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      05-06-2012, 08:51 PM   #45
flinchy
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Quote:
Originally Posted by Obioban View Post
Just to show that I wasn't lying..

spreadsheet of some various e46 M3 exhaust setups.

Check out the Bora midpipe. The Borla isn't anywhere near as extreme as the racing midpipes I was describing, yet even on this (which they consider a street setup), the torque at 2800 rpm (highway cruising RPM) goes from 214 (all stock) to 123 with the midpipe. You absolutely can kill your torque and street drivability with the wrong setup.



The midpipe above is considered a street part still. The mids I was talking about, that people use for race cars (that gain the big numbers) are far, far worse. I can also say that with first hand experience, btw-- I have one of those pipes on my e36 M3 race car (385 hp NA, from the S50B32 (euro spec e36 M3 engine)). It's completely dead below 5000 rpm (not what you'd expect from a 385 hp, 2315 lb car :P).
i've been a part of hundred page long discussions on it, but torque and hp can be near analogous, as either one can be geared for, and geared out... the fact it has lower torque.. *should* be COMPLETELY offset by significantly higher hp as well, at the torque's low point.. unless something is very VERY wrong and there's also a power defecit at the same revs.. or there is a much greater torque defecit than there is horsepower gain

though if you look at number 12 with a custom mid pipe.. has the same high end power and the best torque to match, so it really looks like there's something actually quite wrong with the borla midpipe as every single one of those graph entries lowers the torque... i'm guessing it steps down in diameter, or has dodgy bends?.. so yeah i's hazard a guess that it's actually poor design rather than being 'too free flowing' or anything like that :/

would like to know more about it though as that's really super dodgy lol.


as i said, we'll see how the headers stack up against each other... MMW's have been in testing and development since about october (or even before likely), so you can't say they haven't done their work at least lol
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      05-07-2012, 12:21 PM   #46
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Amusingly I ran #12 on my car for a bit. It had low end and top end but the middle range was dead.
(this document was from the development process of the Borla V2 mid, and the "custom" pipe listed up there in #12 became the borla V2)

The race mids for the 46 M3 do prove they can be "too free flowing", though. They get you to ~320-330 whp, but completely destroy the bottom/middle end. Said first hand, as I have it on my race car.
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      05-07-2012, 07:55 PM   #47
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Hmm sounds like there must be other issues? If theres correct afr and enough compression and timing and appropriate cam durations as such with little exhaust gas to ruin the stoich, there should be appropriate power, mathematically :/ :/ :\ :\
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      05-08-2012, 06:23 AM   #48
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It sucks that N52 isn't getting the love it deserves.

I am considering emailing Insight Racing for their 128i in the CTSCC series to ask the about what the heck they are doing for power
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      05-08-2012, 07:57 AM   #49
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Quote:
Originally Posted by flinchy View Post
Hmm sounds like there must be other issues? If theres correct afr and enough compression and timing and appropriate cam durations as such with little exhaust gas to ruin the stoich, there should be appropriate power, mathematically :/ :/ :\ :\
Custom dyno tuning and proper AFRs across the board.

Nor is this unique to my car in any way. 99% of the race prepped M3s are running such a pipe, and all compromise the bottom end.

It's just not as simple as freer flowing = better.
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      05-08-2012, 08:02 AM   #50
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Quote:
Originally Posted by Evice View Post
It sucks that N52 isn't getting the love it deserves.

I am considering emailing Insight Racing for their 128i in the CTSCC series to ask the about what the heck they are doing for power
there's a workshop a couple of hours from where i live (just south of brisbane) (rx automotive) that i've been told has a fairly race prepped 130i... i plan on getting mine serviced there next (as they're obviously the best for the job, as well as apparently being really cheap ^_^) so i plan on asking them a few choice questions on the matter

i assume they've just done basic stuff (I-T-E) and the full range of handling mods... though i'd like to know if/where they got their tune done since there's nowhere to get a decent one oever here


Quote:
Originally Posted by Obioban View Post
Custom dyno tuning and proper AFRs across the board.

Nor is this unique to my car in any way. 99% of the race prepped M3s are running such a pipe, and all compromise the bottom end.

It's just not as simple as freer flowing = better.
yeah if you have a poor pipe the frequency/speed (and therefore temperature) of the gas could flow badly with that specific pipe/merge at a specific rev rangecausing the gas itself to effectively restrict the exhaust flow.. that's the only other reason there could possibly be, really.

i have heard of that happening with most cars though, as the exhaust travels in pulses, a properly sized and.. well everything, exhaust, will create a slight vacuum in the cylinder chamber allowing that fraction more air to flow in... however the inverse is possible where it pushes some gas back in and hinders everything

i mean, if you have (just for a ridiculous example) 2" pipes out of each exhaust port with minimal bends (say two, one out of the block one to get to the outside of the car) straight all the way back, you'll find increased gains accross the board no doubt

Last edited by flinchy; 05-09-2012 at 04:12 AM.
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