I agree that better flow means more power, but I went from straight pipes to a custom crossover exhaust with race mufflers and several bends and that was enough to give me much better low end to mid range response and power. What happens below boost. your motor runs like an NA motor. So to much exhaust will cause lost torque in the low ranges. if you are drag racing only, big pipes will work best. But if you modulate the throttle like in turns, then an exhaust with some backpressure might work. But unfortunately there is no testing to compare this and mfg's are going to favor the system they sell, so that is useless.

 

nicely done are those 3" resonators where the cats used to be? either way looks good!

 

i believe your just feeling the differences that an X design makes as it pulls the exhaust from the opposite bank as one gets pushed out.

choked up piping ona turbo car does no good. back pressure is accomplished by the turbine housing.

 

Agree, the turbos themselves provide plenty of backpressure. I had a 4inch exhaust on my last car and I knew others with the same - almost zero backpressure from the exhaust. But one day I had a conversation with a guy who had taken the time to measure backpressure ahead of the turbo on such an exhaust. WOW! Exhaust pressure ahead of the turbo is much much higher, this is a big part of the reason why larger turbos make more power apparently - less backpressure. If you've ever seen those toys with the little spinning turbine thing in them that make noise when you blow on them you have some idea as to what the exhaust port sees as you blow into the toy. Now restrict the outlet on the toy, much less spinning right? That's what backpressure does to your turbo's turbine.

It's possible to measure the post turbo backpressure using one of the O2 sensor ports. You have to use a fitting and a piece of copper tubing to isolate the heat some, use a good gauge. I think Justinn was one of the guys doing it on Supras. I'd hope that some of the folks selling exhaust have at least tested the backpressure their exhausts represent if they're selling them as "tuned" at a couple grand a pop. Testing ahead of the the turbo is much harder and would require a specific fitting but can yield some interesting results that might help select a turbo for the hardcore.

 

Take a look at the dynos in the AMS thread -with the JIC exhaust added the car picked up everywhere, alot of it in the low end/midrange.

 

I have heard nothing but great stuff about JIC exhausts. I believe it. It would be interesting to compare that exhaust with a fabspeed cats and straight pipes. There may not be much of a difference.

 

I've always wondered if an X did much more than smooth the sound on a turbo car that had two banks. I know on NA cars the alternating pulses are supposed to help scavenge but wonder if the turbos smooth things to the point where this is less of a case. It is kind of surprising that no shop has apparently done a shootout with the various exhausts like the Supra guys did. ??? I bet it would really settle some questions! On these cars though it would probably be a PITA moreso than on the Supra and sure as heck more expensive to gather all sorts of exhausts together.

 

where can I buy this exhaust?

 

meanest sounding exhaust

 

They are 6.5" round, 3" ID MUFFLERS just like the smaller ones in the picture. We were able to put the larger diameter mufflers there since there is a lot of room (were the cats usually are). The 6" round suppress sound a lot better than the 4.5" used in the rear.

 

I did a back to back dyno test with my cat-less Maxspeed (same as Speedtech) 70mm system and my new 3" X design and actually LOST about 10-15hp. I didnt mind though because the crossover sounds VERY nice. I am actually surprised there are not a lot more guys dyno testing these setups, especially when their paying thousands for them.

 

I tried calling the guys at RB to get some info/specs on this exhaust and didnt really get anywhere. It is AWESOME sounding! My X-design 3" sounds like this but it doesnt have the cool turbo whistle to it like this one

 

How much was your exhaust? Any vids or soundclips?

 

Is it possible that tuning would have recovered the power? With the backpressure the turbos represent it just doesn't seem like the added backpressure from an exhaust would do anything for the short time that the motor isn't pressurized.

Surely you would think that more guys had done back to back tests on exhausts!

That RB exhaust sounds NICE! I'd love to see some pics of the design. If it had no drone I'd be VERY interested in it Something with 4 small mufflers and 100cell cats or something like dgreen posted although I'd really like to retain catalytics. Dgreen how does your's sound? Ah duh you said it sounds like that sans whistle. Wonder if that's turbo sizing doing that?

 

in an X-pipe design, you have to fast flowing air streams crossing each other causing turbulence. with an x-pipe you definitely want large pipes to reduce the exhaust speeds and reduce the turbulence. Hence the reason why I did an H pipe. I went from my fabspeed straight pipes with cats to the exhaust below with cats and I got rid of all the drone, reduced noise by about 20% and gained a little driveability and no loss of power according to my trap speeds. In fact my trapspeeds went up, but that could have been for other ambient reasons.