Forced open loop
 

Are there any benefits to be had from full time open loop on what's basically a road car engine , just mafless , tgv deletess ,
I can understand for maybe different cams , certain maf set ups , race motor type builds
But for mine is it worth looking into ?


Tony

I would of thought if the car was still being used on the street and under light load situations as well the Closed loop would be of benefit... But im only new to tuning!

If you are running speed density, particularly no as you will have AFR errors. Speed density using only MAP sensor and intake air temperature sensor is a poor method for estimating airflow. If you also have EMAP, coolant and EGT compensation with proven and tested models then possibly, then it might work.

If you have cats, absolutely not.

The easy way to answer for yourself experimentally is to look at your fuel trims during a typical journey from cold start involving cruise, stationary idle, with/without AC and power steering use and after hard use with heatsoak, plus warm start, all in a variety of weather conditions.

I see what you mean about Poor way to monitor air
No cats john but i think I'll put it on hold until Ive a real need or more knowledge
You've put a little doubt in my mind now
In your opinion do you think s/d is slightly less precise full stop
The only reason that leads me to think this is why do Subaru bother with maf sensor if they could just run map and iat
In simple terms ( you know I'm not that bright John ) what are the advantages / disadvantages
I only started running it because I modded my inlet and wanted spark cut l/c ( shallow I know )
And it gave me a reason to delete my tgvs

Tony

The only reasons to delete MAFs are if you can't get a MAF to measure the airflow you need, or your induction/BOV/compressor/intercooler/cams cause misreads or flow reversions.

MAFs as their name suggests measure mass air flow which is the value you are only estimating from SD calculations, and whilst a car can run very well using SD, certainly smoother than a MAF setup that is suffering from the problems above, it is not as precise or accurate as a well designed MAF setup, which leads to AFR errors which are unacceptable for modern emissions standards which rely on precise AFR control. There are emissions compliant versions that mainly fuel from SD, but mostly they use MAF compensations to correct the SD airflow estimate under steady state conditions. This gives the best of both worlds because an SD calculation gives a responsive estimate of air mass flow at the intake valves (ie air leaving the inlet manifold) but MAF gives a more accurate estimate of air mass entering the inlet manifold.

Here is a thread http://forums.evolutionm.net/ecuflas...t-success.html about the Evo IX SD conversion which runs to 48 pages but includes development of it and the issues, it was the second of three SD conversions I developed. Different issues arose during SD conversion of a MAF based Power FC on the Subaru. The GTR SD conversion didn't really have any issues. I don't know enough about the Subaru SD conversion you're using to know its specific foibles, but SD precision and accuracy are never as good as a good MAF setup.

I had a feeling maf was more accurate ( for emissions at least )
For the difference in real world (and my mapping ) would you have any concerns running s/d

No concerns but you can check for yourself by looking at your fuel trims.

Lol , we won't go down that route with my dodgy methods

Closed loop areas are some of the most challenging to get right with speed density, so you can trust your fuel trims there.