trying to source but its a minefield of contrary information..all we can say for certain is that john s worked so i will try one ..though funny thing is the primaries on his were smaller than mine..go figure because i can't!

Have you managed to get yours flow tested yet?

Ross

rule of thumb from what ive been told is 1 and a 1/2 times the size of the turbo hotside is the best for a down pipe and the closer you can make it near the turbo outlet the better.

is that 1.5 times size of turbo outlet? and do you mean it needs to reach that size as near outlet as possible?

ross flow testing i am not sure what that can tell us about the differences in flow capability between the cars but i would get it checked if there was someone near i knew could do it

i am not sure if a 3.5" downpipe would make a diference..the biggest pproblem is room and having to use such tight bends straight out of the turbo i am wondering if there is anything else i can do about making space for the downpipe to be able to run straight outwards a little further

Isn't there an alternative route you can takE?

Ross

carry on!

1.5 x the size of the turbo hot side ie the outlet and the faster you can get to that diameter the better so either straight away if room or when ever your able to

ok we were straight to 3" but i will go for a 3.5 and see what that can do as after gaining over 100bhp removing bits of exhaust i want it as free flowing as possible

Italy for a manifold? would you not consider booking it in to OJZ or Simpson racing exhausts with the planned sizes you want and leave the rest up to them?

ojz has a 2 month + lead time i have not tried simson but will look into it tomorrow..thanks

Have you called OJZ though? He might have a shorter lead time now that the racing season is underway

have spoken to him today to be frank he was suprised the 36ml primaries were an issue

Three things:

1) 600 BHP will produce the same amount of exhaust gasses, whether produced by a 2 litre, 2.5 litre or 5 litre engine. That is because you will be burning the same amount of fuel in the same amount of air in the same amount of time in order to do so.

2) a five cylinder engine will not be choked by 36mm ID primaries at 600 BHP.

3) increasing the diameter of the pipe to a diameter much larger than the oulet from the turbo (in your case 2.5") will not yield much benefit.

In an earlier post you did alude to the fact that there are 500-600bhp engines producing big power without massive pipes after the turbo. Another clue is to look at turbo race/rally engines. Lancia, Porsche, Ford, Audi - never mind the F1 teams in the turbo era - ran with pipes no larger than the turbo exit diameter. Think about it: the biggest restriction in the exhaust system is is the smaller diameter (exducer diameter) of the turbine wheel itself.

Of course the frame size of the turbine housings are limiting - a GT28 will not flow as much exhaust gas as a as a GT30

ok i had thought that myself (no point bigger than 2.5)but having gained 50bhp by removing the centre exhaust section ,then another 50 nearly venting wastegate to atmos rather than down pipe i am leaning toward giving it as much space as possible..it would run best just turbo with no exhaust so to my thinking ;the least restriction and the more ability to flow the better? yes no? this is bloody hard work for the layman..
i spoke to the american turbo supplier and they said give it as much room as possible as it will give its best with no exhaust!

what were the lancia,f1 etc doing with thiers? using outlet size for downpipe?

The facts are 2 identical cars to yours are running well,Barbz,ROb40.The only thing you have different is the manifold and blower,.
The only concern is that Johns ran smaller primaries than you currently have.
That said,Johns build does differ from yours quite a bit.

The complications involved in calculating the flow and pulse rates of this is based on theory mainly over forums.
But i know full well that a manifold can cause more issues than the stock one.

Stick with it mate and dont spend all night worrying.
The best man is on the case and im confident he will sort it.

Ditto!!!
I cannot believe that your 36ID manifold is the cause for this issue…
Johns had 34mm ID – this will result in a better response in lower revs, but your manifold definitely should be better in top end performance.
As I stated to you – I have 34ID as well (I bought mine from Cufaro Racing some years ago, it was selfmade from Cufaro – no Italian like Scara) – after about 560HP there was no chance to get more HP out of my GT3082R – either it was my manifold or it was my small 0,64AR.
We will see after installation of my new GTX3582R – this unit is capable to do 760HP. Thus this new charger definitely won’t be a limiting factor. Then I can tell you how far 34ID will reach…
Other suggestions:
- Check your catalyst (do you have one?)
- maybe your coating reduced the inner diameter of your manifold in some area significantly – check with an endoscope?!
- Check of the charger – is it ok? Maybe that a small 0,63AR had been installed instead of your wanted 0,82?
In my opinion you bought the best available manifold on market for this car. Moreover the 3” downpipe is more than sufficient.
There must be another reason for this issue…
Juergen

Are you using one of Leighton's big MAFs?

no maf i am on a dta standalone nigel

i also think its got to be something else as the more i look into a solution and the more manifold specialists i speak to i find 36 should do it easily..
however i also find that primary length has a big effect as does collector as does angle of wastegate pipe exit and cubic capacity should have a direct relationship on the length of the primaries
so i also know you cant just knock one up and expect it to work well
the feeling at the dyno was it was a restriction and the more we removed from the hot side the greater the bhp which i know was inevitable but not to the degree we experienced..there is still no easy explanation for why however much boost we gave it it couldn't get much further than 400bhp and all we got was quicker glowing of the manifold which again is indicative of restriction..we were holding steady boost also
we are going over every valve,the whole boost set up and testing wastegate etc also so maybe we will find something..i hope so as it will be an expensive fix otherwise!

Obviously restrictions futher down the length of the exhaust will cause flow problems, so removing one of them (as you have ) will bring improvements.

Venting the wastegate to atmosphere is a very good thing to do, because dumping a big volume of high temperature gas into the flow directly after the turbine exit will reduce the pressure difference across the turbine and increase the volume of exhaust gas that the pipe has to flow (hotter exhaust gasses=greater volume).

If you can remove further restrictions in the exhaust after you 3" pipe you should see a benefit, but if you go up in size from 3" to 3.5" any benefits will be negligable.

Yes, in all the pictures I have taken they use the same size pipe as the turbo exit/outlet. Pictures I took at Goodwood Festival of Speed 2009 included Lancia LC2, Ford RS200, Audi Quattro S2, Porsche 956, Bentley Speed 8, Audi Le Mans petrol engined winner - same engine as the Bentley of course. F1 pictures are not mine but from the book 'Formula 1 - the Turbo Era'

You should expect the manifold to glow red/orange - EGTs will be 800-900 degrees C at load on boost. Seeing the manifold glow is not a sign of a restriction. Whatever the setup, at high boost pressures the pressure in the manifold is going to be equal or greater than boost pressure even on a perfectly designed system.

What turbo is it you are running (I've read the thread through and couldn't find this information)? I am particularly interested in the turbine spec and housing A/R so I can do some rough calculations.

i will send spec via pm but what i meant by the glowing was that it happened much quicker with more boost even though we made no power

whats Barbz's theroy on this?

It looks like your 'hot side' is what was run in the racing version of the Ford RS500 (rather than the road car which was a bit smaller) - a T31 housing with a stage 3 turbine.

If so, the turbo should not be causing a restriction up to similar power figures - though who knows beyond that?

what do you think of it? it is pulling hard by 3200 and ive seen positive boost at 2500 when booting it and thats with the .82..
marco..the mapper said he has seen similar a number of times and he was sure it was restriction on the hot side which seemed to be right as we were removing bits it was bearing out what he thought
however barbz thinks that before we bin the manifold we go over everything for boost leaks or duff valves then if no better we try another manifold and turbo to see if the set up gives what it should with that..
if not its not manifold/turbo..
if it gives what it should then it is ...simpless!
so those are our next steps...ill post the results

any more news on the restriction KTM?

yes ..after testing it turns out as we suspected to be the manifold
..although it flows very well with a 2.ol it does not for the 2.5..with the size of my comp wheel and valves this manifold just does not deal with it efficiently..we have longer pulses with greater volume of gas than the 2l with its shorter stroke and less cubic capacity...
just goes to show what works well on one set up does not on another
we have gone with a bit of a radical idea for a solution...something definately as yet untried on any coop anywhere..i can't actually find information on any car (as yet) thats tried it as a tuning solution though there are one or two older turbo cars that used it though not at our power level
the sad thing about it is it was so well made..a real nice piece of kit...someone with a 2l will make over 500 with it though i hope..the other loss is that we had full boost by 3200 revs on a 600+ capable turbo...the company themselves have been very good and offered to build one to any spec from a full race manifold with turbo position moved to similar with bigger id, free of charge.. but we are going as i mentioned earlier for the more rad aproach..i will elaborate if it works!

How do you mean, longer pulses?

And how have you measured (compared with a 2.0L) that you have longer pulses?

is this information you're keeping secret (no issue with that!) or willing to share?

My 2.0 clocked 587bhp, but if we ever get the 2.4 in the car (long and painful story of being let down), should I be looking at having a new manifold made before I bother getting the engine back in?

I've not read this thread word for word but am I right in think your running a 2.5" exhaust? Have you a picture of the manifold?