Chimaera serpentine T5 5ltr Rovergauge logs analysis
Discussion
Hi all,
I am based in Sydney Australia and have nearly completed a full body off restoration which included some engine mods.
It started life as a 4ltr but a previous owner had it stroked to 5ltr, but did nothing to the cylinder heads or induction side.
I have fitted big valve heads, 500 size trumpet base etc and ACT twin throttle plenum. I also swapped out the standard fuel regulator for an adjustable one. The cam was replaced by a similar profile to the TVR885. The stepper was been replaced and housing cleaned.
Unfortunately I am having issues with jerky running around 1200 to 1500rpms. I have swapped out both Lambda sensors, MAF but the problem still exists.
I have been using Rovergauge to try to indentify what is going on and the issue seems to be caused by a high -ve short term trim for both banks, with one bank consistently worse than the other. Long term trim for both banks is -100%.
I have captured the following logs and was hoping somebody (Blaze_Away ?) could review them and provide some insight.
1) 10 mins of idle at operating temp with MAF - Direct, Throttle - Absolute and Trim - Short
2) Short run with various rpm levels etc - Note this run always seems to trigger engine fault code 19 (Throttle pot to / MAF high)
I do have the following areas of concern.
1) The exhaust manifolds were ceramic coated inside and out but I suspect the pre-cats are still in there and could have been damaged
2) The possibility of an air leak somewhere - am arranging for a smoke test to determine this
3) The ACT plenum does not have a vacuum advance connection for the dizzy - currently blanked off at dizzy
4) Servicability of the fuel pump and the adjustable fuel regulator
I have spent some time going through other posts on here but need help with understanding exactly what RG is telling me.
Thanks
I am based in Sydney Australia and have nearly completed a full body off restoration which included some engine mods.
It started life as a 4ltr but a previous owner had it stroked to 5ltr, but did nothing to the cylinder heads or induction side.
I have fitted big valve heads, 500 size trumpet base etc and ACT twin throttle plenum. I also swapped out the standard fuel regulator for an adjustable one. The cam was replaced by a similar profile to the TVR885. The stepper was been replaced and housing cleaned.
Unfortunately I am having issues with jerky running around 1200 to 1500rpms. I have swapped out both Lambda sensors, MAF but the problem still exists.
I have been using Rovergauge to try to indentify what is going on and the issue seems to be caused by a high -ve short term trim for both banks, with one bank consistently worse than the other. Long term trim for both banks is -100%.
I have captured the following logs and was hoping somebody (Blaze_Away ?) could review them and provide some insight.
1) 10 mins of idle at operating temp with MAF - Direct, Throttle - Absolute and Trim - Short
2) Short run with various rpm levels etc - Note this run always seems to trigger engine fault code 19 (Throttle pot to / MAF high)
I do have the following areas of concern.
1) The exhaust manifolds were ceramic coated inside and out but I suspect the pre-cats are still in there and could have been damaged
2) The possibility of an air leak somewhere - am arranging for a smoke test to determine this
3) The ACT plenum does not have a vacuum advance connection for the dizzy - currently blanked off at dizzy
4) Servicability of the fuel pump and the adjustable fuel regulator
I have spent some time going through other posts on here but need help with understanding exactly what RG is telling me.
Thanks
Belle427 said:
I would hazard a guess the map in the ecu isnt right for a 500 engine.
It did have a 5ltr chip installed when it was stroked to 5ltr but of course that doesn't mean it is now matched after the changes.I do have a Griff 500 ECU I could swap in but really wanted to understand what is going on.
Here is what I've seen in the data.
The 3 charts attached are based on data as follows
005 My Chim as reference
077 Your chim stable idle
078 Your chim on a run
ALL DATA RUN CHARTS
Shows all the data from 005, 077 and 078 which shows everything looking good.
MAF RUN CHARTS
This shows your 077 v my 005 where yours is a bit more variable at idle.
MAF DISTRIBUTION
This shows again that your MAF is less stable than mine.
RE: Std deviation mine is 0.00285 vs yours at 0.00501
What this means is your MAF is putting out a signal that is more variable. Thus the ECU has difficulty in controlling the Fueling. What I have found is that When Std is under 0.004 cars run well when its over 0.007 they run badly and overfuel significantly. Yours being 0.005 is in that no-mans-land area not good but not really bad. If you have one I would suggest your swap out the maf and rerun the stable idle data collection again.
Also your Throttle position sensor could do with a slight adjustment. Yours is running at 0.052 v mine at 0.077. To adjust just loosen the screws and turn the body a little to increase the value, from memory that’s anticlockwise, but I might be wrong and its clockwise.
Other than that all other parameters look good.
|https://thumbsnap.com/5nvFMLxG[/url][url]
[url]
The 3 charts attached are based on data as follows
005 My Chim as reference
077 Your chim stable idle
078 Your chim on a run
ALL DATA RUN CHARTS
Shows all the data from 005, 077 and 078 which shows everything looking good.
MAF RUN CHARTS
This shows your 077 v my 005 where yours is a bit more variable at idle.
MAF DISTRIBUTION
This shows again that your MAF is less stable than mine.
RE: Std deviation mine is 0.00285 vs yours at 0.00501
What this means is your MAF is putting out a signal that is more variable. Thus the ECU has difficulty in controlling the Fueling. What I have found is that When Std is under 0.004 cars run well when its over 0.007 they run badly and overfuel significantly. Yours being 0.005 is in that no-mans-land area not good but not really bad. If you have one I would suggest your swap out the maf and rerun the stable idle data collection again.
Also your Throttle position sensor could do with a slight adjustment. Yours is running at 0.052 v mine at 0.077. To adjust just loosen the screws and turn the body a little to increase the value, from memory that’s anticlockwise, but I might be wrong and its clockwise.
Other than that all other parameters look good.
|https://thumbsnap.com/5nvFMLxG[/url][url][url]OK - I have replaced the MAF and it now looks like its variation is low. I have also altered the TPS to around 7.8.
Although this has not fixed the shunting Rovergauge is now reporting that is having to correct underfuelling now. The even bank is showing high +ve trim. The odd bank is showing mainly +ve but does occasionally go -ve.
Long term trim is actually now showing +100% for both banks which is the opposite of before.
The running fuel pressure was under 2.5 bar so I have increased it to 2.5 but this appears to have made no difference.
I will try swapping over the Lambda sensors to see if the problem moves to the other bank.
Still thinking potential air leak or an issue with one of the pre-cats. I also think that if it was a fuel map issue then both banks would be acting in a similar way but of course I could be wrong.
One odd thing I can't yet understand is why the reporting for the odd bank seems to stop after a while as if it gives up.
Latest logs have been sent to Blaze_Away review
Although this has not fixed the shunting Rovergauge is now reporting that is having to correct underfuelling now. The even bank is showing high +ve trim. The odd bank is showing mainly +ve but does occasionally go -ve.
Long term trim is actually now showing +100% for both banks which is the opposite of before.
The running fuel pressure was under 2.5 bar so I have increased it to 2.5 but this appears to have made no difference.
I will try swapping over the Lambda sensors to see if the problem moves to the other bank.
Still thinking potential air leak or an issue with one of the pre-cats. I also think that if it was a fuel map issue then both banks would be acting in a similar way but of course I could be wrong.
One odd thing I can't yet understand is why the reporting for the odd bank seems to stop after a while as if it gives up.
Latest logs have been sent to Blaze_Away review
OK thanks to Blaze_Away the TPS setting is better but the MAF Standard Deviation is still too high.
I understand that the MAF voltage at idle for a 5ltr should be around 1.75v or 35% at idle for a 5ltr. Looking at one of the logs it varies from 1.57 to 1.76v (Which is 31.4 - 35.2 %) which is a real problem. So onto the 3rd MAF to see what it runs like.
One question though: Is there any other reason why the MAF may be acting like this?
I understand that the MAF voltage at idle for a 5ltr should be around 1.75v or 35% at idle for a 5ltr. Looking at one of the logs it varies from 1.57 to 1.76v (Which is 31.4 - 35.2 %) which is a real problem. So onto the 3rd MAF to see what it runs like.
One question though: Is there any other reason why the MAF may be acting like this?
The sensor could be dirty effectively insulating it from the cooling air flowing over it.
To clean it you need extreme care.
Remove both end plates from the maf.
Squirt aerosol Maf cleaner onto the sensor several times until the sensor looks cleaner.
Reassemble and retest it.
FWIE it is my hypothesis that the higher standard deviations are an indicator of thermal damage to the electronics in the MAF.
To clean it you need extreme care.
Remove both end plates from the maf.
Squirt aerosol Maf cleaner onto the sensor several times until the sensor looks cleaner.
Reassemble and retest it.
FWIE it is my hypothesis that the higher standard deviations are an indicator of thermal damage to the electronics in the MAF.
Edited by blaze_away on Wednesday 15th November 14:38
blaze_away said:
The sensor could be dirty effectively insulating it from the cooling air flowing over it.
To clean it you need extreme care.
Remove both end plates from the maf.
Squirt aerosol Maf cleaner onto the sensor several times until the sensor looks cleaner.
Reassemble and retest it.
FWIE it is my hypothesis that the higher standard deviations are an indicator of thermal damage to the electronics in the MAF.
Interesting. Here is the history of the 4 MAFsTo clean it you need extreme care.
Remove both end plates from the maf.
Squirt aerosol Maf cleaner onto the sensor several times until the sensor looks cleaner.
Reassemble and retest it.
FWIE it is my hypothesis that the higher standard deviations are an indicator of thermal damage to the electronics in the MAF.
Edited by blaze_away on Wednesday 15th November 14:38
MAF-1 2nd hand supposedly working that I bought from another TVR owner here in Australia - labelled 5AM
MAF-2 Brand new one bought from Rover dealer which has probably only done a few hundred kms - no label
MAF-3 Used one from a Griff 500 that I have borrowed - no label
MAF-4 My old one which is the worst of the lot and the reason why I changed MAF in the first place - labelled 5AM
I'll check the condition of each one.
So from the above list the last logs came from MAF-2 which is the cleanest externally (Still looks shiny) but of course it is the inside that is important.
Time for an update.
Thanks to Blaze_Away's huge help in interpreting the logs and guidance it appears the jerkiness at light throttle has been greatly reduced. I will need to clear the ECU once more then do a couple of 100 kms or so to be sure and let the ECU re-learn.
Findings:
1) The standard deviation of the MAF was too high at idle. Tried 3 others and one successfully passed (just, so needs an eye kept on it) and is now permanently installed. Note: When Std Dev is under 0.004 cars run well when its over 0.007 they run badly and overfuel significantly
2) TPS set too low at idle. Adjusted. Note: Needs to be around the 7% mark
3) The IBP should be in the 30 to 40% region. Mine was 10 to 16%. So the IBP is not open enough at idle. This typically results in issues around ‘throttle off’ approaching junctions etc and jerky acceleration at lower revs. Adjusted to around 30% by lifting the base idle. Note: Had to re-adjust tps as playing with the base idle changed the TPS value.
So next steps :-
- Interpret the injector duty cycle and pulse width shown by RG. Mine look very low which is odd. I'll raise another topic for this
- Resolve overheating
Thanks to Blaze_Away's huge help in interpreting the logs and guidance it appears the jerkiness at light throttle has been greatly reduced. I will need to clear the ECU once more then do a couple of 100 kms or so to be sure and let the ECU re-learn.
Findings:
1) The standard deviation of the MAF was too high at idle. Tried 3 others and one successfully passed (just, so needs an eye kept on it) and is now permanently installed. Note: When Std Dev is under 0.004 cars run well when its over 0.007 they run badly and overfuel significantly
2) TPS set too low at idle. Adjusted. Note: Needs to be around the 7% mark
3) The IBP should be in the 30 to 40% region. Mine was 10 to 16%. So the IBP is not open enough at idle. This typically results in issues around ‘throttle off’ approaching junctions etc and jerky acceleration at lower revs. Adjusted to around 30% by lifting the base idle. Note: Had to re-adjust tps as playing with the base idle changed the TPS value.
So next steps :-
- Interpret the injector duty cycle and pulse width shown by RG. Mine look very low which is odd. I'll raise another topic for this
- Resolve overheating
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