High Injector Duty Cycle while tuning w/WBO2

[PlayingWithTBI]

I just installed a WBO2 and hooked it up to my EBL Flash-2. After running some learn and flashes I see my injector DC is ~100% at 5200 RPM. Even though my AFR is a little rich, and I'm guessing after some more tunes it'll get closer to "Commanded AFR", do I need to do something to lower the DC? Right now I have a bored to 46mm TB with 18LB spring and the 155lph fuel pump.

[Kitch]

If you're hitting 100% duty cycle at 5200RPM then I'd say you need to up your fuel pressure.
Even if you lower your VE to lean back your W.O.T. AFR into the mid 12's your injector duty cycle will still probably be in the 90's.

[PlayingWithTBI]

Thanks Kitch, I added some spark and the VE learn jacked the DC up to 114% in 2nd gear @ 5125RPM. Any suggestions on an AFPR or should I try to get a bigger spring (maybe 22-25LBS)?

[brian617]

The late tbi big block 30# spring works great. In my experience the "18#" isn't very reliable, it was coil binding at 17.5#s and causing erratic pressure.

[PlayingWithTBI]

Thanks Brian, according to the EBL Utility calculator their flow will go from 71.8 - 92.7#/Hr so, I'm figuring my 114% DC will go down to ~88% (if it's a linear calculation) which looks to put me in the right range? Will the diaphragms hold up to that pressure?

[Kitch]

I've had a similar experience to brian617, my particular 18PSI spring was very close to coil binding at 20PSI and the pressure was a bit erratic at times, it was generally consistent while running but if you started up on another day it might have lost 1PSI and it might be back the next day. Dropping it back to 18 seemed to make it more consistent.
Another option to the big block spring is going to an external regulator http://www.gearhead-efi.com/Fuel-Injection/showthread.php?7655-low-BLM/page2
That might be my next change only because I didn't like my chances of finding big block TBI spring here in NZ.

[PlayingWithTBI]

Thanks again! I found this on ebay...

https://www.ebay.com/itm/GM-TBI-28psi-fuel-pressure-regulator-spring-Silverado-Sierra-Tahoe-Suburban-/251810001036

[brian617]

Thanks Brian, according to the EBL Utility calculator their flow will go from 71.8 - 92.7#/Hr so, I'm figuring my 114% DC will go down to ~88% (if it's a linear calculation) which looks to put me in the right range? Will the diaphragms hold up to that pressure?

I've been running that spring for 5-6 years now @ 22#s +/- with no problems. The spring was used in the 94-95 big block TBIs.

[PlayingWithTBI]

I've been running that spring for 5-6 years now @ 22#s +/- with no problems. The spring was used in the 94-95 big block TBIs.

I ordered the spring but still need a pressure gauge, does anyone have a setup (tee and gauge with fittings) they have used? Then, once I install the spring I guess I'll have to relearn my VE tables or, can I divide them by the same percentage I increase my BPC (flow increase in the calculator)?

[donf]

In my experience the "18#" isn't very reliable, it was coil binding at 17.5#s and causing erratic pressure. The 18# spring I got from ebay was not an 18 lb spring at all. Thats why I keep telling people to check their pressures. Mine put out pressures in the low 20's and even backed all the way down could only drop to 19.5. I am pretty sure most of them sold are just generic springs purchased in packs from Mcmaster Carr and there not that accurate psi wise.

[donf]

still need a pressure gauge, does anyone have a setup (tee and gauge with fittings) they have used? I use a regular fuel pressure gauge kit for automotive repair. I got mine years ago and it still works fine. The larger gauges are usually way more accurate than the small bubble gauges everyone likes to use. I usually just hook it in after the fuel filter and set the regulator pressure. Its removed before driving. So far I have checked it twice. It has no moved once set. When looking for a Kit look for the fittings like the TBI fuel lines have. That makes it easy. I purchase mine years ago when TBI was a new thing and most of the kits had the proper fittings included.

[PlayingWithTBI]

Thanks, I was thinking of permanently installing a gauge or Schrader valve just behind the TB so I don't have to crawl under the truck each time, I don't do bend-overs much anymore, lol.