The idle bleed screws are also all the way in.
Wondering if the seal isnt good enough around the rollers, if its not I will be rather annoyed as they are brand new
Looking for some ideas as to why I cant pull my idle speed down.
Tick over is around 1200rpm and I cant get it any slower. If I wind the idle srew right out it just starts to open the rollers again (they will turn
through 360deg).
I have checked the map take offs as I thought they were leaking, but they are ok. Throttle bodies are mounted direct to head with O-ring seals.
Mounting faces are all good.
With the throttle effectively closed if you put your hand infront of each barrel all are still drawing pretty hard.
Any ideas?
David
Are you saying the butterflies will turn through 360?
If so I'd suspect that was you problem, they are slightly oval normally so they can provide a complete seal, facilitating very slight openings to
control tick over air flow.
Failing that, do the TB's have air bypass screws in them? the GSXR750k ones I had did, screws could be too far out.
The throttle bodies are roller barrels, so yes will turn through 360deg when not installed on the car.
The idle bleed screws are also all the way in.
Wondering if the seal isnt good enough around the rollers, if its not I will be rather annoyed as they are brand new
Mmm, any pics of them in your archive, just trying to visualise what you have?
Air is getting by somewhere....
Yep, here you go
Could this also be down to the wrong amount of fuel? I know when I adjust the fuel map on my ECU the idle can go up without touching the
throttle/butterflies.
you may be chasing the wrong cause of the problem trying to find air leaks.
Just a thought.
Will the rollers position so they are 'completely' closed? or do they start to open again 1st?
Can you retard the ignition timing at idle as too much advance will increase the idle speed?
Yes they will just position completely closed, but it makes no difference to the idle speed
I can slow the idle down by making it really rich (10 or less), but thats besides the point once you get to around 13:1 idle speed is closer to
1300rpm
Advance is locked to 10deg at the mo too.
Is there any breather system installed the engine side of the barrels - and could it be running off the air supplied through that? That wouldn't match with your first comment though (still drawing if trying the "hand" trick)...are the barrels meant to be air-tight though? If not, how do they seal against the body?
Air has to be getting by the barrels if you can feel it being drawn in when closed, which doesn't sound right.
be worth contacting the supplier to check you haven't got miss matched body barrel assys - can you detect any lateral movement?
There's no movement on the barrels, they are mounted on sealed bearings at both ends. There obviously has to be some clearance so they dont jam,
but how much there should be I dont know.
The only openings the engine side of the rollers are the map take offs, which are all sealed off and the injector ports, which dont appear to be
drawing any air in either.
You can definately feel air being sucked in around the barrels though even when completely shut.
Could you have the barrels 180 degrees out ? might sound a daft question but you said they can rotate through 360 deg, it might make a difference.
No they are definately right, the ports are different shapes on the outside and the engine side so its easy to tell if the are wrong 
Do you mean the body or the rotating butterfly, I was talking about the butterfly.
The barrel/butterfly is also directional. The outside of the hole is round and the engine side is oval so you can tell if its wrong
I have just been speaking to a very knowledgable chap at Track n Race down in London who has given me a few pointers and things that I should try
before going too far.
First I am going to have the throttle bodies off and see if I can see anything obvious. Maybe the seals arent sitting right, but I think it would have
to be all 4 of them as they all show the same airflow on the synchro.
If that doesnt do anything then its back to playing with the map. The best suggestion at the moment seems to be to run a lot less ignition advance at
idle (even as low as 0 degrees is OK at idle which suprised me) to bring the idle speed down. The concern at the moment is that the idle speed is
1300rpm even though its running massively rich (11.5 AFR) and with the theoretically correct advance (10 deg).
Why are you surprised that 0 degree advance is worthwhile trying? Sorry for my ignorance, but im anticipating difficulties when i set up my MS2 with
the new engine.
What i mean is, surely you can run an engine on anything from 0 degrees, and that its the engine components and performance requirements that dictate
what the advance needs to be?
[Edited on 14-33-10 by MakeEverything]
quote:
Advance is locked to 10deg at the mo too.
Those roller barrels look nice.
Agreed on lowering the advance at idle. Stock map for old Busa is 4deg advance at idle.
Matt
Retarding the ignition just to reduce idle is surely just masking the real problem?
quote:
Originally posted by MikeRJ
Retarding the ignition just to reduce idle is surely just masking the real problem?
quote:
Originally posted by rusty nuts
quote:
Originally posted by MikeRJ
Retarding the ignition just to reduce idle is surely just masking the real problem?
Not if the ignition timing is over advanced in the first place! At least one major manufacturer (VW) has used ignition advance to maintain an even idle in the days before engine management
quote:
Originally posted by MakeEverything
And the old A Series had an advance and retard pipe to the carb for this reason also.
quote:
Originally posted by rusty nuts
Not if the ignition timing is over advanced in the first place!
Done a little more playing around this morning and got the idle to around 1100rpm with 2 deg advance.
I am going to have to pull the throttle bodies off and check all the seals I reckon.
I am also going to speak to Titan on monday and see if they have any suggestions!
An idea MIGHT be to get it running and at its idle position and then smear some thick grease/vaseline round the barrel/opening ( without moving the
rollers).
Then start it and see if the idle is lower ( or if it idles at all). This could possibly eliminate your concern at the roller to body clearances.
If it sucks the grease in then the clearances must be substantial I'd have thought.
Does it have a MAF sensor fitted and if so, have you tried cleaning it?
Phil
quote:
Originally posted by flak monkey
I have just been speaking to a very knowledgable chap at Track n Race down in London who has given me a few pointers and things that I should try before going too far.
First I am going to have the throttle bodies off and see if I can see anything obvious. Maybe the seals arent sitting right, but I think it would have to be all 4 of them as they all show the same airflow on the synchro.
If that doesnt do anything then its back to playing with the map. The best suggestion at the moment seems to be to run a lot less ignition advance at idle (even as low as 0 degrees is OK at idle which suprised me) to bring the idle speed down. The concern at the moment is that the idle speed is 1300rpm even though its running massively rich (11.5 AFR) and with the theoretically correct advance (10 deg).
Stripped everything down on the intake side, made sure everything was super clean and reassembled it all. Now have a hunting idle (800-1200rpm) which
indicates to me I have an air leak somewhere It could have been that I started off with a substantial air leak causing the idle to be so high.
It now also revs a lot better without really changing anything else, so I might be heading in the right direction.
Its still all off at the moment, think I will smear some hylomar on the seals for the throttle bodies when I reassemble everything and see if that
helps. Been on and off twice, both times with the same result.
PS yes I meant Track n Road... they also told me not to bother with megasquirt - and gave several good reasons. But as I already have it I'll
stick with it for at least this year.
[Edited on 14/3/10 by flak monkey]
quote:
they also told me not to bother with megasquirt - and gave several good reasons