I think I am losing boost somewhere. I checked all vacum lines and they are snug and the intercooling piping is fine, What I was wondering is can you lose boost pressure to the vacum line going to the brak booster or is there a check valve of some sort in there?
Boost loss question...
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Gerald
Enthusiast
Do you know how to check belt slippage?
Dr Roof
Enthusiast
AB
if you are boosting and your boost gauge is going to say 10lbs and drops off your belt is loose or slipping.
do a 3rd or fourth gear run up at full boost to check and watch your boost gauge.
if you are boosting and your boost gauge is going to say 10lbs and drops off your belt is loose or slipping.
do a 3rd or fourth gear run up at full boost to check and watch your boost gauge.
Joseph Dell
Enthusiast
Or, there is one more possibility. Check your clamps (silicone hoses) and all inlets / outlets. The most likely place to lose some boost is at the blower outlet...
The most _likely_ thing is that your belt is toast. But if you are certain on the belt, check ALL the piping...
JD
The most _likely_ thing is that your belt is toast. But if you are certain on the belt, check ALL the piping...
JD
Dr Roof
Enthusiast
BTW
BE real careful when doing this, better yet have someone ride with you to look or use a camera mount!
I don't think I am having belt slippage problems...I have fabercated a belt tensioner screw to tighten down the belt. I didn't see any dust in the pulley area. I will have to double check it. I was data logging with the split sec box and as my rpms went up..so did my boost..
I also have this pulley that is suppose decrease the chance of slippage. The belt I have on right now covers about 75% of the pulley.
The black pulley to my right is a 3.75" and the silver one is a 2.70". What gets me is that I am only seeing about 7-8 lbs of boost at around 5500 RPMs. I should be seeing somewhere in the range of 11-15PSI. I have Jeff Morey heads with a compression of 8.9 to 1, larger intake valves, exit valves, T&D 1.7 roller rockers. I have 3" exhaust all the way back to the rear and no cats. Any other guesses? I was also wondering if the IAV valve could be leaking also?
Other than the boost being down right now, the car has still gobs of power and torque...I litterly went side ways on the road when I stepped on the gas...but I know it has a lot more. I finally got her on the road today to do some data logging. I am seeing around 11-11.5 to 1 on air to fuel...and idling at about 14-16 to 1. Car idles great and smooth transistion through out the fuel map.
I also have this pulley that is suppose decrease the chance of slippage. The belt I have on right now covers about 75% of the pulley.
The black pulley to my right is a 3.75" and the silver one is a 2.70". What gets me is that I am only seeing about 7-8 lbs of boost at around 5500 RPMs. I should be seeing somewhere in the range of 11-15PSI. I have Jeff Morey heads with a compression of 8.9 to 1, larger intake valves, exit valves, T&D 1.7 roller rockers. I have 3" exhaust all the way back to the rear and no cats. Any other guesses? I was also wondering if the IAV valve could be leaking also?
Other than the boost being down right now, the car has still gobs of power and torque...I litterly went side ways on the road when I stepped on the gas...but I know it has a lot more. I finally got her on the road today to do some data logging. I am seeing around 11-11.5 to 1 on air to fuel...and idling at about 14-16 to 1. Car idles great and smooth transistion through out the fuel map.
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Dr Roof
Enthusiast
CHECK THE BELT! TIGHTEN IT!
Joseph Dell
Enthusiast
The other place you could lose a _little_ boost is the piping to the gauge itself. I'm not sure where you are tapping the vacuum line from, (not that we have many choices), but check that too. those platic T's can sometimes crack.
Did you used to see more boost than this before? with a free-flowing exhaust and well ported heads, a 10lb pulley will only see 8 lbs of boost, so this may not be all bad... but again, i don't know what you had before.
JD
Did you used to see more boost than this before? with a free-flowing exhaust and well ported heads, a 10lb pulley will only see 8 lbs of boost, so this may not be all bad... but again, i don't know what you had before.
JD
josesph,
What size pulley do you have? how much PSI? I will have to recheck the belt tension, but the belt tension is pretty darn tight already....if you torque it down anymore, it might snap... The Pulley I have is about a 14-15 lb pulley...
What size pulley do you have? how much PSI? I will have to recheck the belt tension, but the belt tension is pretty darn tight already....if you torque it down anymore, it might snap... The Pulley I have is about a 14-15 lb pulley...
Gerald
Enthusiast
Most likely your belt is slipping some. Look at your boost gage. Ramp it up in 4th and see if it's steady or steadily climbing. Any static movement of the needle and your loosing boost from a slipping belt.
What about your blowoff valve? Is that sticking open? closed? Every Hose clamP? Under Boost they can expand..
G
What about your blowoff valve? Is that sticking open? closed? Every Hose clamP? Under Boost they can expand..
G
Marc Lublin
Enthusiast
AB most probably your belt is slipping. You don't need to see dust for it to slip. Try tightening and see if you get any higher peak boost. How many ribs is you belt? If you want to be pushing the higher boost #'s, I believe you will need a 10 rib belt.
I am using an 8 rib belt system. I would have preferred the 10 rib belt system, but didn't have access to it. I know plenty of people on the 8 rib system that have the 16 psi pressure....When you look at my belt or grab it, there is hardley any slack or availble movement on it.
Bill B
Enthusiast
Boost is resistance. If you have ported your heads and intake the pressure will drop but the volume will increase.
DynoDaddy
Viper Owner
I think you might be loosing only 2 psi somewhere. With those heads, CR, and exhasut you might only see 10-11psi on a 14# pully. I have seen many cobras drop 2 psi with the addition of dual 3" exhasut. 3psi more with ported heads/intake.
Do you have an intercooler? If so that could be the culprit of 1-2psi pressure drop depending on its style. Double check every pipe, ect. If you suspect the brake booster, take the hose off and plug it. See if the PSI goes up after that.
Another suggestion, get some of those little rubber plugs and start plugging all of the little vacuum lines that are not immediatly necessary, i.e. A/C controls ect. Elliminate all the small issues.
I hope that you have T bolt clanps on all of your piping as well. THe screw clamps are worthless POS. THey will let air blowby but not pop off. Best of luck, keep us informed.
Do you have an intercooler? If so that could be the culprit of 1-2psi pressure drop depending on its style. Double check every pipe, ect. If you suspect the brake booster, take the hose off and plug it. See if the PSI goes up after that.
Another suggestion, get some of those little rubber plugs and start plugging all of the little vacuum lines that are not immediatly necessary, i.e. A/C controls ect. Elliminate all the small issues.
I hope that you have T bolt clanps on all of your piping as well. THe screw clamps are worthless POS. THey will let air blowby but not pop off. Best of luck, keep us informed.
Yeah I need to figure out the boost I should be making on my car with the pulley.
My heads specs are as follows:
2.040 Intake
1.600 Exhaust
Stainless valves
Bronze valve guides
Int, Exh, ductile iron seats
Crower duel valve springs 130lbs closed and 360 open pressure.
Crower titanium retainers
Crower spring locators
Compression 8.9 to 1
1.7 T&D
3" no cats Exhaust
Lower crank pulley for the paxton is the same diameter as the stock accessory crank pulley is with a 2.70 blower pulley. So what would that be in PSI?
My heads specs are as follows:
2.040 Intake
1.600 Exhaust
Stainless valves
Bronze valve guides
Int, Exh, ductile iron seats
Crower duel valve springs 130lbs closed and 360 open pressure.
Crower titanium retainers
Crower spring locators
Compression 8.9 to 1
1.7 T&D
3" no cats Exhaust
Lower crank pulley for the paxton is the same diameter as the stock accessory crank pulley is with a 2.70 blower pulley. So what would that be in PSI?
Gerald
Enthusiast
What does your boost gauge with your foot to the floor at redline in 3rd or 4th?
DynoDaddy
Viper Owner
You probably already know this, but impellor speed will only give you a rough guesstimate of what the PSI on your engine will be.
In the end it is all a function of the backpressure created by the engine that the SC is feeding. This directly correlates to the effectiveness to pump air through the engine. The variables are displacement, headflow, exhaust flow, intake flow, ect.
For example:
Let's say the impellor of a NOVI 2K is turning at 30,000 rpm. This SC will make 15psi boost on a 4.6L engine while on an 8.0L will only make 7psi. This is due to the increased displacement in which the CFM of the SC can fill up in the cyl. This is much like taking a 50gallon tank with 50 psi, and transferring all of that air into a 100 gallon tank. What would happen? You would most likely get 25psi or less in the 100 gallon tank. Nothing changed except the volume of the tank. Still the same cubic feet or air.
The first thing to figure out is if you have a leak, or belt is sliping. WIth hat pully and the tension that you said you have on it, I seriously doubt it is the belt. What you need to do is to run the car up under load at watch that boost gauge. If it keeps rising until redline you are good to go. IF it stops short I would bet that it is a leak somewhere. This being based upon the small amount of boost that you are producing.
Remember just because you only have 8psi does not necessarily mean you have a problem. It is most likely a good indication that the rest of your system is optimized. (Heads, intake, exhaust ect)
I hope this helps.
In the end it is all a function of the backpressure created by the engine that the SC is feeding. This directly correlates to the effectiveness to pump air through the engine. The variables are displacement, headflow, exhaust flow, intake flow, ect.
For example:
Let's say the impellor of a NOVI 2K is turning at 30,000 rpm. This SC will make 15psi boost on a 4.6L engine while on an 8.0L will only make 7psi. This is due to the increased displacement in which the CFM of the SC can fill up in the cyl. This is much like taking a 50gallon tank with 50 psi, and transferring all of that air into a 100 gallon tank. What would happen? You would most likely get 25psi or less in the 100 gallon tank. Nothing changed except the volume of the tank. Still the same cubic feet or air.
The first thing to figure out is if you have a leak, or belt is sliping. WIth hat pully and the tension that you said you have on it, I seriously doubt it is the belt. What you need to do is to run the car up under load at watch that boost gauge. If it keeps rising until redline you are good to go. IF it stops short I would bet that it is a leak somewhere. This being based upon the small amount of boost that you are producing.
Remember just because you only have 8psi does not necessarily mean you have a problem. It is most likely a good indication that the rest of your system is optimized. (Heads, intake, exhaust ect)
I hope this helps.
Dyno Daddy! Thanks!! VEry nice write up! I may see 8 psi at the most and I think that is on top of 3rd gear...I will have to try it on top of 4th and see what happens. I was thinking that my system flows so much that the PSI would drop, but then at the same time, J Dell is seeing around 15-16 psi on his. I think we both have the same size crank pulley and he has heads that flow well also.
I am happy we have a long weekend! I have some snooping around to do!
I am happy we have a long weekend! I have some snooping around to do!
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Adam, that doesnt look like an 800hp filter, looks like a 300hp filter NA, maybe 550hp for blown motor. Pick a non dusty day and try a run without the filter, at least that way you could eliminate it as a problem if it doesnt make a difference.
DynoDaddy
Viper Owner
YOu should not see any more boost in the top of 4th than you did in 3rd.
Good thinking though Joel.
IF he is indeed running 15psi with hte same crank pully and 2.70 pully and has the same heads then you are loosing psi somewhere. That is far too much of a drop between cars. Get to hunting for leaks. Try looking at the PVC valve if you are running one. You will not be able to run a PVC valve with forced induction. Also the IACV, TB gasket, intake gasket, ect. Best of luck.
Good thinking though Joel.
IF he is indeed running 15psi with hte same crank pully and 2.70 pully and has the same heads then you are loosing psi somewhere. That is far too much of a drop between cars. Get to hunting for leaks. Try looking at the PVC valve if you are running one. You will not be able to run a PVC valve with forced induction. Also the IACV, TB gasket, intake gasket, ect. Best of luck.
Joseph Dell
Enthusiast
I'm not running a paxton kit, so I have no idea if my crank and blower pulleys are the same as yours. since mine is a DLM special and it is a 10 rib belt, i doubt that you can compare my motor to yours. but then again. perhaps you can. best thing to do is to compare your setup to your setup. i know what amount of boost i was seeing pre-head work. and i see the change post head-work. what about you? just b/c the number isn't 15lb doesn't mean that there is something wrong...
JD
JD
It's the same filter DLM uses on his cars.
As far as being the same as J Dell, what I meant was "if" the crank pulley was the same diameter, then we should see some where near the same boost.
The Paxton kit is pretty much gone. The only thing I am really using is the Novie 2000, brakcet and lower crank pulley...everything else was taken off and the new stuff was custom fabercated with aluminum.
I took all day today and tighten down belts, IC clamps and double checked all vacum lines.
Dyno Daddy, you say I can't run a PCV valve? The PCV Valve I have opens when there is vacum and shuts when there is pressure...But when I took off my throttle bodies today, I did notice oil in the intake. Not a lot but enough to get your fingers wet with it. I think the PCV Valve I have maybe sucking in oil...
Gerald
Enthusiast
For crying OUT LOUD Adam, did you ramp it up on 3rd and 4th and look at your boost guage yet as we posted a few days ago? 
15 psi on a 8 rib? I'll get belt slip if Im' not tight on 10lbs!!!
Gerald
15 psi on a 8 rib? I'll get belt slip if Im' not tight on 10lbs!!!
Gerald
Gerald the reason why you have belt slippage is not due to the DLM product, but because of the WD-40 you use to spray on everything! LOL!! Don't forget who helped ya get in the 10's in a indirect way!
That air filter still looks restrictive to me, but if DLM are getting results....... If its the steel mesh type, they don't filter well, keep the flys out but let the dust through...
http://www.mkiv.com/techarticles/filters_test/2/index.html
http://www.mkiv.com/techarticles/filters_test/2/index.html
Gerald
Enthusiast
YOu still haven't checked your belt slippage. Your scared to boost your car up to it's limits! LOL!!!
Noone post another damn thing until he checks for belt slippage. He's a stubborn APE and skuuuuuuuuuuuurd
hahah
G
Noone post another damn thing until he checks for belt slippage. He's a stubborn APE and skuuuuuuuuuuuurd
hahah
G
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