Tuning from scratch

[Jim Blackwood]

kur4o I wanted to run something past you before I get too deep into the VE table. I'm working on the area between 30 and 40 kPa and 400-2400rpm trying to get a stable idle for warmup. I took the approach of richening the VE table and leaving the open loop table alone. At this point the mixture is still just a little too lean to support a steady idle but I have increased the values in those cells to 2.8000 which your comments should lead me to believe would be way too rich. This points to there being another problem somewhere, the question is, where?

I have checked and double checked the injector flow rate. I flow tested the injectors myself on my own flow bench and they range in a tight cluster around 35 lbs at 40psi. I used an online calculator to convert that to 4.4 gm/sec and entered that value.

Can you think of any other thing that could possibly cause this discrepancy? I'd sure appreciate any leads you can give me.

Jim

[brian617]

Cylinder Volume.
Injector offsets.
Returnless VS Vacuum Ref. (Flow rate vs KPA)

[Jim Blackwood]

Please see if these figures look like they are within reason. I only changed the cylinder volume.

Cylinder volume is 712cc
EOIT Boundary: 585
EOIT: 230-500
Inj PW voltage adj: .06-9.68
Inj voltage correction: 1
Min PW: 1.277
small pulse threshold: 3.997

Couldn't find the returnless/vac reference but my fuel system uses a return and is referenced to MAP.

Thanks,

Jim

[kur4o]

The way you set the inj flow rate, requires constant 60psi fuel pressure.
Step 1 to fix this, remove the map reference to the fuel pressure regulator.
or Make inj flow rate constant across all ranges and leave the map reference.

I am not quite sure how the ve works in ls1 but it must have some max value that will be close to 100% ve. Looking at the values at the right bottom of the ve table will give you the max value the pcm can use. If you max the ve table the only way to tune will be increase the cylinder volume scalar and than rework the ve table.

Dont forget that all of this ve calculations are represented as airflow to pcm in g/s. Monitoring that value will give you a clue if you manage to change the values or they are capped.

Don`t tune warm up, there are some other adders for that purpose. Tuning ve table must be done on fully warmed engine with all the others turned off.

[brian617]

Couldn't find the returnless/vac reference but my fuel system uses a return and is referenced to MAP.

Thanks,

Jim

"Flow rate VS KPA" is how its listed in HP Tuners, not sure what it will be named in your XDF. Also VE table should be a whole number from 0-100 for instance the file I'm looking at ranges from 17-97

What injectors are you using?

[Jim Blackwood]

At the risk of sounding obtuse, how do you ever tune the ve table if you can't idle the engine? Seems to be a necessary first step for getting it up to operating temperature, I don't see an easy way around that. Any suggestions for initial cold enrichment settings and where to make them? I'm all ears, I'd love to hear your suggestions and will try them out straight away.

My injector flow rate/kPa chart only varies by .22 gm/s but I have changed it to 4.4 across all values. I can't see that making much difference, certainly not enough to fix my lean condition but that's done.

My FPR has a hose that connects to the intake plenum so that it maintains 40psi in reference to the intake regardless of vacuum or boost conditions. There is no other modifier to the fuel pressure. This is consistent with most return-type fueling systems and is completely independent of the engine controller.

The max entered value in my VE table is 2.3980 which is at 4800 rpm and 170 kPa. At 100 it is 2.3227@4400 rpm. I am also accustomed to using values from 1-100 but that doesn't appear to be used here so I'm trying to adapt. As a multiplier, 1 would equal unity in the formula, (does not change it) which also uses the injector flow rate and other factors. For my engine to require at least a 3x multiplier in order to idle suggests that there is an unbalance elsewhere in the formula. Not the VE table, not the injector flow rate. Some other factor has to be off by and be dividing the formula by approximately 3 or more. I need to find out and fix that.

Does anyone have the actual fuel calculation formula?

Jim

[brian617]

My injector flow rate/kPa chart only varies by .22 gm/s but I have changed it to 4.4 across all values. I can't see that making much difference, certainly not enough to fix my lean condition but that's done.

My FPR has a hose that connects to the intake plenum so that it maintains 40psi in reference to the intake regardless of vacuum or boost conditions. There is no other modifier to the fuel pressure. This is consistent with most return-type fueling systems and is completely independent of the engine controller.



Jim

With vacuum ref the "Flow rate vs KPA" should be a fixed number across the table which reflects the flow rate of your injector @ xx psi. I believe that's 45psi in the LS world? Some correct me if wrong.

Example, a 01 Silverado with a 5.3 engine has a value of 25.1 across the table.

[kur4o]

I suggest you run fixed fuel pressure at 60psi. It is also very likely that the fuel flow constant is higher than actual. The injectors might flow less than you thought.

Start lowering the values at the fuel flow table by 10% and see how it goes. When you remove the map reference the table should take that into account.

Your best bet is to start with some ls1 stock injectors with good stock data, and make initial tuning with them. That way a big unknown is removed from the equation.

The % of ve is derived by the ve table values and cylinder volume. If anyone knows the formula I can add it to the xdf. I will play with efi live to see if I can rip the conversion they used.


Ls1 intake is with equal length runners and there is no need for individual cyl corrections. It could be some of the cylinders running leaner than others.


The xdf tables looks weird with 170kpa tables. I wouldn`t trust them too much. You have 1 bar map that can`t read 170kpa or there is some scaling with 2 bar map used.

A complete write down of your setup might be needed with the origin of the xdf and bin.

[Jim Blackwood]

The injector flow rate of the stock '01 Silverado is 3.18 gm/sec. I flowed my injectors at 35lb/hr (4.4gm/sec) @ 40psi. Actual was 37.7 and below saturation flow values were as expected. I could jack up the fuel pressure but that seems like an artificial solution, especially when it was running fine with that fuel pressure and comparable settings on the other controller. (MS2)

If anyone can find out the actual formula it should be possible to pinpoint the problem using that. Until then I guess I can fudge the thing by lowering the injector flow value to offset whatever is causing the problem. It's funny in a way, that was my first impulse. Going full circle here so maybe that's a sign.

About that MAP value, yes I am using a 2 bar sensor. I changed the multiplier to account for it and rescaled most of the tables that use MAP. May have missed one here or there but I don't see why that shouldn't work just fine.

Logic would seem to suggest that if the VE has to be tripled to get enough fuel, then the Injector flow number should be divided by 3 to achieve a comparable result. That seems like a lot but it won't hurt me to try it.

Jim