Last week I had to swap out my Perrin exhaust & cat delete and put back in my stock exhaust so that I could pass DEQ. I had passed the emissions part the week before but buggers pulled out the decibel tester and I was just over so I did not pass. The thing is… I find that I am now enjoying the “quiet” factor of the stock exhaust (I also put in some dynamat while I was at it). Now when I am cruising at highway speeds my Evo is seriously almost as quiet as my former late model Benz! While I have noticed that it is not spooling up quite as fast as before the butt dyno seems to be telling me that I have not last that much. Of course I have not tracked it to be sure and we are in the cold months.

So here’s my question:
Has anyone ever done a dyno after just adding the PERRIN exhaust & cat delete?

If so, I’d love to know how much you gained over stock. I also wonder if my flash is all whacked now since Al factored in the exhaust and cat-delete… guess I’ll have to ask him.

I dunno, maybe I’ll just keep it around and bolt it up for track days but I am also considering selling it…

Jason

 

The fact that it's Perrin doesn't really matter. Just the fact that it's a cat-back and test pipe means you lost 20-25whp. The flash should not be affected much by the exhaust change.

 

Thanks... I was afraid of that!

20+ is quite a bit to lose. I swear the butt dyno just never seems to be accurate... I'll really have to mull this over now!

Perhaps I'll just put the Perrin system back on and add a bit more dynamat. I was surprised that they dynamat really wasn't as heavy as I thought it would be (the weight penalty seems minimal). Right now I only have the floor under the front seats and tunnel covered. Amazing how well it works. Maybe if I just did under the rear seat and trunk it would quiet even the Perrin with cat-delete enough. Man, I am turning into an old fart... worried about loudness and all.

Jason

 

you'd be better off pulling the cat and putting in the cat delete and using the stock exhaust. The cat will be more restrictive than the muffler. The no cat/stock muffler will be more quiet and make more power than the cat/aftermarket cat back setup.

 

Yep... I was thinking about this option too! I'll bet the majority of the power gain does come from the cat-delete.

However, do you really think that the stock catback makes more power than the Perrin full 3' with a much straighter design? I dunno about that one...

Jason

 

I'm not sure if I'm reading your post correctly, but I'm willing to say your #'s are a bit on the high end. IMO, the DP/cat are the crap shoot of the exhaust.

Speaking of which, I wonder how many people actually know that their dp may taper when getting to the cat.

 

no, no.... I'm saying the cat delete/stock exhaust combo will make more power than the stock cat/cat back setup.

For sure, the Perrin will make more power than the stock cat back.

 

Well let me tell you exactley what you lost

Here is my dyno chart before and after. The first run is stock with no modifications and the second run (They are overlapped) is with the Perrin exhaust + cat delete with no other modifications. The net gain was 23 WHP.

 

Maybe; maybe not. When Buschur did his part-by-part dyno testing he gained 15-20whp just by replacing the axle-back, which showed that the stock muffler was the major restriction. I think it's reasonable to expect another 10whp from the cat delete. People go from ~230whp to ~300whp with mbc/tune/tbe, which is about a 70whp gain, 30 of which I attribute to the TBE...I don't think the DP is a large part of that 30.

 

Whats really evident in the dyno chart is that the spool up time is much quicker. I dont care much about a peak number since it doesnt necessarily mean you have improvement across the board. With the less restrictive setup it is obvious that you make more power sooner and hold a better curve all the way up to redline.

This dyno chart was also done with a full 3in TBE + cat delete so if Buscher is gaining 15-20 WHP then it would seem to make sense that the cat is probably only reducing your max power anywhere between 10-15 WHP. You got that GTECH Jason hook it up and find out I also got the latest GTECH RR which is really nice! Would be interesting to see how close they measure the same car!

 

I did roughly the same thing. Got tired of the noise and replaced my 3" cat back with the stock system.... I absolutely love the car with the stock exhaust. In my case I lost 10 whp with the removal of the cat back. I'd guess the whole TBE is worth 20~25 whp.... However, I think your tune might be off... I don't know what Al might have done when he tuned your car, but when I went back to the dyno to re tune my XEDE for the stock cat back, I was running very lean... This is dangerous in these cold days... I don't know if the Dynoflash changes your boost levels either, but if the car is tuned for the open TBE and you go back to stock, you could easily see boost spikes.... Again, I don't know about your setup, but with the XEDE, changing back to stock caused AFRs and boost to change in a dangerous way.... Fortunately that's what the dyno and the tuner are for... Andrew at Dyno4mance tuned the car for optimal performance with the stock exhaust (and stock everything else too, except for the JDM aluminum BOV). My car now puts down 249.3 whp on a DD dyno and it's quiet and comfortable....I'm pleased

 

Putting a stock exhaust back on shouldnt make you run lean, it should be the opposite. More air flow=leaner

 

i noticed a nice difference when i put my perrin cat delete on... i had HKS DP and HKS Carbon TI too

 

Hey maybe you are right, but the fact remains that after I replaced the 3" cat back with the stock one, the AFRs were much leaner than they were when the car was initially tuned with the 3" catback.... Also, it definitely was spiking the boost to 23 psi.... I don't know much about the theories behind all this but I definitely know what the numbers were from the instruments in the dyno.....

 

Thanks all for the good feedback.

Chris… essentially my Gtech is now the RR as well because TESLA let me upgrade to the RR version firmware for free after they came out with the RR. However, it would be interesting to see if there is any variance between the units. Yeah, I probably should just go out and do some runs, but I think I may have changed the boost settings since my last session as well, so I would not be comparing apples to apples… not to mention that I am starting to get wary of making hard launches as I don’t want to replace my clutch right now.

Anyway, I think I will consider putting the cat-delete in with the stock cat-back and see what that is like. I dunno, I will probably will just end up bolting it all back on. It’s just nice to have it be so darn quiet.

Personally I would think that the car would be running slightly rich with the Flash still set for the other exhaust and cat-delete (but what do I know??). I do know, that I haven’t seen anything alarming on my AFR or EGT gauges, however, I don’t know how reliable they are. Sounds like I should just talk to Al about it to be sure.

Cheers,
Jason