RazMan
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| posted on 1/12/10 at 03:07 PM |
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Lowering idle speed with timing?
I'm having a few problems getting a slow idle after fitting my ITBs and it is probably due to the butterflies not sealing perfectly (3 attempts
at this now). I can get it stable at 1100rpm and I just want to bring it down to 800 - 900rpm. Clearly I can't adjust the idle in the normal way
so I thought maybe a bit of creative mapping might help.
What is the best way to do this? Do I simply retard the ignition more aggressively at 800rpm and get it back to normal at 900rpm? Any thoughts guys?
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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flak monkey
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| posted on 1/12/10 at 03:10 PM |
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Run it down to maybe 2 or 3 deg at idle, should slow it down and wont cause any major problems.
Youll need to fiddle with the values just off idle to sort the throttle response, but just ramp it up to normal values pretty quick. I assume you are
running TPS based advance?
I know of people running negative timing at idle with roller throttles to pull the idle speed down enough to make it sensible.
Sera
http://www.motosera.com
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atspeed racing
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| posted on 1/12/10 at 03:20 PM |
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Try loosening the throttle butterfly's and snapping them shut, then retighten them. If the butterfly isnt central it can cause high idle
problems.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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RazMan
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| posted on 1/12/10 at 03:29 PM |
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I have carefully fitted the butterflies 3 times now and this is the best result I could get. I even applied some Molykote 321 which improved things
enormously but I still can't get it lower than 1100rpm - I guess 12 burrerflies is just too much 
Here is my timing at the moment ...
 
Description
Flak - you say to run it down to 2-3 degrees at idle. Ermmmm I'm about that now and considerably more at anything lower - any ideas? 
p.s. It is indeed a TPS based setup
[Edited on 1-12-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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RazMan
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| posted on 1/12/10 at 04:08 PM |
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Update: I have had some success! I took the timing @ 1000-1750rpm down to 2 degrees and presto! - it idles at 850rpm with an AFR of 13.5 I also
tried 1 degree but I could hear some farting in the trumpets so I thought that was a little too far.
That's a relief as my ITB project was looking a bit compromised.
Thanks Flak - you were spot on!
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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flak monkey
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| posted on 1/12/10 at 04:27 PM |
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Good stuff.
Sera
http://www.motosera.com
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matt_gsxr
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| posted on 3/12/10 at 07:57 PM |
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I wonder where he learned this trick?
http://www.locostbuilders.co.uk/viewthread.php?tid=131856
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flak monkey
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| posted on 3/12/10 at 08:16 PM |
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Yep, I speak from personal experience 
Its what I like about these sorts of projects, you always learn loads of stuff, which hopefully then helps someone else out...
Sera
http://www.motosera.com
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RazMan
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| posted on 3/12/10 at 10:56 PM |
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quote:
Originally posted by flak monkey
Its what I like about these sorts of projects, you always learn loads of stuff, which hopefully then helps someone else out...
Exactly right A few years ago I didn't know anything about building a car and it is only due to people here that I learned all the processes
I needed - now I'm making throttle bodies, mapping, who knows what next!
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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matt_gsxr
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| posted on 4/12/10 at 09:48 AM |
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quote:
Originally posted by flak monkey
Yep, I speak from personal experience
Its what I like about these sorts of projects, you always learn loads of stuff, which hopefully then helps someone else out...
No offence intended, I just like it when you see the genealogy of answers.
I certainly read it in a book that was recommended in an earlier thread. The learning is the best bit for me.
Matt
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atspeed racing
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| posted on 7/12/10 at 12:08 PM |
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what is your TPS voltage at close?
this effects MBE idle a lot, can cause massive flat sopts with throttle pick up if not correct. so for MBE is VITALLY important.
generally MBE systems idle and anti stall very well if the base set up is correct. 5degrees ignition at idle works very well with MBE on most
engines.
- colin.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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RazMan
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| posted on 7/12/10 at 12:35 PM |
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Hi Colin, I had to re-index the TPS for the ITBs and it is now ~0.43v (closed) and ~3.48v (WOT) - is this ok? Also I found that increasing the fuel
gain was necessary to get some more headroom in the map, although I haven't started any road tests yet.
I was exploring the MBE sample maps and all of them seem to use 0deg advance at idle and I found that 1-2deg was about right for me, although I will
need a session on your dyno eventually to get things set up properly
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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atspeed racing
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| posted on 7/12/10 at 02:33 PM |
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as long as your TPS reading moves as soon as you open the throttle then its ok.
what normally happens when its set incorrect is you will open the throttle the first few % and the ecu will not register any voltage change, so doesnt
add in any extra fuel for opening of the throttle.. so you get a horrible flat spot that no ammount of mapping can get rid of. so makes pulling away,
or very light throttle driving very horrid.
- colin.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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RazMan
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| posted on 7/12/10 at 03:13 PM |
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Ah ok I see what you mean now. I already made that schoolboy error when I first tried to start the engine and wondered why I wasn't getting any
fuel to the injectors. At least I'm learning by my own mistakes though
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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atspeed racing
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| posted on 7/12/10 at 04:47 PM |
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your own mistakes are the easiest to learn from.
good stuff
if your ever in any doubt, feel free to send me over your map file and i can take a look over it for you: info@atspeedracing.co.uk
- colin.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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RazMan
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| posted on 7/12/10 at 05:10 PM |
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That's very kind mate - U2U sent
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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