# hp - MAF(g/s) correspondence



## checcoa3 (Sep 15, 2011)

hello guys,

I have seen many sites and forums, which give an idea of the horsepower of your engine you need to do the following calculation:

(value MAF g / s) / 0.82 = hp


you also use this method?

logically it is less reliable than a test bench.

try! and await your results.


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## BlueSleeper (Nov 9, 2002)

checcoa3 said:


> hello guys,
> 
> I have seen many sites and forums, which give an idea of the horsepower of your engine you need to do the following calculation:
> 
> ...


It also depends on the size of your MAF housing.


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## groggory (Apr 21, 2003)

BlueSleeper said:


> It also depends on the size of your MAF housing.


Why?

I thought it takes x amount of air to combust with y amount of gas. If you know the air, you know the gas. If you know the gas then you know the amount of energy that is combusting. If you know the energy then you can convert it to any form you want...hp for instance.


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## need_a_VR6 (May 19, 1999)

If you change the housing and not the calculated value the g/s is off.


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## groggory (Apr 21, 2003)

need_a_VR6 said:


> If you change the housing and not the calculated value the g/s is off.


That makes sense. I was assuming that the housing matched the software and the software gave you an accurage g/s


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## Turbo freak (May 9, 2005)

You can see how off is your MAF/tune calibration by checking how much your ecu is adapting fuel i may think.

Is that .82 number the AFR?


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## checcoa3 (Sep 15, 2011)

I do these tests using the vag com.

For example, last night I tried one, audi s3 210hp, with mapping. The MAF has scored 195 g / s.
so it should have about 240hp, the value seems realistic.


written by ross-tech: 
"
if you have a stock 150 hp 1.8T, expect around 120 g / s. If you see Significantly Less Than That, You May Be MAF on the way out. This still works if you are chipped, but "race" programs May make more power through timing, Rather Than airflow. Therefore, take all readings with a grain of salt. 
"


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## checcoa3 (Sep 15, 2011)

collect your experiences I'm curious.


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## badger5 (Nov 17, 2003)

I use g/s divide 0.8 as a ready reckoner, and it often corresponds to bhp on my dyno.

It can take no account of ign or fuel quality however, but on stage 1 remapped cars its pretty close estimation.


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## checcoa3 (Sep 15, 2011)

well!

therefore, much higher than for processing, it is not very reliable?


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## RobbieRolex (Sep 5, 2011)

badger5 said:


> I use g/s divide 0.8 as a ready reckoner, and it often corresponds to bhp on my dyno.
> 
> It can take no account of ign or fuel quality however, but on stage 1 remapped cars its pretty close estimation.


 
Dito, i always go by the / .8 rule.


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## checcoa3 (Sep 15, 2011)

other experiences?

I know to say how much influence a MAF 3 "with K03? mean in terms of income ....


mount it worth?


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## audis3gr (Feb 23, 2009)

i saw 255gr/s at my big turbo setup,the maf case is from audi rs4(82mm id)and perfect calibration,the idle and low throttle is like oem!!the rs4 maf flow 37%more than stock 70 mm id maf case,i use this
http://www.unitconversion.org/flow-mass/grams-per-second-to-pounds-per-minute-conversion.html
to calculate the lb/min the turbo compress and send to the motor,
255*1.37=349gr/sec(real flow) which is 46lb/min and almost 460hp,

i saw these readings at 1.6bar


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## [email protected] (Jul 1, 2009)

OP: don't overcomplicate things by factoring different MAF sizes and compensation values. Just ensure your g/s readings are true, then divide by .80 for a reasonable estimate of power.


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## audis3gr (Feb 23, 2009)

At my ecu it cannot display more than 299gr/s so i
See maximum at 299 with calibration but i must calculate to find the real gr/s,if i divide the 255 with 0.8 i will not take right numbers!


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## checcoa3 (Sep 15, 2011)

but you think it is useful to mount a MAF 3 ", with K03 turbo?


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## Turbo freak (May 9, 2005)

checcoa3 said:


> but you think it is useful to mount a MAF 3 ", with K03 turbo?



You only change the MAF diameter when you max the MAF reading of a certain size. There is no point to put a 3" MAF housing while using a K03, it will never max the 2 3/4" MAF.


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## audis3gr (Feb 23, 2009)

Turbo freak said:


> You only change the MAF diameter when you max the MAF reading of a certain size. There is no point to put a 3" MAF housing while using a K03, it will never max the 2 3/4" MAF.



Exactly!no point to change it until you max out the readings!


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## tedgram (Jul 2, 2005)

I had signs my 3 year old MAF sensor was going bad. Bought a new one and put the sensor in my over sized housing. I'm thinking it's the wrong sensor. I'm getting 308 G/S with a stock K04 @ 25# of boost and Cat 51 intake cam. There is no way I'm getting that kind of power.


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## checcoa3 (Sep 15, 2011)

to read the right value of MAF, in which gear you have to try?


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## The_RoadWarrior (Nov 21, 2011)

audis3gr said:


> Exactly!no point to change it until you max out the readings!


How about removing the flow restriction that the MAF housing ID can create?

Say you have good size V-stacked filter and an 80 mm TIP (think badger5 awesome TIP), creating a bottle neck with the maf housing is going to result in less mass and laminar flow :thumbdown: . 

Ask me how I know? 
I run a 42 DD intake and using a 3" ID Audi S4 Housing, although at 245 G/S I not near maxing out the sensor voltage, I gained substantial flow registered at the MAF (calibrated the reading with margin of error to account for the the bigger cross section) :beer:


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## tedgram (Jul 2, 2005)

checcoa3 said:


> to read the right value of MAF, in which gear you have to try?


3rd or 4th gear work best.


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## The_RoadWarrior (Nov 21, 2011)

How accurate is this calculation really? For example, the amount of heat removed by intercoolers (depending on the efficiency), showing at the IAT sensor, will call for timing correction. Even on a car with only a chip or some basic mods this calculated power figure will be wrong. 

In my case, at 245 G/s I'm making well over 300 WHP and boat load of torque :screwy: .
My factor should be something like a 1.3-1.4 ; timing and how lean/rich the AFR curve is, will create some serious power that is not accounted for in this calculation.


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## checcoa3 (Sep 15, 2011)

I do a test tonight.

I put the original mapping, I want to see as it marks the MAF!

However from what I understand the method is quite real if there are extreme changes.


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## checcoa3 (Sep 15, 2011)

Hello guys, then last night I tried the original mapping.

result:

134 g / s from MAF
13.1 / 13,3:1 with a stoichiometric ratio at full throttle.

in the coming days I will test with the new mapping.


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## checcoa3 (Sep 15, 2011)

Hello boys

some of you have done other tests?


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## spartiati (May 19, 2008)

Max I think the factor for you is the e85. That will skew your actual power output vs Maf reading. In other words with e85 you can make more power with the same amount of air.

The reading is pretty damn close. When I ran a S4 maf I hit 305g/s peak. 
305/.8= 381.25 CRANK HP
now lets assume 15% drivetraing loss for my FWD GTI
381.25 CRANK HP*.15(drivetrain loss) = 57.19hp

381.25 CRANK HP-57.19hp = 324.06 whp

My dyno at the time was exactly that. 324whp. I'd say its pretty damn close.


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## checcoa3 (Sep 15, 2011)

what is e85?


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## Budsdubbin (Jul 14, 2008)

spartiati said:


> Max I think the factor for you is the e85. That will skew your actual power output vs Maf reading. In other words with e85 you can make more power with the same amount of air.
> 
> The reading is pretty damn close. When I ran a S4 maf I hit 305g/s peak.
> 305/.8= 381.25 BHP
> ...




I'm not sure if I understand how does 305.8 = 381.25 Bhp. I was under the impression that MAF readings correspond directly to crank hp.


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## spartiati (May 19, 2008)

sorry that was before my cup of coffee in the morning. Yes that's what I meant. Lol. I'm a zombie until I get my "fix" haha...

corrected now.


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## MidnightG60 (Aug 16, 2004)

Back from the dead but...

Just did my initial logging for my stage 1 Motoza Tune. Best maf reading was 154.41 gs which equals 193 crank HP. Not too shabby for the base tune and stock intake/cat/dp. :thumbup:

Only mods are panel K&N filter, reversed 710N, and newest revision N75. 

Excited to see what the next revision of the tune will put out on 91...


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