I'm gonna have to dissagree with this one. Here's why.

The heated MAF wire losses heat by both velocity of the air and the temp(density). It could be explained like windchill. Colder temp or higher velocity will make the "feels like temp" change. A 70 deg flow of air at 10 mph will feel a lot warmer then 20 deg air at the same speed. The velocity of the air isn't any different say at 5000 RPM on or off the bottle, but the temp is a lot colder. Because the PCM tries to keep that wire at a constant temp(just like your body tries to stay at 98.6) it has to pass more current through it to keep it the same cause the "feels like" temp to the wire is lower(your body shivers and forces it's muscles to work and make heat to keep up your temp)

This only works cause it is heated, the velocity and temp...lets say "strip" the heat off it, and the PCM corrects buy givin it some more juice to keep warm. If it just read the air temp, it would be called an IAT.

 

Well said, thanks. And when the heat is stripped away the resistance changes untill warmed up again and thus a different electrical signal is sent to the computer to adjust/find proper a/f, correct?

 

Yes that is what I said earlier and I agree with BMN.

 

I am willing to put money on the fact this is wrong. A 50 dry shot doesnt put as much fuel into the motor as a 200 shot otherwise how do you figure the A/F ratio stays the same?

I will ask Ricky from NX to chime in on this one cause that just doesnt add up.

 

I work for BLAH BLAH and we built a boat for BLAH BLAH who cares? You obviously dont know what you are talking about or you would finally admit what I have been saying is correct. Chalk it up and say he you misunderstood what I was saying that way you can save face without resorting to personal attacks.

3 years of tech and 4 years of mech engineering congrats I got my mech. engineering degree in 1997 after just 4 years so you want a biscuit with that?

I never claimed I know everything in the world but I still have yet where you showed I was wrong at any point during this discussion.

Wow it must be a cool job to be building a boat for Edelbrock but what the **** does that have to do with the price of tea in China or pertain to this topic? Oh yeah nothing just another attempt to draw the attention away from the fact I proved you were wrong and misinformed over and over again.

Oh and you look pretty young to have 40+ years of drag racing. Say you started at 12 that would make you 52 you dont look that old, what story sunshine???? Oh that is probably some other useless fact to hide the notion you were made to look like a fool.

 

I wouldn't bet much money on that one.
If the nozzle is directly in front of the MAF as in Homeslice's case, even a system pilled for 50hp can max out the MAF depending on conditions. Once the signal from the MAF is maxed, it's maxed. The PCM calculates fueling for maximum load and depending on conditions, that could be all the fuel you can get.

What I think he was saying is that a small shot can max out the MAF just like a big shot can.

 

I get what he was saying maybe I am misunderstanding his thinking.

My question to that is say ok 50hp shot directly in front of the MAF sensor maxes the fueling out (As far as the MAF sensor is concerned not the injectors), ok I will buy that for now. Then what happens when you spray a 100 shot? It is already maxed out at a 50 shot so where is the PCM getting the information to add more fuel? O2 sensors? If so it is a little late by that point. If not there then where? It HAS to add more fuel or the A/F ratio will be WAY off optimal on the lean side.

You can say you tune it to just run more fuel all the time but then the car runs super rich and like a pig when you arent spraying.

 

Man so much input so much input.
I have been on the fence on this one. I personelly do not have or sale dry kits, so I do have a couple of questions, and then a couple of comments.
Question:
1. What is the maxed out point on the maf. TEMP
2. Has anybody ever monitored the voltage, or resistance on the ECM sensing wiring. Sorry if the terms are off just not as technical as I should be.
3. Who cares as long as it works. lol

Now my comments.
When you are at wide open throttle and you spray lets say 50hp worth of nitrous. The amount of outside or heated air has a greater volume then the 50hp worth of nitrous. Hence that air will absorb or dispurse the cold volume. Now you are spraying 200hp worth of nitrous. You have a larger amount of cold air then you did with 50hp. The overall effect of the incoming air is greatly changed.

If I under some of the comments about maxing out the maf,(even at a small shot) it would be correct in stating that system would run rich until the proper amount of air to match that fuel is supplied.

Again I am not dry tech but it would be safe to say that the MAF adds fuel in proporation to amount of air the engine is letting in. Cold air hot air it is still air and GM has figured away out to match that air with the proper fuel. Also once you have matched the MAF out, keep raising the nitrous pill would or should lean the over all system out. And I thought it was bad to kit the MAF with a direct beam, or plum of nitrous. Nitrous being -127 at the point of discharge. I do not think GM every planned on temps that cold, or volume of air to make it that cold. I guess that would "freeze the MAF" and max it out, possible damage the sensitive wire to.
Just my opion and my question.
All right reserved to me and these comment might not reflect anybody else opinions.
Ricky

 

That's exactly what happens. As you pill up the N2O, your AFR goes from pig-rich to maybe just very rich (closer to correct).

Once your PCM sees maximum load from the MAF the actual fueling will not increase unless you change another condition that goes into the fueling calculation like the CTS output. Homeslice does change the CTS output on his car by using the CTS tricker box when he sprays. This is how he still runs very rich when spraying a 200hp shot through a ported MAF.

 

Do some more reaseach when you make comments like this.....Your IAT table is set from the factory like that...That why that resistance works to supply the PCM with that particular temp referenced in the table to pull 4 degrees or whatever that cell is set to. What if someone who has a modified table wants to pull 4 degrees like that...It will pull whatever it is referencing on the new table that was modified.

The IAT and MAF are both used.....If you spray on the MAF alone the car wont adjust timing. If find this out when the car kept eating a plug every once in awhile from not getting the fuel it needed. I moved the nozzle back to hit the IAT sensor too and the AF dropped to a fatter condition. It doesnt just use one or the other in my findings, it uses both.

 

When you spray into a MAF it drops you into a much higher load range of your timing table, so it indeed does change your timing quite a bit.

The IAT is pretty much useless. It factors in such small changes that I just zero those tables out.

 

Now this makes more sense to what you said and I replied to earlier. Well put that time.

Mike

 

I havent changed anything in the IAT table..>At least I dont think I have..LOL

Mike

 

The only way to find out for sure is for someone to log maf flow as they are spraying, and see what the maf does. does it max out on a 50 shot? what is the a/f? Change pills, now does it max on a 100, what is the a/f?

 

I've done a lot of logging already. Like I hinted at in an earlier post, it depends on exactly where you have the N2O spraying in.
If you have a 50hp dry system going into your air-filter lid, then it will probably be nowhere near maxing your MAF.
If you have it within about 2" or so of the MAF wires and it sprays directly on them, then yes it can.

 

Mr 93ls1rx7, I am sorry you took it the wrong way, I was just clowning the both of us (granted maybe more towards you) as I seen in your profile that you are an engineer, also. I don't think either of us is the absolute no-it all, but don't tell my family. Once again, I must say I am sorry for offending you, as I was trying to disfuse our debate through one sided humor.

Now 40+ years of drag racing, you don't believe it/me?
So, here's a couple pics.

The first one shows myself in white sweat shirt cleaning up around the moon tank after fueling and please notice date on photo. It is my father's A/B fuel altered. I was born and bred into mechanics/drag racing and still go to my father for info, who is still a fine Master Mechanic in his late 70's.

The second picture is of me after winning the NHRA World Championship. This photo was taken in about 1961 when in first grade, different altered than above.


In addition, I would like to thank all the tech guys for being so cool, and also for input, so we can all enjoy our hobbie.

 

I have some experience

me as a fetus

 

Now that is funny

 

Nitrous leaves the nozzle at about -129 degrees. No amount of ambient air is sufficient to raise the average temp of the charge to a degree that the MAF is capable of discerning.

It would run very rich indeed until you supply enough oxygen (in my case via N2O by jetting up) to bring the AFRs back into your desired range. In my case it took a nozzle with no jet to deliver enough nitrous to bring my AFR's up to where I wanted them.

Does that make things a little clearer?

 

No hard feelings I couldnt tell if you were joking or just being an *** so I leaned more to the side of you being an ***!!

I am on here trying to learn more too so its all good.

And to the dude that posted the Fetus pic THAT **** IS HILARIOUS!!!!