2JZ-GE Exhaust Noise

[scott87]

without exhaust scavenging you will be loosing some low and mid range tourqe but should still make more than having the stock cat in so yes. your really long pipes may be able to promote high hpm power! If only I was still back at school and had access to the equipment we had there! If I knew exactly the velocity of the exhaust and could measure the pulses and knew the exact length of the runner I could make an educated guess. an engine dyno is the only sure way to tell.

 

 

Beautiful work there Scott. I just really hate the stock backbox its restrictive as hell!

BTW my n/a auto made 200 rwhp this summer compared to the 150 it put down on the same dyno winter 2009 and 90K kms ago so those headers really work.

 

 

Trust me OBX, second decat and that piping following the original lines but removing boxes is not restrictive. The box was. Until I did around 100 miles and blew the baffles out. It's definitely not restrictive now. Ran 206bhp on the Dyno the other week

 

Thanks for the compliment. Wanted something different. Sticking with it at nat too to deliberately be restrictive and keep boost down.

[garethr]

It's about 30 bhp more . . . a Catless 7M-GE produces 200 bhp, a Catless 2JZ-GE I figure about 230 bhp

 

But yes, that's the conclusion I started to come to before even posting on here, that although quite SIMILAR, the engine differences are why there's the extra noise ! But it's good to get feedback from you guys who know this engine.

 

I think most people would think I'm being too fussy . . . even more would probably say the exhaust sounds BETTER with this engine !

 

At the end of the day I guess I've done pretty well, as this exhaust modification cost me £30 . . . to have a custom exhaust made would probably cost more than I've spent in total on this 2JZ engine transplant!

For some reason I had 7M-GE - 170 bhp in my head.

[Guest Roger NE]

Many thanks for all the comments/advice chaps.

 

without exhaust scavenging you will be loosing some low and mid range tourqe but should still make more than having the stock cat in

Incidentally, on the Mk3 the main cat goes where that first box is in the photos (the Cat version of the downpipes end in a flange at that point). My car originally had a Cat, and I simply removed it about 10 years ago by by-passing it. But I did notice a loss of low end torque. I then discovered that Toyota fitted a different front section for the non-cat models - the front box is there to replace the Cat. It's not a silencer (people who've taken them apart say they're not at all restrictive), but it's there to provide the back-pressure the engine expects. So that's what I fitted back then (still readily available from exhaust centres in the UK), and that's what you see in my photo. The 7M-GE was certainly much better with this box in!

 

That's why I figured this system would work OK with the 2JZ-GE engine. But I suppose it's a different engine, and it's expecting that box much sooner after the manifold.

 

By the way, the rest of the stock exhaust system on the Mk3 doesn't split in two and then re-join, it's just one single exhaust line, with a main silencer and a back box with two pipes coming out. However, being a longer car, it's fairly straight (doesn't zig-zag around like the Mk4 exhaust)

Edited January 26, 2014 by Roger NE (see edit history)

[Guest Roger NE]

So is it the Cat that reduces the noise? Or the fact that the two pipes join together really soon after the manifold?

 

If I fitted a s/h first cat, and could knock the innards out so it's not restrictive, would that reduce the noise, do you think?

 

I guess I could then have a single pipe that goes from the flange on the back of the Cat all the way to the flange at the back of box in my picture (ie doing away with that my existing first box, as well as the twin downpipes).

 

But I imagine that pipe would be quite expensive to have made up! (certainly a lot more than the £30 it cost me to have my current adaption made). Wonder if it would be worth it?

[Guest Roger NE]

Was hoping someone would answer my questions . . .

[Chris Wilson]

Catalytic converters certainly reduce noise, they make very effective silencers.

[Guest Roger NE]

Yes but the noise doesn't actually come out the end of the exhaust system, so my silencers are doing their job OK . . . it's the noise of the exhaust gasses rushing down the downpipes that I'm not really happy about !

[Chris Wilson]

Some folk worry too much. It's when you don't hear combustion expansion you need to worry