F1technical.net

trinidefender wrote:

irsq4 wrote:

gruntguru wrote:No big deal.

If the VE is 110% thats 10% extra air mass. If the MAT is 27 degrees above ambient thats 10% less air mass. Combine the two - no change.

(This is VE of the piston engine i.e. charge air not atmospheric)

How did you get 10% less, I got 17% less for 27 deg above ambient (22)?

Did you use 22 as ambient?ambient air temp is considered 15 degrees Celsius and 29.92 in.Hg/1013 MPa by ISA conditions.

Heh, kinda crazy, using an ambient air temperature that's above standard room temperature!

I probably shouldn't have used the word ambient. All I was trying to say is, raising the CAT by say 30 deg from 300K to 330K will reduce charge density by 10%.

beelsebob wrote:

trinidefender wrote:
Did you use 22 as ambient?ambient air temp is considered 15 degrees Celsius and 29.92 in.Hg/1013 MPa by ISA conditions.

Heh, kinda crazy, using an ambient air temperature that's above standard room temperature!

That's not really crazy: how many races are run at 15°C? I haven't seen many over the past few years....

trinidefender wrote:

irsq4 wrote:

gruntguru wrote:No big deal.

If the VE is 110% thats 10% extra air mass. If the MAT is 27 degrees above ambient thats 10% less air mass. Combine the two - no change.

(This is VE of the piston engine i.e. charge air not atmospheric)

How did you get 10% less, I got 17% less for 27 deg above ambient (22)?

Did you use 22 as ambient?ambient air temp is considered 15 degrees Celsius and 29.92 in.Hg/1013 MPa by ISA conditions.

Yes 22, but it`s not 17% it`s cca 8% less air mass for 22 - > 27 degs. My bad! But forget, post above explains 10%

You all are willing to accept inaccuracies of over 10% but want to pin down on something as sensitive to making power as A:F?

ringo wrote:You all are willing to accept inaccuracies of over 10% but want to pin down on something as sensitive to making power as A:F?

No, it was just some math checks, forget. Of course A:F has influence, g/kW/h, rpm, temp, displacement, all has influence on pressure and air consumption.

ringo wrote:You all are willing to accept inaccuracies of over 10% but want to pin down on something as sensitive to making power as A:F?

Because in the current fuel limited formula A:F ratio has a much bigger impact than before. Especially with direct injection where engine builders can possibly include things like running the engines quite lean and controlling the combustion, stratified charge.

Ringo you seem to be forgetting that Renault themselves say that they ran 3.5 bar

trinidefender wrote:

ringo wrote:You all are willing to accept inaccuracies of over 10% but want to pin down on something as sensitive to making power as A:F?

Because in the current fuel limited formula A:F ratio has a much bigger impact than before. Especially with direct injection where engine builders can possibly include things like running the engines quite lean and controlling the combustion, stratified charge.

Ringo you seem to be forgetting that Renault themselves say that they ran 3.5 bar

3.5 bar - absolute or boost?

irsq4 wrote:

trinidefender wrote:

ringo wrote:You all are willing to accept inaccuracies of over 10% but want to pin down on something as sensitive to making power as A:F?

Because in the current fuel limited formula A:F ratio has a much bigger impact than before. Especially with direct injection where engine builders can possibly include things like running the engines quite lean and controlling the combustion, stratified charge.

Ringo you seem to be forgetting that Renault themselves say that they ran 3.5 bar

3.5 bar - absolute or boost?

According to this: http://www.renaultsport.com/IMG/pdf/rsf ... final2.pdf it is 3.5 bar absolute so 2.5 bar boost

none of you seem to allow for humidity. Would that not also affect it?

Most engine testing standards do not correct for humidity. This is probably because the standard test conditions are relatively low temperatures around 15 - 20*C and the air will not hold a significant amount of moisture at these temperatures. For example at 20*C the oxygen content in a given volume of air only varies by 2% between 0 - 100% relative humidity. On the other hand at 40*C the difference is about 8%. The boost of current F1 engines would need to be adjusted accordingly to maintain the correct oxygen/fuel ratio.

ringo wrote:You all are willing to accept inaccuracies of over 10% but want to pin down on something as sensitive to making power as A:F?

A +-10% agreement on what AFR is being used in the current engines would be a huge improvement. We have had people arguing for everything from 0.8 to 2.0 ie 1.4 +-43%.

Thanks for clearing that up for me.

gruntguru wrote:

ringo wrote:You all are willing to accept inaccuracies of over 10% but want to pin down on something as sensitive to making power as A:F?

A +-10% agreement on what AFR is being used in the current engines would be a huge improvement. We have had people arguing for everything from 0.8 to 2.0 ie 1.4 +-43%.

You are not understanding my statement. I am saying that yes 10% difference in A:F is very important. And this is why you cannot willy nilly accept 10% fudged numbers for other things like air temperatures and charge pressure and temperature.
They all affect A:F used.
So I am basically saying that you can't have your cake and eat it. Either you work with complete accuracy or you don't.
Previously you all were fudging up boost temps and pressure. I am saying that you cannot do that and expect to get any useful result.