Fresh .020 Over Shortblock And H/c/i, Inj, Maf Wont Stay Running

[Scurvilicous]

Hey guys, I recently got my fresh 5.0 back in my 94 GT and its been a very frustrating go since then.
my parts are as follow:

94 GT
5.0 bored .020 over
TFS 11R 190's
TFS track max stage 2 cam
TFS R-series intake 90mm
Comp HE aluminum RR's 1.6
255 LPH walbro pump
FR 47# injectors
90mm lightning MAF
UPR x pipe and flowmaster 40's
EGR and smog pump delete
AODE to T5 swap (from a 99 v6)
Quarterhorse W/ BE

I started out with an SCT chip from american muscle tuned for those parts, the car would start great but then rev like it was at WOT untill 3k RPM and then die completely, no sputtering. After some phone conversations and emails back and forth I was convinced they were useless and I ordered a quarterhorse. I set up a base tune using decipha's t4m2 tune from efidynotuning.com and went throught the steps to add my parts, but Iam a total noob, and tried posting on on eectuning.com to have someone check my tune out but got no replies. with the tune i made it cold starts decent, but it surges and dies after about 10 seconds. Then it just gets harder and harder to start it, eventually ending with it just firing up and then dying immediately, it seems like its VERY rich. if I try using the Stock tune, its about the same. still seems super rich and progressively gets worse to the point of just firing and dying. . Im in the process of installing a wideband to know exactly whats happening with the AFR. Im thikning i must have another problem other than the tune. any ideas would be appreciated. Ive pulled out the canister and EGR lines from the pasenger inner fender and the plug that went into the EGR is just hanging there, but its shut off in the tune. I can provide a datalog of a cold start where it runs for a few seconds if that would help.

The things I've attempted to troubleshoot already
-confrimed fuel pressure is 39.5 at the rail
-checked TPS voltage (Was 1.04 at closed throttle and swept smoothly to 4.75 at WOT)
-checked TDC #1 with rotor pointing at number 1 and confirmed firing order
-traced my vacuum lines and checked for leaks
-sealed my PCV connections to ensure no vacuum leak there

 

[stykthyn]

I would say pull codes but you've nixed the computer. Maybe @a91what can chime in.

 

[a91what]

Hmm I usually tune speed density cars. But if I was too guess....... maf transfer is not everything, did you re-scale the warmup tables for larger injectors? They input fuel based on the injector constant.

Recheck the maf transfer as well, unlike a "recalibrated" maf the lightning maf transfer does not directly correlate to injector size.

Do you have a usable wide band hooked up and can you view/log that data?

Next suggestion- burn it all and buy a ms then I could help you tune it from my livingroom.

 

[a91what]

Maybe @Gearbanger 101 and @addermk2 can help.

 

[jrichker]

Your injector and MAF sizes are OK for pressurized induction, but way out of bounds for a Naturally Aspirated engine. The engine is going to run pig rich until you resize the injectors and MAF to match the engine displacement.

Fuel injector sizing & injector photos

Revised 26-Dec-2014 to add statement about figures are for flywheel HP and not rear wheel HP

Injector HP ratings: this flywheel HP, not rear wheel HP.
Divide flow rating by.5 and multiply the result by the number of injectors. This uses a 100% duty cycle. These ratings are for naturally aspirated engines at the flywheel.

Example:
19/.5 = 38, 38 x 8 = 304 HP
24/.5 = 48, 48 x 8 = 384 HP
30/.5 = 60, 60 x 8 = 480 HP
36/.5 = 72, 72 x 8 = 576 HP
42/.5 = 84, 84 x 8 = 672 HP

The preferred duty cycle is about 85% maximum, so for a safety factor multiply the final figure times .85.

19/.5 = 38, 38 x 8 = 304 HP x .85 = 258 HP
24/.5 = 48, 48 x 8 = 384 HP x .85 = 326 HP
30/.5 = 60, 60 x 8 = 480 HP x .85 = 408 HP
36/.5 = 72, 72 x 8 = 576 HP x .85 = 490 HP
42/.5 = 84, 84 x 8 = 672 HP x .85 = 571 HP

Remember that the above ratings are at 39 PSI. Increasing the pressure will effectively increase the flow rating. Example: a 19 lb injector will flow 24 lbs at 63 PSI, and a 24 lb injector will flow 30 lbs at 63 PSI.

See http://users.erols.com/srweiss/calcpchg.htm to get the calculators used in these examples.

Here's the duty cycle explanation. Duty cycle is how much of the time the intake is open the injectors are turned on. The 85% figure means that for 85% of the time the intake valve is open, the injectors are spraying. The idea is that you want some percentage of the duty cycle left over so that you have some room to grow the process.

If you are at 100% and you need more fuel, all you can do is turn up the fuel pressure. That means the whole fuel curve from idle to WOT is affected. Maybe you are already too rich at idle, and turning up the fuel pressure makes it worse. If you had some injector duty cycle left to play with, a custom tune could use that where it is needed. That would not over richen the whole range from idle to WOT.

If you did turn up the fuel pressure, you might be able to change the injector duty cycle to get the air/fuel mixture ratio you want since the injectors will have extra fuel delivery capability.

With larger than stock injectors or higher that stock fuel pressure, you will need an aftermarket MAF that matches the injector size. The MAF “lies” to the computer to get a fuel delivery schedule that meets the engine’s needs and isn’t too rich or too lean. The best strategy is an aftermarket MAF and a custom tune to insure the best air/fuel ratio over all the RPM range.

Don't forget to increase the fuel pump size when you increase injector size or significantly increase the fuel pressure



Diagram courtesy of Tmoss & Stang&2birds

24# injectors are all you need, and a matching75 MM MAF would be a better match for the engine displacement



See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

 

[Gearbanger 101]

Do you have the ability to data log? Did you end up pulling codes?

FWIW, this is where @jrichker and I disagree. Those injectors and MAF can be easily tuned to run like a stock, but you must have the correct transfer function, injector slope, and breaker point programmed into the ECU.

 

[a91what]

For the record..... I have tuned a 1.6l L4 for daily driving, it has 70lbhr injectors in it. Ready for the turbo. It has no problem idling or driving...

The key is to find a happy medium where the injectors are at a 2ms pulswidth or more at idle. Anything lower and they have an erratic spray cycle. With very large injectors this can be achieved with simultaneous firing of all injectors.

 

[Scurvilicous]

Thanks for replying everybody, I'm going to sift through the information provided.

24# injectors are all you need, and a matching75 MM MAF would be a better match for the engine displacement

I thought that because I have the ability to change parameters with my QH now that i couldnt really have too big of MAF or injectors? Am i wrong?

Do you have the ability to data log? Did you end up pulling codes?

I cant get to the car untill tommorrow afternoon at the earliest. Yes I have the ability to datalog. I did not pull any codes. somebody had mentioned that i cant pull codes when I'm running my QH? is this true?

did you re-scale the warmup tables for larger injectors?

Im afraid I dont know how at this point, I dont quite understand scaling and when i set this tune up I pretty much used cookie cutter values found at efidynotuning.com. what i changed was the Engine displacement, MAF transfer, injectors low and high slope, inj. breakpoint. Inj offset. borderline spark table and crank PW.
Im going to attatch my tune

 

[Scurvilicous]

an experienced tuner with BE and QH said that there's nothing wrong with my tune, so I must be looking at somthing unrelated to the EEC here.

 

[jrichker]

@ Gearbanger 101
@ Scurvilicous
Right now your power output is similar to the 93 Cobra engine. You may have a bit more power, but not enough to warrant the size injectors or MAF you are running.

The 90 MM MAF is designed to work with an engine that sucks in big gobs of air at a velocity high enough to produce a stable MAF output. If that airflow drops below its design parameters, you will have an unstable system.
There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables. Changes in RPM cause the airflow to increase or decrease, changing the voltage output. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow.

The change in airflow across a 90 MM opening will be much smaller that the change in airflow across a 76 MM opening when similar amounts of varying suction are applied to them. That's where the MAF transfer function comes into play; it is supposed to be used to compensate for the differences in MAFs. The gotcha is that at low flow rates the change in airflow across a 90 MM opening is so small that there will be occasions that it does not measure the change correctly. Think about what a graph of voltage vs. airflow would ideally look like; it would be a 35° to 55° sloping line. Too steep a slope and the MAF runs out of voltage before it hits the peak airflow it is rated for. Too flat a slope and it fails to correctly detect changes in airflow accurately; that's where you are at now.


Injector sizing – injectors are sized in pounds of fuel per hour at a specified pressure, usually between 37-41 PSI. The chart I posted shows that 24 Lb. injectors are about right for your combination of mods.

What happens when you put too big an injector on an engine? The normal process is to play with the injector pulse width to shorten the time that an injector actually sprays. Since an injector is an electromechanical device, there are limits to what can be done. An injector will have a certain minimum pulse width and a certain maximum pulse width. Get out past these limits and things don’t work well. Put a big injector on a small engine and you may have problems because the injector’s minimum pulse width is wider that what the computer says it needs for the correct air/fuel ratio.
Some people will tell you to just turn down the injector pressure. That will work, but at some point the injector spray pattern becomes droplets of unatomized fuel instead of a very fine mist. Droplets of fuel don’t mix completely and the air/fuel mixture will be uneven in the air charge that is sucked into the cylinder. If the combustion chamber design causes a high swirl rate, the uneven air/fuel mixture may mix it up enough so that the engine may run without problems.

 

[Gearbanger 101]

@ Gearbanger 101
@ Scurvilicous
Right now your power output is similar to the 93 Cobra engine. You may have a bit more power, but not enough to warrant the size injectors or MAF you are running.

The 90 MM MAF is designed to work with an engine that sucks in big gobs of air at a velocity high enough to produce a stable MAF output. If that airflow drops below its design parameters, you will have an unstable system.
There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables. Changes in RPM cause the airflow to increase or decrease, changing the voltage output. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow.

The change in airflow across a 90 MM opening will be much smaller that the change in airflow across a 76 MM opening when similar amounts of varying suction are applied to them. That's where the MAF transfer function comes into play; it is supposed to be used to compensate for the differences in MAFs. The gotcha is that at low flow rates the change in airflow across a 90 MM opening is so small that there will be occasions that it does not measure the change correctly. Think about what a graph of voltage vs. airflow would ideally look like; it would be a 35° to 55° sloping line. Too steep a slope and the MAF runs out of voltage before it hits the peak airflow it is rated for. Too flat a slope and it fails to correctly detect changes in airflow accurately; that's where you are at now.


Injector sizing – injectors are sized in pounds of fuel per hour at a specified pressure, usually between 37-41 PSI. The chart I posted shows that 24 Lb. injectors are about right for your combination of mods.

What happens when you put too big an injector on an engine? The normal process is to play with the injector pulse width to shorten the time that an injector actually sprays. Since an injector is an electromechanical device, there are limits to what can be done. An injector will have a certain minimum pulse width and a certain maximum pulse width. Get out past these limits and things don’t work well. Put a big injector on a small engine and you may have problems because the injector’s minimum pulse width is wider that what the computer says it needs for the correct air/fuel ratio.
Some people will tell you to just turn down the injector pressure. That will work, but at some point the injector spray pattern becomes droplets of unatomized fuel instead of a very fine mist. Droplets of fuel don’t mix completely and the air/fuel mixture will be uneven in the air charge that is sucked into the cylinder. If the combustion chamber design causes a high swirl rate, the uneven air/fuel mixture may mix it up enough so that the engine may run without problems.

While I hear and understand what you are saying, I don't think his injector size, nor his MAF choice is anything that could be considered too far out of the acceptable range. After all, power adder cars that might utilize large MAF meters and injector combo run around just fine at idle and under vacuum during light/moderate throttle levels while no exceptional increase in airflow levels traveling through the meter, or greater demands for vast fuel amounts being demanded by the injector than a stock N/A engine is seeing.

When properly programmed to do so, you can run quite a large injector meter combo with the stock ECU and have it make them behave just like stock.

My last car was running a 90mm LMaf and 42lb/hr injectors while feeding only 281ci and it idled, drove and got as good of mileage as it did with the stock 19lb and 70mm unit.

There are guys running 60-80lb injectors in their cars that will lug right along at 1,000RPM are still pass emissions checks just like stock. Now granted, they're heavily modified to utilize their capabilities....WHEN NEEDED, but just putting around town isn't causing them to go into fits either.

Are big meters and injectors overkill in some cases? Most certainly. But that doesn't mean the vehicle can't be programmed to run just fine with them. The OP's car in this case is no different.

 

[a91what]

Yup. 50lbers and 90lmaf on my little 302 before going aftermarket ecu. Ran fine.

 

[A5literMan]

And the op is well over a 93 Cobras output. Inj are probably a little bit but isn't the problem IMO

 

[Grn92LX]

Your problem is simply a matter of dialing in the tune. Injectors/maf aren't too big nor will smaller ones "fix" the car. It needs to be tuned.

Your stalling immediately upon dart up issue sounds like it's lean on cold starts. Try adding fuel. I'm running 42lb injectors on my n/a car and had to add fuel in the cold temp menu in the PMS and also pull out cranking fuel during start up. As far as dialing in the WOT tune, you need a wideband and the car should like 32-34* total timing at WOT.

 

[Scurvilicous]

Thanks for all the input everybody.

I had not mentioned in the OP that i was advised by American muscle to re install my 19lb injectors and stock MAF and try that with my SCT chip. The issues were still there on the SCT chip and the stock EEC. That makes me believe that some other problem is hiding somewhere. The car ran great last year before i did all these upgrades as well. Also, decipha at efidynotuning.com reviewed the Tune on my QH and said it looks good, and is not my problem. Im fairly sure that he created the site and forum over there and runs a tuning shop and seems to be very knowageable about tuning with BE. I havent got a chance to do a datalog or install my wideband, and probably wont untill atleast this weekend. when i get that stuff done ill post a datalog of however long i can get the car to run.