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Turbo Tuning


Billman

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Is anyone using an SCT tuner? I have a fuel issue at low load. seems to be lean. I am still learning how to tune. Can anyone point me in the right direction?
 


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turbo91xlt

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Head over to turborangerforums.com Plenty of people there tuning with SCT.
 

Billman

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no thanks, but thanks for looking
 

turbo91xlt

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lol your loss then
 

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Are you using a wide band O2? If not, how do you really know it's lean or fat? It is obvious if it is predetonating, but other than obvious signs you won't know without a wide band O2.
Timing needs to be pulled when it's going into boost and fuel needs to be increased. I do not use SCT but a TwEECer. tweecer.com
Anything less than a computer tune for a boosted application is a band aid.
 

Billman

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at low load it is not in fuel control. Long term fuel trim is at 24 and short term is at around 10-18 only at loads below 25%. No wide band, but I am aware that I wont get it perfect without one. Knowledge of its leanness is from the O2 sensor reading .005V and fuel trim high. I would like to get the base tune and go from there. I just added bigger injectors and a larger MAF.
 

Billman

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The question should be which parameter should be adjusted to add fuel at low loads.
 

Billman

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I have asked these questions and more on TRF and received ridicule in lieu of answers so perhaps you are correct turbo91xlt my loss.
 

scotts90ranger

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I don't know what tables are available, the stock computer stuff has always worked for me so I haven't screwed with it...

What tables are available, and what are the indexes? Do you have to set up the ECM for the injector flow rate and the different MAF sensor? blindly changing parts and hoping it will work without much in the way of feedback sensors won't work out all that well. For light load situations where it should be in closed loop fuel control you should be able to go off of the narrow band O2 sensor and shoot for ~.45V. I do have experience tuning engines but it's always for emissions for marine and industrial engines that do not run mass air flow sensors, we just use speed density. Is the MAF too big to sense airflow at low speeds? You may have your indexes set up wrong for the sensor, or just the wrong combination of parts. If it is an option, figure out the area in the fuel table that you are low and increase it from there. Normally the closed loop fuel control takes the base fuel table and multiplies it by a value based on the fuel trim.
 

Billman

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Now if we can just find the base fuel table...Ok I believe the MAF transfer function has something to do with it but not sure how to manage that table. The combo is correct for my application. and that is: 1998 Ranger 2.5 with 5speed trans and 3.73 gears out back, the mods are a T3/4 stainless header with a TO4E turbo with integral waste-gate that is set for 8psi, plumbed through a 26x6x2.75 inter-cooler, the injectors are from a coyote 5.0 and the MAF is from a Lightning, the exhaust is 2.5 throughout and the cat is factory, of course I have modified the tune to reflect these changes and added some timing. The low load leanness is as seen through a Launch Bluetooth scan tool I have. I will probably do some data-logging but am still trying to get it to run well enough.
 

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I am tuning with Advantage III software.
 

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Each MAf has it's own unique tranfer in lbs or kilgrams of air per time and voltage returned by the MAF. The computer knows the airflow by the voltage returned. You got to get the MAF transfer and enter those numbers for your MAF for it to run correctly. The larger injectors need to be input too, so the computer knows what pulse length will give what amount of fuel. You enter a high and low number for the flow of your specific injectors.

When at Lower RPM, under load, when boost is coming on, the stock fuel table is going to be too lean. You got to add fuel, my 4.0 is at 12:1 fuel in open loop, under load at 1/2 throttle or more and around 2,200 rpm when boost starts. My fuel then quickly drops to 11.4:1 (that is for for 5400' altitude, should be more like 11:1). I dropped timing to 24 degrees around 2,200rpm with load/boost and drops to 21.

Eectuning.org has much info that may help you, Tweecer has a tuning forum specific to it on Yahoo. Hope this helps:icon_thumby: SCT seams to be more about selling tunes and keeping you in the dark than quarterhorse, moats, Tweecer which are more DIY.
 
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Billman

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Thanks, I have put in the MAF and the injectors. The engine is lean at low loads 24% or less. Once in boost ~ 2200rpm all seems ok. What can I tweek to get some more fuel at idle and up to say 25% load. There is a table that says Load with failed MAF; could this be the base fuel table? I have seen some Tweecer vids on you-tube; I could check them out on yahoo. SCT is definitely keeping me in dark, and I can find no one to write a tune for me...
 

scotts90ranger

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the base fuel table might be called the VE table, or Volumetric Efficiency as that's somewhat normal, I think one of the engine control systems we use at work uses that...
 

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Thanks, I have put in the MAF and the injectors. The engine is lean at low loads 24% or less. Once in boost ~ 2200rpm all seems ok. What can I tweek to get some more fuel at idle and up to say 25% load. There is a table that says Load with failed MAF; could this be the base fuel table? I have seen some Tweecer vids on you-tube; I could check them out on yahoo. SCT is definitely keeping me in dark, and I can find no one to write a tune for me...
Lo load, oh, Likely running in closed loop and the computer is trying to maintain a 14.64:1 stoic fuel ratio. A boosted engine needs to go into open loop fuel much sooner than an NA engine. The stategy a given computer uses often determines how yo can tune it. It likely has an Open loop Function which switches the engine from closed loop stoic fuel saving emission to Open loop fuel for performance. It is going to be a function which uses rpm or load vs throttle position. It is likely you need it to go to Open loop fuel sooner. My tune hits open loop by RPM vs Throttle position and I got it kicking in at 1/4 to 1/3 throttle. You may also adjust the base fuel table, which is what it goes to in open loop.
 


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