Thoughts on a DIY timed anti lag controller

[sublunacy]

I dreamed something up today, Critisism is welcome :]
So.... if revotronic gets the Anti lag function enabled with the stock ECU, and had a hand operated switch for on/off, then......>

Ill illustrate.... When you press the pedal ALL the way to the floor the Anti lag would be switched on, and a DIY contoller with a countdown timer would turn it off. after say 1 second or whatever.

- pedal slaps floor/ Antilag on!

----------- -----------------
-that system can funtion on its own with no manual user input right? It could be tucked behind the dash, and the wiring being run apropriately.- Being hidden alltogether-. BUT the system will be electricaly driven, allowing us to install a hand switch to cut the power, effectively turning the Anti lag off alltogether, just sayin you could, but not really needed.

Switch on, and pedal slaps the floor- AL On
Switch off- AL Off


imagine that on our Beasts? it would be totally disgusting,
Whoooomm, Crack Crack Crack
What do you guys think??????????????

[log1call]

What is this anti-lag?
Subaru measures the speed the throttle position resistor changes at and uses that change speed to calculate how much fuel to inject. They do that because if they only used the air flow meter to calculate fuel rates, the long subaru inlet manifolds would give a lag before the air flow meter gets a change of reading, so the motor would be a bit lean for a second when you first floored it. They measure the airflow(as it is at that second), take note of the "speed of change", of the TPS, and then calculate the IPW from those two figures(plus temp etc as per normal cars).

I don't know what you could switch off to stop anti-lag, or why you would want to.

Do you know how or what revtronics do that is different to that?
Do you know how their "anti-lag works?

[gijonas]

i believe he is refering to a very destructive process wherein upon letting off the throttle,fuel is dumped and timing is retarded to the point where combustion takes place in the exhaust manifold? this causing the turbine to continue being fed exhaust pressure while off throttle.Maybe im wrong.

[Legacy777]

That's what he's talking about.

For a street car, it's just going to cause lots of problems and premature engine/turbo death.

[93forestpearl]

What is interesting is that the WRC cars did not use that method for antilag. They had a valve that went from the charge piping to the exhaust right before the turbo.

[jamal]

you'd also need a solenoid to hold the throttle open when you take your foot off, and a map switch for the als to actually work. So the whole foot to the floor to turn it on thing would be pretty pointless when you could just have a switch do everything.

[sublunacy]

I realize its destructive to th turbo and exhaust. but come on!
Does no one want? i don't think so.

I heard that our ECU has an antilag feature built in, but disabled.
is this true? what happens if it is enabled then, illuminate me?
Has anyone got it to work yet on our stock ecu, yet?

[ericem]

ask revtronix maybe it needs extra devices as mentioned for it to work. Fuel economy would really suck though lol.

[evolutionmovement]

Compressed air tank filled by waste pressure. It works (Ford and Subaru WRC team usage was banned by the FIA), isn't destructive, is far more clever, and reuses otherwise wasted energy. The picture Dan posted shows part of the system, I believe. If that's not the exact system, it's very close. I posted about it a couple times in the past and I'm too lazy to find the links.

[gijonas]

Just build your engine so it is fast enough that you dont need that crap.Is it worth ruining your engine within weeks just so you can get to the corner stop in 47.87 seconds rather than 46.96?I think the coolness factor of popping noises from your tailpipe will lose its novelty once you realize that it costs you like $150 each time it happens.

[skid542]

Why all the hate?

I'd LOVE a good anti-lag system. It's true, they do tend to be hard on the turbo. But there's a lot of people out there that run them with no troubles. I have a good friend that runs a two-step (MSD ignition) anti-lag for his drag car and he's never had problems with it. A lot of the manual tranny guys do in the drag world.

And so what if it's hard on the turbo - just run a cheap TD04 and replace it occasionally when it needs it. I think an antilag on something like a TD04 would be a pretty wicked street auto-x machine.

I'd really like to have something as cool as the WRC guys that runs off of an air charge of some sort opposed to igniting gasses. I'd love being able to use my now useless cruise control lever to activate an anti-lag for launches or have a hard switch so it comes in during my shifts. I may not use it all the time, but the times I get to/decide to would be a blast.

Yes, it can be hard on components, particularly if it's not done right. But lets keep things in perspective. Honestly, how many people here actually have any hard experience with anti-lag? Admittably, I have limited personal experience but what I've seen I like.

So I say lets keep the ideas flowing. Maybe we can finally piece together a viable solution.

How much air does the tank for the air-suspension hold? Would it be enough for the occasion go?

[evolutionmovement]

That's my wondering, but IIR the piece in Racecar Engineering from about 8 years ago, the tank was rather large, but then, it was intended to be used often. In my book, I originally put the tank in the passenger footwell (and didn't think it would actually work, so my character ended up using it to deploy active aero aids), but the Subaru WRC team used the trunk. The piping looked pretty large, though—like 2.5-3" tubing. I think something the size of a grille propane tank would be plenty, plus the volume of the pipe that should also be pressurized. If you don't have ABS, you could fit something there so distance is minimal or fit it behind the fender like the air suspension, but on the passenger side.

The whole thing could be on an on/off switch and when active, be deployed by a pressure switch. Someone would need to do some math—flow rates and volume needed, of course, the higher the pressure, the smaller pipe needed, but would you have the volume? As for angle of delivery, I have no idea, but the picture posted shows an angle I would never have figured on. Maybe it's not critical, or maybe you want the air facing away so the cold air doesn't hit the hot turbo directly.

[sublunacy]

evolutionmovement the wrc cars have "synchroshift" wich is probably why the canister could be small. with our slow manual shifter an 8+ gallon tank sounds about right. The hardware would weigh about 20 pounds?
- whats the pro's and cons?

Does anyone have any experience with the AL built into our stock Puters? Im asking becuase if the puuter is controlling it, i figure it will probly run hassle free for a Long time. Big explosions in the exhaust would be harmfull Yes. But small ones that are properly timed and controlled should be ok. Its not the explosion that drives the turbo, itsthe vacumm created by the explosion that keeps the air moving. Because it only travels one way! and it keeps the turbo spinning so how could there be back pressure, or even seriously harmfull pulses? Done right it should be fine for rebuildable turbos, or maybe ball bearing turbo's......

[evolutionmovement]

The WRC cars had large canisters. I think you could get away with less on a street car as you'd be using it less. Blow-off valve pressurized air could be used to refill the tank. Originally, I planned it to also tie into a wastegate control that would allow an overboost that would be used to fill the tank, but that would be complicated and require several pressure sensors to run it (or maybe a simpler system of a secondary relief valve). An electric pump and/or manual valve for refilling would be the easiest way to do it. The air could also be used for other things—like the pneumatic air dam and side skirts from my book to maintain your ground clearance when you want it or you can use it for whatever else you can think up.

[log1call]

Ok, well that's all very interesting.

I'd imagine though, that to keep enough air flowing to keep the turbo spinning you would have to not close the throttle wouldn't you?

I presume the rally guys only half close their throttles and do really quick changes? It would work though if you were just easing off a little for a corner perhaps.

If you wanted to use the pressure resevour tank idea I'd imagine the tank would have to be huge, and the piping too?

What if you fed the blow-off to the exhaust and fed fuel in there with a retarded timing to ignite it.

The trouble I'd see with any of these systems is that your gear changes would get slower without snappy shut-off when you backed off the throttle.

Anyone tried it and actually had faster times through the gears? Or does it only work through corners in one gear?

[gijonas]

Just pulled this from rallycars.com.


When the driver lifts his foot from the gas pedal the ignition timing is altered with sometimes 40° or more of delay (retard) and the intake air and fuel supply mixture is made richer. The inlet butterfly is kept slightly open or an air injector, bypassing the inlet butterfly, is used to maintain air supply to the engine. This results in air/fuel mixture that keeps getting in the combustion chambers when the driver no longer accelerates. The ignition being severely delayed, the air/fuel mixture reaches the exhaust tubes mostly unburned. When the spark plug fires, the exhaust valve is starting to open due to the ignition delay mentioned above. Additionally, the exhaust temperature being extremely high, the unburned fuel explodes at the contact of the exhaust tubes. Luckily the turbo sits right there and the explosion keeps it turning (otherwise it would slow down since its intake, the exhaust gases, is cut-off). The effect is vastly lower response times with some downsides:

A quick rise of the turbocharger's temperature (which jumps from ~800°C to the 1100°C+ region) whenever the system is activated
A huge stress on the exhaust manifold and pipes (mounted on a street car a bang-bang system would destroy the exhaust system within 50-100 km) The turbo produces significant boost even at engine idle speeds
The explosions which occur in the exhaust tubes generate important flames which can, sometimes, be seen at the end of the exhaust tube
Reduced engine brake
The ALS effect is mostly dependent on the quantity of air allowed into the engine, the more air supplied the more the ALS effect will be noticeable. Consequently ALS systems can be more or less aggressive. A mild ALS will maintain a 0 to 0.3 bar pressure in the inlet manifold when activated whereas, when inactive, the pressure in the inlet manifold with the throttle closed would be in the region of -1 bar (absolute vacuum). Racing ALS versions can maintain a pressure of up to 1.5 bar in the inlet manifold with the throttle closed.
While the systems mounted in Toyota and Mitsubishi racing cars are relatively smooth and noiseless those fitted in Ford and Subaru cars are much more noisy and aggressive.
The bang-bang system owns its name to the loud explosion noises one hears whenever the driver lifts off. Most racing implementations have user selectable anti-lag settings depending on the terrain, usually three settings can be selected by the driver going from mild to very aggressive.