Yeah, that is kinda strange, especially given the 3" is MUCH better than the 70mm, but the 63mm is only a tad better than the 3".

 

might wanto retune.
You will gain more tq !!

 

yeah I still don't understand this haha. must be the old back pressure theory, but if that is true why is a 3 inch better than 70mm? because it's bigger you say, but then why is 63 the best? hahah

 

This thread is blowing my mind!

 

you didn't log boost, and i think that's the missing piece of this puzzle. target AFR's would have been nice to see, too. i can only guess you're running the 12psi pulley? also, what management are you on?

i would have loved to see the boost curves. i understand they are always linear with centrifugal setups but things can get tricky up top towards redline (slipping belts will slip more depending on how humid/hot/cold/blah blah that day...)

i'm not saying that your exhaust experiments are altogether wrong but i think we're missing some data here.

 

uhhh yes !!! Sorry about that ! since I wrote it last night I forgot to include the boost data.
Im using the SOS 3inch pulley.
AEM EMS as engine management.
boost was the same of 14.6 psi on all runs (graphs on bottom of page)
Belt not slipping at all is achieved by 3M fabric glue spray (green bottle)!!!

Red is from my last setup ( not used)
Green is from FX70RR


Red is 3 inch
Green is 63mm

 

ahhh well done

now you've thrown me another curveball - i've never heard of anybody using 3M adhesive to prevent slippage. where do you apply it, and how long does it last before it needs to be re-applied?

all this being said, are you going to stay with your tanabe exhaust, or are you now going to experiment with various 63mm setups? also, what test pipe/cat setup did you run with the tanabe?

keep the info flowing - my supercharger is in the mail and i'd loved to be well educated before it gets here.

 

mike did you do a head gasket this time around?which system did you go with?how much boost are you planning on running?

 

Very interested in your cooling setup. Or if you have a link to where you saw this info, it would be very appreciated!

 

I recall talking to Mase about this a few years back, when I was planning my FI setup.

I think it has to do with exhaust velocity, not flow. The exhaust gases are exiting the smaller diameter exhausts at a MUCh faster rate than with a larger exhaust setup. The increase in exhaust velocity leads to a greater "scavenging effect" at the exhaust ports, effectively pulling the exhaust out faster.

I know this also affects turbo applications, but not to the same degree as teh scavenging effect is negated by the placement of the turbo between the exhaust ports and the downpipe. Mase's kit uses a 63mm downpipe, I think... If that is fed into a larger cat-back system, the added flow of the larger exhaust will increase exhaust velocity from the turbo (it will be flowing the same as the larger piping, so velocity must be increased). It does not make the turbo spool any faster, but will prevent it from "bottle necking" at the downpipe.

This is how I understand it...

John