Mazda2ndgen

Ok, for those of you who have not been following the "pics of my car and intake" thread, I have a motor that had lost compression for some reason, it had 75psi on all three rotor faces on the front rotor, and 65on all the faces on the rear. anway, hwere i live the local dragstrip has once a month an open running for poeple who want to race. its bascily set up for streetracers. No water box, no dragsters, balah, blah, balh. the line runs real quick and you get to get a lot of runs in. all they do is show your time if you want for it to be shown, no time slips. so anyway, I went down there on friday night.

the best i ran was a 15.0 with low compression! hahaha, that was really cool. I dont know what the trap speed was.

well, for quite some time i ahve been kicking around a new intake idea. basicly, I decided that the best AFM to have is no afm. and, what you do is, get a s-afc, a a/f gague, and then you remove the afm from the intake, but leave it pluged in, and hold the flapper door opne somehow. with the flapper door opne you will be running full rich the whole time, so you will need to use the afc to detune all the fuel out of the low rpm (beolow about 5k), then add fuel if necisary in the upper rpm. BUt i have not had the money to buy a s-afc or a/f gague as of yet so i havent been able to try out my idea.

well, while whre at the track my friend says that we sould try the no afm mod and see if hte car will run. I knew deep down inside that i would runlean if it even ran at all, but me being stupid and half curious i deciede to try it.

with my intake setup it is really easy to do theis. see the thread and picutes to findy out why. anyway, what i did was, left the afm hooked on the intake, then started the car, then removed the afm, reved up the eninge, and held the flapper door wide open. the car below about 5k runs EXTEMELY rich and barley runs, but as soon as you get to 5krpm the engine just revs like never before!! wow!!!! well, we tested it a few times, and then decied to make a run. We started it up, and then zip tied the flapper door open. I staged (etremly had to do at 5000rpm) then went!! holy crap 1st gear was sooo freakin fast!! wow!!! BUT, then i shifted to 2nd. doh. it had hardly anypower, and the car just stuumbled, and hesitaked and just felt like crap. but i stayed on it, ran through 2nd went inot 3rd and finished the 1/4. i ran a 15.2!!!! agian, i dont know what the trap speed was. I pulled over, put the afm back on, and the car barley ran and felt aweful. I went home (about 5min from the trac) and did a compression check. 1st rotor, 85-85-85. haha, i somehow gained compression back on the front rotor, but the spark plugs were white. not tan, but white!! then i checked the rear rotor and it was 0-0-0. i put my hand infront of the spark plug holes, an no air was coimng out... on saturday, i used a mirror to look into the eingein throughtt the sparkplug holes, i could see the groves where two of the apex seals were supposed to be, but they wernt there. but ther was one apex seal left... i gues i am lucky that i didnt blow up the front rotor too.

at any rate. the point is, you CAN run without an AFM. and the fact taht i ran a 15.2 only running on one rotor after 1st gear shows that there are huge gains to be made running iwth out an afm. but, thats if you ahve enogh fuel.

what you have to do, is have an a/f gauge so that you know if you are running lean or not. and an afc to add fuel up top, and to take away fuel in the lower rpm. all you have to do is leave the afm pluged in, but keep the door all the way open so that it will be running full rich so that you will get enough feul. this is better tahn any mustang afm. Now i dotn reccommed yuou do this unles you ahve a a/f guage and an afc or you will blow your motor like i did. but htis will work.

mazdaspeed7- y ou might want to try this. your car will run without the afm, it just will run real lean up top, and real rich down low. thats why you need the afc to tune that.

but the ony thing is, i dont know if the afc will have enough adjustmen to compinsate for all the extra fuel that you get at low rpm, b/c the engine thinks you need all the fuel b/c the flapper door is all the way open, but you are actuly at a low rpm. its just somghitn that i will have to test. if anyone does this please post and let me know if it works or not b/y i am curious!

and btw, before anyone says it, i know that iam a freakin idiot for doing what i did. but oh well, what happend, happend, and i'm just going to have to get a new motor now. oh well. but, at least i did prove that it will work to run without an afm, you just need more fuel up top, and less in the afm. and i proved that there are huge hp gains b/c i ran a 15.2 only on the front rotor after 1st gear

natedogg

I can't believe you actually had the patience to type all of that!!

You're.... amazing dude.

VtekEater

Hey man thats pretty bad ***
Sucks what happened to your motor though
Hey I'll try this on my friends car since I gave him my SAFC and see if it will work, hehehe he will be my guinee pig
I'll post tomorrow and tell you guys if it worked
See ya

Mazda2ndgen

Awesome!! I am really curious if it will work with a afc or not. Just leave the afm attached to the car, then start it, rev it up a little, then remove the afm, and open the door, and give it a lot of gas, and it wiill run. personaly, i would add more fuel up top on the afc before doing it, so that you run lean at all, b/c you will. then even when you are 1st testing it you wont fun to lean. then after you get the top end happy where it isnt running lean, tehn try to get rid of all the fuel in lower rpm. thats where i am concerned. I just dontknow if the afc will be able to make it so that it wont run soooo rich in lower rpm. i had messed around with it beofre, and if you just pushed the flapper door in slighly wtih the car running at at idle, it would die. so i just dont know if it will be alble to run at low rpm with out running so rich that it stalls. i guess youll just have to find out!

hopefully a new motor will come soon.

Mazda2ndgen

oh,and heck ya taht took a long to time to type!! but this is a potential HUGE mod if it works with an afc for the 2ndgen crowd! and it should work on t2s ithink. I dont see why tnot. i think how much fuel the computer puts into the eninge is based upon the tps and the afm on the na's, and the tps, afm, and boost on t2s. but the boost senosr doesnt connect wtih the afm in anyway, itdont think it doesn anyway. so it should in theory work on t2s too!?!?

Keith

I am going to throw out some observations here to think about. When the model T Ford came out, the "carburetor" on it was a venturi, a pipe with a hole in the side. The engine ran at a constant rpm, had no throttle, so this worked really well. As engines evolved, they had to run at variable rpm's, so in addition to the venturi, idle jets, intermediate jets (for partial throttle openings) were added to the venturi. For passing power, a power valve was added (actuated when there was no manifold vacuum). Here, we had a step device, consisting of idle, intermediate, main, and power. When the emissions stuff hit, a carburetor was just too inaccurate to cope, so a throttle body system was developed. A computer would sample rpm, throttle position, manifold vacuum, and engine temperature, and would then compute how much air was being drawn into the engine and inject the correct fuel for it. This was a pretty good educated guess, and with an oxygen sensor for correction, it worked pretty good. Well, for performance, this still wasn't good enough. So, the system evolved in a very logical direction: Don't guess at the air being drawn into the engine, measure it! It's much simpler and much more precise. There are 2 types, volume and Mass AFM's (Mass is the most precise, our cars use a volume type, Mustangs use a Mass type). Yeah, corrections are generated by throttle position (on our cars, that input is only for the first 1/3 of throttle opening), air and water temperature, and manifold vacuum/pressure.

Then along came Mazda2ndgen and turned his intake system back into a model T!!!! The purpose of an AFC is to fine tune Air/fuel mixture by making slight corrections to the AFM signal at 500 rpm increments. Your AFM is sending a signal saying the engine is drawing the most air it can possibly draw at all rpms! Even with the max 50% correction, your signal will still be 50% of the maximum the AFM can sense! Since at idle the flap is barely open, you can never hope to even come close! Hey, if you want a car that you tow to the drag strip, you're fine. If you try and drive it on the street (assuming you can even keep the engine running), you are going to carbon your engine to death in a matter of weeks! Hey, I'll even help you out, so you don't need the AFM at all. Just jumper pins B and D (+5v to voltage sense). You will also need to jumper the fuel pump test connector or pins G and H on the AFM connector to keep the fuel pump going. Sure, it ran better, all AFM's are restrictive!

I'm not trying to Flame anyone here, all this is IMHO. Also my $.02 worth.

Irv, Keith's dad

kliftin

Alright. Makes sense. I have the afc. Keith is saying that the AFC gets the airflow signal coming out of the AFM and converts that to A higher Value and shows it to the ecu thus +-50 percent of more fuel ACCORDING TO THAT NEW VALUE. So if that value from the AFM Is at 0(zero) airflow. 50 percent increase of ZERO is uuuuuu ZERRRRROOOO.

So we found a little hickup keith. Dosent mean we should all give up. Mazda2ndgen was on to something. I have a little idea. please coment on it.

Take off the AFM like m2g said but we would now have to figure out how to get some air threw to make the 50 percent adjustment closer to what the car would need to be at. I hope your following me. Like I said 0 flow plus 50 percent adjustments is zero. But get some air threw the AFM plus 50 is SOMETHIN.
Solution-To cure this all you have to do is instead of cracking the flap open at 100 percent, crack it open only part way so the afm senses some flow. Low enoughf to make your adjustments up to - 50 percent now compensating for the overly rich mix. Now as for the top end leaning out because of monster airflow and not enough air going through the AFM, I have a possible solution. I think.

One is finding out some way to open the afm all the way pluss tunning on the afc. (we still dont know it the afm at part open with afc +50 isnt enoughf so assuming it isnt.) Get the air pump and stick it in the afm but cover the back side and pinch a hole in it. I think this would create a vacume with the air pumping through it. I dont know. At high rpms that thing puts out a lot of air wich is were we need it to open at... My second solution is simpler mabey. Get T11 injectors and a T11 fuel pump like I have. Have not installed yet though. Someone might read this and think what an idiot. But im only 20 and like to think so no flamin...

kliftin

Alright. The airpump wont work because It would send the computer crazy with the sudden jump in gas. And you wouldnt know when it would open so you would have to check it out on the af gauge. I just ansewered my question.... but I think getting t11 injectors and pump would be better. I would try it but have to re ingeneer my injectors first. Bad surging prob when cold only. Anyone now whats up.

Mazda2ndgen

actualy, no i didnt turn my car into a model t.

anyway. what you said is exatcly what i said in my post, i was concerened that the afc would not have enough adjustment to make up for the engine running so rich in lower rpm. but, the solutuion to that would be only open the door half way, then with the 50% you could take away all the extra fuel in the low rpm, and then again, with the 50% you could add all the fuel back to the top end. then that way it would be just like having hte afm, but without it being attached. b/c if hte door is opne half way, and you adjust the signal 50% in each direction it would be just like haviing hte full range of hte flapper door. now, this would result in a lean condiditon in the upper rpm, which was demonstarted by my motor. the soltuion to that would be t2 injectors in the secondariys. this idea will work, all it will take is a little time and tuning. i'll let everyone know how it goes whenever i get the money to do it. im gonna be pulling my motor this weekend to rebuild it, so the afc shoudl come soon after i get the motor back in

kliftin

Solution-To cure this all you have to do is instead of cracking the flap open at 100 percent, crack it open only part way so the afm senses some flow. Low enoughf to make your adjustments up to - 50 percent now compensating for the overly rich mix. Now as for the top end leaning out because of monster airflow and not enough air going through the AFM, I have a possible solution. I think.

supergoat

where can I buy an s-afc. I'm not gonna try this, I just want one.

Keith

Ok, I'm gonna try this one more time, simply because I am a glutton for punishment. More likely I'm an idiot, pick which one that applies. Let's say you get the car to idle. You have a fixed AFM signal here, corrected by the SAFC. You now floor it. Since the AFM signal didn't change (it would change drastically if the AFM was still installed), for the next 500 rpm at least, you would have an engine sucking air like crazy but only enough fuel for idle. WAY lean, wouldn't you say? Well, you could correct that by tuning the SAFC, you say? Sure, but if you got the mix correct for WOT, it wouldn't idle (WAY too rich!). Another example: you just finished your 1/4 mile. You leave the car in gear, and let go of the gas pedal. Normally, the AFM would show a huge reduction in air intake. It's fixed, remember? So, you now have enough fuel being injected for 7000 rpm WOT, but the throttle plates are closed! If, by some miracle the engine didn't stall, I bet there would be so much black smoke pouring out of the exhaust that the people in the stands would have to wear gas masks! Not to mention new plugs needed for every run!

All I'm trying to point out here is that the AFM serves a very important purpose here - it is the main input for the ECU in deciding how much fuel the engine needs.

If you want to eliminate the AFM, I would suggest modifying an aftermarket Throttle Body system, which would then take the place of the AFM function. Also, as noted in my earlier post, you really don't need the AFM anymore just to provide a fixed input, just use a 5 Kohm variable resistor across D and ground, with the wiper attached to B (on the AFM plug). This gives you infinite and stable adjustment of the simulated AFM signal.

Anyway, I'm done. You guys are on your own. Have fun!

Irv, Keith's dad

tweaked

iTrader: (4)

Here is what I have been working on. In fact I wa working on it just a few minutes ago but got cold and had to com inside.
First a little intro to the thought.
The AFM is a mecanical to electrical device right? It has a flapper door that is connected to a shaft that rotates an electrical contact. In short is it a variable resistor. This then sends the info to the computer for adjustments, right?
This is the thought. Take apart a SPARE afm. so that all you have is the shaft where the door was and the electronics housing. everyone following?
Connect to the shaft a lever of some sort.
to this lever you connect it to linkage you have made comming off of the throttle body butterfly shaft. I am trying to use the left over "hole" from where the cruse control cable would be.
You set up this linkage so that it turns the shaft on the MAF to mimic how it would work if the MAF were actually seeing air. following??
Two reasons I am using a spare MAF instead of being brave. One I drive this car every day. two, I can watch the stock MAF to get an idea what t he modded MAF should do.
This has not been a presing mod for me yet. I am close. What I would like is to be able to make it from parts you can get a just about any hardware store insead of making it from scratch. If anyone wants to try to get this done before me go ahead just share your info with me to make it easier.

I think you will still need an aftermarket puter to fine tune. but the benifits would be fantastic.

Doesn't that sound like a better plan than too rich and too lean? or new motor?

kliftin

Hears a little help. Put a voltage meter on the AFM and the other AFM to compare that way.

rx7_turbo2

I know Irv didnt want to flame but I will. This has to be one of the most retarted things I have ever heard. If you don't want to use the flapper door AFM then do it right and purchase a hotwire kit, there are a couple available for the 2nd gen, or better yet go with a stand alone ecu that runs on fuel maps, yes it will cost more money but at least it will be done right instead of some 2 bit hack job. I have a S-AFC and can tell you there is not a chance in hell I would give this a try, better 1/4 mile times and horsepower can be found else where.

tweaked

iTrader: (4)

nobody liked my idea?
I thought it was geinus.

kliftin

1/4 mile times can be found elswere. Where else. Not when your n/a is maxed out already. Nobody wants to spend 1400 for a haltec or apexi then another 600 for the proper tuning and more for dyno. I cant even find a place closer than frickin la who will even touch my car. I think 2 grand can buy me another car. Thats why I think this mod is more important to some people. Nowone said you had to try it.j

Do you have the site or place where I can get the hot wire. And will it still allow me to use my afc.?

kliftin

Procedure for the afc trick.
Heres what should be done. Someone lean out the afc at idl and read the a/f gauge. Lean it out just before it dies. Then have someone push in the AFM slightly until the a/f gauge reads normal again. Then lean out the afc the rest of the way and push the afm in again to reach the right mixture. Wants its right then Thats where the afm should be set at. This is better than just guessing by crackin the door open not noing were its optimal position is. Or am I missing somethin here.

Mazda2ndgen

ahh ok, i see your point about leaving it in gear... i hadnt thought of that. but, maybe its not a problem. the fuel curve is based upon the votage from the afm and the tps right? well, what would the computer do if its getting a signal from the afm saying it needs a lot of fuel, but a singal from the tps saying the car is at idle? that would be the situation if you let off the gas completly at 7000rpm and left the car in gear. seriously, do you know what the compter would do in that situation? b/c if it went by the tps signal i think it would be ok, but if it went by the afm siganl that would creat the problems that you mentioned.

thanks for you help and not realy flaming. I think this mod can work with a little work, but im not srue about teh streetability part yet.

and i was already thining about the varibale resittor, mabye an rpm acitvated one?

and about it not being worth it.... when you have an na, if you have to come up with new stuff. you can do a filter and exhaust and still frekin run 15s. you have to be a little gutsy and try new things...

Mazda2ndgen

hmmm, i realy like that idea. then we wouldnt hve to screw with the resistor or anything, plus the car would then not have the 500rpm gap that keith had mention the car would have. hmm, i think we can pull tihs off. also, then taht way, we wouldnt hvae to worry about the problem with leaving it in gear either. all we would have to do is use teh afc to add fuel in the upper rpm.
hmmm, your pretty smart

kliftin

Mazda2ndgen. UUUUh I dont know what the whold 500 thing is and where can we get a rpm variable resistor. One more q. What does the comp see when the afm hotwire is on? does it just take inputs from teh tps after that. If so PROBLEM SOLVED. right

defylogik

doesnt someone somewhere make a program you can run off a laptop that would piggyback off the stock computer and eliminate the afm? i mean other than a haltec... something u could plug into a serial port or what not.

my friend has a laptop in his talon tsi that logs all the data from the car and he can make adjustments in addition to his afc-r..

scott

tweaked

iTrader: (4)

I would like to know why no one is considering my idea. It sounds perfect to me. The computer thinks the car is still using the AFM. the modded AFM is still sending info to the puter. The major advantage to this is that the AFM is then proactive instead of reactive. What I mean by that is:
When you smash the gas the motor has to "catch up" to your input by then sucking in more air. there is a delay between the time you smash the petal and the AFM is fully open. Infact the AFM will not fully open until higher RPMs are reached. with the AFM connected directly to the throttle cable there is no delay. instantly the puter adds the extra fuel. the butterflies open imediatly to let in the extra fuel so there will be less delay for the motor to get the extra air and fuel it needs.
Further more if it is done correctly, you will not need the added electronics. you will only have to do the standard AFM mod to make the mixture richer, when compared to the mixture ration prior to this setup.

I am trying to use a bicycle brake cable to opperate the AFM. the part I am having troble with is the exact length of the lever connected to the shaft of the AFM. If it is too long the AFM "opens" to fast, too short and the AFM "opens" too slow. this will cause a rich and lean mixture respectively at throttle positions other than idle and WOT.

supergoat

Tweaked, I think it has potential. I'd like to see it when it's done.

Ryde _Or_Die

Ok, my question is why do you have to worry what the AFM does at all? I mean the S-AFC overrides the ECU to give more/less fuel at certain times. Is there a reason the flap has to wired open then? Or why you would need the AFM at all? I could see that you would need it or you might get some codes on the ECU but not sure what it would really do.