when should I see boost?
02-01-2009, 09:32 PM
#12
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Join Date: Jul 2007
Posts: 3,731
Something definitly sounds really really wrong there. If youre not seeing boost by 4000rpms youre cars power curve is gonna be soooooooo weird so something is not right. I dont know whats wrong but i do know something is not right. What size pulley are you running and what kinda bpv/bov are you running and how strong of a spring is in there??? That could be your problem. My buddy had this problem with his turbo cobra. His bov was stuck open and thats why he wasnt making boost. When he got the bov unstuck and made sure it didnt stick open, he went from making like 8 psi to 30+psi(pegged the gauge). So check your bpv/bov springs to see if its stuck open depending on if your pulley is small enough to make some decent lbs of boost. I might even be posting some bad info but i thought think that some people run bpv/bov's on centri blowers.
If the bypass valve was stuck open, using either a vortech mini-race or a mondo-BPV, he would see neutral vacuum all the way to redline, so I'm sure it's not that.
Either way, he shouldn't have to be at WOT to see boost, that's just semi-retarded.
lightfooted driving normally is defined from about 0-10% throttle, at which point, no, he should be in full or neutral vacuum, or somewhere in-between
anything above that, and he SHOULD be in boost.
if you guys actually think lightfooted, or WOT are the only two types of driving, i'd hate to see you on the drag-strip for the first time, or hell, any time after that
02-01-2009, 09:40 PM
#14
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Join Date: Jan 2009
Location: California
Posts: 1,092
and i do fine driving to the grocery store not at WOT
and i do fine on the drag strip
You seem to know whats wrong.... just tell him already
02-01-2009, 09:43 PM
#15
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It's not going to a tuning issue, and I can tell you why. The bypass valve, if working properly, is vacuum actuated, basically, when the area past the throttle body goes into vacuum, the bypass valve opens and starts recirculating the air. That's not a perfect explination, but it will do.
Basically, bottom line, it isn't a tuning issue.
If I were to say anything, I would think that it's actually a case of the OP loosing boost through the exhaust valves. If he doesn't have just the right set of cams, I would say that's a very real possibility, or it could be that the cams might not be timed as efficiently as possible.
02-01-2009, 09:46 PM
#16
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If you think that the only two types of driving are grocery store, and WOT, I can guarantee you I could run on street tires at the strip and leave your car like it was standing still
Just so you know, do some research before you actually do decide to take that challenge. I do have my timeslips up in many places on the forums, with a very stiff suspension as well
02-01-2009, 09:51 PM
#17
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Join Date: Jan 2009
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If you think that the only two types of driving are grocery store, and WOT, I can guarantee you I could run on street tires at the strip and leave your car like it was standing still
Just so you know, do some research before you actually do decide to take that challenge. I do have my timeslips up in many places on the forums, with a very stiff suspension as well
Just so you know, do some research before you actually do decide to take that challenge. I do have my timeslips up in many places on the forums, with a very stiff suspension as well
didnt say u couldnt drive by the way....
i gotta go, the grocery store and racetrack are waiting. god if only there was a way to drive in between.
02-01-2009, 10:48 PM
#18
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Join Date: Jul 2007
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OP, sorry to take away from your thread. Argument was taken to PMs
anyway, back to your question, it all depends on what kind of driving your doing.
Essentially, the ammount of air that the blower is flowing is pretty much a constant which is based on the RPM of the engine.
So, for example, if you're running at 3000RPM, the blower is going to be pushing the same amount of air, no matter what. the only thing that changes, is the throttle blades.
The more the throttle blades are open, the more air is taken into the combustion chambers using the intake manifold. if you're seeing 8PSI at 4,000RPM, which you should be with the T-trim, which as a more agressive ramp up rate in the boost curves, at WOT, that means, that at 4,000RPM if you were to be at exactly 50% throttle, simple math says that you should be at around 4PSI.
What I think may be happening is, when you press the throttle in, you might not actually be seeing 50% when you think you are. You might be confusing the actual Throttle position by your mental image of how far your foot has traveled on the pedal.
50% throttle is actually a decent push, it's actually a good distance from the resting position of your foot, to where it is. You might really only be seeing 20-30% throttle, and be confusing how far your foot has traveled with 50%+ throttle
A good way to check this, if you have a handheld programer, is to actually plug it in and run the diagnostics/datalogging feature. You can actually view the Throttle position sensor readout right there, at the exact moment that the throttle is opened
anyway, back to your question, it all depends on what kind of driving your doing.
Essentially, the ammount of air that the blower is flowing is pretty much a constant which is based on the RPM of the engine.
So, for example, if you're running at 3000RPM, the blower is going to be pushing the same amount of air, no matter what. the only thing that changes, is the throttle blades.
The more the throttle blades are open, the more air is taken into the combustion chambers using the intake manifold. if you're seeing 8PSI at 4,000RPM, which you should be with the T-trim, which as a more agressive ramp up rate in the boost curves, at WOT, that means, that at 4,000RPM if you were to be at exactly 50% throttle, simple math says that you should be at around 4PSI.
What I think may be happening is, when you press the throttle in, you might not actually be seeing 50% when you think you are. You might be confusing the actual Throttle position by your mental image of how far your foot has traveled on the pedal.
50% throttle is actually a decent push, it's actually a good distance from the resting position of your foot, to where it is. You might really only be seeing 20-30% throttle, and be confusing how far your foot has traveled with 50%+ throttle
A good way to check this, if you have a handheld programer, is to actually plug it in and run the diagnostics/datalogging feature. You can actually view the Throttle position sensor readout right there, at the exact moment that the throttle is opened
02-01-2009, 10:55 PM
#19
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02-01-2009, 11:20 PM
#20
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Join Date: Jul 2007
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hahah, Seriously. Apparently I'm a tool because I know how to drive, yup, that makes sense
oh, and with a terminator, airflow from the blower isn't a constant based purely on engine RPM, just so everyone knows. It's also affected by Throttle blade position as well. So just by controlling the throttle position, you can control the amount of air going through the blower. Imagine that
Last edited by 2000AZ5.0GT; 02-01-2009 at 11:24 PM.