Trottle stop and pots
Discussion
I've discovered my engine is idling with the throttles fully closed. This is making it rather difficult to set the pots because every time I open and close the throttles they seem to come to rest in a slightly different position. I assume this is due to the various resistances along the throttle assembly.
I would prefer my throttles to close against the solid stop to make adjustments more accurate. All I can assume is that the engine is getting sufficient air via the drilled butterfly screws and emissions purge pipes.
If I replace the drilled screws would this reduce the idle air flow sufficiently to be able to use the normal throttle stop?
Does the fact that the engine is idling with the throttles fully closed suggest another problem?
Finally, I assume the butterfly screws are threadlocked as loosing one would be terminal.
I would prefer my throttles to close against the solid stop to make adjustments more accurate. All I can assume is that the engine is getting sufficient air via the drilled butterfly screws and emissions purge pipes.
If I replace the drilled screws would this reduce the idle air flow sufficiently to be able to use the normal throttle stop?
Does the fact that the engine is idling with the throttles fully closed suggest another problem?
Finally, I assume the butterfly screws are threadlocked as loosing one would be terminal.
Unfortunately you have a bit of a problem finding your leak there.
The only point of the holes drilled through the butterfly bolts is idle balancing, not idle speed.
Assuming the guy who drilled the bolts knew what he was doing then replacing the drilled bolts with undrilled ones will make your engine slower but more lump, less smooth idling.
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What am I saying, the AJP is the lumpiest engine ever at idle.
Alternatively make sure butterflies are sealing, and bolts done down tight on inlet to manifold.
The only point of the holes drilled through the butterfly bolts is idle balancing, not idle speed.
Assuming the guy who drilled the bolts knew what he was doing then replacing the drilled bolts with undrilled ones will make your engine slower but more lump, less smooth idling.
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What am I saying, the AJP is the lumpiest engine ever at idle.
Alternatively make sure butterflies are sealing, and bolts done down tight on inlet to manifold.
if the buterflies are fully shut and you adjust the idle scrws on the dead stop ever so slightly, then it should adjust the idle nicely. for it to jump to 1500rpm, either your are turning the idle screws too much or the increase in the idle screw adjustment mixed with the air through the drilled screws in the butterflies is making the big jump up in revs.
I would block or replace the drilled butterfly screws with solid ones and make sure the butterflies shut properly and are not sitting open at all.
Then follow the Tpots setting porcedure, have you seen the big write up on the procedure? its not too difficult once you readit 100 times and fiddled with the car while trying to work it out.
I would block or replace the drilled butterfly screws with solid ones and make sure the butterflies shut properly and are not sitting open at all.
Then follow the Tpots setting porcedure, have you seen the big write up on the procedure? its not too difficult once you readit 100 times and fiddled with the car while trying to work it out.
brakedust said:
Mine also idles with the butterflies all shut, idle screw all the way in and the bar removed.
Im not at the car for a few days, will have a look if mine are drilled also but I dont think so.
Be interested to see what you come up with
I this situation, I would go round the car and put the flat of your hand over each inlet in turn, to see if one is letting air through.Im not at the car for a few days, will have a look if mine are drilled also but I dont think so.
Be interested to see what you come up with
If nothing cover a bank at a time.
You shoulde be able to stop the engine with all the butterflies closed.
You should be able to stop the engine with the butterflies closed, but you'd be surprised how little air is required to keep an engine running. Many cerbs idle just fine with all the throttle stops backed off / not touching .. theres enough air bleeding around the butterfly edge to keep it going, and some cars (with the added flow of drilled screw to even airflows up) idle too high with no apparent scope for bringing the airflow down.
While I have you here jools, did you ever have a problem with butterfly rods seizing in the inlet tract?
I'm messing with the no-rod thingy and in the throttle body I'm playing about with there is a brass ferrul in both ends of the throttle body. I'm sure I've never seen that before.
What is means is that the rod never did sit on any of the holes between one end and the other, just on the two brass rings at either end.
In fact I'd go as far as to say the middle two throttle bodies have quite an easy escape of air as the rod is not airtight in the middle three aluminium casting holes.
I'm messing with the no-rod thingy and in the throttle body I'm playing about with there is a brass ferrul in both ends of the throttle body. I'm sure I've never seen that before.
What is means is that the rod never did sit on any of the holes between one end and the other, just on the two brass rings at either end.
In fact I'd go as far as to say the middle two throttle bodies have quite an easy escape of air as the rod is not airtight in the middle three aluminium casting holes.
Well I removed the throttle link, loosened all the butterfly screws, replaced the drilled screws, made sure all the butterflys were fully seated and tightened the screws again.
Re started engine and it would not tick over. Brought the idle screw upto the throttle and adjusted it to 1,000. Re attached throttle link and using a synchrometer balanced air flow rate so both banks were flowing 4kg.
Spotted one problem. All cylinders were flowing 4kg apart from 8 which was flowing 7. Something wrong there.
Now the trottles are stopping against the idle screw and are balanced I have a better reference for setting the pots. Tickover and low rpm driving seemed smooth. However, I am getting a fault on Throttle Pot1. Will replace tomorrow.
Re started engine and it would not tick over. Brought the idle screw upto the throttle and adjusted it to 1,000. Re attached throttle link and using a synchrometer balanced air flow rate so both banks were flowing 4kg.
Spotted one problem. All cylinders were flowing 4kg apart from 8 which was flowing 7. Something wrong there.
Now the trottles are stopping against the idle screw and are balanced I have a better reference for setting the pots. Tickover and low rpm driving seemed smooth. However, I am getting a fault on Throttle Pot1. Will replace tomorrow.
I had something like this, that no8 throttle is letting in air or it's coming in through the manifold gasket or a split in the manifold itself.
If you can with the engine off pressurise throttle 8 with the butterfly open you'll soon know if air is escaping. I used a bung with a shrader valve from a bike inner tube pressed through from the back. and pumped it up with a bike pump.
Another way with the engine ticking over spray a bit of easy start or brake cleaner round the base of the throttle inlet, if the revs flare you have a gap.
If you can with the engine off pressurise throttle 8 with the butterfly open you'll soon know if air is escaping. I used a bung with a shrader valve from a bike inner tube pressed through from the back. and pumped it up with a bike pump.
Another way with the engine ticking over spray a bit of easy start or brake cleaner round the base of the throttle inlet, if the revs flare you have a gap.
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