ECMlink global setting?

[enriquez2000]

I tried to do the math but coming up odd... I have rc1200 on the way... says they flow 1090 at our 43.5 fuel pressure. What would my global for e85 be... I was thinking it should be around -38 or so but want to clarify here first.

 

[Type1DSMr]

For E85 take your injector and multiply by .67. So 1090 × .67 = 730cc Global (450/730)-1=-38
So yeah mathematically it checks out.

 

[steve]

I have rc1200 on the way... says they flow 1090 at our 43.5 fuel pressure.

43.5psi? That looks like a 1G in the avatar and while you CAN run 43.5 psi based fuel pressure they normally run less that that depending on if it's a manual or automatic.

DSMLink assumes the correct factory base fuel pressure for it's global offsets unless you tell it different.

 

[enriquez2000]

43.5psi? That looks like a 1G in the avatar and while you CAN run 43.5 psi based fuel pressure they normally run less that that depending on if it's a manual or automatic.

DSMLink assumes the correct factory base fuel pressure for it's global offsets unless you tell it different.

Im running 43.5 on my afpr for months now. Its a 93 auto so it was 43 stock.

 

[steve]

There is nothing "wrong" with running 43.5 psi but you need to account for it when calculating the global. DSMLink assumes a manual transmission configuration. I believe if you use the calculator in Link it will calculate based on the ECU type. I don't have any 1G logs here to verify against. Try looking at what global you get using 450cc and 43.5 psi.

http://www.dsmlink.com/wiki/ecmlink101initialchecks
Global fuel

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Go to the ECU Config → Fuel tab and check the global fuel adjustment slider. This one is a bit more complicated to explain simply because there are a lot of things you can do to your car's setup that will affect this value. These things include:

• Changing injector size (of course)
• Changing base fuel pressure
• Changing fuel type (gasoline, E85, etc.)

To help with this, there is a “calculate” button on the Fuel tab near the Global fuel adjustment area. Click this Calculate button and enter appropriate values for your specific setup. The following screenshot shows a “typical” FIC 850 configuration on gasoline with a 2G ECU.

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1G ECU will default to a different base fuel value (37psi). Adjust this only if you've installed an aftermarket fuel pressure regulator or you know your car is running some different pressure than the default.

http://www.dsmlink.com/wiki/fuelsettingshelp
Settings
The Global fuel and Deadtime adjustments are intended to be used mainly to compensate for injector flow rate and fuel pressure that differ from stock. They are applied at all times. There is also a secondary fuel scale and deadtime adjustment conditionally applied with Full V3 (see the ECU Config→AuxMaps tab). But you have to go out of your way to enable that, so it's not something we'll cover here.

Global fuel
The stock ECU assumes that the car is equipped with 450 cc/min injectors and a fuel pressure of either 37 psi (1G) or 42.6 psi (2G). As injector size is increased, the Global fuel adjustment must be made more negative. Reducing the Global fuel adjustment value to, say, -50% to compensate for 900 cc/min injectors cuts fuel delivery in half.

The needed Global fuel adjustment value may be calculated as follows:

FlowRateAdj1G = squareroot(BaseFuelPressure / 37)
FlowRateAdj2G = squareroot(BaseFuelPressure / 42.6)
FlowRateAdjEVO1-3 = squareroot(BaseFuelPressure / 42.6)
NewInjFlow = InjectorCCPerMin * FlowRateAdj
Adj = (100 * ( 450 / NewInjFlow ) ) - 100

Where BaseFuelPressure is specified in PSI and InjectorCCPerMin is the flowrate of the injectors at 43.5psi (the standard flowrate reference pressure). Some slight empirical tweaking of this theoretically-derived value may be needed to get actual air/fuel ratios to match what the ECU intends. Since the Global fuel adjustment value is a multiplier applied to the injector pulsewidth, altering it tends to change the actual air/fuel ratio proportionally under all conditions.

 

[enriquez2000]

on link with stoich at 9.8 , 43.5 injectors and flowing 1090cc it gives me a -42.9 but i got -38..

 

[steve]

Not sure what your asking?

If I have this right, DSMLink's calculator is saying that the global should be -42.9 but from your tuning you found that -38 ran best, correct? So why the difference?

There are several factors off the top of my head that could cause empirical results to differ from the theory:

The injectors could be flowing less than 1090cc/m. 1000cc/min in that same calculation gives -37.7

The actual deadtime of the injectors is longer than the data or what you have programmed. This will cause the "effective" injector pulse width to be shorter that expected and deliver less fuel.

Your MAF (or SD VE) could be off, again throwing the results off the calculations.

Your fuel gasoline-ethanol ratio could be different changing the stoichiometric ratio.

Your actual fuel pressure could be lower than measured. Either a base pressure or tracking manifold.

 

[enriquez2000]

i havent installed them yet.. i have pte1000 in right now but i am throwing these rc1200 in to test some things.. my math gave me -38 but link calculator says different. So which is correct? I know they may be tweaked anyway in the end but 4% is a big difference.

Also I guess while I am here with the given dead times of the injectors, do I just enter them number for number in DA if i choose to zero it out in the fuel tab?

 

[steve]

i havent installed them yet.. i have pte1000 in right now but i am throwing these rc1200 in to test some things.. my math gave me -38 but link calculator says different. So which is correct? I know they may be tweaked anyway in the end but 4% is a big difference.

Show us your math.

Also I guess while I am here with the given dead times of the injectors, do I just enter them number for number in DA if i choose to zero it out in the fuel tab?

I didn't look at the table to see if it was DSM specific but the DA table is for total deadtime at a given voltage rather than the delta from stock like the single value on the Fuel tab.

 

[enriquez2000]

For E85 take your injector and multiply by .67. So 1090 × .67 = 730cc Global (450/730)-1=-38
So yeah mathematically it checks out.

same math as this....

 

[steve]

FlowRateAdj1G = squareroot(NewBaseFuelPressure / 36.3)
NewInjFlow = InjectorCCPerMin * FlowRateAdj
E85FlowRate = NewInjFlow * 0.67
Adj = (100 * ( 450 / NewInjFlow ) ) - 100

So,

FlowRateAdj1G = SQRT(43.5/36.3) = 1.09
NewInjFlow = 1090 * 1.09 = 1188.1
E85FlowRate = 1188.1 * 0.67 = 796.03
Adj = (100 * (450 / 796.03)) - 100 = -43.5

Using 37 psi I get -42.9

 

[enriquez2000]

FlowRateAdj1G = squareroot(NewBaseFuelPressure / 36.3)
NewInjFlow = InjectorCCPerMin * FlowRateAdj
E85FlowRate = NewInjFlow * 0.67
Adj = (100 * ( 450 / NewInjFlow ) ) - 100

So,

FlowRateAdj1G = SQRT(43.5/36.3) = 1.09
NewInjFlow = 1090 * 1.09 = 1188.1
E85FlowRate = 1188.1 * 0.67 = 796.03
Adj = (100 * (450 / 796.03)) - 100 = -43.5

Using 37 psi I get -42.9

and in link using 43.5 in the calculator it came to that... this why im confused..

nvm... i think you meant 43.5 not 37

 

[steve]

No I mean in the first example I used the factory nominal base fuel pressure of 36.3 psi to come up with the FlowRateAdj for your 43.5 psi base.

Since Correction was higher than the DSMLink calculator, I decided to check my work. To see why I used the 43 psi base that ECMTuning must use in the calculator and applied to a 43.5 base the final correction matched the Calculator.

Your and Type1DSMr -38 correction math forgets to include the adjustment for a change to the base fuel pressure from stock. Which was the main point of my first two postings.

1G DSMLink is derived from the 1G Federal Manual Turbo code and a 36.3psi (or 37) base fuel pressure. If you run some different base you have to correct for that also.

Or you can realize that the factory 450cc injectors really flow about 417cc/min at the factory base pressure and then the math becomes (417/730) - 1= -42.9