Injector blues.

[Dewayne_S]

So I was running 30 lb/hr injectors and the duty cycle was in the high 80's to lower 90's when at WOT and above 5700 rpms. I never really noticed the WBo2 going lean so I didn't worry much about it.
A while back a almost new set of Siemons 60 lb/hr injectors became available for the right price and I jumped on them. Ever since I have had hell getting my tune back to where it ran as good as it did with the 30's. Start up and warm up are rich, if you try to drive before it warms up good it's very rich. AE does not exist for some reason, when I let off any at all it goes rich but all I have to is touch the gas and it's back where it needs to be. I took it to the track a couple weeks ago and when I would stage and stall up it would dump enough fuel to choke it down.

I'm not sure whats going on but I think I'm gonna put my 30's back in.

[RobertISaar]

sounds like you're having issues with DE, not AE?

Siemens come with a good injector characteristic sheet?

[EagleMark]

So I was running 30 lb/hr injectors and the duty cycle was in the high 80's to lower 90's when at WOT and above 5700 rpms. I never really noticed the WBo2 going lean so I didn't worry much about it.
A while back a almost new set of Siemons 60 lb/hr injectors became available for the right price and I jumped on them. Ever since I have had hell getting my tune back to where it ran as good as it did with the 30's. Start up and warm up are rich, if you try to drive before it warms up good it's very rich. AE does not exist for some reason, when I let off any at all it goes rich but all I have to is touch the gas and it's back where it needs to be. I took it to the track a couple weeks ago and when I would stage and stall up it would dump enough fuel to choke it down.

I'm not sure whats going on but I think I'm gonna put my 30's back in.

So you were spot on with 30 lb injectors and you doubled the size and are now having issues?

Yup I'd put the 30's back in... I'm not sure you could tune out that much extra fuel?

[Six_Shooter]

What code/ECM are you running?

$59 has been run with 80 lbs/hr injectors, so I can't see why other codes couldn't run 60's.

Are the 60's high or low-Z?

[Dewayne_S]

sounds like you're having issues with DE, not AE?

Siemens come with a good injector characteristic sheet?

DE and AE, when I try to pick up a little speed or pull a hill I'm not getting and added fuel and when I reach a point where it adds fuel it way too much.

So you were spot on with 30 lb injectors and you doubled the size and are now having issues?

Yup I'd put the 30's back in... I'm not sure you could tune out that much extra fuel?

You know, it sounded like a good idea at the time. not so much now.

What code/ECM are you running?

$59 has been run with 80 lbs/hr injectors, so I can't see why other codes couldn't run 60's.

Are the 60's high or low-Z?

I'm running 6e. I thought I could tune it out but I'm really sick of messing with it. High -Z according to researching the number on the injector.


Maybe I will start over fresh this weekend if I can find someone to drive me around so I can make adjustments.

[Six_Shooter]

Do you have a DMM? If so measure the resistance of the coil and let us know what you read.

How have you tried reducing fuel delivery?

Also AE itself will need to be reduced, because the asynchronous pulses are delivering much more fuel, that is not needed for the same amount of injector open time. So in addition to reducing fuel to get the normal load cells right, AE also needs trimming when going to larger injectors.

[EagleMark]

You know, it sounded like a good idea at the time. not so much now.

I hate when that happens! Right now I'm dealing with to much fuel, this is a rare problem! Down to teens at idle and 70.xx WOT and seems to be OK...

You know if your overloaded with fuel you don't need much if any AE, but man when you get close to Stoich it sure changes and needs AE...

[ony]

what ecm are you running? might be able to cut the pulse withed off set down,

[Dewayne_S]

AE was bad rich at first but I pull a ton out and now I can't find a happy spot for it. To add to this tuning issue several years ago I took a piece of 4" aluminum thin wall pipe and formed it to match the throttle body then put the guts out of the stock MAF sensor in it. Needless to say I no longer had an air restriction in that area. It took a little while to get the tune right but it was working really good before the injector swap. In my head I feel that the larger MAF lacks sensitivity of small amount of air flow changes and in turn the large injectors get little to no pulse change and I'm just not getting AE.

I did drop from 50psi back to 43psi fuel pressure when I did the swap.

I plan to start this weekend with one issue at a time and try to work it out. Start up/warm up will be first but we all know I get one shot a day at this.

ony, it's a '7165 ecm

[tequilaboy]

Siemens 60s can run acceptably, even in a stock displacement applications (350), but there are a few compromises with running an injector of this size. First step is getting the offset tables right. This can be done using by tuning the tables and monitoring blm values, assuming you already have a decent MAF calibration and AFR target. Next you need to determine the min pulse width that the injector will tolerate without misfiring. This is typically around 1.60 ms. Adjust all 3 min pw (min, default and min asynch) settings to the same value.

Note, when the min pulse limit is reached, the INT will be reset to 128 and the car won't go any leaner, despite what the calculated bpw indicates in the datastream.

In double fire mode, a min pulse width setting of 1.60 ms will likely be a little richer than stoich for idle, so you must disable the rich O2 error and accept the richness. Necessary compromise. In single fire mode, the min pulse width can be further reduced to allow a stoich mixture at idle. The injector seems to be more resistant to misfire in single fire mode and will tolerate a smaller overall pulse width since the offsets are only applied once. Running single fire is an option if you want/need a clean/stoich mixture at idle.

The issue with single fire mode is the transition to double fire. To get enough fuel in PE, double fire mode will be set on PE entry and reset next time the injectors are off (DFCO for example). This can be a rough transition from single fire to double fire depending upon where you are in the cycle when PE is entered, since the injector may have already delivered a full load of fuel for the next 4 stroke cycle. As result there is risk of a momentary hit of ~50% more fuel. If you can tolerate this extra fuel hit, single fire may be the way to go. I prefer double fire, despite the richness compromises.

The other compromise area due the the min pulse width is at light load and moderate rpm. Under these conditions, you will reach an rpm/load condition where the car will blubber due to the excessive fueling. This is even worse than a slightly rich idle. This occurs, for example if trying to cruise in a lower gear above 3,000-3500 rpm. To avoid, you can upshift sooner to avoid this speed load condition. Shouldn't be an issue for auto trans cars.

Other than these compromise areas, the injector should respond to normal tuning techniques. Be sure to limit the max asych pw to avoid overfueling in AE. Little things like adding some artificial load at idle (like constantly running fan at low speed) and minimizing idle rpm and detuning the spark advance will also help clean things up on the bottom.

[Dewayne_S]

It's been a while since I worked with my car but last week I removed the 60's and put the 30's back in. I uploaded the tune I was last running with the 30's it now runs as smooth as it did before I switched to 60.

Also, all these years I have ran in open loop since I never took time to install a heated 02 in the long tube headers. It's no installed and wired up. The BLM's are close enough not to worry much about more tuning at this time except for the fact that idle fuel goes nuts in closed loop with my 280/288 .570 lift cam. I will work with this issue soon.