I beg to differ. You do need a bypass valve even if its only 5-6 psi for the car to idle correctly.
Why am i running a second slower with the charger?!!
- Thread starter SiK91LX
- Start date
A blower like that wouldn't make any boost at idle to begin with, but the valve's a good idea cause it vents boost when you snap the throttle shut to aviod over pressurizing the intake plenum. Anyway, SiK91LX, this is what you gotta do before we can make any progress. Get a Boost/Vacuum Guage. Hook it up and check much much vacuum at idea you're pulling (Should be at least 20mg with a stock cam). Then rev the motor up least 3k, maybe 5k and see how much boost you're pushing. From there we can get an idea of what's going on. Also, what you really need as well is a A/F ratio gauge, you shouldn't really tune a s/c motor without on. Anyway, your problem sounds like you've got a vacuum leak and your FMU isn't operating like it should cuz your boost is blowing off.
It does sound like vaccum leak.I have the performer intake with stock heads and cam and it made a hell of a difference.A good place to check for leaks is the tree of vacuum lines under the drivers side intake top.That is were your pcv should be going and it feeds vacuum to the tree on the firewall.If all of your hard lines are broken on the passenger side follow them back to the tree on the firewall and plug it.The vacuum line going to the egr valve should be pluged in with no leaks.The side cover on the upper intake is also a good place to check for leaks.There is a line from the upper intake going down to the smog pump.It is behind the distributor.When you check vacuum get a t and put a small length of hose on it.Then unplug a hose that has vacuum all the time from the firewall tree and put that hose on the t and plug your small hose were you took the one off.The last part of the t is where the line from gauge goes.It is easy to get your short length of hose of the one that comes with the gauge.Then check vacuum.
onefaststang said:
This is about the only sound advise I've seen in this thread so far. Your car has issues that need to be resolved. Throwing money and parts at it is not going to solve your problem. I know I've said it before but it never ceases to amaze me that so many folks throw together so many problems into a combination all at one time then have no means whatsoever to tune it. If you already knew that there were problems after the intake install then I would suggest that you back the truck up to that point and get those issue resolved before adding more issues. Tossing boost ontop of an already existing problem is only going to make matters worse.
If you don't have the means to monitor the vitals of that motor under boost then you need to take to someplace that CAN monitor those vitals for at least as long as it takes to get a proper tune. Fuel Pressure / Boost / AFR are REQUIRED vitals for tuning just about any car. The tolerances for those things narrow even more with forced induction.
Edit: Also... the 24's and an FMU is more than enough for that combination if properly tuned. Once you resolve the Vac issues you may even discover that the FMU you're currently running is ramping pressure up either too high or too fast but again.... you'll need to resolve the vac issues to find out. You do not require a bypass valve for that blower. If the blower is not providing enough flow for idle or part power the motor will 'draw' the air it needs through the blower and past the impellor. That's in the nature of centrifugal blowers. They are not true 'sealed' air pumps nor do they positively displace air. They're more of a 'fan' than anything else.
SiK91LX said:
Ok, first of all you need to plug/hook up right that line that you have a breather on. Thats a huge vacuum leak on its on. Get a PCV and get it hooked up right.
Second, if that line running off the FMU is running behind the intake and not on to the vacuum tree(probably where most will pull vacuum for the FMU) I think it is the B/R port(might not be right, cant remember for sure) anyways if its not hooked up then your FMU isnt working anyways.SiK91LX said:
You have a lot of problems that wont take no time to fix. Good luck
Ranchero5.0
The Voice of Reason
Gawd what a mess...
If those who haven't been there or don't know would just shut up this thread would not be so F'd up. Before we continue please read my signature.
As said above you need all the vacuum lines hooked up correctly, including the PCV system (the pcv itself can handle the 5-7psi of boost against the check valve easily). The only hose you block off is the clean air line from the throttle body to the valve cover oil fill cap tower (it'll allow boosted pressure into the crankcase and blow out the dipstick and some seals under boost). I pull the hose barb out of the TB and tap it for a 1/8" NPT fitting and plug it. If those two vacuum lines are screwed up you'll lose all your pressure there.
For the Paxton, from experience I do recommend a 1" bosch bypass from a Saab turbo car because it will allow cruising speed boost to bleed off back to the inlet side of the blower. Remember, boost is heat and at part thottle you have boost between the blower and throttle plates. Plus the extra boost is hard on the ball drive and generates a lot of heat in the blower. Replace the fluid with a good synthetic and you will pick up 1-2psi of boost. Replace the inlet and outlet pipes with 3" power pipes and you'll get more power out too. I'm still getting 6-7psi out of mine with stock pulleys even pushing through these high flowing heads (stock motor will see 7-9psi). IN my case, the FMU, timing master and blow off valve are all hooked into the back of the intake on a common line.
For timing with 92 octane I run 14 degree initial with the spout out with a boost retard set at 1.25 degrees/ pound of boost. Fuel sets at 45psi no vacuum with a stock FMU setup and 24lb injectors. Makes for a wicked torque curve. Only gripe is if I shift too slowly at 6k and floor it again it'll ping for a split second because the FMU drops pressure under vacuum. In a race situation it's fine.
Hope this helps;
Jamie
If those who haven't been there or don't know would just shut up this thread would not be so F'd up. Before we continue please read my signature.
As said above you need all the vacuum lines hooked up correctly, including the PCV system (the pcv itself can handle the 5-7psi of boost against the check valve easily). The only hose you block off is the clean air line from the throttle body to the valve cover oil fill cap tower (it'll allow boosted pressure into the crankcase and blow out the dipstick and some seals under boost). I pull the hose barb out of the TB and tap it for a 1/8" NPT fitting and plug it. If those two vacuum lines are screwed up you'll lose all your pressure there.
For the Paxton, from experience I do recommend a 1" bosch bypass from a Saab turbo car because it will allow cruising speed boost to bleed off back to the inlet side of the blower. Remember, boost is heat and at part thottle you have boost between the blower and throttle plates. Plus the extra boost is hard on the ball drive and generates a lot of heat in the blower. Replace the fluid with a good synthetic and you will pick up 1-2psi of boost. Replace the inlet and outlet pipes with 3" power pipes and you'll get more power out too. I'm still getting 6-7psi out of mine with stock pulleys even pushing through these high flowing heads (stock motor will see 7-9psi). IN my case, the FMU, timing master and blow off valve are all hooked into the back of the intake on a common line.
For timing with 92 octane I run 14 degree initial with the spout out with a boost retard set at 1.25 degrees/ pound of boost. Fuel sets at 45psi no vacuum with a stock FMU setup and 24lb injectors. Makes for a wicked torque curve. Only gripe is if I shift too slowly at 6k and floor it again it'll ping for a split second because the FMU drops pressure under vacuum. In a race situation it's fine.
Hope this helps;
Jamie
