Heads up for FAST 90/90 owners.

[ArKay99]

Nice job and thanks for the story! Once again starting with the basics pays off. I am learning with this tuning stuff that too much thinking can ruin the tune! During my quest to learn tuning I have read and disected so much stuff that it had drove me nuts. After slowing down the thought process it all started to make sense.

Again the VE is the foundation of it all and needs to be as close as it can get. Keep us posted on how the car continues to act!

Howard

I sure will. I'll probably come back here shortly asking how to fix something I noodled up. A little knowledge can be dangerous , but I move slowly, one param at a time.

[joecar]

...it's validation for the REQUIREMENT to have a solid VE table as the basis for your tune...

[frodo84]

Originally posted by Arkay99 "I don't see how starting with 28lb injectors, then switching to 30lb injectors would make it easier to dial in. I went with my old 28lb setup and when I did my h/c I put the 30lb injectors in and calculated the table from the flow rate then put the tune in."

I guess I thought it would be one less thing to do when initially firing up the motor with new heads/cam, intake and ported tb, larger MAF, etc. Maybe not, that's what I'm doing here, trying to learn. Thanks for your help!

[ArKay99]

I guess I thought it would be one less thing to do when initially firing up the motor with new heads/cam, intake and ported tb, larger MAF, etc. Maybe not, that's what I'm doing here, trying to learn. Thanks for your help!

I don't know how much help I am, I mostly echo what I've learned from those before me and a little of my experience. I don't know if you know the formula for scaleing injectors, so at the risk of being redundant here is the formula I use.

From RC Engineering:
       __________________
 \    /  New Fuel Pressure
  \  /  --------------------     X       Injector Flow Rate                
   \/    Old Fuel Pressure

In order for this formula to work you have to know what fuel pressures are involved. There has been some controversy as to what fuel pressure Ford uses to flow the SVO's. Some have used 43.5psi, and some have used 39psi.
I used 43.5psi for mine and it worked out fine, i.e. no weird VE table numbers to make up for inaccurate IFR values. At least once I figured out what I was doing with my 'SD' tune.

So I set my table like this:
My injectors came with a flow sheet and the middle value was 30.597lbs/hr.
I assumed 43.5psi for my old pressure and 58psi for my new pressure and plugged the values in.

So I got: sqrt(58/43.5) * 30.597 = 35.330372....lb/hr
When I convert that to kPa and grams/sec to fill in the table I get:
sqrt(420/315) * (30.597 * 0.125997881) = 4.4515520... grams/sec
the (0.125997881) is a factor to convert lbs/hr to grams/sec.
the value 4.4515520 goes into the 0 cell in the IFR table.
Then for 5kPa in the table which is 5kPa VACUUM I add 5kPa to the 420kPa value for: sqrt(425/315) * (30.597 * 0.125997881) = 4.477970....
and I fill the table with each result of incrementing the 420 and adding the next kPa value to it until it's filled. That will be your flow values. I tried it with the stock values and they were very very close. Although air pressure is standard atmosphere = 101325 Pa = 101.325 kPa I used 105kPa as 1 atmosphere because that's how the table is laid out and used 4bar as the multiplier for 58psi and 3 bar for 43.5psi.

[joecar]

That's the correct calculation , what you did can be expressed as (for unreferenced regulators):

flowrate = R0 * sqrt((FP + BARO - MAP)/P0) = R0 * sqrt((FP + VAC)/P0)

where:
FP = fuel pressure measured at rail
P0 = injector's rated pressure
R0 = injector's rated flowrate

i.e. the pressure term is the absolute pressure difference across the injector;
(during flow testing/rating, the injector has BARO on each end,
so the pressure difference is (P0 + BARO) - (BARO) = P0).


This is what the spreadsheet calculates.

[ArKay99]

That's the correct calculation , what you did can be expressed as (for unreferenced regulators):

flowrate = R0 * sqrt((FP + BARO - MAP)/P0) = R0 * sqrt((FP + VAC)/P0)

where:
FP = fuel pressure measured at rail
P0 = injector's rated pressure
R0 = injector's rated flowrate

i.e. the pressure term is the absolute pressure difference across the injector;
(during flow testing/rating, the injector has BARO on each end,
so the pressure difference is (P0 + BARO) - (BARO) = P0).


This is what the spreadsheet calculates.

OMG, there IS a spreadsheet on the conversions tab. I could have put that into the spreadsheet, created a new one, and been lazy and had EFILive do it for me. The good thing is, it wasn't all that hard. Like I said, even though I've been using EFILive for a while, I'm still a noob in lots of places.
Thanks for the tip.

[joecar]

This is the link to the spreadsheet on RHS's tuning website: http://www.allmod.net/hpt/injectors.xls

Edit: the spreadsheet is good, but now that you've done it manually ("handraulically"), you've learnt valuable knowledge.

[TAQuickness]

This is the link to the spreadsheet on RHS's tuning website: http://www.allmod.net/hpt/injectors.xls

Edit: the spreadsheet is good, but now that you've done it manually ("handraulically"), you've learnt valuable knowledge.

I like that