How can a chassis dyno machine know the drive train loss on a car? I started a thread to find the drive train loss through a Tiptronic trans Boxster.

http://986forum.com/forums/performance-technical-chat/56594-curious-about-hp-loss-through-drivetrain.html

Only person to give out any real numbers was Jake Raby, but it was for manual cars.

So if Jake Raby is seeing a 4% swing on manuals, how is a chassis dyno machine going to know how to accurately calculate drive train loss?

Can you answer that for me? What's the drive train loss on a Tip trans car?

I remember seeing this and being surprised. I've got the same setup, plus a bit more and dynoed at 244rwhp.
IMHO, 300 FWHP is about the best you'll get from bolt-ons with the 3.2.
I do not think the original poster's question is possible without other work.

Clue me in what you mean by FWHP? Never mind flywheel horse power. I always thought that was called bhp?

Worse case scenario of your car having a 22% drive train loss (per Jake's post), you have 297.68bhp, that's a 47.68hp increase. Your car has a 7.2 dme, my car has a 7.8 dme, might be some benefit there? The engine are a bit different unless you put a 2003 or newer engine in your car, your car from factory had 250bhp, mine has 258bhp.

That's my dyno plot and mods listed further above. I have several dunks of various kids on my cars. The one above showing 272 is my 550 so has 987 airbox already and is running 100 cell cats and manifolds already. It also has an indeed rive pulley. You are dreaming d you think you can get significantly over 300 from basic mods.

I also have one chart showing all the different plots for the different mods for my 2000 S.

When I get a chance I'll be only too happy to show the plots for both my cars and the mods done. Kram - you've got your wires crossed on my plots and mods above and have a plot for one car with mods for another.

Is that plot showing drive train loss?

Are you also running the stock intake from the 987 air box to the motor? So no larger intake piping, no larger TB, less effective Distribution T and no tune?

you can add a correction factor into a dyno; someone could have easily modified those dyno results with a 1.15 or 1.2 correction factor so that it was reading high. as was previously stated, the only real information you can get from a dyno is change in hp, not absolute numbers. and in all the tuning i have seen of boxsters, i have yet to see anyone bolt on a 50 hp increase. i have seen people brag of 300 hp, but no 50 hp increase. that's why everyone always wants before and after numbers, because absolute numbers mean nothing when it comes to dynos.

The dynos that show flywheel HP gathered at the rear wheels have always been a joke to me. The drivetrain losses are calculated through a wizard thats no where near accurate for the drivetrain of a Porsche. On top of that, the ones I've seen before allow the user to put what ever figure they want in for a drivetrain loss and the software moves the curve. Its a real good way to cheat.

Numbers gathered at the rear wheels should always be just that. They should not be converted to some wild guess drivetrain loss correction.

If you want flywheel HP numbers, gain those from an engine dyno.

The quickest way to slow a car down is to use a dyno to gather the wrong data, for the wrong reasons.

Jake do you have any data on drivetrain loss with a Tiptronic?

Jake, I'm also curious, when you do a engine dyno, do you have the air intake and exhaust system installed on the engine that's going to be on the car the engine is going into, when you dyno the engine?


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The boxster was restricted coming out of the factory. It has a horrible designed header/exhaust combo. Fabspeed claims Porsche didn't want to showup the 996 guys. Here is actual dyno video of boxster mods.
https://www.youtube.com/watch?v=WN_h9juITLk

Yes I have a ton of tiptronic data, my chassis dyno has over 8,000 dyno runs saved, every car that comes and goes from here gets an evaluation.

With the engine dyno we can outfit with any intake or exhaust, BUT due to the work that goes into firing an M96 on the engine dyno, we only use it for developmental work.

Customer's engines are never tested on this dyno, and sometimes an engine stays bolted up for 3-4 months at a time as we optimize the combination that we are shooting for.

Disagree.

I have used the stock exhaust system from a Boxster to make over 300RWHP in the past. The Boxster engine was ripped with intake ports, not seeing variorum plus till 2007, and through the intake system as well as camshaft profiles.

We can increase Boxster performance way more than 996 performance at the same displacement points. 90% of everything I build gets stock exhaust, and keep in mind that NONE of them are stock displacement.

Yes, but your making your hp in motor building and internals. I'll take an aftermarket header, muffler, delete cat system any day over the stock pieces.

Here is a consolidated graph showing a variety of mods. There is a baseline plot and then each plot shows the compound effect of the mods. Don't focus on the ultimate number instead look at the shape and gradient of the plots.

The car in question was my 2000 S. UK car, so only 2 cats. Baseline is at approx 60k miles and the other runs are between 60-70k. All runs done on the same dyno. The dyno operator has no axe to grind. He does not tune or modify cars as a business. I have never bought anything from him, not told him what mods have been done to the car. This is the UK remember so the weather and temperature is pretty much the same all the time!

http://986forum.com/forums/performance-technical-chat/47555-tuned-modified-2000-boxster-s.html

http://i43.tinypic.com/ka3dbo.jpg

The plot below is for my 2004 550 Anni. Again a UK car so no cats in manifolds/headers. Same dyno as above. Approx 105 miles. This car has a K&N filter (987 airbox as standard), ebay stainless manifolds/headers, Carnewal exhaust (internal modification only), 100 cell cats (ceramic I think). It also has a 4" underdrive pulley but I doubt that adds much if anything.

http://i61.tinypic.com/20uxu00.jpg

This estimated flywheel figure is 272bhp and the plot for wheel horsepower shows 223bhp which is consistent with Jake Raby's above data of 18-22% drive train losses.

Somebody correct me if I am wrong but the AFR here is pretty much there or thereabouts so a "tune" in my opinion is not going to see any significant gains, certainly not to trouble 300bhp.

On the same dyno on the same day in the same conditions my car made 10bhp more than 2 other standard 550 Anniversary cars.

I used to think optimistically that if I had a strong base standard car to start with that I might crack 300bhp but it's just not going to happen at the same rpm. People often compare to a BMW M3 but forget that the limiter and where the power is made is much higher. If you extrapolated my 272 plot from just under 6500rpm on the same gradient and by another 1500rpm to where the M3 makes its power then the peak number won't be that much different.

I have done the throttle body mod on my previous car (above), and based on the gains there, you can see they are not huge, that mod will give me a bit more but not 10s of bhp.

There is a chap here in the UK I know of who has an early 3.2 987 and has experimented with various bolt-on mods too and has not quite cracked 300bhp either. That cars starts out with 280bhp ish as standard.

There is another chap who is a tuner and engine builder by trade, and a quite distinguished one at that, but who is new to Porsches. He saw a good gain on his rebuilt 2.7 by a slight increase in compression from a head skim.

I'm no trading expert but just an enthusiast who has wasted many £££s and hours mucking about with a toy car. Sure i could spend more money on supposedly better branded items and maybe make a little more power but that is not what I am trying to do. I am trying to experiment on a deliberately small budget. There are lots of butt dyno claims but the only real test is as above. I also felt that when I had done the manifolds/headers and exhauston my first Boxster that the butt dyno gave me a lot more than the real dyno.