port exhaust side for boost

[bjornmk1]

is it wise to enlarge/port the exhaust port side when
using a supercharger.(3400 heads on destroked block-3L)

logicaly there is a lot more air being fed to the inlet side..
so...???

so this must go out on the other side right ??

[Ortie666]

I would say, with supercharged motors big exhast and ports helps alot, and reduces tempatures

[Guest]

It is a common agreement that any power adder vehicle will have larger exhaust ports than an N/A engine would use as compared to the intake side.

In other words the exhaust ports flow more than the intake side could in theory support, if the engine were naturally aspirated.

[bjornmk1]

who has done this ...and what size/ratio
compaired to the intake would be good/effective ??

[Guest]

I don't know anyone that has done this to a 660, but many SBF and SBCs'.

IIRC the ratio was something around .65 to .75, that being that the exhaust sides 65 to 75 % of what the intake does, but it has been a long time since this was in great discussion. This was more for all out performance as the velocity at lower RPMs pretty much drops off, but at higher RPMs where it the flow is wanted and where the most difference between intake pressure or chemical adder are seen between the intake and exhaust.

I believe there is some discussion of this on www.grapeaperacing.com

[nocutt]

is it wise to enlarge/port the exhaust port side when
using a supercharger.(3400 heads on destroked block-3L)

logicaly there is a lot more air being fed to the inlet side..
so...???

so this must go out on the other side right ??

There is always power to be had when increasing the way the engine should breathe...period!
The question should be if you have reached the max potential on said heads at said boost? IMO on 20Xci porting the exhaust is not worth the gains to be had...it will be better to a.) move to a bigger or better designed head or b.) maximize the said heads with a better designed bumpstick...

Don't get me wrong if you are going to go thru the trouble of porting the exhaust you might as well do the intake, then get a bumpstick to compliment the mod and open up the exhaust...granted it is a fiero (already short exhaust)...nevertheless

[bjornmk1]

okay..guys,
the way I look at it now is :I won't enlarge the exhaust port
since it could effect the low rpm torque.

I guess i will leave it as it is right now.

the 3400 head on a 3L bore is already maxed out
on valve size..so it should breathe well for a 3L engine.

thanx,bjorn

[bjornmk1]

closed