down losses are actually an OVER estimation of the losses, so you can pretty much be sure that the figures quoted by Nobles are a touch pessimistic.'

What are your figures at the wheels?

NJH said: What are your figures at the wheels? Realised that I didn't pick that printout up from them. I'll get them to email it on Monday.

ORD said: Shock news: dynos tend to over-read. It might be running at 320, but over 330 is extraordinarily unlikely. I disagree, 336bhp is only 5% over the advertised, 320bhp, output. This is within factory tolerances. It was a cold day (they usually have the rollers down but had them open today), running Tesco 99 with the Redline si-1 in the tank plus it should have super slippery internals due to the Archoil 9300. Brand new air filter, very recent engine and transmission oil change, cleaned MAF and throttle body. With all this combined is it totally unfeasible to achieve 336bhp on a healthy pampered car?

finestjammy said: ORD said: Shock news: dynos tend to over-read. It might be running at 320, but over 330 is extraordinarily unlikely. I disagree, 336bhp is only 5% over the advertised, 320bhp, output. This is within factory tolerances. It was a cold day (they usually have the rollers down but had them open today), running Tesco 99 with the Redline si-1 in the tank plus it should have super slippery internals due to the Archoil 9300. Brand new air filter, very recent engine and transmission oil change, cleaned MAF and throttle body. With all this combined is it totally unfeasible to achieve 336bhp on a healthy pampered car? I think its most likely a high reading from the dyno given its a standard car. I've had lots of cars on the dyno and done plenty of dyno days and reading high is pretty normal on even highly respected dyno's however reading high is preferable to low since it probably indicates your car is making the quoted power. As far as I'm concerned its a good result to show around factory power!

AntiLagGC8 said: I think its most likely a high reading from the dyno given its a standard car. I've had lots of cars on the dyno and done plenty of dyno days and reading high is pretty normal on even highly respected dyno's however reading high is preferable to low since it probably indicates your car is making the quoted power. As far as I'm concerned its a good result to show around factory power! Thanks for the response, useful to have the view from someone who's attended numerous dyno days. Agreed, I'm not bothered about pub bragging rights, just interested that it, hopefully, gives an indication that everything is running as it should be.

finestjammy said: Thanks for the response, useful to have the view from someone who's attended numerous dyno days. Agreed, I'm not bothered about pub bragging rights, just interested that it, hopefully, gives an indication that everything is running as it should be. There is a correction factor to compensate for differences in air pressure, temperature, and humidity. I'd check that has been applied. NA engines vary a lot - to the extent that in a race qualifying session teams will wait for cloud cover - knowing that will boost performance significantly.

Don't Porsche quote power levels at a higher altitude. That way when you come back down towards sea level, it would make sense to be producing more power. Also their 0-60 times are super conservative when compared to road tests in car & driver and other online mags that do proper tests.

jayxx83 said: Don't Porsche quote power levels at a higher altitude. That way when you come back down towards sea level, it would make sense to be producing more power. Also their 0-60 times are super conservative when compared to road tests in car & driver and other online mags that do proper tests. I wasn't aware of it. DIN figures are quoted at a fixed set of atmospheric conditions - and at sea level I'd be pretty sure. If I remember rightly there is a 5% tolerance - ie any particular car should be within 5% of the quoted output figure. As you say their acceleration figures tend to be conservative - but it's more difficult to judge whether their power figures are.

I recall various Porsche bods saying that they plump for the bottom end of what they see, so your Pork may well be producing a little bit more power. I think the video about the GT4 included a quotation to that effect - Porsche horses are particular strong, or something like that. 0-60 times are way down on what other people manage, that's true. My 987.2 S was a lot more like 4.5 than whatever Porsche quoted.

Agreed. The thing is its almost impossible to extrapolate from the measured power at the wheels to power at the flywheel on these dynos to any sort of accuracy. The coast down measurement is a nonsense as a vehicle driveline saps power when under load from the engine but coast down by definition is under no load, there are some long threads and discussions on this subject on the net, many of the best on other parts of PH. One last thing on this subject, the so called "dynos of truth" or what people think are accurate chassis dynos are only ones where the flywheel guestimation either produces a lower number or it happens to fit with a certain manufacturers numbers. This is what made me laugh about the old Weltmeister set up at Silverstone, they used the same rolling road equipment as many other places that get roundly criticised but Weltmeister didn't because you could strap a stock Porsche on their rollers and get stock horsepower numbers. Eventually you realise its all a load of old cobblers.

ORD said: I recall various Porsche bods saying that they plump for the bottom end of what they see, so your Pork may well be producing a little bit more power. Isn't this the same thing that most car owners and sometimes manufacturers say? I'm sure we've all heard this many times before from owners of various brands. Porsche manufacture is usually very good (comparatively) so I'd expect the car to be very close to its stated power figures. What's is always less accurate are dyno's because of the number of variables that can affect a run, they are very sensitive to everything being perfect for a reasonably approximation of power. My car's power has varied by 22bhp on the last 3 dyno runs (the car hasn't had anything changed). I think 0-60 and 1/4 times are probably more worthy as a measurement of performance as long as the driver is capable of getting the car off the line and its properly timed (not someone timing from in the car). Edited by AntiLagGC8 on Sunday 10th January 13:35

This is what makes me laugh when people proclaim an X bhp increase from an air filter or exhaust mod they may have done. They look up the book number and compare to what they have just shown on the dyno or what the seller states on their marketing material. For my own car, I mod and use the same dyno so there is some comparative basis. You can get a baseline and dyno each time you make a mod. Ok, this is not 110% accurate all the time but without spending all your money on the dyno time then it is good enough for me. Another thing I find interesting is the "dyno day". This gives you some context to how the numbers look with other cars, even better if there are several of the same type.

Just another point - why are you using additives in your oil/fuel? I'm not an expert on this topic but I've read plenty of accounts from people who are, and none of them recommend sticking any of these snake oil type products in your engine! Stick to quality oil (Mobil 1) with regular changes, and high octane fuel, and that's all you need to do.

S1MMA said: Just another point - why are you using additives in your oil/fuel? I'm not an expert on this topic but I've read plenty of accounts from people who are, and none of them recommend sticking any of these snake oil type products in your engine! Stick to quality oil (Mobil 1) with regular changes, and high octane fuel, and that's all you need to do. The fuel additive was to make sure the whole system was clean. Redline had a high PEA content which will clean the injectors, lines, combustion chamber etc. The Archoil 9300 has lots of research to back up its claims, it's nothing like the old Slick 50 PTFE type additives that clogged filters etc. This car was new to me from 39,000 miles so I'm not entirely sure how it has been used and maintained other than the Porache service stamps, which are too far apart in my opinion. If I'd had it from new I probably wouldn't have bothered with the oil additive, but I am sold on a regular maintenance dose of Millers Petrol Power Ecomax as a detergency additive to keep the injectors healthy. As with PDK vs manual you'll get very split opinion on additives with some saying they add 100bhp and others with the opinion they'll grenade your engine PS My MPG did seem to improve a little after the use of Archoil...but of course this could be because of other factors.

edc said: For my own car, I mod and use the same dyno so there is some comparative basis. You can get a baseline and dyno each time you make a mod. Ok, this is not 110% accurate all the time but without spending all your money on the dyno time then it is good enough for me. Another thing I find interesting is the "dyno day". This gives you some context to how the numbers look with other cars, even better if there are several of the same type. Here is a tip though if you want to win at dyno day. Pump your tyres up to their maximum safe running pressure. Likewise for when places do tuning, they do the base run on the car with cold tyres then after 20 minutes doing lots of pulls on the dyno the tyres have also got hotter, increasing pressure in them and likely making the dyno read a few hp more than "it should" due to the drop in rolling resistance. This alone could easily be enough to account for a small gain claimed from the stuff people do when tuning N/A cars.

NJH said: Here is a tip though if you want to win at dyno day. Pump your tyres up to their maximum safe running pressure. Likewise for when places do tuning, they do the base run on the car with cold tyres then after 20 minutes doing lots of pulls on the dyno the tyres have also got hotter, increasing pressure in them and likely making the dyno read a few hp more than "it should" due to the drop in rolling resistance. This alone could easily be enough to account for a small gain claimed from the stuff people do when tuning N/A cars. Brill, I like it. I did get slightly concerned when he said he reached 155mph, that's just when I remembered I had the winter tyres fitted rated to 149mph, whoops

After mod dyno sessions are only a handful of runs max so pressure is not so much an issue. When I had my last car mapped, different dyno to my local, I had many runs and they checked tyre temp before and during each run to ensure tyre temp was consistent. How tightly you strap the car down can also have an influence.