Did I ruin my injectors? AFR max lean for 15 sec after 8psi

[5.3LS10]

Hey everyone,

I think I got a little boost happy and might have hurt my fuel injectors. Combo is a MS3X on a 5.3L with a turbo.

I was keeping the AFR rather rich in the 10s as I learned to tune this combo. During the first day we got up to 14psi and the car was pulling very hard. We drove it like this for a couple weeks. I have started to run into a scenario where the car just stops pulling part way into 2nd gear and the AFR maxes out in the 20s for about 15 seconds and then comes back online.

While in the rush and excitement of getting the turbo setup together and running I did not pay enough attention to duty cycle....

Going through datalogs it was constantly going over 100%. (52lb injectors with fixed regulator)

Is there something that would explain why the injectors would shut down for ~15 seconds? Almost exactly every time in the data logs.

Since I noticed the duty was too high I have since turned down the boost pressure to around 8-10psi.

Any ideas?

I have uploaded the current tune as well as a couple datalogs.

Thanks,
Shane

[piledriver]

That will not hurt the injectors...
However, your pistons may not have liked it much...

[billr]

I kind of agree that high DC shouldn't hurt an injector; but I gotta ask: are these high-Z or low-Z? If low-Z, are you using a P&H type of driver?

[piledriver]

Do the drivers have thermal overtemp shutdown?

[5.3LS10]

They are ford racing 52lb high impedance injectors. Not sure who actually makes them.

http://www.cjponyparts.com/ford-racing- ... 4/p/INJ21/

I will upload some of the earlier datalogs with higher boost where the duty cycle is 120%+

I thought running over 85-90% was bad for the injectors.

[turbo conversion]

Is everything working okay at 8-10 psi or is the same thing happening like it did at 14-15 psi?

If it is okay I would think the injectors are okay, you just need larger injectors to run 14-15 psi.


David

[gjestico]

Going static for a while _might_ be hard on a low resistance injector, But High resisance units pull about one amp, I would think that whould be no problem to sustain for a while. Especially considering they have fuel flowing thru them to cool them. Test the resistance of each just to make sure.

Are you sure what fuel pressure you are actually running ? That link for those injectors shows them rated at 52 lb @ 39.5 psi. If you were to crank up your fuel pressure to ~60 PSI, They would flow about 64 LB. Good for about 700+HP.

Have you pulled a plug to check condition and gap etc ?

[5.3LS10]

Is everything working okay at 8-10 psi or is the same thing happening like it did at 14-15 psi?

If it is okay I would think the injectors are okay, you just need larger injectors to run 14-15 psi.


David

I am now seeing the issue at 8psi as shown in the datalogs, previously it only happened at higher boost levels.

Its jsut strange that it is 15 seconds almost consistently.

[5.3LS10]

Going static for a while _might_ be hard on a low resistance injector, But High resisance units pull about one amp, I would think that whould be no problem to sustain for a while. Especially considering they have fuel flowing thru them to cool them. Test the resistance of each just to make sure.

I will test the resistance this week.

Are you sure what fuel pressure you are actually running ? That link for those injectors shows them rated at 52 lb @ 39.5 psi. If you were to crank up your fuel pressure to ~60 PSI, They would flow about 64 LB. Good for about 700+HP.

Base fuel pressure is ~58psi but since it is a fixed regulator, under boost pressure my injector flow is running at a lower pressure (fuel pressure - boost pressure)

I verified pressure idling with a gauge on the rail but currently do not have a sensor connected into the computer (On my to do list).

I am running a "dead head" style single feed rail with a wix 33737 regulator/filter combo. I think I should first get a pressure gauge wired into the computer so that I can monitor fuel pressure. We have already upgraded the fuel pump from a 255 to a 450 walbro so maybe the regulator is causing issues?

Have you pulled a plug to check condition and gap etc ?

Last week I pulled all the plugs after seeing with very lean condition. Base of the porcelain was very black (it was running very rich for a couple weeks under boost) Plugs are TR6 gaped @ 0.028", seeing about 3 threads of color on the plugs so I think the heat range and gap seem to be fine. No specs on the plugs that I could see showing any sort of detonation.

[gjestico]

5.3 , Whats going on at ~375 secs into your "pull2" log there. Is that a run through the gears ? How many gears in that thing ? Or just a few throttle stabs ? . I think I see your AFR issue right at 379 secs ? Reading just pegs at 22.3 and stays there. I would be looking at an issue with the AFR gauge and/or input to the MS. Theres no way you would be making ~180 KPA MAP at 5800 RPM with the AFR at 20+.
Is it possible the AFR sensor is overheating and shutting down ?

[whittlebeast]

Figure out a way to check fuel pressure at WOT.

Andy

[turbo conversion]

When you looked at the plugs last week and they were black that is a rich condition not lean.

Were you having this same issue at that time or did it start after that?

I would look at the plugs again, if they are black then the sensor is not reflection the actual afr.

If they are white then it is actually running lean.

David

[5.3LS10]

When you looked at the plugs last week and they were black that is a rich condition not lean.

Were you having this same issue at that time or did it start after that?

I would look at the plugs again, if they are black then the sensor is not reflection the actual afr.

If they are white then it is actually running lean.

David

I thought the black would have been build up from the past couple weeks of an overly rich condition. Wasn't sure if it would show right away, I did swap out the plugs last week though so I will have to pull a few and check.

[5.3LS10]

Figure out a way to check fuel pressure at WOT.

Andy

I have a -6 inline adapter on my other car. Ill swap it out onto his and see what it shows.

[5.3LS10]

5.3 , Whats going on at ~375 secs into your "pull2" log there. Is that a run through the gears ? How many gears in that thing ? Or just a few throttle stabs ? . I think I see your AFR issue right at 379 secs ? Reading just pegs at 22.3 and stays there. I would be looking at an issue with the AFR gauge and/or input to the MS. Theres no way you would be making ~180 KPA MAP at 5800 RPM with the AFR at 20+.
Is it possible the AFR sensor is overheating and shutting down ?

this is a pass at the drag strip so the activity from ~350-365 is the burnout, and ~370-390 is a 1/4mi pass.


You are correct 379-395 is the window that the wideband was reading lean and misbehaving for pull2.

Pull1: AFR issue is from 402 to 417
Pull3: AFR issue is from 106 to 120

I know the wideband controller is not losing power because I was able to watch the status light on it during a pass and it stayed solid green the whole way(when it boots up it flashes for 10-15seconds). I suppose that does not rule out an issue with the sensor though. the car definitely seems sluggish and down on power when this happens though.

[billr]

"...under boost pressure my injector flow is running at a lower pressure (fuel pressure - boost pressure)"

I think you have that backwards, pressure across the injector is the nominal FP plus the boost pressure.

[5.3LS10]

"...under boost pressure my injector flow is running at a lower pressure (fuel pressure - boost pressure)"

I think you have that backwards, pressure across the injector is the nominal FP plus the boost pressure.

Only with a 1:1 boost referenced regulator does that hold true.

With a fixed pressure regulator it should be the difference.

Ex.the fuel side of the injector is at 60psi and boost pressure it at 15psi in the intake manifold so the 60 psi would be fighting against the 15psi on the other side of the injector with a net difference of 45psi across the injector

Ideally we should be running a 1:1 regulator but currently it is not setup that way.

[billr]

OK, I wasn't understanding what you meant by a "fixed" FPR. Are the injector PWs going to zero, or is it just that the engine seems to be going lean? Leaning is to be expected, of course, if your FP is effectively dropping.

[5.3LS10]

OK, I wasn't understanding what you meant by a "fixed" FPR. Are the injector PWs going to zero, or is it just that the engine seems to be going lean? Leaning is to be expected, of course, if your FP is effectively dropping.

The injector PW is around 20-24 at WOT. With the fuel pressure dropping I would be expecting the PW to keep increasing to try to make up for the injectors starting to flow less fuel with higher MAP levels as more fuel is needed under higher rpm and boost pressure.

I will get the fuel pressure sensor hooked up so I can check that out I just have a hard time believing it is running out of the same amount of fuel for the same amount of time after each pass. It seems to be part way through second gear on the data logs everytime..

Pull1: top of second gear ~6011rpm
Pull2: halfway through second ~5500rpm
Pull3: halfway through second ~5500rpm

Strange...

[whittlebeast]

You have to prove to yourself that the fuel is not starving. We could be looking at a fuel pickup issue. It could be a fuel pump with not enough capability to keep up. It could even be some sort of ignition issue. The trick is to find a way to prove things one at a time.

Andy