Midpipe Muffler Horsepower Numbers!
It's never fast enough...
Joined: Feb 2001
Posts: 3,760
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From: Miami - Given 1st place as the POOREST city in the US as per the federal government
I talked to Borla about their heat resistance to the exhaust temps of a rotary. They told me the same stuff they make their muflers out of is what they pack their mufflers with. Aircraft Stainless steel packing.
I've had their original CB for over 50k miles with no problems and no sign of it falling apart ANYWHERE.
Also, their XR1s have been known to cause a 1-2hp loss when COMPARED to a straight pipe....
I've had their original CB for over 50k miles with no problems and no sign of it falling apart ANYWHERE.
Also, their XR1s have been known to cause a 1-2hp loss when COMPARED to a straight pipe....
Senior Member
Joined: Mar 2002
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From: bay area
Originally posted by Apexi
Yes, but do you have actual numbers, or just going from observations?
I'm surprised to see that out of all the people on the forum, a very small percentage seems to have actual numbers (ie/ dyno or at least GTECH).
Yes, but do you have actual numbers, or just going from observations?
I'm surprised to see that out of all the people on the forum, a very small percentage seems to have actual numbers (ie/ dyno or at least GTECH).
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Joined: Mar 2001
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From: EA
Yup, the muffler is a 3" straight through. Well from all the feedback thus far, I've come to the conclusion that it must be either ignition related (spark plugs) or AFR related (running too rich?).
I've noticed before with the midpipe, I could not get lower than 11-12psi boost, even with a ported wastegate. Now with the muffler/midpipe I can control boost to wherever I want it, even down to 8psi, so it's definitely adding some flow restricition.
I'm determined to figure it out. I've had my AFC richen my fuel 3-4% at 7,000-8,000 RPM just for safety. That seemed to be fine with the straight midpipe, but maybe too rich with the muffler. So I zeroed it all out, and went for some test again today. My numbers seemed to be getting close to where they were before, within 5 HP of the midpipe, but I'd say the results are inconclusive at the moment, since there was too much variance in the measurements. I couldn't get in solid runs since there was too much local traffic, and therefore I had to move around here and there, and ended up doing the runs on different roads.
I'm just going to wait for a clear night (it's been raining straight for 2 weeks), and do some good solid runs at my usual strip when I get the chance.
I'll post up the results.
I've noticed before with the midpipe, I could not get lower than 11-12psi boost, even with a ported wastegate. Now with the muffler/midpipe I can control boost to wherever I want it, even down to 8psi, so it's definitely adding some flow restricition.
I'm determined to figure it out. I've had my AFC richen my fuel 3-4% at 7,000-8,000 RPM just for safety. That seemed to be fine with the straight midpipe, but maybe too rich with the muffler. So I zeroed it all out, and went for some test again today. My numbers seemed to be getting close to where they were before, within 5 HP of the midpipe, but I'd say the results are inconclusive at the moment, since there was too much variance in the measurements. I couldn't get in solid runs since there was too much local traffic, and therefore I had to move around here and there, and ended up doing the runs on different roads.
I'm just going to wait for a clear night (it's been raining straight for 2 weeks), and do some good solid runs at my usual strip when I get the chance.
I'll post up the results.
Last edited by Apexi; Nov 16, 2002 at 03:21 AM.
Rotary Enthusiast
Joined: Mar 2001
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From: Mechanicsburg, PA USA
Although I can't find the numbers or links anywhere, I have heard of some people with HF cats making as much or a little less than people with midpipes. One guy dynoed at KDR and found no change at all in going from a midpipe to a HF cat, just a little different curve. For dyno purposes I'm sure the midpipe would get you the high peak numbers that everyone wants to see. Like I said, I felt a bit more power up above 6K rpms with a midpipe but the car didn't feel as powerful overall as it does with my HF cat.
I know Rich (Goodfellas) dynoed at 337 rwhp with a midpipe at 13 psi and 368 rwhp with a HF cat at 15 psi - meaning they would be pretty close. I guess it just depends on the car. The Borla XR1 seems like the happy medium though.
I know Rich (Goodfellas) dynoed at 337 rwhp with a midpipe at 13 psi and 368 rwhp with a HF cat at 15 psi - meaning they would be pretty close. I guess it just depends on the car. The Borla XR1 seems like the happy medium though.
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Joined: Mar 2001
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From: EA
Originally posted by kwikrx7
Although I can't find the numbers or links anywhere, I have heard of some people with HF cats making as much or a little less than people with midpipes. One guy dynoed at KDR and found no change at all in going from a midpipe to a HF cat, just a little different curve. For dyno purposes I'm sure the midpipe would get you the high peak numbers that everyone wants to see. Like I said, I felt a bit more power up above 6K rpms with a midpipe but the car didn't feel as powerful overall as it does with my HF cat.
I know Rich (Goodfellas) dynoed at 337 rwhp with a midpipe at 13 psi and 368 rwhp with a HF cat at 15 psi - meaning they would be pretty close. I guess it just depends on the car. The Borla XR1 seems like the happy medium though.
Although I can't find the numbers or links anywhere, I have heard of some people with HF cats making as much or a little less than people with midpipes. One guy dynoed at KDR and found no change at all in going from a midpipe to a HF cat, just a little different curve. For dyno purposes I'm sure the midpipe would get you the high peak numbers that everyone wants to see. Like I said, I felt a bit more power up above 6K rpms with a midpipe but the car didn't feel as powerful overall as it does with my HF cat.
I know Rich (Goodfellas) dynoed at 337 rwhp with a midpipe at 13 psi and 368 rwhp with a HF cat at 15 psi - meaning they would be pretty close. I guess it just depends on the car. The Borla XR1 seems like the happy medium though.
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Joined: Mar 2001
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From: EA
while on this topic, just wondering if anyone has actual numbers of what kind of power difference the following would typically make:
1. poor spark plugs
2. dirty intake filters
3. running a little too rich
From my experience, I know a loose plug wire can easily account for 50-60RWHP, and running too rich can account for 10-15RWHP. I don't have any experience or know what fouled plugs or dirty intake filters would do.
1. poor spark plugs
2. dirty intake filters
3. running a little too rich
From my experience, I know a loose plug wire can easily account for 50-60RWHP, and running too rich can account for 10-15RWHP. I don't have any experience or know what fouled plugs or dirty intake filters would do.
Senior Member
Joined: Mar 2002
Posts: 401
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From: bay area
Originally posted by Apexi
while on this topic, just wondering if anyone has actual numbers of what kind of power difference the following would typically make:
1. poor spark plugs
2. dirty intake filters
3. running a little too rich
From my experience, I know a loose plug wire can easily account for 50-60RWHP, and running too rich can account for 10-15RWHP. I don't have any experience or know what fouled plugs or dirty intake filters would do.
while on this topic, just wondering if anyone has actual numbers of what kind of power difference the following would typically make:
1. poor spark plugs
2. dirty intake filters
3. running a little too rich
From my experience, I know a loose plug wire can easily account for 50-60RWHP, and running too rich can account for 10-15RWHP. I don't have any experience or know what fouled plugs or dirty intake filters would do.
2. dirty intake filters ---> can be verified visually and a piece of cake to replace
3. running rich ---> can be verified once you pull your spark plugs and if nothing is being done to solve it expect your cats to clog!
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