AJP throttle linkage heat expansion?

[vroom]

Was having another play recently in attempt to set the throttles up on my 4.5.

However, one thing I have noticed is that the throttles drift noticeably when the engine gets hot, to an extent where they are a good few % out of each other, despite being perfect at cold

I am seeing an increase in the even bank and an equivalent reduction on the odd bank (or so it appears).

I have noticed the slight hesitation on part throttle is only apparent when the engine is hot, so I have tried to re-calibrate everything when the engine is hot (adaptives around +/- 5%).

The engine runs great like this but the engine is slightly lumpy until really warm

I guess this a known 'characteristic', and was wondering if an alternative linkage(rod) is available which has less expansion?

I remember Joolz talking about this years ago...but it's a distant memory now.



Any ideas / views on this?

Cheers

Edited by vroom on Monday 13th September 23:40

[RichV6]

Have had similar during a hot european trip, though may have also
adjusted the shape of the linkage on track due to lots of full throttle.
Found the offside bank butterflies were almost completely shut until
the engine bay was hot. My throttle cable now goes to the nearside bank
thanks to Joolz, and I live with slightly slow running until everything warms up

[vroom]

Was thinking of replacing the link rod with a fibre-glass rod or similar. Basically, something with lower coefficient of expansion (or whatever!).

Don't laugh, but I have an old 6' glass fishing rod which I was considering cutting to length and tapping to accept the adjusters.

Only prob is that it is green (but you cant see it behind the scuttle)!

Stupid or a sensible idea???

[a1rak]

I had this on mine, i disconnected the linkage and the throttle pots still wondered from hot to cold and from bank to bank by a few degrees meaning it was not just the link rod that was causing the problems (if at all). I think the complete system sufffers from the heat, including the manifolds spindles and throttle pots.

[ridds]

I set mine up once it's all stinking hot and it seems to cure the bulk of it. I'm not bothered about how it is when cold as I never really let it idle when cold.

[Gray_101]

ridds said:

I set mine up once it's all stinking hot and it seems to cure the bulk of it. I'm not bothered about how it is when cold as I never really let it idle when cold.

+1

[vroom]

ridds said:

I set mine up once it's all stinking hot and it seems to cure the bulk of it. I'm not bothered about how it is when cold as I never really let it idle when cold.

Fair point.

I guess I want to keep the smooth running during the warm-up

I guess the lumpiness is magnified during this period as I really do drive the car gently (very little throttle) until I see a drop in engine oil pressure

It is reassuring that you guys also experience the same characteristics with you cars as I do.

Cheers

Nick

[ridds]

vroom said:

ridds said:

I set mine up once it's all stinking hot and it seems to cure the bulk of it. I'm not bothered about how it is when cold as I never really let it idle when cold.

Fair point.

I guess I want to keep the smooth running during the warm-up

I guess the lumpiness is magnified during this period as I really do drive the car gently (very little throttle) until I see a drop in engine oil pressure

It is reassuring that you guys also experience the same characteristics with you cars as I do.

Cheers

Nick

Yeah it's a trait of the setup unfortunately. The thing to remember is at what point will you really want you idle balance to be spot on. For me it's when stuck in a jam in traffic or on the motorway, so ideally get the thin red hot, set them even and get your adaptives good around the points where you drive. e.g. very light throttle openings. I'm not even that bothered if they are a few % off above 40% as the variation here will make very little difference to have the car feels or how it is to drive.