Very low "Required Fuel" value required?

[forcefed86]

This is a 4.8 liter turbo engine drag car. Running 160lb injectors with AEM driver box and e85 fuel. (E70 when measured) roughly 700ish hp.

So my current injectors wont idle steady unless im above 1.5ish MS. Even with the required fuel tab at "1" I cannot accomplish this. I ended up setting this value to ".4". This allowed me to idle steadily at 1.6ish MS. Been running the car all season this way. I know its not "right" but I didnt know how to get around the issue.

Problem is Im out of fuel adjustment on my VE map. It is maxed out above 19psi. (VE value reads 255). My injs are no where near maxed out. Currently putting together a 6.0 litre motor to run next year. I will need to add fuel to my current tune. How can I get around the maxed out VE table issue?

Thanks!

[billr]

[pit_celica]

You are maxing out the VE table because of the low reqFuel. It's usually not a good idea to modify the calculated reqFuel. If your injectors requires at least 1.5ms to behave correctly but you still have too much fuel at idle, then, there is not much you can do. Your injectors are simply too big. For 700 HP, even on E85, 8x 1000cc injectors should do the trick. The other solutions is to find some other injectors that behaves nicely at low PW like the ones from Injector Dynamics (I've heard nothing but good things about these injectors).

Also, as billr pointed out, a msq and log would be helpful. Maybe you have some fueling variables that aren't correctly tuned (Gair, Gbaro, WUE) and that are removing some fuel and it could be why you are maxing the VE table.

Sam

[forcefed86]

MSQ attached. didn't have it available on my PC/Phone.

The injectors are racetronix 160's. I don't dyno my cars, so HP level is not certain. I go by trap and weight. The current 4.8 was just a spare engine to get me by the rest of the year. Earlier in the year I was trapping 159 with a 5.3 LS motor. Which put me over 900 flywheel. This winter I'b building a 6.0. So smaller injectors aren't' really an option.

Another member suggested I use the table switch function and have it RPM based? Is this a viable option? Does the required fuel field carry over between tables? If It did could I set up a my current ".4" required fuel in one map, then ahve it switch over to the other table with a much higher required fuel number?

Thanks for the input.

[jsmcortina]

Unless table-switching physically swaps out your injectors it won't achieve anything.

I would strongly suggest that you re-do the tune using the calculated ReqFuel number. You'll need to re-scale your VE table accordingly.

The resultant fuel pulsewidth won't change (hence my comment about table-switching) but the VE numbers will be more sensible and you won't run out of range.

James

[forcefed86]

Thank you, though even going from the current .4 to .5 resulted in the idle being too rich with my 4.8 engine. Regardless of what numbers I had in the VE table, I could not get the PW high enough to idle steady. I'll see how it does with the larger motor. maybe I'll have a little more wiggle room. The supplied dead times with these injectors was also odd compared to most of sheets I've seen. Can someone double check I have the injectors setup properly on my MSQ to match these injectors? I feel I have this setting is off quite a bit. I attached the PDF of the inj dead times. I wonder if I have the injectors setup correctly with the PWM current limiting? I'm using Low-z injs and an AEM driver box.



Thanks...

[billr]

A simple guess is that the injector dead-time is incorrect. Test yours with your drivers and your fuel pressure; vendor data isn't necessarily applicable. I am just guessing, I admit, but my perception from a lot of threads here is that idle problems with too-big injectors is usually related to dead-time being wrong. Yeah, "too big" on the injectors. Won't those eight 160# (170?) injectors flow enough for over 1500-2000 hp, even with E85/70? The MAT table may also be a problem, it has been "fattened" a lot from real life. There are a lot of threads/opinions here about what the MAT table needs to be, I won't get into that, but it is something to be considered.

[forcefed86]

A simple guess is that the injector dead-time is incorrect. Test yours with your drivers and your fuel pressure; vendor data isn't necessarily applicable. I am just guessing, I admit, but my perception from a lot of threads here is that idle problems with too-big injectors is usually related to dead-time being wrong. Yeah, "too big" on the injectors. Won't those eight 160# (170?) injectors flow enough for over 1500-2000 hp, even with E85/70? The MAT table may also be a problem, it has been "fattened" a lot from real life. There are a lot of threads/opinions here about what the MAT table needs to be, I won't get into that, but it is something to be considered.

Why is there a field for MS3 injectors and "Main board injectors"? Which should I be concerned with?




Depending on base pressure guys are seeing more like 1300-1400 on true E85. The BSFC on these LS turbo engines is pretty high. I picked up 2 barrels of E90 to try for next year. I'm guessing this motor may actually make close to 1200whp so I'm not wanting to drop inj. size. I think I could drop the base pressure a tad if this would help. Currently at 45psi. I'm also batch firing off the crank sensor alone now. I could setup the sequential fire without too much trouble. I altered my MAT table. It has has very little effect on the tune.

Which value on the injector sheet should go into the MS "Bank 1 Dead time"? .357? Or the opening/closing time of 1.27MS for the 4A driver? I did try all of these values in the "Bank 1 Dead time" field with very little difference in idle quality.

What should my current limiting be set to?

Guys running the Holley seem to have no idle issues running these injectors with E85 by adjusting the "Offset" and the "Injection Angle" (not sure how these apply to the MS3). I'd assume it's just a matter of setting up these injectors correctly. Would playing with the "injector small pulse widths" help any? Again this is a drag toy. I don't need it to idle perfectly. I was more than happy with the current MSQ's idle/driveability.


(meant to highlight the 4A values ignore the highlights)

[jsmcortina]

Why is there a field for MS3 injectors and "Main board injectors"? Which should I be concerned with?

I'd suggest you read section 4.10 on Injectors. The different outputs and wiring etc. are covered there.
http://www.msextra.com/doc/pdf/html/MS3 ... .3-57.html

James

[jsmcortina]

I just took a look at your MSQ.

Seems like you don't have sequential fuel or coil-on-plug enabled. Is there a reason?

Sequential fuel will almost certainly help idle and will allow you to adjust injector timing.
"Coil on plug" will run the coils as they are designed to run. Wasted-COP runs them at twice the speed, possibly building up heat.

Your MSQ shows that you have PWM current limiting set on the mainboard fuel outputs, but you aren't using those outputs. According to your settings, your injectors are connected to the MS3X outputs. (Via the AEM Peak and Hold box you mentioned in the first post.)

The Deadtime curve looks totally wacky also. The tooltip advises you that the 13.2V setting must be 100%. Yours is around 40% - so you are actually telling the ECU to use about 0.15ms deadtime which is a long way away from the datasheet numbers.

James

[forcefed86]

I just took a look at your MSQ.

Seems like you don't have sequential fuel or coil-on-plug enabled. Is there a reason?

Sequential fuel will almost certainly help idle and will allow you to adjust injector timing.
"Coil on plug" will run the coils as they are designed to run. Wasted-COP runs them at twice the speed, possibly building up heat.

Your MSQ shows that you have PWM current limiting set on the mainboard fuel outputs, but you aren't using those outputs. According to your settings, your injectors are connected to the MS3X outputs. (Via the AEM Peak and Hold box you mentioned in the first post.)

The Deadtime curve looks totally wacky also. The tooltip advises you that the 13.2V setting must be 100%. Yours is around 40% - so you are actually telling the ECU to use about 0.15ms deadtime which is a long way away from the datasheet numbers.

James

With all the motor swapping I do, It's easier to run batch fire. I am always changing between the 24t crank and 1 tooth cam or the 58t crank and 4t cam. Also the cam sensor locations are at different points depending on the year/motor. Some at the aft of the motor and some up front on the cam cover. Basically did it for simplicity. I'm either putting to and from the track or at WOT with this setup, so I didn't think it would matter a ton. I'll try to run sequential this time around.

I was under the impression I was to make the curve look like the supplied injector offset graph. So thats how I Set it up. I'll grab the factory setting graph1 curve and give it a shot.

Appreciate all the help!

[ashford]

i run these same injectors, they are a pita to get right. the graph shown is for a p&H drive that is goes into holding mode after a set time, others go into holding mode after amperage reaches a certain point.

i trick i found to do on ms3 is to set dead time to 1 ms and input the voltage offset into the curve, just move the decimal to the right 2 spots. ie if the dead time is .5ms at 13 v enter 50% for that voltage or .67ms enter 67%

my computer i tune with is at work but i can get you a starting point. and yes get your cam hooked up and use sequential.

[forcefed86]

i run these same injectors, they are a pita to get right. the graph shown is for a p&H drive that is goes into holding mode after a set time, others go into holding mode after amperage reaches a certain point.

i trick i found to do on ms3 is to set dead time to 1 ms and input the voltage offset into the curve, just move the decimal to the right 2 spots. ie if the dead time is .5ms at 13 v enter 50% for that voltage or .67ms enter 67%

my computer i tune with is at work but i can get you a starting point. and yes get your cam hooked up and use sequential.

Thanks, look forward to seeing it. Unfortunately I'm a ways away from having an engine back in and running. So I won't be able to get back with an update until spring.

[forcefed86]

Got the new 370” motor in and running. Broke it in on batch fire. Then played with the settings a bit. I was able to move the required fuel to .5 on the engine without it dying. I then moved the fuel to sequential mode. Saw no noticeable changes. I did still have my settings on 2 squirts per cycle. I’ll have to change that to 1 and see how much difference it makes.

Also had quite a bit of trouble getting the setting right for sequential COP. After changing the settings over to sequential it would backfire while attempting to start. Set it back to batch fire and and it ran great. Not sure what the big difference is there.

Never did get to see that tune Ashford? If you have a sec I’d sure like to look at your MSQ.

Thanks!

[ashford]

i don't know how well this one is tuned it is from my older laptop. it is a 383 sbf it runs mid 9's at 10 lbs, and a few squirley low 9's@152 at 15#. 160lbs racetronics injectors. i do have a 6.0 tune with #120's

[forcefed86]

Thanks! I'll give those injector setting a shot. Would be great to peruse the 6.0 file as well. Surprisingly few LS equipped MS setups.