Real limits of MAFT?

[vteckiller2000]

What are the real limitations of the MAFT?

I am aware of the way it works, and that when limiting the air mass data you can also increase timing to the point where it is dangerous and difficult to tune for pump gas due to knock, but what is the actual limit to the system?

Has anyone succesfully tuned a MAFT with a larger turbo, such as a holset hx35 or something bigger than the garden variety 16g?

I know that big 16g's are used with 2g MAS fairly successfully and since the functionality of the 2g MAS in that application is the same as limiting the air mass data with a maft, I am curious.

(obviously I am using larger than stock injectors in this hypothetical scenario)

 

[HustlerTalon]

MAF sensors operate by measuring pressure, temp and volume. The ecu takes that data and multiplies it out to calculate air mass. Air mass is then used to calculate fuel mass required to achieve a 14.7:1 Air/fuel ratio. That fuel mass is then used (along with the ecu's idea of which injectors are installed on the car) to calculate injector pulsewidth. And then that is finally used to schedule the injector firing events.

But it all starts with airflow measurement. Like all devices, maf sensors were designed to operate in some pre-defined range of operating conditions. One of those, of course, is the volume of air flowing through the Maf sensor. When the true volume exceeds the measuring capacity of a maf sensor, you end up with an erratic volumetric output. The erratic output feeds into the fuel calculation described above to produce an erratic a/f mixture. And that produces erratic engine operation, typically while you're running wide open throttle

 

[bastarddsm]

blah blah blah

way to try and earn rep points while not actually answering the question.

A 2g maf will measure into the 50lb/min region. Thats 500whp on E85, if you want more, look elsewhere.

A 3" gm maf should measure into the 70lb/min region, thats enough for 700whp, on good fuel.

The limit for a maft depends on your definition of limit. If your planning on running a stock ecu and using the maft to tune, the limit is in the 450 whp territory. aka, thats about the most people have gotten out of that setup. The problem is you'll run into issues with timing because of the size of injectors you'll need to run to support that much airflow.

Now if your going to do internal code mods to the ecu, or run dsmlink, the limit is much higher, probably closer to the 70lbs/min that the gm maf will measure.

Finally if you ditch the maft and use a dsmlink adapter cable, you can run it much higher than the 70lbs/min a gm maf can measure, when you use the maf clamp feature.


I personally run the 2g maf, and I am in the 48lb/min region with it. I'm planning on trying to run a 3"gm maf and making a adapter cable.

 

[Calan]

50lb/min region. Thats 500whp on E85, if you want more, look elsewhere.

A 3" gm maf should measure into the 70lb/min region, thats enough for 700whp, on good fuel.

The 10 horsepower per lb of airflow rule is used as a VERY rough estimate of BHP, not horsepower felt at the wheels.

 

[NOSLO2PT0]

Info here.

http://www.ecmtuning.com/wiki/maffrequencylimits

3" GM MAF = 80lb/min
3.5" MAF = 92lb/min!!!!!

 

[bastarddsm]

The 10 horsepower per lb of airflow rule is used as a VERY rough estimate of BHP, not horsepower felt at the wheels.

OH jeez lets nitpick. On e85 or other good fuel it ends up being around 10whp to the lb/min. On pump gas its around 9. But all of that has to do with way more than the fuel type. So nitpick away at that too.

I'd seriously like to know what research you have done to negate my claims. Its a well known fact that oxygen bearing fuels generally tend to make more power for a given volume of air than standard fuels do. Why the #### do fuel cars make so much power if this wasn't true?

Oh and I guess I was off on the maf readings.. to lazy to look it up, but still, my point stands. The GM maf will read to 70lb/min and beyond, and people have made 450whp+ on a maft.

 

[Calan]

OH jeez lets nitpick.

Call it what you want; but there is a big difference in crank hp and wheel hp.

On e85 or other good fuel it ends up being around 10whp to the lb/min. On pump gas its around 9. But all of that has to do with way more than the fuel type.

So why mention the fuel type at all then?

In fact, the fuel type would have very little to do with anything, other than determining how much cylinder pressure you can develop without knocking. If your gonna mention that, you might as well mention the AFR, timing, etc. etc. So in other words, it could be 3hp per lb/min or 15hp per lb/min.

We're getting OT here... I think the OP has his answer.

 

[vteckiller2000]

Excellent. I figured the timing would be the limiting factor when injector size went up.

 

[tkelly27]

Before modification of the factory ECU code became easy and common people would adjust base timing with the CAS to make up for the discrepency caused by the MAFT. This will make it run poorly under non-wot conditions, but you weren't asking how smoothly you can make your car idle or what kind of fuel mileage you can get.

You can buy a chip burnt with better timing tables that will let you extend the effective range dramatically. A chip can even make a SAFC a fairly powerful tuning option.

I wouldn't do any of those. I would edit the eprom, be it through link, an ostrich, or burning proms. You can get an eprom burner, 20 eproms, UV eraser, and a soldering iron for ~$100.

 

[NOSLO2PT0]

Oh and I guess I was off on the maf readings.. to lazy to look it up,

NO rep points for you either!!!! HAHA

 

[vteckiller2000]

Before modification of the factory ECU code became easy and common people would adjust base timing with the CAS to make up for the discrepency caused by the MAFT. This will make it run poorly under non-wot conditions, but you weren't asking how smoothly you can make your car idle or what kind of fuel mileage you can get.

You can buy a chip burnt with better timing tables that will let you extend the effective range dramatically. A chip can even make a SAFC a fairly powerful tuning option.

I wouldn't do any of those. I would edit the eprom, be it through link, an ostrich, or burning proms. You can get an eprom burner, 20 eproms, UV eraser, and a soldering iron for ~$100.

What kind of software would I use though to burm eproms? I know that is what everyone did ten years ago before flash technology was widely used, but I have no idea about the mechanics of a setup. Hence using a maft and adjusting timing with the CAS or an MSD BTM type device (which I used on my old turbo miata 7-8 years ago).

 

[bastarddsm]

Call it what you want; but there is a big difference in crank hp and wheel hp.
So why mention the fuel type at all then?

In fact, the fuel type would have very little to do with anything, other than determining how much cylinder pressure you can develop without knocking. If your gonna mention that, you might as well mention the AFR, timing, etc. etc. So in other words, it could be 3hp per lb/min or 15hp per lb/min.

There sure is a big difference, and I never stated there wasn't. I stated my numbers based on personal scientific research. Running E85 or other highly oxygen bearing fuels will result in 10+whp per lb/min of air. Pump gas and other standard type fuels will be in the 9whp per lb/min area. Like I said previously, fuel type has every bit to do with the amount of power an engine can make with a given amount of air. It is a well known fact that an oxygen bearing fuel will make more power than an standard fuel of the same detonation resistance. If this wasn't true, why would people run nitromethane for power?

Anyway, the fact is, the guy asked what the limit of a maft is, and I gave him credible estimates of what it is. Then you come along trying to get your gold star for the day, and attempt to nitpick with your superior "wiseman" status, and pull the thread way ot.

What kind of software would I use though to burm eproms? I know that is what everyone did ten years ago before flash technology was widely used, but I have no idea about the mechanics of a setup. Hence using a maft and adjusting timing with the CAS or an MSD BTM type device (which I used on my old turbo miata 7-8 years ago).

Personally I use TunerPro R/T, its probably the easiest and best supported way to mod the stock bins. Its defiantly hobbyist software, as you have to learn how to mod the code before you can tune.
Some people just use a hex editor to mode the code and burn it to a new chip.
These two methods are definatly best for people who like to constantly tinker with stuff.

Finally, you can get the dsm link. You bascially install it and start tuning. Way more friendly to someone that just want to tune and be done.

Check this stuff out.
First Generation DSM EPROM Editing
dsm-ecu : DSM-ECU
dsmecu.com