WOT throttle pot reading on a flapper
Discussion
Hi all.
Had my head under the bonnet looking for free horsepower (as you do...). At WOT, I notice the throttle pot voltage between the green and red wires tops out at 4.15v. The blurb Ive got says it should top out at 4.5 volts max.
Does anyone know if the 4.15v Im getting is about right, cos I reckon it might be a bit low? I guess the result could be that the ecu is underfuelling because it thinks Im not flat out when I am?
Any opinions?
Rather not replace it if its working OK - they're a bloody rip-off! Increase in voltage is smooth as throttle is opened, 334mv at idle.
Ta.
Ed.
Had my head under the bonnet looking for free horsepower (as you do...). At WOT, I notice the throttle pot voltage between the green and red wires tops out at 4.15v. The blurb Ive got says it should top out at 4.5 volts max.
Does anyone know if the 4.15v Im getting is about right, cos I reckon it might be a bit low? I guess the result could be that the ecu is underfuelling because it thinks Im not flat out when I am?
Any opinions?
Rather not replace it if its working OK - they're a bloody rip-off! Increase in voltage is smooth as throttle is opened, 334mv at idle.
Ta.
Ed.
Im just investigating a few niggles:
Runs well, compressions are good, revs smoothly and everything is substantially fine. BUT:
Normally requires a little dab of throttle to get it to start cleanly, otherwise it just kicks over, firing half-heartedly.
Misfires a little when started on a cold morning for about 20 seconds. No bigie, but would be nice to sort it.
Not got much grunt above 5kRPM. Drove a mates Chim 400 (I know, I know... But it was only once...), and that was well up for it right up to 6k. The wedge is superb all the way from 2kRPM to 4750RPM though.
Sometimes the idle speed wanders a little, and its difficult to get it to idle well below 1000RPM. This may be down to the cam.
So basically Im trying to get the engine dialled in that last 5%.
Ed.
Runs well, compressions are good, revs smoothly and everything is substantially fine. BUT:
Normally requires a little dab of throttle to get it to start cleanly, otherwise it just kicks over, firing half-heartedly.
Misfires a little when started on a cold morning for about 20 seconds. No bigie, but would be nice to sort it.
Not got much grunt above 5kRPM. Drove a mates Chim 400 (I know, I know... But it was only once...), and that was well up for it right up to 6k. The wedge is superb all the way from 2kRPM to 4750RPM though.
Sometimes the idle speed wanders a little, and its difficult to get it to idle well below 1000RPM. This may be down to the cam.
So basically Im trying to get the engine dialled in that last 5%.
Ed.
Hey Ed,
Free HP...GOOD THINKING!!!
Where should i measure this? I'm assuming that this is tested with just the ignition on, but which wires do you check for the throttle pot? Im clueless at this bit
Also, just to confirm, my car revs the same as yours. My mates chim (400 - not HC) revs freely up to about 6K where i never take mine above 5K as it doesnt seem right and the dyno at BBWF proved that...
Lookin at the plot (and this is going by the jerks in the line and the grid formation showed) it showed 249.9 HP at 4920-4980 RPM and then started tailing off quickly at 5040 RPM until the test stopped at 5160 RPM......
Could it be the Rev counter doesnt read correctly? Or is this cam wear? Mine runs fantastically, although does pink a bit so need to adjust the fueling..
Let me know which wires to test and i'll let you know. As yours is an 89, and mines one of the first 400's, they could have the same engine (not that i would ever expect TVR to do such a thing...obviously!!)
Matt Man
Free HP...GOOD THINKING!!!
Where should i measure this? I'm assuming that this is tested with just the ignition on, but which wires do you check for the throttle pot? Im clueless at this bit
Also, just to confirm, my car revs the same as yours. My mates chim (400 - not HC) revs freely up to about 6K where i never take mine above 5K as it doesnt seem right and the dyno at BBWF proved that...
Lookin at the plot (and this is going by the jerks in the line and the grid formation showed) it showed 249.9 HP at 4920-4980 RPM and then started tailing off quickly at 5040 RPM until the test stopped at 5160 RPM......
Could it be the Rev counter doesnt read correctly? Or is this cam wear? Mine runs fantastically, although does pink a bit so need to adjust the fueling..
Let me know which wires to test and i'll let you know. As yours is an 89, and mines one of the first 400's, they could have the same engine (not that i would ever expect TVR to do such a thing...obviously!!)
Matt Man
TVRleigh_BBWR said:
My 89 Flapper 400SE has good pull all the way to 6K it's been over that a few times also.
I know on some of the hotwire system with an LandRover chip they are not mapped past 5k
With a flapper they don't work on a map as such, so not a problem.
Hey Leigh...I know on some of the hotwire system with an LandRover chip they are not mapped past 5k
With a flapper they don't work on a map as such, so not a problem.
Thats really weired then, my would definatly not got to 6k...not without a lot of nuts and bolts coming from under the bonnet!
matt-man said:
TVRleigh_BBWR said:
My 89 Flapper 400SE has good pull all the way to 6K it's been over that a few times also.
I know on some of the hotwire system with an LandRover chip they are not mapped past 5k
With a flapper they don't work on a map as such, so not a problem.
Hey Leigh...I know on some of the hotwire system with an LandRover chip they are not mapped past 5k
With a flapper they don't work on a map as such, so not a problem.
Thats really weired then, my would definatly not got to 6k...not without a lot of nuts and bolts coming from under the bonnet!
Plus I'm sure they went to 5600 RPM on the dyno. I think it was 236 BHP.
this was done via Mark Adam's after he gave it some tweeks.
Also I Remember another member here who's would rev fine up-to and even past 6K.
ed_crouch said:
My ECU says Landrover on it.
D'you think its the wrong ecu? Perhaps a "well meaning enthusiast" replaced a dead ecu with the wrong one?!?
Be interested to try a loaner ecu if theres one available?? *bats eyelids*
Ed.
Thats pretty random...no idea what mine says, didnt really look...last time i took it out was when i forgot to put it back in the car and couldnt understand why it wouldnt start!! haha!D'you think its the wrong ecu? Perhaps a "well meaning enthusiast" replaced a dead ecu with the wrong one?!?
Be interested to try a loaner ecu if theres one available?? *bats eyelids*
Ed.
Edited by ed_crouch on Friday 16th January 19:13
Well, if you ever come out for a blast, you could have a little borrow of mine and see if it makes a difference..long as you promise to give it back!!
So again, what wires am i testing voltage at??
ed_crouch said:
My ECU says Landrover on it.
D'you think its the wrong ecu? Perhaps a "well meaning enthusiast" replaced a dead ecu with the wrong one?!?
Be interested to try a loaner ecu if theres one available?? *bats eyelids*
Ed.
It wouldn't hurt as such to use a Landrover (Rangerover) ECU insofar as the car would still run but the various resistors that fine-tune the ECU to the rest of the system would be wrong so running may well not be 100%. Of course the car could have had an engine swap for one from a Rangerover and the ECU could have been swapped at the same time; or it may be an ex-Rangerover ECU but all the resistors might have been changed for the correct values (ie copied from the original).D'you think its the wrong ecu? Perhaps a "well meaning enthusiast" replaced a dead ecu with the wrong one?!?
Be interested to try a loaner ecu if theres one available?? *bats eyelids*
Ed.
Unless you know what they should be for a 350i rather than a Rangerover (and there are some on PH who do) then you can't otherwise tell whether it's correct for your engine.
Righty ho.
Get the multimeter, and plug the probes into the throttle pot connector as follows (leaving the throttle pot connected - you have to ease the probes into the back of one end of the connector), with the ignition switched on but the engine stopped:
Yellow and green should give 4.1 to 4.5 volts.
Then take the probe out of the yellow wire, and probe the red wire. Red to green should give 0.325v +/- 0.025v - so 300mv to 350mv with the throttle closed.
If its out of range, slacken the two screws and move it very gently until you get near the middleo f the range. Then tighten the screws back up again.
Now open the throttle slowly to WOT (this is why the engine needs to be stopped!!). The meter reading should smoothly rise to 4.5 volts max. Mine only goes as far as 4.15 volts. I wonder if the ECU thinks Im not at WOT when I am...
This all needs to be done with ignition on, ecu plugged in, engine stopped.
As you open the throttle you will hear the injectors click once. This is normal.
Have fun!
Ed.
P.S. Thanks for your generous offer of the ecu swop for a test - I may need it!!
Get the multimeter, and plug the probes into the throttle pot connector as follows (leaving the throttle pot connected - you have to ease the probes into the back of one end of the connector), with the ignition switched on but the engine stopped:
Yellow and green should give 4.1 to 4.5 volts.
Then take the probe out of the yellow wire, and probe the red wire. Red to green should give 0.325v +/- 0.025v - so 300mv to 350mv with the throttle closed.
If its out of range, slacken the two screws and move it very gently until you get near the middleo f the range. Then tighten the screws back up again.
Now open the throttle slowly to WOT (this is why the engine needs to be stopped!!). The meter reading should smoothly rise to 4.5 volts max. Mine only goes as far as 4.15 volts. I wonder if the ECU thinks Im not at WOT when I am...
This all needs to be done with ignition on, ecu plugged in, engine stopped.
As you open the throttle you will hear the injectors click once. This is normal.
Have fun!
Ed.
P.S. Thanks for your generous offer of the ecu swop for a test - I may need it!!
ed_crouch said:
Update:
Im only getting 4.13V at WOT, and the yellow-green control voltage is 4.37V, i.e. the throttle position signal on the red wire isnt reaching the full voltage even at WOT.
Question is, does that mean the ecu is underfuelling??
Possibly not. The supply to the pot is from a voltage regulator on the ECU that also feeds various comparators etc. in the electronics. As long as that's the reference voltage that the circuit has to work with, then whatever the pot sends back is within the range of the circuit, if you see what I mean. If you jacked the reference up to say 5v, then the pot wiper would send back a proportionally higher voltage too.Im only getting 4.13V at WOT, and the yellow-green control voltage is 4.37V, i.e. the throttle position signal on the red wire isnt reaching the full voltage even at WOT.
Question is, does that mean the ecu is underfuelling??
Next you'll be whipping the ECU lid off to check Vref, to make sure that what the electronics see is what the pot sees, won't you ...
It is sometimes a little jerky when you begin to tickle the gas after pulling away. You let the clutch up, and if you let the car chug along at idle in 1st or 2nd, as you touch the throttle, it jerks quite badly. Ive also heard it referred to as trailer-hitching, and the blurb reckoned it could be a dodgy throttle pot...
'S really not a bad problem, I just want to get it going as well as is possible.
'S really not a bad problem, I just want to get it going as well as is possible.
ed_crouch said:
It is sometimes a little jerky when you begin to tickle the gas after pulling away. You let the clutch up, and if you let the car chug along at idle in 1st or 2nd, as you touch the throttle, it jerks quite badly. Ive also heard it referred to as trailer-hitching, and the blurb reckoned it could be a dodgy throttle pot...
'S really not a bad problem, I just want to get it going as well as is possible.
Try disconnecting the pot, you'll probably find the ECU scarcely notices.'S really not a bad problem, I just want to get it going as well as is possible.
One thing I find is that if you floor it from low speed, the engine takes a big gulp of air that you can hear through the AFM but it then baulks before picking up. You can replicate it with the car stood still. When it does that you can watch the AFM flap swing wide open then back, like an undamped analogue meter movement.
In my experience the RV8 with flapper injection responds better to progressive throttle rather than stamping on it.
ed_crouch said:
Does anyone know if the 4.15v Im getting is about right, cos I reckon it might be a bit low? I guess the result could be that the ecu is underfuelling because it thinks Im not flat out when I am?
4.1 volts is fine. Your acceleration enrichment circuits respond the rapid throttle pot rotation and the full load enrichment circuits are triggered sometime before WOT. The first three pages of the TP pdf here explains the function.http://www.vintagemodelairplane.com/pages/Rover_Te...
Subsequent to that article, this explains that Full Load Enrichment is not a myth, follow the red dot.
Or here if image did not appear. http://www.vintagemodelairplane.com/pages/Photo_Me...
So Rover clearly designed it in, but never published where it occurred. Study of Flapper ECU comparitor circuits now shows full load enrichment circuits are triggered at 3.7 volts. If anyone knows for sure its different, please advise and explain cuz old stuff is being periodically updated.
ed, my 390se is the same year as yours and i have recently done the following after only getting about 200hp at the crank and struggling like hell to pull above 5k.
Changed throttle pot,set to 0.3 at tickover it reads 4.35 at wot.
Changed leads,plugs etc.
Altered ignition timing to 12 BTDC, this adjustment alone completely altered the engine, it was like someone had bolted a new one in overnight without me knowing.But make sure you go no further and always use super unleaded with as higher octane as you can get your hands on.
Set AFM flap to get 2.25% co at tickover.
Fitted F.S.E. boost valve and set to 40psi with ignition on but not running.
It is worth noting that torque does tale off above 5k but the difference up to it is incredible, the main change on my car apart from what feels like twice the power, is the complete removal of a kick in power at around 2.5k, it is now a smooth curve from about 1500 upwards.
Changed throttle pot,set to 0.3 at tickover it reads 4.35 at wot.
Changed leads,plugs etc.
Altered ignition timing to 12 BTDC, this adjustment alone completely altered the engine, it was like someone had bolted a new one in overnight without me knowing.But make sure you go no further and always use super unleaded with as higher octane as you can get your hands on.
Set AFM flap to get 2.25% co at tickover.
Fitted F.S.E. boost valve and set to 40psi with ignition on but not running.
It is worth noting that torque does tale off above 5k but the difference up to it is incredible, the main change on my car apart from what feels like twice the power, is the complete removal of a kick in power at around 2.5k, it is now a smooth curve from about 1500 upwards.
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