Best way to "cut" revs for idle with throttle jacked open?

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EMS
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Best way to "cut" revs for idle with throttle jacked open?

Post by EMS » Fri Mar 23, 2012 12:46 pm

As topic title. We need jacked open throttle for decent ALS, but idle is too high. (of course) Is there a decent way to introduce some sort of rev-limit for idle?

Jasper K
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by Jasper K » Mon Mar 26, 2012 2:47 pm

Hi Mark,

Shouldn't you be using Fuel Cut to keep revs under control?

On the other hand..... If revs are too low so is airflow through the engine and that means the turbo is not going to spool really good anyways. In my opinion it's always a trade off. I would think introducing Fuel Cut to keep revs under control seems like a good way.

TBH. What else would a "Rev-Limiter" normally do?....... Cut fuel(or spark but that wouldn't be very wise) ;-)

Cheers,

Jasper.

EMS
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by EMS » Tue Mar 27, 2012 8:12 am

Hi Jasper,

Perhaps I wasn't completely clear. But I don't mean the control of RPM with ALS on, but with ALS off! With ALS on the ignition retard will drop RPM, but if I jack the throttle open for good ALS the revs go through the roof with "normal" ignition timing...

Cheers,

Mark.

stevieturbo
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by stevieturbo » Tue Mar 27, 2012 10:51 am

Dont jack open the throttle until ALS is active then ? Dont the two happen together ?

Jasper K
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by Jasper K » Tue Mar 27, 2012 3:04 pm

Hi Mark,

If I understand you correctly it seems that you are running a Cable actuated Throttle. You are jacking it open continuously to allow for ALS when activated but this jacked open throttle situation is more or less fixed so gives high revs with "normal" timing. Is this correct?

If this is the case I would strongly suggest to use a Throttle jacker which is only operating when the ALS is active and will not have a jacked throttle when ALS is deactivated. If this is not an option than perhaps a large PWM actuated Bypass Valve would be also a good option. You can keep the throttle as you would normally and activate the Bypass valve as soon as ALS is activated to let a lot of air go past the Throttle body directly into the intake manifold.

Another option would be to fit a DBW throttle body and call it a day :D

Cheers,

Jasper.

EMS
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by EMS » Tue Mar 27, 2012 8:54 pm

Yes, of course cable operated throttle. (otherwise I wouldn't have asked...) ;) I want to open the throttle more by adjusting the screw which sets the throttle rest position. In the Motec you can set a idle rev limit for such setups. In all of the older group N rallycars (no DBW) you need to setup ALS like this. It's not allowed to add by-pass valves or DBW throttle.

pat
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by pat » Wed Mar 28, 2012 9:42 am

Just a quick note....

What you want is AntiLag System -> Off Calibration, where you will find fuel cut and multiplier (if memory serves) to be applied when ALS is *off*, which is designed for just this purpose :)

Cheers,

Pat.

EMS
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by EMS » Wed Mar 28, 2012 12:50 pm

PERFECT, just what I was looking for!

Thanks Pat!

Jasper K
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by Jasper K » Wed Mar 28, 2012 3:38 pm

Awesome! Something new learnt again as well.

EMS
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Re: Best way to "cut" revs for idle with throttle jacked open?

Post by EMS » Fri Apr 06, 2012 1:39 pm

It's the only possible way to get more air in the engine, without being illegal. Finshed the car today and it worked fine with the fuel cut function to have idle speed under control. It's a bit shitty to cruise at low speeds, as you are cruising with something between 1 and 3% TPS. And I need to have quite a bit of fuel cut below 1% TPS to control the revs. But if you drive the car on a rally stage it's perfectly fine! 8-)

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