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Wed Nov 19, 2014 3:50 am
Tauranga New Zealand
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Wed Nov 19, 2014 3:50 am
Tauranga New Zealand
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Sun Sep 28, 2008 4:25 pm
MFaulks wrote:Hi Chris
Hope you are out there enjoying your holidays! Well, when you catch up I have developed the port and happy with the overall result - bulk flow, flow down force (cylinder filling), and mixture motion (wet flow)... results look like this (.. and that's my best reworked 46mm inlet valve 3ltr head by comparison, not the OE 3ltr head performance):
I'm quite pleased with the that given the complexity and extreme care needed with the 2.5ltr port SSR compared the 3ltr.
Martin
MFaulks wrote: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.
Non Member
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Wed Nov 19, 2014 3:50 am
Tauranga New Zealand
Non Member
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Wed Nov 19, 2014 3:50 am
Tauranga New Zealand
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Sun Sep 28, 2008 4:25 pm
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