AustenW

Can anyone give me any coments on the headflow in the graph below compared with other heads they have had tested?

measured at 28"

AustenW

Anyone?

From the above its running about 240cfm @ 0.5 inch lift @ 28 inches of water on an 81mm bore

andy@amt

What flow bench is it and what software.

AustenW

Superflow I think, its all calibrated correctly

Will check

group5turbo

The 230.4 CFM @ 28" is equivalent to 218 CFM @ 25" or 138 CFM @ 10"

By my calcs the engine should be good for around 59 BHP per cylinder - so if it's a four then 236 BHP - if everything else like the inlet tuning, cam lift & timing, exhaust tuning, CR, fueling and ignition are spot on.

However - if this was done at QEP - they usually use 25" on their flow bench so the numbers I have given would be wrong!

AustenW

The graph is showing 240cfm at 0.5 inch lift

It was measured at QEP with 25" of water

What will this equate to? is this good or bad?

(Its on my 5cyl Volvo / new RS engine with 4mm bigger valves)

group5turbo

I was reading of the printout at the top - not the graph - and that says maximum CFM of 230.4 for the head hi-lighted.

240CFM @ 25 inches is very good (I guess that is the head with a peak flow of 267.8CFM?). It means your engine has the potential to make around 65 BHP per cylinder - 325 BHP in total. That doesn't mean you will achieve that power - you need to get a lot of other things right and you may need some extreme engine speed.

QEP have achieved 287CFM @ 0.5" lift per cylinder on my four pot engine with 36.7mm inlet valves. I am very pleased with that!

AustenW

I run 35mm inlets what head is it you had tested? Lancia Delta?

group5turbo

Yes its a Delta/Thema head - Nick will tell you about it if you ask - he finished all the headwork including porting after Matt had begun investigations.

Do you know the length of the con-rods on your engine?

For longevity, I don't think you should rev your engine to much over 6300 rpm on a regular basis if you have a standard bottom end. That will limit the power as I think you will need over 8300 rpm to see more than 300 BHP.

AustenW

Matt told me about it, some great flow numbers there, what spec you building it too? what bhp you after?

group5turbo

It's actually going to be a turbo motor for racing, so the ultimate power will depend largely on the choice of turbo and what it can flow.

Though the flow figures indicate 312BHP @ 9600 rpm we can't get the engine to that speed safely, as my engine has the same 90mm stroke as yours. As a normally aspirated motor I conservatively expect about 270BHP @ 8300 rpm with the steel rods we are using - the bottome end is also overbored to 2.1 litre. This should produce just over 600BHP @ 1.5 bar boost - but we may run a smaller/less laggy turbo which will reduce that to a reliable 500BHP @ 7300 rpm with 1.4 bar boost.

The turbo mapping will control boost to limit torque to 400 lb/ft which is all the gearbox will take reliably without getting special parts made.

In Group A rally trim this engine produced 300BHP @ 7000 rpm on standard sized valves, limited only by the regulations as was the Cosworth. The 500BHP is I think adequate for my needs but also a very realistic target.

AustenW

Yours sounds like a nice engine, apparently the gearbox is the weakest link on those

I'm runing a 77mm steel crank and 152mm rods (rod ratio of almost 2:1)

Engine is a 2.1 litre

Will be reving it to 10k so should hoopefully see over 300bhp as I'm running some huge cams, high comp and staged injectors

group5turbo

I like the shorter stroke - but you will still have huge mean piston speeds at 10,000 rpm of nearly 26 metres per second! That's higher than current F1 which run about 24 metres per second @ 18,000 rpm - so I admire your confidence!

AustenW

9740rpm is at 25m/s on a 77mm stroke

It can run upto that in short blips which should be fine

RickyLee53

You'll be fine, current f1 engines could do 22,000rpm's if there wasnt a limit.

Stock Honda B18 has piston speeds of 24m/s on cast pistons, and a rod ratio of 1.58. We've reved them to 8700 on the stock bottom end without issues which is over 25m/s.

Stock Honda S2000 piston speeds of 25m/s.

Back to the topic,

What turbo do you intend to use?

group5turbo

I'm not sure if that question is to me, but if it is for the smaller turbo we will use a TTs205 - best TT have ever seen from this turbo is 583 BHP - and for higher BHP another custom spec turbo from Turbo Technics with a T66 compressor wheel.

AustenW

I'm keeping my engine nasp