I did indeed Chris, I'm doing some flow testing soon (maybe this week) with some direct to head bodies and a standard inlet manifold (in the middle of converting a customers car) so will search out the exhaust test and post it up at the same time... any good ? Those figures look very low though, but the percentage changes could be close.
At last Chris, as requested! This is the exhaust flow data from my ported ABF head. I also did some testing with a Supersprint manifold, so as soon as Mike H see's this and rustle's up another of his charts I post up the data... but for now here is the standard flow and the final modded port. Standard ABF exhaust port flow .050 14.7 .100 33.5 .150 51.1 .200 63.5 .250 70.0 .300 74.2 .350 76.3 .400 78.3 .450 78.2 .500 78.3 JMR / Mr hillclimber modded ABF exhaust port .050 16.5 .100 35.5 .150 53.4 .200 68.0 .250 77.7 .300 83.6 .350 87.4 .400 88.8 .450 91.0 .500 92.5 There's some text to come with this but the day job bekons, so I'll add that later. On another interesting note, I did a quick flow test of a standard k-jet inlet plenum on a ported head (this one actually!) and a full flow test of a direct to head throttle body off a car I'm converting. I'll get the full flow test up later (that time thing again), but on the ported head the flow at .430 thou lift dropped from 130.8 to 120.6 when the k-jet plenum was added. I removed the throttle body and flow went up to 122.0. So when you next think of porting a standard t/b I would'nt waste your time, if removing it totally only gains 2cfm, porting it wont gain much if any at all. I could'nt run a full lift curve test because as you know the plenum sweeps back over the top of the head, so I cant set up my valve opening tool or mount a dial gauge to read off a full curve... for the test I cut down some bolts short enough to clear the manifold to hold open the valves at the pre-set point and just ran the one check. I also did'nt test with the metering head as it will be a bit of a mission to support it, but at some point I may make an adaptor to mount it straight to the flow bench and test it that way. I'd imagine around a further 5cfm or so can be knocked off the above inlet flow figures, so there is more than enough flow with a ported head and a standard plenum to support around 190-195hp for road use, a bit more for competition with some more tweeking. I'll get the bare head v's the direct to head t/b test up later... bet you cant wait for that one...
No i cannot wait, and am quite supprised at the flow of a standard inlet manifold. Well done for all this info it makes very interesting reading.
Yep, good info Jason. Supports what has been proven out in the past with numbers around 190bhp on plenum. I suspect those were not quite perfect set-ups. From what I have seen in the past (not VW), 115 cfm with a fully dressed inlet, with the right exhaust / cams / bottom end and mapping should be good for up to about 210 bhp. I suspect the ducting / metering head / airbox / filter may shave off a little more than 5cfm, no evidence to support this, just a gut feel and the length of the tract will almost certainly have some viscous loss. Keep up the good work
Whos going to be the first man to make port cc/cross-section smaller and check the results on a flowbench
Thanks chaps. Neal, I would'nt be surprised to see over 5cfm, best pull me finger out and test it I spose! Anyway, for those that had a sleepless night waiting for the DTH results () here they are... JMR ABF ported inlet .050 29.6 .100 51.3 .150 72.0 .200 87.6 .250 103.0 .300 116.4 .350 124.2 .400 128.8 .450 134.0 As above plus Jenvey DTH throttle body .050 29.0 .100 51.5 .150 70.9 .200 86.6 .250 102.6 .300 111.6 .350 118.7 .400 125.2 .450 128.4 So, there are indeed still losses even with a direct shot down the port. Some of it will no doubt be due to wall friction from the total length of the trumpet & body, but I'd say the biggest loss is due to the butterfly & shaft. Previous flow testing has shown the on the same head with a hi-flow DCOE carb manifold that a figure of 132.8 @ .450 is achievable through just the manifold and head but with no carb. When testing an 8v set up I found a 4.5 cfm loss through a 45 DCOE fitted with a 38mm choke. To save you reaching for the Casio that would bring the hi-flow 16v carb manifold set-up back to around 128.3 cfm @ .450 when fitted with a 45 DCOE. Now take a look at the DTH figures @ .450 above...
45mm versions tested yea? 48mm available also (originally designed as 48mm) what estimated difference would you anticipate? airflows not directly equating to power/torque as we know
A bit, though not too far off what I was expecting. There's bound to be some loss with a butterfly, we cant have it all.
Nope, I did'nt find any difference with it on my manifold tests. There's also a small step at the bottom, the body being slightly bigger than the head. I did make a small ramp there and found no change at all in flow.
Yes indeed, 45mm versions. I'd have thought the difference was small between a 45 & 48, couple of cfm maybe. I expected some sort of loss from the butterfly/shaft, and going from the carb test it's about right, so it's not really a bad thing... though the carb does have a choke and an aux venturi in the way too! No thats true to a point, but no airflow means no power. I have some DCOE bodies coming soon for an 8v project, so I'll fit one up to my 16v manifold and see what we have. I'll also do a full flow curve with a 45 DCOE at the same time, maybe try with and without the choke and vent and see whats what. I dont think the choke effects the flow by much at all, as long as it's not really small. But having said that, I know an engine builder very well who uses chokes in t/b's on some engines. The top end power is all but the same but the mid range comes up... and thats on a small engine with small chokes used. So maybe the aux vent has litttle effect too... we'll soon find out.
