Exhaust pipe sizing, sound vs. low end power?

[George_R]

Recently I occassionally obtained the sound I was always willing for. I'd like to ask if I can reproduce the sound with more 'normal' configuration, and with less degrading of engine performance.

Long things short, I had to run fully stock 1uz-fe vvti for extended period in workshop, so I fabricated appropriate air vent system. Overall, exhaust was like 2.5" pipe down each header, a 12" glasspack on each pipe, then Y-piece into 3" pipe connected to 3.93" air vent pipe 20 feet long, with a fan at the end of it.

What I liked about the sound is it was reasonably loud and rich in middle frequencies (not only lows). It also featured some popping under load, the thing I would expect only from bigger displacement engines. At the same time there were no slapping or popping like one may find in old school V8's - the sound was a tad smoother, with no high frequencies either. Of course, all of these effects were gone after fitting more 'normal' exhaust to the car after the conversion was done, it became dull and silent as planned.

So the question is, can I obtain the same thunder-like sound with real world pipe lengthes and diameters, while not sacrificing engine performance to a great extent? What are the key factors to consider?

 

[LEXUSA]

So you had OE exhaust manifolds, 2.5" pipe from there with a short glass pack muffler on each side, merging into a 3" pipe.

Diameter and length influence power and sound. Keeping the diameter the right size to start out with and stepping it up in size over the right lengths improves power delivery curves and usually sounds better, more tuned if you will. At least in my opinion.

Are you going to stay with the OE exhaust manifolds or run/make headers? What vehicle is the engine going to be in? Will you be running the OE catalytic converters? The system you detailed above is overly large for making low end torque and probably didn't really do much for top end power.

 

[George_R]

Thank you for the reply, let me go into details

Firstly, all the setup described above is merely occasional/unintentional experiment with a customer's car. I just noted how unusual the sound became after replacing everything after the Y-pipe with a long and wide air vent pipe .

You're right about the exhaust configuration, except for the extractors - I forgot to mention I always use OE 2UZ-FE manifolds because I can weld them in case of tight fit. And I should have said 'generic inexpensive hot dog style muffler' rather than 'glasspack'.

Regarding my own car, I'm pretty free with exhaust design, with some notes however - I will use 2UZ-FE manifolds, and I'm highly biased to having single exhaust pipe on the RH side (LH side has fuel lines)

I'd just like to copy that unusual sound which I got with the air vent pipe, if only I can fit everything needed under my car. I will be fine with sacrificing some power/torque or both for having the better sound.

My guess is that the air vent pipe is highly restrictive by its nature as the engine has to push a decent amount of air stored in it. Its sound is very similar to that of big displacement V8 boats, having exhaust pipe submerged into water.

As for my car, it's 1970 model, 1990 production, and it's already fitted with 200hp 1jz-ge and 5-speed auto.

It just needs more bottom torque as n/a 1jz has none.
I have completed a number of vvti 1uz conversions already, but I never paid too much attention to exhaust because everything needed was nothing more than a quiet note.

 

[George_R]

p/s just found some video with the sort of sound I'm after
http://youtu.be/QkMHzQZDjpc

 

[BlackUZZ31]

this is what i have with two 2.5 lukey race mufflers into a single 3 inch lukey race...
http://www.youtube.com/watch?v=BQlVRGlOaFU

Excuse the "I ran out of gas for the MIG" welds...

 

[George_R]

BlackUZZ31 it may be the record quality itself, but I noted heavy bass domination in your sound, without much presence of higher frequencies, it's like the sound comes out of some box, well to my taste. I'd like a more 'open' note. But thanks anyway, that's a good example what I may expect to get with 2.5" into 3"