completely different injector question. smart people only
 

As some of you may know, I have been working on a way to eliminate the MAF from the stream of air flow. To recap I am trying to set it up so that the MAF will be controled actively by throttle posision, via cable connected to a lever, conneced to the shaft of the MAF which was connected to the flapper door.
I need to find a way to compinsate for the restriction that has now been removed from the low of air. I think the best way to do this is first with larger injectors. but I am unsure what would be the proper size.
this is what I am thinking...
(X) amount of air is being pulled into the chamber with the MAF inline. the stock injectors are set up to work perfectly with X amount. now that X has been increased since the Resistanc (R) has been removed, I need to know what the new injector size (I) is going to be.
I am not a math wiz but to give you an idea
X - R = I
I could jsut experiment, but that is an expensive proposision. if I get it wrong the first time, at the least I would have to buy a new set of injectors. at worst the lean out would cost me a new motor.
I only need to get close. If the motor will start and run, I can fine tune by readjusting the MAF inside. then even more with some sort of fuel computer.
Does anyone have any idea what size injectors I should set up to? I need it to be backed up with nubmers if possible

Your first problem will be that connecting the gas pedal directly to the MAF sensor will really screw up your engine control. The computer will think you maxed out the flow when you mash the throttle at idle. I don't think the MAF sensor ever goes full open with the normal setup (does it?), but it surely doesn't at 1000 RPM.

Get a Haltech.

-Max

Exactly. Punch the throttle at 2k rpms and your engine will probably die, from the flood of gas :D

Also you will have to hold the gas down to start the car.

just go with a MAP sensor instead!

none of that is true. I have already hooked it up and run the car with the actrive setup. I just left the old one inline, and diconnected it from the electrical connectionn and hooked up my modded one the that connection. the car does run a little better. the thing is when you smash the gas your butterflies open up imedeatly too. if you guys that have an air fuel meter inside you will notice when you smash the gas you will richen a little right?. that is because the MAF has to catch up with the air demands of the motor. this stops that. when your car needs air, it has it.
the MAF does open all the way it just takes a while to get there. that is part of the problem. the posision of the flapper is dependent on how much air the motor is useing but with a delay. there is no delay with the active system.
Everytime I try to do something and I need a little help there is always some one on the board that tellls me I can't for one reason or another. Please, stop telling me I can't and start telling me what I need to get it done. It already works. I just need one more set to get it to work perfectly

Do yourself a favor and get a Haltach, it eliminates that sensor and it will run right with more power.

you have more air and less resistance, so you say you need larger fuel injectors ?

sounds logical to me.

Hook a voltmeter up to the MAF sensor wire at the ECU in the car.
You will notice that even if you floor it, it will never open more than 10-20 percent at low RPM's. The only time it ever gets close to fully open is WOT over 5-6000 rpms.

I have been playing with my S-AFC for every waking hour the last week, and I have spent a lot of time watching the mixture and the MAF sensor position.

The car will be going crazy rich when floored at lower RPM's.... but I'm sure there's some way around that.

You shouldn't need larger injectors.

You know...
I keep staring at the subject, and I've ignored replying until now.

The SMART people would go with a Haltech instead of trying to rig and fool the stock ECU...





-Ted

No matter how much you open up the intake in that area by the AFM, there is still a bottle neck in the intake after the throttle body. Without forced induction all that work your doing to get more air in the engine and trick the ECU is futile IMO. The Haltech seems a more reasonable way even though it is expensive.

Good luck anyway. The factory injectors(460cc) are good to about 230HP. Unless you port your engine they should work just fine.

One more thing. I have sit for many hours thinking of a way to get more cool air into my racecar engine. This car has no headlights so I'm going to put the air filter where the right headlight use to be and raise the headlight cover a few inches. I'll have a tube connect it with the factory intake similiar to a riced honda intake. I'll end up wit a stand alone engine management so I will not need the AFM. This is not a streetable car.

Re: completely different injector question. smart people only
 

All you may need is a fuel pressure regulator for the additional fuel. Changing to a bigger size may be too drastic.

could you hook the afm up to the output of the air pump?? what you need is something that simulates the afm from the tps or an ecu that uses a map sensor, like an fd one

mike

Oh man.. ever see the board game "Mousetrap"??
That's what this dude's engine bay is going to look like.
It's a great concept, but just too "Rube Goldberg"ish.

Cool, since it works maybe you can tell me how the AFM is used by the ECU in the first place. See its only one input into the A/F equation. Its been speculated that its only used for low demand situations and not used when the ECU goes open loop; ie when the secondaries come online (then the ECU calc's fuel based on boost (MAP), RPM's along with the minor correction factors (battery voltage, water temp, air temp, etc.) The other inputs will be things like the TPS reading. The little bump going rich when you mash the throttle is there for a reason (its equivalent to the throttle pump on carbs and has to do with the complexities of sudden changes in the airflow speed in the throttle body IIRC) and its not because the flapper is slow (think about it, if the flapper is slow (hence reporting LESS air to the engine than actual), then you'de see a lean condition at this time). With your current setup your going to run rich at low RPMs with the pedal mashed and lean at higher RPMs and light throttle as you don't have an RPM input into your 'revised' AFM setup. I suspect your gas mileage is going to hell as well as the ECU will likey not be able to run closed loop at low throttle conditions as the A/F mixture will be too far off to correct for. The ECU will also go to a 'default' value for the AFM if its thinks its failed, you may be running off this - seeing any codes?

You don't need larger injectors to compensate if the above is correct. You do need an RPM correction into your setup if you really want to run this way.

Now for the intelligent answer: take Ted's advice.

Henrik
87TII

Hey tweekek. I thought of something...Not to lose focus on your question but what if bambam or someone got the percentage of the increase of the flapper door, he says 10-20 percent at under 3k rpm or something.. All we have to do is figure out the rest for all the RPMS so we can electronically open the maff by a motor that senses the input from the ECU and will push the maf to the position it needs to be... . or not?????? But anyways u have a good idea as long as this isnt your daily driver it should be a fun project.

Soul assasin. Can u convert to a map without a stand alone???

Anyone smart want to tell us why this will not work instead of telling us to get a stand alone.???????
That would be much more apreciated. If u dont have anything smart to say then just dont post your opinion. We all now that it would be easier and safer to get a stand alone but were obviously arnt right.... So why bother.

One thing I have learned by playing with the AFC is the drivability is affected GREATLY by just s tiny bit of fuel difference. 2-3% can make a car run like crap. Light throttle can be rough, it can stutter, jerk on-off throttle, whatever. It's really suprising how much of a idfference a little bit makes. Now- If you want I'll check to see where the AFM is at WOT though the RPM range, but it will ONLY be good at WOT, and I'm sure my car isn't identical to yours. I just don't think the results will be good enough to persue- honestly. You may be able to rig it for full throttle compensation, but the car would be baerely drivable- ESPECIALLY when it's cold. It'll be about as streetable as a 300 hp bridgeport- Doesn't seem like a worthwhile sacrifice for 5 HP.

Bambam.. Nevermind but thnx.. I dont want u to go through the hassle because it was just a suggestion and wont be doing it...I will start looking into electric motors and stuff... Just to see if thiers any possibilities. Your right about your car. Its different and will mess up someone elses car most likely.

"smart people only"

:crackup:

you should have put "poor smart people" since most smart people would just go haltech...

Look. I am sick of the people that say this can't be done or that a halteck is the answer. in some classes of racing you can't use aftermarket fuel managment. other people could do this to get more power that can't afford $3000 for the new computer and somebody to tune it right.. there is no mouse trap syndrome under my hood. the MAF is a self contained box with a throttle cable comming out of it. If you arn't going to help me then shut the hell up!. I don't want to be rude but this sux ass. everytime someone wants to try something new, a few people attack them for thinking out side the box. If I could get this to work I am sure there are several people that would want the how to.
The MAF is another Mazda mistake. it robs power plane and simple.
I have taken care of the intake I just put on my ported manifold. now the bottle neck is the throttle body. my intake out flows it.
the computer only goes into open loop at very high engine operation. it can't prossess fast enough to keep up with the changes that happen above some where around 5500 RPM
There are some very minor drivabliity issues which I am working out. it just needs fine tuning.


The Adjustable fuel regulator is a good idea. thanks


the ECU uses the MAF to sense how much air the motor is using at a given moment. this is how it works, the motor has an amount of air that it needs which changes with rpm. (all other things being equal). the MAF is passive, it has a door that is in the way of the air. as more air passes though the opening being blocked by that door, the door is forced open. the door is attached to a shaft that is spring loaded to close as air demand falls. at the other end of this shaft, in side a sealed box, is a variable resistor. this resistor slides in a circular motion as the door is opened farther. as the electrical resistance changes the computer makes minor adjustments to compensate for timing and fuel.

One mre thing if you guys are sooo worried about me running rich at WOT. I could set up a small.... kind of shock absorber to slow the "opening of the door" but as of yet I have noticed no ill affect on mixture

You might look into the flapper to hotwire conversion kits they have for the Mr2 Toyota crowd. Hot wire sensors don't restrict flow much, like the flappers do, and they don't have any moving parts.

Or maybe you can pump freon from the AC into the intake to make the mixture a bit denser, and maybe it will help the Octane, who knows for sure ?

What do you think, Max ?



-Les

I really, really, really like the FREON idea. That took some thought to come up with that.

Trying to use the stock ECM programming is the tough part. And the stock injectors will be big enough if the ECM is programmed properly. An adjustable fuel pressure regulator will help for WOT open loop conditions.

I would suggest figuring out how to reprogram the stock ECM. Try this link maybe it will help get you started: www.diy-efi.org. It is more for the GM guys but has a lot of great information. If aftermarket companies can re burn them there is no reason you can't.

I also agree with lesd. Converting it to a hot wire setup would be best, if you get a large enough one you will have no bottle neck at the AFM anymore. These type of MAF (AFM) are great, they are very accurate at giving the ECM the amount of airflow. A stock GM LT1MAF flows 887 CFM with the trash screen removed. Your motor will never out flow it. And you can get used ones on Ebay for arounf $50.

Maybe you should log all your time on this. If time is money the Haltech will save you a ton. But if you have more time than money, than I suggest burning your own PROM, and making a wide band A/F ratio meter.

Good Luck

Is your engine a 6 port? If so.. just pull the 6th port studs out of the housings, elliminate the vaccum activators in the intake manifold and install bigger secondary injectors (84-85 gsl-se).

I believe that the "poor smart people" comment is not a positive one. So please don't say such things there are RX-7's running the 7 seconds with turbo/webber I say that is just plain smart, it is not about who got more money it is about who knows what to buy without being misled by the corporate racing Bullshit hype!!!!!

Hey Tweeked. Im sure an electrical engineer can ansewer your question. THiers got to be able to find a car engineer from mazda who desinged the thing who can tell u.

Where can anyone find the hotwire conversion.

If you can't afford to pay, you can't afford to play...

Alright, after this reply, you won't get another peep from me...

Sure, and you end up being an engineering anomoly with your 15 minutes of fame on the Internet...

Boy, I don't see your engineering credentials posted.&nbsp You've just blasted a few millions dollars of R&D by Bosch (foremost) and Mazda.&nbsp I'd tend to rely on engineers from Bosch and Mazda anyday over your claims at this point.

Wrong.&nbsp It runs an open loop idle.&nbsp it also runs open-loop anytime over 4kRPM or when the secondary fuel injectors kick in.

Wrong again.&nbsp The 1986-1988 Zenki FC's run a logrithmic resistance signal that fluctuates several times from 0 to 5k-ohms(?); this is not a simple potentiometer.&nbsp Also, the AFM input is strictly for fuel; it has nothing to do with timing.&nbsp Timing is controlled by boost/pressure sensor and RPM, primarily.

By the time you get everything "tuned" adequately, I could've worked and made enough money to have bought and install the Haltech...

Hell, you want cheap, go with and SDS or any of the "cheaper" stand-alone system available for under $1,000...

I'd recommend you do your homework before making wrongful assumptions at pointed out above.&nbsp You're trying to tinker with something you don't have the proper knowledge of?&nbsp That always leads to no where...



-Ted

Mazdaspeed7 is working on one, but I beleive has hit a wall with the power supply... I am not sure though.

OK, I just don't know if this MAF conversion is possible without some real professional development.
Have you ever watched the AFM sensor when you touch the throttle off idle? It jumps in very far for a second when you first touch the throttle, then returns, even thugh you still have the throttle open. This is due the engine vacuum being initially depleted when the butterflies open , then resuming to normal engine intake. The ECU takes advantage of this natural process to use it as the "accelerator pump" that carbs have. The engine needs that little enrichening jump. The computer is programmed like that. I am not sure if the hot-wire sensor can react quickly enough to accomodate that- and if it can't then a computer in-line with the AFM signal needs to be built to simulate it.

Most EFI's use the TPS to sense the need for extra fuel when you stomp the gas. Hot wire reacts pretty fast, but the issue I have is how linear the signal is vs. flow rate. I am considering one for a turbo VW aircooled bug at the moment. I hate carbs, and I hate flappers too. If the MAF was linear, I'd use that vs speed density. It just seems more correct to me.

-Les

I think the best solution would be a software one- like the signal interpreter software on the board of a wideband o2 sensor display.
If someone could make a board that would simply convert the hot wire signal, to the proper cooresponding MAF output voltage to the ECU. Just install the hot-wire, the converter, and go.
Enough with linkages, and crap- all these baind-aid solutions. But like I said, that needs more or less profesional development. Cause I don't know how!!

This just strikes me as a lot of hard work for very little gain. I applaud you for thinking laterally to get around a problem but I don't think you've got enough of a grasp on how EFI works to overcome the many problems this conversion would cause. The power gained by removing the restriction caused by the AFM would be lost because of the screwed up fuelling. The obvious downfall of your design is that airflow into the engine is not linearly related to throttle position. That's it. Some systems can run off throttle position and RPM only but that's only on racecars that run mainly WOT, and would be totally unsuitable for a road car.
If you're dead set on eleminating the AFM but not the stock ECU, consider the HKS VPC, but in terms of $/hp an aftermarket ECU is still better.
BTW, for every one knocking air flow meters, remember the ECU needs to know how much air is going into the engine, and the only way to do this is with an AFM. You can only estimate air flow from manifold pressure or throttle position, which is why most cars have use an AFM. A manufacturer has to worry about economy and emissions, not just peak power, so an accurate measure of air flow is required. The ideal setup would be a hot wire type AFM capable of flowing large amounts of air without causing a restiction.

yes I do understand how efi works. I was over simplifying for the sake of the forum.
I may have been a little off on how this particular EFI system works, but this IS how most work. there may be slight differences, but the things work about the same. when open loop happens is nearly irrelivant, not completly, but nearly.
the MAF is used for tuning and fuel you were right just not completly. so was I. it adjusts how much fuel based on how much air. this is basic tuning.

A big thanks to every one that has offered advice.
I did consider the wok involved befor hand. to date I have spen about 30 minutes procurring a used MAF, another cutting ut up to eliminate the flapper and still have the shaft. 15 minutes fitting it to a "kit box" from radio shack. and about an hour figuring out where the cable an lever need to be on the shaft so that is opens in parallel with the unit that is still stock. this will be greatly reduced since now I know and all I have to do is measure and write it down. ( i need to remember to measure)
Any way I am going to order a variable fuel reg. next week. I will do som research to find one that I like. at an affordible price of course.