Nizer

Anyone here running or tried GMG's World Challenge Sport Header system on 997 GT3/RS?

http://www.gmgracing.com/porsche_exh...72header.shtml

Curious about your experience. Thanks.

911SLOW

+40hp from an exhaust in a 3.8RS?

So with a filter and a DME upgrade you are at the 4L's 500hp mark.

Nizer

Actually just header and cat, not full exhaust, but hence the question. I suspect if there were 40hp to be had by changing headers and cats Porsche would've addressed it.

Izzone

Interesting

There is a local guy here with cargraphic headers / cats and he can walk away from reter and I in a straight line

As much as more HP sounds good.....these car sare having a hard enough time with the HP they have

Izzone

Emissions.....I believe 200 CEL cat sin lieu of 400

Even Porsche has less restrictive cats on 4.0

paver

Are you talking about engine failures? I think I saw you post somewhere that some RS's had blown motors.

Izzone

I am referring to drivetrain

but yes some have went boom, if you drive them enough you will find out if yours is one that might go boom

911SLOW

Before discussing the +40hp, I will digress for a moment to ask you:

What do you mean? engine failures and drive-trains that went boom

997gt3north

It is all above 7000rpms, which is perfect on the track, but it is my bet that 95% is due to the CATS. If someone could sell a 100 cell CAT that can pass smog and not blow apart after 1 DE season then I would do this for sure - why wouldn't you if you track your car.

Izzone

Check email

911SLOW

In the above mentioned setup, they are using 200cell cats..not 100.




-Rs tuning measured for cargraphic (on a proper real engine dyno) a 3.8RS with equal length headers with mandrel bends, F1 style collector box with spike, 200 cell HJS cats, full exhaust and a BMC filter. Peak gains were 17HP and 5NM..
Headers alone gave +10HP.

-Akrapovič measured +17 HP (and not in peak power) with their full race system and headers running 100cell cats.



Their (independent) dyno results are outside of the expected gain ranges, giving me a reason to suspect that the dyno test was not done correctly.
If it's an equipment failure or a mistake in the methodology is unknown. (These cars are tricky to measure properly. You need to monitor and stabilize many parameters and if you are working with a rolling dyno you need to do a lot of runs and average results, a single back to back run is useless)


Besides GMG appears to be a serious company, and from what I hear their exhausts are very well made, so I can't think that they really need to claim anything extreme or fake to sell them.





BTW I respectfully disagree with you regarding 100cell cats.

Quality 100 cats don't "blow apart" in the first DE.
I have thousands of miles on them in various hi-revving cars (including an x-track clio cup car).

I will give you one example: a hard driven 2001 996 GT3 MK1.
10yo motorsport 100cell cats with 90,000klm.. like new.


Akrapovič, Manthey, Cargraphic / RS tuning, Europipe etc, are all using 100 cells per square inch (cpsi) catalysts..


Passing smog tests or OBD compliance? I am not so sure. It probably depends on the country. I can pass the EU4 test here with the mk2 gt3 as long as the HJS MS 100 cats are super hot.

aussie jimmy

i have run 200 cell cats on my golf for last 4 years; zero issues.

Nizer

Somebody please enlighten me on cats because it's always been a bit of grey area.

What's the difference between 100 cell vs 200 vs 400?
I assume not all cats of same cell count are created equal. True?
I've heard other board sponsors/members make reference to stock cats not lasting long. How much truth is there to this?
What's the difference between the stock cats on 3.8 vs 4.0 RS?

997gt3north

I didn't say 1 DE, I said 1 DE 'season' - and in a car that sees 8500rpms.

If you really search and ask around - the shops will confirm this - this is not new news.

Porsche going to 300 cell cats in the 4.0 pretty much confirms at the very high rpms - it is the cats and unrestricting them is where some free HP can be found.

I have a lot of dyno experience with lots and lots of setups in the turbo world and can tell you that very high flow cats do make a real difference

aussie jimmy

nizer, 100/200/400 etc refers to the number of holes in the cat; more holes more restriction.
less holes, more flow, but also creates more pollution and can cause cel on oem tune
not all cats are created equal. basically, the lower cell count flows (breathes) much better at high rpms, but can be a dog in the lows, so depends on the type of car and it's application.
that is why 200 or 300 are a good all-round application.