Martin’s PRV bone yard…

Martin,
You mentioned some time ago you had a bare set off 24vl. cyl. heads...can you do me a favour & measure the inlet port center lines.. eg. 108mm x 108mm & the port diam... the origonal runners are 108mm x 98mm...I am looking at making a set off inlets for my 24vl. similar to the P4 & don,t want to strip my inlet system to verify.
Cheers Eddie.

Hi Eddie,

Yes I'll measure this for you as soon as I get a chance, certainly this week if that's ok for you?

measure pleasure
Martin, can you measure me the distance between, the clutch spring and the inside surface of the bellhousing next time you are at the biturbo, cause of the central release bearing project
And a pic of the bellhousing inside???

Would be great!

You're not asking the right person
Main issue will be that the casting is shaped to give clearance for the crown wheel so to get the cylinder seated will mean raising it to clear .....

Did not expect anything from John, as we don't know each other. Martin is the right person, but too busy to be the fastest but he has already fitted the right clutch!

Why didn't you pop up earlier, having it in front of you ? ...joking...
Thank you very much for the pic and the explanation, i'll let it turn a bit in my head around!

Cheers

Martin,
You mentioned some time ago you had a bare set off 24vl. cyl. heads...can you do me a favour & measure the inlet port center lines.. eg. 108mm x 108mm & the port diam... the origonal runners are 108mm x 98mm...I am looking at making a set off inlets for my 24vl. similar to the P4 & don,t want to strip my inlet system to verify.
Cheers Eddie.

Hi Eddie,

107.5mm centre and equal spacing between them. Same goes for the exhaust. The port is flat oval as you know, and 43.2mm width x 43.6mm to the top of the injector cut in height, or 36mm ignoring it.

Hope that helps.

You're not asking the right person :wink

not wrong there lol

Why???

Why???

Thanks Martin...that,s exactly what I wanted.
CheersEddie.

Right I thought I would go back to some flow development and testing of the various PRV heads, and further previous results to compare the PRV in 12V form to other V6 engines and see how we stack up. Let’s face it this is what we are all looking to do, compare other marques and the technology of the day.

Well the airflow potential of a head will give the power potential of an engine, really the head if the build is such it can support the flow potential efficiently (remember the restrictions in the manifolds etc need to be accounted). If you want to read more then, you pick a good guide from the Superflow manual:

http://www.superflow.com/support/brochu ... ations.pdf

So I thought I would put some numbers around this by way of comparison out of interest. The Alfa 12V 2.5 and 3ltr engines make good comparison, 2V technology, but better chamber than the PRV from the point of even flow characteristic (pressure recovery) around the valve curtain area. The PRV is not so blessed in this regard, and this does affect our fuel distribution pattern, something I am currently trying to improve. Anyway, the Alfa 3ltr stage II engine here, with 11.5:1 CR and 292 deg cam gave 236hp at 6490 rpm, so good direct comparison. The standard 2.5 12V Alfa engines in 10:1 CR form were 200hp, >11:1 versions with hot cams and ported heads on 46mm inlets show 215+hp , and the Essex V6 head here went on to give 175hp at the wheels. So looking at the 3ltr Alfa and PRV 3ltr both in stage II trim on the same diameter valve give very similar performance, with the PRV beating it at the higher flow, big cams would pay dividends here. I will have to dig the data out for the OE 3ltr heads for both the Alfa and PRV, just to give some comparison, but not essential for this discussion. As you can see from the following, with careful flow bench development the PRV 3ltr head porting, seats and valve shape can be made to perform, and potentially more with larger still valves, but this would get into offsetting the shrouding and measures needed to achieve that.

So I think the P4 replica should be looking good for around 200hp given it’s a top end only rebuild, and the lower 9.5:1 CR. Andreas 12V n/a 3ltr with the high CR pistons, full build and fresh rings should see him to the 230hp hopefully, and that will be a lovely engine. So hopefully there should be some interesting articles on here this summer, John Law’s set included.



Column order (left to right):
PRV OE 2.5 44mm, PRV 2.5 stage II, Alfa V6 2.5 OE 44mm, PRV 3ltr 46mm stage II, Alfa 3ltr 46mm stage II, and finally Essex V6 3ltr 46mm stage II

Lift thou
50 17.1 18.5 13 17 18 15
100 38.9 37.4 25 35 36 29
150 58.2 55 42 53 57 44
200 73.7 72.2 55 71 74 57
250 85.6 89 68 87 92 69
300 91 104 77 102 104 78
350 93 114 83 114 110.4 86
370 xx xx 85 118 112 xx
400 96 119 86 122 114 91

I have it in Excel if you want it, bit difficult to drop it in here. Flow numbers in CFM, as mentioned above at 10" depression.

and to add some colour ... the 24V Venturi PRV engine on racecars at the moment, thing worth noting as I mentioned above on water pumps is the lower pulley, reduction in size to drop the pump speed...



You can see it's using the OE lower section of the 24V inlet manifold, so this is not their full blown unit, but would be nice to see what the other internal detail is.

Thanks for posting the flowbench results Martin, very interesting numbers, nice to see it listed that way to compare!
So i think it's not too bad to take the 2.5l heads as a base!

Yes, but not without a lot... and I do mean a lot of work. It was done as an investigation really, and the last test head I developed these numbers with has 3 different seat insert arrangements, numerous valve shapes and plasticine ports

The sensible thing to do would be to get it CMM mapped now, and then get repeat port copies through 5 axis CNC, but I don't think there would be any interested parties to put in any money quite frankly. There is more potential there, but it's a case of justifying the time...

Do you fancy copying some valves then? I mean reprofiling the replacement valves I've used according to my test valve shape...

Might be no interest now but ...take a decent casting for ref and we can always digitise it at a later date