87hellbird

I was reading on a supra board about how they trick their computers by putting a bigger maf on the car from a different car and then it would allow them to put bigger injectors. So it got me thinking... I have 2 maf's one that is broke and one that is new, if I put a y pipe and put both on to split the air flow into 2 even halves with only the good one sensing half the air, could I put 38# injectors in instead of 19? and would the idle be all messed up? If it were possible I would do this with 2 small turboes into a y into one inlet then to another y to make sure the air is even not one turbo pulling more then the other. Then pull timing and... but would this idea work first?

RyanJB

Honestly, I'm not sure I understand your question properly.
You're basically trying to use two MAFs so you can use a larger injector?

If that is the case, it would not work. At all. The ECM only takes in one MAF input, so one would be totally ignored unless you did some serious modification to the firmware of the ECM. It would be much easier to just change the injector constant in the ECM to 38#...

87hellbird

it wouldn't pick up from both, it would only pick up air from one but I would have a y pipe with the main one going to the turboes the other 2 ends having 1 dummy maf and the other y with the real maf to make sure the air is split perfectly in half for both mafs. so the computer is only reading half the air not all of it.

RyanJB

Well, reading half the air is going to make it deliver less fuel not more.

If the one MAF is just going to be a "dummy" and not provide data to anything why even have it there?

87hellbird

to make sure that the engine doesn't suck more air from that side, basically make sure the intake has the same resistance on both halves, and it would tell the inj to put half the fuel in that's why I could double inj size to off throw both sides of the spectrum and make it the correct fuel to air ratio and possibly go twice as much power from turbo. If the maf says that im pumping 300 cfm but since its only half the cfm for 600 cfm then having twice the inj would fill the 300 vs 600. The reason for it is 19's are prob good for like 250-300 maybe but 38s I could have a turbo at 450-500

87hellbird

in other words if it only sees half the air, and you still had 19's in then it would only put half as much fuel in, so if you double the inj size to 38's it would dump the correct amount. the most restrictive thing in my pipeing is the maf so to make sure that one side doesn't suck more then the other it would need the same resistance hence 2 mafs, one dummy to just make sure its the same and one real to measure half the flow.

Street Lethal

iTrader: (16)

In a naturally aspirated situation, the MAF is not the restriction, the ECM is. If you are looking to run boost with a MAF though and are worried about it being an obstruction, just do what the GN guys do, run a simple LT1 MAF w/translator, then burn a chip accordingly to work with it. No need to run two stock MAF sensors...

87hellbird

I mean restriction after the y pipe to make sure the cfm that goes into both sides is the same. Im not worried about the restriction I just have to match both sides to make sure exactly half the air goes through both sides so I can double the inj to make up for the missing cfm. I am basically trying to trick the computer

RyanJB

Why try to trick it with this overly complicated set up when tuning is relatively simple? Especially when there's so many different options available.

Street Lethal

iTrader: (16)

He can't trick it that way. He forgets that the Supra ECM's are already tuned for boost pressure. Doubling the injector size without telling the ECM, nor rescaling the MAF tables is a bad idea. I already mentioned that the MAF is not the restriction, the ECM is. He doesn't need two MAF's or two intake tubes to achieve double the flow of air, that will not work. One turbo and one MAF will get it done, throw in the 38# injectors, tune the MAF/LV8 values, and enjoy the ride. The other way is a bad idea...

Street Lethal

iTrader: (16)

The other way he is trying to describe would be like throwing in larger rods and jets in a carburetor to compensate double the horsepower over what it is already making, then running a turbo at 15-psi giving him enough fuel to cover the boost, same difference. However, two tubes and two MAF's become irrelevant in that case. One turbo, one MAF, 38# injectors, and 15-psi of boost with a tuned MAF/LV8 will do what he wants properly...

tmellott89

Dear ECM, April fools. If being "even" able to trick the ECM, id imagine it screw up all the data that you would log anyways taking longer to tune if you even can than if you was to do it right. Nothing would ever be accurate.

tmellott89

Forget the turbo just run your exhaust strainght to the throttle body, that will build some pressure.
No using MAF and the right injector you can hack around the code for it to be alright with boost, invest in a wide band setup. ive went 12.60 on 5psi with MAF so far, and its still not a good tune im sure i can get a little more out with wideband. wideband is key part here.

junkcltr

iTrader: (1)

The ECM being a restriction is false. This is a myth that floats around about the TPI MAF ECM. The TPI MAF itself is the electrical restriction. It outputs 5v at 255g/sec. By putting an equally flowing pipe in parallel with the MAF, the ECM will see 2.5v at when the engine is flowing 255g/s. This will allow the ECM to see 510 g/sec at 5.0v.

The ECM will need tuning for any engine modification including boost. Just put the pipe in parallel and tune the fuel and timing curves. Just like the MAP ECMs, a factor of 2 resolution will be lost due to the 2x increase in dynamic range.

junkcltr

iTrader: (1)

This what you want to do with the MAF for air control. A MAF reads air through it. Th TPI MAF sends 5v to the ECM at 255g/sec (or 330HP) worth of air through it. With the pipe in parallel it will now be able to read up to about 660 HP worth of air at 5v into the ECM.

The fuel injector pulse width is Airflow * (fuel/air ratio) * (1/injector size). Suppose you 1/2 the air (but don't tell ECM it is 1/2 in the MAF tables) and 2x the injector size (but don't tell the ECM the injector is 2x). Now you have, (airflow/2) *(fuel/air) * (2*1/injector size)). As you can see, the "2"s cancel out making everything seem fine in terms of how much fuel went into the engine.

Other parts of the code look at the MAF reading so those need to be adjusted. For example, suppose at idle the ECM checks the MAF g/sec to make sure it is in range. Lets say it should be 64 g/sec, but with the pipe it will be 32 g/sec so the check engine light comes on.

End result, your idea is valid. The ECM will need some adjusting for the MAF values.

junkcltr

iTrader: (1)

Side note, the TPI MAFs failure rate always seemed higher than the later MAFs. That is one reason why I try to stay away from them. What is the price for a TPI MAF these days?

MAP sensors are cheap. You may want to look at putting the Aussie $12P code with MAP in your stock 165 ECM.

Street Lethal

iTrader: (16)

... considering the fact that every Turbo Buick racer that upgrades to an LS1 MAF w/translator are all still relegated to 255 gr/per second in their GN OBD1 ECM until the proper chip raising the gr/per second values to either 512 gr/per second, or 768 gr/per second is installed, I am forced to disagree with your theory.

junkcltr

iTrader: (1)

Going by what others do and say instead of looking at the HW and SW yourself leads you to disagree.

Street Lethal

iTrader: (16)

What exactly would you like me to look at? This was explained then later proven to me by an owner running a stock MAF sensor setup in his GN. You stated that the restriction is in the MAF and not the ECM, and I have stated that the restriction is in the ECM and not the MAF according to what was demonstrated to me. Companies such as Commander, Max Effort, Full Throttle and Turbo Tweak all make chips to well exceed the alleged limitations of the stock 5v frequency MAF, and lets not forget the original author of this thread is only shooting for 450-500 horsepower, something that a stock GN could accomplish with the stock 5v MAF, larger injectors, and Turbo Tweak chip. The main reasoning behind newer MAF's were for increased size and cooling capacity, as well as the fact that GM discontinued them, with the translator allowing the OBD1 ECM to communicate with the increased Hz. Rescaling the MAF in the bin creates a 0-512 grams/per second airflow capacity, but despite that, let's entertain your theory for a moment, do you honestly think there aren't other ways to add fuel in the bin as cfm increases above the MAF? The author of this thread is not a tech savy, he wants to accomplish this mechanically, which may very well work for him, but it's wasted effort. Incidently, Supra guys don't waste their time with bigger MAF's with translators, they go Speed Density, just like the GN guys do...

Orr89RocZ

iTrader: (20)

I thought latemodel maf were different than out thirdgen mafs? Late model output frequency while ours is volts related? Hence reason for translator

In any case when you bypass the maf like the OP wants to do, you will read theoretically half the airflow. The maf tables in computer only have inputs up to 255g/s. I dont think you can simply put 512 in for 5 volt location.

I made a 3.5" maf using stock maf internals. Result was 255 g/s limit still but since more air was getting in passed the sensor, you were extremely lean. Had to greatly increase maf values for each volt point in maf table 1-6. I recall 255 being my limit and i now reached that in table 3 or lower table 4 i cant remember.

I suppose you could have cut injector constant in 2 and done same thing to trick fueling and end up leaving maf tables alone

Regardless of all that, i would go speed density and be done with it.
edit: speed density for turbo car. Maf could work for centri blower as boost is predictable and linear with rpm. Use pe mode % enrich vs rpm to deal with that. Timing could also just set max lv8 to whatever timing it needs at said boost with centri blown cars. Turbos are variable so speed density is best

Street Lethal

iTrader: (16)

It's funny how we're discussing stock MAF sensors, I wouldn't recommend Mass Air Flow to anyone as it is, but I don't see how a stock MAF couldn't provide the power that the author is looking for, up to 500 horsepower in this case through a new chip. I think in the old days, turbo guys running the stock 5v MAF's would max out the PE tables and tune the engine with fuel pressure if I remember my reading, and it worked fine. I mean think of it this way, a larger MAF will allow the ECM to measure "true" cfm as opposed to fudging numbers, but when both methods are showing the correct air/fuel on the wideband, both will give the same results. I guess it's a matter of the "true" vs fudged measurement of cfm that bothers people. Anyways, I'm done, it's not worth arguing about anymore especially since most of us run Speed Density. Looking forward to see both Dave's and your progress with your Camaro's...

Orr89RocZ

iTrader: (20)

I think the problem is the stock maf is only calibrated to 255 g/s at 5 volts. I am not sure but this seems like the case.

If there was a plug and play 0-5 volt sensor that read to 510-ish g/s then i think someone would have found out about it now.
The only ppl who run different maf is with a translator. Blowerworks.net does a larger maf with custom chip to allow it to be used on stock ecm electronics. Not sure what all changes or if it also runs a translator
Tequilaboy on here would know for sure.

junkcltr

iTrader: (1)

Putting 2 TPI MAFs in parallel and reading one MAF v_out 0-5v into the ECM makes the "system" run as a single MAF with 510 g/s at 5v.
This is the same as taking a late model Freq MAF with a translator making the Freq into an analog 0-5v voltage. The code could do a 2x on the value read by the A/D and retain that as the stock MAF reading, then an extended MAF variable indexes above 255 g/s for the A/D above 2.5v. Could also just relabel the tables to by the new max g/s from the MAF and adjust all the other MAF compare values. Be it a parallel TPI MAF of translated Freq MAF..........same same.

This is essentially how I mod the SD code to run a 2/3 bar MAP sensor and retain most of the original code. I do the 2x and created new variables/tables for boost. Most people don't understand how to do it.

OP, your idea is valid using the parallel MAF and 2x injectors, but you still need to change the MAF compare values to keep the code happy.

junkcltr

iTrader: (1)

87hellbird,
I looked through the MAF code. If you made new XDF constants/tables for 19 items by doing a 2x on the gm/sec column, row, or bin value along with making a new XDF constant for the fuel injector with a divide by 2 on it then a freq translated MAF or your parallel MAF (up to 510 gm/sec) would work with the stock injectors or any other injector of your choice.

If you search a file called bau_hac.pdf for "gm/sec" you will see all the actual locations. Currently, the code uses 1 gm/sec per bit which becomes 2 gm/sec per bit with the new MAF setup.

87hellbird

So from what I am understanding from junkclrt is that the air to fuel measures would be right however since the values of the maf would be off from what the computer expects it would need tuned back right. Would this make the engine not run right or just the check engine light come on and would it be at all throttles and rpm or just idle? And I do now see what street lethal was saying about the maf being the restrictor.

junkcltr

iTrader: (1)

Doing this with a GM or any other manufacturer ECM/PCM requires tables to be modified.

An example, Pick the so-called "VE / load" table and pick RPM at 5000 and MAF at 255 gm/sec. The ECM pulls out a value of say 86% for VE with the stock MAF setup.

Suppose you put in a translated or parallel MAF setup. The ECM will now pick out the "VE load" value located at 127 gm/sec which is say 98% for VE. As you can, you wanted to get 86% but you got 98%.

If you fix up the labels on the tables then you can then move the values around to the correct position.

He was saying the the ECM is the restriction, not the MAF.
Simply changing the tables........or not changing them and "re-tuning" is probably how the other guys do it without understanding they are essentially just moving existing values around.
You will get a check engine light. You probably won't notice a difference in behaviour depending on how good of a tune you are used to. People spend 100x time more tuning than doing the simple table mods up front.

87hellbird

This maybe a dumb question but if you didn't tune it with this form of induction and large injection wouldn't the computer just adjust off the air flow difference sensed by the maf to run right from a turbo? Or is it based off only one curve. I very well could be wrong just not the most knowledge able on the computers in these

junkcltr

iTrader: (1)

It wouldn't adjust.
You would have to tune the load tables for boost.

The cheapest way to do what you want to do (not mess with the ECM) is to install a nitrous fuel soleniod and hobbs switch to turn it on for the "extra turbo fuel".

87hellbird

Ok that all makes sense! Thanks everyone! It was just an idea that came across me while I was in a junkyard one day haha I am more knowledge able with more carb tuning haha

junkcltr

iTrader: (1)

Great ideas come from the yards.
Turbos + carbs work too. Try the fuel solenoid with that too.
Once you go turbo, driving stuff without them is un-inspiring.