Single Turbo Exhaust System

[1UZ-HZ]

What would be the best system for a single turbo set up? The turbo will have a 4inch dump pipe and 4 inch catalytic convertor, but I'm not sure where to go after that, the car is goin to be street reg'd so I need something fairly quiet but also free flowing. Here's what I can come up with so far:
1) Single 4 inch all the way through
2) Single 3 inch " "
3) Twin 2.25inch from cat back
4) Twin 2.5inch " "
5) Twin 3 inch " "
Any help would be appreciated
Thanks
Jeremy

 

[88Alltrac]

This really depends on the turbo and how much power you want to make. A single 3" can flow enough for almost anything you will throw at it but if you are using a 4" dump-tube you might as well just run full 4" with a non-race type muffler to quiet it down. I've been looking into truck mufflers and such.

-Steve

 

[XR8tt]

On my 330 Ford twin turbo[twin Precision SC61/3's] , with single 3" it maxed out at 380 rwkw...We fitted two 3" all the way from turbine housing.. It spools faster, so far 440 rwkw....The fuel pumps can't keep up now....Happy with that for street car....

 

[stevechumo]

It seems to me you only run mild boost for a street car, so I'd go for a 3". A single 3" can make well over 500 rwhp guaranteed. It might not be the 3" diameter when you can't go past it. It might be other factors such as the turbo sizing & tuning...etc. A 3" will eliminate some of other problems for you such as the available room & noise.

 

[JBrady]

On my 330 Ford twin turbo[twin Precision SC61/3's] , with single 3" it maxed out at 380 rwkw...We fitted two 3" all the way from turbine housing.. It spools faster, so far 440 rwkw....The fuel pumps can't keep up now....Happy with that for street car....

This is a very good example of the VARIABLES that effect any system.

I do not know what the record for RWHP on 3" exhaust on a turbo car is BUT I would think it is much higher than 380rwkw (510rwhp).

So, why would it become the limit on this car? I am not certain but if he was joining two 3" pipes from the turbos to a single 3" then the transition becomes a restriction.

Think of it like water into a sink. Turn the water on full open and many drains will not keep up as the water splatters and rolls. Remember the pipe feeding the faucet is smaller diameter than the drain and the pressure is higher in the feed pipe. So, in this simple example it is clear that the water is not transitioning efficiently. Same applies to gas flow. An efficient system can flow more than a less efficient larger system.

Building a highly effective system takes knowledge and R&D.

You have a 4" downpipe and want to run a 4" catalyst. Why this size? is the outlet actually 4"? What is the actual turbine outlet size?

Since you want a "street" system you can either go single 3" for up to 500rwhp or you can run 3" into twin 2.25" pipes or even 2.50" pipes. The twin pipes are easier to fit and provide more choices and location for mufflers if you wish to be quiet. You could also run 3.5" from the turbo to twin 2.50"s. A single 4 inch is more than dual 2.5s (apx 12sq/in vs. 9.5sq/in) so this could create a restriction. Again, design particularly in the transition areas is where efficiency is gained or lost.

 

[stevechumo]

...So, why would it become the limit on this car? I am not certain but if he was joining two 3" pipes from the turbos to a single 3" then the transition becomes a restriction....

Very good. It's just pure physics.

 

[JustenGT8]

The last part of my system is 4 inch and then down to 3.5 inch with a large (custom made) straight thru barrel muffler. Nice mellow exhaust note and no probs laying down over 500rwhp.

 

[XR8tt]

It wasn't designed that way..It was fitted up to my old n/a system.. Besides on a 330 ci engine it may choke at higher rpm...380 rwkw is closs enough to 500 h.p anyway...
Strange enough the turbo's spooled way earlier and made turbo's sound much quieter...Our cars have plastic fuel tanks so one pipe down each side of diff cannot be done..They need to crossover to one side.. I eventually made my own muffler with 2 X 3'' inlets and outlets, no room for two single mufflers....
http://s4.photobucket.com/albums/y146/EBXR8240/?action=view&current=DSCF0240.jpg

 

[mdcmotorsports]

3" twin exhaust comming off the 4" down pipe.

 

[XR8tt]

3" twin exhaust comming off the 4" down pipe.

Yep it will still have a v8 note to it ....Nice !!!!!!