[cjperformance]

Im just theoretically speaking here. I know its a just an approximation.

Reputable tuners have said 1 lb/min airflow = 10 hp. That is assuming your tune is perfect with spark, afr, etc... i gravitate to 1 lb/min = 9 hp because im a pessimist.

Regardless of the exact ratio, if you have a forced induction system consuming, for example, a max of 60 lbs/min and an NA engine consuming the same max 60 lbs/min. Would they be making the same peak power at the flywheel?

Do you have to account for the supercharger drag? Or does it somehow just magically work out in the airflow numbers?

[sr71bb]

Originally Posted by cjperformance

Im just theoretically speaking here. I know its a just an approximation.

Reputable tuners have said 1 lb/min airflow = 10 hp. That is assuming your tune is perfect with spark, afr, etc... i gravitate to 1 lb/min = 9 hp because im a pessimist.

Regardless of the exact ratio, if you have a forced induction system consuming, for example, a max of 60 lbs/min and an NA engine consuming the same max 60 lbs/min. Would they be making the same peak power at the flywheel?

Do you have to account for the supercharger drag? Or does it somehow just magically work out in the airflow numbers?

\\

GREAT QUESTION!!! One of the best if not the BEST forced induction shop in the country is AMP. They produce 1000+ HP cars like the were SKITTLES candy primarily utilizing modifed STOCK blowers, MAGNUSON, and PROCHARGERS.

I was told by their tuner that at full BOOST, an F1X can take over 100HP just to turn the blower assembly especially on some of the higher HP builds that are running over 30 pounds of boost. This is commonly referred to parasitic losses. As the boost level goes up, those losses increase. And as we all know, the MORE you compress air the HOTTER it gets hence the need for intercoolers to help control that.

The intake air temperature of a naturally aspirated engine is MUCH cooler than the intake temperature of a BOOSTED engine. All other things being equal, cooler air is of course MORE dense allowing you to burn MORE fuel and thus produce MORE power.

[Joshinator99]

Originally Posted by cjperformance

Im just theoretically speaking here. I know its a just an approximation.

Reputable tuners have said 1 lb/min airflow = 10 hp. That is assuming your tune is perfect with spark, afr, etc... i gravitate to 1 lb/min = 9 hp because im a pessimist.

Regardless of the exact ratio, if you have a forced induction system consuming, for example, a max of 60 lbs/min and an NA engine consuming the same max 60 lbs/min. Would they be making the same peak power at the flywheel?

Do you have to account for the supercharger drag? Or does it somehow just magically work out in the airflow numbers?

It’s the same. The supercharger parasitic drag would be reflected in the lower WHP number, that’s all.

[KingLT1]

The problem with using MAF lb/min to calculate HP is that the MAF maxes @ 86lb/min even though it may have plenty of ceiling in HZ.

I have setup a custom Math's parameter for HP in HPt using the PID 50408 x 50070 / 5252. It gives you fairly accurate HP reading if your VT tables are close.

[cjperformance]

Originally Posted by KingLT1

The problem with using MAF lb/min to calculate HP is that the MAF maxes @ 86lb/min even though it may have plenty of ceiling in HZ.

I have setup a custom Math's parameter for HP in HPt using the PID 50408 x 50070 / 5252. It gives you fairly accurate HP reading if your VT tables are close.

I have seen as high as 84 lbs/min at the very top end of my charts, mostly an outlier thing... what is the approach when maf is expected to exceed that 86 lbs/min value? Is that just for the torque modeling aspect? If the engine consumes more than 86 lbs/min, will it go lean? Or is it okay, because fueling is based off Hz and not the calculated lbs/min value?

[Joshinator99]

Originally Posted by cjperformance

I have seen as high as 84 lbs/min at the very top end of my charts, mostly an outlier thing... what is the approach when maf is expected to exceed that 86 lbs/min value? Is that just for the torque modeling aspect? If the engine consumes more than 86 lbs/min, will it go lean? Or is it okay, because fueling is based off Hz and not the calculated lbs/min value?

It won't go lean thankfully, its just an HP Tuners readout issue. You still tune the MAF at WOT the same way.

[KingLT1]

Originally Posted by cjperformance

I have seen as high as 84 lbs/min at the very top end of my charts, mostly an outlier thing... what is the approach when maf is expected to exceed that 86 lbs/min value? Is that just for the torque modeling aspect? If the engine consumes more than 86 lbs/min, will it go lean? Or is it okay, because fueling is based off Hz and not the calculated lbs/min value?

It's just a readout limit in Hpt as Josh mentioned. The ECM uses frequency for fueling. So as long as your HZ limit is adjusted for a higher ceiling in the maf airflow table its fine.

[s346k]

my car shows 45-48 lb/min. m6, made 441, trapped 125 on drag wheels @ 3900 lb raceweight & 900' da.

i think it would take considerably more lb/min in a blower car to equal the performance.

[cjperformance]

Originally Posted by s346k

my car shows 45-48 lb/min. m6, made 441, trapped 125 on drag wheels @ 3900 lb raceweight & 900' da.

i think it would take considerably more lb/min in a blower car to equal the performance.

441 wheel should be around 490 crank, so that correlates well with 48 lbs/min.

[wnta1ss]

Originally Posted by cjperformance

Im just theoretically speaking here. I know its a just an approximation.

Reputable tuners have said 1 lb/min airflow = 10 hp. That is assuming your tune is perfect with spark, afr, etc... i gravitate to 1 lb/min = 9 hp because im a pessimist.

Regardless of the exact ratio, if you have a forced induction system consuming, for example, a max of 60 lbs/min and an NA engine consuming the same max 60 lbs/min. Would they be making the same peak power at the flywheel?

Do you have to account for the supercharger drag? Or does it somehow just magically work out in the airflow numbers?

SC is using some of the air to burn extra fuel in order to turn the supercharger (extra drag to overcome). Therefore you must account for the supercharger IMO, meaning that your theoretical 60 lb/min of airflow is likely giving more hp at the flywheel or rear wheels in the NA application than in the SC application.

[s346k]

Originally Posted by cjperformance

441 wheel should be around 490 crank, so that correlates well with 48 lbs/min.

i really don't understand the lb/min reading. it has basically read the same thing despite the car picking up power and mph. i never put much stock in it tbh. i also wonder how weather would affect the reading.

[cjperformance]

Originally Posted by s346k

i really don't understand the lb/min reading. it has basically read the same thing despite the car picking up power and mph. i never put much stock in it tbh. i also wonder how weather would affect the reading.

In 90 degree weather i see a max of 76 to 78 lbs/min, in 60 degrees, i see 78 to 81 lbs/min. Cooler air is more dense, and given the same displacement, pressure, rpm, etc a greater mass of air will enter the engine. This is prob compounded with a sc because i will also see higher boost pressure in the manifold, so higher pressure is even more air mass.

In reality there is a maximum amout of hp you can make given a certain mass of air. To make more hp you have to add more fuel, and to burn that effectively you have to have more air. So in a loose way, the lbs/min defines the MAX power you can make. If your power is increasing but airflow lbs/min stays the same... it means you are more effectively using the air and fuel you always had.

This doesnt account for cams and other things that can drastically change airflow characteristics... its just an approximation. At some point i want to make back to back runs under the same conditions with one run at 5 to 10 degrees less spark timing to see if the airflow is more about cam/displacement/rpm/etc (the physical air pump) vs actual power. Is suspect its more about the former... meaning just an indication how much air you can consume. Making the power is more about using it effectively.

[ZL14ever]

Originally Posted by KingLT1

The problem with using MAF lb/min to calculate HP is that the MAF maxes @ 86lb/min even though it may have plenty of ceiling in HZ.

The PID "Dynamic Airflow" can show 120+ lb/min. Is this a calculated or measured reading?

[Joshinator99]

Originally Posted by ZL14ever

The PID "Dynamic Airflow" can show 120+ lb/min. Is this a calculated or measured reading?

That’s the one I’ve been using for the past couple of years. I think it’s MAF blended with VVE airflow, but since VVE is mostly ignored at higher RPM, I’m thinking it’s mostly MAF at that point. I was 113 lb/min on my 927 WHP dyno pull so I think it’s reasonably accurate.