Won't hold boost pressure
Discussion
For months I have thought the reason I could not hold max boost was because the BOV was opening too soon. I disconnected the BOV but still as soon as I reach max boost (in any gear) the engine coughs/stumbles/hesitates and the boost gauge goes back down to normal. The boost gauge does go all the way to the far right. Everything else seems fine. Any ideas?
Sounds like too much boost pressure (leak in wastegate pipe possibly) is putting the management system into shutdown mode until the pressure drops back off whereupon the management resumes normal operation, hence the stuttering at the top of this cycle. Should be fairly easy to sort out. Most management systems on production engines incorporate this to prevent meltdown if the owner enjoys the extra boost caused by a fault and chooses to leave the fault in place !
Maybe too much boost pressure, oh no! A few months ago I had to 330hp moto-concept chip installed. Please don't tell me I should go back to the original chip (which for some unknown reason I do not have). I think it might have been doing this, but not as bad, before the new chip was installed.
The wastegate was removed when a new exhaust system was installed. The PO had wired it open and it was literally a clump of useless rusted metal.
>> Edited by Skerd on Monday 16th December 12:27
The wastegate was removed when a new exhaust system was installed. The PO had wired it open and it was literally a clump of useless rusted metal.
>> Edited by Skerd on Monday 16th December 12:27
I would have thought that the chip supplier/installer should have checked all this out when it was done. Each chip should be programmed to work at its best at a predetermined boost pressure, and they really should at least stick a gauge on it to check at installation time. I would suggest you get to a turbo specialist and seek advice, although I would have thought the chip people should be giving you some answers.
You checked your vac line to the wastegate right?
If the line is off and it goes into over boost the ECU will cut fuel to injectors and it will sputter and stall until the condition goes away. It happens right around 3-4 K and then the car drives fine without a miss when the turbo is not being used. It will happen even with the stock chip.
Calvin
If the line is off and it goes into over boost the ECU will cut fuel to injectors and it will sputter and stall until the condition goes away. It happens right around 3-4 K and then the car drives fine without a miss when the turbo is not being used. It will happen even with the stock chip.
Calvin
Thanks to both of you.
Calvin - I am having temporary amnesia, but is the wastegate the "flap" in the exhaust system? That was totally rusted into a piece of non-moving junk and removed (and not replaced) when I had a new exhaust system installed.
>> Edited by Skerd on Tuesday 17th December 12:36
Calvin - I am having temporary amnesia, but is the wastegate the "flap" in the exhaust system? That was totally rusted into a piece of non-moving junk and removed (and not replaced) when I had a new exhaust system installed.
>> Edited by Skerd on Tuesday 17th December 12:36
The wastegate is right after the turbo and has an actuator arm from wastegate capsule It is this capsule that the line to acutate sometimes just pops off. When I first got my Esprit I went for a ride in my friends Josh's car he had all the upgrades on his SE including the S4s chip. He said check this out and stomped on accelerator, the boost gauge pegged to show a lighting fast turbo spool. the fastest I had ever seen to before. I thought I have to get me one of those chip. Then the engine sputtered and felt like it was running out of fuel. Then I thought nah maybe the chip is not so great. We pulled over and the hose to the wastegate capsule had just come off. The engine was just trying to protect it from over boost and cut fuel to the injectors. That flap thing you are talking about could it be the EBPV (exhaust back pressure valve)? Right before the entrance to the muffler. That would have very little to do with it unless it was stuck closed. I have also heard of the cat breaking apart and clogging the muffler. Give an exact descrption of the symtoms. When does it stumble? At what rpm and throttle opening? What engine temp or is it all the time? Does it stumble and miss during non turbo operation? Is the fuel pressure at spec's to handle the pressure needed for the turbo to kick as strong as it should?
Calvin
Calvin
Calvin: You are the man. Your ride in
your friends car sounds awfully familiar!
My bad on the EBPV mis-identity. It does
it all the time AT MAX BOOST, so that is all
different RPM, but usually around 3-4K.
I only would max it out when the car is fully
warmed up, so it is when fully warm. It does
not do it during non-turbo operation. I will
check that line going to the turbo ASAP.
Thanks again.
your friends car sounds awfully familiar!
My bad on the EBPV mis-identity. It does
it all the time AT MAX BOOST, so that is all
different RPM, but usually around 3-4K.
I only would max it out when the car is fully
warmed up, so it is when fully warm. It does
not do it during non-turbo operation. I will
check that line going to the turbo ASAP.
Thanks again.
Last night I checked all connections at the turbo. Nothing is disconnected. On pages 34 and 35 of Section EF of the Lotus repair manual (93 and up version) it has a bit on the turbocharger and wastegate. Do you mean the pressure sensing hose? It was connected, I just want to make sure I concentrate on the correct thing.
Yes it is the pressure sensing hose. There is also a chance that the waste gate actuation capsule is bad or needs adjustment. Be very carefull when adjusting the capsule rod and nut. The shaft of this rod must spin at all only the nut as it will tear loose from the diaphram and the capsule will be broken at that time. From you descrption I am almost certain that the turbo is going into overboost and the fuel is being cut to the injectors. Look for cracks in the line, the connection on the other end as you fllow this line. Perform tests to insure the wastegate is opeming. be careful about the wastegate do not break it while testing. I think there is a section on testing this capsule in the manual. I'll check when I go home if you can not find it.
Calvin
Calvin
Maybe the dealer is the best place in this instance. If the rod rotates during adjustment the diaphram will tear. only the nut should move. Many of the nuts are frozen by rust and such. There is a chance the other side of the actuator hose or the hose itself has a leak. I have heard of the waste gate going bad. Depends on the miles. Several people seem to have the problem after 50K miles.
Good luck
Calvin
Good luck
Calvin
Thought I'd post in case it's any use. A good way to check for leaks like this is a plant sprayer and a torch. Get someone to rev the engine, and spray a fine mist, using the torch if necessary to see the mist. Any disturbance to the mist shows where the leak is. It's a good way of finding holes or cracks in pipes of joints which are too small to see.
Calvin or ?,
This sounds possibly similar to what I just noticed recently. There's a local small hill I like to climb in 3rd starting at 2.9k rpm at full throttle. With the new chargecooler pump rebuild and the S4sMkV chip I did a couple months ago, she just pulls that hill like a dream, torque and all. But, the last two times I've done it, a few seconds after the boost is at 1 (max), the power/torque falls a bit. Almost feels like a slipping clutch, but that's not the case because the rpm doesn't rise, just a slight loss of power. In all other cases I have not experienced that sudden slight drop in power/torque. I have to pay more attention to see if the boost guage is dropping then too, cause I'm usually watching the road.
I have Freescan. Do you think if I logged that 1/4 mile run that the cause might show up on the logs, which could point to waste gate diaphragm or leak or something?
I also thought maybe it could be, since the weather is colder now, that maybe I was at 82C when I started, and somehow dropped to 81C, such that it might cause it to limit the boost right then. Is that possible? BTW, I do have 50k miles on her.
thx
- Mark91SE
This sounds possibly similar to what I just noticed recently. There's a local small hill I like to climb in 3rd starting at 2.9k rpm at full throttle. With the new chargecooler pump rebuild and the S4sMkV chip I did a couple months ago, she just pulls that hill like a dream, torque and all. But, the last two times I've done it, a few seconds after the boost is at 1 (max), the power/torque falls a bit. Almost feels like a slipping clutch, but that's not the case because the rpm doesn't rise, just a slight loss of power. In all other cases I have not experienced that sudden slight drop in power/torque. I have to pay more attention to see if the boost guage is dropping then too, cause I'm usually watching the road.
I have Freescan. Do you think if I logged that 1/4 mile run that the cause might show up on the logs, which could point to waste gate diaphragm or leak or something?
I also thought maybe it could be, since the weather is colder now, that maybe I was at 82C when I started, and somehow dropped to 81C, such that it might cause it to limit the boost right then. Is that possible? BTW, I do have 50k miles on her.
thx
- Mark91SE
The S4s chip does put additional strain on the turbo but with a well functioning turbo it should not be a problem. Are you exeriencing the 3K stumble that maybe inherent in MKV chip? Take it at high R's and see if it still stumbles. What we are talking about a serious loss of boost and not a stumble. You would know a total loss of boost in an SE.
Calvin
Calvin
Quote: Take it at high R's and see if it still stumbles.
Normally, it runs full range on rpm just fine. No misfiring or anything. And I get good boost, but mainly drive on flat roads. It's just that hill, where it can be obvious (just 2 times so far).
As soon as it stops raining I'll try again.
thx
Normally, it runs full range on rpm just fine. No misfiring or anything. And I get good boost, but mainly drive on flat roads. It's just that hill, where it can be obvious (just 2 times so far).
As soon as it stops raining I'll try again.
thx
The loss of boost hasn't happened since. But, I think the problem was essentially because I might have been right on the threshold of 82deg which is required for full boost. And, when speeding up the increased air flow cooled it down and it crossed below the threshold. That's the only thing I can figure.
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