Turbo Heads

is pressure directly proportionate to flowed volume?
so if you add 50% for pressure, do you get 50% more volume of air in/out?

i think i need to read wikipedia a bit more

Depends on the scenario, simply increasing the pressure will not double the flow (unless you remove all restrictions) By its very defintion, pressure is 'resistance' to flow.

Basically, you want to think in CFM, not pressure, as pressure is a meaningless figure for power gain. You can increase inlet pressure by restricting the exhaust side, and you will infact decrease flow through the engine, even though inlet pressure has gone up.

I think it will help a bit,a restiction's a restriction .If you're constipated pushing harder wont help ,but if your a###hole was bigger

I will say though Lee, that yes, it may be smaller than the 3 runners going to each port, but that is all academic considering those 3 runners lead into one main pipe which is the same diameter as only one.

Hence, if its not the biggest restriction in the 'chain' then enlarging it will probably make diddly difference.

But if it's balanced to the inlet and doesn't then go to a std manifold it will be better innit ?

Upon further inspection and even further reading I'm not going to enlarge the exhaust ports .They could do with a smoothing but not as much as the inlets need .
There are two nasty lips/steps ,one at the inlet and perhaps the worst under the valve seat where the machining has carried on to form a 1/2 mil step in some cases.
I have made a start on one ,not going for a mirror finish but getting rid of all the lumps and bumps .................

Thanks Martin not in any rush .I've got a spare lump that I'm practising on I'm only looking to clean and smooth the ports up and get rid of a few nasty lumps .

... bum trying to search for my old airflow figures, yes you guessed it I can't find that note book been searching all morning... I never liked electronic files, like to scribble too much

they were also posted up here... note the missing post between yours above...

... well the answer is - it is possible to achieve NO loss in flow with the std header fitted, tested on a calibrated Superflow airflow rig at my good friend Guy Croft Tuning yesterday. Not tested with the final 2 into 1 collector fitted but that can be reworked as well. But the rest I ain't tellin... ha-ha+

Well after searching for ages and great annoyance at losing my test data I have found the first sheet of my notes (some thing at least ) when I was taking flow numbers on some of my original mildly ported 3ltr n/a heads (seat angle work, 46mm inlet valve on 45 deg seat, throat pocket work), later these were further developed.

Anyway to the numbers tested at 10" depression for comparison:

Inlet bare port flow (corrected for temp, pressure and humidity) 123 cfm - seat dimensioned for 46mm valve.
Exhaust bare port flow, corrected as above 87 cfm

E/I ratio no header 71% good result.
with the std header this dropped to a poor 61% and disturbed flow and turbulence, clearly some losses to over come.

Subsequent work addressed these issues. However, of more interest, the 2.5ltr turbo heads I've recently completed as part of an experimental engine project, and just tested on the same flow rig achieved the flowing by comparison:

Inlet bare port flow 121 cfm - 30 deg seat prep'd for a 44mm valve
Exhaust: 88.5cfm

E/I ratio 73%, so more on the money.

Further and more importantly no loss in flow achieved with the header fitted, and in fact flow calming effect (tricky dicky setup) brought the E/I flow ratio up to 76.5%

So looking very interesting, coupled up with the right cam the 'ole 2.5ltr heads are going to put up an interesting fight against the 3ltr and per cc capability has greater potential when using the OE equipment as limiting factor.... A610s... better crank up the boost to 11...