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KLDE Runner length pressure waves needed (speed of sound)
KFC - 14/9/15 at 09:42 AM

Hi,
I'm still doing the V6 swap on a RX8 that I'm about 75% done. I'm trying to decide how long the trumpets should be for good torque low down. I have the room for longer trumpets so if it's worth doing, I will do.
I've found various websites to calculate the length, I just need the speed of sound figure to put it. Has anyone found this for the KLDE V6 engine?

Cheers

Ugg10 - 14/9/15 at 10:59 AM

The speed of sound (through air) changes depending on the altitude/barometric pressure and temperature but 340m/s is a pretty good average for the UK.

Jenvey website has some reasonable estimates - http://www.jenvey.co.uk/faq/general-faq

So based on a 200hp at 6000rpm, 2.5l v6 this seems to indicate -

35-40mm throttle body butterfly diam (injector between butterfly and valve can take the larger end) with an overall (end of trumpet to valve) distance of 525mm with the butterfly-valve distance of around 200mm and the injectors nearer the valve for better low speed response/power.

KFC - 14/9/15 at 12:07 PM

quote:
Originally posted by Ugg10
The speed of sound (through air) changes depending on the altitude/barometric pressure and temperature but 340m/s is a pretty good average for the UK.

Jenvey website has some reasonable estimates - http://www.jenvey.co.uk/faq/general-faq

So based on a 200hp at 6000rpm, 2.5l v6 this seems to indicate -

35-40mm throttle body butterfly diam (injector between butterfly and valve can take the larger end) with an overall (end of trumpet to valve) distance of 525mm with the butterfly-valve distance of around 200mm and the injectors nearer the valve for better low speed response/power.


Wow, that was a quick response! Thanks for the info. I don't know the measurement from the valve yet but from the head flange I can run up to 170mm.
I would like the peak torque lower down as this will be my comuter.

Ugg10 - 14/9/15 at 01:32 PM

No problems, don't suppose you need any exhaust headers, I have a brand new set of stainless ones that could be yours to modify for a few beer tokens (they are FWD but the headers can be used without the cross pipe) -



KFC - 14/9/15 at 02:07 PM

quote:
Originally posted by Ugg10
No problems, don't suppose you need any exhaust headers, I have a brand new set of stainless ones that could be yours to modify for a few beer tokens (they are FWD but the headers can be used without the cross pipe) -





I bought the exact same set about a year ago, then sold the down pipe. A shame I can't attach the photo I have under the car from my phone. I'll have to do it later on my laptop.