Intake Port Size Affects - CIS

[klefroid]

Here was another good thread long time ago but may be usefully to.
Homebrew Head Porting: Attempting the dark art .....

Originally Posted by totle

Interesting. That golf ball effect in the port looks nice.
Wonder how much extra effect that gives.
My 930 tops was ported by extremecylinderheads. Wish hey had this tool then :-)

Yes golf balls have a fascinating aerodynamic.
https://www.youtube.com/watch?v=LvVuuaqCC7A

One day they shape the valves to

[Black_Hat]

more



Surface Turbulence – Article | metricmechanic.com

[klefroid]

Ok, they do exist, best to replace them every 20 hours
Williams MotoWerx - Over 20 years in the industry providing performance parts for motocross.

[RarlyL8]

Waste of effort for 1-2 HP. I'll add 1/100th bar boost.

Heads should be done soon, I'll post pics. Very exciting stuff!

[Alan L]

FWIW, I just opened my intakes to 38mm, and 38mm injector blocks. Installed Elgin cam - in between SC and 964. Didn't want to loose to much low end. I discussed all this with Chris before settling on parameters. He did say that going to 40mm intake still showed improvements on dyno.
I plan to test it all at track day next week, hopefully I can report some improvements.
Alan

[RarlyL8]

Please do Alan, real world data is all that matters!

We decided on 40mm intake / 37mm exhaust using anti reversion bumps along the path. Never done it exactly like that before so anxious to see how it all works out. Unfortunately that is not an isolated change so I probably won't be able to judge the merit of it in this case, it's just part of the package.

[Alan L]

Originally Posted by RarlyL8

Please do Alan, real world data is all that matters!

We decided on 40mm intake / 37mm exhaust using anti reversion bumps along the path. Never done it exactly like that before so anxious to see how it all works out. Unfortunately that is not an isolated change so I probably won't be able to judge the merit of it in this case, it's just part of the package.

Just back from my first track run after the following mods - Elgin cam (SC330 brian?), 38mm ports/injector housing, 964 IC. So more than one change, which is what you do while in there.
What I can report is a rocketship. The lag end doesn't seem to have changed, but the boost onset is probably not as vicious as previous (which I found beneficial for the track, half way round a corner with it nailed to WOT). The top end just keeps going - from mid range up. I was running out of fuel at the top end and had to short shift to keep the AFRs below 12.5. FWIW there were times in the 13s and no damage.
Short shifting, 0.8 boost, and 3 sec gain on previous lap times - and this is with a passenger in the car, and previous lap time set at 1.0bar. Once I get the tuning sorted..............
Regards
Alan

[RarlyL8]

3 second lap improvement sounds huge! Yes with those cams and head work the engine can move a lot more air.
We should be finished with the injection blocks soon and the heads will follow. Really excited to see how well it will all work together.

[Alan L]

The AFRs are climbing muuuch quicker than they used to after boost dump. This means as we go thru the mid-upper rev range the engine must be shifting muuuch more air. Previously I used to watch it steadily progress through about 0.5 AFR once the boost dump had settled. The boost dump is not noticeable now (the engine needs that fuel and gobbles it) and the numbers just shoot for the upper end within seconds. I was shifting at around 5,400 to keep it around 12.5. There is a lot of improvement in the post boost power, and I think the transition is a lot more manageable. It has improved the engine all round. (Which I think helps the track driveability - easier to get power down earlier).
Definitely a good change.
Regards
Alan