bmwtye

Was wondering what kind of numbers you guys are seeing with these modifications. Preferabley, do you have before and after dynos. I know GT3Ranger saw about 26rwhp and good gain in midrange hp and trq, with the FVD setup, just wondering if anyone else has done before and after dynos?

Also, would like to hear your impressions on how the car felt after the mods.

997gt3north

if you search under my posting name (997gt3north) you will find before and after dyno charts of:
stock, stock with sharkwerks rear exhaust, sharkwerks exhaust with FVD softwre - sorry, no before and after headers,

awe-tuning posted some before and after header/exhaust plots

awe's plots also show basically what is possible
1) headers give you lets say 15whp in the low rpm range, none in the mid range
2) highflow cats give you lets say 5-10whp in the very highend (there is a question by some as to how long 200cell cats will last in a gt3)
3) software tuned for more aggressive timing on 93 octane can give you "maybe" 5whp - if you run 100octane then more is possible

- also, you should know, that porsche claims that the 997gt3 cannot be "properly" dynoed on a 2wdr dyno as they say the car will "sense something wrong" and put the car in a slightly safer mode (thus you will need an engine dyno, or a dyno where the rear wheels are connect to a belt or by electronics that will then turn the front wheels at the same rate)
- my own dyno experience, given realworld / guesstimated / known transmission loss ratios is that this "safemode" likely results in very minimal if any loss

bmwtye

I did see your original posting, and was more curious as to the look of the before and after curves with headers. GT3Ranger mentioned a considerable gain in midrange hp and torque with the FVD header and exhaust. Im wondering if anyone else also has this setup and what they are seeing.

Im also curious as to the results of someone who has done the cargraphic system. I know cargraphic has dyno charts, but Id like to see independent ones. I know the gains are to be had with the headers and cats, while the exhaust really does nothing.

In terms of sound, the sytem sounds I like the best are the cargraphic headers, cats, with sharkwerks exhaust (fred's old setup), and the full FVD setup. But performance comes first over sound, so I want to see what the best combo is.

Todd/A.W.E.

The most comprehensive GT3 exhaust dyno testing you will find to date:

AWE Tuning GT3 Exhaust Development

We did 159 dyno runs during development, and found that, contrary to popular belief, a rear or side muffler delete will result in significant power loss. All adaptation and weather variables were accounted for during our testing (It's a bitter pill to swallow for people who have done the rear muffler delete mod, but we believe serious track users will demand performance over sound alone).

Details of our system found here:

AWE Tuning Exhaust Details

Jon70

With a rear muffler delete, don't you initially get a power loss until the ECU 'resets' after about 200 miles? and after the 'reset' power readjusts to normal?

Todd/A.W.E.

That's what some people are now wanting to believe, but what you are describing is the ECU adapting.

Accounting for ECU adaptation is a major challenge when dyno testing any modern Porsche, and we learned a long time ago how to eliminate it from the equation.

The bottom line is that with careful, controlled testing, you can see that even with the ECU "reset", there is major power loss with a rear muffler delete. You won't see this with 2 or 3 runs before and after. Dyno testing a GT3 is not a casual affair.

For example, we did several *dozen* runs both before and after when we tested what a rear muffler delete did during our exhaust development. This was almost a year ago before any of the current designs were on the market. We *wanted* this sort of mod to work, as it would have made our manufacturing and development a lot easier. The fact is, after extensive testing, we could not generate data to support that approach.

I know this is a sticky subject, since there is conflicting information from the companies selling rear muffler deletes, and all the GT3 owners with this mod on their car don't want to learn that they have lost power. I don't want to belabor the point, but we did 159 dyno runs. The data we accumulated during this testing is *very* conclusive.

340Elise

Todd,

I don't know how familiar you are with the Lotus ECU for the federal cars, but it is a major PIA for teh aftermarket developers. It has a learn function that basically ends up negating any gains from intake and exhaust modifications and often leads to reductions in HP. In the beginning, when the aftermarket tuners started developing some bolt on mods for the cars they did before and after dynos on the car and would get some significant gains of 8 to 12 hp with intakes and exhaust. However, what they found is that after driving the car for several hundred miles that not only did they lose these gains, but they would also often end up with less power and CEL's. The ECU also has a limp mode that will put the car in a safe mode if it thinks something is very wrong; however this is a dramatic reduction in power.

Anyway, is this similar to the new GT3? What about reflashing along with adding bolt on mods to correctly take advantage of the mods? I know that on the Lotus this was all encrypted and took a long time for a few very smart individuals to finally figure out (like one or two in the world).

Anyway, I am about to take delivery of my GT3 in a few days and I am going to be very selective about any aftermarket mods (if any) that I do to potentially increase engine power. The other thing I keep hearing is just how good the stock exhaust is and how difficult it is to improve upon; I noticed that was one of the first things you admitted about the system; which I like.

I need to drive the car and listen to the engine note before I decide if I want to modify it anyway. But if I do, I want to lose weight, significantly change the torque curve of the car for the better (since it is NA, I think the low and midrange are most important), and lastly, make it sound even better than it already does.

Let me know if my Lotus analogy is similar to what you are describing or if I am way off.

Stephen

rsman

Todd, thanks for your fine work and candid responses.I am curious of your views on the following: Porsche as you have indicated does alot of homework on their exhaust systems and it is very difficult to improve on. One of the important elements in that process is their resonance tuning with I assume is ( and Porsche seems to imply this in their technical literature) accomplished in part by the design of thier rear muffler and the balancing of exhaust flows from each cylinder bank. On the awe system each cylinder bank is a stand alone system with seperate mufflers and no balancing between the two. The question is whether you think additional gains could be had with flowing the exhaust from both banks into a shared rear balancing muffler and whether awe has considered or tested such an approach and whether awe considers there to be any benefit from such approach?

Jon70

Has anyone 'dissected' the rear muffler of the GT3? I am curious as to what the tubing looks like beneath the muffler housing.

TB993tt

It is worth mentioning that the Cargraphic dyno plot pictures are taken directly from the RS Tuning engine dyno plots -this is a very expensive Borghi & Saveri engine dyno (same brand used by Ferrari F!) which measures the torque the same way Porsche do it - NOT the same as any number of rolling road "power runs"......

Todd/A.W.E.

Stephen,

That is *exactly* the issue that needs to be contended with when developing products for the GT3 (and most all modern cars). However, the "adaptation period" on the GT3 can be accelerated by controlled back to back tests. We verified this by retesting a control car after several hundred miles of field use.

The fuel injection ECU not only will adapt its air/fuel and ignition advance on the GT3 in response to an altered load from exhaust modifications, but it will also "jump" ignition timing maps easily if intake and coolant temps are not rigorously controlled during testing. It is *very* easy to unknowingly corrupt data when dyno testing these cars. See this thread:

How To Properly Dyno Test a Modern Porsche

The only way to know if the modification has indeed liberated power is to do enough dyno pulls with careful intake/coolant cooling to see a trend emerge. For us, that meant dozens of pulls at each stage of development, as well as same day swapping between stock and modified parts as a final check.

For the record, our gains were recorded with the stock ECU programming. We ultimately developed a system that was not canceled out by long term ECU "learning".

Todd/A.W.E.

First, the mechanisms that Porsche uses in their OEM GT3 mufflers to produce this resonance tuning effect is quite complex. It is a series of chambers and baffles found throughout the system. The rear muffler itself is far from being two alternate paths depending on what flapper mode you are in. Looking in from the side inlets, you would be shocked to see the myriad horn shaped tubes and perforated walls. Therefore, we were not that perplexed when a simple bypass pipe in place of the rear muffler did not improve power. The equation on this car was more complex than that...

Anyway, as we admit in our site literature, we shortcutted our development process by "borrowing" some design cues from what Porsche did on the 997 RSR. Up until that point, our progress was fairly minimal, and we had done at least 6 prototypes deleting mufflers with different diamater tubing, using various balance tubes, playing with header lengths. Our tools were a combination of experience, CFD software, and dyno tests, and yet we still had minimal luck improving on the highly developed OEM system.

In reality, we could have spent many thousands of man hours to "evolve" on the factory's resonance tuning results, but we just did not have the time or resources to do so. If we were not able to co-opt the RSR design and see actual, repeatable gains, we would have scrapped the project (to great cost to us, but we have done so on other cars rather than release a "vaporware" product).

The tradeoffs of the RSR inspired design vs OEM:

1) the elimination of a street/sport mode mechanism, which would not pass strict EU noise regulations. Here, we were not held to the same standard as Porsche with the OEM GT3 system.

2) placement of a cat further away from the cylinder head vs stock, which technically increases warmup emissions. This would not pass CARB or Federal emissions certification standards, even though a check engine light is not set. Since our system is for off-road use only, we were not held to the same standard there as Porsche with the OEM GT3 system. (The RSR does not use a cat, but we had to adjust some system specs to account for this slight increase in backpressure vs the RSR design).

3) fairly labor intensive hand building of components. The factory was able to use some pre-existing tooling for the OEM system, such as for the fender muffler cans and header collectors. For a specialty, yet "mass produced", vehicle like the GT3, there is still a cost tradeoff on certain parts, leaving some performance (albeit meager) on the table.

So, without being able to take some design cues from the RSR system, such as the header primary lengths and primary diameters, we may have moved onto less challenging exhaust projects. Even with this "help" our entire development process took a year and multiple test cars to finalize, due to how we had to adapt the basic RSR design to street use.

This was the most challenging exhaust project we undertook to date, and we executed it to the best of our abilities and resources. Could there be more power to be found? Maybe. But that would drive the price even higher and come with too much of an opportunity cost to us. As it is, we are very proud of the power gains made.

This is in stark contrast, we feel, to the systems that popped onto market immediately after the car hit our shores...