Equal length manifolds
Turbo Mini Forums

Hi all,

I am a student currently studying motorsport engineering, i am throwing a turbo project around as a bit of a laugh for my mini. I am thinking of producing an equal length turbo manifold to mount a garrett T2 onto. I am stuck as to whether this will make a difference with a turbo? or whether i need to work out the pulse tuning?

Just toying at the mo, gonna be using an injection front subframe and some custom engine mounts to tilt the engine so space not a problem.

Any ideas?

Cheers Anthony

Correct me if im wrong but i dont think pulse tuning is really a concern on a turbo motor..
as far as im concerned you cant beat the mirage setup for the t2 ...

If you do use the mirage setup you dont need to move the engine mounts forward.. just use an adjustable engine steady..
Moving the mounts too far forward can cause problems with torque steer

There is no shockwave effect as the turbo doesn't have a pressure drop/surface to reflect from. But pipe sizing is important to maximise the pressure difference at the "pulse front" equal length and correctly sized tubes are the go here. A bit like an LCB. Problem with the mini is that you have to fit this lot in and a lot of surface area=lot of area for heat transfer. Underbonnet superheat anyone? You could lag it but I reckon the bends would possibly restrict the flow slightly and make the point self defeating. Janspeed did this (IIRC) and Jan was formerly a short stroke screamer man and knew all about his exhaust design, I expect. I reckon that the gains would be getting the turbo to spin up a tad better but the top end flow gain would not be realised unless you were expecting it to flow like a beast where you were using a massive boost, exhaust lift/duration, then the gain would only be small. Perhaps for class racing it might give you an edge, but since these guys can blow up virtually any engine with the welly of the standard set up, as they say "If it aint broke......."

Stu

Edit (I forgot Jan was exhaust design man anyway!!!!! what I meant to say was he had experience of using both turbos and engines where resonance effects were paramount, which there haven't been for years) The whole shockwave effect has been dumbed down by crappy fuel>less CR>need high CR to run long duration cam>short strokes like long cams>hence the use of longer strokes to achieve a capacity and more low down grunt. I love my short stroke screamers. Yeeeehaaaaa!!

Edited by Hedgemonkey on 13th Mar, 2005.

Bugger off, I'm getting there.

Its funny u should mention the mirage kit, cos i worked for mirage last year. I am just aiming to get the best flow i possibly can from the manifold. I have access to a flow bench and everything else i need at college, as well as a knowledgeable group of lecturers. However, you guys, like me love your minis and my lecturers are stumped!!!!

Cheers Anthony

do some work slacker

wouold equal length manifolds work becuase of the siamese port between 2+3?

ps i know f-all about this

Pulse tuning: Well crack on and let's get some REAL info on this.
Thinking about it, the 'A' does have good separated pulses.

Consider: Firing order 1342
Now picture the following:

Cylinder numbers: 1 2 3 4
Exhaust runners: A/ B/ C

Hence when applying the firing order to the above, we get the exhaust pulses:
ABCBABCBABCBABC.....

But that's where my knowledge ends!!!!
What you should be looking at (maybe) is seeing if there is a measurable difference in power between a '3 into 1' at the turbo (stock manifold), an LCB style affair with the turboi after the last collector, and then playing with pipe lengths and bore diameters on the two options aswell.

That's the answer we all want to see!

Edited by turbodave16v on 14th Mar, 2005.

Yeah i would like to know that aswell

Shockwave tuning is really only any good on a car with an internal reflector (megaphone/reverse cone) or an open exhaust and a really long cam, hence why they have fallen out of favour in recent times due to fuel limitations/noise regulations.

I reckon that at the top of the tree, you're looking at the inertial extraction effect, where it is important to keep the individual exhaust pulses apart (leaving a good pressure drop for the next pulse) without excessive restriction (pressure diff not high enough, hence next pulse doesn't fly out so well) or too big a pipe (insufficient velocity to get everything out the way). There is a maths way of finding out the ideal pipe size but a good old trial fit usually gets the job done.

So, what you find in practice is that the inner branch of the LCB has got to have the same volume as the outer two put together, this coupled with sizing the outer pipes correctly by long testing, gives the ideal size. This gives the best flow extraction for the setup. Problem is, the different pipe volumes give a different shockwave effect and this is minimised by having the outer 2 branches the same length as the middle one, the bit where the outer 2 join isn't the best thing for shockwave (if you're trying to use that) so that's why 3>1's work better for long cams. Again, this is an oversimplification, compression ratio, exhaust valve timing/lift/duration all influence the property of "the slug" and how it behaves as a shockwave or its inertial properties.

For a turbo system, an LCB system would give the best pulse properties, although the effect of them would be reduced as there is a sodding great restriction there! The thing would flow a tad better (weeny bit) but the whole pulse thing would be the crux of the matter.

Anyway, that's off the top of my head, I'll go and have a think about it some more........instead of doing something more constructive

Bugger off, I'm getting there.

Well so far have just been playing about on CAD at the moment to try and get some ideas of the feasiblilty. Have been discussing it with my boss and the best idea he could come up with was turning the boost up to overcome the flow problem, but surely using the pulse tuning would make it all more efficient.

Will post my pics i have done soon but not finished the plans for it depending on the effects the pulse tuning may have. Need to get a book from the college library on exhaust tuning for some direction!!!

All these ideas, just gotta find all the bits for it. Got the car though so at least thats a start!!!!

Anthony