AFR - ideal 90 degrees IC outlet vs. 140 at the track - what's the diff. in density?

[E-man930]

ahhh no targets!
I just posted the book for those that did not fully understand how CIS and its evolutions works... My initial coments I'm going to blame on my tired cranky moody self studying GA securities laws. Pat, you are correct in your previous statings. I realized than rather than posting snide remarks beating up on other members who may not have the same knowledge base as me is childish, so I changed my post. Unfortunately it was too late.

[NathanUK]

Are you guys saying that when the turbo compresses air that no more air is drawn into the engine through the barn door?

I would have thought that if the engine received 30cfm of boosted air it would still have 30cfm of air being sucked through the barn door but it would be travelling at twice the speed compared to after the turbo if it had to go through an aperture of the same diameter as the door?

[Craig 930 RS]

Geez, this thing is getting out of hand.

This topic is simply a question of at "what rate does the air density decrease as temperature rises"

I received an answer of 6-8 percent less density - aka, the mixture becomes 6%-8% richer. Thanks for that -

Barn door discussions and "If little Tommy is traveling to Pawtucket on a train at 50 mph, and his friend Jane is travleing to Pawtucket at twice the speed in an airplane, what time will they meet for a quickie in Rhode Island by the CIS meter which is 1/3 the distantance from Pawtucket?"....yeesh

[beepbeep]

Originally Posted by Craig 930 RS

Geez, this thing is getting out of hand.


I received an answer of 6-8 percent less density - aka, the mixture becomes 6%-8% richer. Thanks for that -

Barn door discussions and "If little Tommy is traveling to Pawtucket on a train at 50 mph, and his friend Jane is travleing to Pawtucket at twice the speed in an airplane, what time will they meet for a quickie in Rhode Island by the CIS meter which is 1/3 the distantance from Pawtucket?"....yeesh

...and you are still wrong. Unless air magically leaks or dissapears between CIS and engine, AFR won't change a squat unless you "pegged" the CIS with barn-door fully depressed all the time.

[Garen]

How about this:

When you set your fuel mixture, you base it on what comes out of the IC, and into the engine. X amount of air, sucked in through the barn door, pressurized, cooled to 90 degrees, and ready to be consumed by the engine has a density of Y. So, you tune the mixture to get your desired AF ratio based on air of that pressure, temp, & density.

Now you're at the track, and your actual intake temp is at 140. The density has changed. Has the CIS been fine-tuned for 140 degree intake temperatures? That is Craig's question as I understand it.

I don't think it's about air dissapearing between the barn door and the throttle body, it's about what parameters you set your mixture to. Correct me if I'm wrong, but you don't set the mixture to the air just before the turbo, do you?

So, Craig, would you feel comfortable leaning out the car based on the density difference? Kinduva risky game to play...

[Craig 930 RS]

Door would be 'pegged', beep - we are talking full throttle AFRs.

Garen has understood the question, yet let's clarify the function:
Thus DonE has set his fuel on his EFI to run 6-8% leaner at the higher post-intercooler engine inlet temperatures due to the CHANGE - the decreased density of the incoming air.

Now keep in mind that EFI CAN adjust FOR that difference........I speak of the temperature difference *by itself* here.....90 degrees vs 140.

Thus the original question:
Air density as a function of temperature? (and also humidity) -

[DonE]

Originally Posted by Garen

.....


So, Craig, would you feel comfortable leaning out the car based on the density difference? Kinduva risky game to play...

I won't speak for Craig, but I did exactly that during the summer months. Otherwise, it was pig rich and didn't run as well (and I might add, evidenced by an AFR gauge/wideband O2). Did I need to do it? Nope, but I had the capability and this car is all about performance anyway.

[Garen]

I guess as long as it's not done to excess, where a cold day at the track sends the AFR's too lean, then all is well. Having the proper tools, as you have mentioned, is a definite plus!

Just curious, did you ever run some comparisons, be it dyno tests, acceleration measures, etc, to see the difference between the summer/winter months? It would be cool to know.

[DonE]

AFR's were the only thing I monitored. To keep the the motor from leaning out to 13.0:1 in the winter, I had to take away .4 bar pressure on warm and enrichment pressure.