Lean, Or Rich?

louieb · Sep 20, 2012

Hi, i was looking for a solution to making adjustments on the car to raise, or lower the fuel mixer.

the car is a 1986 mass air converted 30lb injectors 42 1/2 lb fuel pressure.

i am pretty sure the only way to take control of the fuel mixture is to have a wide band o2 sensor, and a pc.

i have a kit from innovate motorsports, but i did not install it. not sure i even will. i may sell it cheap..

what could be done to lower hydrocarbons? the cats are removed, and it puts out 1800 part per million. pass is like 300. lol but still thats a lot of fuel waste.

i just hoked up a msd digital 6al, smoothed out everything nice. could there be some misfire in there even after the tune up?

would a lower fuel pressure lean it out a bit? say 36 lbs, not 42 1/2? thanks..

ThatBear · Sep 20, 2012

It might make it leaner, might also starve your engine of fuel. Why not just get some high flow cats? What state are you in?

GroverDill · Sep 20, 2012

base fuel pressure should be about 38 psi no vaccum

Noobz347 · Sep 20, 2012

You're not going to lean/enrich your Air Fuel Ratio (AFR) with a wideband meter and laptop. Those two pieces of equipment will only TELL YOU what the AFR is and allow you to data-log it. That is all.

Also...

Changing your fuel pressure isn't going to get you where you want to be either. The AFR is commanded by the EEC. For example: Let's say you're running your fuel pressure where it's supposed to be at 38 psi vac off and have a cruise AFR of 14.7. You decide you want to try to go richer and crank your fuel pressure up to 43 lbs. Guess what's going to happen... The EEC is going to shorten the injector pulse and put your AFR right back to 14.7 at cruise.

People who crank up the fuel pressure to adjust AFR do it because of one of two conditions. Not enough fuel injector to achieve commanded AFR or too large of an injector to achieve commanded AFR.

The equipment you need to digitally tune your car comes in three basic flavors:

A chip tune that is programmed on a dyno by a professional
An inexpensive system with a HUGE learning curve that you will likely not be able to learn on your own
A very expensive system that you will probably be able to learn on your own

Choose your poison. I recommend that you keep your wideband until you've learned the difference between these systems and know exactly what you need. You may discover that you will need it in order to use one of these systems.

louieb · Sep 20, 2012

there is not much info , if i lower fuel lean will result, but at 42 1/2 seems a bit rich. is there another trick or two? wider smaller spark gaps?

any other tuning tips for fuel? ty.

gearheadboy · Sep 20, 2012

You can't adjust out a 1500 ppm hydrocarbon with a plug gap or a miracle cure like letting a vacuum line off or something. Do some research on what causes the readings you have and make the corrections.

louieb · Sep 21, 2012

I know you cant dial that out, i was just pointing it out.

here are symptoms. carbon deposits, on plugs.

high hydrocarbon emissions. i had the car 6 years since new motor install. i had 2 problems from the start. only now have i followed up on it, because it drives ok a little rich. very punchy.

the good news, i fixed the problem, 1 new ignition, two new distributor, tune up. what is left?

I scanned it, and it said there was a bad ground to ecu from fuel pump.
when i find it, even though ill have to ask for help again, it should produce 25 hp or more with proper tune. it has never been tuned, let alone scanned.

scanner also produced tps senor is not calibrated right.

that means the computor is reading the fuel incorrectly. creating a rich condition.
i did do my research. that could cause more fuel to come in.

25 hp or more may pop out of this motor, after its aif flow, and fuel ratio is solved.
the reason may have to do with this bad ground.

is it on the cpu? or is it in the fuel tank?

thanks.

Noobz347 · Sep 21, 2012

louieb said:
that means the computor is reading the fuel incorrectly. creating a rich condition.
i did do my research. that could cause more fuel to come in.

This is incorrect. Fox cars come with narrow band sensors to feed the EEC. All it knows is if the sensor is off-scale high, off-scale low, or predominantly in the middle. What's more, is that the only time it makes adjustments is at idle. It will add or subtract a TOTAL of roughly 15% fuel to the entire fuel table based on whether it sees the sweet spot at idle or cruise. Those adjustments are made to the ENTIRE fuel table including the WOT and part throttle tables.

When you run larger injectors with a "tuned" (cough) meter, your injector slopes are off. What that means is that the 15% +/- fuel added to the KAM is also going to be added/subtracted to fuel tables that do not match the slope of your injectors. 24lb injectors, you can usually get away with... Once you start hitting 30 lb and higher, the differences become larger than the EEC's ability to adjust.

Consider the 02 sensors in a Fox to be two position switches... They have an off, and on, and a do nothing position. They are not capable of providing the EEC with the data necessary to make fuel efficiency adjustments. Not in the manner that you're thinking they should.

Noobz347 · Sep 21, 2012

Get the car professionally tuned... A 3 bank chip will allow you a tune for power, a tune for emissions, and a tune for economy.

Gearbanger 101 · Sep 21, 2012

Noobz347 said:
Get the car professionally tuned... A 3 bank chip will allow you a tune for power, a tune for emissions, and a tune for economy.

....but not all at the same time.

jrichker · Sep 21, 2012

What are you running that needs 30 LB injectors? Those injectors would be OK on a 351W or a 302 with pressurized induction, but too big for a normally aspirated 302.

Fuel injector sizing & injector photos

Revised 11-Dec-2011 to add larger injector sizes to injector table

Injector HP ratings: 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/ 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

louieb · Sep 21, 2012

Noobz347 said:
This is incorrect. Fox cars come with narrow band sensors to feed the EEC. All it knows is if the sensor is off-scale high, off-scale low, or predominantly in the middle. What's more, is that the only time it makes adjustments is at idle. It will add or subtract a TOTAL of roughly 15% fuel to the entire fuel table based on whether it sees the sweet spot at idle or cruise. Those adjustments are made to the ENTIRE fuel table including the WOT and part throttle tables.

When you run larger injectors with a "tuned" (cough) meter, your injector slopes are off. What that means is that the 15% +/- fuel added to the KAM is also going to be added/subtracted to fuel tables that do not match the slope of your injectors. 24lb injectors, you can usually get away with... Once you start hitting 30 lb and higher, the differences become larger than the EEC's ability to adjust.

Consider the 02 sensors in a Fox to be two position switches... They have an off, and on, and a do nothing position. They are not capable of providing the EEC with the data necessary to make fuel efficiency adjustments. Not in the manner that you're thinking they should.

thanks for the info, the rich condition may be the ground to ecu. thats what i was told. it could cause a fuel problem.

I am tasked at finding this bad ground and fixing it. thats what i hope to do. also dial in the tps.

so any info on were these ground connections are made would be helpful. thanks ..

Noobz347 · Sep 21, 2012

jrichker is right!

I was so caught up in the tuning portion that I didn't even look to see if you even NEEDED injectors that size. If you're not running boost, you need to put the 19's back in the damned thing and call it a day.

Noobz347 · Sep 21, 2012

louieb said:
thanks for the info, the rich condition may be the ground to ecu. thats what i was told. it could cause a fuel problem.

I am tasked at finding this bad ground and fixing it. thats what i hope to do. also dial in the tps.

so any info on were these ground connections are made would be helpful. thanks ..

TPS doesn't need to be 'dialed in' on a Fox. It's referenced on startup.

I think jrichker has a ton of EEC wiring diagrams at his fingertips.

Noobz347 · Sep 21, 2012

Noobz347 said:
TPS doesn't need to be 'dialed in' on a Fox. It's referenced on startup.

I think jrichker has a ton of EEC wiring diagrams at his fingertips.

Disregard... he's already provided it in his post above.

Some f the colors might be different because of the differences in years and your MAF conversion.

Gearbanger 101 · Sep 21, 2012

Noobz347 said:
jrichker is right!

I was so caught up in the tuning portion that I didn't even look to see if you even NEEDED injectors that size. If you're not running boost, you need to put the 19's back in the damned thing and call it a day.

I guess it would depend on the mass air meter he was running. If he's running one calibrated to 30lb squirters, then it should be able to fool the computer into thinking everything is hunky-dory?

louieb · Sep 21, 2012

331 10.4 compression. AFR 185 heads, comp cam 266 ex energy. accufab 90 mm race throttle body. to 75 mm. 90 mm Anderson ford power pipe, T5 world class, on top performer RPM 2 30 lb injectors 80 mm mass air. Digital A9L ignition. aluminum drive shaft third link, center force clutch. rear seat delete x-Pipe shorty heads.. 1986 GT. cheers.

Power should be identical, if not better than the test set up on the AFR dyno results small block ford..

I built my motor to be test proven already. Modled after test 4 The 331 package. see link.

http://www.airflowresearch.com/ford_dyno.php

Noobz347 · Sep 21, 2012

Gearbanger 101 said:
I guess it would depend on the mass air meter he was running. If he's running one calibrated to 30lb squirters, then it should be able to fool the computer into thinking everything is hunky-dory?

No... because the slope in the EEC is for a 19 lb injectors. A MAF can you close but it can't tell the EEC how to behave across it's entire duty cycle. So you'd be fat at some portions of the table and lean in others. The EEC doesn't know it's not trimming a 19.

30's are generally the limit without a tune. Yeah.... I've seen folks go larger and be really lucky (or least claim that they were)... I've not been that lucky. lol I've had to trim everything over a 24 on a non-Cobra EEC.

louieb said:
331 10.4 compression. AFR 185 heads, comp cam 266 ex energy. accufab 90 mm race throttle body. to 75 mm. 90 mm Anderson ford power pipe, T5 world class, on top performer RPM 2 30 lb injectors 80 mm mass air. Digital A9L ignition. aluminum drive shaft third link, center force clutch. rear seat delete x-Pipe shorty heads.. 1986 GT. cheers.

Power should be identical, if not better than the test set up on the AFR dyno results small block ford..

I built my motor to be test proven already. Modled after test 4 The 331 package. see link.

http://www.airflowresearch.com/ford_dyno.php

Hope you find your bad ground (if there is one). You need to get it tuned. You're way outside of what the factory EEC was designed to handle.

louieb · Sep 21, 2012

Noobz347 said:
Disregard... he's already provided it in his post above.

Some f the colors might be different because of the differences in years and your MAF conversion.

louieb · Sep 21, 2012

thanks for this link. i guess i need to be tracing, off the fuel pump relay.
also i would like to add, these red bosh injectors flow 30 lb at 42 1/2 lbs. the motor seems to like more fuel. it was originally set at 36 lbs from performance shop. they said thats normally what they set them at. when i changed it the motor was much better, but already i had the pip sensor in the distributor starting to fail or was not doing its job. after a year or so it finaly quit all together. (pip sensor)

I just hope i can find this bad ground wire.

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