I've had the Prototype velocity stack on my car for a while now, but never noticed this before (didnt pay attention)

First of all, those running velocity stacks, where are you getting your resonance point or points (for the high rpm apps)? Between 4,000 and 5,000 rpms at full throttle my car sees about .05 to .07 k/cm2 boost. Yeah i know its not really boost, but just a minor amount of positive pressure. It only does it right there, and probably again at about 9,000. (didnt try up there yet.) Everywhere else it doesnt read positive.

Idle is -760mmHG so i dont think my MAP is screwed up.

Just posting to see if anyone else has seen these results. A couple others running veloctiy stacks here had the resonance points around the same spot im seeing boost, you could see it on the dyno, cuz it leaned out there when the stack was put on.

Feel free to comment / add any input.

 

Try the FI forum

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revhard92si &raquo;</TD></TR><TR><TD CLASS="quote">Try the FI forum</TD></TR></TABLE>
he's not talking about turbo, lol

i have heard of slight FI with the itbs facing forward running down a drag strip. same thing with ram air setups.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Revhard92si &raquo;</TD></TR><TR><TD CLASS="quote">Try the FI forum</TD></TR></TABLE>

why? did u read or just comment?

 

i remember a story someone told me about tony shagday reading 1lb of boost when he was driving the skunk integra....urban legend maybe

 

Interesting topic. So how do you go about tuning with this hit of boost? Mimic it on the dyno and just tune it like that?

 

well on the dyno it wont read boost .......if it even occur.......its only happening down the track ....so i guess you read the datalog and see where its lean and fatten it up

 

I see. Very Interesting.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SUPERNATURAL &raquo;</TD></TR><TR><TD CLASS="quote">well on the dyno it wont read boost .......if it even occur.......its only happening down the track ....so i guess you read the datalog and see where its lean and fatten it up</TD></TR></TABLE>


Used2beAb16 is not running his V-stack for ram air. It is under hood and has a K&N filter on it.

I have a custmor w/ a AEM V2 also say that he was seing a small about of postive presure at certain RPMs. I am guessing that the resonance effect has something to do w/ it.

Maybe CAT will comment on this and teach us something new.

 

Don't all intakes do that to some effect when the intake valve closes? That is the basis of the resonance effect, the air builds pressure by slamming up against the intake valve and that energy forces it into the combustion chamber when the valve opens again.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rochesterricer &raquo;</TD></TR><TR><TD CLASS="quote">Don't all intakes do that to some effect when the intake valve closes? That is the basis of the resonance effect, the air builds pressure by slamming up against the intake valve and that energy forces it into the combustion chamber when the valve opens again.</TD></TR></TABLE>

If the V-stack is doing its job, then it may multiply this effect.

 

interesting point going here... im gonna have to pay attention to my guages next time i take my car for a spin(anytime now an-r ). keep the info coming.

 

ask google: "Helmholz resonance"

Longer velocity stacks = lower frequency for harmonics. #2 harmonic = strongest one generally practical to optimize for.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdm_ef9 &raquo;</TD></TR><TR><TD CLASS="quote">interesting point going here... im gonna have to pay attention to my guages next time i take my car for a spin(anytime now an-r ). keep the info coming.</TD></TR></TABLE>

Yeah check it out dude, I am just runnning a 3" short ram with the prototype stack and filter, behind the headlight. (not ram-air style like some people are assuming)

It wasnt occuring with the stock TB, IM, but over the winter i installed a crankcase vent. system, max-bore (70-65mm) tb, and AEBS intake manifold, and im seeing postive manifold pressure. (though its not much) Even with the stack, it didnt see postive pressure untill the mods listed here.

I noticed it because i set the timing and took it out for a spin, and when i pressed up on the vafc, Instead of logging the max rpm, it logged my highest manifold pressure. This had occured at 4,770 rpms. (I was only shifiting at 6,000 or so.) assuming the hermolz or whatever, there should be another resonance point around 9,000 but i didn't see if it sees postive pressure up there yet. heh,

Maybe ill try it out again today and see what i come up with. Lemme know if yours is going into the postive aswell.

 

I don't run a velocity stack, but I see positive pressure sometimes at around 9000 RPM.

The highest my V-AFC ever read was +2 kPa. Most of the time I break 0 to +1.

I'm running an AEBS manifold, Edelbrock 65mm TB, and an AEM cai.

 

Ohh ... just a tid bit of info on the Prototype Racing velocity stack.

I dynoed my car yesterday using it and all the runs were done w/ the filter on. A friend said "take the filter and see what you gain" and I said "Joe at Prototype said no loss in WHP if you use a filter, so what the hell let give it a try and see if Joe's is the man". Sure enough there was no gain by running w/out a filter. WHP was the same start to finish.

So the moral is run a frik'n filter and save your motor.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DDD &raquo;</TD></TR><TR><TD CLASS="quote">Ohh ... just a tid bit of info on the Prototype Racing velocity stack.

I dynoed my car yesterday using it and all the runs were done w/ the filter on.</TD></TR></TABLE>

Umm.. where are the plots? lets here some info.. also did u try with the stack on and off?? u cant just talk about dynoing and not give plots around here. heh

Anyone else dyno i might find interesting?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Used2beAb16 &raquo;</TD></TR><TR><TD CLASS="quote">

Umm.. where are the plots? lets here some info.. also did u try with the stack on and off?? u cant just talk about dynoing and not give plots around here. heh

Anyone else dyno i might find interesting? </TD></TR></TABLE>

I was down there again yesterday and for got to print the befor and after. I gete a plot next time I go down.

 

Sorry different car, but did do a log. It was a 2.oL VW 16V we were testing and with the stock intake manifold the most we got was 3in/hg. We then mod. the stock intake for more volume, we noticed that at about 3500rpm it went to .6psi and held that to red line 7200rpm. Every thing else was the same as before but the mod to the intake. fun car also shoot a blue flame out the exhaust tip that held for the run.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by monster007 &raquo;</TD></TR><TR><TD CLASS="quote">Sorry different car, but did do a log. It was a 2.oL VW 16V we were testing and with the stock intake manifold the most we got was 3in/hg. We then mod. the stock intake for more volume, we noticed that at about 3500rpm it went to .6psi and held that to red line 7200rpm. Every thing else was the same as before but the mod to the intake. fun car also shoot a blue flame out the exhaust tip that held for the run. </TD></TR></TABLE>

was all this done with a velocity stack?? or just an intake and cone filter?? What was the exact setup?

 

just an intake with a cone filter, the only change was the intake manifold.

 

I run the velocity intake and with the length of my intake piping the resonance is at 5,000 rpm.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b19coupe &raquo;</TD></TR><TR><TD CLASS="quote">I run the velocity intake and with the length of my intake piping the resonance is at 5,000 rpm.</TD></TR></TABLE>

I ran my intake piping as long as i could to try and get the most length, and it seems like mine peaks at 4,7XX rpms.