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setting up antilag on link g4

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hello im having trouble getting the correct setup on my own car rb25det skyline,

iv set this up alot on other vechicles but its just not doing as its ment to does anyone have a base antilag table that would work as a refrence im just getting one massive bang instead of pops and bangs like iv had on other vechicles

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The Timing retard is set for 0-30% throttle, Shouldn't this be 70-100%?

What are you using in the way of air bypass or throttle opening when the antilag is active? I find that this is the most common cause of poor antilag performance and too much or too little can affect it. Too much will normally make its presence known by excessive pushing off throttle though.

The amount of retard you are using is probably a little more aggressive than I would normally run too (although not ridiculous). Probably not your issue but I try and use as little retard as I can get away with to achieve reasonable antilag behaviour.

Viper this sort of antilag is a 'rally' style where throttle opening and ignition retard is used to improve throttle response. It's a completely different technique to the launch control style of antilag.

Oops yep my bad, For some reason I was thinking Launch Control

I think the official terms for both types are "on-throttle" anti-lag... and "off-throttle" anti-lag. ?

Marek, I'm not sure there is any officially accepted terminology and it varies from manufacturer to manufacturer. Personally I refer to rally style antilag as 'antilag' and launch control antilag as 'launch control' or 'two step'.

be careful using the anti-lag on the RB25DET as they have hydraulic lifters which may pump up, if it's performance for shifting up gears have you considered flat foot shifting instead? or is it just for pop's and bangs?

"Chris250", i don't know who told you this, but ALS has no affect on lifters pumping up. Lifter pump-up is caused by high RPM and oil viscosity.

Marek i have to say, Chris250 is absolutly right.

The unburned mixture does spontanious combust in the exhaust manifold. Thats what you hear as "pop and bangs". The pressure peak in the exhaust manifold can and will lift the exhaust valve from it's seat. In the worst case the valves touche the piston, or more likely a shim or some thing else can pop out and damage the valve train. On some engines its alrady critical to run an usual ignition cut rev limiter.

Adrian i don't think you know what lifter "pump-up" actually is.

With anti-lag, peak localized pressure (around the exhaust valve) happens when the valve is still OPEN!.

Conventional back-fires *can* unseat the valves.

Still... has no affect on lifter pump-up (or "bleed out")

Actually Marek, this is a possible concern for the same reason you can't successfully run 2 step launch control with a lot of retard on an engine with hydraulic lifters.

As previously mentioned, large enough pressure pulsations in the exhaust manifold can momentarily pop an exhaust valve back off it's seat. When this happens you end up with lash clearance between the cam and the bucket/follower and the lifter extends to remove the lash - Most people refer to this as the lifters 'pumping up'. After that the valve is held off it's seat and you have no compression and a poorly running engine until the lifter bleeds back down which can take 30 seconds or more.

I've never tried setting up antilag on an engine with hydraulic lifters so I can't comment on whether this is a real world concern. The aggressiveness of 2 step launch control, coupled with the much higher rpm and the higher mass flow through the engine (WOT vs almost closed throttle) makes me say it's far less likely to be a problem during antilag operation than 2 step launch control but not impossible.

thanks guys im only going for pops and bangs and to assist turbo lag as its a big turbo, iv allready got flat shift and launch control active,

andre im using the isc stepper to help atm until i find a throttle kicker that will work with my setup

would you think its not getting enough air and matbe remove some ign retard

Whats wrong with using ISC?

I've yet to find a factory ISC that will bypass sufficient air to allow good antilag operation. A good test would be to see what the idle speed is with the ISC 100% open - If it's only around 1500-2000 rpm then that almost certainly won't be enough air. I generally find in the Group N cars that I've tuned which just rely on a throttle stop will idle somewhere around 4000-5000 rpm if the cyclic idle function is disabled. This gives you some idea how much air is being bypassed.

That being said, incorporating a second ISC solenoid purely for antilag operation 'may' be effective. E-throttle is the neatest solution however I'm getting away from the actual topic now.

Ahh makes sense now, I was setting up 2-Step launch control on a RB25DET and playing with the settings, When I set it to be quite agressive (from memory about 20'ATDC) we got a massive backfire and then the car idled like crap for a little while but came good shortly after.

Thats only if you have massive backfires. A *properly* set up anti-lag doesn't need those violent explosions/backfires to get good turbo spool.

Viper, yes that sounds like the lifters had pumped up and held the valves open. On the 4G63 I usually can't get away with more than 5-10 degrees retard before the explosions in the exhaust manifold pop the exhaust valves open.

Marek as I said earlier, there is in my opinion a vast difference between the operation of the engine in a rally-style antilag and two step launch control. Rpm and mass flow are very different. That being said I've tuned more rally cars than I care to remember and without fail if the antilag was set up aggressively enough top be effective, it results in pops and bangs. Is it the same as what you could expect on two step launch control? - Almost certainly not.

Oh yeah, sorry, i was thinking of launch anti-lag again. With launch-anti-lag (2 step) it can be set up (properly) to have no backfires.

Iv seen a BMW turbo (turbo conversion from NA) run 15 degrees ATDC anti-lag launch... as he wasn't getting any backfires. But im guessing he had higher compression that stock RB25.

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