Why upgrade the maf?

[Drift]

I've done a search and tried to narrow it down, but still to many posts w/ maf in it? Why does the maf need to be upgraded? I know something about the voltage being limited or something of the like, but I don't understand why. The same amount of air is getting pulled the the maf whether you have the stock 155HP or push like 250HP w/ extra goodies, so what is actually limiting the maf? Main reason I'm asking is because I know of the tried and true methods from reading members posts of JWT, SAFC's, etc. I got a short answer from someone once before but didn't really answer my question as to why you could not just run 370cc injectors, and to compensate for the addl fuel by just bumping the base pressure down w/ the likes of a Nismo FPR. And begi now makes a unit which does can adjust the base pressure and can add boost dependent pressure as well. http://www.bellengineering.net....html Now I could see how the stock timing map could factor in a problem, but I just don't see why it couldn't be compensated for, for reasonably much less then what you'd pay for the other FMU options. So two questions here, the MAF question, and the FMU question. TIA

[Nathan]

What is actually limiting the MAF is the electronics inside it, it physically maxes out at a set voltage (5 v) and once its flowing enough air to require that 5 volts to keep the wire at the set temperature, then any air above that point is then un-metered. A different MAF, such as a Z32 maf has different electronics etc. and wont reach that 5v maximum until a much higher amount of air is passing through it. To understand this, you have to know how a hotwire maf works. A hotwire maf has a well...hot wire, as air passes over this hot wire it cools it, the maf detects this and increases the voltage flowing through the wire to maintain its temperature. By doing this, the maf can tell the ecu the exact quantity of air entering the intake tract

[andrave]

to simply lower base pressure would assume that the pressure would raise from that base pressue on the same linear scale as it would from the stock fuel pressure. It also assumes that the 370 injectors would perform on the same linear scale as a 270s. Which they don't.

[CarloSR]

MAF not reading = LEAN = Kabbboooommm !!

Carlos.

[j-z]

youre wrong about the same amount of air getting pulled in whether you have 150 hp or 300 hp. its not the same. if it was then you wouldnt need to get a different maf from a car that flows more air. and your whole fuel setup is just whack. go one way or the other.

[Drift]

youre wrong about the same amount of air getting pulled in whether you have 150 hp or 300 hp. its not the same. if it was then you wouldnt need to get a different maf from a car that flows more air. and your whole fuel setup is just whack. go one way or the other.

I wasn't going one way or the other, I was just trying to get some informed opinions. Its a learning process.

Quote »to simply lower base pressure would assume that the pressure would raise from that base pressue on the same linear scale as it would from the stock fuel pressure. It also assumes that the 370 injectors would perform on the same linear scale as a 270s. Which they don't. [/quote]

Don't hacked maf's basically use the same timing map? I mean the only thing that's changing between the two is the fuel pressure, no? So wouldn't it be the same as a hacked maf setup except w/ altering airflow signal, its altering fuel pressure? With the stock ecu on hacked maf, isn't the pressure still going to increase linearly on the 370's as it would the 270's just more fuel getting dumped?. The only difference this time around w/ the fuel flow which has been bumped down to compensate for the larger injectors? I'm sure I'm horribly off, I just don't see why this wouldn't work. Probably because its too easy.

[huguetpj]

I'm sure I'm horribly off, I just don't see why this wouldn't work. Probably because its too easy.

In essence yes, it's the same as having a hacked MAF... well kinda. The hacked MAF regulates injector duty cycle by measuring less air. Lowering the fuel pressure makes less fuel enter the combustion chamber. The problem with lowering fuel pressure is the possibility of a crappy idle and it could even affect fuel atomization (tr?) because of the lower pressures at the injectors.

[j-z]

hacked maf doesnt change fuel pressure. all it is is a trick being pulled to where you can run larger injectors on a totally stock ecu.

[andrave]

I think he is saying that what a hacked maf does to air, lowering the fuel pressure SHOULD do to fuel. One of the problems is that the ecu gives fuel based on air, not air based on fuel...I dunnoits confusing to thinka bout.

[Drift]

hacked maf doesnt change fuel pressure. all it is is a trick being pulled to where you can run larger injectors on a totally stock ecu.

I was actually responding to andrave's post about the whole linearity thing. I didn't know if fuel pressure was changed NA or not. So if the fuel pressure is not changed the only thing the that is changing is the duty cycle. Which if I'm correct changes according to RPM, MAF readings, load, etc. For the same conditions then on 270cc vs 370cc, the ecu will not know anything is different and will keep the duty cycle the same for all 270cc conditions. The only problem then should be first then is how low does the fuel pressure actually have to go in order to not be too rich. If the whole linearity thing holds up (which I'm sure it doesn't) from base fuel pressure of 45 PSI, you would need to drop that down by about 27% (27% increase of injector) which is 12.15 PSI dropping the base down to around 33 PSI. Is that really that much lower? I know atomization probably needs a certain amount of PSI, but 33 doesn't seem too low, and what is the stock fuel pressure on an SR 20 anyways? A 12:1 FMU would increase pressure that much for one pound of boost ... I don't know, it still just seems to me like it can be done if a hacked maf will work. Maybe I'll try to pioneer the "hacked fuel pressure regulator".

[andrave]

its called an adjustable fuel pressure regulator. A look through ebay, nopi, or the summit catalog suggest that you are not the pioneer.

[Drift]

its called an adjustable fuel pressure regulator. A look through ebay, nopi, or the summit catalog suggest that you are not the pioneer.

Dude I know. I alluded to one in my first post with a link. I meant it pertaining to the subject at hand. Geez, didn't know peeps were so literal.

[andrave]

its alright I just had a bad day at work, came home alone, then my fiancee and I had a row.and then I read your post.sorry.

[Jookmasta]

sorry for bringin back a week or two old post but this caught my eye and the topic happens to land on this question i have. so if im gonna be running 370cc injectors with an safc to compensate; i will also have a nismo fpr; will i also need to upgrade the MAF? i only want to run b/w 250 and 300whp. help help HELP!!!!!

[C-Kwik]

I'm not sure of the limitations of the S13 MAF. The S14 MAF is 260 WHP according to JWT. It's possible the S13 MAF may be lower. With something like a SAFC or E-Manage, I would look into upgrading the MAF even at 7 psi+ on an S14. Perhaps lower on an S13 if the MAF limit is lower. Since both the E-Manage and AFC see only a max of 5 volts from the MAF and then alter the signal to a lower voltage to compensate for larger injectors, the MAF actually maxes out sooner. In fact at 6.5 psi, my MAF is maxing out at some 5000 RPM, hitting 5 volts. The ECU then only sees about 4.5 volts max and can never see higher without some tuning. But tuning once the MAF hits 5 volts will be inaccurate. My injectors do not go over about 80% duty cycle. I also believe the MAF actually goes a little over 5 volts since the S14 MAF should not be maxing out until about 10-11 psi.

[Drift]

C-Kwik - I read some of your other posts and was kinda hoping you'd respond to my fuel pressure question. What's your take on the whole thing?

[C-Kwik]

Personally, I'd probably refrain from using fuel pressure as a method of tuning as much as possible. Particularly if you are lowering pressure. Injectors are designed to operate at a particular relative pressure(manifold vs fuel rail). I would be more comfortable increasing pressure than lowering it to a certain degree. Lowering pressure can mess up the spray pattern quite a bit compared to increasing it. Think about a simple twist type garden hose attachment. Set it to spray at about 45 to 60 degrees. You increase hose pressure and the spray pattern remains for the most part in tact but sprays out faster. Turn down the pressure and at some point the pattern distorts heavily, enough that it becomes a stream of water rather than anything that resembles a "spray". While the stock fuel pressure is probably well above the point where this may occur, I'd just rather not take chances. Keep in mind when you lower pressure the size of the droplets in the mist become larger as well. This makes it harder to atomize the fuel during the compression and combustion process. Too high a pressure can also be bad. Flow from the pump is reduced when you increase pressure. Which is why an FMU is so limited. Adjusting fuel pressure to a small degree should be fine(a few psi). But I wouldn't use it as a way to compensate for larger injectors.

[Jookmasta]

so should i upgrade to the z32 maf then? or should i upgrade to the s14 maf?

[C-Kwik]

If you are going to upgrade, I'd go for the Z32 MAF. the S14 MAF will max out perhaps only a little higher than an S13 MAF. Depending on where the S13 MAF maxes out.

[tapdeznutz]

just to get this straight everyone is talking about te turboZ32 maf right or any z32 maf will work. just had to cler it up for me thankx

[andrave]

they are the same

[kevdog240]

ok, so after reading these posts it kinda seems like i should be switching to the z32 if i am going to be running a system at 7psi with the e-manage or s-afc? is that really necessary or is it just extra careful? also, what about 10psi?

[huguetpj]

7PSI, not needed. 10PSI, don't think so. I've gone up to 9PSI with my stock S13 MAF with no ill effect. Although I have yet to measure MAF voltage

[kevdog240]

how exactly do you measure MAF voltage?

[huguetpj]

how exactly do you measure MAF voltage?

Measure voltage from the signal line to chassis ground...

[Jookmasta]

so then z32 maf it is. cuz i want to run the 12 or 13 psi and im assuming correctly that the stock s13 maf wont cut it right?

[huguetpj]

so then z32 maf it is. cuz i want to run the 12 or 13 psi and im assuming correctly that the stock s13 maf wont cut it right?

I don't believe it will reach 12PSI. But I haven't tested it myself. When my car is out of the shop I'll connect the SBC to the MAF and let you know what I'm getting at 9PSI.

[Jookmasta]

cool; please keep me posted cuz it seems that i cant find anywhere that has info on when the stock s13 maf maxes out