Thread: 50.8mm runners Too big??? Results on last page...

None of my equations come from the internet, period. If you have tried multiple runner lengths, would you post them with the corresponding dyno graphs please? I would love to know what lengths and diameters you have tested.

The diameter calculations I use are very simple, and as I have already mentioned aim to achieve an average velocity entering the head. This speed of 70m/s for peak power is universal. Ask any professional race engineer and you will hear a similar story. I have tested this on real engines and it works. This is also identical to the Honda CBR 1000RR which is making almost 200hp out of an engine half the displacement of our engines. These are simple things we all can learn from. That engine's induction system is very well made and miles ahead of anything using guesswork.

I think at this point everyone should know that literally any change to everything affects peak torque in some fashion, each of these changes create our torque line. When I say peak torque it is referring to that individual components efficiency point. Some things affect the torque output in a larger way...we all know this. You line all of these guys up for one rpm, bingo you make power.

If you disagree that is ok and your right to do so, I am just trying to gather information here for my own design and research and help some in the process if they care to listen.



Thank you Daves! Very valuable, this would reduce the needed runner length significantly to about 9inches to the bellmouth.

Payu,
I don't know if you care It looks like your runners are a bit short in length, but I am sure you are happy with the results. With Daves' new length, 8-9 is the magic length I'm pulling out of the hat. When your runners of 6.5inches become efficient you are well past the flow capabilities or rpm capabilities of the ve head. If anyone has tried these lengths I would love to hear about the results...

Walker

^^^ what you are saying its the stock runner length its the best choice but the problem its that there its no room on the engine bay to make an IM with 9in runners an a bigger plenum I tried to build it as long as possible actually mine came about to be a little bit over 7.5in plus a thermal gasket that has probably like .25in and still raised the peak power about 900rpm but.. peak torque came sooner about 500rpm.. But I am happy with the results at least it gave me gains... Maybe not Ideal but they would be Usable once my FD arrives not with stock FD...

That dip its created by the Tri-y header all cars here with the header have the dip if they scale the graph differently you wont see it....

interesting

@ payu

it's interesting that xs made 10whp and your custom intake make 14whp albeit it with different motor.

it would be nice to to a comparison of the 2 intake side by side
- plenum size
- runner length
- runner diameter
- etc

but even if this is not done, what would say caused the custom to make more power than the xs?

as THOR asked earlier, is it possible to overlay a xs IM graph over you custom IM grapgh (similar modded cars)?

will your custom IM clear the brake booster on RHD car?

thanks

peace

Beat the firewall in and it'll clear anything

lol endorsed!

actually niZmo i wanted to see overlayed with the stock set up he has.... seeing thou thats what most of the community has on now.... wouldnt ask him to dyno a excessive with this motor as that would come with a dyno cost

Here are some runner lengths I've already tested. They range from 7"-13". Sorry no corresponding dyno graphs since I spent too much time and money to give them away so easily.









As for the intake port length, they are 4.85" centerline. No guessing here because I made a mold and measured.