FPR Vacuum?

Nixon1 · 03-07-2003, 02:01 PM

This is a question I'm curious about with a friend of mine... He's got, I think it's an 88, GT with a 5 speed...performance clutch, shift kit, short-throw, Moroso Cold Air Intake Arm & Filter, Hooker Super Comp headers, H pipe, Flowmasters, and he SAYS it's got a cam in it.. But besides all this..the car is TRASH... The motor is filthy and it's a big time hackjob...although we thought he did a nice clutch dump in front of us on videotape until we replayed the tape slow-mo and noticed that a vast majority of the cloud of white smoke we were engulfed by came from his turndowns, NOT his tires.

To the question though..HOW necessary is vacuum to a stock fuel pressure regulator? Among the things hacked together on his car, his FPR has no vacuum line going to it whatsoever. The line is cut open about 1 in. past the regulator and leads to nowhere. Car still runs very hard...just the motor sounds like crap. He's been wanting to race me at the track for some time now and I'm just trying to get an idea of HOW screwed up his car is, to know if I can still beat him even though he's got more modifications. I hate losing money.

Thanks all.

PKRWUD · 03-11-2003, 09:41 AM

It's very necessary. The vacuum is what determines the final fuel pressure. When you are at WOT, there is no manifold vacuum, so the spring inside the FPR opens up the diaphram all the way, allowing maximum fuel pressure. When you back off the throttle, the manifold vacuum rises, and creates resistance against the spring, reducing the fuel pressure. Afterall, when you're backing off the throttle, you want lower pressure. If your friend has no vacuum applied to the FPR, then the pressure will be too high.

I'm surprised the smoke coming from his turndowns wasn't black. Check his oil, and smell the end of the dipstick. It'll smell like gas. His bearings are being eaten away, and his rings aren't sealing. Basically, he's killing his engine rather quickly.

Take care,
~Chris

Nixon1 · 03-11-2003, 08:21 PM

I kinda figured it was a very important piece..lol...his car is HACKED. And I thought MINE was a hack job when I got hit....his has vacuum lines cut off everywhere, disconnected cables and sensors, all sorts of crap....argh.... He has two individual toggle switches to run his damn turn signals! I hate to see it cause this is probably the fastest car he's ever owned, and he's just gonna leave it to blow up.... I'll try to convince him to buy a damn vacuum line....

Nixon1 · 03-12-2003, 02:00 PM

Hmm...he went out and bought a 222 watt Sony XPlod amp yesterday to power his two Kenwood 10's.....instead of fixing the 4000 things wrong with his car, he goes and buys an amp! Ahhhh!

PKRWUD · 03-12-2003, 11:18 PM

That way he doesn't have to listen to it grenade. Pretty clever.

Take care,
~Chris

Shogun · 03-13-2003, 01:17 AM

LOL! Ya, if he's bellowing white smoke out of the turn downs, he has FAR bigger issues to deal with than a vaccum line to the FPR. call out the Bugle platoon, they will play taps soon!

Nixon1 · 03-13-2003, 05:04 PM

Well most of the time I never see smoke...but he's got turndowns so it's less obvious. But the time he punched it..whewee...blue and white/gray EVERYWHERE. Usually it just pushes a lot of blue, with a LITTLE white when he gets on it..

03-07-2003, 02:01 PM	#1
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	FPR Vacuum? This is a question I'm curious about with a friend of mine... He's got, I think it's an 88, GT with a 5 speed...performance clutch, shift kit, short-throw, Moroso Cold Air Intake Arm & Filter, Hooker Super Comp headers, H pipe, Flowmasters, and he SAYS it's got a cam in it.. But besides all this..the car is TRASH... The motor is filthy and it's a big time hackjob...although we thought he did a nice clutch dump in front of us on videotape until we replayed the tape slow-mo and noticed that a vast majority of the cloud of white smoke we were engulfed by came from his turndowns, NOT his tires. To the question though..HOW necessary is vacuum to a stock fuel pressure regulator? Among the things hacked together on his car, his FPR has no vacuum line going to it whatsoever. The line is cut open about 1 in. past the regulator and leads to nowhere. Car still runs very hard...just the motor sounds like crap. He's been wanting to race me at the track for some time now and I'm just trying to get an idea of HOW screwed up his car is, to know if I can still beat him even though he's got more modifications. I hate losing money. Thanks all. __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

03-11-2003, 09:41 AM	#2
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	It's very necessary. The vacuum is what determines the final fuel pressure. When you are at WOT, there is no manifold vacuum, so the spring inside the FPR opens up the diaphram all the way, allowing maximum fuel pressure. When you back off the throttle, the manifold vacuum rises, and creates resistance against the spring, reducing the fuel pressure. Afterall, when you're backing off the throttle, you want lower pressure. If your friend has no vacuum applied to the FPR, then the pressure will be too high. I'm surprised the smoke coming from his turndowns wasn't black. Check his oil, and smell the end of the dipstick. It'll smell like gas. His bearings are being eaten away, and his rings aren't sealing. Basically, he's killing his engine rather quickly. Take care, ~Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

03-11-2003, 08:21 PM	#3
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	I kinda figured it was a very important piece..lol...his car is HACKED. And I thought MINE was a hack job when I got hit....his has vacuum lines cut off everywhere, disconnected cables and sensors, all sorts of crap....argh.... He has two individual toggle switches to run his damn turn signals! I hate to see it cause this is probably the fastest car he's ever owned, and he's just gonna leave it to blow up.... I'll try to convince him to buy a damn vacuum line.... __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

03-12-2003, 02:00 PM	#4
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	Hmm...he went out and bought a 222 watt Sony XPlod amp yesterday to power his two Kenwood 10's.....instead of fixing the 4000 things wrong with his car, he goes and buys an amp! Ahhhh! __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

03-12-2003, 11:18 PM	#5
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	That way he doesn't have to listen to it grenade. Pretty clever. Take care, ~Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

03-13-2003, 01:17 AM	#6
Shogun Registered Member Join Date: Feb 2002 Location: Nebraska Posts: 86	LOL! Ya, if he's bellowing white smoke out of the turn downs, he has FAR bigger issues to deal with than a vaccum line to the FPR. call out the Bugle platoon, they will play taps soon! __________________ Proud RHC member #99 1990 Mustang GT Trick Flow heads,F303,Mac cold air,FMS 65mm tb,73mm ma,FMS 1.6,GT-40 intake,MSD igintion,NOS Big Shot@150,Mac equal shorties,Mac h-pipe,American Thunder flows,Centerforce dual friction,TTC 3550,alm drive shaft, 3.73's, HPM subframes, k-member brace, strut tower brace.. amongst others.

03-13-2003, 05:04 PM	#7
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	Well most of the time I never see smoke...but he's got turndowns so it's less obvious. But the time he punched it..whewee...blue and white/gray EVERYWHERE. Usually it just pushes a lot of blue, with a LITTLE white when he gets on it.. __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

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