Intermittent Boost
Discussion
I posted a problem in November with my 90SE regarding intermit boost but still have not found the cause. I can get full boost in 4th gear all the way to redline , shift to 5 th , mash the throttle and get zero boost. Try it again and it 's fine. Seems only to happen after gear change. Not getting engine light so I'm feeling it is mechanical , maybe waist gate hanging up.
Any thoughts ?
SGB
Any thoughts ?
SGB
Hi,
I have a suspicion that it may be your chargecooler. If the ECU picks up a temp greater than 70°, it will cut the boost. FYI, there is no mechanical link between the gearbox and the turbo so switching gears by itself will have no effect.
If on a run, you may be fine on boost through 4th gear. But, by the time you get to 5th, you may have too high a chargecooler temp so the ECU cuts out the boost. As soon as the temp settles back down, the ECU allows boost again.
Immediately after a spirited run, place your hand on the chargecooler, it should feel slightly cold to the touch. If not, your impeller is probably faulty. It can loose some of it's rubber blades, or I have actually seen one which became convex through heat deformation and didn't make contact with the pump walls for the middle third of it's length. This caused sufficient loss of coolant flow on my friend's S4s that the chargecooler temp rose to the point that the ECU cut out the boost. This was deceiving as we first thought the impellor looked ok (all blades intact). Only when we removed it did we discover the convex deformation which took place. We replaced the impellor with the new one and it instantly cured the problem.
The impellor is located on the right hand side of the engine under the intake manifold/plenum and is mechanically driven off the Auxillary/Oil pump shaft.
To change it, first buy the replacement impellor and cover gasket. Then drain some of the chargecooler fluid (on the SE I believe that it shares the engine coolant and is not a separate circuit). Remove the 3 (4?) 10mm bolts holding on the cover. Once the cover is off, pull out the old impeller, dip the new one in glycol to provide lubrication on 1st start, and replace. Refit new gasket and cover then fill/bleed the system. Hope this helps. Happy Motoring!... Jim'85TE
I have a suspicion that it may be your chargecooler. If the ECU picks up a temp greater than 70°, it will cut the boost. FYI, there is no mechanical link between the gearbox and the turbo so switching gears by itself will have no effect.
If on a run, you may be fine on boost through 4th gear. But, by the time you get to 5th, you may have too high a chargecooler temp so the ECU cuts out the boost. As soon as the temp settles back down, the ECU allows boost again.
Immediately after a spirited run, place your hand on the chargecooler, it should feel slightly cold to the touch. If not, your impeller is probably faulty. It can loose some of it's rubber blades, or I have actually seen one which became convex through heat deformation and didn't make contact with the pump walls for the middle third of it's length. This caused sufficient loss of coolant flow on my friend's S4s that the chargecooler temp rose to the point that the ECU cut out the boost. This was deceiving as we first thought the impellor looked ok (all blades intact). Only when we removed it did we discover the convex deformation which took place. We replaced the impellor with the new one and it instantly cured the problem.
The impellor is located on the right hand side of the engine under the intake manifold/plenum and is mechanically driven off the Auxillary/Oil pump shaft.
To change it, first buy the replacement impellor and cover gasket. Then drain some of the chargecooler fluid (on the SE I believe that it shares the engine coolant and is not a separate circuit). Remove the 3 (4?) 10mm bolts holding on the cover. Once the cover is off, pull out the old impeller, dip the new one in glycol to provide lubrication on 1st start, and replace. Refit new gasket and cover then fill/bleed the system. Hope this helps. Happy Motoring!... Jim'85TE
When I first puchased the car in Feb 2001 I was not getting boost at all until I changed the chargecooler impeller. The increase in horsepower was staggering.
I have put 20000 kms on since then so I was not suspecting the impeller but anything is possible. I'll test the Chargecooler temp after a run and see what I have. Yes the SE has a stand alone chargecooler system. Thanks for your input Jim.
SGB
I have put 20000 kms on since then so I was not suspecting the impeller but anything is possible. I'll test the Chargecooler temp after a run and see what I have. Yes the SE has a stand alone chargecooler system. Thanks for your input Jim.
SGB
windsorlotus said:
When I first puchased the car in Feb 2001 I was not getting boost at all until I changed the chargecooler impeller. The increase in horsepower was staggering.
I have put 20000 kms on since then so I was not suspecting the impeller but anything is possible. I'll test the Chargecooler temp after a run and see what I have. Yes the SE has a stand alone chargecooler system. Thanks for your input Jim.
SGB
SGB,
Since installing the impellor, has there been any work done to the cam belt? If so, and IF the Aux. Pulley was counter-rotated even slightly the impellor was almost certainly damaged.
As you are aware, the impellor blades are straight, but conform/orient to the curve inside the pump body in the direction consistent with the shaft's rotation. The tolerance is so tight in the pump body that there is insufficient room inside for the blades to reverse themselves. If the shaft is counter-rotated, even the slightest bit, the rubber blades will tear or break. This failure may be either sudden or progressive. And as I discovered, there is the possibility of blade deformation, which of course could occur in normal running. BTW, you say you've gone 20000km since changing the impellor. At what mileage did you make the change? It may simply be time again.
Another possibility could be that your chargecooler needs a good flushing. I would undertake this if changing the impellor to insure that no debris in the system could damage the new part.
Hope this solves your issue as it's about the easiest/cheapest variable I can think of. Happy Motoring!... Jim'85TE
>> Edited by lotusguy on Monday 23 February 03:55
>> Edited by lotusguy on Monday 23 February 03:57
>> Edited by lotusguy on Monday 23 February 04:00
I had exactly the same problem with mine, when I changed gear ( and nearly always from 2nd to 3rd ), no boost but then it would come back after a few seconds. I would not do it every time, just sometimes. I even maganged to guess what was happening and my dealer fixed it quite easily.
It was this : The waste gate was sticking open. So, when you change gear, the waste gate opens, you select the next gear, waste gate stays open and there you go, no boost !! They told me that the waste gate acutator arm was bent. They just took it off and straightened it out and it's been fine since.
BTW - 'Waist' is the bit round your middle !!!!
Adrian
97GT3
www.adrianmugridge.co.uk
>> Edited by adrianmugridge on Monday 23 February 08:53
It was this : The waste gate was sticking open. So, when you change gear, the waste gate opens, you select the next gear, waste gate stays open and there you go, no boost !! They told me that the waste gate acutator arm was bent. They just took it off and straightened it out and it's been fine since.
BTW - 'Waist' is the bit round your middle !!!!
Adrian
97GT3
www.adrianmugridge.co.uk
>> Edited by adrianmugridge on Monday 23 February 08:53
Adrian,
Good Call! I too thought of the wastegate, but ruled it out as SGB states that the rpoblem only occurred during the 4/5 shift. My thought is that a sticky wastegate will stick sportically and not consistently on only one shift. This is why I think there may be some chargecooler involvement. What do you think? Happy Motoring! ...Jim'85TE
Good Call! I too thought of the wastegate, but ruled it out as SGB states that the rpoblem only occurred during the 4/5 shift. My thought is that a sticky wastegate will stick sportically and not consistently on only one shift. This is why I think there may be some chargecooler involvement. What do you think? Happy Motoring! ...Jim'85TE
Adrian,
Good Call! I too thought of the wastegate, but ruled it out as SGB states that the problem only occurred during the 4/5 shift. My thought is that a sticky wastegate will stick sportically and not consistently on only one shift. This is why I think there may be some chargecooler involvement. What do you think? Happy Motoring! ...Jim'85TE
Good Call! I too thought of the wastegate, but ruled it out as SGB states that the problem only occurred during the 4/5 shift. My thought is that a sticky wastegate will stick sportically and not consistently on only one shift. This is why I think there may be some chargecooler involvement. What do you think? Happy Motoring! ...Jim'85TE
Jim
When I had the same thing I also wondered about it being the wastegate as it only ever seemed to do it from 2rd to 3rd and nearly always under max boost as well. There could be some problems with the chargecooler as you suggest also. I had problems with mine before replacing the impellor ( but that was to stop a water leak in the main ). The engine was getting very hot and that caused a major lack of power. But, as you say, the test for a problem with the chargecooler is simple, just put your hand on the top of the CC and if it's hot then something's amiss. But, I think I'd bet on the wastegate actuator rod more than the CC.
Adrian
When I had the same thing I also wondered about it being the wastegate as it only ever seemed to do it from 2rd to 3rd and nearly always under max boost as well. There could be some problems with the chargecooler as you suggest also. I had problems with mine before replacing the impellor ( but that was to stop a water leak in the main ). The engine was getting very hot and that caused a major lack of power. But, as you say, the test for a problem with the chargecooler is simple, just put your hand on the top of the CC and if it's hot then something's amiss. But, I think I'd bet on the wastegate actuator rod more than the CC.
Adrian
Tested the chargecooler today and it is ice cold. The wastegate actuator rod looks straight but it could be slightly bent. I will take it off tomorrow and check it out. Keep you posted on progress.
Thx for the input guys.
P.S. The 4/5 shift was just an example, It has happenned 2/3, 3/4 as well.
SGB
Thx for the input guys.
P.S. The 4/5 shift was just an example, It has happenned 2/3, 3/4 as well.
SGB
Is it possibly a partially colapsed air inlet pipe to the turbo. The pipe that runs from air box to turbo, internally there may be an obstruction that restricts flow on occasion. I believe the concerina section of pipe has an inner and outer layer, if the inner layer comes away it can either act as a flap or balloon out to block the pipe.
Possibly when changing gear th reversing or change in air flow from on high boost to no boost/reverse air flow may cause it to temporaily block pipe. Once air settles down it un blocks and gives air flow back once more.
Still sounds more wastegate logically but never know ?
Possibly when changing gear th reversing or change in air flow from on high boost to no boost/reverse air flow may cause it to temporaily block pipe. Once air settles down it un blocks and gives air flow back once more.
Still sounds more wastegate logically but never know ?
Hey guys , sorry it took so long to get back on my intermit boost problem. I took it out today for the first spirited run of the season with an ambient temp of aprox 50 degrees. The boost worked flawlessly in every gear so I am inclined to go with the chargecooler impeller theory. I will pull it and see what it looks like. Keep you posted.
THX
SGB
THX
SGB
Here's some pics I took of my Chargecooler Pump R&R! The rubber was melted into the inlet/outlet pipe holes! I also had a problem with shaft scoring which made it really really hard to remove.
www.voicecrystal.com/Esprit/Chargecooler/Pump/
- Mark91SE
www.voicecrystal.com/Esprit/Chargecooler/Pump/
- Mark91SE
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