how much does the stock exhaust limits HP/Tq after camshaft install???

3625 Views 60 Replies 20 Participants Last post by HisMajesty, Oct 22, 2003

coldbanana1

Discussion Starter · Feb 12, 2002

I've got an MK4 vr6...I've got a set of cams similar to DSR 256...with a bit more duration....and I've got a GIAC chip...but I'm still running a stock exhaust...Lately I've been booting my car on the highway and find that at rpm above 4200rpm...3/4 throttle compared to full throttle yields very very little difference in performance....I was wondering if my stock exhaust may contribute to a high loss in expected performance of the camshafts with the stock exhaust at high RPM...I've also found that my midrange is exceptionally strong...but the pull doesn't increase...yet stay constant after 4200rpm smoothly until redline....

[Modified by coldbanana1, 6:37 AM 2-12-2002]

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coldbanana1

Discussion Starter · #2 · Feb 12, 2002

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (coldbanana1)

nobody knows?

climbingcue

· #3 · Feb 12, 2002

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (coldbanana1)

Do a before and after exhaust dyno...... But a high flow exhaust is key to make the most out of the cams.............. I would say it is hurting you for sure, but I can not tell you how many hp...........
Good luck

M this 1!

· #4 · Feb 13, 2002

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (climbingcue)

once you add cams and a chip, you now have more fuel and more air coming in which gives you the increase in power. well you also have more exhaust gases now and this is when a high flow exhaust will show increases. the more important question will be which one and what sound?

maxxam

· #5 · Oct 9, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (M this 1!)

What is the diameter of the exhuast tubing on a stock MK4 VR6?
Thanks,
Max

VR-Slow

· #6 · Oct 9, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (maxxam)

2.25", but you get the best gains on a vr with a highflow 2.25" exhaust compaired to a 2.5"

maxxam

· #7 · Oct 9, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (VR-Slow)

Thanks for the quick reply. Mine has only 2 inch exhuast, I have a VR swapped into a 16V and haven't changed the exhuast yet. I guess it's time to shop around for a new exhuast system http://****************.com/smile/emthup.gif

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orangecrush1234

· #8 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (maxxam)

so should i go with the 70mm jettex on a n/a motor or 2.5 techtonics i also have the 264 cams with remus can with stock 2.25 pipng no resinator

http://****************.com/smile/emthup.gif

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2

need_a_VR6

· #9 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (orangecrush1234)

I'd do the TT exhaust, just because it's known to work.
For refrence I picked up about .2s in the 1/4 going from a 60mm Supersprint to a 2.5TT/Borla setup.

VR-Slow

· #10 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (need_a_VR6)

magnaflow. i have a TT exhaust. didn't help as much as a magnaflow.

need_a_VR6

· #11 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (VR-Slow)

Do you have track and or dyno numbers to back that up? Honestly a 2.25 is a step in the wrong direction.

FatSean

· #12 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (need_a_VR6)

Hey Bill, I remember at that dyno day in CT way back your Schrick268/NeuspeedExhuast car only got like 1-2hp on my Kent264/StockExhaust. Dunno what a 2.5" would do tho.

VR-Slow

· #13 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (need_a_VR6)

Quote, originally posted by need_a_VR6 »

Do you have track and or dyno numbers to back that up? Honestly a 2.25 is a step in the wrong direction.

yep. i'll post em when i find them. i know with a magnaflow exhaust you get 11hp gain over stock. and that is 2.25" on vr's and 2.slows

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VR-Slow

· #14 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (VR-Slow)

Please keep in mind that the TT exhaust was tested on a car that started with more hp factory than the magnaflow car. and as you can see from the charts you get the same if not better gains from a 2.25" exhaust than a 2.5". This is just my opinion from charts and the mods i have done to my car and to others.
Magnaflow 2.25" 11+ hp gain

TT 2.5" about 9 or 10 hp gain

As for track times, I need to find some tickets that I have away somewhere at my house. I'll post those when I find em.

Modified by VR-Slow at 1:21 PM 10-10-2003

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need_a_VR6

· #15 · Oct 10, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (VR-Slow)

Well that's two different cars on two different dynos. I can see that the 2.25 is better then stock as it's got better mufflers. What I can't see is the 2.25 being better then the 2.5". There's just no way.
My car from 60mm - 2.5 - .2s
Billy's car from 2.25 Magnaflow to 2.5" TT - .2s
There's no fluke.

5.0 eater

· #16 · Oct 11, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (coldbanana1)

If you dont like loud than don't do the TT. It sounds awesome but has way to much drone.
Lets just say that after I took my TT 2.5" W/Borla off and put my stock one back on, the car was a little better on the bottom but I definitely could not feel the cams as much on the top end. What was suprising was that when I got the TDI Midpipe (only $69 CDN) The top end came back dramatically. I can't say for sure if it pulls as hard as with the TT (I never Dyno'ed with either) but if it dosen't than, The Butt Dyno can't tell the difference. If you want a little deeper tone with almost stock cabin noise levels and a noticable gain on a VR6, with the regular bolt-ons (Cams, GIAC, Modified Airbox or CAI) the TDI Midpipe is the best mod you can do dollar for dollar in my opinion.
I was pleasantly suprised since I did it for sound and not power. So remove your resanator and the stock system flows really well.
You choose drone for $850 to $900 CDN or no drone and very similar subjective gains for $69 CDN.

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5.0 eater

· #17 · Oct 11, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (need_a_VR6)

You guys do realize that the post starter was talking about a MKIV which has a much different exhaust than either of your cars.
Maybe there were more gains to be ahd with the Older systems.
Neither the TT or Supersprint that I had made much of a difference over my latest setup, stock with TDI midpipe.
I've driven my car back to back with each of the systems and right now with my mods the TDI midpipe was my best gain for the buck.

DubinBuffalo

· #18 · Oct 11, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (5.0 eater)

I don't know how it is on the MK4 VR6's but I am running a stock exhaust now with a SC and have no complaints at all. From what I understand, the VR exhaust is pretty free flowing from the factory, I assume it would be the same free flowing nature for a MK4

need_a_VR6

· #19 · Oct 11, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (DubinBuffalo)

The stock Mk3 muffler isn't very free flowing. Ever look into the inlet? Yeah restriction right there.
Listen to whomever you want about the subject. Just remember who's going fast and what they're using.

Dansk Ventoe

· #20 · Oct 12, 2003

Re: how much does the stock exhaust limits HP/Tq after camshaft install??? (VR-Slow)

VR-Slow said:
Magnaflow 2.25" 11+ hp gain

QUOTE]
Man that baseline is weak. I don't see any reason to stay with a 2.25 when you can get the 2.5 which is proven to make power. If the magnaflow would put more than a couple hp down than a healthy stock motor I might be convinced otherwise.

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