AFC + missing link?
02-06-2004, 03:01 PM
#11
1.0 BAR
Join Date: Jun 2003
Posts: 444
Re:AFC + missing link?
Originally Posted by willahlborn
Originally Posted by TurboEF9
..again, almost.
The problem with using the missing link and the AFC is the AFC *needs* to scale the MAP sensor back, otherwise, your larger injectors will be flowing entirely too much fuel. It needs to see an untouched MAP sensor signal for the percent of scaling to be correct.
The problem with using the missing link and the AFC is the AFC *needs* to scale the MAP sensor back, otherwise, your larger injectors will be flowing entirely too much fuel. It needs to see an untouched MAP sensor signal for the percent of scaling to be correct.
Here is the example i'd like you to use (please don't take these percentages literally, this is just to illustrate my point)
This example will be with a turbo d15, stock wastegate at 8psi, dsm 450 injectors, a missing link, and an SAFC.
RPM: fuel correction: map input: boost:
1000 -40% 3v 1psi
2000 -39% 3v 3psi
3000 -37% 3v 8psi
4000 -37% 3v 8psi
5000 -36% 3v 8psi
6000 -36% 3v 8psi
7000 -36% 3v 8psi
again these numbers are not accurate; just to illustrate my point. Even with the map sensor reading no boost (limited to 3v by the missing link to prevent a CEL) the SAFC can still be adjusted by rpm to compensate for more fuel as revs, and therefore psi, increase. I guess this would only really work if you know exactly when and how your compressor reaches full boost.
EDIT:
the above example will basically be my setup in about a weeks time. I'll get it set up and running and then post some exact correction factors to prove that this works.
I had something very similar
but to tune up your VAFC as to have a proper ratio without using map output is very complicated.
First, you got to set the all ratios for Vtec engaged or not.
then maybe do some low throtle tests as well.
Once everything is good and nicely seted on the AFR wideband meter
then next day weather change and you have to go trough everything again.
Iam running 17PSI
I tried many ghetto way, one of the best is to get a bigger Map Sensor.
Thats my 2 cents
02-06-2004, 03:21 PM
#12
3.0 BAR
Join Date: Apr 2003
Posts: 2,260
Re:AFC + missing link?
Yes, but it's still not going to work.
The missing link will bleed off all boost, keeping MAP sensor voltage input below 3.0v. On top of that, scaling back your injectors to the optimum amount to run 450cc injectors reduces your fuel and ignition map size to half of it's physical width. The 3.0-5.0v is what the rest of the map is valued at. Missing link won't let you get that high. ...sheesh.. This discussion is over. :P
The missing link will bleed off all boost, keeping MAP sensor voltage input below 3.0v. On top of that, scaling back your injectors to the optimum amount to run 450cc injectors reduces your fuel and ignition map size to half of it's physical width. The 3.0-5.0v is what the rest of the map is valued at. Missing link won't let you get that high. ...sheesh.. This discussion is over. :P
02-06-2004, 05:37 PM
#14
1.5 BAR
Join Date: Mar 2003
Posts: 1,190
Re:AFC + missing link?
How in the world do the big block guys run these monster blowers on top of their V8s?? What type of fuel management do they use? I can't imagine it's easy, if they're carbed... :P
..becuase they have loping idle at like 400rpms. And Whitey is right, because the power increase is more linear, the fuel increase would also be linear, which would a function of the needle valve on the carbs.
..becuase they have loping idle at like 400rpms. And Whitey is right, because the power increase is more linear, the fuel increase would also be linear, which would a function of the needle valve on the carbs.
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