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CMSport

Mild ALS without air bypass

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Hey all... apologies if this has been covered already but I've had a search around and not found anything strictly relevant

I have a setup with a relatively small turbo used for circuit racing but still suffer a bit of lag through apex on slow circuits. I'm not overly keen on the idea of a full AL system making huge amounts of boost off throttle, mostly from the point of view of preserving my turbo (read as budget). 

I gather it's easy enough to fit a DI switch and setup the basic AL function in the software but am I wasting my time faffing with this if I don't have any additional air being fed in? In addition to this, is there a simple way that I can use EGT's to limit ign retard or turn ALS off altogether if things get dangerously hot? 

If I were able to achieve 0bar or even slightly negative pressure on overrun then I'd be happy with that but if it seems very unlikely that this is achievable then I'll focus my attention elsewhere

 

Cheers

Tim

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A couple of options - if you have an idle valve you can use the ISC override setting to open the idle valve when antilag is on, that will unlikely be enough however.  The other option is to do "group N" style where you adjust the throttle stop so that the throttle is always open a bit.  You then may need cyclic idle to control idle speed when antilag is off.

 

3 hours ago, CMSport said:

In addition to this, is there a simple way that I can use EGT's to limit ign retard or turn ALS off altogether if things get dangerously hot? 

Yes, you can use a virtual aux to enable the anti-lag.  This means you can add logic such as ECT and/or EGT must be below a certain value. 

 

3 hours ago, CMSport said:

If I were able to achieve 0bar or even slightly negative pressure on overrun then I'd be happy with that but if it seems very unlikely that this is achievable then I'll focus my attention elsewhere

Be aware you will not be able to use vacuum assisted brakes with antilag.  Have you tried anything tune related to see if the lag can be improved?  Some engines/turbos for instance seem to spool better with more advance and relatively lean mixture, others seem to improve with retard - so you may find some improvement just from experimenting with some tune variables in the problem area.

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thanks for the response, Adam. I don't have an ISC - just an old style thermo-mechanical bypass - but would be happy with group N style setup on cyclic idle. 

I do understand the impact on boosted brakes with anti-lag but to what extent can I keep with the system connected? if I see zero pressure at the intake is this going to cause a rock solid pedal? or will it be the same as if I'd disconnected the booster vacuum signal? I'm not going to be throwing a whole bunch of intake air at it so I'd be surprised if it made any boost at all with the throttle closed...? 

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It wont make any vacuum at all at idle and worse still at high RPM lift off conditions when antilag is active (say the end of a straight), it will have positive pressure and little engine braking effect.  Typically you will need to convert to a pedal box or electric vacuum pump and vacuum reservoir.

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