Exhaust query -shape

With all the exhaust dramas people have been having lately, I thought I'd ask a question for the boffins.

Now, we all know people tend to get 3" or 4" exhausts. The problem with 4" being a) the noise and b) the ground clearance.

Now, I was wondering if, rather than having a round pipe exhaust, how an oval pipe exhaust would be.

Now, I know it's all about cubic area for restrictions and allowing as much gases out though the exhaust as possible, but has anyone gone the route of a custom oval pipe exhaust, to get over the ground clearance issue?

And, what kind of dimensions would the oval pipe need to be to match say, a 4" exhaust?

When it comes to the back box, would it be possible to customise one so that the oval pipe went into the round pipe of the back box, as long as the cubic areas match, without then limiting the flow? As I think to have an oval back box would be a custom job?

Discuss

Oval pipe is a bitch to bend

My Drager pipework is 95 mm and i don't get many problems and the car is lowered on Eibachs, its

also not that loud

As it would be a custom job, would it not be ok to cut and weld it to the correct shape?

I don't really know exhausts would angular bends apposed to rounded bends make a big difference?

I'm thinking from first decat by the way, to allow plenty of ground clearance.

More trouble than it's worth IMO. Just buy a decent exhaust to begin with.

The point isn't the exhaust itself, it's about gaining ground clearance and still allowing the same flow rate as a 4".

I have some horrendous speed bumps in my area, and my 3" catches on half of them already.

would angular bends apposed to rounded bends make a big difference?

Yes. You want it as straight as possible. Any disturbance in gas flow can cause back-pressure which will cause power-loss issues.

would angular bends apposed to rounded bends make a big difference?

Yep. An exhaust (in theory) will only flow the maximum of it's narrowest point. An angular bend in 4" might knock it down to 2.5", therefore you have 2.5" (e.g. restrictor rings).

Mandrel (round) bends keep a constant radius in the pipework.

The point isn't the exhaust itself, it's about gaining ground clearance and still allowing the same flow rate as a 4".

I had a Whifbitz twin box system on my old single Supra and it was perfect. My car was very low.

Yep. An exhaust (in theory) will only flow the maximum of it's narrowest point. An angular bend in 4" might knock it down to 2.5", therefore you have 2.5" (e.g. restrictor rings).

 

Mandrel (round) bends keep a constant radius in the pipework.

Ah, I see.

Thought there must be a reason I haven't seen it done.

Why do you need a 4inch exhaust anyway? Not needed unless your running mega power just stick with 3-3.5inch

4" oval with 3.5" cut out.

http://imageshack.us/a/img197/6589/dscn1270q.jpg

When you mess with oval you need a top fabricator, simple as that.

Why do you need a 4inch exhaust anyway? Not needed unless your running mega power just stick with 3-3.5inch

This.

If you're going for over 650bhp, then I think you'll need 4", under than you'll be perfectly good with 3"

This is all just for future plans really. Not for what I have now

Ground clearance of an oval cannot be matched and the flow is more or less the same as a normal 4" exhaust. As I said though you need a very good fabricator as it's very easy to get it wrong.

This is all just for future plans really. Not for what I have now

In that case I would say go 4 inch exhaust when/if you actually need to. No point doing it now especially if you current exhaust already catches. Chances are by the time you actually need the 4 inch exhaust you would have probably damaged/dented it which will restrict it anyway;)

Not worth the hassle. Raise the car up. If you have to. Im changing my exhaust and I have bumps as well (like you know mate when you crashed into it when you came to visit) but I'll sort the issue if there is one rather than pay ££££££££££ to keep it 10-30mm lower.

You won't want 650bhp on a car that's too low anyway. Handling will be aweful if it's too low, more power will make it harder and less enjoyable.

This idea wouldn't be followed up for a while yet. Not until the rest of the bits have been sourced.

@Noz that pot hole was horrendous lol

This idea wouldn't be followed up for a while yet. Not until the rest of the bits have been sourced.

 

@Noz that pot hole was horrendous lol

Sounds good mate look forward to the updates. Nothing wrong with asking questions and planning ahead:)

My thinking exactly mate.

Probably wont happen for a couple of years yet lol but collecting parts as and when the money is there and bargains come up. I'm in no rush to go single, but trying to gather all I can bit by bit.

Plan on getting a second engine at some point, so I can build it outside the car. That's last on the list though

3" off the shelf exhaust, job done.