2JZ-GE Exhaust Noise

[Guest Roger NE]

As some of you may know, I recently fitted a 2JZ-GE in my Mk3 Supra.

 

The 7M-GE engine I replaced looks very similar . . . and the Mk3's stock exhaust system has TWO separate outlets on the Manifold (similar to the 2JZ-GE), except they continue much further before they join and then enter EITHER a Cat, OR first box (which replaces the Cat on the Non-Cat versions)

 

I figured that if I got the 2J exhaust cut and welded to the 7M stock exhaust it would work fine AND get rid of the 2J's Cat - in this photo you can see the stock Manifold & downpipes of the 7M-GE (top) and my modified 2JZ-GE version underneath

 

http://www.wessexprod.demon.co.uk/supra2jz/exhaust3.jpg

 

The rest of the exhaust, by the way, is the stock 2.5" system used on the Mk3 N/A AND Turbo cars, a main silencer, then a tail silencer with twin exhaust pipes out the back. (so I have 3 boxes altogether)

 

Being exactly the same exhaust system as on my old engine, I figured the exhaust noise would be much the same with the 2JZ-GE . . . but I'm disappointed that it's MUCH louder ! Not from the back, but from the front, so you really hear it inside the car.

 

At first I thought I must have a leak, but I can't find one (plus manifold leaks usually sound quite distinctive, and it's not like that) . . . it's OK on tickover, but as soon as you blip the throttle there's a kind of ROARING noise of the gasses going down the downpipes.

 

Basically, I'm hoping someone can tell me is this NORMAL, or do I have something wrong?

 

I suppose the nearest comparison would be someone who's fitted Headers to their 2JZ-GE . . . do you get a similar roaring sound from the downpipes?

 

And that having the original 2J system of the two pipes joining almost straight away in the Cat stops this from happening?

Edited January 23, 2014 by Roger NE (see edit history)

[Dan_Q]

the stock mkiv has 2 cats- the first is the shorter y piece you describe, which takes it from 2 into 1, then there is the second cat directly behind that.

 

I've not done it myself but just double decatting a mkiv GE even with a stock exhaust apparently makes it very loud, I assume that's the sort of noise you are getting unfortunately.

 

I'm sure someone with more of an idea will be along soon.

[David P]

The 2JZA80-GE has a very noisy exhaust.

 

I think you'll find those long secondaries are preventing noise being buffered from merging with gasses from other cylinders.

[Guest Roger NE]

I would have thought it would be more efficient? (quite apart from not having any Cats, just like with my 7M-GE engine)

 

But I really never expected the noise . . .

 

Maybe someone else who has de-catted, or fitted Headers can advise?

[David P]

 

Maybe someone else who has de-catted, or fitted Headers can advise?

 

What makes you think I haven't done both?

 

Check your not a grommet missing in the firewall.

[Guest Roger NE]

Check your not a grommet missing in the firewall

 

I hadn't really thought of that . . . the only "hole" I have altered is obviously removing the 7M Engine Loom, and feeding the 2JZ one through . . . and to be honest it's not sealing as well as it should, as I can't get a drill in there without removing lots of stuff to bolt it in place. (the 7M one was just a big grommet, whereas this one should bolt against the bulkhead to get a proper seal)

 

So that may be making it a bit worse . . .

 

But the noise when you sit in the car with the door open and blip the throttle is MUCH louder than it was with the 7M engine

 

What makes you think I haven't done both?

 

So are you saying that's what you would expect with this setup? ie I probably haven't got any manifold or exhaust leaks at all?

Edited January 24, 2014 by Roger NE (see edit history)

[Ian C]

Is the new exhaust the same material and wall thickness as the stock one? If it's a less dense material and/or a thinner wall, you'll probably get more sound out of it.

[Guest Roger NE]

The new exhaust IS the stock one . . . the same as was on the car before the engine swap

 

Just the two downpipes have been cut and welded to the two 2JZ downpipes (as you can see in the photo)

Edited January 24, 2014 by Roger NE (see edit history)

[GMan]

I intalled obx headers and a 3 inch exhaust with straight through decat mid pipe and hit 126db at wot. I have been leaving the bung in 90% of the time. in response to your question. Yes the headers make much more noise. your problem is using the really short stock primaries with too long secondaries. the stock setup relies on scavanging the front 3 cylinders from the back 3 and vice versa at the first cat which cuts down on noise hence the almost nonexistent primaries and super short secondaries. an aftermarket uses longer primaries to alow the front 3 and back 3 to scavange of each other. longer secondaries ( but shorter than the primaries) allow the front to back scavanging. This gives you better ve and noise cancellation. With your exhaust you have exhaust pulses traveling in isolation all the way until under the car causing resonance and that is the rushing sound you hear.

[Dan_Turism0]

My Supra with both cats still in place.....horribly loud!

 

[Ian C]

The new exhaust IS the stock one . . . the same as was on the car before the engine swap

 

Just the two downpipes have been cut and welded to the two 2JZ downpipes (as you can see in the photo)

 

What the heck's in that picture then? You said "in this photo you can see the stock Manifold & downpipes of the 7M-GE (top) and my modified 2JZ-GE version underneath", the bottom one looks brand spanking new and a different design to the top one, so it's not the stock 7M one, or your old one, and not a stock GE one as then you wouldn't have had to cut and weld anything... Anyway, before you get all ragey and capitals at me, what I said still stands. If it's not relevant, that's fine, I have no other suggestions

[Guest Roger NE]

Many thanks for all the comments guys . . . much appreciated

 

What the heck's in that picture then?

 

They are/were two identical stock 7M-GE front exhaust sections (I had a spare one in my garage - it looks new because I sprayed it with high-temp aluminium paint before fitting)

 

The top one is bolted to the 7M-GE manifold . . . the lower one has been cut and welded to the 2JZ-GE downpipes (where they normally go into the Cat), to make it fit the new engine. (I took both to the exhaust guy who did the welding, so he could use the top one as a template to get the dimensions right, as he obviously didn't have the car)

 

What I meant was that the whole exhaust system is basically identical to what I had on my 7M-GE engine (an OEM/Stock system for the Mk3)

 

(and I wasn't getting ragey or shouting at you Ian . . . just trying to explain. I use capitals just to STRESS a particular word)

 

With your exhaust you have exhaust pulses traveling in isolation all the way until under the car causing resonance and that is the rushing sound you hear

 

Appreciate the explanation GMan. I'm no expert on exhausts by any means, but I do understand the Physics of Standing Waves and Resonance, etc. I guess you've confirmed that I don't have any leaks then, and that it's bound to be fairly noisy.

 

I wasn't trying to design some special exhaust . . . just a really simple (and cheap!) solution to making my stock exhaust fit the new engine. I figured that it would work OK as the two engines are very similar.

 

I also thought that it would be reasonably efficient, getting rid of the 2JZ's cat - do you think that's the case?

Edited January 24, 2014 by Roger NE (see edit history)

[skippyboyo1]

I have a custom manifold in to a middle box in to a back box and out. 2.5 inch and mines not too loud.

 

Get a custom system, you won't regret it.

[Guest Roger NE]

I have a custom manifold in to a middle box in to a back box and out. 2.5 inch and mines not too loud

 

I doubt if any of you would consider my exhaust at all loud !

 

It's just that it was VERY quiet with the 7M engine . . . and I guess I expected it to be the same when fitted to the 2JZ.

[garethr]

Doesn't the 2JZ produce 50+ more bhp than a 7M? Perhaps it's as simple as more power = more exhaust gases = more noise?

 

Also, would the cam timing and overlap change the sound? Not forgetting that the 2JZ is square (86 x 86) and the 7M is undersquare (83 x 91).

[Guest Roger NE]

Perhaps it's as simple as more power = more exhaust gases = more noise?

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!

Edited January 24, 2014 by Roger NE (see edit history)

[GMan]

the 2jz head flows miles better than the 7m. in the time between them toyota learned alot about resonance tuning. the intake acoustic control valve being a prime example. I am sure that the exhaust gasses exit the ge head faster and with more energy. the 7m also has longer primaries than the 2j with more bends less power = less exhaust gasses @ lower velocity. The long straight pipes is where all your noise is comming from.Your custom exhaust does the job for little money so good work there. if or when you have the time/money/desire look into the obx header for the ge you will get some good power out of it and less resonance. with your skills fabbing a mid pipe to fit the rest of the exhaust will be easy.

[scott87]

the 2jz head flows miles better than the 7m. in the time between them toyota learned alot about resonance tuning. the intake acoustic control valve being a prime example. I am sure that the exhaust gasses exit the ge head faster and with more energy. the 7m also has longer primaries than the 2j with more bends less power = less exhaust gasses @ lower velocity. The long straight pipes is where all your noise is comming from.Your custom exhaust does the job for little money so good work there. if or when you have the time/money/desire look into the obx header for the ge you will get some good power out of it and less resonance. with your skills fabbing a mid pipe to fit the rest of the exhaust will be easy.

 

Just as a heads up the obx manifold/header makes one hell of a noise. Its great, but it is seriously loud!

[Guest Roger NE]

Well I know the 2JZ is a better engine all round . . . mainly in terms of reliability . . . that's why I fitted it ! Plus I knew I could do the whole thing very cheaply . . . the whole job only cost me £500 with EVERYTHING !

 

However, my Supra is not a hobby (the transplant was just to keep it running reliably) . . . I just need a car that looks reasonably impressive to new clients. But unfortunately I'm struggling with my business at the moment, so my priority is my family and paying the mortgage . . . so I doubt if I would ever splash out on a set of headers (and especially if they're noisy too!)

 

So are you saying that although it's noisier than I was expecting, this simple exhaust mod should be working pretty efficiently?

Edited January 24, 2014 by Roger NE (see edit history)

[GMan]

Just as a heads up the obx manifold/header makes one hell of a noise. Its great, but it is seriously loud!

Yes it does! More db just not that rushing sound the op was complaining about. Gives it a nice sound at high rpm

[scott87]

Yes it does! More db just not that rushing sound the op was complaining about. Gives it a nice sound at high rpm

 

Sorry misread the earlier bit.

 

The obx gives a really nice mechanical kind of rasp, not the jap bean can type of noise. Really improves low end torque too, or feels to....

[Guest Roger NE]

Don't get me wrong, the noise isn't NASTY . . . for example, I've never bought a Stainless Steel exhaust for ANY car I've owned, as I've always hated the tinny sound they have . . . the noise from the downpipes is actually quite throaty, perhaps because it's quite thick steel. It's just that I didn't have it before, so didn't expect it! (with the 7M engine, this exhaust was as quiet as a new BMW)

 

You didn't comment whether you thought that what I'm using should be reasonably efficient?

Edited January 24, 2014 by Roger NE (see edit history)

[scott87]

Don't get me wrong, the noise isn't NASTY . . . for example, I've never bought a Stainless Steel exhaust, as I've always hated the tinny sound they have . . . the noise from the downpipes is actually quite throaty - just something I didn't have before, so didn't expect it! (with the 7M engine, this exhaust was as quiet as a new BMW)

 

I think if you have always stayed clear of tinny exhaust then keeping near stock with an obx manifold will give you an awesome result. its pretty much what i did and the noise my car makes is immense. I did this:

 

[trebor69]

I have a whifbitz 1st decat and my 2nd cat back on, had the whifbitz 2nd decat and the OBX manifold/1st decat and it was too loud, girlfriends neighbours complaining all the time, I still set car alarms off now (and there is quite a bit of in cabin noise) but it performs better lower down and it is quieter .....not much though and the girlfriends neighbours are still complaining ....but they complain when my bike is ticking over too

[GMan]

Don't get me wrong, the noise isn't NASTY . . . for example, I've never bought a Stainless Steel exhaust for ANY car I've owned, as I've always hated the tinny sound they have . . . the noise from the downpipes is actually quite throaty, perhaps because it's quite thick steel. It's just that I didn't have it before, so didn't expect it! (with the 7M engine, this exhaust was as quiet as a new BMW)

 

You didn't comment whether you thought that what I'm using should be reasonably efficient?

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.

I think if you have always stayed clear of tinny exhaust then keeping near stock with an obx manifold will give you an awesome result. its pretty much what i did and the noise my car makes is immense. I did this:

 

http://i588.photobucket.com/albums/ss321/langers_2004/IMG_0048.jpg

http://i588.photobucket.com/albums/ss321/langers_2004/IMG_0046.jpg

http://i588.photobucket.com/albums/ss321/langers_2004/IMG_0049.jpg

 

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.