Throttle body CFM VS engine Cubic inches?
I have a dodge 360 magnum. And the 600hp efi 30002. I chose that unit as I wanted timing control. The engine is all stock. So in Initial setup I chose 360 cubic inch and cam one. The afr learn was maxed out positive. I had fuel learn set as high as 60. And trims and afr learn would still max at 60%.
After thinking about carb cfm size for cubic inches. I was wondering if the fitech was to big and I was just getting to much air. I raised the cubic inches, I’m up to 480. It run a lot better. Trims are between +-5. And fuel learn is at 29, and that what I have it set at. So my question is, is it ok to set the cubic inches like that to kinda trick it?
today i checked for vacuum and didn't have any. with it set to 360 ci i turned off closed lope and messed with the cam1 table. I had to go to 120% before i could get a/f to match target a/f just at idle. Back to default cam1 table and set to 550 cubic inch i had to add about 10%. I seem to be getting way to much air, can figure it out. I am also have and issue where i go max lean on left hand turns only, make no sense. I need to get a fuel pressure gauge.
You may want to look at these threads. Maybe that's part of your issue:
https://fitechefituning.com/fitech-efi-tuning-forum-2/topic/bad-map-sensor/?part=1
Quote from tony-muscle on October 12, 2020, 5:14 pmYou may want to look at these threads. Maybe that's part of your issue:
https://fitechefituning.com/fitech-efi-tuning-forum-2/topic/bad-map-sensor/?part=1
I have, and mine was all out of shape. I cut the end of. But had the same issue. When i just crack the throttle i can see the fuel stop. I took apart the throttle body and 3 injectors were full of dirt and i have two filters installed. I clean them out and it got rid of the lean tip in. I still need to have it 200 cubic inches over to get it to run good. I checked for vaccum leak and exhaust leaks that was good, With it set like that it run better but and can not floor it from a stop it bogs right down.
With regards to cfm size, I'm led to believe that because a carby relies on venturi speed to operate correctly, if the throat is too big for the air pump (engine) to create low enough pressure (vacuum) below atmospheric, the venturi speed is too low to draw enough fuel, whereas with the wet EFI throttle body the fuel is regulated by the throttle position, it gets more fuel as butterflies open, directly opposite to a carby, enabling larger cfm EFI throttle bodies to be used comparable to carries.
Quote from ajax-1947 on October 12, 2020, 11:05 pmWith regards to cfm size, I'm led to believe that because a carby relies on venturi speed to operate correctly, if the throat is too big for the air pump (engine) to create low enough pressure (vacuum) below atmospheric, the venturi speed is too low to draw enough fuel, whereas with the wet EFI throttle body the fuel is regulated by the throttle position, it gets more fuel as butterflies open, directly opposite to a carby, enabling larger cfm EFI throttle bodies to be used comparable to carries.
That is what I was thinking, just wanted to make sure.
starting to wonder if I have a something wrong. Map sensor bad? Seems to read high. Log from last night line 1789 I tried to go full throttle from a stop, 50% throttle 100kpa, goes very lean
https://docs.google.com/spreadsheets/d/1vKPGoMEiaBRkQbJeFsd6Lr-1XfGPLiHhAO53jG1hQfM/edit
I would argue that the corollary is also true, that even though the fitech advertises only an 850 cfm like throttle body it can operate much higher than a 850 cfm carb, because it doesn't rely on venturis to meter fuel, but utilizes the mass air flow sensor, and as long as your injectors can handle enough fuel demand...
I was just told by them that the 30002 will be good for as low as 200ci.
I feel like I have a huge vacuum leak. But can’t find one
A huge vacuum leak would have the engine running extremely rich which would be evident by the appearance of the spark plugs, spraying starter fluid or whatever seems to make little difference as it is already over fueled, a smoke test is the surest method to use ( speaking from experience).