boost surge/oscillation at wot
#1
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boost surge/oscillation at wot
i searched, found this thread: https://www.rx7club.com/showthread.p...ht=boost+surge ...
but this only shows the problem not the fix. ive noticed it since i bought the car. and i was tuned last week by BDC (great tune btw). the symptoms are: under wot in anything above 2nd gear around onset of boost (5-7psi) at near 4500 rpm i hear a woosh-woosh-woosh and the car bucks some then settles out aroun 9-10 psi and power is on strong. it seems to stop around 8 psi and is nonexhistent after that. i mostly notice it when i roll into wot in all gears. BDC thought it may be a boost or vacuum leak but we checked all ic piping. and vacuum lines. everything is fine, but i still notice it. i dont see any more than .75 bar on pfc, and i sustain 9 to just under 10 psi as per a petit boost gauge. i dont want to turn it up until i find what this is. the tune is solid, i know its not that. i see 11.1-11.3 tops at wot. anyone have any idea? it seems to me like a wastegat flutter or something causing the wastegate to open or flutter as boost increases. again, the vacuum lines are all on. my mods are:
2mm atkins seals, mild street port (around 1500k miles) greddy profect b (the good one), 1680 2nds, stock prims, aeromotive fpr, front mount, greddy type s bov, supra pump, power fc, pulleys, cltuch 9.5 lb fly wheel, 3 inch turbo back no cat exhaust, twin intake, non seq., fluidine rad, and a few others.
BDC thought it may be the bov, but i dont hear the sound it makes when opening.
but this only shows the problem not the fix. ive noticed it since i bought the car. and i was tuned last week by BDC (great tune btw). the symptoms are: under wot in anything above 2nd gear around onset of boost (5-7psi) at near 4500 rpm i hear a woosh-woosh-woosh and the car bucks some then settles out aroun 9-10 psi and power is on strong. it seems to stop around 8 psi and is nonexhistent after that. i mostly notice it when i roll into wot in all gears. BDC thought it may be a boost or vacuum leak but we checked all ic piping. and vacuum lines. everything is fine, but i still notice it. i dont see any more than .75 bar on pfc, and i sustain 9 to just under 10 psi as per a petit boost gauge. i dont want to turn it up until i find what this is. the tune is solid, i know its not that. i see 11.1-11.3 tops at wot. anyone have any idea? it seems to me like a wastegat flutter or something causing the wastegate to open or flutter as boost increases. again, the vacuum lines are all on. my mods are:
2mm atkins seals, mild street port (around 1500k miles) greddy profect b (the good one), 1680 2nds, stock prims, aeromotive fpr, front mount, greddy type s bov, supra pump, power fc, pulleys, cltuch 9.5 lb fly wheel, 3 inch turbo back no cat exhaust, twin intake, non seq., fluidine rad, and a few others.
BDC thought it may be the bov, but i dont hear the sound it makes when opening.
Last edited by rt turbo; 02-25-06 at 10:59 AM.
#2
Racecar - Formula 2000
Here's alink to how things are supposed to work.
http://robrobinette.com/boost_note.htm
It sounds to me that you feeling the normal transition from the primary to secondary at ~4500 when the transition occurs. A normal boost pattern is 10-11 psi on primary, a small dip to 9 or 9 at transition, and then 10 psi until the revs get high enough that intake and exhaust restrictions cause the boos to taper off.
http://robrobinette.com/boost_note.htm
It sounds to me that you feeling the normal transition from the primary to secondary at ~4500 when the transition occurs. A normal boost pattern is 10-11 psi on primary, a small dip to 9 or 9 at transition, and then 10 psi until the revs get high enough that intake and exhaust restrictions cause the boos to taper off.
#5
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Originally Posted by NVMYRX-7
Who is BDC and are they in the Charlotte area. Was your tune done on a dyno and how much HP did you have?
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