2g mass air sensor in a stock 1g...

[dnhieu]

i know i should only do this if i got 550cc injectors, but has anyone actually done this to there car before and logged it? any knock? did it make more power??? just curious because i have a 2nd gen mass and intake pipe i would like to put on my beater...

thanks in advance
david

 

[CanadianTSi]

Your going to be roughly 20% to LEAN all the time...

 

[steve]

If you have the right tuning tools you can switch to a 2G MAF anytime.
What you can't do is swap the MAF and some 550 injectors at the same time and not have to tune the car.

Steve

 

[LaN-]

I know of people that have ran the 2g mas without doing anything, but it never ran perfect.

The right way to do it is to get an Eprom ECU and set it up for a 2g mas.

What are you trying to accomplish?

 

[steve]

The right way to do it is to get an Eprom ECU and set it up for a 2g mas.

That would qualify as the prefered tuning tool in my book.

Steve

 

[titogs95]

Your going to be roughly 20% to LEAN all the time...

No offense, but how you came up with this number? According to this post located in this thread 2g Mas flow 33% leaner.

and According to this tunning guide a 650CC injector flows about 33%. So, they cancel each other with the 2G Mas. But you still will need a Tuning device no matter what.

 

[dsm-onster]

Thanx for the links to these posts. I've always been told a 2g maf puts out about 20% lower signal for the same airflow as a 1g maf.

According to dsmchips, to whom DSM90AWD refers in that thread:

At 1000 Hz:
1G MAS = 90 liters per second
GVR-4 MAS = 94 liters per second
2G MAS = 119.5 liters per second
3G #482 MAS = 150 liters per second
EVO 7/8 MAS = 150 liters per second
​

I suspect the actual curve of the tranfer funtion is not the same as well. If they are similar curve shapes, one can apply the same correction factor for fuel flow as airflow when they are swapped. The Dsmlink manual shows the correct way to correct fuel. Applying this to maf signal changed:

(old meter reading)
------------------------- - 1 = percent correction factor
(new meter reading)


90 liters per second
------------------------------ - 1 = -0.25
119.5 liters per second


Or -25% correction, NOT 33% correction.

See Converting Karman to AirFlow for the whole thread.

550s need an -18% correction factor. 650s need a -31% correction factor. 680s need the -33.8% correct towhich you refer.



Now applying a different fuel pressure affects injector flow by a certain flow factor:

sqrt(NewPress / OldPress) = Flow factor

[450cc / (new injector cc) / (flow factor)] - 1 = injector correction factor

One can have 550s to flow enough for a -25% correction factor by creating a 1.09 flow factor. Knowing that a 1G runs at 37 psi base, this comes to a hair over 44 psi to create that flow factor number. So if you swap a 43.5 psi 2g fpr (include the fuel rail for fitment), it should cause a set of 550s to flow nearly perfect at 1000 hz w a 2g maf. Lowering the fuel pressure to the neccesary correction factor when using 650s is not something I'd or recommend. So 550s are better here. Raising the stock fuel pressur eon a 1g is a way to get the most out of your 550s anyway. At 37 psi and 80% IDC, 550s flow enough for a little over 310hp. At 43.5 psi, 550s flow enough for almost 340 hp.

But, who has done this is the question.

 

[titogs95]

dsm-onster, That is really good. Thanks for the Info and confirmation.
I will be sending you a PM to leave this thread on topic.

 

[dnhieu]

well you guys are 100% correct. i wired one in and im picking up 8 counts of knock now . i definetly just switched back the 1g mass...