Leaning out IDLE && Cruise - Tuning Forum

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Leaning out IDLE && Cruise
Friday, June 30, 2006 11:51 PM
I have made changes in Engine>Airflow>Idle && Low RPM (xxxx) and In Engine>Fuel Control>Multiplier Table (I forget the name exactly)

I changed values literally for hours today and either got no change at all, or the car would not turn on, even though after every single upload i make with hptuners my car does not turn on until i hold down the gas for a few seconds right where idle would be and it finially catches.... but other times it just didnt turn on at all....

What tables do i change?

sry if the paths mentioned above are wrong, hptuners is on my laptop, not this computer....

p.s. wideband either reads low 13's at idle and cruise and my changes either made the car not turn on, or made no change at all







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Re: Leaning out IDLE && Cruise
Saturday, July 01, 2006 12:12 AM
Are you having problems with your idlea that you are changing the idle VE table?





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Re: Leaning out IDLE && Cruise
Saturday, July 01, 2006 6:18 AM
inaccurate wideband?



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Re: Leaning out IDLE && Cruise
Saturday, July 01, 2006 8:11 AM
protomec - no, im pretty sure its working correctly because when i get into boost it richens up, and when i was tunning i accidently put my constant to the highest value, and my gauge was pined to 10 (highest possible value)

shifted - I am editing the tables in Engine>Airflow>General Airflow>Main VE> IDLE && LOW RPM Signal && Low RPM Double

I didnt touch Low RPM Coastdown or VE offset because i am not sure what it does

After that didnt work I tried messing with the Engine>Fuel Control>General Fuel>Injector Const. && IPW Multiplier vs. VAC

One weird thing i noticed is that with the scanner i can edit some things on the fly, and one thing i messed with was VCM Controls > Fuel & Spark > Spark Control > Minus > and I put that to 13 and my a/f's went into 14's and my car got noticeably louder

any ideas?



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Re: Leaning out IDLE && Cruise
Saturday, July 01, 2006 12:52 PM
Yeah, but why are you editing the idle VE table? Are you having idle problems?

VE Offset increases the entire VE table by that amount, its used so that numbers greater than 116 or so can be entered in the tables. Low RPM coastdown is when you are coasting to a stop at low TPS.

The "on the fly" stuff doesn't stick, so you are only changing that when you are using the scanner. As soon as you disconnect the scanner, it goes back to the way it was. If you changed your spark control to minus 13, you are retarding the timing 13 degrees, definately not a good thing as far as performance goes.





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Re: Leaning out IDLE && Cruise
Sunday, July 02, 2006 9:25 AM
if the VE tables are not the right ones to mess with for fixing my idle and cruise, then which tables are the right ones?

my problem is that im running air/fuel ratios in the low 13's high 12's when i am in park, sitting sitting at stop lights, and cruising around i wanted to get them to 14.7-15.1 but nothing i was changing worked... i am going to try again today, so i will be back on later to see if anone has any pointers... thanks



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Re: Leaning out IDLE && Cruise
Sunday, July 02, 2006 8:19 PM
Sounds like your injector constant is way out of whack.

-Chris-




-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
Re: Leaning out IDLE && Cruise
Sunday, July 02, 2006 10:16 PM
umm... that could be... ummm.... i am going to try and mess with that tomorrow i guess... i tried doing the tutorial on shifted's write up and it gave me a number WAY to low... lol... the car wouldnt even start....

i have 440cc's running 35psi... stock is 190cc (i think) at 55psi . . . . i forget the number i got, but it was .0xxxxx something so low that i couldnt get my car on....

but i could try lowering it in little increments and see what happens... i will update tomorrow!! thanks..



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Re: Leaning out IDLE && Cruise
Sunday, July 02, 2006 10:23 PM
Stock is 252cc, you need to adjust the numbers for fuel pressure before using them in the equation.





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Re: Leaning out IDLE && Cruise
Sunday, July 02, 2006 11:30 PM
i know, i used an injector flow calculator online to find out the new throughput but it still didnt work . . . i think i used 190 for the stock value though, that might have something to do with it i can try that tomorrow



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Re: Leaning out IDLE && Cruise
Monday, July 03, 2006 8:10 PM
What was your stock constant and what is your base pressure right now

I could work that out for you in 20 seconds.

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...

Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 9:05 AM
stock constant for my eco was .1750 i believe... after the calculations i got a really low number that didnt work, and now its at .20101.... the lowest number the car would turn on with... it might be way to high, as i didnt know that my car would not turn on for 50 attempts after making a fuel change with hptuners...

to bad you didnt live near by i'd let you figure it out in 20 seconds for sure!! i havent had time lately... but i will update either tonight or tomorrow... thanks guys



|Forged 8.9:1 Wiseco Pistons|Forged Eagle Rods|HPTuners|60trim|Tial Wastegate|
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Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 9:56 AM
Forgive me I don't know much about the eco fuel system.

190cc injectors? Are you sure? is that 55 psi base pressure?

The constant being .1750 sounds low for some reason... but going off of Ron's Equation I come to a new constant of: 0.0988

Hmm.

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 11:23 AM
interesting.....

i know the 55psi base pressure on the stock fpr is right, but i am not sure about the 190cc stock injectors, shifted mentioned 252cc a feww posts up...

i am going to try again with the calculations using the 252cc's



|Forged 8.9:1 Wiseco Pistons|Forged Eagle Rods|HPTuners|60trim|Tial Wastegate|
|Precision Intercooler|2.5" Exhaust|2.5" Charge Pipes|630CC Mototron Injectors|
|Stock: Fuel Pump, Transmission, Manifold, TB, Head, Head Gasket, Ignition, Suspension...|
Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 11:49 AM
It helps to know what psi the injectors are rated at, and what their size are...

Are you certain that was your stock constant?

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 12:19 PM
Acer wrote:

interesting.....

i know the 55psi base pressure on the stock fpr is right, but i am not sure about the 190cc stock injectors, shifted mentioned 252cc a feww posts up...

i am going to try again with the calculations using the 252cc's


Well, part of the problem is that the SIZE of the stock injectors are NOT rated at the stock fuel pressure... At 55psi they are putting out a bit over what stock is, I believe GM rates thier injectors at 48 PSI.

Ford, rates thier injectors at 43.5 PSI.





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Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 12:21 PM
stock fuel pressure = 55psi
new Pressure = 30psi

old constant: .17800, i just confirmed...
new constant - .20101... completely guessed number...

my new injectors are rated for 43.5 psi, and they are bosch green top 42lb/440cc



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Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 8:20 PM
And you're SURE the stockers are 190cc?

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
Re: Leaning out IDLE && Cruise
Tuesday, July 04, 2006 10:17 PM
i found a post that said 190. shifted says 252...

http://www.j-body.org/forums/read.php?f=40&i=66501&t=66039#66501

there is a post that refers to stock eco injectors as 190cc



|Forged 8.9:1 Wiseco Pistons|Forged Eagle Rods|HPTuners|60trim|Tial Wastegate|
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|Stock: Fuel Pump, Transmission, Manifold, TB, Head, Head Gasket, Ignition, Suspension...|
Re: Leaning out IDLE && Cruise
Wednesday, July 05, 2006 8:29 AM
Ok Going by Ron's 252cc then....

252cc @ 43.5 psi = 5.79cc per psi.

252cc @ base 55 psi = 319cc. (That sounds so wrong, are you sure 55psi is the base pressure?)

440cc @ 43.5 psi = 10.11cc per psi.

440cc@ 35 psi = 354cc.


As you can see, going from your #'s the idle won't have to be adjusted much if in fact your original #'s were correct.

Plug it into the equation.

New constant = Old Constant x (old injector size/new injector size)

New constant = .17800 x (319/354)

New constant = .17800 x .90112

New constant = .16040


Therefore your new constant, going by all the data you've given me, should be 0.16040

Try punching that into HPT and seeing what happens. Remember the higher the # is the smaller the injector is (as per Rons information).... so what you punched in was a LEANER injector.

Your car probably was being pulsed for more fuel out of your injectors because the PCM was expecting a much smaller injector... with the super low #'s you were getting the PCM was pulsing the injectors for not enough fuel, expecting a massive injector to be installed.... I'm by no means an expert, just going off what I've learned.

Good luck, I hope this works out for you!

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
Re: Leaning out IDLE && Cruise
Wednesday, July 05, 2006 1:03 PM
thanks for your help man!! I am going to definitely give that a try when i get home... the only thing that i am not sure about is the 252cc stock ecotec injectors.... i kno its 55psi stock... i saw the gauge before i had an adjustable fpr



|Forged 8.9:1 Wiseco Pistons|Forged Eagle Rods|HPTuners|60trim|Tial Wastegate|
|Precision Intercooler|2.5" Exhaust|2.5" Charge Pipes|630CC Mototron Injectors|
|Stock: Fuel Pump, Transmission, Manifold, TB, Head, Head Gasket, Ignition, Suspension...|

Re: Leaning out IDLE && Cruise
Wednesday, July 05, 2006 8:11 PM
So now that everyone is trained to think a 17 lb injector is a 17 lb injector, they need to be retrained to adjust 'em for fuel pressure changes, eh?

Here's something that might help.

http://go.delphi.com
Look up your injectors by make, model, engine, year. Get the specs. Flow is in lbs/hr, so to convert to cc/min multiply by 10.5. Pressure is in kPa, so to get psi multiply by .145038 .

So Delphi's information shows 252 cc/min @ 55 psi in the stock application. If your pressure is different

I won't promise that site will always be correct, but it has been every time I've used it.

GM injectors in the past were listed by flow at 43.5 psi. Ford injectors were at higher pressure. I think Shifted's got this backward. Recently GM has been increasing the pressure at the rail to improve atomization and emissions.

The injector constant represents a base amount of time the injector is on for to deliver a specific amount of fuel (I know SweetnessGT understands this). Bigger injectors mean smaller constants, or less time the injector is on. It may help to think about filling a bucket with a garden hose, which might take 2 minutes, or with a much larger fire hose, which may take a second or two.

Make sure the fuel pressure is read with the key on and engine off. If the engine's running the pressure reading will be too low.

Here's the numbers I get:

Your injectors @ 35 psi = 37.67 lbs/hr or 394.67 cc/min.
Original injectors are 252 cc/min
So 252/394.67 * .17800 = 0.11365

Part of the error in the calculations above was an incorrect scale for fuel pressure. Injector flow and pressure have the relationship new flow = old flow * (square root new pressure / square root old pressure). Obviously, this does not produce the same result as saying injector flow = 10.11 cc per psi, so new flow = 10.11 * 35. Here's an example of correct and incorrect flow ratings at different pressures with the 440 cc injectors :


New pressure Correct flow Incorrect flow
10 210.9638527 101.1
15 258.3768966 151.65
20 298.3479416 202.2
25 333.5631392 252.75
30 365.4001114 303.3
35 394.6772288 353.85
40 421.9277053 404.4
43.5 440 439.785
50 471.7295153 505.5
55 494.7540896 556.05
60 516.7537932 606.6
65 537.8544007 657.15
70 558.1578897 707.7

Re: Leaning out IDLE && Cruise
Wednesday, July 05, 2006 8:40 PM
maybe it is time to put the factory tune back in and start over. Change the constant from there, if it does not start, take it out and keep it running for 10-15 minutes, your computer should make some correct adjustments. That constant can be WAY off and the car will still run.


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Re: Leaning out IDLE && Cruise
Wednesday, July 05, 2006 8:47 PM


if i had my laptop, i would be walking outside right now!! Its at my buddies house... i going to try this tomorrow

thanks slowolej and sweetnessGT, i will try both and see what happens...



|Forged 8.9:1 Wiseco Pistons|Forged Eagle Rods|HPTuners|60trim|Tial Wastegate|
|Precision Intercooler|2.5" Exhaust|2.5" Charge Pipes|630CC Mototron Injectors|
|Stock: Fuel Pump, Transmission, Manifold, TB, Head, Head Gasket, Ignition, Suspension...|
Re: Leaning out IDLE && Cruise
Wednesday, July 05, 2006 10:54 PM
now is this where the short term and long term fuel trims come into play?

if i keep backing off the injector constant with small adjustments shouldnt I see my fuel trims get closer to -4 rather than -14



1989 Turbo Trans Am #82, 2007 Cobalt SS G85





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