I see alot of people max out the factory MAF at 600-700 rwhp depending on the setup. On blower/turbo mustangs you take the sensor out of the factory 2.5" sample tube (or whatever size it is) and put it in a larger sample tube (3"-3.5") and then the sensor can read alot more.

Would this work on an ls1, my fabrication guy wants to cutout the sensor on my stock maf and stick it in a larger tube and just go into ls1edit and change the airflow/fueling data the % change in total area that the tube changes, then fine tune from there.... this would allow 800-1000rwhp to be possible with stock PCM setup

 

I'm pretty sure you can add a resistor to change the read of the meter.You will then have to rescale a few table's.

P.S- still waiting for that present in the mail

 

Well I wouldnt think a resistor would work, because the MAF can only read a maximum certain amount...putting it in a larger sample tube, it would read less air at the same amount of airflow and you could compensate if you knew how to just change the fueling characteristics and timing to correspond with the new airflow readings coming in.

(all the readings would be alot less than they normally are so the car wouldnt run right unless all of the correct tables were corrected)


oooo..just realized this was kinder, yes that was sent.

 

well, Im not sure it would work or wouldnt. But the stock MAF is in a fairly large tube. I wouldnt think that it would help all that much.

Harlan is who should answer this question to know
ed

 

I did some searching and i see the resistor thing works just like a MAFT.....has this worked well for anyone trying 700-900 rwhp

 

You can't hang a resistor or anything passive on the MAF signal to make it read more. It's a freqeuncy output w/ a non-linear output based on flow.

You can put the sensing element in a large sample tube, that's what you do when you port your MAF or buy MAF end's. You increase the opening, report the same flow, and in effect lean the mixture. Only a few percent though.

the problem is not the MAF maxing per say, as you hit the limit of the PCM to read frequency or read g/s depending on which MAF you have. The plastic 85mm ones hit the frequncy limit of the PCM just about 400 g/s, but the metal F-car ones hit the g/s limit of 512 before they run out of frequency range.

it's a PCM limitation, that requires additional fueling via PE once you can no longer read the actual air entering the system.

same meter in larger tube is exactly what Pro-M does.

 

The mustangs use a different setup in their MAF, they have a sampling tube that is replaceable that allows them to calibrate their MAF. As far as the LS1's we don't use the same type of setup.

-Sly

 

well you can't make it read more, but you can make it read less which gets you to the same end
You can use resistors or pots on the sensor bridge to reduce the output of the maf's frequency vs airflow.

You can use a resistor to cut the maf output by 1/2 or any % you wish and just edit the maf tables to match. Been doing this for the last 4.5 years now. The Maf's output will still follow the same slope, but reduced.

You do lose resolution when doing this and no way around that I know of. But I have never noticed a drivability loss with the output cut even above 50%.
Putting the sensors in a larger housing would work also, but the flow curve might be changed a bit and you might really have to do some work on the edit tables. The 85mm maf housing is plenty big for most guys , especially if on the pressure side.

Steve

 

S_J_H what value of resistor have you been using to cut it in half.

Ryan

 

At those hp levels you need not worry about how much you can read as how long that MAF will actually last. Many people blow apart the stock MAF's when shooting for huge power levels in forced induction. Harlan has 2, so he's only running say 500 hp through each.

 

Why not use a bypass ?? say an 1" diameter tube bypassing the MAF ( or larger ). Ive heard of people doing this on some cars when larger injectors have been fitted to fool the ecu into thinking it is getting less air, and therefore it gives less fuel. With proper tuning, it would allow more air into the engine, without maxing the MAF, but it should still provide a consistent airflow reading to work with.

 

Been a while since I ran it at 50% reduction or more. I don't need that much range with my G-trim, up to 67lbs/min is about all I need now .
I used to run that much reduction before ls1edit was available and I was using 42lb injectors at 65psi with dry nitrous and stock tuning. This method used to be kept secret by the few who knew about it.
But just install a decent 1K ohm pot across the sensor bridge and start around 800ohms and work from there.
You need to first make some baseline runs logging maf frequency and flow rates. Preferably N.A.! You don't want to be dialing it in under boost!,lol.
Then edit the tables so you have double the fuel flow at 1/2 the current maf range. Injector tables is the usual place to edit.There may be other tables you need to edit as well, such as the trans shift pressures if using an A4 and spark tables as this will effect the calculated load.
Then calibrate the maf using the pot until it is showing VERY close to 1/2 of the flow of the baseline runs. Always begin tuning rich. I like to replace the pot after tuning is complete with a quality set resistor to keep the tune stable.
It takes a little testing and tuning. This should all be done on the same day so weather changes don't factor in and a wideband should be used also.
This method takes some pretty good tuning skills and is not for the beginners.
Steve

 

"But just install a decent 1K ohm pot across the sensor bridge and start around 800ohms and work from there."


i understood the rest of what you said but not that part. can you give a little more detail on installing it across the sensor bridge. how do you access the wires? do you run a wire inside the sensor and just solder something to them or get a conection from the out side somehow? thanks for this info, i am going to try it. seems odd people would hide this method.

some kind of set resitance would be nice. wouldn't there be a way to know what resistor to wire in there for a certain reduction in output? i know right now i would like to be able to read 50% more air. go from 60lb's to 90lb's. i think i could handle the tuning.

 

Drill a small hole through the maf and run the Pot wires through.You need a decent 10 or 15 turn pot, but a Radio Shack cheapie will get the tuning job done.
Solder them across the short and long rails like my resistor is in the pic.This way you can externally adjust the maf. Once your happy with your tune, desolder the pot and solder in a good resistor of decent wattage to be on the safe side.
You can keep the pot full time if you want to be able to fiddle with the mafs output.I used to run my pot wires into the car and could tune on the fly.
But I prefer to use LS1edit for minor changes now.
Most maf's have a bit of variance and each one may need a slightly different resistance.
We used to do some wild things with the mafs years ago before LS1edit came along. Managed to fry a few as well.

Steve

 

Ok, my turbo fabricator has an idea on this subject.

Say you need to support 1000hp and the maf cant read that high.

Tell me if this will work
Heres a budget cheap guy way we think would work:

What if i take my say 3" intake pipe that normally goes through the MAF to the intake.

Take that pipe and Y it into two pipes side by side identical, where you y it, make sure that its perfectly symetrical and splits perfectly to effectively send 1/2 the air down each pipe (this would be easy on the straight part of the intake piping on my car). Install the MAF one side of the pipe and for identicalness sake, install another MAF on the other side (I wouldnt even hook it up, just a dummy to make it identical) and Y the pipes back into 1 pipe to the throttle body.

Then just goto the injector flow rate table and double it to give double the fuel to the massair reading. The massair would still read very accurately but would only see half the air.

 

thanks sjh, i will be trying this soon.

C4, that is the idea behind the sample tube. for what you are talking about there is reportadly someone making a maf averager. it will take 2 signals and average them into one signal. i would think just reading one would be fine too.

what i like about the resitor mod idea is i see no reason why you would have to go a full double. i wont be pushing 120lb's of air anytime soon. 90lb's will take care of me for a long time so i will try and gain 50% more reading and not loose as much resolution if i can.

 

Why do anything to the maf since you can change the PE tables? Let the maf work as designed until the ecm runs out of calibration, then chenge the PE......why screw the maf up?

 

once the maf is maxed and you are tuning with the PE table the only thing you are basing your fueling on is rpm. if there is a temp change or other weather change or you decide to crank the boost up a hair then the fueling is all wrong again. if you can get the maf to read the air then it will compensate for those things.

 

When you change the signal to 50% you lose minimal resolution I would think.

What exact tables need to be multiplied double to make up for the resistor mod??

I would think MAF flow rate OR just cut injector flow rate in half and would put you almost right on the dot and then build your timing curves yourself like you normally would....just move the timing table #'s lower in the flow rate...

 

your also going to have to do something for the load/VE calibration, or engine displacement, as with the computer seeing 1/2 or 2/3 the air , you will be at a more agressive spark calibration, than you want to be.

Ryan