Intersting situation…

A mates car went on the dyno during the week and made some big numbers.

Interesting thing though, like mine, it fell flat above 7000rpm. No matter how much more boost or revs you pumped through it, the power peaked at like 7100rpm.

Turbo was a bigger version of the TA than mine...

Thoughts or comments?

 

Intake manifold restriction? Nature of side ports?

 

Intake restriction of the cosmo manifolds is what I am thinking.

Is anyone else making 500rwhp+ with standard cosmo inlet manifolds?

 

Stevie.

You ever seen a cut away version of the JC plenum chamber.....??

Its a wonder the damned thing flows 300hp let alone any more. I was over at Plazmaman's a while back & he had a 20B plenum cut open. The 13B one would be the same I reckon.

They may look good on the outside & flow well for low to mid range compared to the FD version, but the design theme for the JC was "touring" hence the mainifold configuration.

Thats my 2c............

 

mine is like falling off a cliff after 6500

mike

 

Dave - The general consensus is that the upper inlet is the ducks nuts, its the lower manifold that is restrictive...

 

Porting ?

Restrictive (late opening & early closing "near stock) primary inlet port timing kills power range.

I know for a fact from my own personal experience regardless of what gen intake manifold set up you have, a decent street port (with overlap and same primary/secondary opening timing and closing) will lift the peak rpm power point at least 500 to 1000 rpm and it will flaten out the peak torque curve too. That and exhaust ports that are opened up to the limit of the exhaust sleeve greatly help.

A different custom manifold would help a bit but if the engine has "coloured in mild ports" near factory timing all a custom intake will do is shift the point a bit.

Decent street port will make peak power in the 7200 to 7800rpm range when combined to factory manifolding and with custom intake manifolds, Near stock porting will struggle to make peak power much above 6700 to 6900rpm (and will greatly fall on its face at higher revs) and a street port with extreme custom intake will generally make peak power at 8700rpm or there abouts and not fall dramaticly untill about 9200rpm.

I have not herd of many people trying a full custom intake on a "mild ported" engine but this will obviously aleviate some of the issues (allow more flow and lift the rev range a bit).

For some solid numbers, 550 rwhp (dynojet) has been done at 19.4psi @ 7200rpm with a good street port on your gen engine with turbo only using stock intake manifolds.

 

send me an email and I will fax you the sheet

riceracing@ozemail.com.au