I posted a while back about my plans on making the AFC read boost and adjust fuel accordingly. I got my pressure sensor yesterday. I assembled and wired in the unit today. The pressure sensor is behaving reliably and the AFC is accurately reading vacuum/boost pressure. I ran out of daylight today, but tomorrow I'll see if I can adjust fuel based on boost pressure.


Corbin
'95 ESI-T
HRC + FMIC
http://members.nbci.com/cbehnken/

this is a very interesting project. i understand the basics of what you're trying to do but i'm not sure i completely understand how the afc works. i know you're not doing it this way, but normally you would set low throttle and high throttle values. let's say for example that you set your low throttle values as follows:

1000rpm = -50%
2000rpm = -40%
3000rpm = -36%
etc...

now i'm guessing that the afc will average the values out to come up with the in-between numbers. like at 1500rpm it'll probably be -45% correct? ok then keeping those values, let's say you set your high throttle settings as follows:

1000rpm = -24%
2000rpm = -20%
3000rpm = -16%
etc...

the afc lets you decide what throttle position is considered 'low' and 'high' by the tps voltage right? so let's say you are driving with the throttle halfway between your set low and high throttle points at 2000rpm's. at low throttle it would be -40% and at high throttle it would be -20%. at the inbetween throttle position would it be -30%?

if so then tuning it your "fooled afc" way could be pretty accurate for ANY boost level at ANY rpm. i can't wait to see how it turns out. good luck and keep us posted.

LAST EDITED ON 22-Mar-01 AT 09:39 PM (PST)

WTG Corbin. This is really awesome. Puhleeeaaseee post pics!

Where did you mount this boost sensor? Oh yeah, are you going to retain your boost-senstive FPR? Will the presence of it interrupt the setup you're trying to employ?

Good luck man!
Keep us updated!

Jason
98' Eagle Talon ESi-T
Mitsu Super 16g Turbo(HRC)


http://springfielddsm.homestead.com/JasonsPics.html

Got a picture for ya. I didn't have to modify the sensor any. I picked one that was amplified and will compensate for changes in temperature. It's really perfect for the application. There is a little noise in the signal, due to pulsing in the intake manifold...but the output voltage doesn't dance anymore than the other AFC inputs. So the AFC must filter the signals some. The picture shows the sensor mounted in a small enclosure and wired. It uses the ground and supply voltage from the stock MAP...that gave me a very stable voltage to work with. I will still use a FPR to dip the pressure at idle...something like a 1:1 ratio. I don't like my Bell FPR ...I want a stock FPR to mess with. Can some kind OBDII person donate their useless stock regulator to me? I'll pay for shipping.




Corbin
'95 ESI-T
HRC + FMIC
http://members.nbci.com/cbehnken/

I'm OBD2...is the stock FPR the item on top of the fuel filter? If so you can have mine since i have the sfmu to replace it.

I asked for an OBDII person because their FPR gets replaced when they go turbo . I just realized that the FPR in OBDII cars may not be referenced to manifold pressure . Can you check if your stock FPR has a vacuum port on it? Thanks.


Corbin
'95 ESI-T
HRC + FMIC
http://members.nbci.com/cbehnken/

How would you use the stock FPR to tune down idle pressure?
isn't it like set at a certain number?


l e o n

so where did you order the sensor? :) I wanna get one too now!


l e o n

nope, the factory FPR does not have a vaccuum line. I think I threw mine away when I was cleaning out my car.

Have fun!

Actually,

the AFC interpolates the values between the set low and high point.

So if you set low(ie TPS 0.1) 5000 rpm at -50% and high(ie TPS 0.75) 5000 rpm at -10%, then if the AFC sees the TPS as 0.4, it'll adjust it to:

(0.4-0.1)/(0.75-0.1) * (50-10)% = +18.46%

-50% + 18.46% ====> -31.54% <=== at TPS 0.4

WTG Corbin! Did you have to do any modifications to the sensor when you hooked it to the AFC?



l e o n

LAST EDITED ON 23-Mar-01 AT 05:54 AM (PST)

Good luck with the project... If you want to see some really interesting stuff on the AFC and what it can do check this out

http://www.notabusinessracing.org/ubb/Forum6/HTML/000420.html

And yes, it is a joke.... you can't really do this with an AFC :)

Any update? :)


l e o n

I used a portable compressor and a bleed valve to apply pressure to the sensor and an accurate pressure gage. I recorded what the AFC read at each pressure point. The data is linear and follows the manufacturers specs. I'll do a few simple tests with the stock injectors, but I won't really know if it does everything I want until I put in the bigger injectors. I want to get my FPR issues resolved before I swap injectors. I hope to do this soon, but I've got other projects going too. Namely, a $25 Jumptronix clone and my senior design project (hydrogen powered Suburban). I've included a pic of both, just for kicks.




Corbin
'95 ESI-T
HRC + FMIC
http://members.nbci.com/cbehnken/

Damn sounds much better than nursing school.


Stan2gnt
Stan2va@aol.com
95 Talon ES-I-NOS but T soon!
http://members.nbci.com/FlyEsi/home.htm
You too can have a never updated site complete with old info and dated pics!

so what's the part # that you used? :)


l e o n

I was going to put together VFAQs for the pressure sensor and Jumptronix clone that would have all the necessary information...parts lists, ordering info, wiring diagrams. I'll give you the part #'s if you really don't want to wait for the VFAQs.


Corbin
'95 ESI-T
HRC + FMIC
http://members.nbci.com/cbehnken/

Thanks a lot Corbin.

Plus, your jumptronix clone looks better than the real thing!

I can't wait to see your VFAQ. PLease keep us updated on the pressure sensor stuff.

Jason
98' Eagle Talon ESi-T
Mitsu Super 16g Turbo(HRC)


http://springfielddsm.homestead.com/JasonsPics.html

How small is your jumptronix clone gonna be? I find the jumptronix a tad bit HUGE...

if you can manage to make it as thin as possible :), that'll be cool..then I can mount it above the rear view mirror! :D



l e o n

dude, where did you get the voltmeter at? I have a friend that is in need of one like that. Is it pretty fast?

have fun!

oh yeah what would the refresh be for your A/F clone? Would it be much faster than the jumptronix one?


l e o n