Intake Resonance Pulse Tuning: How to (very cool)

**Radar** · 11-02-2011, 03:29 PM

http://3tcgarage.com/viewtopic.php?f=37&t=56
Deff worth a read.

**Radar** · 11-02-2011, 06:38 PM

If anyone knows about this kinda thing, if the runners are tuned to be at 12 bounces at half RPM (i.e. 3500rpm,) and at full RPM (i.e. 7000rpm) 6 bounces. Can that work as a dual stage ram effect?
Also is it the lower the number of bounces *(as long as its an even number)* the better or is there an IDEAL number of bounces?

Thanks in advance

**Billzilla** · 11-02-2011, 08:13 PM

The lower number of reflections the better, as they are stronger - That's why my race engines often have very short inlets.

**Radar** · 13-02-2011, 08:32 PM

Very short inlets would create more bounces? To get two bounes at 7250 rpm I need runners that are over 22inches.

**Billzilla** · 13-02-2011, 08:43 PM

Originally Posted by Radar

Very short inlets would create more bounces? To get two bounes at 7250 rpm I need runners that are over 22inches.

That's a hugely long inlet compared to what I run - The racer has an inlet length about 1/3 of that.

**Radar** · 13-02-2011, 11:09 PM

Originally Posted by Billzilla

That's a hugely long inlet compared to what I run - The racer has an inlet length about 1/3 of that.

I always thought short runners for high rpm, ive just been using the above formula. Are there some other major things I should be taking into account in terms of runner length?

**Billzilla** · 14-02-2011, 10:02 AM

Not really, you just have to decide how many bumps you want to go with and how long/short the inlet runner is going to be .... or can be. On really high-rev engines you physically can't make the inlet short enough so you have to go for a double or triple bump type.

**oldcorollas** · 14-02-2011, 10:44 AM

need to also take into account the rev range you want.
either side of a strong single "bump" will be negative effects, so sometimes it is better to go for a weaker reflection, and not lose as much either side as well, and also get another "bump" or two into your rev range.

single bump manifold is ok if you have a narrow rev range.

also, runner length starts at the valve, so that could already be a good 6" there, so need to mke sure you are talkign the same language..
ie, 22" total vs an 8" manifold
22-6 = 16" manifold = twice the 8" manifold (but i think bill is talkign about 8" total anyway)
althought his image link no longer works, you can see int he preview, the relative strength of the 1st, 2nd etc harmonic strength...
ie, if you can't achieve 1st or 2nd harmonic, then 3rd to 4th etc is not that much different, and means you get more positve points within rev range
http://www.google.com.au/imgres?imgu...Disch:1&itbs=1

**Radar** · 14-02-2011, 11:46 AM

OC Im not 100% sure what you mean??
I was working off the total length from valve face to end of ITB.
According to formula in the link I posted, if I have worked my maths out, I can get the bump to hit right on 8bounces (8.002) at 3750rpm (500rpm after my cam actually kicks in).
And then 4 bounces just as my cam ends. I thought this is what I was aiming for?
If I want even less bounces I need to make my runners even longer. The shorter the runner the more bounces it has.
Just confused again I had always thought like bill said short runners for high rpm. But it seems to tune for ram effect you need long runners?
RPM / 60sec = ERpS (engine revs per second)
ERpS / 360degrees = CDpS (total crank degrees per second)
# of crank degrees inlet valve is actually closed / CDpS = IViC (Total time inlet valve is close at this RPM.)
So if I run a massive cam with a 288deg duration that only leaves 144degrees over 720degrees.
So from there its:
1125(speed of sound) x IViC = Pulse distance in ft. (convert into inches)
So its then
Pulse distance (inches) / Runner length (inches) to work out number of bounces.