flak monkey
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posted on 19/10/17 at 05:01 PM |
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I never got mine to idle less than 1200rpm with roller throttle bodies, fine for a track car not for the road - gave up and went to Jenvey DTH with
the rotrex.
The reason being the clearance around the roller portion of the TB is large enough to allow significant air flow, even with them closed right off you
will bypass enough to idle high. The manufacturing tolerance differences are enough to vary that idle speed by 100rpm or so, and you can slow it down
more with some silly timing maps, but it's covering up a flaw in the design. Roller TB's just aren't meant for low rpms - infact the
airflow through them is awful until you get over 50% throttle.
IMO roller TB's are great on a track car, but a bad choice for road use.
Sera
http://www.motosera.com
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peter030371
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posted on 19/10/17 at 05:16 PM |
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That reminds me I haven't looked at this yet, will try and do it at the weekend.
I have read lots of stories of poor idle ect with roller barrels but >300 miles in with a mixture of road and track use and on a standard engine
(no lumpy cams) mine idles around 1000rpm just fine. Doesn't sound overly fast and doesn't change hot or cold (so far).
So much of my car is a compromise on the road (gearbox noise, no windscreen, poor view in the mirrors, no seat padding and so on) that this compromise
doesn't bother me when it does give a little more power on the track at WOT
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pjay
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posted on 24/10/17 at 04:47 PM |
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Based on Chris's initial comments I dug into the OMEX 600 manual and the section on "Idle Strategies" & "Without air
bypass idle motor". It looks very likely that ignition retard is being used in your set ups to 'restrain' the Idle RPM when hot but
give a fast idle when cold:
"As the engine is being given more air than is required to idle the engine when warm it retards the ignition whilst in the idle condition to
maintain the target engine speed. When the engine is cold it requires more air to idle and so it benefits from the extra air, the ignition is advanced
whilst in the idle condition, and the engine has an improved cold idle speed."
To confirm the Ignition Map and the Idle Scatter Spark Table can be looked at.
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