Race Engine Forum UK

I need the forum's opinion with some exhaust flow figures, from a Peugeot 1.9L Mi16 head. The head is almost identical to the S16 head Guy talked about in the locked Cylinder head section.

This head normally has a 4-2-1 eight branch manifold. However, I was lucky to come accross a Peugeot GTi6 4-1 tubular manifold that has been ceramic coated. The problem however, is that the port spacing/layout differs between Mi16 and GTi6 heads. So I made a 25mm thick adaptor plate, hoping to achieve a smoother transistion between the two exhaust port shapes.

The graph below shows the results @ 28in., together with the inlet flow. As you can see, the adaptor plate severly hurts the flow after 0.300". However, maximum exhaust lift is 0.362" and the ports still flow expectionally well at low lifts. The I/E flow average percentage up to 0.300" is 79%, then 77% at 0.350".

So my delema is whether to use the ceramic coated 4-1 design, stay with std. manifold or construct some new 4-1 pipes that have a more gentle transition. The first two are easy options but naturally new pipes will take some time.

Very interesting question Peter,

as we both know contemporary thinking is that with E/I ratio over 70%, (maybe less), there is no exhaust pumping loss problem, that said provided the exhaust cam is giving the right kind of valve event.

However I would not like to bet on whether the high flow one is better is better on test! If anyone has direct experience I'd be pleased to hear it.

[For those who don't understand E/I we're talking about the ratio on flowbench test of airflow exhaust port to inlet port. The least you can really get away with is 65% and more is better].

GC

Guy.
I would like to see some examples of standard head E/I flow and what different stages of tuning provide. Have you any data to hand? Which heads flow well from standard, and which are really poor?

Andy.

Andy you can see some of this data in the VWshop section, where you can see cosworth YB vauxhall XE FL 16v E/I, or be able to work them out.

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Rich

i'm a little curious om how big the mismatch is and how the adaptor plate looks. the flow difference is (and the way it levels off) is quite marked.

I've managed to improve things a bit. Attached is a very rough sectional drawing through the ports/adaptor/manifold flange. I have decreased the angle down to 9 degrees by taking some metal out of the manifold flange. You might be able to get a better idea from the pictures. I'm fairly confident the assembly will work now but haven't had it flowed as yet.

The way you have executed this Peter, very nicely, as I'd expect from you, it will have no adverse impact on power at all, in fact the divergence may even yield a benefit over a parallel section.

GC

Have you come that far as this engine have been tuned yet?

A danish guy is having problems with his 2.3 litre XU engine.
It's got a 2.0 16v XSi (XU10J4R) head with 50mm throttlebodies, some 290deg catcams and gti6 exhaustmanifold.

He doesn't seem to be able to make good power, and a well respected danish peugeot tuner have said it's probably due to the exhaust manifold.

I would hva thought this manifold sohuls be able to make like around 250bhp mark, but that's maybe optimistic?

I've been too busy doing jobs for others but I hope to finish it by the end of January. The pipe dimensions seem fine for a 2L engine making max. power at 7500. Mine is a 2L with 11.8:1, 48mm TB's and big cams. I'll let you know.

I finally have this engine finished and dynoed. I still need to run to bed the rings in properly and map the ignition - it's running a flat 25 degs. of advance. Very happy with the result so far however. Rev. limit was set to 7400. I don't know why the printer clipped the last 500 rpm of the power curve.

It's just occurred to me that I need to quantify the results above with some type of reference. Figures from roller dynos are variable at the best of times. So here's a 1905cc version of the same engine, 10.8:1 with one of my mild inlet cams, otherwise standard. Power at the wheels, same gear in both cases. There were four runs on this run, testing two different ECU's. The rev limit was 7100.