Throttle delay
Discussion
Hullo,
Ever since I bought the V8S there's been a noticeable delay between pressing the accelerator and the engine revs rising, perhaps a quarter to half of a second, particularly when cold. Ok, it could very well not be as much as I am no expert on the passage of time.
I don't notice it as much when driving about but when stationary and I blip the throttle (like you do) I get a feeling that it shouldn't really be like that. It just seems to lag behind what I'm doing, and any spirited acceleration can be undone during gearshifts.
Can you tell me if this delay is pretty normal. I'm comparing it with my brother's 350i which, while older and a different model entirely, surely shouldn't be more direct in the feel of the throttle? From a driveability standpoint I mean. I also drive a 1992 Honda and when I blip the throttle, the engine reacts almost instantly. Smaller engine and less metal to move around, but surely it should not be so great a difference?
The throttle cable seems fine. The bible doesn't mention throttle delays as far as I can see. I don't really know where to start. I thought maybe it's a fuelling problem - sticky doodad or gizmo or iffy pressures.
Any help much appreciated. It doesn't make the car undriveable but I'd like to clear up whether this is a TADTS or something that, once sorted, would make driving even more pleasurable.
Ever since I bought the V8S there's been a noticeable delay between pressing the accelerator and the engine revs rising, perhaps a quarter to half of a second, particularly when cold. Ok, it could very well not be as much as I am no expert on the passage of time.
I don't notice it as much when driving about but when stationary and I blip the throttle (like you do) I get a feeling that it shouldn't really be like that. It just seems to lag behind what I'm doing, and any spirited acceleration can be undone during gearshifts.
Can you tell me if this delay is pretty normal. I'm comparing it with my brother's 350i which, while older and a different model entirely, surely shouldn't be more direct in the feel of the throttle? From a driveability standpoint I mean. I also drive a 1992 Honda and when I blip the throttle, the engine reacts almost instantly. Smaller engine and less metal to move around, but surely it should not be so great a difference?
The throttle cable seems fine. The bible doesn't mention throttle delays as far as I can see. I don't really know where to start. I thought maybe it's a fuelling problem - sticky doodad or gizmo or iffy pressures.
Any help much appreciated. It doesn't make the car undriveable but I'd like to clear up whether this is a TADTS or something that, once sorted, would make driving even more pleasurable.
Mine has done that when cold, when the fuel pressure was set too high. It will also do it when the throttle pot is faulty or not connected. Normally, the engine should start responding to the throttle instantly, even if the revs pick up relatively slowly compared to some more highly tuned engines.
Obviously I will be checking the Bible when I get home but is there any way of checking the throttle pot is not causing the symptoms, without swapping it for a new one?
PS. What is a throttle pot in layman's terms?
And how might I check fuel pressure. Doesn't sound like a job I could do safely.
PS. What is a throttle pot in layman's terms?
And how might I check fuel pressure. Doesn't sound like a job I could do safely.
GreenV8S said:
PS. What is a throttle pot in layman's terms?
Full name throttle potentiometer, its a variable resister (aka potentiometer) connected to the throttle spindle. Just like the volume control on your HiFi, except not as reliable.
Which is basically a variable resistor that sends a variable voltage (signal) to the ECU to tell it how far you have your foot pressed down on the throttle. The ECU then varies the fuel/air ratio accordingly.
All very good when it works
Don't remember this one GI. Maybe that'd be a good excuse for my 'slightly off pace' times on the 1st Lotus day - bridgdav! 
Ok, bit of an odd piccie, but for illustration purposes it'll do.
Throttle pot can be seen bottom right... small black thing with wire attached.
I think there's an item in 'The Bible' about testing the throttle pot.
Not sure about testing fuel pressure regulator?
Ok, bit of an odd piccie, but for illustration purposes it'll do.
Throttle pot can be seen bottom right... small black thing with wire attached.
I think there's an item in 'The Bible' about testing the throttle pot.
Not sure about testing fuel pressure regulator?
My V8S is exactly the same. It is a bit slow to pick up revs when cold, but only from idle. The ECU tells the engine to run very rich when cold, which has always been my threory for it bogging down slightly. No problem when cold, although the RV8 has the feel of an engine with a much larger fly wheel compared to some modern cars.
Z
Z
KentishS2,
Thanks for further elucidation. Muchly helpful for this layman.
PStruck,
You're still around then, mate. You'll be pleased or frustrated to know that he / she is being well looked after. Been experimenting with waxes lately. Need to sort out the mechanical side of things - re: stopping the thing rusting away through the winter - very soon. Have ordered some Ferkin or Fartin or something like that - rust proofer in a tub. Paint on stuff.
I seem to be the only one here that hasn't spent twice the purchase price on mods, niggles and cosmetic niceties. No problems encountered at all so far (apart from the throttle and it might not be a problem at all judging by what these other lads are saying). You were a damn fool to sell him / her / it!
Piccy very useful, ta, and I shall be trying to work out when exactly I notice the delay in the next couple of days.
Stationary it doesn't really bother me, but when I give it beans changing up through the gears, there's the feeling of abnormal delay between planting my foot back on the accelerator and the car beginning to respond. A couple of passengers have commented also, and of course, they can't see my feet.
Z_chromozone,
I do notice it more when I first start it up at idle (at which it is most unresponsive), but there seems to be something lagging behind as well when it's warmed up and I'm 'making progress', albeit in my amateurish cowardlike way. Is this the fabled 'flywheel effect' ?
Besides the fact the car has a TVR badge on it (and thus fulfils my long-held dream) and has the right noise, I have no detailed knowledge of how engines do what they do - other than you squirt fuel, it goes bang, flings metal around inside a big lump of more metal and the car is propelled forward. Ok, I know a bit more but talk of throttle pots, ECU mapping and valvetrains fills me with mock terror. I may have made up 'valvetrains' - I can't be sure.
But this is no place to discuss all that shit.
I just thought with all the bits and pieces that UKBob seems to need to fix with money he has conjured up from somewhere other than his 'TVR purchase fund', maybe I had a wonky sprocket or squirty big end that needed a mop and bucket and not a little counselling.
Thanks for further elucidation. Muchly helpful for this layman.
PStruck,
You're still around then, mate. You'll be pleased or frustrated to know that he / she is being well looked after. Been experimenting with waxes lately. Need to sort out the mechanical side of things - re: stopping the thing rusting away through the winter - very soon. Have ordered some Ferkin or Fartin or something like that - rust proofer in a tub. Paint on stuff.
I seem to be the only one here that hasn't spent twice the purchase price on mods, niggles and cosmetic niceties. No problems encountered at all so far (apart from the throttle and it might not be a problem at all judging by what these other lads are saying). You were a damn fool to sell him / her / it!
Piccy very useful, ta, and I shall be trying to work out when exactly I notice the delay in the next couple of days.
Stationary it doesn't really bother me, but when I give it beans changing up through the gears, there's the feeling of abnormal delay between planting my foot back on the accelerator and the car beginning to respond. A couple of passengers have commented also, and of course, they can't see my feet.
Z_chromozone,
I do notice it more when I first start it up at idle (at which it is most unresponsive), but there seems to be something lagging behind as well when it's warmed up and I'm 'making progress', albeit in my amateurish cowardlike way. Is this the fabled 'flywheel effect' ?
Besides the fact the car has a TVR badge on it (and thus fulfils my long-held dream) and has the right noise, I have no detailed knowledge of how engines do what they do - other than you squirt fuel, it goes bang, flings metal around inside a big lump of more metal and the car is propelled forward. Ok, I know a bit more but talk of throttle pots, ECU mapping and valvetrains fills me with mock terror. I may have made up 'valvetrains' - I can't be sure.
But this is no place to discuss all that shit.
I just thought with all the bits and pieces that UKBob seems to need to fix with money he has conjured up from somewhere other than his 'TVR purchase fund', maybe I had a wonky sprocket or squirty big end that needed a mop and bucket and not a little counselling.
It is very hard to explain exactly when it comes to feel, noises etc (as I well know).
The flywheel effect on the RV8 is very subtle. I try to use extremes when explaining things like this. F1 cars have very small flywheels listen to them on the grid at the start of the race, the revs rise and fall very quickly as they stab the throttle (like pushing a small child on a roundabout). Larger flywheels are found on engines used in the luxury car market, they iron out quick changes in revs to give a smoother ride (listen to a RR revving). However, the increase in revs should happen immediately, but will take a longer period of time. (Think, pushing fat kid on a roundabout).
If you have a delay like I described when my car was cold, but when yours is hot, you definitely have a problem other than the flywheel effect. As I said the rev change should be instantaneous when warm.
I hope I clarified rather than muddied the waters,
Z
The flywheel effect on the RV8 is very subtle. I try to use extremes when explaining things like this. F1 cars have very small flywheels listen to them on the grid at the start of the race, the revs rise and fall very quickly as they stab the throttle (like pushing a small child on a roundabout). Larger flywheels are found on engines used in the luxury car market, they iron out quick changes in revs to give a smoother ride (listen to a RR revving). However, the increase in revs should happen immediately, but will take a longer period of time. (Think, pushing fat kid on a roundabout).
If you have a delay like I described when my car was cold, but when yours is hot, you definitely have a problem other than the flywheel effect. As I said the rev change should be instantaneous when warm.
I hope I clarified rather than muddied the waters,
Z
GI said:
Hullo,
Ever since I bought the V8S there's been a noticeable delay between pressing the accelerator and the engine revs rising, perhaps a quarter to half of a second, particularly when cold.
Press it 1/4 - 1/2 a second sooner than you need to then.
Sorry!
This does sound like you have a problem with the pot, I have a V8s and have not noticed any delay on mine.
GI said:
I had the car inspected by Peninsula before I bought it from Pete - would they have checked the throttle pot and other such bits and bobs?
The car had a remarkably clean bill of health - Justin (I think it was) told me the things he'd noticed were extremely minor niggles.
GI
Like any electrical item, the TP can go at any time without warning and even if checked one day, could fail the next.
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