flak monkey
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| posted on 13/3/10 at 04:58 PM |
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Idle speed issues
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
Sera
http://www.motosera.com
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r1_pete
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| posted on 13/3/10 at 05:22 PM |
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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.
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flak monkey
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| posted on 13/3/10 at 05:28 PM |
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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 
Sera
http://www.motosera.com
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r1_pete
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| posted on 13/3/10 at 05:31 PM |
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Mmm, any pics of them in your archive, just trying to visualise what you have?
Air is getting by somewhere....
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flak monkey
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| posted on 13/3/10 at 05:34 PM |
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Yep, here you go
 
Sera
http://www.motosera.com
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stuart_g
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| posted on 13/3/10 at 05:37 PM |
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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.
http://www.eastangliankitcars.co.uk/
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r1_pete
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| posted on 13/3/10 at 05:39 PM |
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Will the rollers position so they are 'completely' closed? or do they start to open again 1st?
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rusty nuts
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| posted on 13/3/10 at 05:43 PM |
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Can you retard the ignition timing at idle as too much advance will increase the idle speed?
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flak monkey
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| posted on 13/3/10 at 05:44 PM |
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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.
Sera
http://www.motosera.com
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ss1turbo
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| posted on 13/3/10 at 05:55 PM |
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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?
Long live RWD...
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r1_pete
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| posted on 13/3/10 at 05:56 PM |
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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?
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flak monkey
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| posted on 13/3/10 at 06:06 PM |
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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.
Sera
http://www.motosera.com
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Bigheppy
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| posted on 13/3/10 at 07:42 PM |
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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.
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flak monkey
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| posted on 13/3/10 at 07:47 PM |
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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 
Sera
http://www.motosera.com
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Bigheppy
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| posted on 13/3/10 at 07:55 PM |
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Do you mean the body or the rotating butterfly, I was talking about the butterfly.
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flak monkey
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| posted on 13/3/10 at 08:01 PM |
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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
Sera
http://www.motosera.com
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flak monkey
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| posted on 13/3/10 at 08:55 PM |
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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).
Sera
http://www.motosera.com
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MakeEverything
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| posted on 13/3/10 at 09:28 PM |
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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]
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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fatbaldbloke
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| posted on 13/3/10 at 09:45 PM |
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quote:
Advance is locked to 10deg at the mo too.
Can you do anything about that? With bike TB's, for example, it's quite common to have to back off the ignition to 4-6 degrees btdc to
get the idle back under control.
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matt_gsxr
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| posted on 13/3/10 at 11:03 PM |
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Those roller barrels look nice.
Agreed on lowering the advance at idle. Stock map for old Busa is 4deg advance at idle.
Matt
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MikeRJ
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| posted on 13/3/10 at 11:05 PM |
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Retarding the ignition just to reduce idle is surely just masking the real problem?
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rusty nuts
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| posted on 14/3/10 at 08:34 AM |
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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
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MakeEverything
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| posted on 14/3/10 at 08:38 AM |
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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
And the old A Series had an advance and retard pipe to the carb for this reason also.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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MikeRJ
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| posted on 14/3/10 at 10:24 AM |
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quote:
Originally posted by MakeEverything
And the old A Series had an advance and retard pipe to the carb for this reason also.
This is true, but it wasn't to fix a high idle problem. The two reasons I have heard were related to difficult starting (i.e. lots of advance
during cranking causing the engine to kick back), and as a fix for a crank rumble problem at idle. I think it's more likely the former, the
Marina suffered from crank rumble and the vacuum advance was removed entirely!
Other BL cars used ported vacuum advance as well, but it depended on the country they were destined for.
quote:
Originally posted by rusty nuts
Not if the ignition timing is over advanced in the first place!
If the throttles were sealing properly no amount of advance would let the engine run if they were closed...
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flak monkey
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| posted on 14/3/10 at 11:18 AM |
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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!
Sera
http://www.motosera.com
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