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boost problem


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Hi Wayne,

The combination of the OBDII MAP reading and a visual of the car's boost gauge should verify the actual boost situation. There will be a small margin of error between the readings as they come from different circuits (my boost gauge reads a bit lower than the MAP), but they should shadow each other as the boost pressure changes. One further test Francesco could do is confirm that with the engine not running the MAP reading is close to the Barometer reading (if it was vastly out there should be an error code).

Also Francisco has disconnected the link from the boost solenoid to the wastegates (see point 4 above) and the car boosted to 0.75bar, hence it looks like the wastegate springs are strong enough to deal with boost above 0.35bar. I initially suspected the wastegate springs, but seems its not the problem on the evidence Francisco has supplied.

I'm not sure how the ECU could reduce the boost limit with the boost solenoid below the mechanical setting of 0.35bar. At the end of the day this mechanical setting is controlled by the physical spring and the setup of the wastegate. I wonder if the ECU is cutting the fuel (as it could do, according to the service manual if the boost is above 1.1bar for a longer period). It would be interesting to see the injector pulse widths (left & Right) from the transition from 0.35bar to 0.0bar. Would the fuel be cut if the ECU reset due to a hardware problem?

I would recommend that Francisco contacts Lotus Tech Support, as they know more than all of us put together.

I have to say its a mystery to me and look forward to getting a rational explanation for the symptoms and more important for Francisco finding out what was needed to fix the problem.

Regards,

Peter.

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i am with you peter. i am going to talk to the lotus service manager here in houston, TX today. at this point it is either something so simple that it may be embarassing to post, or an electronic problem with the ECU.

i will post what he says.

also, on peter's point above:

"I wonder if the ECU is cutting the fuel (as it could do, according to the service manual if the boost is above 1.1bar for a longer period). "

when i bought the car, the red-hose had disconnected accidentally, and i did not know. so when the overboosting would occur, fuel would be cutoff to the injectors, then the engine would stall out (kill). when the ODB scanner was connected there were misfire codes set. i guess my point here is that the ECU basically shuts down the engine to lower boost during an over-boosting condition. at least, it is what i experienced.

thanks for all the postings

i spoke with the lotus service manager. he is saying that based on the data, that it looks to him that there is an electrical problem (lower voltage than spec) between the ECM and the wastegate soloenoid even though a open ckt code is set when the harness is disconnected. i will take a voltage reading this weekend and see. he offered for me to bring the car in and go through the system with me to isolate the problem. i will do this next week. will keep you posted on the outcome

thanks

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  • 2 weeks later...

well,

it is still at the shop. i spoke to the service manager on friday, and he indicated that they are still troubleshooting. they have confirmed the following:

1. system is connected correctly

2. wastegate solenoid is working and the proper control signal is applied from the ECU

3. wastegates on the turbos seen to be ok

in other words, they are still trying to figure out what is going on

i will definetely post the resolution

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Keep us posted.

By the way, I have similar problem but took me a long time to figure. On the passenger side turbo, one of my silicone hose has an inch crack. In low boost, I have no problem boosting. In higher boost the crack will get bigger, The turbo will not boost over 5psi. The crack is the culprit (on mine). Took me a long time to figure because the silicone hose is wrapped by heat shield fabric material. I could'nt see it.

In a higher boost, can you hear something leaking?

Edited by Che
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i did not hear anything leaking, but honestly i was not actively listening either. the shop has it now, hopefully it is something simple like that, but they are indicating that they have checked the entire system. will post when they have a resolution. hopefully nothing embarassing for me.

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Keep us posted, based on everything I've read I am betting on a bad ECU. One look with a scope on the square wave going to the frequency valve (solenoid) would tell the story, if it's a wastegate control issue, but that still doesn't explain the boost going below .35 bar when it fails? The possibility of a cut or seam opening at higher boost and dumping all pressure fits the failure mode, but even that would have to dump the boost from the "good" side back through the plenum.

This should be a good story!

Wayne

The Older I get the Faster I was

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just received a call from lotus to ask me some questions to confirm what they are seeing is what i was seeing when i was troubleshooting the problem. in the conversation they indicated that they confirmed that the control signal from the ECU is "good." not sure how they verified this, they probably did not put it on an oscilloscpe.

one thing i have seen about three years ago on this car is as follows:

my ABS light would come on intermittently. checked all the sensors, etc... and could not figure out what the problem was. at one point we thought it was the ABS control board ($4000 ouch). it ended up being the alternator was fluctuating voltage slightly out of spec causing the ABS control board to set erroneous codes from time to time. after replacing the alternator, no more ABS issues.

my point here, is that i hope is not the ECU ($$$$), and some other electrical component that is causing the control signal to be slightly out of spec and not engage the wastegate solenoid valve.

will keep you posted on the progress

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Che,

You could very well be correct. If one turbo "locks up" after it gets warm, then the other turbo's boost could unload through the plenumn and then via the "locked" turbo and back out into the air intake. I would think there would be a major difference in left/right bank injector pulse width.

Wayne

The Older I get the Faster I was

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when i unplug the red-hose from the wastegate soloenoid, i get boost works fine. i then plug the red-hose right back and the problem re-appears. i can do this repeately with same results. i would think that if the problem was mechanical with the turbo sticking or locking up, removing the red-hose from the wastegate soloenoid would not restore boost. anyway i talked to the service manager yesterday, and they also see the wastegate duty cycle reading of 0% with their tech 1 scanner. they are thinking there is a problem with the wastegate solenoid control system, they are still troubleshooting.

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There are 2 things can happen in the wastegate actuator. Either stuck open or stuck close...sometimes

the rod does not move at all. There is something inside the canister (could be a binding spring) holding the rod. This is happening to my V8 now. Sometimes the rod works but sometimes stuck and won't move.

The diapram is good.

The rod must be free all the time.

If stuck open, you will get no boost (you can hear it). Stuck close, you will get boost or overboost.

This could be a mechanical issue...but I am waiting what they find.

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Fransisco;

Your point about repeatly unplugging the red boost control and getting "good" boost is well taken. I agree the turbo cannot be "locking up", good news. I now vote for a bad frequency solenoid, as long as the Lotus techs' say the pulse width and frequency (32 Htz) is correct. If Lotus's is using a tech1 scanner and "seeing reasonable duty cycles" when the failure occurs, is has to be the frequency solenoid (boost control valve).

Wayne

The Older I get the Faster I was

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Francesco, I agree with Wayne...

but boost control valve is not new to Lotus Esprit problem. Why can they simply replace and not wait 3 weeks

in the garage?

We are feeding you other idea (in boost issue), we figured the dealer did look at this first. This is elementary.

The boost control valve only cost $35.

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that is what i thought at first. i actually replaced the solenoid valve with a new one ($35). i beleive i mentioned in an earlier post. the dealer also said that they verified that the new solenoid valve is good. this is why i brought it into the shop. i was totally out of ideas. i thought for sure that replacing the wastegate solenoid valve was going to fix my problem

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update,

i just spoke with the service manager at the lotus dealership. here is what they are seeing:

1. they connect the tech1 scanner and send a manual code to the ECU to open the wastegate solenoid valve to ventilate the system and it works. the car will boost above .3 bars.

2. the ECU will not send the signal to the wastegate solenoid valve on its own.

3. they have checked all the things that could cause the ECU not to send the signal to provide additional boost, such as eng temp, knock sensor, TPS, etc... everything checks out ok.

they have concluded that electrically from the ECU to the wastegate solenoid valve it is ok, since they can manually send the signal with the Tech 1 scanner and the wastegate solenoid valve ventilates the system allowing additional boost.

basically they think at this point there is something going on within the ECU, but cannot determine what it is.

they are trying to contact Arnie Johnson, he was apparently the CEO of lotus at one point and involved in the development of the esprit, to get his input on where to look next.

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received an email from the service manager. here is what they are saying:

", the 5 lbs of boost that the ecm is allowing is all the ecm is going to allow. After talking to the Lotus managers and reps. they have informed me that the ecm will only allow 5 lbs of boost. Unless you aggressively accel in a gear the spike of boost may reach up to 7-8 lbs but the ecm will correct it to 5lbs only. There is a way to reset the parameters on the ecm to start from scratch that will allow the boost to stay in the upper range longer but as soon as the boost parameters are learned it will only allow you to stay at 5 lbs".

i obviuously disagree with this. since it is inconsistent with how the car operated since i have owned the car, and it is not what the service manual indicates. i will be meeting with the service manager today.

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