Hey all, i was wondering if anyone knows what effect putting bigger injectors in with a Map sensor will do, i know everyone does the MAF conversion and with good reason. its easier to tune, works better with everything. i know its time for new injectors, but when aftermarket 24lbs are cheaper than the OEM injectors with better performance its a hard call. My question is can the Stock map adjust to make use of the larger injectors? or is it a waste of money
Map Questions
- Thread starter moyer17901
- Start date
MAF sensor, not MAP.
And changing the MAF sensor is a old trick to "fool" the computer into thinking it's seeing less air than it really is to reduce fuel used by the larger injectors.
Today, in 2016, the proper way to install larger injectors is a tune, which can be pricey.
Stock injectors are good to about 300HP crank. If you aren't there, going to larger injectors is a waste.
And changing the MAF sensor is a old trick to "fool" the computer into thinking it's seeing less air than it really is to reduce fuel used by the larger injectors.
Today, in 2016, the proper way to install larger injectors is a tune, which can be pricey.
Stock injectors are good to about 300HP crank. If you aren't there, going to larger injectors is a waste.
I have an 87 5.0, i have most of the basic mods like the gt40 top end, mild cam, full exhaust, underdrive kit, delete kit,3.55 gears in rear. i just rewired the car front to back and just looking at ideas for my next step. When i am cruising and dump the throttle, i have crap power til high mid range rpm then it screams its almost a 3 second delay from foot to floor til it wants to really scream, i have literally done everything but the maf conversion and swap injectors for parts not replaced
Doing things to the MAP sensor won't get you any benefits with a Ford Speed Density EFI system.
If you change the computer's internal program you could run 24 lb. injectors with Speed Density. That would require a Moats Quarterhorse or Tweecer and some heavy duty studying to figure it out. Don't like to study? Then a custom burned tune done by a dyno run and a tuner will do the trick.
Speed Density uses Manifold vacuum (MAP), Throttle position (TPS) and RPM, & Air Temperature (ACT) to guess how much air the engine is pulling in. Then it uses all of them plus the O2 and ECT sensors to calculate the air/fuel mixture. It is dependent on steady manifold vacuum and minimal changes in airflow from the stock engine configuration to maintain the proper air/fuel ratio. Change the airflow or vacuum too much and the computer can't compensate for the changes, and does not run well. Forget about putting a supercharger, turbocharger or monster stroker crank in a Speed Density engine, because the stock computer tune won’t handle it. Every time you seriously change the airflow through the engine, you need a new custom burned chip to make the engine run at peak performance.
Mass Air uses a Mass Air Flow meter (MAF) to actually measure how much air is being pulled into the engine. The computer uses this information and inputs from the O2, TPS, ACT, ECT, RPM and Barometric Pressure (Baro) sensors to calculate the proper air/fuel ratio. It is very tolerant of changes in airflow and vacuum and tolerates wild cams, high flowing heads, and changes in displacement with minimal difficulties. Larger injectors can be used with an aftermarket calibrated MAF or a custom dyno tune. This makes it possible to use the stock computer with engine displacements from 302-408 cu in, and make many modifications without a custom dyno tune chip. Put a new intake manifold on your 331 stroker and the computer figures out how much more fuel to deliver without having to have a new chip burned to accommodate the extra airflow.
If you change the computer's internal program you could run 24 lb. injectors with Speed Density. That would require a Moats Quarterhorse or Tweecer and some heavy duty studying to figure it out. Don't like to study? Then a custom burned tune done by a dyno run and a tuner will do the trick.
Speed Density uses Manifold vacuum (MAP), Throttle position (TPS) and RPM, & Air Temperature (ACT) to guess how much air the engine is pulling in. Then it uses all of them plus the O2 and ECT sensors to calculate the air/fuel mixture. It is dependent on steady manifold vacuum and minimal changes in airflow from the stock engine configuration to maintain the proper air/fuel ratio. Change the airflow or vacuum too much and the computer can't compensate for the changes, and does not run well. Forget about putting a supercharger, turbocharger or monster stroker crank in a Speed Density engine, because the stock computer tune won’t handle it. Every time you seriously change the airflow through the engine, you need a new custom burned chip to make the engine run at peak performance.
Mass Air uses a Mass Air Flow meter (MAF) to actually measure how much air is being pulled into the engine. The computer uses this information and inputs from the O2, TPS, ACT, ECT, RPM and Barometric Pressure (Baro) sensors to calculate the proper air/fuel ratio. It is very tolerant of changes in airflow and vacuum and tolerates wild cams, high flowing heads, and changes in displacement with minimal difficulties. Larger injectors can be used with an aftermarket calibrated MAF or a custom dyno tune. This makes it possible to use the stock computer with engine displacements from 302-408 cu in, and make many modifications without a custom dyno tune chip. Put a new intake manifold on your 331 stroker and the computer figures out how much more fuel to deliver without having to have a new chip burned to accommodate the extra airflow.
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Rather than thinking about new injectors, you should really be pulling codes, performing the cylinder balance test and troubleshooting why your car doesn't run well with the setup you have now.
Also, what cam did you select? Speed Density has a reputation for being picky on cams. Depending on your selection, you may need to switch to MAF regardless.
so i tried to pull the codes as per http://sbftech.com/index.php/topic,2471.0.html and i literally get absolutely nothing not a blink, checked all the fuses and they are all good
LiquidStangs
Well-Known Member
"not a blink"... I've heard that pre-'89 cars didn't have a check engine light, or didn't blink it to indicate codes. Did you try the test light or meter methods?
Mine's an '89, so can't say from experience.
Mine's an '89, so can't say from experience.
mikestang63
SN Certified Technician
wait- are you SD or do you have a MAF? I highly doubt SD with that cam and no tune. Does the MAP/BAP sensor have a hose coming from the intake to it or is the sensor reading atmospere air/pressure?
a hose from the map goes to the back of the intake. Im fighting an uphill battle on this car, i bought it back in 04 and it has had issues after issues which i expected. I didnt realize the previous owner had randomly tapped every wire and just rigged everything up without covering any bare wires back up. i removed the entire interior, fixed all the wires back to factory and completely removed what was left of the BCM. The dash wiring is still an issue but im working on that, i have most of it fixed i think its mostly radio wires left. the engine runs great, starts instantly except when i do short in town drives, when i assume its flooding because it will crank forever and not start but smells strongly off fuel. after sitting for 5 min it starts right back up. i recently fixed that when i replaced the entire ignition system. I'm not clueless with all of this, I have a degree in automotive and diesel tech. and now i work on F15E jets and ive never messed with mid 80's mustangs. When it comes to anything new im fine or if you take it back to the 60's im fine.
Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.
Dumping the computer diagnostic codes on 86-95 Mustangs
Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.
Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.
Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.
Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.
Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.
If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.
The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.
89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.
The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.
WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.
What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems
Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.
Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.
Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.
Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.
Or for a nicer scanner see www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
Dumping the computer diagnostic codes on 86-95 Mustangs
Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.
Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.
Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.
Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.
Be sure to turn off the A/C, and put the transmission in neutral when dumping the codes. On a manual transmission car, be sure to press the clutch to the floor.
Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.
If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.
89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.
The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.
WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.
What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems. This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and driveablity problems
Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.
Dumping the Engine Running codes: The procedure is the same, you start the engine with the test jumper in place. Be sure the A/C is off, and clutch (if present) is pressed to the floor, and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.
Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.
Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10
Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.
Or for a nicer scanner see www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
86-89's don't have a check engine light, so no blinks.
You need to use a test light, or invest the $25 in an Innova 3145
well i have tried everything on the internet to check for codes and i get nothing. now im thinking that my ecu is no good, its acting like an injector is hung up but its all of them. i figured it was just because i had the neg terminal on the battery off for so long that it had to relearn the trim and everything but after half an hour messing with the throttle it really didnt get much better. i popped a fuse when i was trying to check codes, the black single wire next to the diag port was rubbed bare in the loom touching frame which explains the fuel pump running. its just one thing after another it seems
- Mar 2, 2015
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Just FYI...its not hard to convert your car to MAF. It would be a hell of a lot easier to get running. There's info all over the net. Convert to MAF buy 24lb injectors and calibrated pro M MAF and be done.... That computer may be fixable...open it up and see if the circuit board is burned. Info to fix them is all over the net, too.
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