Required fuel: injector + fuel pump = different numbers?
 

Hello all,

Pretty nubby to tuning stuff. What seemed a simple question has really veered off in all sorts of unexpected thought processes. (specific questions at end)

Simple initial question posted to the fb group "miata megasquirt tuning" : Where does the info from photo one get into Tuner Studio? Also, I tried using the approximate values from photo 3 to set the curve and the car fell on its face. I dont have a log of this on hand but the car runs and idles ~ok with the default line that was on the tune when I started. That line is either default or what the tuner gave me during my previous N/A tune.

Google Doc link to tune file
https://drive.google.com/file/d/19A-...LjX_V2VsH4kgSg

1,2,3,4 are the cylinders that received the correlating inj
https://cimg1.ibsrv.net/gimg/www.mia...b241ff1230.jpg
Either this was the default line or this is what my tuner had used when he did my N/A setup last year before injectors and fuel pump
https://cimg4.ibsrv.net/gimg/www.mia...2dcd856135.jpg

This is what Flow Force has as instructions. When I used this instead of the above, the car wont run without a lot of throttle.
https://cimg5.ibsrv.net/gimg/www.mia...30ef8b51a0.png


By the end of the convo with the admin on that group, he was suggesting that my ~650cc injectors were actually closer to being 750cc injectors because I have a 190lph fuel pump. Id never read anything like this.
Either way, the fb group admin, likely well intentioned, had a Mr.Miagi approach and rather than speaking plainly or giving straight answers, spoke in confusing circles trying to get my mind somewhere else to understand. It only really served to confuse and frustrate me :)

When I installed the injectors, I updated the required fuel table with my injector size, & target afr of 14.7, Ive never seen anyone taking fuel pump into this consideration.


So.....
- What values, should I use in the required fuel table?
- Is the fuel pump a factor that changes the cc rate of the injectors? I wouldnt have thought so... not every vehicle runs the same base fuel pressure but the same injectors are offered for different platforms.
- Where is the info from photo one entered into TS?
- My car runs fine on the flat line from photo two, is it likely a case where this curve is wrong and the tune is supplemented elsewhere?
- I cant remember where I found the 1.12 value. It was what others have used. Is this where the info from the card comes in?


Thanks in advance for any help here. Getting my toes wet has lead to me falling in and drowning on this one O_o

Just scale your injector for required fuel. Assuming you already had tuned your car and your VE table was okay on stock injectors, this should get you very close. In this case, your required fuel should go down as you have larger injectors.

Fuel pump may have a marginal effect, but I didn't notice anything significant at idle. I have heard cases of an upgraded fuel pump overwhelming the stock FPR, but I did not experience this with my DW200.

You need to input the injector dead times into the dead time voltage % curve under fuel settings.

1.120 is correct for FF640's.

Thank you for setting my mind at ease. That FP bit specifically, was driving me bonkers lol.

He had also mentioned that with an NB I should potentially be using the 4 bar number rather than the three. So rather than the 1.12 use the 1.261

Pity this social distancing thing. Im only a 5 min drive from Maple Grove.

Sorry - mistakenly assumed you had an NA. Yes, if you have an NB, I believe your have a 4 Bar returnless system. You will want to use the 4 Bar table for your dead times.

Additionally, the 640cc rating is at 3 Bar, so you will need to compensate for this in your required fuel as you will effectively have 752cc injectors @ 4 Bar. This has nothing to do with the fuel pump, it has to do with your FPR.

All of this is explained on the FlowForce website in detail: https://goflowforce.com/instructions

Reading it again I see all of this, somehow I had missed it initially O_o. The adhd intensifies when tackling new things sometimes O_o

My mistake. Thank you for the responses!