antilag systems - WRC mitsu style

[thechuckster]

was trying to find a wiring diagram to share with Cool1 and found these pics on the msefi.com forums.

Is a Antilag system from a WRC mitsubishi (year unknown)

They are using the blow off valve to inject air into the exhaust manifold, this is being done only when you lift off the throttle, now if you inject some extra fuel into the engine at the same time, coupled with timing retard, the extra fuel will pass right through and mix with that air in the exhaust and cause the turbine to spin faster due to the energy produced by the burning of this air and fuel in the manifold.

Notice that in 2nd pic (different valve) the valve is pneumatically and/or electrically actuated, I believe they could use this same method to build boost at launch as well.

Also of interest is the route taken by the dump pipe - over the gearbox before going down between firewall and engine. I guess you can do that when your gear changing and clutch work is all done elctronically.

In the smaller pic, you can see the restrictor upstream of the turbo.




also, the general assemby of hardware under the bonnet is interesting - milspec-type connectors everywhere and ziploc's galore. If you've seen the ARC teams servicing a car, anytime the undercarraige is removed to change/repair parts, all the flexible protectors are re-ziploc'd on.

If they shutdown the WRC, am sure ziploc makers world-wide would shut down.

[chris davey]

Nice find Charles.

SO how does this system compare to other regular ecus like Motec, haltech antilag systems?

From what I have read about it, it isn't the best thing for turbo life but with unlimited budget who cares about that!

[thechuckster]

i think Motec and haltech take approaches that retard timing and/or drop sparks on cylinders (done in rotation to spread the damage across the engine) to while upping fuel.

The trigger for it to happen is throttle suddenly closing, and it does its thing for variable amount of time, or until you open the throttle.

From a canberra-based rally driver (tortfeaser on msefi.com):

I've a bit of experience tuning antilag on other ECUs - motec and autronic principally.

Their control strategies require a couple more variables to be set, but also have a mode where antilag is enabled when TPS exceeds a figure (no switch). (Developed because Group N rules didn't permit changes to wiring looms and aftermarket ECUs had to fit in the OEM ECU case.)

Variables include:
* a 3D table of RPM/VE and retard- retard amount is not net, but subtracted from the calculated advance for the particular RPM/VE point

* a 3D table of RPM and fuel trim - often this isn't used and a global fuel trim % is added. No table necessary.

* a determined idle RPM - this is the RPM that the ECU tries to maintain when antilag is deactivated, using the soft-cut RPM limit strategies already in place (so you wouldn't want to use this stuff for antilag) - much like the launch control stuff. You need this because the throttle is opened to give the air needed to sustain boost, but would otherwise make too much RPM.

* a set of TPS variables - one below which the RPM is limited to the idle RPM (something like 5%), and one (usually about 10% higher) where the RPM is free above that limit (retard interpolated between the two).

* a maximum time variable - to limit EGT, antilag isn't enabled beyond, say 10s. Antilag reenabled when TPS exceeds another TPS threshold (like 80%).

So, antilag works like:

check if antilag switch on.
If yes, check if TPS>antilag TPS limit.
If yes, retard ignition by amount in table, add fuel according to fuel trim.
If no, don't retard (ie antilag not enabled).
If TPS<>two TPS variables, limit RPM phased out (linear interpretation).

If antilag enabled greater than max time, disable antilag. Reenable when TPS exceeds a threshold.

Its common to have an EGT probe set, and to disable antilag if EGT exceeds a threshold.

Ignition retard is maintained up to 100kPa, but not higher. The Autronic docs say ignition timing for small capacity 4 valve central spark plug combustion chamber engines should be in range -20 to -30 deg. For large capacity 2 valve engines -2 to -20 deg should suffice.

fwiw, i think toyota in the ARC use motec, dynomatt might be able to confirm?