Throttle Pot

[jimed]

I've had the Griff (500 serp) for 3/4 weeks now and really enjoying it. It was serviced last week and as it was idling roughly (and was worse when cold)I'd asked them to have a quick look at it - result was the throttle pot was set incorrectly and whilst they hadn't managed to set it absolutely right it was very close and end result is it is ticking over and running very nicely (also probably using less fuel as well as it was overfuelling quite badly apparently). Anyway whilst it is fine the recommendation was that I think about a new throttle pot in the not too distant future so question is - does the TP just fit on & plug in or does it have to be adjusted to set it correctly and which is the right one for the 500 Serp engine? (I've seen them on TVR Car Parts and Clevor Trevor for what I think is silly money for what is probably also used on Range Rovers - or is it?? Any thoughts appreciated!
Jim

[clive f]

yes they do have to be set correctly, very simple to fit, but need to be set up with the correct voltage reading I think from memory.

how much is silly money??

[jimed]

Hi Clive - the ones I've seen may not be the right ones for the serp engine but are listed as being for the Griff and are well over £100 - clever trevor has an E0206 for pre-serp at £127 and TVR Car parts has what is apparently for the serp engine at a mere £160(!!) and Racing Green has an E0467 which is also for the serp engine apparently at a mere £115 - Phew - surely they aren't that expensive - OK I can understand that maybe some aftermarket ones may not be that good and should be avoided but that sounds silly.
Jim

[blitzracing]

Dont get hoodwinked, the TP is just a plain variable resistor, and really the only thing to go wrong is the track wears, so the varaible voltage it produces is not smooth. This can be simply tested by measuring the output voltage with a test meter as you open and close the throttle. I dont see how it would overfuel the engine. The ECU does have quite wide tollerances for the throttle pot setting voltage, but on post 1992 engines the adjustment feature was removed, as it was simply elongated holes that allowed you to twist the pot to set its volatge with the throttle shut. You can file longer holes on the later pots if you want to tweek the voltage. Mark Adams is very specific about this voltage, and I can only assume its more critical in the TVR fuel maps, than the origional Range Rover set up that seemed to cope with the wider voltage range.

Heres the set up voltages

http://www.v8engines.com/carbs-2.htm#setting-up

[blitzracing]

Dont get hoodwinked, the TP is just a plain variable resistor, and really the only thing to go wrong is the track wears, so the varaible voltage it produces is not smooth. This can be simply tested by measuring the output voltage with a test meter as you open and close the throttle. I dont see how it would overfuel the engine. The ECU does have quite wide tollerances for the throttle pot setting voltage, but on post 1992 engines the adjustment feature was removed, as it was simply elongated holes that allowed you to twist the pot to set its volatge with the throttle shut. You can file longer holes on the later pots if you want to tweek the voltage. Mark Adams is very specific about this voltage, and I can only assume its more critical in the TVR fuel maps, than the origional Range Rover set up that seemed to cope with the wider voltage range.

Heres the set up voltages

http://www.v8engines.com/carbs-2.htm#setting-up

[clive f]

jimed said:

Hi Clive - the ones I've seen may not be the right ones for the serp engine but are listed as being for the Griff and are well over £100 - clever trevor has an E0206 for pre-serp at £127 and TVR Car parts has what is apparently for the serp engine at a mere £160(!!) and Racing Green has an E0467 which is also for the serp engine apparently at a mere £115 - Phew - surely they aren't that expensive - OK I can understand that maybe some aftermarket ones may not be that good and should be avoided but that sounds silly.
Jim

I bet they are manufactured in asia for 50p each!!!

try Blitz`s method and test it.

tell you what, I`m sure I`ve got one in the garage, you can have it for a pint at next years growl.

[jimed]

Cheers Clive- I'll take you up on the offer!
Jim

[Meatball]

These any good?

http://cgi.ebay.co.uk/TVR-CHIMAERA-GRIFFITH-THROTT...
or
http://cgi.ebay.co.uk/Land-Rover-Disco-1-V8-thrott...

Edited by Meatball on Tuesday 15th December 15:10

[jimed]

The ebay adverts don't say which TP they are but look at the price of the Land Rover one at the bottom!
I'll have a go at the adjustment as per the link above - I take it the serp and pre-serp is the same ecu, etc. and therefore the same adjustment??
Jim

[clive f]

jimed said:

Cheers Clive- I'll take you up on the offer!
Jim

pm me your address mate and will ask the other half to put it in the post tomorrow.

just looked at the ones on the linky, has yours got the same plug on the end? mine is 3 pin, but rectangular not round like those ones.

Edited by clive f on Tuesday 15th December 18:23

[jimed]

I suspect the round plug as per the ebay ones is for the pre-serp so mine should be the other plug but I'll make sure and check it tomorrow Clive. Once I've done that I'll let you have the details in a PM. In the meantime thanks for the above it is appreciated!
Jim
Later - I've just been and had a look - a PM is on its way Clive.

Edited by jimed on Tuesday 15th December 20:04

[pwd95]

Just keep your eye open on ebay. Had one for my old Wedge for £20. Easy to set up with a multimeter. Sorted my missfire out. There are a few different types & they look alike so make sure you get the right part number.

[jimed]

Given that I need to set it up when it is connected and with the ignition on what is the process to actually read the voltage? Do I stick some pins in the wires/down the connector or what - I'm sure its easy to do but just getting the means to connect (without risking shorting it out as well) is key so any thoughts/advice?
Jim

[blitzracing]

You do need to push your test meter down the back of the connector to make contact. There are basically 3 wires, +5v, ground and output. Even if you get the test pins in the wrong holes it wont do any damage, just an odd reading. The basic idea is the output would go from 0 volts to 5 volts through the entire movement of the throttle pot if you removed it, but when its fitted to the plenum, the movement is restricted slightly, so it not longer starts at 0 volts, but a bit above it. This is why you twist the body of the pot a bit on its elongated holes to reach this "throttle shut" value. Like wise you need to make sure you reach the peak voltage when the throttle is wide open (it has been known for a lower voltage, which means you wont get full power!) The lower setting is of .29v to .36v at throttle shut, to 4.6v to 5 volts throttle wide open. You will see from the RPI site the preffered setting is mid way between these points.

[jimed]

Thanks for that Mark.
Jim

[2Munkys]

pwd95 said:

[Throttle Pot] Sorted my missfire out.

That's interesting. Wonder if that could be the source of my inconsistent hesitation when flooring it. Wotcha reckon?

[jimed]

It may not be relevant but I had a hesitation issue on the S some time ago and it was down to the timing but you never know as throttle pots can get wear inconsistencies which can cause electrical spikes/interference (or so I was told by an "expert" (?) when I had a problem with the S and checking with a meter to see if it was wiping the resistance correctly showed all was apparently OK but it wasn't as a new TP was the answer) which are hard to find with the usual static tests but can cause problems!
Jim

[Del 203]

My wires are Brown, Green & Blue


I'm getting some very strange reading Yes, i know its probably all to do with my electrical skills

Throttle closed
Green 4.65v

Throttle open
Green .57v

Am i going made ? Surely this is the wrong way round !!

Blue is 4.87v


I will also add, anyone testing, press the immobiliser button rather than wondering for 1/2hr why you cant get any readings

[blitzracing]

I expect you have one pin on the 5 volts when it should be Ov, so the reading will be reversed.

[Del 203]

blitzracing said:

I expect you have one pin on the 5 volts when it should be Ov, so the reading will be reversed.

Oooops


.23 to 4.47 across the green & blue Should i adjust it up a little ? will it make any bhp difference ?