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      09-07-2010, 12:16 PM   #1
J08M3
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Car actually seems faster w/ OEM xpipe and cats

So as many of you know I've had about 7 different systems / combinations of exhaust systems on my car. Now, hopefully my final and most recent combination is only an Akrapovic slip-on. I'm back to stock cats and xpipe, after just having the system combined with Fabspeed xpipe and HFC's. To be honest the car really seems to be faster now and must be making a little more torque in the lower RPMs (where on the street 95% of my time is spent). I say it seems faster cause I notice traction control kicking in all the time now as I accelerate cause the rear tires are trying to spin. This didn't happen nearly as often with aftermarket xpipe on. It's not due to loss of tread on rear tires as they are fairly new too. I'm thinking the full systems only really help you out at the very high RPM ranges and slow you down in the lower ones.
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      09-07-2010, 01:22 PM   #2
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No offense, but that's why people dyno their cars instead of relying on what they feel. As you know, back to back dynos with the stock system vs. HFCs/x-pipe show increase or equal performance across the entire range, so I don't see how what you're saying would be possible. Unless all these dynos are cooked. Only exception is the untuned full Akra which shows a slight loss of power in a small part of the band.

Tires do require a break-in period FYI, so they will actually provide less traction when new...so that could be part of it.
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      09-07-2010, 02:43 PM   #3
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Quote:
Originally Posted by Singletrack View Post
No offense, but that's why people dyno their cars instead of relying on what they feel. As you know, back to back dynos with the stock system vs. HFCs/x-pipe show increase or equal performance across the entire range, so I don't see how what you're saying would be possible. Unless all these dynos are cooked. Only exception is the untuned full Akra which shows a slight loss of power in a small part of the band.

Tires do require a break-in period FYI, so they will actually provide less traction when new...so that could be part of it.
No offense taken, and I'm the last one to believe in a "butt dyno". But the tires aren't brand new so they are broken in. I also know all dynos show otherwise. But I can tell you from behind the wheel it does seem to have a little more in it.
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      09-07-2010, 02:46 PM   #4
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Mine doesnt feel slower or faster, but after removing the HFC the car feels MUCH smoother in acceleration.

All in my head? Perhaps but ill take it.
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      09-07-2010, 02:49 PM   #5
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All in my head? Perhaps but ill take it.
Me too
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      09-07-2010, 06:14 PM   #6
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Quote:
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No offense, but that's why people dyno their cars instead of relying on what they feel.
You'd be hard pressed to find dynos that start at less than 4K rpm, so OP has a point. Besides, it's a well known fact you're going to give up low-end torque for top-end HP with a full system; the only question left is how much. And yes, most folks know this, so it shouldn't come as a surprise . Good day.
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      09-07-2010, 06:50 PM   #7
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Besides, it's a well known fact you're going to give up low-end torque for top-end HP with a full system
this, +1.
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      09-07-2010, 07:09 PM   #8
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Quote:
Originally Posted by elp_jc View Post
You'd be hard pressed to find dynos that start at less than 4K rpm, so OP has a point. Besides, it's a well known fact you're going to give up low-end torque for top-end HP with a full system; the only question left is how much. And yes, most folks know this, so it shouldn't come as a surprise . Good day.
There are plenty of dynos that start at around the 2k range. The full systems *without cats* show a loss at around 2500. I've never seen a HFC system do worse than stock down low - equal yes, but not worse. If you have a graph that shows this, then I'd be interested to see it.
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      09-07-2010, 07:27 PM   #9
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Quote:
Originally Posted by Crazy Bimmer View Post
Mine doesnt feel slower or faster, but after removing the HFC the car feels MUCH smoother in acceleration.

All in my head? Perhaps but ill take it.
Interesting....why'd you remove your HFC?
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      09-07-2010, 07:45 PM   #10
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Interesting....why'd you remove your HFC?
+1
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      09-07-2010, 07:52 PM   #11
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Well my car is street driven so I don't spend as much time at top of the rpm band as the lower rpms so the little extra torque down lower is better for me than the extra few hp up top. Plus I now pass inspection with no issues.
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      09-07-2010, 08:00 PM   #12
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Quote:
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Interesting....why'd you remove your HFC?

Was a tad louder than I wanted for my daily driver.

Also didnt care for the check engine light then kept coming and going.

Guess im just becoming a wussy the older i get.
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      09-07-2010, 08:39 PM   #13
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Quote:
Originally Posted by Crazy Bimmer View Post
Was a tad louder than I wanted for my daily driver.

Also didnt care for the check engine light then kept coming and going.

Guess im just becoming a wussy the older i get.
Ha. I hear ya. I'm in the same boat. I guess we do mature as we get older...LOL.

What exhaust you running now?
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      09-07-2010, 08:40 PM   #14
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Eisenmann sport but kept the fabspeed xpipe with stock cats.
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      09-07-2010, 09:01 PM   #15
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With very little restriction in the exhaust system, you will definitely lose some low end torque. Overall horsepower might shows gains but torque is a different story. It's difficult to find the combination that not only will increase hp but torque as well.

I hope the akrapovic full system does so because they cost a pair of kidneys.
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      09-07-2010, 10:14 PM   #16
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With very little restriction in the exhaust system, you will definitely lose some low end torque. Overall horsepower might shows gains but torque is a different story. It's difficult to find the combination that not only will increase hp but torque as well.
This statement is confusing to me. If you lose low end torque, you are losing low-end HP also.

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I hope the akrapovic full system does so because they cost a pair of kidneys.
It does - with the exception of a small portion of the rev range down low. The stock programing can't adjust properly in this area, but ESS and PC now have tunes out to address this.
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      09-07-2010, 11:08 PM   #17
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agreed, have the full akra, ess tune and 3.45 dinan diff. 295 rear tires and can easily lose traction in 3rd...love the setup
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      09-08-2010, 04:54 AM   #18
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Quote:
Originally Posted by J08M3 View Post
So as many of you know I've had about 7 different systems / combinations of exhaust systems on my car. Now, hopefully my final and most recent combination is only an Akrapovic slip-on. I'm back to stock cats and xpipe, after just having the system combined with Fabspeed xpipe and HFC's. To be honest the car really seems to be faster now and must be making a little more torque in the lower RPMs (where on the street 95% of my time is spent). I say it seems faster cause I notice traction control kicking in all the time now as I accelerate cause the rear tires are trying to spin. This didn't happen nearly as often with aftermarket xpipe on. It's not due to loss of tread on rear tires as they are fairly new too. I'm thinking the full systems only really help you out at the very high RPM ranges and slow you down in the lower ones.
I have to agree with this. I have gone back to stock and am surprised how good it feels now
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      09-08-2010, 11:09 AM   #19
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are you guys on stock ecu or flashed?
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      09-08-2010, 11:23 AM   #20
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Stock, never had a tune. Didnt want to mess with it.
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      09-08-2010, 11:37 AM   #21
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are you guys on stock ecu or flashed?
stock, wouldn't dare mess with the ECU for a couple of HP. and unless I was racing stop light to stop light that couple HP means very little. wouldn't risk voiding my warranty over that or want to deal with shipping ECU somewhere and then having to worry about doing it again if I should need some dealer updates that over writes my software.
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      09-09-2010, 01:37 PM   #22
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Officially crossing the catless xpipe/tune off the list. I was on the fence so I'll just stick to my titanium slip.
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