Does an aftermarket exhaust make a difference?
11-06-2007, 07:52 PM
#46
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The muffler on the right is stock and the muffler on the left has had the MK II mod completed.
11-06-2007, 11:01 PM
#47
It is possible to get even a greater difference that you mentioned. I have seen high boost/hp vary by over 50 rwhp (uncorrected) on a Dynojet. That is why you put in temperature and humidity readings into the dyno sofware everytime you run and look at corrected numbers. Despite the raw number differences, the corrected numbers were within 1%. SAE correction standards are applied to compensate for varying climate conditions. My correction factor was 1.04 for my baseline and 1.03 with the intake and exhaust. In my case, if you look at just the raw/uncorrected numbers; the difference is actually greater (at 24 rwhp). On the second dyno it was cooler, but more humid resulting in a slightly lower correction factor.
Being able to compensate for varying climate conditions using correction factors is the reason why a chassis dyno is the most accurate way to measure power variances next to an engine dyno in a climate controlled room. Keep in mind that not everyone inputs climate data and corrects corrections factors when they operate a dyno. Make sure they do it whenever you dyno or the result of the runs will be useless. Feel free to read SAE white papers on dyno calibration and correction standards to understand more about how climate can effect engine performance and is compensated by standardized mathmatical formulas.
One other thing to think about is in a similar thread someone made a comment that they measure changes by using a Gtech or other manually trigger motion sensing box. These devices have no abiltiy to compensate for varying climate conditions and hence provide no accuracy in measurement.
Being able to compensate for varying climate conditions using correction factors is the reason why a chassis dyno is the most accurate way to measure power variances next to an engine dyno in a climate controlled room. Keep in mind that not everyone inputs climate data and corrects corrections factors when they operate a dyno. Make sure they do it whenever you dyno or the result of the runs will be useless. Feel free to read SAE white papers on dyno calibration and correction standards to understand more about how climate can effect engine performance and is compensated by standardized mathmatical formulas.
One other thing to think about is in a similar thread someone made a comment that they measure changes by using a Gtech or other manually trigger motion sensing box. These devices have no abiltiy to compensate for varying climate conditions and hence provide no accuracy in measurement.
11-06-2007, 11:12 PM
#48
I'm no engineer and my dyno knowledge is all secondhand. I'm also aware of the correction factors. But different dynos produce differing results. Also, there are other factors that aren't corrected for and tuners can use to game the system (tranny oil temp, for example). So, I remain a skeptic when it comes to mods and "proven results". If it sounds too good to be true, it probably is...
11-06-2007, 11:34 PM
#49
I generally agree with this, and I think if you have to look that hard for proof, it's probably not worth the trouble. But I think exhaust is different, dyno or no. It's the most tunable part of an engine without opening the motor up, and the component most likely to be deliberately compromised by the manufacturer for marketing or compliance reasons. A good exhaust lets the engine come closer to making the power it was built with. If you understand how exhausts work, and I think you probably do, you'd have a hard time arguing with that statement. Worth the money? That's subjective. But gains, yes.
11-07-2007, 09:26 AM
#50
Now, about this engineer in Zuffenhausen. Can I pick any engineer I want to tell it to? Does he have to be able to speak English, or work for Porsche? Could he be, like, a train engineer? Or a sanitation engineer? Can we have beer after he laughs in my face? Could I use this as a standup routine in a Zuffenhausen bar on open mike night? Would I win?
11-07-2007, 10:25 AM
#51
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There definitly is some power to be had. I just took off my bypass pipes and went back to stock. The car has a wee bit more grunt down low (who the f**k cares about this), and has less ***** in the mid/high RPM.
11-07-2007, 01:58 PM
#54
Cap'n Insane the Engorged
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PSE audio samples:
Sample One
Sample Two
Not so much performance gains, but the sound makes the car feel faster, plus it gives a nice aural indicator of when to blip and shift.
PSE audio samples:
Sample One
Sample Two
Not so much performance gains, but the sound makes the car feel faster, plus it gives a nice aural indicator of when to blip and shift.
11-08-2007, 03:11 PM
#55
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"Curb weight.....3149 lb"
http://www.caranddriver.com/longroad...era-page4.html
And the Tip weighs ~100 lbs more, plus the driver, fuel, fluids ,etc, easily equals ~3,400 lbs.
Let me point out the obvious: how accurate can that gizmo be (certainly not the 100th of a second)?, same route?, same conditions (very unlikely, that's why chassis dyno numbers are so suspect and easy to manipulate)?
If you're happy with it, that's all that matters. But, the gains you claim are highly suspect given those mods (a turbo or sc would be a different story). Common sense says that you'd need to a big jump in power to lower your 0-60 time by that margin and there's no way those mods are going to get you there.
http://www.caranddriver.com/longroad...era-page4.html
And the Tip weighs ~100 lbs more, plus the driver, fuel, fluids ,etc, easily equals ~3,400 lbs.
Let me point out the obvious: how accurate can that gizmo be (certainly not the 100th of a second)?, same route?, same conditions (very unlikely, that's why chassis dyno numbers are so suspect and easy to manipulate)?
If you're happy with it, that's all that matters. But, the gains you claim are highly suspect given those mods (a turbo or sc would be a different story). Common sense says that you'd need to a big jump in power to lower your 0-60 time by that margin and there's no way those mods are going to get you there.
My car weighs 3084lbs and 3259lbs with my weight 175lbs (lightweight 02 5 spokes F/R 8”/10”, PS2 235/265, no floor mats except for 1 weathertech driver mat at approximately 5lbs, a hair over 1/4 tank of gas, a stereo amp at approximately 10lbs, heavier GT3 sway bars and TRG drop links, engine protection plate, no spare tire, no toolkit/jack, JICs which weigh the same as stock from my measurements, and the rear strut brace).
The car is a 99 996 6spd, w/lsd, rear wiper, heated seats, and tinted windows.
11-08-2007, 06:31 PM
#56
11-08-2007, 06:43 PM
#57
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Yeah I don't understand why people think performance exhausts are nothing but sound. I think exhausts like the Fabspeeds, GHL, and others would certainly boost hp a bit. I seriously doubt it's 22whp (or bhp for that matter), but I think ~10hp is certainly possible.
11-09-2007, 12:01 AM
#58
