EFI Quick Shifter, Fuel or Ignition cut?

[Danm54]

The quick shifter on the turbo is currently set to ignition cut and works fine at low throttle openings with the usual pop and flame out the exhaust.

But as I'm shifting at higher rpm and throttle opening I'm feeling the pulse out the air filter as well, its also one hell of a bang.

 

I've read plenty of opinions on fuel cut and generally its considered ok as long as its a total fuel cut and not still injecting enough to cause a very lean condition.

Ignition cut is also considered quite hard on the turbo/manifold and with the harshness that its exploding I'm worried about causing damage especially if I'm feeling it out the intake.

I don't think I've got the option to pull timing but I'm not sure thats a safe way to go either.

 

So whats the opinion in here? What are you using and how effective is it?

 

Thanks

[FJD]

what kind of ignition do you run ?

[wombat258]

I am running ignition cut only on paddle shifted turbo EFI at 12 psi boost with no problems. Admittedly I am using a closed loop system that shifts in 12 to 30 ms. It would probably be different with a slower timer based shift cut system.

[FJD]

i can only talk from second hand experience, my uncle runs a Motec on his turbo dragbike, and he just changed from fuel cut to running ignition after TDC, this keeping turbo spinning/reducing lag

[Arttu]

Fuel cut should work as well as long as you have the injectors relatively close to the intake valves.

On the other hand correctly configured ignition cut shouldn't cause much popping either. Rule of thumb is that if you hear popping while shifting you have too long cut time.

[Danm54]

Using a Specialist Components Typhoon ecu.

 

Injectors are right before the head so as close as you can get to the valves.

 

I'll check how long the ignition is cut for, I guess if its not long enough it won't shift.

Will also check what other options I have.

[Danm54]

Ok, got the option of ignition cut or ignition retard 

Gear cut time is 60ms

Fuel multiplier is 0.6

Ignition retard is 30 degrees

Retard ramp-out rate is 30ms

 

So I can change it to ignition retard

Drop cut time in stages I guess to find the minimum it needs

Fuel multi might as well stay the same?

Ignition retard - I'm not sure if it pulls 30 degrees off the timing or sets it at 30. Will have to call Specialist Components to find out. I'd guess it pulls 30 degrees off the map though.

 

Not sure how much ramp out it needs but I'll ask about that too.

[Gixer1460]

Are we taking air shifter or just a linkage triggered foot shift? If the former, the optimal time we measured was between 60 - 70ms total but the actual kill time is only a portion of that and its not at the start. You trigger the shift and solenoid released air takes two paths - one to the ram, the other to the kill switch which due to a longer air line has a delay built in as so the ram builds pressure on the lever, then the kill occurs, unloading the gears so ram can push through then 20 - 30Ms later the ignition is back on. If its foot shifting, you have to play around with the trigger point for the kill as its you preloading the lever not a ram. I believe either ign. or fuel cuts work equally well - its just timing that is the key - some sound like a autobox others bang and flame - guess which ones have their timing right!

[Danm54]

Its the linkage triggered shifter, and yea mine is the one that bangs and shoots flames!

[Arttu]

Hmm, 60ms cut time should be at right ballpark. If I remember correctly I'm using 80ms on my GSX with normal foot shifter. With air shifters I have been using 40-60ms with good results. These were with plain ignition cut, no retard nor fuel modifiers.

So I'm wondering if that ignition retard is causing problems in your case. If it's retarding 30 deg from current value that will probably result something like 0 deg timing when spark comes back. And that will effectively lit up all un-burnt mixture in exhaust.

[Danm54]

It's been set to ignition cut so I assume it doesn't retard the ignition but it does reduce fuel. I could reduce the fuel even further as a total ignition cut wouldn't ignite any lean mixture.

 

[Gixer1460]

Not preaching but please don't try 'reducing' fuel to unload the engine - cut it ALL or do it with retard. Boost + lean mixtures melt things...... no fuel = no power = no lean mixture. Personally I wouldn't ramp anything fuel or timing - cut it all and bring it all back instantly / at one time, as I can't see the point speeding up a gear change to then 'slowly' build power back with ramped timing? Its already at lower revs so needs the power to continue the drive.

In the 'old days' with uncontrolled ignition kills, we found that if you kill the ignition system as well as the coils you get the biggest bangs as the ignition when switched back-on, tended to fire any / all the plugs till correct timing was re-established - leaving the ignition live to keep the timing correct and trying to fire 'dead' coils worked well.

[Danm54]

Well it already reduces fuel to .6 with the ignition cut, I wouldn't do it without ignition cut.

I don't see much point it firing fuel in if its not going to be ignited but I guess its better than too little fuel when it ignites.

 

If I set the multiplier to 0 that would cut all fuel and I could set the ramp-out to 0 as well, don't want it bringing fuel back gradually.

 

That should cut fuel and spark simultaneously for 60ms and bring them both back together.