vx inlet manifold equalisation

[Vx124]

I saw on Guy Croft's website a while back that he was working on equalizing the standard volumex blower-to-head manifold. Does anyone know if he was successful or how he went about it? Would be an interesting modification.

[Wallace]

E-mail him and find out !

I did suggest once that you could run with different size pistons to equilize flow - - but no-one thought that was a good idea .. . .

[Vx124]

apparently its still in progress. He mentioned "Unfortunately one cannot assume per-se that air flows are the same as fuel flows, gasoline laden air may well behave differently, and assuming they are same could lead to serious disparities on distribution".

Would fuel injection be the solution to this? Equalise the airflows, then tap an injector in front of each port.

[VX131R]

hey Mark, Welcome to Lancisti :D

There is some bloddy smart people on here, I saw that on G.C's site too, don't know how he did it though. Possibly ported the internals of the manifold???

[cthargiss]

Unfortunatly this is a problem common to all engines that use a fuel distributor upstream of a branched manifold whether forced or natural. Tuning must be compromised in favor of the weakest cylinder. The ideal is individual distribution for each cylinder, down stream of any boost system, whether injection or carburation. Perfect tuning can only be obtained with individual exhaust sensors for each cylinder.
Craig

[chrisc]

If i was going to be doing that task id be moving the supercharger further out (not that theres any room to do so!) or maybe fabricating a crazily long pulley :D - Either way would obviously involve basically a brand new manifold. Imho the stock inlet manifold is dismal for anything other than stock power.

A guy I met who had put a mercedes blower on a vx engine found that he had huge detonation / uneven mixture problems because basically all the air went to the first 2 cylinders (from the cambelt end obviously).

[VX131R]

I think with proper port matching between manifolds and head, and manifold to blower etc you can improve on the standard unit, but I agree the only way to get it right is to fabricate a new manifold.
cthargiss: If you get everything right from air box to exhaust extractors,( correct lengths/ diameters etc) I doubt you will need 4 O2 sensors, we are not talking F1??

[Vx124]

sounds like an uphill battle

[cthargiss]

VX131- As long as you have uneven air flow, you will have one or two very rich cylinders and one or two very lean cylinders. Hence the need for multiple sensors. Witness the problem chrisc described. Judson used internal baffles in their manifolds to equalise air flow and pressure. IF you can get equal flow and pressure to all cylinders, then a single sensor will do. As the vx manifold stands, the flow and pressure are far from equal.
Craig

[VX131R]

cthargiss: I agree entirely, just meant you can improve on it.
Am in the middle of fabricating something similar to the 037 for mine. The 131 is blessed with plenty of room in the engine bay. Bonnett clearance might be my only issue.

[Will]

you could equalize the flow with something as simple as cutting a gasket undersize in #1 and #2 ports, but first you need to run the motor and figure out HOW MUCH. It's probably a lot less than we think, remember how the valves actually open, this is a lot different from the flow-bench result where all the pressure escapes down #1 and #2.
-Will

[VX131R]

Hi Will, what did you do on your 190bhp little gem?

[Wallace]

Problem with a simple restriction is that it won't be proportional to the intake air velocity - . . so it will only "work" at a given load/rpm.

Different manifold with equal length runners is a better option - and then you can use a better blower like the sprintex - or a more readily available (cheeper ??) one !

[chrisc]

Yeah, undersize gaskets and suchlike sound like a right bodge. Do it once, do it right, sell it for fun and profit :) make up a few adaptor plates for the end of it to commonly available blowers too just in case.

[Maigret]

Undersize gaskets may not be such a bodge as first appears. While not the ultimate solution it is following the same principle of balancing multiple carburettors.

[FORZALANCIA]

You will need a good plenum chamber i made one its on my setup which i will post up soon, it uses part of a fiat 124 twin carby manifold. How do you post pics on this site anywayz?

[Hamish]

You will need a good plenum chamber i made one its on my setup which i will post up soon, it uses part of a fiat 124 twin carby manifold. How do you post pics on this site anywayz?

Easist way to set piccies up:
You'll need to set up a gallery and post a link :wink: I can never seem to be able to get photos to 'load' so I gave up trying :oops:

I'd have thought the ideal solution to the fuel issue would be FI - and it might be possible to drill the standard manifold to take injectors, but then you get into having to run mapped ignition (don't you :?: ) of some kind and serious modifcation of what's under the bonnet as is.

It would be interesting to see how GC has got on with his prototype manifold, but as a short term cure, Wills gasket 'fix' would do the job or perhaps phased sleeving on the inlet tracts from the manifold to the head... working out the 'math' would be interesting :!: and possible expensive on an engine 8O