With 3.91 LSD and 30# injectors I am seeing 16mpg for city driving. Just curious what mpg range to expect when running 42# injectors.
Thanks.
Anyone running 42lbs injectors? Question......
Re: Anyone running 42lbs injectors? Question......
Why would the mpg change?ecartoys wrote:With 3.91 LSD and 30# injectors I am seeing 16mpg for city driving. Just curious what mpg range to expect when running 42# injectors.
Thanks.
OK my fault for not providing more details.
30# injectors are maxing out well beyond 80% duty cycle. Engine is managed by MS with wasted spark.
I am assuming recalculating to 42# injectors will also require re-tuning hence possibility of change in MPG.
Just wanted to know what MPG others running 42# injectors are getting with their respective diffs. Very simple question.
30# injectors are maxing out well beyond 80% duty cycle. Engine is managed by MS with wasted spark.
I am assuming recalculating to 42# injectors will also require re-tuning hence possibility of change in MPG.
Just wanted to know what MPG others running 42# injectors are getting with their respective diffs. Very simple question.
Well, then your MPG will go way down...
The injector size has very little to do with the fuel economy, you could have 100#/hr injectors and at 10% duty cycle the fuel economy would be the same as 10#/hr injectors running at 100% duty cycle (it'd idle like crap, but you get the point). Unless you can find someone running the same power levels (not injector size) as you, it's damn near impossible to predict fuel economy.
The injector size has very little to do with the fuel economy, you could have 100#/hr injectors and at 10% duty cycle the fuel economy would be the same as 10#/hr injectors running at 100% duty cycle (it'd idle like crap, but you get the point). Unless you can find someone running the same power levels (not injector size) as you, it's damn near impossible to predict fuel economy.
Injectors can't supply higher than 100% duty cycle. When your EMS says they're running at say 110%, it's letting you know that in order to supply enough fuel for the spec in the fuel map you would need an injector with 10% higher flow rate. As a rule of thumb you shouldn't run your injectors over about 80% duty cycle for any extended period of time.
So even if you scaled your fuel maps for your new higher flow injectors without increasing power, you'd see an increase in fuel consumption (likely very small because you're likely only over 100% duty cycle in very extreme portions on your map). You should have noticed that your engine was running lean in those extreme sections of the map.
So even if you scaled your fuel maps for your new higher flow injectors without increasing power, you'd see an increase in fuel consumption (likely very small because you're likely only over 100% duty cycle in very extreme portions on your map). You should have noticed that your engine was running lean in those extreme sections of the map.
OK. Just came back from driving and readjusting the tune to 42# injectors after installing them this morning. Still running 12 PSI and with 250 miles of all conditions driving I am getting 16.5 mpg. It is a lot better than when I was doing the same kind of driving/tuning with the 30# injectors as I was getting 14s.
Now that the tune is settled in with the 42# I will check mpg again on the next 250 miles.
To answer your question on the duty cycle and AFR. MS log registered max of 118% duty cycle on full throttle full boost run. The time from over 80% to 118% was about 4 seconds long and all through that time the AFR was hovering where I have set it at 11.8 and never goes lean. The injectors were modified by FIC to spray consistently at high fuel pressure with 4 pintle style nozzle. Every time I hit above 8PSI with full throttle the duty cycle goes over 80% but never goes leaner than what I have set the AFR - 11.8.
Forgot to add, with the 42# injectors the VE table was reduced from above 6PSI with big reduction happening from 9PSI and up. This is done with both Autotune and VE Analyzer.
Now that the tune is settled in with the 42# I will check mpg again on the next 250 miles.
To answer your question on the duty cycle and AFR. MS log registered max of 118% duty cycle on full throttle full boost run. The time from over 80% to 118% was about 4 seconds long and all through that time the AFR was hovering where I have set it at 11.8 and never goes lean. The injectors were modified by FIC to spray consistently at high fuel pressure with 4 pintle style nozzle. Every time I hit above 8PSI with full throttle the duty cycle goes over 80% but never goes leaner than what I have set the AFR - 11.8.
Forgot to add, with the 42# injectors the VE table was reduced from above 6PSI with big reduction happening from 9PSI and up. This is done with both Autotune and VE Analyzer.