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Technical Inlet manifold for a revvy P75 motor

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Technical Inlet manifold for a revvy P75 motor

Brooky

Brooky

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Right, im building a 1242 8v engine up for my rally cinq and im wanting to have a play with the inlet manifold.

Now i remember arc saying that the stock P75 mani was prity crap...

So, would something like Fingers plenum chamber work well on a N/A setup?
See this thread https://www.fiatforum.com/cinquecen...chamber-so-far-pictures.html?highlight=plenum

Plans are so far are for a very similar disign to his but with a 40mm TB off a 1242 16v engine.

So what are peoples thoughts on this???

I suppose i could make some ITB's up with a rake of 30mm butterflys from the standard cinq TB's....but then it would still require some kind of plenum chamber on top of them. And id rather not make a set of ITB's to be honest, save them for me other cinq
 
Yeah a plenum chamber with shortish runners can be made to work very well N/A and forced induction. I've not looked into N/A application so can't give any hits of volumes, diameters, lengths etc.
 
Found a nice website: http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=466
Maybe of some use to John, if you havent already finished it:p

Some experts suggest that the plenum volume for a peak torque somewhere from 5000-6000 rpm should be equal to 50-60% of the "equivalent" displacement in a 4 banger. On an N/A setup the equivalent displacement = actual displacement. On FI setups, the equivalent displacement = how much volume of air is blown into the motor.
Click to expand...
 
I've not read that article so this may be covered however remember that runner length and diameter will have large implications on when torque is produced and also the way the torque curve leads up to and moves beyond peek torque. Get the synergy wrong and you'll be down on torque, power & drivability.
 
What do you sugest then....like i said i could make some 30 or 32mm throttle bodies up,but surely they would have some kind of plenum on top. Suppose they could have a filter on top, but i want to get a decent cold air feed to them(without sticking a big vent or scoop on the bonnet)

John....have a drool over this http://www.skylinesaustralia.com/forums/Complete-Inlet-Manifo-t210411.html
 
fingers99 said:
I only mentioned it cos you like wild cams! ;)
Click to expand...

its getting a wild cam for sure:devil::devil:

I just carnt be arsed faffing about with machining the splindle for all the butterflys, seals, linkages ect ....but on the other hand, it'll keep me very busy and be my first major machining project. Still rather make a plenum tho
 
hey the 4 30mm tbs sounds a good idea. personly i would machine a single spindle that all the butterfly's are on. it wont be hard as the spindle goes straight thru. it also mean you can use the standard TPS on one side and the original throttle cable/cam on the other.
Also saves farting about with linkages and seals as you said.(y)
 
yeah thats what i was thinking, but you'll still need the seals, to stop air leaking in where the shaft goes through the walls of the mani.
Will all become apparent when you strip a TB down

Doing the shafts induvidually would be eaiser in a way as theres less of a chance cocking up a measurement
 
fingers99 said:
Only issue might be that bumpy cams don't like plenums.
Click to expand...
Wild cams really don't get along with any single throttle body arrangement.

Brooky, you may do well to have in-runner TBs and a common induction/settling plenum, in terms of power and torque this setup can work very well. It's a lot of work though & may well need the remaking of the manifold.
 
looks like another ITB'd cinq in the making then....what a shame.

Cheers for the help guys:worship::worship:, will make a start when i get back to work(in two weeks time:D) and get some ally bar to machine.

In the mean time,anybody got any 30mm TB's;)

Ive already chopped the stock P75 manifold down a few weeks ago:p
 
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