just made myself a 3.5" exhaust system for my shonky saff. it's a damm tight fit.

 

damn - thats massive

must release a few more ponies surely

 

tony measured the back pressure in my old front pipe and advised me to fit a 3.5" front pipe. so i'm goin to make a 3.5" system with side exit pipe or pipes.

 

How much back pressure was there, and how much power are you making ?

 

wicked work

 

as this man said, i run a 3" full system on my xr2, how much power are you running?

 

Starts to be restrictive at 660+ bhp. We were on 3" at 720bhp & cracked you know what so not that restrictive .

 

To much and not enough. Lol.

 

What size exhaust do you run, Rod? 3.5 as well I'm guessing? Lol

 

That's what she said...

 

That's going to be 1 serious car

 

Can I ask where did you get the turbo flange from? I've been looking for one but cant find a supplier and I don't want to cut my mongoose one up.

 

Christ, that's a proper tight fit there. Good work! Hope its solid, because that's gonna be feckin' annoying if it keeps tapping the gearbox in corners

 

Nice work John, i'll be doing the same over winter, gonna be a mission doing it on a 4x4 and a massive skyline box in the way!

 

The thick steel flange I took off my old exhaust. The thin stainless part came from a mate that works at a aerospace company.

 

Oh yes its going to be a job and a half. Can you pm me where you got your fuel tank from please. Thanks john.

 

John, what box you got in that?!
Nice work on the exhaust btw.

 

get it heat wrapped, will dull down the sound it it bangs around.

 

The transition upto 3.5" is a bit crap aint it. Should have tapered it.

 

I've put a elite 6sp sequential in it now.

 

Thanks for your comment.

 

There is enough room around it. Hopefully. If it catches anywhere I'll alter it.

 

allthough the way he worded it could have been better, he isnt entirely wrong a taper would be far less restrictive than what you have on there mate

 

Please explain how a taper would be better than what I've done. I'm not against change if there is a better way top do it. I'm not a exhaust designer.

 

the lip on the 3" to 3.5" section will create a vortex and swirl the gas, this will cause a flow issue and hence not the best, whereas a taper is a controlled expansion of the gas and won't swirl the same, so more flow.

 

hey up,i am the man who made the flange adapter and the tube,if the turbo has a 3 inch housing and the adapter fits right up to that housing,then there is only 10mm of tube which is 3 inch then it goes into 3 1/2,if it was flowing the other way then a taper on the tube would of worked better,it is fiiting to a t4 turbo,so we are using the standard flange,thanx for your comment,i will keep it in mind when im making custom parts no one else is making

 

Not a very descriptive answer.

There are certainly few downsides to going bigger ( apart from hassle, cost and noise ). But it would seem a lot of effort if it isnt actually needed.

 

what im trying to say is,if the turbo housing is 3 inch and the flange is of the 3inch down pipe,then there was no other way of making the adapter,the adapter has a shoulder of around 12mm at 3 inch i/d,then it goes to 3 1/2.forming a taper would make no differance to the flow at all,if the turbo had a bigger housing then i would of made it 3 1/2 inch from the turbo

 

well i can cope with with the 3 downsides youv'e listed what are the other ones. ps thanks for your input.

 

what he said lol (i am an exhaust fabricator btw)

 

IIRC porkie had a 4" system made by now long gone tube torque in macclesfield, he had pics on here years ago showing the taper they made.
It might be worth pming him to see if he still has a pic

steve

 

The taper promotes a less dramatic pressure drop in an area which has been identifid as being problematic by testing on this very car.

Ever wonder why your making custom parts that no one else is making?

 

everyone a critic,trial and error,if it dont work we will try somthing else,

 

Great work, nice to see someone doing things right for a change

IIRC you can start to measure backpressure in a 3" system at something like 350bhp

rapidcossies sapph use to run a 3.5 or 4" downpipe (can't mind what size it was now and I wrapped the fecking thing today as it happens) splitting to twin 3" after the g.box

 

sooo what power are you running?

 

I don't know what power it will be I just know that when we checked the back pressure last time it was too much. The problem was either the front pipe or the silencer. I'm changing both so hopefully that should cure the backpressure issue. Who would like to design me a back box.

 

On a turbocharged car everything is about pressure drop. You WANT the pressure to drop across the turbine.
What he has done is probably better than a smooth taper.

And there is absolutely nothing smooth about what is exiting the turbine/wastegate.

It would be better still upping to 4" for the downpipe and then downsizing. As Rod as already suggested even around 6-700bhp, 3" isnt really much of a problem. Although again going upsize certainly wont do any harm.
But if you had only 4-500bhp or so, it would be a waste of time.

Back pressure in the exhaust really doesnt sap power as much as you think, unless it was silly.

 

ive just made my own 4" full system. its all complete but i have'nt got any pictures of it fully fitted yet because my downpipe is away getting wrapped.

 

You should be careful the string doesn't get wrapped around your driveshafts

 

I cant help thinking that a petrol container isnt the ideal support for welding up an exhaust lol