What does "pegging" the MAF really mean?
- Thread starter Pokageek
- Start date
Thanks Grady. In real life terms, what is the difference between pegging it at say 5000RPM vs getting a better meter and not pegging it at all? For example if I am pegging it at 4500 RPM now and I got a meter that didn't peg until like 6200RPM, what would happen? Would the car go faster? Generate more power? How much? Thanks!
The pcm don't know what to do from 4500 and beyond.
The last bit of info about how to fuel the motor was obtained at 4500.
Starting to see the prob here ....................
Additional airflow from 4500 and up
but
NO additional fuel flow
Possibly an opportunity for you to say Bye Bye to your pistons
Grady
The last bit of info about how to fuel the motor was obtained at 4500.
Starting to see the prob here ....................
Additional airflow from 4500 and up
but
NO additional fuel flow
Possibly an opportunity for you to say Bye Bye to your pistons
Grady
Yep. Thanks for the splanation. The last time (before a coupla other mods), the stock MAF ws doing fine through 271rwhp and 308rwtq - just FYI. I don't think I would bump my timing higher than 15* but that is where it was. I am pretty sure I am putting out 20-30 more HP now though. Still waiting to take it in and see. I got a lightening MAF just becase I wanted a bigger one but partial to factory.
WhiteDevil
New Member
yeah at 300rwhp i was pegging my 19# calibrated Pro-M at like 5,500rpm. I would just go to 4.9v and stop but the rpms were will going. I suspect i was just barely pegging it because at 5,800rpm it would go back below 4.9v so it did not make much of a difference for me. But if it was majorly pegged that could seriously mess stuff up.
Don 95Vert
Founding Member
We have a tech article on our website that explians exactly what happens when you peg a MAF in detail. http://www.lasotaracing.com follow the link to the tech articles and then go to MAF Info/using an SCT MAF.
In a nutshell, as Grady explained the PCM only aknowledges 5v max (with a tune)- actually without a tune the hard limit is 4.7v, but a tune can extend that to 5v. The MAF will generate voltage to battery voltage, but the PCM only sees 5v as max. When it happens, the PCM thinks there is no more air coming in, but there is, so it doesn't add more fuel. Then calculated load drops so timing starts climbing. A bad mix.
Don
In a nutshell, as Grady explained the PCM only aknowledges 5v max (with a tune)- actually without a tune the hard limit is 4.7v, but a tune can extend that to 5v. The MAF will generate voltage to battery voltage, but the PCM only sees 5v as max. When it happens, the PCM thinks there is no more air coming in, but there is, so it doesn't add more fuel. Then calculated load drops so timing starts climbing. A bad mix.
Don
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