Why doesnt the stock turbo hold boost to redline?
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Evolving Member
Joined: Jul 2005
Posts: 147
Likes: 2
From: Australia
My original post was poorly worded: even if you have boost control (MBC, EBC, ECU - whatever) the stock turbo will still taper boost as you approach redline.
The question was directed at controlling that taper through the use of a stiffer wastegate actuator or modifying the boost control solenoid. My understanding from the previous posts is that you cannot stop the taper - its an artifact of the turbo design.
I wish I had a compressor map for the stock turbo because its not clear to me that its even worth trying to control the taper.
The question was directed at controlling that taper through the use of a stiffer wastegate actuator or modifying the boost control solenoid. My understanding from the previous posts is that you cannot stop the taper - its an artifact of the turbo design.
I wish I had a compressor map for the stock turbo because its not clear to me that its even worth trying to control the taper.
Last edited by boomtown; Nov 18, 2005 at 02:05 PM.
Originally Posted by evofool
on my car with a 9.8 hotside, my car holds 20.5 psi and tapers to 18.5 at 7500ish, with a halman boost controller and forge diverter valve
This dosen't seem to add up. So does this mean the EVOIII turbo was better then the one on the 8? I am pretty new to the EVO thing, but I have been working on dsms for 6+ years. The EVOIII 16g on my GSX is set to 19psi, and because of boost creep issues is up to about 22psi by redline and climbing.
So is this a wastegate issue? Because I can't imagine the turbo itself would fall off.
So is this a wastegate issue? Because I can't imagine the turbo itself would fall off.
Last edited by ItsFast; Nov 18, 2005 at 03:04 PM.
Originally Posted by boomtown
My original post was poorly worded: even if you have boost control (MBC, EBC, ECU - whatever) the stock turbo will still taper boost as you approach redline.
The question was directed at controlling that taper through the use of a stiffer wastegate actuator or modifying the boost control solenoid. My understanding from the previous posts is that you cannot stop the taper - its an artifact of the turbo design.
I wish I had a compressor map for the stock turbo because its not clear to me that its even worth trying to control the taper.
The question was directed at controlling that taper through the use of a stiffer wastegate actuator or modifying the boost control solenoid. My understanding from the previous posts is that you cannot stop the taper - its an artifact of the turbo design.
I wish I had a compressor map for the stock turbo because its not clear to me that its even worth trying to control the taper.
https://www.evolutionm.net/forums/sh...d.php?t=170020
Someone was saying you cannot hold boost to redline and it always tapers off no matter what and I commented mine holds boost. He asked me to videotape it to prove it and so I did. Check out my post on the 2nd page to see the vid.
I was holding WOT to 7k.
Hopefully this will clear things up - i also posted all my mods.
So, no one has answered my question yet about lower gears, like 1st or 2nd. It is reasonable to expect the stock turbo and any boost control to hold boost in 1st or 2nd to redline. I ask because those gears are the most important for autocrossing.
As far as I know, it holds for me. I know for sure from my video that 3rd, 4th and 5th hold it.
to be honest i never really shift at 7k in 1st gear. maybe 2nd.
ill test it today and let ya know.
to be honest i never really shift at 7k in 1st gear. maybe 2nd.
ill test it today and let ya know.
everyone is saying something different so i'll say it all in one post.
there are three reasons why the stock turbo tapers boost.
the first is the stock boost solenoid, not only is it a bleeder type boost controller which means the wastegate is ALWAYS slightly open, it is also controlled by the ecu which allows it to open and taper the boost off for "engine safety". linked to this phenomenon is also the the boost bills inside of the lines that connect to the stock boost solenoid which aide the solenoid is tapering boost.
this facet of boost taper can be taken care of with a manual boost controller
the second reason is the stock waste gate actuator has a pretty weak spring inside, it may not be able to stay shut even without being triggered by something as "solid" as an mbc.
the way to fix this is to get an upgraded actuator, which there has been plenty of talk about in the recent months.
the third reason the stock boost tapers and the reason that is most difficult to overcome is the stock turbo whether 10.5 or 9.8 cannot flow enough air at higher rpms and increased boost levels. this is the taper you usually see on a dyno with these cars that alreayd have actuators and mbcs, the power and the boost still fall off because the compressor side of the turbo (that's why it is regardless of 10.5 or 9.8) cannot flow that much air, so what ends up happening is that ths boost falls off because the pressure differential between the inlet and the oulet of the turbo becomes too much and this backpressure so to speak makes the boost fall off.
the way to fix this is to get a different compressor, this is why the wr 20g and evo9 compressor covers nad compressor wheels are so valuable. they maintain the wonderful spool up yet sacrafice nothing up top as far as holding boost.
there are three reasons why the stock turbo tapers boost.
the first is the stock boost solenoid, not only is it a bleeder type boost controller which means the wastegate is ALWAYS slightly open, it is also controlled by the ecu which allows it to open and taper the boost off for "engine safety". linked to this phenomenon is also the the boost bills inside of the lines that connect to the stock boost solenoid which aide the solenoid is tapering boost.
this facet of boost taper can be taken care of with a manual boost controller
the second reason is the stock waste gate actuator has a pretty weak spring inside, it may not be able to stay shut even without being triggered by something as "solid" as an mbc.
the way to fix this is to get an upgraded actuator, which there has been plenty of talk about in the recent months.
the third reason the stock boost tapers and the reason that is most difficult to overcome is the stock turbo whether 10.5 or 9.8 cannot flow enough air at higher rpms and increased boost levels. this is the taper you usually see on a dyno with these cars that alreayd have actuators and mbcs, the power and the boost still fall off because the compressor side of the turbo (that's why it is regardless of 10.5 or 9.8) cannot flow that much air, so what ends up happening is that ths boost falls off because the pressure differential between the inlet and the oulet of the turbo becomes too much and this backpressure so to speak makes the boost fall off.
the way to fix this is to get a different compressor, this is why the wr 20g and evo9 compressor covers nad compressor wheels are so valuable. they maintain the wonderful spool up yet sacrafice nothing up top as far as holding boost.
Newbie
Joined: Mar 2005
Posts: 62
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From: Dearborn
Can you explain how the Works P2 flash and "upgraded" hose fits into your explanation?
Originally Posted by trinydex
everyone is saying something different so i'll say it all in one post.
there are three reasons why the stock turbo tapers boost.
the first is the stock boost solenoid, not only is it a bleeder type boost controller which means the wastegate is ALWAYS slightly open, it is also controlled by the ecu which allows it to open and taper the boost off for "engine safety". linked to this phenomenon is also the the boost bills inside of the lines that connect to the stock boost solenoid which aide the solenoid is tapering boost.
this facet of boost taper can be taken care of with a manual boost controller
the second reason is the stock waste gate actuator has a pretty weak spring inside, it may not be able to stay shut even without being triggered by something as "solid" as an mbc.
the way to fix this is to get an upgraded actuator, which there has been plenty of talk about in the recent months.
the third reason the stock boost tapers and the reason that is most difficult to overcome is the stock turbo whether 10.5 or 9.8 cannot flow enough air at higher rpms and increased boost levels. this is the taper you usually see on a dyno with these cars that alreayd have actuators and mbcs, the power and the boost still fall off because the compressor side of the turbo (that's why it is regardless of 10.5 or 9.8) cannot flow that much air, so what ends up happening is that ths boost falls off because the pressure differential between the inlet and the oulet of the turbo becomes too much and this backpressure so to speak makes the boost fall off.
the way to fix this is to get a different compressor, this is why the wr 20g and evo9 compressor covers nad compressor wheels are so valuable. they maintain the wonderful spool up yet sacrafice nothing up top as far as holding boost.
there are three reasons why the stock turbo tapers boost.
the first is the stock boost solenoid, not only is it a bleeder type boost controller which means the wastegate is ALWAYS slightly open, it is also controlled by the ecu which allows it to open and taper the boost off for "engine safety". linked to this phenomenon is also the the boost bills inside of the lines that connect to the stock boost solenoid which aide the solenoid is tapering boost.
this facet of boost taper can be taken care of with a manual boost controller
the second reason is the stock waste gate actuator has a pretty weak spring inside, it may not be able to stay shut even without being triggered by something as "solid" as an mbc.
the way to fix this is to get an upgraded actuator, which there has been plenty of talk about in the recent months.
the third reason the stock boost tapers and the reason that is most difficult to overcome is the stock turbo whether 10.5 or 9.8 cannot flow enough air at higher rpms and increased boost levels. this is the taper you usually see on a dyno with these cars that alreayd have actuators and mbcs, the power and the boost still fall off because the compressor side of the turbo (that's why it is regardless of 10.5 or 9.8) cannot flow that much air, so what ends up happening is that ths boost falls off because the pressure differential between the inlet and the oulet of the turbo becomes too much and this backpressure so to speak makes the boost fall off.
the way to fix this is to get a different compressor, this is why the wr 20g and evo9 compressor covers nad compressor wheels are so valuable. they maintain the wonderful spool up yet sacrafice nothing up top as far as holding boost.
I guess I am one of the lucky ones, where, the old faithful hallmann holds roughly 26-27 psi all the way to 7k, drops slightly to 24, before I shift. And may I add, I am at full boost in second gear. This is with the stock wastegate, 9.8 hotside, and oh I forgot ALKYControl! I reallt do not know how long the turbo will hold up with this setup, but she's almost paid for, then comes the 42R.
Any body with a utec or similiar looking for that perrin solenoid, please take it off my hands. I have played around with thre different types of ebc and nothing compares to the hallman
Any body with a utec or similiar looking for that perrin solenoid, please take it off my hands. I have played around with thre different types of ebc and nothing compares to the hallman
Originally Posted by taumax
Can you explain how the Works P2 flash and "upgraded" hose fits into your explanation?
Originally Posted by nightwalker
how about the Works flash? It's a bit expensive, but does it hold boost all the way to redline?
Originally Posted by trinydex
flashes that retain the use of the stock solenoid attempt to fix the ecu related boost taper in a couple ways. you can eitehr delay the onset of taper indefinitely by setting the dwell time very high. there are several other ways and if you go to socalevo.net you'll see a sticky that says difference between flashes. that explains is more.
