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I need some SERIOUS thoughts.
Posted 13 February 2005 - 09:18 PM
I do have a change. The exhaust. Its still got the TWE header/DP and stock turbo....BUT...instead of having a 2.5" back with a glass pack, its now got a 2.5 inch 3 way cat, that after it reduces down to 2.25 and then down to 2.0 inches thru a 2.0 inch glass pack at the end.
And im using a different air filter.
Are these two changes going to seriously change the actual HP output? I didnt feel anytohng on the 'butt dyno'
Seriously...what does USMB think?
Posted 13 February 2005 - 09:27 PM
Posted 13 February 2005 - 10:12 PM
when you dont have cams, or internal mods, your increased boost, headers, air cleaner, and exhaust system are the main mods, so... i think exhaust and air cleaner would have alot to do with dyno numbers, and more inprotantly, tuning. stoich!
Posted 14 February 2005 - 12:35 AM
Posted 14 February 2005 - 03:42 AM
if you want to be picky, i think kevin might have some good dyno numbers and posts comparing 2", 2.25" and 2.5" exhaust diameters on an XT6. being NA maybe that's useless. going from 2.5" to 2" is a 36% decrease in cross sectional area. i think 2.5" or larger (and kevin i think agrees) is too big for an otherwise stock XT6, a noticeable difference from 2" and 2.25" exhaust. again this is NA, but we could notice the difference, not a very big difference but something. i'm a turbovirgin but that seems significant from what i've read about turbo's. in the end it probably moves the power band more than actually making the highest values that much different. that's what i don't like about the larger exhaust sizes on the XT6, loose too much low end for what i want.
Posted 14 February 2005 - 03:50 AM
If you have a cone air filter or a cut airbox, yes.
If you have a totally stock intake system, I belive the restriction of the intake will help to keep down any gains from the exhaust since its not fully modified (like a 3 inch turbo back or something...)
I found that glasspacking one of my turbowagons made no difference at all. (other than a bit of noise when I let off the gas)
A K&N Filter on my wagon back when it had a hitachi carb made a bigger difference! So I think these cars are more restricted on the intake side.
Like I said, its my opinion, not a proven fact.
Posted 14 February 2005 - 04:37 AM
Using a chassis dyno at all is something of a crapshoot as far as getting usable results goes. Results are extremely dependent on operator skill as well as calibration of the dyno and, of course, the dyno's measurement method. I've actually seen a study where a lightly modded WRX only dyno'd out at about 98 whp. It turns out that a 4/AWD dyno loses something like 4 times as much power compared to a 2WD dyno do to heat and limited traction on the steel rollers (tire slippage). I suspect that you'll actually see a significant reduction in reported horsepower. I think your new exhaust will tend to offset that a small bit, but in the end, you'll see less power.
Posted 14 February 2005 - 06:43 AM
There was no slippage. The rollers are deisgned to not loose traction (aka they have stickey surfaces)
The Dyno Jet that I went to at first was brand new and freshly calibrated...it was 100% accurate on the numbers that other cars pulled in stock form.
This mustang experiment is to see just 'far off' the mustang is as compared to the dyno jet.
My intake remins almost the same...but I went from a mushroom-foam type filter to a regular cone-K&N style filter. ANd I cant put the bigger glass pack exhaust back on....i hacked it into peices to make the current one.
Posted 14 February 2005 - 08:01 AM
Posted 14 February 2005 - 09:56 AM
YOu could go to that same dyno you went to before now and come up with different values. Heck you could go back to that same dyno with the exact same setup and I bet your numbers would be different.
For it to have an ounce of validity you'd have to keep everything the same.
Posted 14 February 2005 - 01:18 PM
Also, why the reducing diameter? You will be losing power through most of the RPM range, I would estimate. Hot gasses tend to want to expand. If you reduce the diameter, you are reducing the volume available for expansion (creating backpressure). I would say the losses would be higher at the top end, though. most likely under 2000 you will not lose much, but over 4500 or so you would see a drop.
Posted 14 February 2005 - 01:34 PM
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