Exhaust Sizing

This definitely seems to be the best thread on exhaust for the 1UZ out there since it actually has some quantitative information in it.

I have put a 1UZ in an 84 4runner and am looking for the best exhaust setup. It is NA with stock ECU etc... I may throw a SC on it with 5PSI in the future, but that's about it.

From what I'm reading, it seems 2" from the headers until 'Y' and then 2.5" from there to the muffler and out. It seems the sizes would be sufficient even with the SC on top at 5PSI according to the information provided above. I am running the stock SC400 manifolds.

I have been recommended to put a resonator on each side after the down pipe to help quiet things a little bit. I do not have any smog restrictions. What are any thoughts on this?

Would it be better to make longer 2" runs and make the 'Y' right at the transmission output area or would it be better to make the 'Y' closer and run the pass. side exhaust under the bell housing area?
 

Mat Grant

Member
Hi all,

Update from me as I've finally got my exhaust made. The car is a 1970s Lotus, a pretty light car with backbone chassis and fibreglass body. My goals were, a quiet exhaust (well not not stupidly loud) as I want to go places in the car, it's a road car not a track car. I want a drivable engine with good throttle response. As my car is old the noise for the MOT (UK version of the inspection) is not very strict, it can still be pretty loud and will pass as long as the exhaust is intact and secure etc. It was more about wanting a car that is nice to sit in for a long drive....

The car will start stock engine and stock ECU, but will be adding a centrifugal charger in the longer term.

From reading the advice on here - lots of useful stuff (thanks Mr Gloverman), and talking to the guy fabricating the exhaust, I have gone with the 2" soarer manifolds (this was a must for space reasons and heat shields were useful) ito a Y pipe / merge with 2" in and 2.5" out and the rest of the system is 2.5" single, two boxes to get the noise down.

Once I've driven it I'll let you know - but I'm expecting it to be better than the 4 cyl 2.0 litre Lotus engine that I took out of the car.....

I'll attach some pics.

Mat.
 

Mat Grant

Member
Yes - I was looking for as quiet as possible without being too restrictive. The reason for that is I want to drive places in this car :) And although it's funny for a bit having a really loud exhaust, it gets annoying after a while! The car is fibreglass so doesn't damp the sound very much.

Plus if I want a cool sound I have an RGV500 (google it)

Mat.
 

Mat Grant

Member
Yes I see what you mean. What boxes and pipe sizes would have made it "cool" sounding? I did ask the question on here several times and in other places.....

As long as it is quiet I will be happy, because there is no room for any more boxes!
 

George_R

Member
Key point here is that the UZ, especially vvt ones, are silent engines by themselves. So you can use things that are known as loud

In your car, you could install 2in-2 out straight through muffler (thus retaining the v8 sound note) which and still be ok with the sound level
 

George_R

Member
Y-pipe makes the sound more mellow, smooth, mean, some may even consider it dull. It eliminates v8's rumble to a great degree. The dual in/dual out muffler is just another compromise between sound degradation and space/weight/etc restrictions (compared to true dual system), it's just biased towards better sound "quality". Both systems can be made silent or loud, depending on pipe size and muffler design.
 

Mat Grant

Member
Thanks for the reply - I was told by quite a few exhaust people, including reading a few posts on here that the Y pipe was important to getting good midrange and throttle response. And that the stock Y pipe was a good design, unfortunately that wouldn't fit on my car. But the response was way more important than the sound to me.

I definitely don't want the car to rumble! I'd like it to be quiet - That might sound weird to most people on here, but the priorities were loosely in this order:

1. Fits in space available (not much on this car) and ground clearance (even less - it's a lotus)

2. Passes MOT (inspection)

3. as light weight as possible

4. cost - cheap as poss but still good quality, and made of stainless steel (even though it doesn't sound as good)

5. unrestrictive as possible, best throttle response / midrange

6. quiet as possible (without overly compromising the 'unrestrictive' above) especially inside the car - if louder from behind (like my soarer v8) that's ok, but I've been in lots of cars with loud exhaust noise inside the cabin, however "great" it sounds, it soon pisses me off!

The "tone" of the sound is below all the above criteria in importance - might not be for other people, but is for me.

Mat.
 

George_R

Member
That makes sense, but rumble doesn't mean loud as hell. I rather mean that the sound might be not so mellow like you typically expect of inline four or six.
Currently, H-pipe does make so much difference to me compared to Y-pipe (and most of the difference is in light throttle / midrange zone). My current setup is still far from perfect and is louder that I wanted it to be, so of course I can't recommend it for your application. But I think you will benefit from x-pipe and double in/double out mufflers, and non-straight-through resonators
 
Last edited:

fastegg

Member
I am uncertain of your goals. It sounds like the stock system is OK and you maybe want more "sound"...

I would not recommend changing the stock duals to a single. The dual pipes allow much more muffling area.

Have you tried the muffler delete? Simply remove the rear two mufflers and drive the car. I will be louder but not loud. If you like this you can simply have straight 2" or 2.25" pipes installed instead of those two mufflers. This will slightly quiet the already minor sound change. Alternately keep the final two mufflers and replace the middle two mufflers with straight 2" pipe. A third option is replace the middle two mufflers with straight through round resonators in 2" with straight 2" pipes from there to the back bumper. If that is too loud for your tastes you can simply add straight through or turbo style mufflers back where the final two mufflers were.
Hi JBrady.. I took out the rear 2 mufflers.. sounded pretty good, quiet but can hear the V8 only a tiny bit of drone but acceptable. I drove round for a few days like that.. I'd still like to go 2.5" single after the front resonator... however the car has Western Australia rego and has to have full blue slip inspection to get NSW rego and most likely will not pass with a 2.5" single. (It has to be under 90db) So I finished up running straight pipes from the 2 center mufflers to the rear of the car.. Its got a nice quiet V8 sound... It will do for now.... :)
 
Top