Flat spots ... help
Discussion
Engine seems to have developed some flat spots and may be running warmer than usual ... anyone got any ideas? Seems to be determined by engine speed. For example, if I accelerate in 3rd gear with about 60% constant throttle from about 1500rpm, the acceleration seems to falter at 2000rpm and somewhere around 3200. Power seems to tail off more quickly than before around 5000rpm.
The symptoms are marginal, so it could be down to paranoia. Otherwise wondering if ECU is getting duff data. Throttle pot often seems to be a culprit, but because I've been pretty much keeping it in one place, maybe less likely this time?
The symptoms are marginal, so it could be down to paranoia. Otherwise wondering if ECU is getting duff data. Throttle pot often seems to be a culprit, but because I've been pretty much keeping it in one place, maybe less likely this time?
quote:
Engine seems to have developed some flat spots and may be running warmer than usual ... anyone got any ideas? Seems to be determined by engine speed. For example, if I accelerate in 3rd gear with about 60% constant throttle from about 1500rpm, the acceleration seems to falter at 2000rpm and somewhere around 3200. Power seems to tail off more quickly than before around 5000rpm.
The symptoms are marginal, so it could be down to paranoia. Otherwise wondering if ECU is getting duff data. Throttle pot often seems to be a culprit, but because I've been pretty much keeping it in one place, maybe less likely this time?
Depending on mileage, you might consider getting checking the state of the cam. Also check for ECU fault codes, and see if resetting the ECU helps (temporarily).
quote:
Engine seems to have developed some flat spots and may be running warmer than usual ... anyone got any ideas? Seems to be determined by engine speed. For example, if I accelerate in 3rd gear with about 60% constant throttle from about 1500rpm, the acceleration seems to falter at 2000rpm and somewhere around 3200. Power seems to tail off more quickly than before around 5000rpm.
The symptoms are marginal, so it could be down to paranoia. Otherwise wondering if ECU is getting duff data. Throttle pot often seems to be a culprit, but because I've been pretty much keeping it in one place, maybe less likely this time?
Sorry to upset you, but who taught you to drive? Accelerating in third gear from 1500rmp? What about being in the right gear at the right rmp for a given situation thereby allowing you to be able to accelerate out of any dangerous situations. I always use a minimum of 2500rmp before I think about accelerating away, that way I'm in the torque curve of the engine. I know that TVRs have loads of low down torque, but that doesn't mean that you have to labour the engine at low revs and then use 60% throttle. You might find that the car will run smoother if you drop down one gear, ie be in second instead of third. This will also give you the added benifit of balancing the car better around corners - if you don't know what I mean try going around a roundabout in fifth and then do the same in the lower gears - you'll have more control over what the car is doing.
Again - sorry for having a go and I know it won't fix your flat spots, but once you've sorted that out you'll find more enjoyment out of your driving.
Ian - Police Class 1 driver
It's a bl00dy V8 of course it should be smooth and progressive from 1500rpm - give the guy a break.
I would start by checking the electrics. Have you ever replaced the HT leads/Dizzy cap/Plg shroud extender thingys? Reset the ECU too just in case (since it's so easy to do - unplug for a minute or two). Then check the steppper motor and the other things you suggest. RPIs website has instructions on how to set up the air flow meter and the throttle pot.
Could be the cam though ... but there are a 100 things to check first. Don't panic. (My cam went at 29k and the symptoms were stalling and no top-end power.)
I would start by checking the electrics. Have you ever replaced the HT leads/Dizzy cap/Plg shroud extender thingys? Reset the ECU too just in case (since it's so easy to do - unplug for a minute or two). Then check the steppper motor and the other things you suggest. RPIs website has instructions on how to set up the air flow meter and the throttle pot.
Could be the cam though ... but there are a 100 things to check first. Don't panic. (My cam went at 29k and the symptoms were stalling and no top-end power.)
quote:
Again - sorry for having a go and I know it won't fix your flat spots, but once you've sorted that out you'll find more enjoyment out of your driving.
Ian - Police Class 1 driver
How helpful. I'm sure it's irrelevant arrogance like that which puts people off doing further training. Go assuage your insecurity elsewhere by patronising somebody without a problem. If my engine had a flat spot where it shouldn't, I'd rather it were fixed than drive around it. Does this mean you start from standstill with a minimum of 2.5k revs in first?
dannylt - You took the words right out of my mouth.
Perhaps Ian -Police Class 1 Driver (gosh I'm really impressed) can explain to the technically minded amongst us what exactly the rmp he refers to is all about. Perhaps the large dial situated in the locus of his speedo has had the lettering interfered with by a person or persons unknown.
Perhaps Ian -Police Class 1 Driver (gosh I'm really impressed) can explain to the technically minded amongst us what exactly the rmp he refers to is all about. Perhaps the large dial situated in the locus of his speedo has had the lettering interfered with by a person or persons unknown.
Perhaps he couldnt read it properly cos of his large ego getting in the way. - Phil, class 1 getaway driver
I would take it to your dealer and get them to check all your ECU readouts could be something simple and shouldnt cost anymore than 50 quid for them to make sure if all is well.
>> Edited by zippy500 on Monday 27th May 08:01
I would take it to your dealer and get them to check all your ECU readouts could be something simple and shouldnt cost anymore than 50 quid for them to make sure if all is well.
>> Edited by zippy500 on Monday 27th May 08:01
I wonder why it should be running hotter too?
I'd agree, take it to an expert to check it out. While it may be the electrics/electronics, it could be mechanical too. It is just possible that you may have a cylinder head gasket starting to leak, which will affect performance and raise the temperature of the water. That would need fixing pdq.
Good luck
R
>> Edited by yum on Monday 27th May 09:10
I'd agree, take it to an expert to check it out. While it may be the electrics/electronics, it could be mechanical too. It is just possible that you may have a cylinder head gasket starting to leak, which will affect performance and raise the temperature of the water. That would need fixing pdq.
Good luck
R
>> Edited by yum on Monday 27th May 09:10
Thanks gents (with special thanks to Top Gun Ian for his comedy interlude) ... the plot thickens ... I ran it up to Cambridge on Friday night and it was pulling smoothly as if nothing had ever been wrong, but on the journey back having behaved itself perfectly, I stopped to refuel (topping up with more Optimax ... didn't accidently fill up with diesel like my mother did once) and it became very lumpy as soon as I restarted the engine. 20 miles down the M11 and round the North Circular in stop-start traffic (congrats to the "face lift" Audi 80 rice mobile that met its maker and the central reservation armco)... and it was running smoothly again (confirmed by blasting up through the cutting onto the top of the hill at Hampstead
).
I assume an intermittent fault tends to point towards electrics rather than mechanical problems, and the weather has been pants during this period so water may be playing a part in the problem.
). I assume an intermittent fault tends to point towards electrics rather than mechanical problems, and the weather has been pants during this period so water may be playing a part in the problem.
quote:
quote:
Again - sorry for having a go and I know it won't fix your flat spots, but once you've sorted that out you'll find more enjoyment out of your driving.
Ian - Police Class 1 driver
How helpful. I'm sure it's irrelevant arrogance like that which puts people off doing further training. Go assuage your insecurity elsewhere by patronising somebody without a problem. If my engine had a flat spot where it shouldn't, I'd rather it were fixed than drive around it. Does this mean you start from standstill with a minimum of 2.5k revs in first?
Danny - it's neither irrelevant arrogance or insecurity, just that to get the best out of any vehicle you need to drive it properly and not labouring the engine trying to accelerate - yes the 500 will quite easily accelerate from standstill in third gear, but it's not feasable to do it everytime. As for being unhelpful, I think you missed the point I was trying to make - once you've got the flat spot sorted out go and take advanced driving lessons to get the best out of the car.
I would give lessons myself, but I'm not qualified as an instructor - I left before I took the instructors exam. As for my arrogance, etc my apologies if it came across that way - it wasn't ment to sound like that and I'm big enough to say sorry if you took it that way.
sybaseian ... look, perhaps I should have explained what I was doing more carefully for your benefit ...
Funnily enough, I don't normally drive like that ... I was "trouble shooting"! The idea is, you try to control which variables are being altered and hold everything else constant and then you look at the results!
If you find that one variable seems to have a big effect on the problem, then you have extracted some useful information about it.
The driving scenario I described was the one that I found showed the problem most clearly, i.e. keep as much constant as possible, except the engine speed and, lo and behold, the flat spots seem to come at certain points in the rev range, independent of throttle position and repeatably. It has nothing to do with my normal driving technique (which sadly involves 1st and 2nd on the North Circular).
Funnily enough, I don't normally drive like that ... I was "trouble shooting"! The idea is, you try to control which variables are being altered and hold everything else constant and then you look at the results!
If you find that one variable seems to have a big effect on the problem, then you have extracted some useful information about it.
The driving scenario I described was the one that I found showed the problem most clearly, i.e. keep as much constant as possible, except the engine speed and, lo and behold, the flat spots seem to come at certain points in the rev range, independent of throttle position and repeatably. It has nothing to do with my normal driving technique (which sadly involves 1st and 2nd on the North Circular).
quote:
dannylt - You took the words right out of my mouth.
Perhaps Ian -Police Class 1 Driver (gosh I'm really impressed) can explain to the technically minded amongst us what exactly the rmp he refers to is all about. Perhaps the large dial situated in the locus of his speedo has had the lettering interfered with by a person or persons unknown.
David as you probably race looking at your profile, you should understand what I meant about being in the right gear/rmp for a given situation - ie you have more control over the balance of the car if you have matched the rmp/gear/speed for a corner. Thus enabling you to apply/correct understeer/oversteer.
quote:
sybaseian ... look, perhaps I should have explained what I was doing more carefully for your benefit ...
Funnily enough, I don't normally drive like that ... I was "trouble shooting"! The idea is, you try to control which variables are being altered and hold everything else constant and then you look at the results!
If you find that one variable seems to have a big effect on the problem, then you have extracted some useful information about it.
The driving scenario I described was the one that I found showed the problem most clearly, i.e. keep as much constant as possible, except the engine speed and, lo and behold, the flat spots seem to come at certain points in the rev range, independent of throttle position and repeatably. It has nothing to do with my normal driving technique (which sadly involves 1st and 2nd on the North Circular).
Alistair, glad to hear that it's not your normal driving technique - where abouts in London are you? Do you fancy turning up for our run out on 1st June - we're meeting up at McDonalds near Junc 7 of M11 at 1pm.
quote:That's a bit presumptuous - what makes you think I don't have equivalent training!? I'm not arguing with what you said per se, it was the context, and the way it came across!
Danny, are you going to the next City meet? I'll take you for a spin and show you what I mean about being in the right gear/rpm.
quote:
quote:That's a bit presumptuous - what makes you think I don't have equivalent training!? I'm not arguing with what you said per se, it was the context, and the way it came across!
Danny, are you going to the next City meet? I'll take you for a spin and show you what I mean about being in the right gear/rpm.
Danny - it was a friendly offer
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