what do you think about awe header, 200 cell cats, stock 997s mufflers?

you say your combo is flat sounding at low rpms. compare that to a stock system. do you mean its quite like the stock system?

 

There's a few people on this board that are running that setup or have run it. The few that I know who did this thought it was a little raspy but still sounded good.

Dave

 

so the awe mufflers made the sound deeper?

 

Gotta see numbers to support that, personal commentary is great but is still speculation - There have been posts to the contrary where introducting too much exhaust free-flow reduces power /tq on the flat six, and sticking with stock cats has been recommended. No numbers / data to support those posts either, btw.. so again just more speculation.
As my only personally verifiable example on the "too much free flow" theory, dyno testing with bypass pipes gave me about 5hp up top but I lost about 7hp on the bottom. I'd rather have the TQ!

It would have been ideal if you managed to test actual results of changes, looks like you've had a fair number of combo setups looking for the perfect blend. Even though my tested numbers and general performance improvements are pretty good IMO, I'm still on the hunt too- But but not willing to experiment with another $2-$3k in new parts until I see hard data first.

I remember when I first installed my KN intake on the 996 (first mod ever)- car sounded Mean!!! I figured it had to be giving me some good gains, I could feel it! Dyno tested and it added just 5whp up top..., 0tq over stock..

 

coming from the vette world, i have noticed that vette guys will dyno a MAF let alone bigger mods but porsche guys rarely dyno anything.

it may have to do with the demographic or the fact that porsches put down very low numbers compared to other cars.

with my Z06, my baseline dyno was 447rwhp so getting into the numbers game was exciting.

the last time i was making 300rwhp was 15 years ago

 

Bara - LOL.. Well it could be the fact that I transitioned from American muscle to European.. The whole "dyno it" thing carried over with me i guess.. I'd usually say "well I'll beat your @$$ in the corners", but of course a well set up Z06 is no slacker there either

 

You're right - intakes on these cars don't do so very much. The stock airbox isn't too bad on its own. Most problems at low rpms from intakes are due to laminar air-flow (or lack thereof) across the MAF sensor. The stock airboxes employ a series of flow straighteners to ensure the MAF reads correctly from low to high flow. Most aftermarket intakes dispense with these and the MAFs then don't read true at low RPMs / low flow. Warning: ***Controversial Statement***!! This is the reason for most CELs with aftermarket intakes, not oil contamination of the MAF!

As for 'too-free-flowing' exhausts. I've said this before - there is little or no back-pressure even with a stock exhaust at low rpms. Yes, that's right, they don't (normally - there are exceptions like the early VW Beetle) have 'designed-in' back-pressure. Think about it. If your exhaust was already restricting the exit of exhaust gasses when the engine is producing say 90BHP at full throttle at 2000rpm (I'm guessing the actual output of the engine here) then how the h*ll could it flow the amount of gas needed to accommodate the engine when it's producing 355BHP at 6750rpm? There just isn't sufficient exhaust gas at 2000rpm to cause back pressure. Period! The changes in low-end torque result from the changes in pipe length and diameter and hence the scavenging effect produced. Also, an engine is quite critical of fuelling and timing under these conditions. Changes to the hardware mean changes to the both fuelling and timing are likely required. A custom re-map to match the hardware will often redress this.

My own car is going into one of the UK's most respected tuners for a custom remap in about a month's time. (This firm mapped 7 out of the first 8 cars to finish the opening round of last year's UK Porsche Club Championship so I guess they know what they're doing)! The spec I'll be taking is stock except for a BMC-F1 filter panel, Fabspeed-style smooth intake hose, AWE headers, cats and mufflers. It will also be mapped to use 99-RON Shell V-Power gas. One of the main things I'm looking for (apart from best top-end) is to really sort the car under 3200rpms too - when it's on the low-lift inlet cam. I'm looking forward to the results and to reporting back.

 

Ian- Great post. You are actually right, what us laymen call "backpressure" in terms of exhaust disccussion are more accurately described in your statement. I actually called Brian at AH and asked him about this and he gave me just about the same exact answer as your post- Which is why (per Brian) he designed the AH mufflers with almost the same length of piping as the stock mufflers, with of course minor differences designed in to help performance and scavenging.

I'm anxious to hear how your tuning session goes. Any chance you can get a before / after dyno comparison? If they can do it, ask them to remap your gas pedal input so it is more responsive off idle. That is a big pisser for me.. tough to blip throttle due to built-in lowered response curve of software controlling egas input. The more you press the egas pedal the more the software begins to map input to a 1:1 ratio (i looked at a spec chart from porsche tech on this). In contrast, cable throttles are always a 1:1 ratio.

I'm still not sure who to go to here in USA (west coast) for that level of tuning..

 

this is the best exhaust discussion ever. thanks everyone for taking the time and post these info

 

You know what's funny, I was the OP on this thread..look at the date

When I originally posted it up it got a few responses...but it just blossemed.

Dave

 

that's why I was surprised when I saw the replays, I was asking my self how come I didn't see this review before but the date explained it all