Jump to content

Fuel Cut Anti-Lag


MiSTI

Recommended Posts

It would be nice to have selectable Fuel Cut, Ign Cut or a combination of both for the Anti-Lag strategy.

With Fuel Cut the EGTs are lower and it is not as harsh to the engine as Ignition Cut.

Some other ECU manufacturers offer this and in professional motorsport mainly Fuel Cut is used anyway.

Link to comment
Share on other sites

aren't you mixing antilag and launch control?

 

antilag is made to spool the turbo when being off throttle, with letting air pass combined with a late combustion to make more exhaust gas energy spooling the turbo. there would be no point doing a fuel cut in this strategy

Link to comment
Share on other sites

I think maybe on Launch Control is useful to have IgnCut+FuelCut strategy. Maybe it would help to raise a little bit of boost and then control the RPM range very precise without huge backfires.

ALS is overrun boost control. Throttle closed, boost is maintained. 

I've recently tuned Rallycross Supercar, Cosworth YB with G4+ Thunder.
There is a fresh air ALS valve (Turbosmart ALV), which directly pushes air from intercooler pipe to the exhaust manifold.
I've tried without ignition cut and also removed some fuel. No response from ALS was shown.
After that I've added ignition cut and also lots of additional fuel.
Of throttle boost maintained static what I wanted, and EGT dropped to 700-800C during ALS
Extra fuel cools down the overall ALS system.

If You have really huge exhaust temperature then lower Your ignition retard. This parameter rises stress on exhaust valves.

Link to comment
Share on other sites

On 10/14/2021 at 10:59 PM, davetest said:

How are you going to keep the turbo spooled if you just cut the fuel which was being combusted to keep the turbo spooled?

You don't cut 100%

It's around 70-90% and the remaining combustion will be retarted up to 35° ATDC.

This is high effective and produce at least as much bosst with ign cut,  but by fare more steady. Works for antilag and launch control. 

Link to comment
Share on other sites

  • 1 year later...

I agree with MiSTI, the strategy would be much better with the option to use either ignition cut or fuel cut. 

I know from personal experience that over the years fuel cut has been more commonly used by top end WRC level teams as it provides more stable ALS conditions and is much simpler to calibrate. 

The lack of the fuel cut option is one major reservation that I personally have about Link ECU when asked to recommend a ECUs for my clients.

Link to comment
Share on other sites

  • 1 year later...

I have been putting around, and I am wondering if you guys could share a bit more about how to use the fuel and ignition cut during ALS.

nothing too serious, no rally or autocross car, just for sake of trying and understanding :)

I am familiar with how ignition retard works and fuel trims. Currently I would retard as much igntion as possible with +20% fuel trims (EGT limit) and then opening ISC until I'm not comfortable with push.

Now if any of these Fuel and ignition cut help with EGT and push while maintaining good throttle response that sounds like a win :D

If let's say both fuel and ignition are cut 50% of the time, are they cut on the same cycles? or randomly (so that some fall on same cycles and some fall separate).

Is there a point where too much is too much if it doesn't have that bad of an impact on EGTs?

Link to comment
Share on other sites

  • 5 weeks later...

I have been reading up on posts such as these as it is what I have been on with over the last few days.

Using pc link to change a few settings in the Evo 6's G4X (tuned by someone for the cars previous owner and luckily not password protected).  I have sorted out the CAN DI communication between a toucan digital gauge and the G4X to make best use of the toucan with it's launch and anti lag switching. The ECU has got overrun fuel cut switched on so there is no theatrical anti lag style pops, bangs, flames and it can stay that way unless on the ALS switch.

My question regarding this post is if I was to add 3 rows of anti lag timing retard in the throttle position columns, apply a 50% anti lag fuel cut but then want to add 1-5% extra fuel trim in a box (let's say 0% throttle position @3500rpm, overrun),   what number would the 1-5% extra fuel trim be calculated from (would it be 1-5% of what is written in the main fueling map OR would it be from the amount that is left after the 50% cut is made.

Also as asked above is the anti lag fuel cut function done in a random cyclic fashion or across the board by shortening each injectors pulse width.

I hope that makes sense.

Ps I've only just started looking at pc link and the ECU settings in it so don't shoot me down, I might have misread some of the help info.

Link to comment
Share on other sites

2 hours ago, Evo6Webby said:

OR would it be from the amount that is left after the 50% cut is made.

A 50% fuel cut doesnt mean 50% of the fuel is removed, it means fuel is completely removed so there is no combustion at all for 50% of the combustion events.  Any combustion event that is not cut will get the normal amount of fuel.  

 

Link to comment
Share on other sites

34 minutes ago, Adamw said:

A 50% fuel cut doesnt mean 50% of the fuel is removed, it means fuel is completely removed so there is no combustion at all for 50% of the combustion events.  Any combustion event that is not cut will get the normal amount of fuel.  

 

Thank you for clearing that up Adam. That will definitely make a difference to the heat and half the impact on the valves, manifold turbo and downpipe. Is that done in the fashion that (let's say injector #1) injects but then does not inject when it is next supposed to and then does inject again on its next cycle.

Link to comment
Share on other sites

6 hours ago, Adamw said:

Yes, and the cut pattern is randomised so any extra stress is relatively evenly distributed as %cut and the operating conditions vary.  

Very good information, thanks.

Lets see how the test drive goes to see what difference it makes. 

Video from the first steps of setting it up, new video to follow with fuel cut anti lag at 50% and more timing retard.

Currently only changed the retard for 0% throttle from 3500-7000rpm (overrun)

Edited by Evo6Webby
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...