Boost Taper
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Boost Taper
Ok i am noticing this more and more as I mod the car. I am on stock IX turbo. running about 25lbs of boost. Synapse BOV HKS intake and few other bolt ons.
So at WOT I hit 25 on the boost gauge... As I hit about 5200 rpms the boost will taper off. It will go down to about 19 or so. IDK if the turbo is just falling flat by design or I have a boost issue. I have this issue on the Stock DV and with the Synapse so tried different DV's
My AFRs are solid so I am not sure if this is just normal and I am just noticing it more or its an issue..
Any thoughts?
So at WOT I hit 25 on the boost gauge... As I hit about 5200 rpms the boost will taper off. It will go down to about 19 or so. IDK if the turbo is just falling flat by design or I have a boost issue. I have this issue on the Stock DV and with the Synapse so tried different DV's
My AFRs are solid so I am not sure if this is just normal and I am just noticing it more or its an issue..
Any thoughts?
Last edited by thedru13; Dec 10, 2011 at 03:15 PM.
how are you observing the taper? Is it from watching the boost gauge while you drive or do you have a MAP sensor you're logging? with the stock IX turbo and hallman MBC I was seeing about 20-21psi @ 7k on my VIII.. this was a 24# spike and recorded via EVOScan using a JDM 3bar.
You aren't too far off from that. first thing I would do is give the car a boost leak test. that usually tells the story of where to look next...
You aren't too far off from that. first thing I would do is give the car a boost leak test. that usually tells the story of where to look next...
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Did a boost leak test and didn't find any. changed all vacuum hoses and checked clamps ect. I have all new couplers and tbolt clamps.
As far as the boost falling off I am seeing it on my boost gauge.
I have tried 2 different UICP's and 2 different intakes same result. The only thing I could think of is that my TB seals are leaking but its not that old. I checked when I did a boost leak check and didn't see much of anything.
UGH
As far as the boost falling off I am seeing it on my boost gauge.
I have tried 2 different UICP's and 2 different intakes same result. The only thing I could think of is that my TB seals are leaking but its not that old. I checked when I did a boost leak check and didn't see much of anything.
UGH
how are you observing the taper? Is it from watching the boost gauge while you drive or do you have a MAP sensor you're logging? with the stock IX turbo and hallman MBC I was seeing about 20-21psi @ 7k on my VIII.. this was a 24# spike and recorded via EVOScan using a JDM 3bar.
You aren't too far off from that. first thing I would do is give the car a boost leak test. that usually tells the story of where to look next...
You aren't too far off from that. first thing I would do is give the car a boost leak test. that usually tells the story of where to look next...
Did a boost leak test and didn't find any. changed all vacuum hoses and checked clamps ect. I have all new couplers and tbolt clamps.
As far as the boost falling off I am seeing it on my boost gauge.
I have tried 2 different UICP's and 2 different intakes same result. The only thing I could think of is that my TB seals are leaking but its not that old. I checked when I did a boost leak check and didn't see much of anything.
UGH
As far as the boost falling off I am seeing it on my boost gauge.
I have tried 2 different UICP's and 2 different intakes same result. The only thing I could think of is that my TB seals are leaking but its not that old. I checked when I did a boost leak check and didn't see much of anything.
UGH
if your TB seals were leaking a boosk leak test would show that. how high did you pressurize the system too? how long did it take for you to lose pressure? also, why did you change all your vac lines and hose clamps if there were no leaks?
honestly, I wouldn't rely on your eyes and a mechanical boost gauge to tell you whether or not you have taper. you really need to log a map sensor and compare those readings to your RPM.
Boost taper is a normal thing with the stock turbo. it just doesn't (efficiently) produce the CFM needed to pressurize the cylinders @ 7k RPM, like it can @ 3.5k RPM. the HP/TQ numbers in your sig look good, what makes you think you are leaving power on the table?
honestly, I wouldn't rely on your eyes and a mechanical boost gauge to tell you whether or not you have taper. you really need to log a map sensor and compare those readings to your RPM.
Boost taper is a normal thing with the stock turbo. it just doesn't (efficiently) produce the CFM needed to pressurize the cylinders @ 7k RPM, like it can @ 3.5k RPM. the HP/TQ numbers in your sig look good, what makes you think you are leaving power on the table?
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Yes Stock O2 Housing
I want to get the car back on the Dyno and tweak my tune. Its been really hard to road tune my car since I have moved. What your saying makes sense. I changed out the vac lines just to rule out any potential source of issues. I got my boost up to 24 and it held.. I didn't hear any leaking.. Only a bit of air coming from where the MBC was since I didn't get that to seal 100%.
I just feel that the car is responding different. I guess I got used to the stock UICP. Odd i guess. After I changed to all hard piping my boost reacts different. For example on the highway with my stock UICP i would hit 27 on the boost gauge Now with the hard pipe I hit 25 and hit 25 each time. This is in higher gears before it used to crawl up even would hit 29 sometimes. I always thought it was the stock couplers expanding.
With my set up now just feels like i loose my boost a bit quicker than before.
So why i am posted just to see if this is normal or I should be looking for something. I will log the car and see what I can find.
Thanks for the info.. Much appreciated.
if your TB seals were leaking a boosk leak test would show that. how high did you pressurize the system too? how long did it take for you to lose pressure? also, why did you change all your vac lines and hose clamps if there were no leaks?
honestly, I wouldn't rely on your eyes and a mechanical boost gauge to tell you whether or not you have taper. you really need to log a map sensor and compare those readings to your RPM.
Boost taper is a normal thing with the stock turbo. it just doesn't (efficiently) produce the CFM needed to pressurize the cylinders @ 7k RPM, like it can @ 3.5k RPM. the HP/TQ numbers in your sig look good, what makes you think you are leaving power on the table?
honestly, I wouldn't rely on your eyes and a mechanical boost gauge to tell you whether or not you have taper. you really need to log a map sensor and compare those readings to your RPM.
Boost taper is a normal thing with the stock turbo. it just doesn't (efficiently) produce the CFM needed to pressurize the cylinders @ 7k RPM, like it can @ 3.5k RPM. the HP/TQ numbers in your sig look good, what makes you think you are leaving power on the table?
I want to get the car back on the Dyno and tweak my tune. Its been really hard to road tune my car since I have moved. What your saying makes sense. I changed out the vac lines just to rule out any potential source of issues. I got my boost up to 24 and it held.. I didn't hear any leaking.. Only a bit of air coming from where the MBC was since I didn't get that to seal 100%.
I just feel that the car is responding different. I guess I got used to the stock UICP. Odd i guess. After I changed to all hard piping my boost reacts different. For example on the highway with my stock UICP i would hit 27 on the boost gauge Now with the hard pipe I hit 25 and hit 25 each time. This is in higher gears before it used to crawl up even would hit 29 sometimes. I always thought it was the stock couplers expanding.
With my set up now just feels like i loose my boost a bit quicker than before.
So why i am posted just to see if this is normal or I should be looking for something. I will log the car and see what I can find.
Thanks for the info.. Much appreciated.
the air leaking out of the MBC is normal. Thats how an MBC works, by tricking the WG into thinking there is less pressure on the diaphram of the WG than there really is. you need to crank the MBC down 3-4 turns when you boost leak test so it won't bleed the air off (just remember to put it back to where it was prior to doing the test otherwise you'll be running A LOT of boost). Unless you're talking about hearing the MBC leaking air when you're driving on the road, in which case you must have super hero type hearing, lol.
boost pressure is just a measure of resistance. a higher number doesn't always = more power. if your car is making less boost but the power is the same that is a very good thing. it means your setup is running more efficient and it needs less air (and fuel) to make the same power.
if you are still on the stock o2 housing, IMO, you are leaving power on the table, especially with a full exhaust behind it. If you are looking for more power I would change that out and see what happens. My guess is you will need even less boost to make the same amount of power you're making now.
boost pressure is just a measure of resistance. a higher number doesn't always = more power. if your car is making less boost but the power is the same that is a very good thing. it means your setup is running more efficient and it needs less air (and fuel) to make the same power.
if you are still on the stock o2 housing, IMO, you are leaving power on the table, especially with a full exhaust behind it. If you are looking for more power I would change that out and see what happens. My guess is you will need even less boost to make the same amount of power you're making now.
Thread Starter
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iTrader: (24)
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From: West Chester PA
the air leaking out of the MBC is normal. Thats how an MBC works, by tricking the WG into thinking there is less pressure on the diaphram of the WG than there really is. you need to crank the MBC down 3-4 turns when you boost leak test so it won't bleed the air off (just remember to put it back to where it was prior to doing the test otherwise you'll be running A LOT of boost). Unless you're talking about hearing the MBC leaking air when you're driving on the road, in which case you must have super hero type hearing, lol.
boost pressure is just a measure of resistance. a higher number doesn't always = more power. if your car is making less boost but the power is the same that is a very good thing. it means your setup is running more efficient and it needs less air (and fuel) to make the same power.
if you are still on the stock o2 housing, IMO, you are leaving power on the table, especially with a full exhaust behind it. If you are looking for more power I would change that out and see what happens. My guess is you will need even less boost to make the same amount of power you're making now.
boost pressure is just a measure of resistance. a higher number doesn't always = more power. if your car is making less boost but the power is the same that is a very good thing. it means your setup is running more efficient and it needs less air (and fuel) to make the same power.
if you are still on the stock o2 housing, IMO, you are leaving power on the table, especially with a full exhaust behind it. If you are looking for more power I would change that out and see what happens. My guess is you will need even less boost to make the same amount of power you're making now.
Great post... You explained that really well. Thanks.... What you are saying makes total sense. I have toyed around with changing the stock 02 out.. I may port mine or buy a ported one. I am thinking of going with a different turbo so not sure what 02 to go with so thats why I have hesitated. Also I am light in the wallet at the moment.
Again really appreciate your help..
