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Forum nameTurbo/Nitrous Tech
Topic subjectWhat am I doing wrong?
Topic URLhttp://forums.2gnt.com/dcboard.php?az=show_topic&forum=8&topic_id=108877
108877, What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
I apologize in advance, as this will be a lengthy post.

98 Eclipse GS, 420a, T3/T4, FMIC, SFMU, Walbro 255, -6AN everything, FCD, 8 PSI WG, manual BC at lowest setting, Crower stage 3 cams, fully built bottom end, 450cc RCs

This thing wont idle at all. I realize with a huge cam idle will be terrible, but it wont run at less than 25% throttle. I tried setting fuel pressure to 40ish for initial start and it fired up, but ran horribly. The lower I go, the better it runs, but now Im in the 10-12 psi neighborhood with KOEO. I installed the lowest cal disk on the SFMU. Also, my KOEO fuel pressure leaks down immediately. No idea why. Im running -6AN supply line to a firewall mounted Edelbrock filter, then into the OEM rubber line that attaches to the OEM rail, fuel pressure test port Schrader valve removed which goes to a 100 psi gauge, then to the SFMU, and -6AN all the way back to the tank. OEM FPR and filter removed. As throttle is applied, the fuel pressure is actually decreasing to 0 psig.

FCD is wired up to the MAP sensor, but the green switched 12v wire isnt connected yet (I figured I would get the idling and driveablilty out of the way before worrying about cut). Could that be an issue? I applied 12v to it but no change. Though I havent checked the voltage reading of the FCD like the manual says to.

Turbo doesnt seem to be making any boost. Nothing on the gauge or anything audible. I can visually watch the comp wheel spin though. And Im getting grey smoke out the the wastegate exhaust port. Normal?
The WG, boost gauge, BC, and SFMU are all T'd into the three prong vacuum port on the intake. Is that an issue?

Wideband says it running wicked rich, 9.8:1 area. I think Ive got too much injector size, but Id appreciate it if someone could help out. This isnt my car, so time is something I dont have, unfortunately.

To sum it up:

Why is the fuel pressure leaking down?
What is the best fuel psi (approx.) with my setup?
Am I running too big of an injector size?
Why no boost?
Should I install an vacuum canister due to the cam size?

Any and all info will be greatly appreciated. Thanks, 2GNT!



108878, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
Forgot to mention the there is currently no exhaust on the car. Has the downpipe that came with the turbo kit with the wideband installed, but thats it. No oxygen sensor is on the car yet.
108879, RE: What am I doing wrong?
Posted by SilvrEclips, Dec-31-69 06:00 PM
Set base fuel pressure to 18-20psi. You are dumping way to much fuel in there.
108882, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
Thats the thing. I started at 40 psi, then 35, 32, 30, 28, 25, 23, all the way down to 11 psi. At 11 it will run ok at about 25% throttle. 0% throttle it dies immediately. And like a stated before, fuel pressure leaks down to zero with KOEO, and when running, it flucuates between 0 and 12 psi. Ive been reading that using injectors this large without Megasquirt causes these issues. Im considering going back to the OEM injectors to test my theory. But that wont cure the leakdown issue.

Also that doesnt tell me why Im not making boost. Ive read that these engines dont make boost while the trans is in neutral. That makes no sense to me, but its on here...maybe someone can explain that.

And lastly, there are apparently differing opinions on how to mount vacuum and boost lines. If anyone can clarify or post a link to a good diagram that would be outstanding.

I hate to be such a ####, and I have tried searching but theres several dead links, and hundreds of posts in the turbo and nitrous forum alone, which makes it pretty difficult.
108883, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
I now totally understand why Im not making boost. There isnt even any wheels on the car yet. Please refrain from hating.

But I really need to figure out my leakdown and idling issues.
108885, RE: What am I doing wrong?
Posted by SilvrEclips, Dec-31-69 06:00 PM
Yea you wont be able to load the motor enough to get boost in neutral. Try swapping the stock injectors back in and see if that helps. Im not sure about the fuel pressure issue. It should be holding pressure steady while the car us running. You can try to remove the vac line going to the SFMU and just set static pressure, the cams may be causing some fluctuation
108886, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
But what about fuel pressure before I even start the engine. I prime the pump, it reaches the desired target pressure, then immediately drops to 0 psi. It should reach the target pressure and stay there, correct?
108887, RE: What am I doing wrong?
Posted by SilvrEclips, Dec-31-69 06:00 PM
I am pretty sure mine would leak down once the fuel pump cut off. The SFMU never held pressure very long
108888, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
Roger that. So thats not an issue.

So basically everything is correct, except 450cc injectors are WAY too goddamn big for this app without SAFC or better?
108890, RE: What am I doing wrong?
Posted by SilvrEclips, Dec-31-69 06:00 PM
I wouldn't say so, I use to run 440cc with only the SFMU, later I added emanage to tweek the fuel in boost but it didn't need much. My base pressure was around 18psi and I dont remember which disc I used. It was one of the lower ones, 4:1 maybe
108891, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
...and you had deleted the stock FPR/filter combo like I have?
108892, RE: What am I doing wrong?
Posted by SilvrEclips, Dec-31-69 06:00 PM
Just the FPR not the filter
108893, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
The EGR is blocked off, and currently there is no jumper with resistor installed, but I dont think it would have that much of a negative impact. Thoughts?
108894, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
Ive decided to go back to original injector size for now, at least until break in is over with. This is a fresh build done by someone across the country, and Id rather be safe limiting myself to 7-8 psi until I know everything is going to last. I feel the OEM injectors will be easiest to get her up and running. Later on, a SAFC or the new MS will be had.

One last question though.

Someone told me that if I retain the OEM injectors, that the impedence needs to be changed to a high impedence. Can anyone clarify if thats true, and why?

Again, thanks so much for your help. I'd be lost without this site.
108895, RE: What am I doing wrong?
Posted by DarkOne, Dec-31-69 06:00 PM
Originally posted by mierze420a
Someone told me that if I retain the OEM injectors, that the impedence needs to be changed to a high impedence. Can anyone clarify if thats true, and why? Again, thanks so much for your help. I'd be lost without this site.


Stock injectors are high impedance.

I order for this thing to run right, you need a base fuel pressure of ~15psi and a working front O2 sensor connected to the factory ECU. The ECU can't trim fuel if it can't read the A/F mix, and with no front O2, it dumps fuel as a failsafe. No amount of SFMU adjustment is going to get you to a reasonable idle on the stock ECU without a front O2 sensor.
108898, RE: What am I doing wrong?
Posted by mierze420a, Dec-31-69 06:00 PM
1000 thank you's for all the info. I welded an additional bung to the O2 housing for a front oxygen sensor. Tried the 450's again with the O2 in just for kicks. Still pig rich, even at extremely low psi, as I expected it to be. So the OEM squirters went back in. Set it to factory fuel pressure and it idles quite nice, considering the cams. Idle AFR is 11.7:1. Didnt run it very long because my oil feed for the turbo is leaking (the fitting was crappy). But it idles, which means once I install the exhaust later this week, I can street it and start adjusting rise rates and all that jazz. Again, I cant express how grateful I am for the help. You guys are very professional.
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