TBI Fuel volume delivery? are 5/16" and 1/4" fuel lines too small?

[shimniok]

FWIW, and I am late to the party, but I am running the stock feed/return hard lines. I've had no problem dialing in the VE tables and in fact have a bit of fueling to spare (max VE1+VE2 is probably 95 or so).

So, looks like I will be coming back to this thread among others when I get arond to running a WB. Whee. :)

[babywag]

Hoping I finally figured this out.
Tried a stock bin and started from scratch vs. the bin from my '88.
My BLM numbers were pretty low 110-120.
Seemed odd to me, and still not agreeing with how it felt when I drove it, and what the wideband was telling me.
Removing fuel was only going to make it run worse, because it wasn't running that rich, and actually lean in some places according to the wideband.

So, thinking to myself I'm missing something simple? but what.
Well, I'm running 15psi fuel pressure...duh!!!
I never adjusted the injector flow rates in the bin.

Changed them to reflect I'm running 15psi, and bam BLM#'s magically telling me what I already knew.
Showing more realistic BLM#'s now 126-135

I feel soooo stoopid now

[EagleMark]

There's another quick way to fix BLMs! Change Stoich AFR to what E fuel is, 14.13...

[babywag]

I don't think that would have done it in this case.

I had previously changed the bin stoich AFR value to 14.13, and was having the exact same issue.
Closed loop BLM#'s saying richer than stoich(contrary to wideband), PCM pulling fuel and going lean.
I could force open loop and get it to run fine and maintain whatever AFR commanded in tables.
Anywho tried that in March. http://www.gearhead-efi.com/Fuel-Inj...oich-14-13-AFR

Stock injectors ~61lb/hr, but increase the pressure to 15psi and they're more like ~71lb/hr.
61*sqrt(15/11) = 71.23
So changing the injector flow rate from 61 to 71 was it. One little setting.

Changing stoich AFR in the bin is a PITA, have to change all the other values/tables too.
Easier to just leave it @ 14.7 and just calculate using stoich.
Pretty sure that's how the code works behind the scenes?

I may say or type 14.7, but my brain is thinking 1.0.

All I know is this thing runs the way it's supposed to now, and the PCM is friends with the BLM#'s.

[EagleMark]

I wasn't disagreeing, you had found the problem and fixed it right. Thanks for sharing mistakes, it's how we all learn.

But changing Stoich is just that, no need to change all other AFR tables. Stoich setting is the start of all the other AFR tables.

[babywag]

So, yesterday got an email from Mr. Injector regarding the old injectors that were installed in this thing.
(I replaced them with new ones a while back)
Sent them in to cleaning/testing mostly out of curiosity.

After cleaning @15psi they only flow ~62lb/hr ~3% less BEFORE cleaning.
According to GM they should be ~61lb/hr @ 11psi.
@ 15psi they should flow more like 71lb/hr
sqrt(15/11)*61=71.23

So with .bin set to calculate VE based on 61lb/hr = injectors weren't even close to delivering that.
According to rough math since I don't have the actual pre cleaning numbers yet...
The injectors were only flowing ~56-57lb/hr @ 13psi.
Would explain why I had to add so much to VE tables, and why I was maxing out.
Would also explain why bumping my pressure to 15psi helped somewhat.

So lesson learned...just because the pressure is good/steady/etc. doesn't mean the flow is

[EagleMark]

3% difference if on both injectors is not bad! I've had increase up to 9% on one injector and 4% on the other, in the end they were the same. That is a big difference.

There's a lot of discrepancy in this area. In the end having both injectors flow max because of cleaning and being the same is key.

First is what GM rated them at, I've seen 11 to 13 and I have no idea which is correct? Since every TBI stock I've tested since 1987 seems to be at 12? A stock 5.7L engine at 12PSI and WOT runs over 100% injector duty cycle and some VE tables are over 100%, so there's barely enough fuel to handle a stock motor.

There is a fact of TBI injectors having a 10% varible do to production machining. Greg machined one apart and we can see why. I think this is where flow matched injectors came from.

Fuel pressure gauges have a HUGE difference. The cheap ones from summit that go under hood and the cheap harbor freight are horrible even if you can read them shaking. The under hood oil filled gauge is only accurate when cold, if it was accurate, they all seem to drop when hot. Even good quality gauges can have a sweep from 0-60 makes it not as accurate as one 0-15 or 20. I finally bought an expensive oil filled race gauge for my temp tuning fuel pressure setup and it matches three Snap On fuel pressure gauges at TBI pressures and MPFI pressures, it has a 0-60 gauge.

Then what fluid was used by GM for this testing? Is it same fuel as injector cleaning service? I know the fluid Mr Injector uses mimicks gasoline! I've spent a lot of time with him to get these dialed in because most machines are not designed for this low TBI pressure, they use a higher pressure for cleaning. That said we had this setup to where 5.0L, 5.7L and 7.4L injectors all came out just a little higher then what GM rated, so it is consistent.

Looking at all my injector reports from Mr Injector they have 2 results, 20 PSI dynamic and 13 PSI static. If yours were only 56-57 at 13 PSI that is almost the entire 10% and the worst I have ever seen! The worst I have even seen before were 5% short, most are a little over.

When I do a tune I do start with serviced injectors with results given. But if I am running out or room in VE? Pressure goes up!