Bigger dump pipe and exhaust
Turbo Mini Forums

Howdy Lads,

I am considering running a bigger dump pipe and exhaust.
Currently its 2" from turbo back.

Issue is with my setup the dump pipe barely squeezes through past the pot-joint.

I am wondering if anyone knows if I use a 2.5" dump pipe but where it cant clear the pot joint I will use a 3" or 3.5" and squish it so its oval (to clear dump, but still have volume) and then back into a 2.5" exhaust.

Will increasing the dump and exhaust benefit me? I was told with turbo's bigger exhaust is usually better (obviously not a crazy 4" system)

Also, the exhaust manifold uses steam pipe and its small 1" ID (I think) or maybe 1-1/4"
Intercooler piping is all 2"

Would bigger pipes for intercooler help?
Bigger intercooler? (Currently using 300za IC with alloy tanks)

Its an 1132cc Turbo - running Hi-flowed Garrett T2 and currently making 106hp atw WITH a blown headgasket (blown in 3 places) fixed now.

Just looking for things to do I guess - 1. To make more bananas and 2. To improve whats there.

Cheers
Pete

1132cc Turbo ~120 bananas ATW - Fun Fun Fun

Hi,
I think you'll need to double your hp before you'll need to worry about that.
Cheers,
Gavin:)

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so dump and exhaust size wont affect it? 106 was with blown headgasket, its around the 120hp mark atw now (150+ at the crank)

If thats the case, I am happy though, no need for new exhaust :)

Edited by pristic on 15th Aug, 2008.

1132cc Turbo ~120 bananas ATW - Fun Fun Fun

Im going to try and change mine to 2.5" over the winter and was planning on doing the same as you descirbed, flatten a larger section of tubing so it still keeps the same cross sectional area. Got do some some maths for that though (im a bit rusty)! Lol

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1/4mile in 13.2sec @ 111 terminal on 15psi

i think cooling the air more effectively before it enters the carb will allow you to add more fuel resulting in more power..
*Bigger intercooler
*more efficient IC, more air (fan) better position etc..
*remove sharp bends in charge pipes.
*Porting compressor (cutting the inles to resemble a bellmouth rather than a seies of jagged steps
*One of those bespoke plenums you can get on here with a stub stack in it if poss.
*IC water/nitrous spray
*Welding up the internal wastegate that dumps waste exhaust back into the path of gasses exiting the exducer and somehow fit yourself an external item with a seperate dump pipe about 2 foot long..
JustMyTwoCents

you are running quite a high CR are you not? i think i remember reading your thread about your car and it being quite high.

i personally would be dropping the CR abit and adding a better, efficiently mounted IC then upping the boost.

what CR are you running? what boost are you running? Do you know your inlet temps (post IC) ? Megajolt?

i think you will see some nice improvements with the above before your exhaust becomes a worry. and before you need to change your downpipe i would have thought that you would want to go larger diameter primaries on the manifold.


EDIT: i just realised this is from freaking august!!!

Edited by James_H on 17th Sep, 2008.

I think I remember he was running a 9.4 CR at 16 PSI. It was something mad like that anyway

On 12th Nov, 2009 Paul S said:

I think Gary OS has taken over my role as the forum smart arse

Hey Lads, Yes, 9.4:1 and that was on 15-16psi

Holds fine and absolutely hammers. (Head Gaskets are the only issues so far) AF ratios, etc etc are all good.


The only reason I am looking at bigger exhaust is because its choking over 6000rpm
3000 spool, 4000 full boost and run out by 6000... so I have our Garrett distibutor building me a hybrid. GT2554R Turbo but with rear housing off the T2 or a T25 with AR of .48
Spool will be quicker than now, but will carry through to RPMs I will never ever reach... so its perfect.

In talking about the issue with them, they suggested (along with other Mini freaks) that the 2" exhaust is restrictive...

The exhaust manifold on it now flows fine and isnt restricting me...

Yes, I am running Megajolt and have an IC, I DONT have a temp sensor on the inlet side (after IC but really want to get one. Any recommendations, just any temp sensor will work? Just started researching this recently.

Why would I need to drop the compression - I DONT get knock (det, etc) at all, even on 16psi with my compression... I dont plan on running over 15-16psi anyway... and with a more efficient turbo and exhaust I think dropping the boost will still make the same power.

Hario - I agree getting a cooler charge is important and there are bends between my turbo and IC that are a little to sharp, so thats on the cards... moving intercooler over and checking the temps I get.

I come from a school of - if the intercooler is doing its job, dont change it, just a waste of money... so if the temps are close to ambient temps, thats as efficient as an intercooler can get... unless you add mist or meth sprays etc...

I told my turbo guy to feel free to build the hybrid with an external wastegate, I am happy to run one with external gate but is that going to really give me many improvements? I know you can control boost better... is it worth it running external gate if money is not a concern...

Thanks guys,
Pete

Edited by pristic on 18th Sep, 2008.

1132cc Turbo ~120 bananas ATW - Fun Fun Fun

Oh, and as for squeezing the dump pipe in, he said 2.5" pipe is still 2.5" squished... so ill get that stuck in.

Peter

1132cc Turbo ~120 bananas ATW - Fun Fun Fun

Actually Pete, it's not.

65mm ID tube has a cross sectional area of 3,318mm square.

Putting a 20mm flat on each side reduces the area to 3,191mm = 4% reduction (but still 63% more than your 50mm)

http://www.jbperf.com/

What I think he meant was heating it up and making it oval - ie/ Not just squishing it (technical term of course) lol

So you think 2.5" into slightly bigger pipe which is squished and then back to 2.5" is better? Im easy either way... he said the only prob is if the 2.5" pipe WONT fit through, he is saying that the join needs to be at the oval part, via a slip joint - which I dont want at all... I want a 2.5" with V-bands...

Dammit! It HAS to fit somehow...

Peter

1132cc Turbo ~120 bananas ATW - Fun Fun Fun

But what about the other things - ie/ External wastegate and which Temp sender/unit for the inlet temps? I really want to know what the temps are!

1132cc Turbo ~120 bananas ATW - Fun Fun Fun

well the main issue with the exhaust side of a turbo is when the housing cannot flow any more gas (when the power curve drops away like you describe) even when the wastegate is fully open, most turbos are still limited because the wastegate dumping right into the gas flow out of the turbo really Really reduces the flow potential of both parts. Using an external wastegate means the turbine has much less of a restriction to push the gas through, Honest, Forced Induction Performance Tuning told me so..
With regards to improved boost control, the answer is exactly the same, rather than the internal wastegate opening a little to modulate boost, it has to open significantly because there is high pressure exhaust directly at the watstegate exit. Does that make sence?! lol google it

Yep ok, spoke to the tubo guy and he's working on it. Looking for a rear housing to our 'specs'

If $$ allows, will go for a quaife diff too, 3.765 open diff at the moment and a little worried lol

Pete

1132cc Turbo ~120 bananas ATW - Fun Fun Fun