parish8

iTrader: (6)

http://www.smokemup.com/auto_math/turbo_size.php

playing around with their calculator and the Volumetric Efficiency makes a BIG diference on the output. i guess this would be for the motor without any boost?

looking at a heads and cam 408 iron motor and dont know what to enter for the VE, any sugestions?

also, on that page the air temp input doesn't make any change in the chart, i wonder if that is a bug in his program? anyone know? it should effect the numbers i would think.

XLR8NSS

iTrader: (4)

I don't agree with the output of that calculator ever since it got changed. If you put in 100% for compressor eff. and 150% for intercooler eff. it's alot closer to real setups. I know that doesn't sound right but, it works out pretty good compared to real motors.

The simpler "Air flow" calc that included boost was VERY accurate. I wish he would put that calc back up.

For VE on a 9:1 heads/cam/high flow exhaust/great setup use around 90% as a good guess. For 8.5:1 drop the VE a few percent.

RunNE1

iTrader: (1)

I think C. Bell of "Maximum Boost" lists V-8's at around 85% VE.

smokemup

iTrader: (6)

XLR8NSS... I posted this just for you! Please note this calculation assumes ideal boost pressure (which is not possible). http://www.smokemup.com/auto_math/airflow2.php

Next time drop me a line if your looking for something. I only found this thread going over my server logs.

Yes the volumetric efficiency plays a big part in how much air the motor consumes and is effected by several factors. I'm unsure of exact numbers for the ls1 but 85% is a good starting point.

The air temp is not taken into account in computing the air density. It is used for the input temps, output temps, intercooler input and output numbers. I left it this way because I assume the turbo maps would be corrected to standard air density.

XLR8NSS

iTrader: (4)

John - Thank you. When you say ideal boost pressure, what do you mean by that? It may not be possible but, that calculator is the most accurate one I've ever seen for blown setups.

Thank you....Thank you....Thank you.

John

parish8

iTrader: (6)

i like that one better!!


Engine Displacement 408
(Cubic Inches)


Engine Type
4 Stroke 2 Stroke Rotary

Volumetric Efficiency (%) 85


Engine Speed (RPM) 6000


Number of Cylinders 8


Boost (psi) 14


Air Temp (° F) 70


Air Fuel Ratio 12.8



Total airflow requirements:
1175.5 cfm
88.31 pounds of air.
6 pounds of fuel

Fuel Supply requirements:
1 gallons per minute for 14.7 A/F ratio.
68.99 gallons per hour for 12.8 A/F ratio.
261.13 liters per hour for 12.8 A/F ratio.


Engine Displacement 408
(Cubic Inches)


Engine Type
4 Stroke 2 Stroke Rotary

Volumetric Efficiency (%) 85


Engine Speed (RPM) 6000


Number of Cylinders 8


Boost (psi) 28


Air Temp (° F) 70


Air Fuel Ratio 12.8



Total airflow requirements:
1748.91 cfm
131.39 pounds of air.
8.92 pounds of fuel

Fuel Supply requirements:
1.49 gallons per minute for 14.7 A/F ratio.
102.65 gallons per hour for 12.8 A/F ratio.
388.53 liters per hour for 12.8 A/F ratio.

smokemup

iTrader: (6)

Maybe ideal boost pressure was not the best choice of words. That calculation simply uses airflow multiplied by the pressure ratio. (if your running 14.7 psi of boost the multiplication factor would be 2, 7.35 psi would be 1.5 etc etc).

By ideal boost I meant perfect compression with no heat added from the compressor (which is not possible).

XLR8NSS

iTrader: (4)

Ok, I see what you're saying. The thing is that if you know what your manifold air temps and boost pressure are you can enter those and get VERY accurate numbers. Then it really doesn't matter what compressor is being used or how much heat it adds.

I still think that calculator does a better job than the new one. Thank you for putting it back up.

smokemup

iTrader: (6)

It really does matter how much heat the compressor adds because that affects the air density (lbs of air).

But if you want to go by that one, have at it.

XLR8NSS

iTrader: (4)

Why does it matter if you take it into account when filling in the "Air temp" field?

If the compressor adds 150 degrees to the 80 degree ambient air and there is no form of intercooling then put 230 degrees in the "Air temp" field. Those numbers might be a little extreme but, I'm just using that as an example. If you know the boost pressure at the manifold and the air temp at the manifold I don't see how that is so inaccurate.

Again, not trying to be argumentative or anything. Just, I've had better estimates from the old one when using the method I showed in the example above.

smokemup

iTrader: (6)

What are your better estimates based on?