056 | Over run fuel cut - Motec M150 (overrun flames)

We were discussing in the chat box about the alterations that would be needed to allow some crowd pleasing flames, or cylinder/rotor housing cooling on over run.

Initially overrun fuel cut would be deactivated, additional fuel would be added to the high RPM vacuum area from the attached picture, also some timing could also be removed in this area.

It was the complete opposite of what the webinar was aimed at but since the question was raised ;)

There are risks that can occur with going for flames...

This is the centre muffler off of a 4WD that was being used for some testing that didn't have ORFC enabled, it made some good flames and loud pops and bangs on the way though!

That's impressive!

pops and bangs are bad kids ;)

This is a quick way to reduce your exhaust back pressure though BlackRex, or find the restrictions in your exhaust system ;)

It is indeed!, also makes it a lot louder very quickly!

Reminds me when years ago I did my first VTEC Honda swap, When VTEC engaged I was like DAMN this VTEC is loud till I realized it was to much for my old stock exhaust and it broke the weld on the resonator clean off. LOL had to limp back home with a dragging muffler! Good times. =)

Multiple 'VTEC kicked in yo!' memes just went through my mind Tommy :)

Hey Andre,

Can you explain what "Overrun Initial Enrichment" is and what purpose it serves with respect to decelerating? I could see it serving the purpose of "Initially cooling" the combustion chamber; a useful strategy you mentioned using on Rotaries. Is this the desired effect? Or are there other considerations? Thanks for your time!

It is used to smooth the transition into over run, and also makes the engine less prone to stumbling when small throttle movements are made.

Makes sense, thanks for the input!

Wuts goin on guys. reviving an old thread to ask about ignition compensation during overrun

In the webinar, a "general" value was given for about -10 degrees. Im running an EJ25, with a corrections pulling 25 degrees from final ignition during overrun - this puts me @ right around anywhere from 5-12* atdc during on boost shifting, and with values btdc during low load conditions. what would be the effects/benifits/downsides of making adjustments to this value? Just looking for more info, thanks!

have you checked the settings are still in the ecu?

Thank you Chris. I actually saved the changes to my file and not to the ecu. Novice mistake. good looking out.

I wanted to add to this thread based on some of my findings playing with some of the new BETA firmware for the GTR and Huracan as I believe these changes will make their way into more firmware and am curious to get the HPA guys thoughts on this and make sure my understanding is correct. Essentially in the new firmware the pedal acts as Torque scaler and this is how I see overrun working on my GTR.

Pedal has to be 0%

1) Throttle pedal damper threshold - when torque is below this dampening of the throttle pedal begins and leads to overrun.

2) Overrun starts When torque pedal is less than overrun torque aim

3) Fuel cut starts when Torque Pedal plus Overrun torque threshold hits torque ideal correction

Adjust overrun torque threshold higher to enter fuel cut more quickly. Can also reduce throttle pedal damper filter to enter overrun more quickly.