WTF????
3rd Gear Member
Joined: Nov 2004
Posts: 905
From: Bayside, New York
RE: WTF????
ORIGINAL: FoxGT
It is possible to lose 4psi from changing exhaust, but it would take a very very horrible setup. The mustangs exhaust isn't that bad on a stock setup even so, the more hp your engines making on the stock exhaust, the more psi you'll lose. The power loss you're feeling was from quite a bit of the exhaust staying inside the cylinder after the exhaust stroke, when the intake opened it pushed against the intake charge making more psi. And you got more power because the mixture was compressed more. Even so, you wouldn't lose 4 over it at those boost levels from the mustangs stock exhaust.
Air density around you has alot do to with the boost psi with a supercharger, turbo's compensate by measuring it themselves with the wastegate. Your s/c is always going to spin the same speed no matter what with that pulley. If the air is cooler you're going to pack more in. It won't be a huge difference, but there will be one.
The only thing the bypass will help is bleeding off. There are performance gains from it on a turbo because by venting the air faster you can keep the impeller spinning at high speed between shifts, but as you know your impeller speed is directly related to engine rpm. Having a better valve will just let the air out faster. The faster you let it out, the better on your parts it is. You don't need to go huge. Your car will tell you if it's too small with surge. If it's way too small you'll hear it without getting on the throttle, it's like a fluttering sound. If it's just a little bit too small you can hear it when you let off the gas. A properly sized one will have one "pshhhh" one that's too small you'll hear "psh psh psh psh"(imagine that at a really fast speed). Quite a few cars have ones that are too small though if you look at some videos they'll have a sort of flutter sound rather than having just one sound.
It is possible to lose 4psi from changing exhaust, but it would take a very very horrible setup. The mustangs exhaust isn't that bad on a stock setup even so, the more hp your engines making on the stock exhaust, the more psi you'll lose. The power loss you're feeling was from quite a bit of the exhaust staying inside the cylinder after the exhaust stroke, when the intake opened it pushed against the intake charge making more psi. And you got more power because the mixture was compressed more. Even so, you wouldn't lose 4 over it at those boost levels from the mustangs stock exhaust.
ORIGINAL: janine
Question:I recently up gradedthe ByPass valve in my 4.62Vfrom the little stock plastic 1/4 inch piston Vortech that comes with the kit to the bigger steel2"piston Vortech mini Race Bypass valve. Would that change in itself improveboost in an engine already putting out 14psi?
People say it only makes the car run a whole lot better -- which it certainly does. But I find my boost gauge hitting 15psi at times. I don't know if the sub freezingtemp (in NYCarea) has anything to do with this.
What is your take?
Question:I recently up gradedthe ByPass valve in my 4.62Vfrom the little stock plastic 1/4 inch piston Vortech that comes with the kit to the bigger steel2"piston Vortech mini Race Bypass valve. Would that change in itself improveboost in an engine already putting out 14psi?
People say it only makes the car run a whole lot better -- which it certainly does. But I find my boost gauge hitting 15psi at times. I don't know if the sub freezingtemp (in NYCarea) has anything to do with this.
What is your take?
The only thing the bypass will help is bleeding off. There are performance gains from it on a turbo because by venting the air faster you can keep the impeller spinning at high speed between shifts, but as you know your impeller speed is directly related to engine rpm. Having a better valve will just let the air out faster. The faster you let it out, the better on your parts it is. You don't need to go huge. Your car will tell you if it's too small with surge. If it's way too small you'll hear it without getting on the throttle, it's like a fluttering sound. If it's just a little bit too small you can hear it when you let off the gas. A properly sized one will have one "pshhhh" one that's too small you'll hear "psh psh psh psh"(imagine that at a really fast speed). Quite a few cars have ones that are too small though if you look at some videos they'll have a sort of flutter sound rather than having just one sound.
I didn't have any surging with the 3.60 pulley.The engine was putting out 6-8 psi and making 351 rwhp. When I put on the 3.25 pulley, I made 10-12 psi and felt surging over 3000 rpm on highway. This occured when I eased off throttle. Not nice but I dealt with it. When I went to a 2:78 pulley, the surging was so insane it wouldn't drive right but in 5th gear. That iswhy I spent the $500 for the Vortech Mini Race ByPass Valve,pipe set up and labor for the welding.
The results was simply outstanding. As far as added noise, when I let off the throttle and push down on the clutch, it makes a very nice whistle. Sounds like the cool turbo whistlesemi's make on the highway -- sort of. The sound definitely fits in with the car.
I gain a psi but have nowattribute that to cool dense air of brisk winter -- the time of year Mustang's thrive.
Thanks for your imput.You are the best I've heard since I joined this forum back in 2004.
Janine
6th Gear Member
Joined: Jun 2006
Posts: 5,693
From: Maine
RE: WTF????
my setup flutters, but only when I completely let off the gas after hauling ***. If I'm just driving at high RPM but at somethin glike half throttle, it sounds normal. But if I let off the gas after getting on it hard, you can hear a little flutter. Most likely because the throttle plate is closed and it has nowhere else to go.
I figured it was fine as long as it doesn't sound that way under normal conditions (driving at high RPM but less than WOT)
I figured it was fine as long as it doesn't sound that way under normal conditions (driving at high RPM but less than WOT)
3rd Gear Member
Joined: Nov 2004
Posts: 905
From: Bayside, New York
RE: WTF????
ORIGINAL: samseed101
my setup flutters, but only when I completely let off the gas after hauling ***. If I'm just driving at high RPM but at somethin glike half throttle, it sounds normal. But if I let off the gas after getting on it hard, you can hear a little flutter. Most likely because the throttle plate is closed and it has nowhere else to go.
I figured it was fine as long as it doesn't sound that way under normal conditions (driving at high RPM but less than WOT)
my setup flutters, but only when I completely let off the gas after hauling ***. If I'm just driving at high RPM but at somethin glike half throttle, it sounds normal. But if I let off the gas after getting on it hard, you can hear a little flutter. Most likely because the throttle plate is closed and it has nowhere else to go.
I figured it was fine as long as it doesn't sound that way under normal conditions (driving at high RPM but less than WOT)
Retired MF Moderator
Joined: Aug 2004
Posts: 14,891
RE: WTF????
ORIGINAL: janine
Yeah, right! Knock it off, Pea Head.
ORIGINAL: nanaki
that's odd. i have a 3.10" pulley on mine and i have no surging at all.
that's odd. i have a 3.10" pulley on mine and i have no surging at all.
3rd Gear Member
Joined: Nov 2004
Posts: 905
From: Bayside, New York
RE: WTF????
ORIGINAL: nanaki
knock what off? i'm running 13psi and i have no surging. 13.03 to be percise.
ORIGINAL: janine
What kind of By Pass Valve are you running?
Yeah, right! Knock it off, Pea Head.
ORIGINAL: nanaki
that's odd. i have a 3.10" pulley on mine and i have no surging at all.
that's odd. i have a 3.10" pulley on mine and i have no surging at all.
Yeah, right! Knock it off, Pea Head.
3rd Gear Member
Joined: Nov 2004
Posts: 905
From: Bayside, New York
RE: WTF????
ORIGINAL: nanaki
the one that came with my vortech kit
the one that came with my vortech kit
And if by some wild chance you not playing with me. How is that so running 13psi and that cheap,shi## valve?
6th Gear Member
Joined: Jun 2006
Posts: 5,693
From: Maine
RE: WTF????
ORIGINAL: janine
My 02 GT bucked or surgedbadly in any gear over 3000 rpm as soon as I eased off the throttle to hold rpm. I was running the stock Vortech Bypass Valve -- that little cheap black plastic one. Don't feel any more surging with the bigger valve.
ORIGINAL: samseed101
my setup flutters, but only when I completely let off the gas after hauling ***. If I'm just driving at high RPM but at somethin glike half throttle, it sounds normal. But if I let off the gas after getting on it hard, you can hear a little flutter. Most likely because the throttle plate is closed and it has nowhere else to go.
I figured it was fine as long as it doesn't sound that way under normal conditions (driving at high RPM but less than WOT)
my setup flutters, but only when I completely let off the gas after hauling ***. If I'm just driving at high RPM but at somethin glike half throttle, it sounds normal. But if I let off the gas after getting on it hard, you can hear a little flutter. Most likely because the throttle plate is closed and it has nowhere else to go.
I figured it was fine as long as it doesn't sound that way under normal conditions (driving at high RPM but less than WOT)
Like if I go from 5000 RPM and take my foot off the gas to close the TB plate...then it will flutter as it surges a little.