Question about Custom Headers + Tuning + Cats?

jrhaile · 24th October 2007, 05:36

My car is going to a shop in Portland this weekend for two weeks where they will be designing and developing custom headers for the E39 M5 at a FRACTION of the cost of SS and Dinan (I will report information on the shops info after they're done and we have a conclusive dyno and testing procedure has been completed). Anyways, my question is will I need to get some sort of custom tuning ie PowerChip or something to accomodate the changes to the headers? I realize it's better to do so in terms of power, but is it necessary and is it harmful not to do?

Now onto my second question... I register my car in Idaho where there are ZERO admission's. Would removing the cats harm the car in anyways? Any performance gain or loss? I know in past not having my cats on really helped my other cars breathe, but the M5 is a whole other beast

Thanks for any info you guys have and I'll be sure to report in as soon as the headers are done...

mottati · 24th October 2007, 06:11

Quote:

Originally Posted by jrhaile

My car is going to a shop in Portland this weekend for two weeks where they will be designing and developing custom headers for the E39 M5 at a FRACTION of the cost of SS and Dinan (I will report information on the shops info after they're done and we have a conclusive dyno and testing procedure has been completed). Anyways, my question is will I need to get some sort of custom tuning ie PowerChip or something to accomodate the changes to the headers? I realize it's better to do so in terms of power, but is it necessary and is it harmful not to do?

Now onto my second question... I register my car in Idaho where there are ZERO admission's. Would removing the cats harm the car in anyways? Any performance gain or loss? I know in past not having my cats on really helped my other cars breathe, but the M5 is a whole other beast

Thanks for any info you guys have and I'll be sure to report in as soon as the headers are done...

yes, you need software, the car will run lean otherwise. Eventually, it will probably trigger an ses light and go into limp home mode. (i think the car will do that before it will burn a valve).

As for idaho, you mean emissions testing, right. If you take the cats out, again, you'll need software to compensate for the post cat o2 sensor, or you'll constantly stare at an ses light. Assuming the car is tuned ok, won't hurt anything, but modern cats are not bad, you may gain 10hp or so.

Once you have your headers and exhaust, you'll want your car tuned by someone who can do some data collection and make a program that works for your situation.

Car will smell quite badly without cats though.

Vee Ten GP · 24th October 2007, 08:04

You can get EXCELLENT headers for the E39 M5 and 540 here in South Africa for about R6000 (fitted) this equates to about $925-00 so you you guys get charger STUPID money for this kind of work.
They work very well and i have had a set on my 540 for 100000 miles now.

xr4tic · 24th October 2007, 08:46

Quote:

Originally Posted by mottati

yes, you need software, the car will run lean otherwise. Eventually, it will probably trigger an ses light and go into limp home mode. (i think the car will do that before it will burn a valve).

I don't think this will happen. If we had a speed-density (MAP based) system, then yes, it could happen, but being MAF based, we always have an accurate amount of air enterring the engine (assuming MAFs are in good shape)

Unless you increase the engines efficiency so much that the MAF maxes out, I don't think you have anything to worry about.

With the headers, you can probably run more ignition timing, maybe change VANOS, and unlock a few more HP.

mottati · 24th October 2007, 18:11

Quote:

Originally Posted by xr4tic

I don't think this will happen. If we had a speed-density (MAP based) system, then yes, it could happen, but being MAF based, we always have an accurate amount of air enterring the engine (assuming MAFs are in good shape)

Unless you increase the engines efficiency so much that the MAF maxes out, I don't think you have anything to worry about.

With the headers, you can probably run more ignition timing, maybe change VANOS, and unlock a few more HP.

it will, there are limits to the parameters that the dme will adjust the afr, once it hits those limits, the ses light goes on, with a 'plausibility' code, and if you try to puch the car, it goes into limp home. It's happened to me, and to many others on the board over the years. Could try to do a search using the term 'adaptation tables', if you're curious.

xr4tic · 25th October 2007, 01:16

Funny, I just read this article:

http://www.europeancarweb.com/tech/0..._m5/index.html

They reported an opposite affect, the car going rich after headers installed.

Adaptation tables are only modified during part-throttle cruising, narrow band O2 sensors are not accurate enough for WOT adaptation (but WOT will use the adaptation table, it just wont modify it)

I guess it's another case of Theory being slapped around by Reality

jrhaile · 25th October 2007, 04:18

Man.. so much confusion haha... so going catless seems like a bad idea but how about high flow cats like from Magnaflow?

mottati · 25th October 2007, 19:15

Quote:

Originally Posted by xr4tic

They reported an opposite affect, the car going rich after headers installed.

Adaptation tables are only modified during part-throttle cruising, narrow band O2 sensors are not accurate enough for WOT adaptation (but WOT will use the adaptation table, it just wont modify it)

I guess it's another case of Theory being slapped around by Reality

my car ran decently under part throttle conditions before software, but if i tried to go wot, i'd get an ses light, and if i persisted, i'd get a misfire followed by limp home. The adaptations had done as much as they could and reached their limit.

Even with an 'off the shelf' powerchip for headers program, i'd get a misfire and limp home consistantly under track conditions. Could duplicate it, until i had my car tuned by dinan under 'real world conditions' with thier data acquisition equipment, which finally solved it.

Not sure what you are refering to with the 'theory vs reality' shot, but that was my car's reality.

AfricaOffroad · 25th October 2007, 19:46

Quote:

Originally Posted by Vee Ten GP

You can get EXCELLENT headers for the E39 M5 and 540 here in South Africa for about R6000 (fitted) this equates to about $925-00 so you you guys get charger STUPID money for this kind of work.
They work very well and i have had a set on my 540 for 100000 miles now.

You have PM.
I'm very interested in finding out more on the SA source.