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Richard.D
27th July 2001, 06:14
Did anyone recently fitting front-mounts consider (or actually do) swapping the inlet manifold around to shorten the path?

I recall both Firefox and Pat mentioning this as a good solution (and I guess Firefox has done it....twice http://bbs.22b.com/ubb/smile.gif) - but has anyone mortal tried it? What's involved?

Thanks
Richard

bdearnley
27th July 2001, 09:15
The Rigoli's here in Australia who have the world record drag racing wrx with a 0-400m time of 10.01 had an article done on them in a local car rag recently, and stated that reversing the inlet manifold made no noticeable difference to power or response (lag). Bear in mind that their car is used only at full throttle, so I don't know if they're in the best position to comment on transient changes in response when on and off the throttle. But you only save about 2 feet in intercooler piping length, and is it really worth all the hassle for maybe 50 rpm less lag?

The WRC cars that used to do it had the intercooler pipe coming out of the intercooler and straight over the top on the radiator into the reversed manifold. This would save lots of piping length and explains why their intercoolers were offset to the drivers side (turbo side) of the car if you see a front-on shot. Our cars still have to have the pipe coming from the other end of the bumper bar and then up and back towards the middle of the engine bay, front or back, depending on which way the manifold is oriented.

pat
27th July 2001, 23:07
Richard,

It would be nice to believe that my life expectancy was boundless but with my driving.... ahem http://bbs.22b.com/ubb/wink.gif

To the best of my knowledge, J has not reversed the intake manifold on a Subaru engine (yet)... I haven't done it on an engine that's in a car (yet) but anyone visiting Scoobysport will be able to see an engine on a stand with the intake manifold the wrong way round... I was messing around with positioning, and discovered that it's possible to drop the alternator low enough to clear the throttle body, so no repositioning of that http://bbs.22b.com/ubb/smile.gif Too late for me as my alternator is on right of the engine, but hey....

I have a large front mount on order, completely custom design with a good balance (hopefully) of efficiency and forward pressure loss... people often forget that the turbo has to make more pressure if the intercooler pressure loss is high, in order to get the same manifold pressure, and this results in higher temps out of the turbo, which IMVHO is counter-productive.... just wasted energy!

Anyway, when that arrives I will swap the manifold round, possibly going to an earlier manifold (shorter intake runners, better for top end power). But this will not be a simple job, as things which normally are attached to the manifold (such as water header tank) need to be moved somewhere else. If prepared properly, I think I'll get it cracked in a day (including the fabrication of custom pipework to connect it up). I am really looking forward to it, charge temps are horrendous at the mo!

With respect to the Prodrive core mentioned, I do not like it. It has entry and exit at the same end of the core, which will result in more charge air flowing through it at the pipework end and less at the other. My design is "diagonal flow", this ensures each part of the core is used equally. Sadly it doesn't allow short pipework but since gas velocity is quite high on the pipework feeding hot air to the core from the turbo, this should be bearable. The nice thing is the length of pipework from the core to the throttle body is very short (just over a foot) and therefore the (just cooled) air doesn't get chance to heat up again before being consumed. Or so the theory goes.

Ah well, time (and the datalogger) will tell.....

Cheers,

Pat.

Adam M
30th July 2001, 00:16
Your design is diagonal flow? http://bbs.22b.com/ubb/eek.gif

I dont think so http://bbs.22b.com/ubb/smile.gif

pat
30th July 2001, 14:59
Adam,

it is diagonal in the sense that air enters the bottom left and leaves at the top right. The tubes are actually vertical, with horizontal end cans. So the tubes aren't diagonal, but the airflow is, IYSWIM....

Cheers,

Pat.

Richard.D
31st July 2001, 04:56
Cheers Pat

Don't s'pose there's a photo of your engine bay anywhere? In 'one' of it's states of flux at least http://bbs.22b.com/ubb/smile.gif

Thanks
Richard

Adam M
31st July 2001, 09:53
Pat, I understand teh tubes are vertical, but I think you will find it was I who convinced YOU to have diagonally opposed entrance and exit to make use of the full core!!!!

Remember my convincing you of the average travel of air from the exit pipe back towards the middle where the throttle body is would be effectively no different from the air being forced to do the same inside the core???????

pat
4th August 2001, 00:29
Rich,

I believe Michelle took some piccies of the engine bay up at Castle Coombe, I suspect it has changed since then though http://bbs.22b.com/ubb/smile.gif It's a bit of a mess at the mo, all waiting to get relocated, but the alternator is already where the aircon should be! The air intake is horrendous, waiting for TMIC to disappear so I can put the airbox under the scoop...


Adam,

'tis possible http://bbs.22b.com/ubb/wink.gif

My original vertical flow design is still my favourite, with a central exit from the top end can, and a central entry to the bottom. But I think that diagonal flow will make better use of the core, hence the reluctant switch.

Now whose idea was it to go with vertical flow? http://bbs.22b.com/ubb/wink.gif

Cheers,

Pat.