Does anyone with some firsthand experience know if fuel cut during decel significantly increases combustion surfaces wear do to the lack of oil/per-mix injection while the engine is still rotating? In other words, should we NOT enable decel fuelcut to ensure that oil continues to be injected in to the combustion chambers for lubrication purposes, or is the increased wear insignificant enough to make an argument for the associate fuel use reduction?

 

Carlos! I finally got my wideband (PLX M-300) hooked and I'm tuning away. I pm'd you with some questions a long time ago... I was also wondering about this too...I am getting about 160 miles a tank. As soon as I let off the gas it really dumps fuel. Like 12:2-13:3 afr's And $25 for 12 gal is killing me.

 

I seriously doubt our engines will notice the lack of oil/gas for brief instances.
But I think you'll find that the car will drive/feel better without using that function.
That's what I found anyway...

And about running real rich after backing off the throttle...
That can be tuned out by reducing injector times during high vacuum

Steve C

 

How lean should i make my motor run for those portions? I took fuel out, so much that I was seeing afr's of 19:1. At the same time I saw those afr's i heard popping noises in the exhaust. Could you be a little more specific about how to tune this portion of the fuel map?

Thanks,
-Ryan

 

Hey Ryan,

To control the off-throttle (lean) popping I leave off-throttle fueling at about 16:1. Any leaner and it become annoying to me. But it's this "wasted" fuel consumption and the possible resulting wear of cutting fuel completely that sparked this thread.

Also, when tune right (about 15:1 under mid vacuum in the 2000-2500 rpm range), your highway gas mileage can go way up. The last 300 mile trip I made, I got 21 mpg. Unfortunately when the the secondaries come on line routinely, I average more like 15 mpg (i.e. around town).

BTW, not sure I ever got your email as I was deployed to the Gulf for 9 months last year. If you still have them, resend.

 

During high vacuum during decel - I tuned to a lambda of about .85 (AFR of about 12.5)
I really didn't play a lot with this section of the tuning curve, but I didn't like it with fuel cut or very lean.

I think the fact that we can not run sequential injection is the biggest thing hurting our gas milage (and less than optimum low RPM power).

My dual webber carbs - approx. equal WOT performance gave me 20 to 26MPG during cruise depending on fwy conditions.
With the Haltech I get 15 to 19 MPG under similar fwy conditions.

What is your timing set at for cruise?
Mine is about 40 deg advanced at low vacuum (less than about 35 kpa?? (sorry, forgot the units)

I have a new thread concerning sequential injection possibilities with the E6X

Steve

 

In the early 70's the rotary Mazda's has approx a 30,000 mile life expectancy.
This was due to two problems.
1) Steel rotor housing surface and steel seals (not good)
2) No Oil injection.

They then "chromed" the steel surface of the rotor housing (steel on chrome is much lower friction) and added oil injection - the oil being stored in the porosity of the chrome.

I would not worry about no oil during decel only

Steve