No overboost cut-out ?
30 September 1999, 11:26 AM
#1
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Fitted a bleed valve today to up the boost a tad (I hear cries of Oh No Fool !) and yes I am aware of the possibilities !
I first fitted it between the Inlet and MAP sensor to "fool" the ECU into thinking it was seeing less boost, thus raising boost. I also thought this would get round the ECU overboost cut-out feature. Didnt work at all, but created loadsa lag and slightly less boost. My conclusion is that the ECU relies more on rpm/load than pressure seen to control the wastegate.
Then used the "traditional" method of putting it between the turbo and wastegate actuator. This works, such that after tweaking I had peak 20psi, holding 18psi. After a sensible thought I've now got it where boost peaks at 18psi and holds at 16.
Q. Why doesnt the ECU cut the fuel supply ? All the wizards seem to think 16psi would be the threshold. But 20peak and 18 held ? Surely that would put the ECU into a panic ?
Perhaps the lack of action from my first attempt and the lack of cut-out means my pressure sensor isnt working ? Would there be any dire affects from this ?
Appreciate any help.
I first fitted it between the Inlet and MAP sensor to "fool" the ECU into thinking it was seeing less boost, thus raising boost. I also thought this would get round the ECU overboost cut-out feature. Didnt work at all, but created loadsa lag and slightly less boost. My conclusion is that the ECU relies more on rpm/load than pressure seen to control the wastegate.
Then used the "traditional" method of putting it between the turbo and wastegate actuator. This works, such that after tweaking I had peak 20psi, holding 18psi. After a sensible thought I've now got it where boost peaks at 18psi and holds at 16.
Q. Why doesnt the ECU cut the fuel supply ? All the wizards seem to think 16psi would be the threshold. But 20peak and 18 held ? Surely that would put the ECU into a panic ?
Perhaps the lack of action from my first attempt and the lack of cut-out means my pressure sensor isnt working ? Would there be any dire affects from this ?
Appreciate any help.
30 September 1999, 11:41 AM
#2
Ecu Specialist
Boost cut is at approx 4.0 v map sensor output, the ecu will allow transients above that but the length of time may vary car to car. The 4 v value should equate to about 16 psi on a UK car. There will be tolerances to take into account.
Check the map out put using a digital voltmeter and accurate boost guage (accuracy is important, most guages are out by at least 1.5 psi). I ran the cables into the car and perched the meter somwhere to do this. I can send you an Excel spreadsheet showing the output of various sensors against pressure if you like ... it may help.
Bob
[This message has been edited by Bob Rawle (edited 30-09-1999).]
Check the map out put using a digital voltmeter and accurate boost guage (accuracy is important, most guages are out by at least 1.5 psi). I ran the cables into the car and perched the meter somwhere to do this. I can send you an Excel spreadsheet showing the output of various sensors against pressure if you like ... it may help.
Bob
[This message has been edited by Bob Rawle (edited 30-09-1999).]
30 September 1999, 06:35 PM
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Thanks for that, I'll have a looksie this weekend.
Where do you think the best place to put the bleed valve ? Immediately before the actuator, in the hose to the wastegate solenoid or immediately after the air exits from the turbo/intercooler ?
Each has their pros/cons but I'm guessing it doesnt really matter !
Where do you think the best place to put the bleed valve ? Immediately before the actuator, in the hose to the wastegate solenoid or immediately after the air exits from the turbo/intercooler ?
Each has their pros/cons but I'm guessing it doesnt really matter !
30 September 1999, 07:07 PM
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Lee,
I have also fitted a bleed valve between the turbo outlet and wastegate actuator.
I also received a second bleed valve for reducing the pressure to the MAP sensor (which has not been fitted).
The boost was initially at 12psi and I have gradually reduced the pressure after fitting until showing an indicated 14psi.
When setting the valve, my boost guage was just creeping over 15psi and the engine cuts for approximately one second. The MAP sensor therefore seems to be working.
Anyhow, getting to the point - in the Turbosmart instructions, the tubing between the turbo and wastegate is replaced and the two hoses removed are connected together (using a 5mm connector). Is this making any difference ? (I know that in theory it shouldn't).
I also notice that air temperature has a big effect on boost levels obtained - I initially fitted the bleed valve during our "summer" period and have had to reduce the boost level twice since - to avoid the MAP sensor triggering.
Looking at the "Training WRX" book, it states some values which may be of interest (standard aussie WRX a.k.a. UK Turbo)...
Max boost (95 RON) 1.0 - 1.1 bar
Max boost (98/99 RON) 1.4 bar
Fuelling system 1.2 bar max.
I'm sure I have read somewhere the standard MAP sensor is inaccurate above 15psi - but
Reading between the lines, 1.2bar would be the safe limit with a car running SUL without chipping/remap. This equates to 17.6psi.
I am however fairly cautious and would not increase the boost on my car above 16psi.
I am still learning about this issue so if anyone has any pearls of wisdom, I would be interested.
Thanks
Gavin
I have also fitted a bleed valve between the turbo outlet and wastegate actuator.
I also received a second bleed valve for reducing the pressure to the MAP sensor (which has not been fitted).
The boost was initially at 12psi and I have gradually reduced the pressure after fitting until showing an indicated 14psi.
When setting the valve, my boost guage was just creeping over 15psi and the engine cuts for approximately one second. The MAP sensor therefore seems to be working.
Anyhow, getting to the point - in the Turbosmart instructions, the tubing between the turbo and wastegate is replaced and the two hoses removed are connected together (using a 5mm connector). Is this making any difference ? (I know that in theory it shouldn't).
I also notice that air temperature has a big effect on boost levels obtained - I initially fitted the bleed valve during our "summer" period and have had to reduce the boost level twice since - to avoid the MAP sensor triggering.
Looking at the "Training WRX" book, it states some values which may be of interest (standard aussie WRX a.k.a. UK Turbo)...
Max boost (95 RON) 1.0 - 1.1 bar
Max boost (98/99 RON) 1.4 bar
Fuelling system 1.2 bar max.
I'm sure I have read somewhere the standard MAP sensor is inaccurate above 15psi - but
Reading between the lines, 1.2bar would be the safe limit with a car running SUL without chipping/remap. This equates to 17.6psi.
I am however fairly cautious and would not increase the boost on my car above 16psi.
I am still learning about this issue so if anyone has any pearls of wisdom, I would be interested.
Thanks
Gavin
30 September 1999, 08:30 PM
#5
Ecu Specialist
When I fit a bleed valve for any reason I always fit it between the amal valve and the actuator. (my car has a three way amal valve.) On a two way valve I would fit between the tee piece and actuator but it will work just as well in any of the pipes.
Map sensor gets a bit non-linear above about 16 psi. (4v output) although an STi IV map is linear up to 20 psi or so.
Max boost per car is dependant on fuel grade, timimg, fueling, air density, temperature etc etc. in other words its dangerous to generalise. They all tend to be a bit different car to car.
Bob
Map sensor gets a bit non-linear above about 16 psi. (4v output) although an STi IV map is linear up to 20 psi or so.
Max boost per car is dependant on fuel grade, timimg, fueling, air density, temperature etc etc. in other words its dangerous to generalise. They all tend to be a bit different car to car.
Bob
30 September 1999, 09:02 PM
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GavinP
You seem to be talking as you got your bleed valve as part of a kit! is there such a thing without the need for a chip which as far as i know, works excatly the same but with a evc to block the cutoff by the map sensor?
where can i get a bleed valve? anyone
cheers
sam
You seem to be talking as you got your bleed valve as part of a kit! is there such a thing without the need for a chip which as far as i know, works excatly the same but with a evc to block the cutoff by the map sensor?
where can i get a bleed valve? anyone
cheers
sam
30 September 1999, 09:45 PM
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G'day...
Bleed valves are available from everywhere... any tuning company...
The Turbosmart kit is an Oz kit, that allows you to alter the boost level of your car.. I believe it's quite cheap.
J.
Bleed valves are available from everywhere... any tuning company...
The Turbosmart kit is an Oz kit, that allows you to alter the boost level of your car.. I believe it's quite cheap.
J.
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01 October 1999, 12:12 AM
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Yep agree fully.
However, house purchase and marriage all mean that my spending money is curbed by my finance director (wife).
So I'm looking for cheap DIY mods.
We all know that an electronic boost controller would be a better buy, although at £325 (Blitz DSBC) its considerably more than a £20 bleed valve. And it can only control boost ! So you then need options to adjust fuelling/ignition etc to get the full benefit.
Instead of adding all these "kits" over the place I would go for the PE remap for £700. This works out slightly cheaper and does the whole job in one go !
However, house purchase and marriage all mean that my spending money is curbed by my finance director (wife).
So I'm looking for cheap DIY mods.
We all know that an electronic boost controller would be a better buy, although at £325 (Blitz DSBC) its considerably more than a £20 bleed valve. And it can only control boost ! So you then need options to adjust fuelling/ignition etc to get the full benefit.
Instead of adding all these "kits" over the place I would go for the PE remap for £700. This works out slightly cheaper and does the whole job in one go !
01 October 1999, 06:52 AM
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I also ordered the Turbosmart kit Type 1. Unfortuntely, after 2 hrs trial, my engine seems to be running very rough and I quickly reverted to standard.
I drive a STI 5 Type R and I increased the boost from standard 1.1bar to 1.3 bar in 3rd. However, I found that in 5th, I seem to overboost to about 1.5 and sometimes more.
Anyone has ideas if this is a safe interim upgrade before a full STI 5 ECU is available. I called Link NZ and they are still working on the MAPs for a STI5.
Lastly, where do we insert this kit? I was told to remove the T-piece and valve to solonoid and directly join the actuator and turbo with the bleed tap in between. Should I leave the t-piece intact, as this is for the engine to control boost.
I drive a STI 5 Type R and I increased the boost from standard 1.1bar to 1.3 bar in 3rd. However, I found that in 5th, I seem to overboost to about 1.5 and sometimes more.
Anyone has ideas if this is a safe interim upgrade before a full STI 5 ECU is available. I called Link NZ and they are still working on the MAPs for a STI5.
Lastly, where do we insert this kit? I was told to remove the T-piece and valve to solonoid and directly join the actuator and turbo with the bleed tap in between. Should I leave the t-piece intact, as this is for the engine to control boost.
01 October 1999, 08:41 AM
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AArrgghhh...
Didnt allow for the fact that boost would be higher in 5th gear !
Cruising along a nice stretch and decided to boot it (rude not to really)..
18psi held for 3 seconds then a god-almighty wrenching as the cut-out kicks in.
I've now reduced the bleed to avoid this in 5th, but now I am running less boost in lower gears.
So the MAP is working then
As to where to fit it etc..You still need the wastegate solenoid in the system so the ECU retains some control.
For ease I fitted the bleed valve in the hose going to the solenoid. I may move it to between the T-piece and actuator (as Bob's sugg) to see if there is any difference.
Since I have not (and cannot) alter the fuelling I am going to stick with the boost just under the cut-out levels..if I put another bleed valve in to sort the MAP sensor I am worried I'll overdo it.
Maybe after a trial at a rollingroad session I'll change my mind but for now I'm happy with 18peak 16held.
Didnt allow for the fact that boost would be higher in 5th gear !
Cruising along a nice stretch and decided to boot it (rude not to really)..
18psi held for 3 seconds then a god-almighty wrenching as the cut-out kicks in.
I've now reduced the bleed to avoid this in 5th, but now I am running less boost in lower gears.
So the MAP is working then
As to where to fit it etc..You still need the wastegate solenoid in the system so the ECU retains some control.
For ease I fitted the bleed valve in the hose going to the solenoid. I may move it to between the T-piece and actuator (as Bob's sugg) to see if there is any difference.
Since I have not (and cannot) alter the fuelling I am going to stick with the boost just under the cut-out levels..if I put another bleed valve in to sort the MAP sensor I am worried I'll overdo it.
Maybe after a trial at a rollingroad session I'll change my mind but for now I'm happy with 18peak 16held.
01 October 1999, 10:35 AM
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If you want consistent boost in each gear, an electronic boost controller is the better way to go. Other advantages are that boost builds quicker, there are no boost spikes, and the set boost can sustained all the way up the rev range. I think the newer electronic boost controllers also adjust boost settings for different barometric conditions.
01 October 1999, 03:05 PM
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Right then..had a good play moving the bleed valve about..
(i) Between the T-piece and the actuator. Not a good idea..
Boost shot up to 25psi before my eyes popped out..
Had to have the valve practically closed in order to stop the monumental overboost. Still wasn't satisfactory..upon booting it psi goes to 20, drops to 10 then rises to 13 where it stays. It is quite amusing though, being shoved then slowing then accelerating again.
I think what happens is...boost builds up quickly, ECU closes solenoid but bleed valve causes boost to rise further..after a second the pressure drops dramatically, ECU opens valve again and finally they stabilise at standard running boost (13psi)
(ii) Immediately after the outlet from turbo.
Same as above although smoother, I guess this is the restrictor smoothing it out. Still ends up running standard boost eventually.
(iii) In the hose to the solenoid. I think for a MY99 this is best. The valve has to be opened quite a lot, but the end result is very good :-
a) Boost rises quickly.
b) Peak is a generous 18psi.
c) The car holds a decent 16psi without fluctuation.
d) Nice n smooth.
Really, for a MY99 this is the only place worthwhile. Otherwise you end up with massive overboost and standard held boost which isnt very good.
Incidentally, I've picked up a rather weird blow-off sound when changing gear..must be because the system is now a little "open"
cheers all for the input. I'm now a happy man.
[This message has been edited by Lee (edited 01-10-1999).]
(i) Between the T-piece and the actuator. Not a good idea..
Boost shot up to 25psi before my eyes popped out..
Had to have the valve practically closed in order to stop the monumental overboost. Still wasn't satisfactory..upon booting it psi goes to 20, drops to 10 then rises to 13 where it stays. It is quite amusing though, being shoved then slowing then accelerating again.
I think what happens is...boost builds up quickly, ECU closes solenoid but bleed valve causes boost to rise further..after a second the pressure drops dramatically, ECU opens valve again and finally they stabilise at standard running boost (13psi)
(ii) Immediately after the outlet from turbo.
Same as above although smoother, I guess this is the restrictor smoothing it out. Still ends up running standard boost eventually.
(iii) In the hose to the solenoid. I think for a MY99 this is best. The valve has to be opened quite a lot, but the end result is very good :-
a) Boost rises quickly.
b) Peak is a generous 18psi.
c) The car holds a decent 16psi without fluctuation.
d) Nice n smooth.
Really, for a MY99 this is the only place worthwhile. Otherwise you end up with massive overboost and standard held boost which isnt very good.
Incidentally, I've picked up a rather weird blow-off sound when changing gear..must be because the system is now a little "open"
cheers all for the input. I'm now a happy man.
[This message has been edited by Lee (edited 01-10-1999).]
01 October 1999, 07:42 PM
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This issue seems to have generated some interest...and I must give Bob his due - generalisation is a bad thing and I understand that STi variants have different tolerances and other factors are involved - he also knows a lot more about this subject than I do !
But, I quoted the MRT book as it gives one opinion on the limits of various engine components. In context, I was trying to make the point that over 1.2bar is a very bad idea on a standard car - which was happening on Lee's car.
--------------------------------------------
Anyhow, I have a couple of further questions which hopefully can be answered:
1. Is there a cost-effective way of doing this (i.e. cheaper than PE remap, less crude than a bleed valve) ?
2. This is directed to Bob (if possible), how is the best way to go about learning more about this subject - have any books been published and how did you learn ?
I agree with Lee completely - I will have a PE remap when I have some money and I feel that the Blitz controller is poor VFM (IMHO).
Looking for a tidier interim solution....
Thanks
Gavin
[This message has been edited by GavinP (edited 01-10-1999).]
But, I quoted the MRT book as it gives one opinion on the limits of various engine components. In context, I was trying to make the point that over 1.2bar is a very bad idea on a standard car - which was happening on Lee's car.
--------------------------------------------
Anyhow, I have a couple of further questions which hopefully can be answered:
1. Is there a cost-effective way of doing this (i.e. cheaper than PE remap, less crude than a bleed valve) ?
2. This is directed to Bob (if possible), how is the best way to go about learning more about this subject - have any books been published and how did you learn ?
I agree with Lee completely - I will have a PE remap when I have some money and I feel that the Blitz controller is poor VFM (IMHO).
Looking for a tidier interim solution....
Thanks
Gavin
[This message has been edited by GavinP (edited 01-10-1999).]
02 October 1999, 07:43 AM
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GavinP,
the only way to do the job properly is to change boost/ignition/fuelling ie the lot!
There are only 3 ways of doing this :
1.Aftermarket kits eg AFR/boost controller etc
2.Different ECU (whether this be a remap, or entirely new ECU such as Motec or the self-tune Possumlink)
3.Intercept the outputs from various sensors and alter them yourself electronically. A member here (Colin something..Bob has the URL) built a unit which plugged in-line with the standard connectors and the ECU and he adjusts the settings himself.
For the layman IMHO a PE remap or professionally fitted Motec are the only options.
Personally if it were a second car I would have gone for the Possum.
the only way to do the job properly is to change boost/ignition/fuelling ie the lot!
There are only 3 ways of doing this :
1.Aftermarket kits eg AFR/boost controller etc
2.Different ECU (whether this be a remap, or entirely new ECU such as Motec or the self-tune Possumlink)
3.Intercept the outputs from various sensors and alter them yourself electronically. A member here (Colin something..Bob has the URL) built a unit which plugged in-line with the standard connectors and the ECU and he adjusts the settings himself.
For the layman IMHO a PE remap or professionally fitted Motec are the only options.
Personally if it were a second car I would have gone for the Possum.
04 October 1999, 09:25 PM
#22
Ecu Specialist
Hi Gavin P, only just caught up with your post.
How to learn ? Mostly just experience brought about by a desire to "find out". I spent a lot of time experimenting with my previous cars (not Scube's, mainly Vauxhalls) and it taught me loads. I also got it wrong a few times as well and there's nothing like it to teach you to do it better next time !!
Books I know of and have read are ...
Automotive Electric/Electronic Systems by Bosch ISBN 1-56091-596-X
Bosch Fuel Injection and Engine Management by Probst published by Robert Bentley publishers ISBN 0-8376-0300-5
Maximum Boost by Corky Bell ISBN 1-899870-23-7
All excellant and informative if a little "heavy". The Bosch reference book covers all aspects of engine management.
If you can get your head round them they will give a good start.
Bob
How to learn ? Mostly just experience brought about by a desire to "find out". I spent a lot of time experimenting with my previous cars (not Scube's, mainly Vauxhalls) and it taught me loads. I also got it wrong a few times as well and there's nothing like it to teach you to do it better next time !!
Books I know of and have read are ...
Automotive Electric/Electronic Systems by Bosch ISBN 1-56091-596-X
Bosch Fuel Injection and Engine Management by Probst published by Robert Bentley publishers ISBN 0-8376-0300-5
Maximum Boost by Corky Bell ISBN 1-899870-23-7
All excellant and informative if a little "heavy". The Bosch reference book covers all aspects of engine management.
If you can get your head round them they will give a good start.
Bob
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