To those running the 034 sic w/ the atx, where do you have the fuel cut set at (point where the secondary injectors start firing)

I had mine at 110 Kpa, and it bogged real bad off the line, dumping to much fuel to early...i just upped it to 120Kpa, and its a little better, but still bogs really bad.

Where do you have your secondaries starting coming on, and how is it off the line?

my setup, 270 primaries, 440 secondaries...feels like its just dumping too much fuel too early. how high can i set that fuel cut point safely?

tia-

With the car off see what the atmosperic pressure is in Kpa. Then figure about 7Kpa equals 1psi. So say your pressure is 110Kpa with the car off then that's what it is at 0 boost. And since you have 270 primaries say you don't want extra fuel until 3psi. So that's about 21Kpa. So 131Kpa is what you'd set the number to in that case. You just need to figure out how much boost those 270's can handle on their own.

Ok, with the engine off, the eic sees 135 kPa

that seems high, but makes sense as to why the car was bogging down as it entered boost

i just set the cut point at ~149 kPa, and its much better, altho right around 2-3psi, it still bogs a lil (when the 2nd injectors are coming on)

so, guess i shoud set that cut point a bit higher and just keep workin till i get a real nice quick transition into boost


Thanks Matt

also check your idle fuel pressure. i know Corbin has 252cc accel injectors and same goes for seconadies. and he told me he keeps his fuel trim a little leaner 5% about and his idle fuel pressure with 252cc is about 26-28psi.
good luck
Michael 99gs
HRC Stage 2 @12psi :D
Stage 3 process begins gathering parts for rebuild
2GNT Member #32

http://www.dreamwater.net/purplebeast

>also check your idle fuel pressure. i know Corbin has 252cc
>accel injectors and same goes for seconadies. and he told me
>he keeps his fuel trim a little leaner 5% about and his idle
>fuel pressure with 252cc is about 26-28psi.
>good luck


his idle pressure is 26psi w/ 252's? that doesnt make sense to me. the cars idle stock w/ ~45psi on 235's, and i idled at ~22psi w/ 315's...

i think my problem was with the fuel cut point, i assumed 100kPa was atmoshperic pressure, and thought having the fuel cut at 120kpa would have the secondaries coming on at around 2-3psi. Well, the eic was at ~135kPa with the motor off, so that means i was dumoing over 700cc's of fuel before the car ever even got into boost, heh.

right now, i upped the fuel cut to ~149kPa, and the transistion is much better, ill try bumping it up a tad more tomorrow to see how it much it improves, like Matt said, need to figure out the what the 270's can do on their own. once i have the car running well by butt-dyno, o2 voltage, and egt tuning at 15 psi, ill get on a dyno w/ a wideband to finetune it, maybe take it to 18psi if it looks good at 15psi...

his idle pressure is 26psi w/ 252's? that doesnt make sense to me. the cars idle stock w/ ~45psi on 235's, and i idled at ~22psi w/ 315's...

yup, i checked my email Corbins full idle vacuum fuel pressure is about 26psi. but this will vary from car to car.

i think my problem was with the fuel cut point, i assumed 100kPa was atmoshperic pressure, and thought having the fuel cut at 120kpa would have the secondaries coming on at around 2-3psi. Well, the eic was at ~135kPa with the motor off, so that means i was dumoing over 700cc's of fuel before the car ever even got into boost, heh.

yah, in the 034 thingy it says, 100kpa was a.p. but it varies from place to place. hehe

right now, i upped the fuel cut to ~149kPa, and the transistion is much better, ill try bumping it up a tad more tomorrow to see how it much it improves, like Matt said, need to figure out the what the 270's can do on their own. once i have the car running well by butt-dyno, o2 voltage, and egt tuning at 15 psi, ill get on a dyno w/ a wideband to finetune it, maybe take it to 18psi if it looks good at 15psi...
well i will get my manifold for my 8-injector setup in a few days, and i will drop it in sometime this week if i got time. i want to play with it till i drop my built motor in just in case. you know? just to make tuning etc a little easier and cut the noise down a little. i will drop my cleaned stock 235cc in my primary rail, and 420cc in my secondary rail.
well good luck man...

Michael 99gs
HRC Stage 2 @12psi :D
Stage 3 process begins gathering parts for rebuild
2GNT Member #32

http://www.dreamwater.net/purplebeast

I am running about 26 psi under vacuum (30-some static). This is with 252's in the primary location. That leaves me about 5% lean right before boost (LTFT +5%, STFT ~0%). Standard atmospheric is 101.3 kPa. But, it does change from place to place. I think I've got my "fuel cut below" set around 110 or so. I've found that it does help to set it a little high. Damping the pressure signal sent to the EIC seems to make a difference too. I think Jason had good results with the little damper (aluminum vacuum connector) that comes with the S-FMU. I made one from a spare brass vacuum connector and JB weld. Seems to help the transition...


Corbin

'95 ESI-T
HRC+FMIC+ETC...



Gimme fuel...Gimme fire...Gimme that which I desire

Yea, i remember reading that and i used the inline air resistor piece that comes w/ the sfmu

In s. florida, we are below sea level, so that explains some of the pressure difference

I currently have the fuel cut below set at 156kPa, ~3psi (the eic registers ~135.xkPa with the car off)

I really need to get a datalogger tho to see my fuel trims, i have a feeling the ecu is pulling a lot of fuel right now if your idling at a lower pressure with smaller injectors