Thread: D2 Dual Exhaust Sizing

I'm not sure that size is needed,,
If it was my money,,
I'd probably go with 1 and 3/4 duals,,
but its not.

How long are the secondaries? this is where your torque is made,,

Originally Posted by Pedro_The_Swift

I'm not sure that size is needed,,
If it was my money,,
I'd probably go with 1 and 3/4 duals,,
but its not.

How long are the secondaries? this is where your torque is made,,

I have no experience with 4wd exhaust systems.

Refering to a sizing chart by one of the exhaust manufacturers (very general and broad information) for a 4.0litre V8 single system recomend a single between 2.5" - 3.0" and on a dual system 2.0" - 2.5".

The headers, not exactly sure but from rough measurements on the computer screen the primaries and secondaries both appear to be around 450mm long.

Little update on the dual exhaust for the D2.

I have finally got around to pricing a system and it is not too bad.

I am going to run with;

Pacemaker Headers
2.25" High Flow Catalytic Converters
2.25" Dual Inlet / Outlet Muffler
2.25" Dual Tail Pipes outletting through the rear bar just inside the passenger side lights.

For anyone who is interested;

Pacemaker Headers $865
Hurricane Headers $765
High Flow Cats $300 each
Ceramic Coating of Headers $500

Cat back dual system with muffler $660 Press Fit or $800 Mandrel Bent.

Obvioulsy the price would be a little less for a single system, but if you are after a cat back system, I would think those prices are pretty good.

Further information on Ceramic Coating

Headers inside and out with black triple coat (30-40% heat reduction) $360

Cat black triple coat outside, muffler black coat outside and dual pipes black coat inside and out $400.

This includes sand blasting, degreasing and coating, total of $760 for full system in black.

Just my 2 cents worth here.

2.25 on the dual pipework sounds a little big. Essentially you're creating an outflow from the dual pipework of 4.50, which may result in lost back pressure; translating to lost torque.

If it were me doing a dual pipe setup, I'd go 2.5 for all of the single pipework and then 1.5 or 1.75 at the dual outlets.
The smaller outlets will also help in cutting down one hell of a noise that might otherwise be produced by the dual 2.25's.

As a comparison, I'm still running std D2 exhaust post conversion, except it's recently lost it's cats. Post cat removal dyno showed more power and torque, exhaust flowed better, emissions same as previous (cat incl) dyno plus it's a lot of kg's lighter.

When I built the last 4.7 2UZ toyota we only ran a 3" as it came from ebay at the right price. We were running 52mm ITB's and certainly flowing more than any rover ever will when you consider it would see 14000 + rpm.

Originally Posted by clubagreenie

As a comparison, I'm still running std D2 exhaust post conversion, except it's recently lost it's cats. Post cat removal dyno showed more power and torque, exhaust flowed better, emissions same as previous (cat incl) dyno plus it's a lot of kg's lighter.

When I built the last 4.7 2UZ toyota we only ran a 3" as it came from ebay at the right price. We were running 52mm ITB's and certainly flowing more than any rover ever will when you consider it would see 14000 + rpm.

So you're running no cats at all in your Y pipe? Which exhaust place did that for you without taking the legalities of running without any cats into consideration?

Originally Posted by Sully

Just my 2 cents worth here.

2.25 on the dual pipework sounds a little big. Essentially you're creating an outflow from the dual pipework of 4.50, which may result in lost back pressure; translating to lost torque.

If it were me doing a dual pipe setup, I'd go 2.5 for all of the single pipework and then 1.5 or 1.75 at the dual outlets.
The smaller outlets will also help in cutting down one hell of a noise that might otherwise be produced by the dual 2.25's.

I do agree on a 4.0l but when it is 5.0 - 5.2l with stage 3 heads I believe the size should be about right.

Also, dual 2.25" exhausts is equivelant to the area of a single exhaust around 3".

The standard single exhaust on my D2 is a size just over 2.5", so the dual 2.25" is not that much larger in reality and should match the future engine work better.

I still need to talk to the exhaust shop about those exact issues though regarding loss of torque, but with the new heads, larger capacity and new cam I think it will be a good match.