boost ranges from 21-24 psi randomly?
boost ranges from 21-24 psi randomly?
like the thread says... sometimes I'll hit 24 psi on my gauge and sometimes I'll hit 21 psi...
I had set my buschur MBC to 21 psi using the eyeball the gauge method... I had a map sensor but had to sell it + I couldnt get the original map sensor off
Could the gauge just be reading differently? It still reads the same at vacuum... just now boosting 24 psi instead of 21 psi... and the car DOES feel a little faster lately too (couldn't have been a placebo either because the car felt faster BEFORE I noticed the 24 psi)
Sorry if the thread is confusing. BASICALLY :
MY GAUGE WAS READING 21 PSI LAST WEEK NOW IT'S READING 24 PSI.
I doubt anybody tinkered with my mbc, it's the buschur one and it only moves if the vacuum lines move... maybe the vacuum lines randomly moved while I was driving? Idk im lost ;( I didn't even know evo's could run 24 psi on the stock turbo on 91 octane
btw if it helps : I have a buschur MBC, crushed IX DV, and depo electronic boost gauge (pretty accurate from what I've heard)
I had set my buschur MBC to 21 psi using the eyeball the gauge method... I had a map sensor but had to sell it + I couldnt get the original map sensor off
Could the gauge just be reading differently? It still reads the same at vacuum... just now boosting 24 psi instead of 21 psi... and the car DOES feel a little faster lately too (couldn't have been a placebo either because the car felt faster BEFORE I noticed the 24 psi)
Sorry if the thread is confusing. BASICALLY :
MY GAUGE WAS READING 21 PSI LAST WEEK NOW IT'S READING 24 PSI.
I doubt anybody tinkered with my mbc, it's the buschur one and it only moves if the vacuum lines move... maybe the vacuum lines randomly moved while I was driving? Idk im lost ;( I didn't even know evo's could run 24 psi on the stock turbo on 91 octane
btw if it helps : I have a buschur MBC, crushed IX DV, and depo electronic boost gauge (pretty accurate from what I've heard)
Temperature has pretty much been the same... but I guess it could be a waste gate issue. As long as I'm not noticing any actual problems I should be fine though, right?
If you have a tactrix cable or know someone that does, it would be a good idea to log some WOT pulls just to make sure you're not getting any knock, but other than that you should be fine.
What gear(s) were you testing boost in? As someone else mentioned ambient air temps can impact on boost levels. If before you were originally set for running 21# in the summer heat and all of a sudden air temps cooled off. Or let's say you changed to testing the boost at night when air temps are cooler instead of during the daytime when air temps are usually higher.
You should always set and test boost under repeatable conditions: on the same stretch of road and at the same time of day, under similar weather conditions and in the same gear to get a fairly objective result.
You should always set and test boost under repeatable conditions: on the same stretch of road and at the same time of day, under similar weather conditions and in the same gear to get a fairly objective result.
Last edited by sparky; Aug 7, 2011 at 12:06 PM.
3rd gear same weather, no knock. I get 1 count of knock once in a while, I'm on 91 octane VD last night on a straightaway 3rd gear came out as 308whp and 290torque this is at the 23ish psi... again I have no knock. Or VERYYY little... ill post up pictures of my log/map/vd when I get home
Funny you should mention the wastegate. Since you are using an MBC then I'll let you in on something: Boost will tend to vary more on a car that has relatively low wastegate spring pressure as opposed to one that has more wastegate spring pressure(preload).
I suspect that maybe your turbo may be set up with relatively low wastegate spring pressure....maybe around 14#. So, from 14-21# you are controlling boost just with the MBC.
Also, if the turbo is creeping 2-3# then you might want to port the entrance to the wastegate bypass port in the turbine housing. Or, if you are running an aftermarket O2 housing you can try porting the crossover hole in the exit chamber divider wall.
Are you running catless, or not?
I suspect that maybe your turbo may be set up with relatively low wastegate spring pressure....maybe around 14#. So, from 14-21# you are controlling boost just with the MBC.
Also, if the turbo is creeping 2-3# then you might want to port the entrance to the wastegate bypass port in the turbine housing. Or, if you are running an aftermarket O2 housing you can try porting the crossover hole in the exit chamber divider wall.
Are you running catless, or not?
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3rd gear same weather, no knock. I get 1 count of knock once in a while, I'm on 91 octane VD last night on a straightaway 3rd gear came out as 308whp and 290torque this is at the 23ish psi... again I have no knock. Or VERYYY little... ill post up pictures of my log/map/vd when I get home
Also, if the evening temps are cooling off more now than when you last set the boost, this may be the cause. I was out in Chico last month and it was hot as heck. If you were to compare boost set during early July in central CA to boost set now when there is some denser, cooler evening air the setting would be way off and you'd have to readjust the knob.
Last edited by sparky; Aug 7, 2011 at 12:28 PM.
Shoulda just went with the hallman in cabin instead of buschur if I knew id be readjusting so much! Hahaha... anyway, sounds like its boost creep then ya? I'm catless on stock o2 housing
To me it sounds like the ambient air temp swings between now and the last time you set boost, or had the car tuned, are affecting your peak readings. You haven't changed or modded anything significant on your car during the interim, have you?
IMO, for it to be a genuine case of boost creep you would have had to have made a change in hardware or tune that would cause creep. Sure, your setup may be on the edge and prone to creeping, but this is good. It means that you have a good tune and that the weather can affect it one way or the other.
So you just have to keep a watchful eye on your boost gauge and turn it down a notch in the winter and conversely you'll have to crank it up a wee bit again in the summer months. As you say, you might have been better off with the Hallman in car kit. Ha Ha
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Look, The Sacramento Valley is strange weatherwise in that it can be extremely hot and arid with little moisture in the air during the day. But, at night it can cool off 20 to 30 degrees and the moisture content of the air increases due to the Tule fog. So, it is natural for the boost level on a turbocharged car to increase w/o touching the controller knob under those conditions.
I had a similar situation when I lived in the Diablo Valley, in Contra Costa County. During the day it would be dry and the air temps were up in the hundreds, but at night the temps would drop and the fog would roll in off the Bay.
So, I had a daytime setting on the boost knob which was 2-3 PSI higher than the night time setting. During the day I would set the knob at 17 PSI and at night I had to turn it back down a half a turn to keep it at 17#.
It might be easier to get a 3-port BCS, and a JDM map sensor, etc. and let Bryan tune your car with ECU controlled boost. I think that setup is self compensating and will keep boost level dead nuts, regardless of ambient air temp changes, if I am not mistaken.
IMO, for it to be a genuine case of boost creep you would have had to have made a change in hardware or tune that would cause creep. Sure, your setup may be on the edge and prone to creeping, but this is good. It means that you have a good tune and that the weather can affect it one way or the other.
So you just have to keep a watchful eye on your boost gauge and turn it down a notch in the winter and conversely you'll have to crank it up a wee bit again in the summer months. As you say, you might have been better off with the Hallman in car kit. Ha Ha
.Look, The Sacramento Valley is strange weatherwise in that it can be extremely hot and arid with little moisture in the air during the day. But, at night it can cool off 20 to 30 degrees and the moisture content of the air increases due to the Tule fog. So, it is natural for the boost level on a turbocharged car to increase w/o touching the controller knob under those conditions.
I had a similar situation when I lived in the Diablo Valley, in Contra Costa County. During the day it would be dry and the air temps were up in the hundreds, but at night the temps would drop and the fog would roll in off the Bay.
So, I had a daytime setting on the boost knob which was 2-3 PSI higher than the night time setting. During the day I would set the knob at 17 PSI and at night I had to turn it back down a half a turn to keep it at 17#.
It might be easier to get a 3-port BCS, and a JDM map sensor, etc. and let Bryan tune your car with ECU controlled boost. I think that setup is self compensating and will keep boost level dead nuts, regardless of ambient air temp changes, if I am not mistaken.
Last edited by sparky; Aug 7, 2011 at 07:43 PM.
To me it sounds like the ambient air temp swings between now and the last time you set boost, or had the car tuned, are affecting your peak readings. You haven't changed or modded anything significant on your car during the interim, have you?
IMO, for it to be a genuine case of boost creep you would have had to have made a change in hardware or tune that would cause creep. Sure, your setup may be on the edge and prone to creeping, but this is good. It means that you have a good tune and that the weather can affect it one way or the other.
So you just have to keep a watchful eye on your boost gauge and turn it down a notch in the winter and conversely you'll have to crank it up a wee bit again in the summer months. As you say, you might have been better off with the Hallman in car kit. Ha Ha.
Look, The Sacramento Valley is strange weatherwise in that it can be extremely hot and arid with little moisture in the air during the day. But, at night it can cool off 20 to 30 degrees and the moisture content of the air increases due to the Tule fog. So, it is natural for the boost level on a turbocharged car to increase w/o touching the controller knob under those conditions.
I had a similar situation when I lived in the Diablo Valley, in Contra Costa County. During the day it would be dry and the air temps were up in the hundreds, but at night the temps would drop and the fog would roll in off the Bay.
So, I had a daytime setting on the boost knob which was 2-3 PSI higher than the night time setting. During the day I would set the knob at 17 PSI and at night I had to turn it back down a half a turn to keep it at 17#.
It might be easier to get a 3-port BCS, and a JDM map sensor, etc. and let Bryan tune your car with ECU controlled boost. I think that setup is self compensating and will keep boost level dead nuts, regardless of ambient air temp changes, if I am not mistaken.
IMO, for it to be a genuine case of boost creep you would have had to have made a change in hardware or tune that would cause creep. Sure, your setup may be on the edge and prone to creeping, but this is good. It means that you have a good tune and that the weather can affect it one way or the other.
So you just have to keep a watchful eye on your boost gauge and turn it down a notch in the winter and conversely you'll have to crank it up a wee bit again in the summer months. As you say, you might have been better off with the Hallman in car kit. Ha Ha
.Look, The Sacramento Valley is strange weatherwise in that it can be extremely hot and arid with little moisture in the air during the day. But, at night it can cool off 20 to 30 degrees and the moisture content of the air increases due to the Tule fog. So, it is natural for the boost level on a turbocharged car to increase w/o touching the controller knob under those conditions.
I had a similar situation when I lived in the Diablo Valley, in Contra Costa County. During the day it would be dry and the air temps were up in the hundreds, but at night the temps would drop and the fog would roll in off the Bay.
So, I had a daytime setting on the boost knob which was 2-3 PSI higher than the night time setting. During the day I would set the knob at 17 PSI and at night I had to turn it back down a half a turn to keep it at 17#.
It might be easier to get a 3-port BCS, and a JDM map sensor, etc. and let Bryan tune your car with ECU controlled boost. I think that setup is self compensating and will keep boost level dead nuts, regardless of ambient air temp changes, if I am not mistaken.
Well I did an uphill pull in 4th gear today around 5 pm (about 90 degree weather) and the boost gauge hit 21 psi around 3.5k rpm and rose to 23ish around 5k then started to taper back down.
I'm not experiencing any actual problems so far... I had an omni 4 bar but I sold it... maybe I'll make the switch to ecu boost and/or speed density in the future
Have you tried just turning the knob of your MBC back out a half turn? I would just be curious to know how it reacts. Do you think that it'll hit 19ish and creep up a pound or two to 21#? Just curious.
I just now reread your original post and I just don't quite understand what you mean by, "...it only moves if the vacuum lines move...". Could you clarify this statement for me please?
Two PSI of creep going uphill in 4th isn't bad and I wouldn't worry about it myself. You said that knock readings are minimal, right? No knock in 90* weather at 23 PSI on 91 octane means your tune is safe. If it was me I might just turn the MBC knob back out a half turn....just to play it safe.
Two PSI of creep under the circumstances isn't too bad. I might be tempted to pop the turbine housing off and port the entrance to the wastegate bypass port. I'd be willing to bet that this would elimimate the 2#'s of creep.
Two PSI of creep under the circumstances isn't too bad. I might be tempted to pop the turbine housing off and port the entrance to the wastegate bypass port. I'd be willing to bet that this would elimimate the 2#'s of creep.
What I meant was that the way that the buschur manual boost controller works; it only allows boost to be changed if the vacuum hoses are unplugged.
I'll probably turn the MBC back a little bit. My boost was set to 21 psi and it's usually there but I do get the occasional 2-3# of creep in the 5k rpm range. So far it seems safe-no knock.
I'll probably turn the MBC back a little bit. My boost was set to 21 psi and it's usually there but I do get the occasional 2-3# of creep in the 5k rpm range. So far it seems safe-no knock.