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davep

537 posts

164 months

[news] 
Monday 16th July 2012 quote quote all
bubblehead said:
Just a quick note to say a big thanks to Mark and the software developers, the lead and software worked perfectly and helped me track down what was becoming a significant problem quickly. Car is now running like a dream (touch wood) and i would recommend this bit of kit to anyone still running a 14cux, superb.
As a fellow pre-cat owner and RoverGuage user I'd be interested to know what the fault and significant problem were. Also what fuel maps your car uses. PM if you prefer.

blitzracing

Original Poster:

3,758 posts

100 months

[news] 
Monday 16th July 2012 quote quote all
bubblehead said:
Mark my screen has a line for target idle speed but it's empty.....it's a 4.3 precat if that matters but it seems to idle fine at about 1000rpm, just curious why i don't have a target idle speed?
I can only think the software equests data from locations in the ECU memory, so if the location is different on different versions of the ECU microcode you might not find what you are looking for.

cmb

65 posts

55 months

[news] 
Monday 16th July 2012 quote quote all
bubblehead said:
Mark my screen has a line for target idle speed but it's empty.....it's a 4.3 precat if that matters but it seems to idle fine at about 1000rpm, just curious why i don't have a target idle speed?
Does the main voltage display correctly? We've found that there is an early revision of the ECU that calculates main voltage and target idle speed a little differently.

If both main voltage and target idle speed are blank/incorrect, my guess is that you have an early ECU (1991?); I'm currently working on a fix for the voltage issue, but the target idle issue requires a lot more investigation and may not be fixed for a while yet.

--Colin

bubblehead

245 posts

73 months

[news] 
Tuesday 17th July 2012 quote quote all
[quote=cmb]

Does the main voltage display correctly? We've found that there is an early revision of the ECU that calculates main voltage and target idle speed a little differently.

Hi Colin the main Voltage does display at 13.7v but i never paid it too much attention to see if it fluctuated or moved when the car was started, will have a look at the weekend. It's a 1992 car so could indeed be the early version you mentioned. Thanks for the input and the work you've put into the software, great stuff.

bubblehead

245 posts

73 months

[news] 
Tuesday 17th July 2012 quote quote all
davep said:
As a fellow pre-cat owner and RoverGuage user I'd be interested to know what the fault and significant problem were. Also what fuel maps your car uses. PM if you prefer.
Dave the fault was of my own making and the fact that i had zero time to properly diagnose before i headed out to Le Mans for it's post body off rebuild shake down trip (not the ideal way to run the engine in i know). The fault was that the car would at various times cut back to idle when the engine reached 2900rpm, not stall, just total loss of power but still idling. As on a previous thread i initially thought it was the TPS and swapped it out with a known good one but still the same snag. My speedo sensor was playing up so disconnected that and thought i had cured it until half way down the M6 it started again. Long story short i fitted a modified plenum from a 420 wedge which meant that although the mounting holes for the TPS were in the same orientation the slot in the throttle spindle was different and hence there was no or negative preload on the TPS. Roverguage showed up a permanent TPS fault although it indicated 8% when shut, i think it was trying to tell me -8% and high air flow with low throttle opening. When opening the throttle and watching the display it went from 8% to 0 to 70% with a huge dead band around zero%, drilling and tapping two new mounting holes in the plenum to reorientate the TPS solved it. A few simple checks with a meter would have identified it (hind sight is great isn't it)although faffing about in the pasenger foot well whilst operating the throttle is a pain, Rover guage made it very simple with the graphic display. Running on map 2 green tune resistor, not sure if the loss of power was it going to the limp home map due to the fault codes or not ?
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davep

537 posts

164 months

[news] 
Wednesday 18th July 2012 quote quote all
Interesting write-up bubble, thanks for that. Hadn't considered the effects of negative throttle pre-load before.

Here's a recent RoverGuage screen capture of my pre-cat at idle, shows throttle preload at 3%:


bubblehead

245 posts

73 months

[news] 
Wednesday 18th July 2012 quote quote all
Dave i see you have no target idle RPM either, must be a precat thing with the early version ECU's scratchchin.

330p4

529 posts

110 months

[news] 
Tuesday 24th July 2012 quote quote all
Where is the plug located on a Griffith 500 is it in the passenger footwell by the ecu
Ian

eliot

5,750 posts

134 months

[news] 
Tuesday 24th July 2012 quote quote all
330p4 said:
Where is the plug located on a Griffith 500 is it in the passenger footwell by the ecu
Ian
Yes that is where it should be.

330p4

529 posts

110 months

[news] 
Wednesday 25th July 2012 quote quote all
Eliot Thanks
Ian

Griffith 500

9 posts

134 months

[news] 
Saturday 28th July 2012 quote quote all
I have had problems with rich running at start up, spitting fuel on the garage wall. When I looked at the Rovergauge I found that the long term compensation was at -100% on both lamdas. No fault codes and all sensors looked OK. I changed the CO voltage on the AFM from 1,8 V to 1,0 V, and now the long term compensation changed to +14 % on one lambda and -26 % on the other. Does this make any sense?

330p4

529 posts

110 months

[news] 
Saturday 28th July 2012 quote quote all
Mark thanks for the lead worked first time
Ian

blitzracing

Original Poster:

3,758 posts

100 months

[news] 
Saturday 28th July 2012 quote quote all
Griffith 500 said:
I have had problems with rich running at start up, spitting fuel on the garage wall. When I looked at the Rovergauge I found that the long term compensation was at -100% on both lamdas. No fault codes and all sensors looked OK. I changed the CO voltage on the AFM from 1,8 V to 1,0 V, and now the long term compensation changed to +14 % on one lambda and -26 % on the other. Does this make any sense?
You may have just solved one of the great riddles of the 14CUX....smilesmilesmile. I have never mangaged to read a shift in the actual lambda cycling when messing around with the CO trim setting, so Ive always concluded this trim makes no difference at all on the cat map- plus I was also told by a 14CUX guru (Not M.A.) that the CO trim circuit was turned off in cat mode, so Ive never doubted this fact. Now with RoverGauge being able to read the long term trim, we can actually see what the ECU is doing to the mixture- NOT whats the lambda probes are reporting post combustion. Its probably why M.A. gives a trim voltage for his chips, but when I asked him why he simply said it was a factory setting confused - and at the time I had no idea that the ECU even had a long term trim facility- (M.A. kept that fact close to his chest) let alone one you could set with CO trim.

This has a lot of potential- as where we have been blindly setting the DC voltage on the CO trim- we could in fact have been mis-setting the long term trim, so the ECU is banging against the limits on the short term trim that can lead to poor low low speed performance (read shunting). We need to try setting up a car that shunts and see if it improves things.

Edited by blitzracing on Saturday 28th July 20:48

TV8

1,537 posts

55 months

[news] 
Saturday 28th July 2012 quote quote all
Griffith 500 said:
I have had problems with rich running at start up, spitting fuel on the garage wall. When I looked at the Rovergauge I found that the long term compensation was at -100% on both lamdas. No fault codes and all sensors looked OK. I changed the CO voltage on the AFM from 1,8 V to 1,0 V, and now the long term compensation changed to +14 % on one lambda and -26 % on the other. Does this make any sense?
Hi, did this sort the richness of the mixture as well please?

Griffith 500

9 posts

134 months

[news] 
Sunday 29th July 2012 quote quote all
TV8 said:
Hi, did this sort the richness of the mixture as well please?
I think so, it takes a couple of minutes before the lamdas are heated and starts to compensate. Before the engine ran very rough, and it was stinking of fuel.

blitzracing

Original Poster:

3,758 posts

100 months

[news] 
Monday 13th August 2012 quote quote all
A bit of help needed here from anyone who has a cable, as I cant get the expected results from my car on the long term fuel trim values. My long term values display correctly just once, and then next time it updates they default to 0, or 255, and then stays that way even without the engine running. Ive not noticed this on any of the TVR's however, so can anyone please just double check two things for me?

1) Please someone just do the same test as TV8 did and see if the long term trim changes with the CO trim on the side of the AFM. The engine must be warm and at idle when you do this and it may take a while to change (no more than 2 mins). Idealy you want to set the long term trim to be as near the mid point (0) as possible, and average out the two banks of the V8.

2) Double check which way the long term trim value changes in relation to the AFM setting- I expect the the trim value to become more +ve as you wind the AFM screw clockwise to richen the mixture. I need to check the Long term trim is the same as the short term trim, that adding fuel trim makes the mixture leaner. Another easy test to do would be to remove the vacuum line from the fuel regulator so it boosts the fuel pressure at idle, this should cause the long term trim to move in a positive direction. You may need to block the hole off in the plenum wheer the pipe was as the extra air will alter the mixture as well.

thanks
Mark

cmb

65 posts

55 months

[news] 
Monday 10th September 2012 quote quote all
Note that the current version of the software (0.3.4) is displaying the short-term lambda fuel trim inverted. Both the long-term and short-term fuel trim values actually should show a higher number with more fuel delivery. We verified that this is the case by using an oscilloscope to monitor the injector pulse width. I hope to soon release a new version with the correct polarity displayed.

I also experimented by writing different values to the long-term trim memory location. (This location was initially at 0 counts with a warm engine at tickover.) Writing the minimum value (-256 counts) caused the engine to stumble and almost die, but the short-term trim values increased substantially to compensate, and the normal idle speed was restored. Conversely, setting the long-term trim to its maximum value (+255 counts) caused a slight increase in engine speed, but this was again corrected by the short-term trim, which decreased substantially.

--Colin

Pink_Floyd

762 posts

101 months

[news] 
Tuesday 11th September 2012 quote quote all
Some thing else that might be usefull to display would be the duty cycle of the injector pulses so that you could see if both banks are the same or, that at tick over that they are low and at full throttle they are 100%. Don't know if this is possible.

900T-R

19,111 posts

137 months

[news] 
Tuesday 11th September 2012 quote quote all
Small point: you don't want the injector duty cycle go over 85-90% for WOT/max power; if they do it's time to uprate the injectors...

blitzracing

Original Poster:

3,758 posts

100 months

[news] 
Tuesday 11th September 2012 quote quote all
You may well hit a stumbling block there as the ECU / CPU runs out of puff at hight RPM, and stops displaying sensor data as its busy controlling the engine.
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