Low Boost question?

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
Over the last week I have been driving the Cobra more frequently, it's got a Stage 2 P-1SC with a 3.9 pulley, and I noticed I'm normally right around 6 psi, it briefly hit 7 psi but never higher. The last time I took it out, I got 5 psi. Though the amounts were different, the ramp rate was similar and it holds the boost level it peaks at... So I contacted Procharger and their response was that my full exhaust was likely contributing to the loss of boost, specifically my long tube headers. They recommended going to a 3.6 pulley.

I posted on the Procharger facebook group to see if the Procharger 3.6 would be sufficient or if I should spend the extra and get a ZPE Griptec 3.625 pulley? The response overwhelmingly favored Griptec, but a few people advised they thought it was belt slip. The tensioner is good, and with a 3.9 pulley on I wouldn't think belt slip would be an issue.

So what do you guys think? I don't want to invest a couple hundred in a Griptec 3.625 and then grenade the engine, because it was belt slip and I'm now over 10 psi between the belt slip being eliminated and a smaller pulley. Inversely I don't want to spend a couple hundred on a 3.9 Griptec pulley and still be sitting at 6 psi because there was no belt slip and my headers are causing the boost drop. Help please!
 

robvas

Well-Known Member
Established Member
Joined
Sep 8, 2020
Messages
1,317
Location
MI
You'll have belt dust (black powder) all over if it's belt slip. 3.9" would be a massive pulley for a Vortech. Sure your belt is good? Tensioner strong? Both of those items will wear out and make you lose boost.

You've checked for any leaks, right?
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
You'll have belt dust (black powder) all over if it's belt slip. 3.9" would be a massive pulley for a Vortech. Sure your belt is good? Tensioner strong? Both of those items will wear out and make you lose boost.

You've checked for any leaks, right?
Brand new Gates belt last year with only a few hundred miles on it, the tensioner requires quite a bit of force to move with a breaker bar so I assume it's good. I'll look for the black dust you mention.

I plan on doing a boost leak test this weekend. If that comes back good, would you go Griptec 3.625? Or would the Griptec be overkill for this size pulley?
 

01yellercobra

AKA slo984now
Established Member
Joined
Oct 5, 2005
Messages
21,128
Location
Cali
You'll have belt dust (black powder) all over if it's belt slip. 3.9" would be a massive pulley for a Vortech. Sure your belt is good? Tensioner strong? Both of those items will wear out and make you lose boost.

You've checked for any leaks, right?
He has a Procharger. Different step up ratio than the Vortechs.

OP, I wouldn't bother with the Griptec for either of those sizes. Even the 3.6 should have plenty of contact without any coatings. As mentioned get a good tensioner on there too.
 

DSG2003Mach1

Well-Known Member
Established Member
Premium Member
Joined
Apr 15, 2004
Messages
15,913
Location
Central Fl
Im one of the ones claiming belt slip. A 4" pulley at 7k on an otherwise stock car should be right at 10#. I just don't see how long tubes and OR midpipe dropped ~4psi.

at what rpm does boost go flat? A centrifugal ramps up with rpm at an increasing rate, at that pulley ratio on that motor the only thing that should make it flat line is slip

With that size belt where is the tensioner when you put the belt on? 0% would be tensioner position with belt off and just letting the tensioner spring all the way over. 100% would be putting a bar on it and breaking it over against the spring until it stops.
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
Im one of the ones claiming belt slip. A 4" pulley at 7k on an otherwise stock car should be right at 10#. I just don't see how long tubes and OR midpipe dropped ~4psi.

at what rpm does boost go flat? A centrifugal ramps up with rpm at an increasing rate, at that pulley ratio on that motor the only thing that should make it flat line is slip

With that size belt where is the tensioner when you put the belt on? 0% would be tensioner position with belt off and just letting the tensioner spring all the way over. 100% would be putting a bar on it and breaking it over against the spring until it stops.
I'll double check, I'm using a Gates K061140HD which was the belt recommended by Procharger. Wishing I had a MAP sensor, so I could data log for boost drops.
 

DSG2003Mach1

Well-Known Member
Established Member
Premium Member
Joined
Apr 15, 2004
Messages
15,913
Location
Central Fl
I'll double check, I'm using a Gates K061140HD which was the belt recommended by Procharger. Wishing I had a MAP sensor, so I could data log for boost drops.

Im sure someone smarter than me can chime in but I would think there would be a way to infer it by watching maf counts

and even though it's a newish belt, a couple hundred miles of slip can start to chew up a belt. The green belts are tougher than a standard belt but the trade off is they're probably a little harder and dont grip as well.
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
Im sure someone smarter than me can chime in but I would think there would be a way to infer it by watching maf counts

and even though it's a newish belt, a couple hundred miles of slip can start to chew up a belt. The green belts are tougher than a standard belt but the trade off is they're probably a little harder and dont grip as well.
Would you try a standard gates belt, or perhaps an gates rpm?
 

DSG2003Mach1

Well-Known Member
Established Member
Premium Member
Joined
Apr 15, 2004
Messages
15,913
Location
Central Fl
Id either try a new green belt the same size or see if you down a size if you can get a smaller belt on. I've been buying mine on amazon.

I dont think Id spend the money on an RPM until you have a handle on whats going on. Your combo isn't anything crazy that should be having major slip issues
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
Ok.... so....

When I get home, I need to:
- inspect belt for tension and condition.
- inspect tensioner (I'm guessing try to move it by hand, and maybe watch it with the engine running to see how much it moves at idle.

I have noticed a chirp that I thought was suspension, but could be the tensioner?

Depending on that, check for boost leaks.

If the tensioner is bad, would you use Gates or Dayco (Apparently the OEM is a Ford stamped Dayco tensioner)?
 
Last edited:

DSG2003Mach1

Well-Known Member
Established Member
Premium Member
Joined
Apr 15, 2004
Messages
15,913
Location
Central Fl
Ok.... so....

When I get home, I need to:
- inspect belt for tension and condition.
- inspect tensioner (I'm guessing try to move it by hand, and maybe watch it with the engine running to see how much it moves at idle.

I have noticed a chirp that I thought was suspension, but could be the tensioner?

Depending on that, check for boost leaks.

If the tensioner is bad, would you use Gates or Dayco (Apparently the OEM is a Ford stamped Dayco tensioner)?

a chirp could be the belt or an idler, get a spray bottle and hit it with some water - if it stops it's likely the belt.
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
a chirp could be the belt or an idler, get a spray bottle and hit it with some water - if it stops it's likely the belt.
It got a brand new idler pulley last year.

The chirp is only under load... so it's all speculation, but with potential belt slip on a new belt, new idler pulley, new alternator, it might be more evidence that perhaps the tensioner isn't providing enough tension.

Most everyone says it sounds like belt slip, and most everyone says belt slip shouldn't be an issue on a P-1SC with a 3.9 pulley.
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
67FC4CA2-BAE8-409B-AA61-CBDA5B1F2CF4.jpeg

View attachment 1762351Well found oil on the tensioner, so I’m going to guess the input shaft seal is leaking??? The oil dipstick was fully coated but I don’t know where else the oil could be coming from…
AEA6278E-F8BE-4D22-A023-85BD710F1628.jpeg
 

DSG2003Mach1

Well-Known Member
Established Member
Premium Member
Joined
Apr 15, 2004
Messages
15,913
Location
Central Fl
Take a picture of the engine bay that shows the pcv lines and how they’re connected

Mine would suck oil into the blower inlet and then leak out of the blower housing

If something’s dripping oil that’s getting in the belt that would definitely cause issues
 

robvas

Well-Known Member
Established Member
Joined
Sep 8, 2020
Messages
1,317
Location
MI
Is your BOV misting any oil onto the engine? Check one of your lowest intercooler pipes to see if there's any oil in it.
 

robvas

Well-Known Member
Established Member
Joined
Sep 8, 2020
Messages
1,317
Location
MI
Can you take a picture of your blower/existing pulley? From the pulley side
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
Take a picture of the engine bay that shows the pcv lines and how they’re connected

Mine would suck oil into the blower inlet and then leak out of the blower housing

If something’s dripping oil that’s getting in the belt that would definitely cause issues
The PCV hose isn’t currently connected to the power pipe. So it’s not blow by leaking through the blower. I’m the last picture you can see where part of the green backing is grey… not sure if that is oil or slippage?


Is your BOV misting any oil onto the engine? Check one of your lowest intercooler pipes to see if there's any oil in it.

I hadn’t considered that but this is more than misting.


Can you take a picture of your blower/existing pulley? From the pulley side

599CFB6B-6875-45A6-8D59-D0C889A695E6.jpeg


It’s tight and I know that doesn’t show much but when I wiped my finger under the pulley along the back of the Procharger there is oil under there. I replaced the input shaft seal roughly a year and a half ago when I first got the car because it appeared to have been leaking but I think I need to replace it again. I don’t want to put a new belt on until the oil leak is fixed.

Not sure if I should buy a press an attempt a rebuild myself, or send it off to have a pro go through it? Procharger confirmed this unit is from 2006 and I’m not sure it’s ever had an overhaul.
 

DSG2003Mach1

Well-Known Member
Established Member
Premium Member
Joined
Apr 15, 2004
Messages
15,913
Location
Central Fl
That green finish ends up blackish like that regardless. If there’s oil under that pulley it’s leaking again. I let procharger go through it, cost me a couple hundred bucks
 

Slow 99

Nothing to see here
Established Member
Joined
Sep 12, 2019
Messages
387
Location
California
Over the last week I have been driving the Cobra more frequently, it's got a Stage 2 P-1SC with a 3.9 pulley, and I noticed I'm normally right around 6 psi, it briefly hit 7 psi but never higher. The last time I took it out, I got 5 psi. Though the amounts were different, the ramp rate was similar and it holds the boost level it peaks at... So I contacted Procharger and their response was that my full exhaust was likely contributing to the loss of boost, specifically my long tube headers. They recommended going to a 3.6 pulley.

I posted on the Procharger facebook group to see if the Procharger 3.6 would be sufficient or if I should spend the extra and get a ZPE Griptec 3.625 pulley? The response overwhelmingly favored Griptec, but a few people advised they thought it was belt slip. The tensioner is good, and with a 3.9 pulley on I wouldn't think belt slip would be an issue.

So what do you guys think? I don't want to invest a couple hundred in a Griptec 3.625 and then grenade the engine, because it was belt slip and I'm now over 10 psi between the belt slip being eliminated and a smaller pulley. Inversely I don't want to spend a couple hundred on a 3.9 Griptec pulley and still be sitting at 6 psi because there was no belt slip and my headers are causing the boost drop. Help please!

Boost is a measure of restriction, so if you have a free flowing exhaust setup with minimal restrictions you'll make less boost but more power. Did you just recently install the long tubes after making the 7lbs to then get the 5lbs? with a 3.9 pulley, I'd highly doubt it's belt slip but I guess you can never rule it out
 

01silverstang

Well-Known Member
Established Member
Joined
Sep 22, 2004
Messages
1,172
Location
Batavia, IL
Boost is a measure of restriction, so if you have a free flowing exhaust setup with minimal restrictions you'll make less boost but more power. Did you just recently install the long tubes after making the 7lbs to then get the 5lbs? with a 3.9 pulley, I'd highly doubt it's belt slip but I guess you can never rule it out
No the car was purchased with the long tubes and blower installed. Local performance shop advised .5 to 1 psi drop from long tubes but not 4 lbs. Most everyone has agreed that I should be making around 10 lbs.
 

Users who are viewing this thread



Top