Full load enrichment - weak CO reading
Discussion
I've recently had a few things done to the car 
and popped up to Power Engineering at Uxbridge yesterday to get a post work, pre Mark Adams re chip (awaitng extra car funds to become available before that bit 
), set of dyno figures for the car, well that was the intention anyway 
.
Having carried out all the pre checks, the first run CO did not get much above 1%
far too weak a mixture and possibly damaging low levels , I was expecting it to be a bit lean 'post work' but not that lean .
Had the AFM checked, very dirty so it was cleaned and seems OK, the throttle pot checked, yep reaching 4.9V (more latter), put a spare HC chip in no difference, after much checking by Chris using Mervyn as a sounding board, it was decided to call it a day and drive it home on light throttle only, with a view to returning another day when MA is in attendance. Not sure if the funds will run to the rechip at the same time so it will have to just be a diagnostic run with MA this time.
However not being one to sit on my hands I spent half the day crawling all over the car in particular anything to do with the ECU/Injection, I mean I have measured every value of every component in the system they are all OK except...............the throttle pot, whilst a value of 4.9 volts was obtained at Power Eng that was done by moving the throttle spindle by hand, great, but by using the loud peddle from inside the car it will not go above 4.15 Volts, btw at rest it reads 0.52 V.
Question time,
1. As I understand it, at rest, the TP should read 0.36 V (certainly less than 0.5) is 0.52V OK?
2. Full load enrichment as I understand it comes in at 4.6 V, is the figure of 4.15 enough to give the low CO readings on the power run ?
3. To correct the full rnage of the pot, if I move the pot around it will make the idle setting too high ,as its too slightly too high already don't really want to go there....yet. Can a streched throttle cable give these readings ? or do I have to play with and or adjust the cable at the throttle linkage end?
Any advice gratefully recieved.
Harry
and popped up to Power Engineering at Uxbridge yesterday to get a post work, pre Mark Adams re chip (awaitng extra car funds to become available before that bit ), set of dyno figures for the car, well that was the intention anyway . Having carried out all the pre checks, the first run CO did not get much above 1%
far too weak a mixture and possibly damaging low levels , I was expecting it to be a bit lean 'post work' but not that lean . Had the AFM checked, very dirty so it was cleaned and seems OK, the throttle pot checked, yep reaching 4.9V (more latter), put a spare HC chip in no difference, after much checking by Chris using Mervyn as a sounding board, it was decided to call it a day and drive it home on light throttle only
, with a view to returning another day when MA is in attendance. Not sure if the funds will run to the rechip at the same time so it will have to just be a diagnostic run with MA this time. However not being one to sit on my hands I spent half the day crawling all over the car in particular anything to do with the ECU/Injection, I mean I have measured every value of every component in the system they are all OK except...............the throttle pot, whilst a value of 4.9 volts was obtained at Power Eng that was done by moving the throttle spindle by hand, great, but by using the loud peddle from inside the car it will not go above 4.15 Volts
, btw at rest it reads 0.52 V. Question time
, 1. As I understand it, at rest, the TP should read 0.36 V (certainly less than 0.5) is 0.52V OK?
2. Full load enrichment as I understand it comes in at 4.6 V, is the figure of 4.15 enough to give the low CO readings on the power run ?
3. To correct the full rnage of the pot, if I move the pot around it will make the idle setting too high ,as its too slightly too high already don't really want to go there....yet. Can a streched throttle cable give these readings ? or do I have to play with and or adjust the cable at the throttle linkage end?
Any advice gratefully recieved.
Harry
Is the fuel pressure right? Are the injectors all working properly and not clogged or sticking? I think these would be thw first things to check.
Other than that, sounds like you may have a duff throttle pot or at least one that is not adjusted properly. The throttle pot should be adjusted so it reads 0.26 - 0.36 at idle, it should then read 4.6-5.0 volts at full throttle. (These figures from The Bible of course - I assume you have a copy with you.) If you can't get that, perhaps you need a new throttle pot.
Confirm you are getting full travel on the throttle spindle, at idle it should be firmly against the idle stop and at full throttle if you hold the pedal down you shouldn't be able to move the throttle spindle open any further by hand. From the point of view of engine management and emissions etc, you can ignore the pedal/cable. Make sure you are getting full travel on the spindle and that is all that matters.
Hope this helps,
Peter Humphries (and a green V8S)
Edited to add that I understand the hotwire air meters are extremely sensitive to dirt on the hotwire element and I don't know if it is safe/possible to clean them. Probably OK to scrape the much off the inside of the choke, but consider the possibility that the meter is now misreading.
>> Edited by GreenV8S on Saturday 19th April 00:46
Other than that, sounds like you may have a duff throttle pot or at least one that is not adjusted properly. The throttle pot should be adjusted so it reads 0.26 - 0.36 at idle, it should then read 4.6-5.0 volts at full throttle. (These figures from The Bible of course - I assume you have a copy with you.) If you can't get that, perhaps you need a new throttle pot.
Confirm you are getting full travel on the throttle spindle, at idle it should be firmly against the idle stop and at full throttle if you hold the pedal down you shouldn't be able to move the throttle spindle open any further by hand. From the point of view of engine management and emissions etc, you can ignore the pedal/cable. Make sure you are getting full travel on the spindle and that is all that matters.
Hope this helps,
Peter Humphries (and a green V8S)
Edited to add that I understand the hotwire air meters are extremely sensitive to dirt on the hotwire element and I don't know if it is safe/possible to clean them. Probably OK to scrape the much off the inside of the choke, but consider the possibility that the meter is now misreading.
>> Edited by GreenV8S on Saturday 19th April 00:46
Fuel pressures fine, 2 bar idle 2.5 bar with full vac, asumption is injectors are fine as plugs good colour. The peddle travel does not put the throttle spindle on full stops. I'll try setting up the idle voltage first on the throttle pot (elongate the holes) and then see how much I can get on the cable adjuster (back of plenum) tomorrow.
Saying all of that the static reading for the TP was 7K2 ohm, book said it should be 5k ohm but the range of voltage output is what is important to the ECU, so if none of that works I'll get a replacement pot and try again.
My main query was that if the TP output didn't reach the ECU triger point of 4.6V then would the low CO value seen be the result?
Harry
Edited to add the AFM was taken apart and internals cleaned with carb cleaning fluid, Chris from power, at the time was putting his money on the AFM being defective even though the output voltage from that appears to be correct on full load, can't remember exact figure but around the 5V value again.
No 2 fav is the ECU itself. but I'm trying not to go down that road until everthing else is spot on.
>> Edited by HarryW on Saturday 19th April 01:03
Saying all of that the static reading for the TP was 7K2 ohm, book said it should be 5k ohm but the range of voltage output is what is important to the ECU, so if none of that works I'll get a replacement pot and try again.
My main query was that if the TP output didn't reach the ECU triger point of 4.6V then would the low CO value seen be the result?
Harry
Edited to add the AFM was taken apart and internals cleaned with carb cleaning fluid, Chris from power, at the time was putting his money on the AFM being defective even though the output voltage from that appears to be correct on full load, can't remember exact figure but around the 5V value again.
No 2 fav is the ECU itself. but I'm trying not to go down that road until everthing else is spot on.
>> Edited by HarryW on Saturday 19th April 01:03
Harry
I would not do anything until Mark has looked at this. There are internal ECU settings that will set the CO level and enrichment and it is quite possible that as your engine is a real bitsa that the standard HC chip is not set up correctly (and possible never has been!).
You could play with the throttle linkage and see if there is some additional movement available by hand when the pedal is fully down. Also check that there is nothing stopping the throttle going down either. Also check that the butterfly is not gummed up or the spindle is bent causing a problem. It could simply be a duff throttle pot or even a low supply voltage.
Have you had the cam changed as I thought that was duff.
I would not do anything until Mark has looked at this. There are internal ECU settings that will set the CO level and enrichment and it is quite possible that as your engine is a real bitsa that the standard HC chip is not set up correctly (and possible never has been!).
You could play with the throttle linkage and see if there is some additional movement available by hand when the pedal is fully down. Also check that there is nothing stopping the throttle going down either. Also check that the butterfly is not gummed up or the spindle is bent causing a problem. It could simply be a duff throttle pot or even a low supply voltage.
Have you had the cam changed as I thought that was duff.
Steve
New cam in, got rid of the clattering, interestingly the 'bitsa' had previously had a cam change that I can't find the paperwork for. The actual work done previously is not insignificant, fitted was a TVR435RM post 97 type, as it had the front shoulder machined/cast ala latter cams. It must have also had at the same time the latest heads, spring seats and composite gaskets fitted. Looking down the V whilst the cam was out it looks like the bottom end might be fully balanced as well, but didn't want to drop it all just to find out. One bit of good news during the work was a full duplex vernier timing chain set up was present , however the chain was changed as a matter of course though.
I'll see if I can get full range on the TP via the throttle pedal today. Changing the TP if necessary (anyone know the part no, is it a straight rover/lucas part?). I'll book in with MA for a final fettling/diagnostics, the bank are not going to be hapy with me as if I've got MA in I might as well use the time to get a tornado set up for the car.
Whilst the car was apart took the opportunity to change the trumpets and whilst the exhaust Y piece was off the pre cats fell out as well. I asume the MA re chip will sort out the ragged tick over inherent with the new cam profile . I was looking forward to actually getting a set of figures before the MA treatment as a back to back comparasom (sp?), ah well cest la vie.
Harry
New cam in, got rid of the clattering, interestingly the 'bitsa' had previously had a cam change that I can't find the paperwork for
. The actual work done previously is not insignificant, fitted was a TVR435RM post 97 type, as it had the front shoulder machined/cast ala latter cams. It must have also had at the same time the latest heads, spring seats and composite gaskets fitted. Looking down the V whilst the cam was out it looks like the bottom end might be fully balanced as well, but didn't want to drop it all just to find out. One bit of good news during the work was a full duplex vernier timing chain set up was present , however the chain was changed as a matter of course though. I'll see if I can get full range on the TP via the throttle pedal today. Changing the TP if necessary (anyone know the part no, is it a straight rover/lucas part?). I'll book in with MA for a final fettling/diagnostics, the bank are not going to be hapy with me as if I've got MA in I might as well use the time to get a tornado set up for the car
. Whilst the car was apart took the opportunity to change the trumpets and whilst the exhaust Y piece was off the pre cats fell out as well
. I asume the MA re chip will sort out the ragged tick over inherent with the new cam profile . I was looking forward to actually getting a set of figures before the MA treatment as a back to back comparasom (sp?), ah well cest la vie. Harry
I don't know when the ECU changes from 'economy' mode to 'power' mode, but I would expect it to happen at moderate revs and throttle and not to depend on having the throttle absolutely wide open. Also, I don't understand why you aren't getting full throttle. Have you added a throttle stop or something? If the pedal is hitting the floor you must have the cable adjusted to put the pedal a *lot* lower than standard and you will need to adjust the cable to raise the pedal slightly to allow more travel. If you have added a throttle stop the height must be set correctly so it stops the pedal just as the throttle is fully open. Too low and it doesn't prevent you stretching the cable, too high and you don't get full throttle. If the stop is in roughly the right place, you can fine-tune the travel by adjusting the pedal height with the cable adjuster.
I seem to remember in the past Mark Adams said something about the standard map being too lean at the top end and maybe yours is just normal - or maybe I misunderstood/misremembered what he said. In any case you really need to an expert to know whether you have a problem and if so what may be causing it - I think Mark Adams would be your best bet if he has time to talk to you.
I seem to remember in the past Mark Adams said something about the standard map being too lean at the top end and maybe yours is just normal - or maybe I misunderstood/misremembered what he said. In any case you really need to an expert to know whether you have a problem and if so what may be causing it - I think Mark Adams would be your best bet if he has time to talk to you.
Your right Peter, I've drawn stumps on it now. I've adjusted the cable to give full opening of the butterfly, which it wasn't before but I think the TP is on its last legs as the readings are inconsistant.
The reason I was originally concerned was that with full pedal travel (into the carpet) the TP wasn't going over 4.15V, there was an open letter by John Ravenscroft (Sprint april 97) stated that TVR chips do not give full load enrichment until 4.6V (3.6V for 4.3's and above) giving a 5-10 % under-fueling , i.e it never 'climbs the map'. I just wondered if that was the problem I was experiencing on Thursday as a reading of around 1% CO is an economy figure normally asociated with gebtle acceleration/cruising, not full load foot to the floor stuff .
As for a modified throttle stop, as far as I'm aware i don't have anything but a standard arrangement in the car, I think it was just the cable that was incorrectly adjusted.
I haven't phoned Mark yet as it's bank holiday weekend. I checked with Power when MA has his next block booking and unfortunately I'm on a residential course for work at the time, so the earliest I think I can get the car in is the first week in May , I'll give him a ring on Tuesday to discuss (unless you're reading Mark ?).
Thanks for the input.
Harry
PS OK then, as the TP is giving inconsistant outputs anyone hazard a guess as to a price, I take it is a standard RR 4.0ltr classic part?
The reason I was originally concerned was that with full pedal travel (into the carpet
) the TP wasn't going over 4.15V, there was an open letter by John Ravenscroft (Sprint april 97) stated that TVR chips do not give full load enrichment until 4.6V (3.6V for 4.3's and above) giving a 5-10 % under-fueling , i.e it never 'climbs the map'. I just wondered if that was the problem I was experiencing on Thursday as a reading of around 1% CO is an economy figure normally asociated with gebtle acceleration/cruising, not full load foot to the floor stuff . As for a modified throttle stop, as far as I'm aware i don't have anything but a standard arrangement in the car, I think it was just the cable that was incorrectly adjusted.
I haven't phoned Mark yet as it's bank holiday weekend
. I checked with Power when MA has his next block booking and unfortunately I'm on a residential course for work at the time, so the earliest I think I can get the car in is the first week in May , I'll give him a ring on Tuesday to discuss (unless you're reading Mark ?). Thanks for the input.
Harry
PS OK then, as the TP is giving inconsistant outputs anyone hazard a guess as to a price, I take it is a standard RR 4.0ltr classic part?
er 2.5 bar isn't enough surely? .. that's only 36 psi - AFAIK it's the same rgulator as the cerbie and that runs 47-52 psi on all the ones I've tested ... fit an adjustable regulator and trim it to 52 psi, that's where I'd start after getting that throttle pot sorted (0.325v with engine running at idle).
Jools AFAIK the lucas 14cux efi runs ok at 2.5 bar 2.7 is about tops, I can't comment on the cerbie set up at 52 psi, thats 3.6 bar 
.
The TP is shagged tho, with throttle closed it started at 0.52V as the lowest I could get it, sometimes 0.8v or 1.4v, took it off the spindle it won't physically read below 0.52v and and is not linear in it's output . I'll pick up a replacement tomorrow from a landie dealer.
The throttle movement was not right either I've adjusted the cable and the throttle linkages to give full range on the butterfly so hopefully with a new TP all should be better.
I'll still get MA in though as with the mods I'm not sure the HC mapping of the chip will provide enough fuel, he can run a full diagnostic on the ECU etc that I can only stab at, I only hope there's not too much else wrong, as a 4 seater with 52 psi fuel would have been cheaper to run.
Harry
. The TP is shagged tho, with throttle closed it started at 0.52V as the lowest I could get it, sometimes 0.8v or 1.4v
, took it off the spindle it won't physically read below 0.52v and and is not linear in it's output . I'll pick up a replacement tomorrow from a landie dealer. The throttle movement was not right either I've adjusted the cable and the throttle linkages to give full range on the butterfly so hopefully with a new TP all should be better.
I'll still get MA in though as with the mods I'm not sure the HC mapping of the chip will provide enough fuel, he can run a full diagnostic on the ECU etc that I can only stab at, I only hope there's not too much else wrong, as a 4 seater with 52 psi fuel would have been cheaper to run
. Harry
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