GT-Four not making full boost...
Discussion
Recently when driving I've noticed the GT-Four (ST205) isn't reaching the top of the boost gauge. A week ago it was going up to the penultimate graduation, but after (and during) a hot rolling road day yesterday it's only making it up to two away from the top. The dyno also gave a rather disappointing reading of 197.4 bhp. It feels noticably slower than before as you would imagine!
The dyno tester reckoned that it could be the wastegate actuator has gone/is going, but a similar thread on GT4OC suggested that it may be linked to hot weather.
Does anyone have any useful info on this? I'd like to have it running full power asap, but don't want the hassle of changing the wastegate actuator if it's solely caused by it being a bit warm outside!
ETA: Another question I have is about the under vent shield- the one that lives under the main bonnet vent. The dyno man slammed the bonnet (made me cringe, but obviously theres a technique to shutting an aluminium bonnet) and I later found that the shield had come off as one of the clips had fallen out. What are the implications of this? I'm happy to go without, but not if it will cause any mechanical issues.
The dyno tester reckoned that it could be the wastegate actuator has gone/is going, but a similar thread on GT4OC suggested that it may be linked to hot weather.
Does anyone have any useful info on this? I'd like to have it running full power asap, but don't want the hassle of changing the wastegate actuator if it's solely caused by it being a bit warm outside!
ETA: Another question I have is about the under vent shield- the one that lives under the main bonnet vent. The dyno man slammed the bonnet (made me cringe, but obviously theres a technique to shutting an aluminium bonnet) and I later found that the shield had come off as one of the clips had fallen out. What are the implications of this? I'm happy to go without, but not if it will cause any mechanical issues.
Edited by Twincharged on Monday 29th June 11:08
Just take the rain tray off from under the vent. In this weather especially, you don't want the engine bay being any warmer than it has to be!
As said, first off, get your error codes, read by bridging the connections in the diagnostics port.
see www.gtfours.co.uk for details.
Common one is code 54 relating to low charge cooler coolant.
Reset the ecu by disconnecting the battery for a couple of minutes, or pulling the ecu fuse.
As said, first off, get your error codes, read by bridging the connections in the diagnostics port.
see www.gtfours.co.uk for details.
Common one is code 54 relating to low charge cooler coolant.
Reset the ecu by disconnecting the battery for a couple of minutes, or pulling the ecu fuse.
Marf said:
Pull the fault codes and see if anything is registered. If the GT-Four is anything like the MR2 then it will revert to safe boost(7/8psi) under certain conditions.
Precisely. I'm guessing "limp mode". I wonder if you've hit fuel cut recently....And bin the vent shield and marvel in the hot air pouring out of the bonnet...
I've had a check of the fault codes both yesterday morning and tonight and there's no fault code. A quick visual inspection reveals no issues with the hoses, although not all of them can be checked without taking bits apart.
I'll give it a drive later to see if it still has the same issue and go from there. If so I'll try and fit in a stripdown tomorrow...
With regard to the vent shield my main concern was the hot turbo being splashed with cold water when driving which would not be good for it in the long term. I have noticed that it the engine bay kicks out a lot of heat in general so that's why I was asking, but as the general consensus is get rid then I'll keep it off!
(It has been noted in the past that the vent grille has the same diamond mesh as a disposable barbeque and could be used as one- maybe the shield is a drip tray?)
I'll give it a drive later to see if it still has the same issue and go from there. If so I'll try and fit in a stripdown tomorrow...
With regard to the vent shield my main concern was the hot turbo being splashed with cold water when driving which would not be good for it in the long term. I have noticed that it the engine bay kicks out a lot of heat in general so that's why I was asking, but as the general consensus is get rid then I'll keep it off!
(It has been noted in the past that the vent grille has the same diamond mesh as a disposable barbeque and could be used as one- maybe the shield is a drip tray?)
Certainly it should go off the top of the scale in every gear (stock boost gauge is pretty useless to be honest)
Twincharged said:
(It has been noted in the past that the vent grille has the same diamond mesh as a disposable barbeque and could be used as one- maybe the shield is a drip tray?)
I couldn't possibly comment....Mr E said:
Certainly it should go off the top of the scale in every gear (stock boost gauge is pretty useless to be honest)
That either means:Twincharged said:
(It has been noted in the past that the vent grille has the same diamond mesh as a disposable barbeque and could be used as one- maybe the shield is a drip tray?)
I couldn't possibly comment....a) You've tried the barbeque idea
b) You've thought the same before
or c) I should have added a
smiley!With regard to the gauge, while it's not massively useful as it doesn't give pressure readings, Mines been fairly good as a general indicator so far- the two graduations have been matched to my drop in power. Still something I'd consider upgrading in the future though.
Remove the turbo heat shield and then pull the little pipe off the turbo. The one that goes from the turbo pressure takeoff nozzle to the actuator. Attach a foot pump (with a gauge on it) to this hose and pump it up. You should see the actuator push rod behind the turbo start to move around 0.5 bar and be fully open by 0.7 bar.
Also check that all the large hoses between the turbo and the throttle body are good and tight.
When you checked for error codes, did you get a continuously flashing engine light?
Also check that all the large hoses between the turbo and the throttle body are good and tight.
When you checked for error codes, did you get a continuously flashing engine light?
The engine light is flashing continuously, and the coolant in the chargecooler is topped right up.
The footpump idea sounds like a good one- I'll be doing a stripdown of the area when I get chance so I'll definitely give that one a try. Good knowledge as always Bodhi
; I did follow your suggestion of posting on GT4OC, but found out I need to be a full member to post on (from what I can tell) all but the sales forums.
The footpump idea sounds like a good one- I'll be doing a stripdown of the area when I get chance so I'll definitely give that one a try. Good knowledge as always Bodhi
; I did follow your suggestion of posting on GT4OC, but found out I need to be a full member to post on (from what I can tell) all but the sales forums.Twincharged said:
The engine light is flashing continuously, and the coolant in the chargecooler is topped right up.
The footpump idea sounds like a good one- I'll be doing a stripdown of the area when I get chance so I'll definitely give that one a try. Good knowledge as always Bodhi; I did follow your suggestion of posting on GT4OC, but found out I need to be a full member to post on (from what I can tell) all but the sales forums.
Has it ever made full boost since you have had it? You would know as the gauge would go right up by the + sign.The footpump idea sounds like a good one- I'll be doing a stripdown of the area when I get chance so I'll definitely give that one a try. Good knowledge as always Bodhi
; I did follow your suggestion of posting on GT4OC, but found out I need to be a full member to post on (from what I can tell) all but the sales forums.If not, then the VSV may be disconnected. If its the charge cooler causing you issues, ditch it and just get a big FMIC.
Mr E said:
Twincharged said:
That either means:
a) You've tried the barbeque idea
a) You've tried the barbeque idea
Twincharged said:
The engine light is flashing continuously, and the coolant in the chargecooler is topped right up.
That's not good. And you say there are no codes?
RobCrezz said:
Has it ever made full boost since you have had it? You would know as the gauge would go right up by the + sign.
If not, then the VSV may be disconnected. If its the charge cooler causing you issues, ditch it and just get a big FMIC.
I have had full boost a few times from what I can tell(I live in Birmingham City Centre, so not many places where this can be done!) but concentrating on the gauge wasn't my priority at the time! I know that the chargecooler is sucking the fluid down, but other than that I'm not sure what's working.If not, then the VSV may be disconnected. If its the charge cooler causing you issues, ditch it and just get a big FMIC.
I did drive the car last night and today- last night it was two from the top again, and today it was even further down, so it appears the problem is getting gradually worse. Perhaps there is a part failing gardually, or a hose is leaking more and more... I'll strip it down at the weekend at the latest I think.
Twincharged said:
Mr E said:
That's not good. And you say there are no codes?
It's flashing continuously when the diagnostic port is bridged, but not on at all under normal operation (which AFAIK suggests "everything's fine")- I should have put that as answer to Bodhi's question.I'd investigate the wastegate next I suspect - is it stuck open?
I've been having a poke around, and one of the things that looks a bit loose is the hose between the chargecooler and the throttle body. I loosened the hose to try and get it further onto the chargecooler, but couldn't really get it any further on. To add to the calamity, I forgot to tighten the jubilee clip before a short test drive, resulting in a large dump-valve-esque hiss 
.
Is the best way going to be to take the whole thing off the throttle body, tighten the jubilee clip around the chargecooler and then tighten the other end back to the throttle body? The design of the throttle body ends makes it difficult to get the bolts out- I imagine in the factory these were tighened before the chargecooler was installed. I'll have to spray some WD-40 on the bolts so can't do the job until the car has cooled down!
This is of course still speculation- it looked loose before and certainly is now, but obviously until I rectify the hose then I can't comment on whether it's the root cause of the entire problem.
.Is the best way going to be to take the whole thing off the throttle body, tighten the jubilee clip around the chargecooler and then tighten the other end back to the throttle body? The design of the throttle body ends makes it difficult to get the bolts out- I imagine in the factory these were tighened before the chargecooler was installed. I'll have to spray some WD-40 on the bolts so can't do the job until the car has cooled down!
This is of course still speculation- it looked loose before and certainly is now, but obviously until I rectify the hose then I can't comment on whether it's the root cause of the entire problem.
The air-in hose that comes from the air filter is a weak point on the GTfours, when I had mine it twice developed a split. It resulted in the measured air not being correct in the engine and was running too rich. (Probably won't show up on an error code).
The split usually occurs underneath and therefore out of sight. So maybe a good idea to remove some hoses and have a good check.
The split usually occurs underneath and therefore out of sight. So maybe a good idea to remove some hoses and have a good check.
On the ST205, the split intake hose is much less of an issue as it runs a MAP sensor to measure air at the manifold unlike the airflow meter on the ST185s. Although a split intake can cause turbulent air problems at the turbo mouth.
With the chargecooler, undo the three bolts that hold it down, loosen the jubilee clips on the front and rear hoses. Twist and slide the front hose, off the turbo and up the pipe towards the body of the chargecooler until you can see the gap between the turbo and cooler pipe. pull the small hose off the back of the chargecooler (around about the middle of the box at the back).
Now, stand in front of the car and wiggle the chargecooler whilst pulling towards you. when it pops out the throttle body rubber, fold it up and to the right and prop it/tie it up out of the way.
The bottom of the throttle body rubber can be prone to splitting and would certainly lose you boost, although it would likely sound a bit like the hissing noise you heard when it wasn't tightened properly.
Chris
With the chargecooler, undo the three bolts that hold it down, loosen the jubilee clips on the front and rear hoses. Twist and slide the front hose, off the turbo and up the pipe towards the body of the chargecooler until you can see the gap between the turbo and cooler pipe. pull the small hose off the back of the chargecooler (around about the middle of the box at the back).
Now, stand in front of the car and wiggle the chargecooler whilst pulling towards you. when it pops out the throttle body rubber, fold it up and to the right and prop it/tie it up out of the way.
The bottom of the throttle body rubber can be prone to splitting and would certainly lose you boost, although it would likely sound a bit like the hissing noise you heard when it wasn't tightened properly.
Chris
Right...
I stripped the whole thing back to under the chargecooler (including a lot of the antilag stuff which got in the way)and there were no split hoses, but I was stumped by a heatshield bolt that got rounded off and I can only get the socket for rounded bolts tomorrow. I decided to put everything back together extra tight and drive it again before assuming that it's definitely the wastegate actuator... and on the test drive I had booooost again
. However, a combination of a stressed turbo pipe and a tight jubilee clip meant that the latter broke 
, and it's one that has a throttle cable holder on so not a standard part. This technically means I have to wait several days to drive the car again, but in reality I'll probably have a go at bodging the holder onto a standard clip and get the proper one later.
I did notice that in 2nd gear (my test due to torque-limited 1st) I only seemed to get up to the penultimate boost marker. I have therefore concluded that it's due to the following possibilities:
One thing I have learned from the experience is the other side of the PH knowledge consultation process. I always read threads about a problem and if the symptoms seem to point to one thing you calmly point out to the worried owner that's flapping around madly that it'll probably be the obvious problem. In this case it's been me on the other side and despite noticing that about other posters, I've done a massive amount of flapping about too
Anyway, the main reason for this post is to give a great big thanks to everyone for their help, I'm really pleased to have it (pretty much!) sorted. A good reminder of the impressive knowledge of the PH / Jap Chat collective!
I stripped the whole thing back to under the chargecooler (including a lot of the antilag stuff which got in the way)and there were no split hoses, but I was stumped by a heatshield bolt that got rounded off and I can only get the socket for rounded bolts tomorrow. I decided to put everything back together extra tight and drive it again before assuming that it's definitely the wastegate actuator... and on the test drive I had booooost again
. However, a combination of a stressed turbo pipe and a tight jubilee clip meant that the latter broke , and it's one that has a throttle cable holder on so not a standard part. This technically means I have to wait several days to drive the car again, but in reality I'll probably have a go at bodging the holder onto a standard clip and get the proper one later.I did notice that in 2nd gear (my test due to torque-limited 1st) I only seemed to get up to the penultimate boost marker. I have therefore concluded that it's due to the following possibilities:
- Wastegate actuator really is on its way out, only not as much as originally thought
- Turbo hose knackered due to years of heat cycles and flex/leakage is allowing boost out
- Boost gauge not very good (as MR E has advised)
One thing I have learned from the experience is the other side of the PH knowledge consultation process. I always read threads about a problem and if the symptoms seem to point to one thing you calmly point out to the worried owner that's flapping around madly that it'll probably be the obvious problem. In this case it's been me on the other side and despite noticing that about other posters, I've done a massive amount of flapping about too
Anyway, the main reason for this post is to give a great big thanks to everyone for their help
, I'm really pleased to have it (pretty much!) sorted. A good reminder of the impressive knowledge of the PH / Jap Chat collective!Gassing Station | Japanese Chat | Top of Page | What's New | My Stuff