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QWKSNKE
05-12-2005, 02:41 PM
Can I run 60's in my car with the 42# Maf and tune the curve with the tweecer or will I have to change MAF's to?

Italian LX
05-12-2005, 02:47 PM
In theory, you could do it, but only up to a certain flow-rate. You would likely end up pegging the MAF if you tried it that way. However, you can go the other way though.

Sendero
05-12-2005, 03:14 PM
Aren't there guys running 55lb injectors with Lightning MAF's? I was under the impression that the MAF curve was just a measurement of incoming "metered" air and that the injector slopes were responsible for sizing the pulsewidth.

The only reason you had a MAF "calibrated" for X size injector was due to many people not having access to tuners with the ability to change fuel parameters? That way when a Mass Air Meter was calibrated for 42lbs could be installed on a car with 24lb injectors originally. Like the C&L meters with different sized flow tubes. Its the same meter, you just change out the flow tube to trick the ECU into thinking its flowing less air so you'll get less fuel from the bigger injectors.

It makes sense, but I could be wrong...

Italian LX
05-12-2005, 03:51 PM
Like the C&L meters with different sized flow tubes. Its the same meter, you just change out the flow tube to trick the ECU into thinking its flowing less air so you'll get less fuel from the bigger injectors.
There is a difference between tricking the computer mechanically and tricking it electronically.

The reason the C&L tubes work is because the different size tube allows the MAF element to cool less at the same flow-rate and, therefore, give off a lower voltage at that same flow-rate. (Keep in mind that this only works if your computer still thinks you are running the stock injector size.)

As far as tricking the computer electronically, you would have to give it the wrong injector slopes in order to use a MAF for smaller injectors. However, this only works up to the point that the meter peggs out. You must remember that when you increase injector size, it has to be because you are increasing your airflow; if you change nothing in the MAF, then you will reach 5v very quickly.

Perfect example is my car. I am running 24# injectors. If I attempt to put my stock MAF back on, there is absolutely no amount of programming I can do to keep me from pegging 5v before it even gets anywhere near my current shift point.

Think about this and then tell me if it makes sense.

.

Wicked
05-12-2005, 04:10 PM
Factory MAFs are all open curves, meaning they output based on airflow. The injector tuning is all in the ECU programming.

Aftermarket MAF's are tuned to be setup for specific size injectors to trick the computer to believe the stock 24's(or whatever is stock in your vehicle) are still in place.

If you have a 42# calibrated MAF and go to 60# injectors you could tune it in just like every other tuner does. You are not changing your airflow so it will not be a problem for the MAF(pegging).

Its the same as a MAFExtender, multiply your hi and lo fuel slopes, and displacement by the 60/42 factor to shorten the injectors pulses.

Wicked
05-12-2005, 04:13 PM
However, this only works up to the point that the meter peggs out. .

If he's only changing injectors, not the MAF, he will not peg the MAF if it wasn't pegging before.

Italian LX
05-12-2005, 04:32 PM
If he's only changing injectors, not the MAF, he will not peg the MAF if it wasn't pegging before.
You right in that aspect, but he would be limiting any chance of using the 60# injectors to their potential. If he dicded to pulley up the blower, his injectors may be capable, but he will likely hit the max of the MAF.

Wicked
05-12-2005, 04:39 PM
You right in that aspect, but he would be limiting any chance of using the 60# injectors to their potential. If he dicded to pulley up the blower, his injectors may be capable, but he will likely hit the max of the MAF.

I totally agree.

Sendero
05-12-2005, 04:51 PM
You right in that aspect, but he would be limiting any chance of using the 60# injectors to their potential. If he dicded to pulley up the blower, his injectors may be capable, but he will likely hit the max of the MAF.


Are we talking about just changing the injector slopes and not the MAF curve itself?

QWKSNKE
05-12-2005, 04:55 PM
Any difference if I use a 55# MAF

Wicked
05-12-2005, 05:10 PM
Any difference if I use a 55# MAF

Not really, its all in the scalars.

Right Nathan, he should not mess with the MAF curve itself.

QWKSNKE
05-12-2005, 07:09 PM
Not really, its all in the scalars.

Right Nathan, he should not mess with the MAF curve itself.


Why? I have been constantly modifying the curve and it isn't dialed in yet.

Wicked
05-12-2005, 08:09 PM
Why? I have been constantly modifying the curve and it isn't dialed in yet.


You're already using the 55# MAF?

Sorry, I was wrong about the 55# maf, if you switch MAF's, you will have to use the new MAF's transform function or develop it yourself.

My comment to Nathan was in response to his question about just changing injectors.

QWKSNKE
05-12-2005, 08:23 PM
You're already using the 55# MAF?



No I am currently using a 42# MAF with 42 injectors. But with aftermarket Mafs you still have to change the MAF transfer in order for the car to be right (refer custom tunes)

Anyways, since the engine rebuild, the tune is not complete (MAF curve, IAC duty, etc.).

The reason I asked these questions is because Wall has 60# injectors and a 55# MAF that he is willing to let go. Since my duty cycle with the 42's is around 90% at WOT, I was thinking of changing over to 60's

86GT
05-13-2005, 11:35 AM
Any MAF and any injector combo can be used with a tuner. The only reason they sell matched sets is for those that do not have a tuner. The Matched sets that are above the stock vaules are fooling the EEC.

Most of the tuners will enter in the MAF curve supplied by the manufacture and then simply enter in the injector slopes. That is the theory behind it, but the fact is that every car is different and the injectors have different tollerances. This is the main reason people have problems even if they have the flow data from the manufactures.

Cold air kit, conical filters and inlet tubing size and material make up all have a toll on the flow numbers. Most of the MAF manufactures use a test bench for the calibration of a MAF meter. This procedure does not include your intake track therefore there will be some differences. Injectors spray different under different pressures and intake port size. As you can see, it not as simple as it appears, but it can be done.

With all that said the 55# MAF and 60# injectors will work, but it will take time to dial it in. If you have the flow sheet, you should be able to get close. The MAF may not help if you are not pegging the one you have. You can raise the injector size and raise the fuel pressure to lower your injector duty cycle. This will only buy you time tho. The larger injectors will lower the injector duty cycle while maintaining the current fuel pressure.

As a side note, I was told the EEC has a build in limit of 90% duty cycle on the injectors. The Tweecer log will log above 90% but the EEC will limit the injector output to 90%. If this is true then you will run lean up top. It is time to change the fuel pressure or injector size. I have not had the luxury of hitting 90%, so I can not test this.

If you try richening the upper part of the MAF while at 90% Inj. DC and the mixture does not change then it is true.

QWKSNKE
05-13-2005, 12:06 PM
my fuel press at WOT ususally hits 55 - 60 psi

Italian LX
05-13-2005, 03:16 PM
I have not had the luxury of hitting 90%, so I can not test this.
I have hit 100% before. :wave:

Wicked
05-13-2005, 06:50 PM
I'd try the 60's with the MAF you have now. The new injectors would be easier/quicker to tune in than the new MAF. Might be easier to tune if you do it in two steps.

QWKSNKE
08-04-2005, 04:13 PM
I'd try the 60's with the MAF you have now. The new injectors would be easier/quicker to tune in than the new MAF. Might be easier to tune if you do it in two steps.

Actually it would take way longer. It would be easier to tune a new MAF and injectors because you would have the flow sheet to go by and adjust.

Changing the injectors on a smaller MAF would equal a lonnnng time datalogging

Wicked
08-04-2005, 04:47 PM
Actually it would take way longer. It would be easier to tune a new MAF and injectors because you would have the flow sheet to go by and adjust.

Changing the injectors on a smaller MAF would equal a lonnnng time datalogging

Well, if you can get the flow sheet for the new MAF, why couldn't you get the flow sheet for the old one. Shouldn't you already have it since you have previous tuned the car?

That doesn't really make sense.

QWKSNKE
08-04-2005, 04:55 PM
Well, if you can get the flow sheet for the new MAF, why couldn't you get the flow sheet for the old one. Shouldn't you already have it since you have previous tuned the car?

That doesn't really make sense.

:think:

Not sure if I understand what you are saying.

The flow #'s I had were not right for my car (which is not uncommon) but it put me in the ball park to start.

If I change to 60# injectors my current MAF transfer curve is going to go out the window. It would be easier to send it back to Pro-M, calibrate it for a 60# injectors and start over rather than just throwing injectors in with the current tune. Odds are it would do like it did last time and not crank because so much fuel is getting dumped into the cylinders during startup

Wicked
08-04-2005, 05:00 PM
:think:

Not sure if I understand what you are saying.

The flow #'s I had were not right for my car (which is not uncommon) but it put me in the ball park to start.

If I change to 60# injectors my current MAF transfer curve is going to go out the window. It would be easier to send it back to Pro-M, calibrate it for a 60# injectors and start over rather than just throwing injectors in with the current tune. Odds are it would do like it did last time and not crank because so much fuel is getting dumped into the cylinders during startup

Okay, so you are saying its not right to begin with.

So if you had the original flow sheet for the MAF you have, you would be okay.

QWKSNKE
08-04-2005, 05:10 PM
Okay, so you are saying its not right to begin with.

So if you had the original flow sheet for the MAF you have, you would be okay.


maybe so. maybe not. Just depends. When you have a modified car it kinda a hit or miss thing. Most of the time it will be close

Wicked
08-04-2005, 05:14 PM
maybe so. maybe not. Just depends. When you have a modified car it kinda a hit or miss thing. Most of the time it will be close

So then it could also be hit or miss with a new MAF.

QWKSNKE
08-04-2005, 05:18 PM
So then it could also be hit or miss with a new MAF.

yep and it probably would be BUT a recal would put it closer

Italian LX
08-04-2005, 06:20 PM
I think you are both missing the key point here -- Lee is already pegging his MAF at the top of his pulls so he should get it recalibrated whether he changed injectors or not.

Remember that there are two issues here and two SEPERATE reasons he is swapping injestors AND the meter. He's calibrating the MAF due to the pegging issues and he's swapping injectors because he's hitting 97% duty cycle.

If he was only hitting around 85% duty cyle, all he would have to do it recalibrate the MAF and use the same injectors. On the other hand, if he was hitting the high duty cycle but not pegging his MAF, then he would only have to swap injectors. In the later situation, he would keep his same MAF tranfer function and just change the injector slopes to match his new units.

QWKSNKE
08-04-2005, 06:24 PM
I think you are both missing the key point here -- Lee is already pegging his MAF at the top of his pulls so he should get it recalibrated whether he changed injectors or not.

.

:doh:

I wasn't thinking about that.

Regardless though, I would recal whether I was pegging the meter out or not

Wicked
08-04-2005, 09:04 PM
I think you are both missing the key point here -- Lee is already pegging his MAF at the top of his pulls so he should get it recalibrated whether he changed injectors or not.

Remember that there are two issues here and two SEPERATE reasons he is swapping injestors AND the meter. He's calibrating the MAF due to the pegging issues and he's swapping injectors because he's hitting 97% duty cycle.

If he was only hitting around 85% duty cyle, all he would have to do it recalibrate the MAF and use the same injectors. On the other hand, if he was hitting the high duty cycle but not pegging his MAF, then he would only have to swap injectors. In the later situation, he would keep his same MAF tranfer function and just change the injector slopes to match his new units.

Okay, I guess I missed where he said he was pegging the MAF. I only saw that he was out of injector.

So if you are pegging a factory meter, that is an open curve, and cannot be pre-calibrated for a specific injector, then your only option would be a bigger/different MAF or larger injector versus being able to recal the MAF.

Italian LX
08-05-2005, 06:46 AM
Okay, I guess I missed where he said he was pegging the MAF. I only saw that he was out of injector.


http://forums.qwiksnake.com/showpost.php?p=34110&postcount=9

:D

Italian LX
08-05-2005, 06:49 AM
So if you are pegging a factory meter, that is an open curve, and cannot be pre-calibrated for a specific injector, then your only option would be a bigger/different MAF or larger injector versus being able to recal the MAF.
I can't really agree or disagree with your statement because I'm not sure if I understand what you're saying.

The easiest way to understand MAF meters is to just forget about anything that has to do with calibrating them for a certain size injector. I think when people talk about meters, they make it way more complicated than it really is. The bottom line is that a MAF measures how much air is coming into your engine. At a certain CFM, the meter will return a voltage somewhere between 0-5v and that's all. Once your motor gets to the point that it's taking in more air than the meter measures at 5 volts, that is when you begin pegging the MAF.

I hope this maybe cleared it up a bit.

:nice:

Wicked
08-06-2005, 12:43 PM
I can't really agree or disagree with your statement because I'm not sure if I understand what you're saying.

The easiest way to understand MAF meters is to just forget about anything that has to do with calibrating them for a certain size injector. I think when people talk about meters, they make it way more complicated than it really is. The bottom line is that a MAF measures how much air is coming into your engine. At a certain CFM, the meter will return a voltage somewhere between 0-5v and that's all. Once your motor gets to the point that it's taking in more air than the meter measures at 5 volts, that is when you begin pegging the MAF.

I hope this maybe cleared it up a bit.

:nice:

Nm, we're all just repeating the same shit over and over. :jester: