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Author: Subject: Titan Roller Barrel TB Idle
flak monkey

posted on 19/10/17 at 05:01 PM Reply With Quote
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

posted on 19/10/17 at 05:16 PM Reply With Quote
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

posted on 24/10/17 at 04:47 PM Reply With Quote
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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