let see.... less oxygen...more fuel.... air fuel ratio.... oxygen fits into the air portion of the ratio so that leaves fuel. to get the proper afr when you have less air one would need to adjust the ??? (i'll give you a hint: it rhymes with mule)

now that's funny.....

the car cannot and does not maintain a stoichiometric afr at all times. sure wish it did though, if it did it would make spin's question moot.

 

Are you implying that a tuned car at altitude isnt making power becuase the tune is off? Are you saying you can tune back the power lost from less dense air when there isnt anything for the same amount of fuel to mix with?

 

Are you suggesting that guys at higher altitude run leaner than stoic? Like 16:1 or 17:1?

The car adjusts itself all the time in closed loop so there isnt any adjustment. A cylinder cant fill more than atm pressure allows.

 

wait, hold on... to many variables that equal in both of those statements.

i'm not saying that a tuned car at altitude isn't making power because it aint' tuned. i'm saying it needs to be tuned for the altitude.

no, not saying you can tune in more air when the source contains less.

i am simply saying, 'look into the previous methods folks used to make power at higher elevations'. determine why and how they did it then adapt it to the 'new' method.

check out 'pikes peak' tuning methods.

 

yes, getting close, however, don't know i'd go that far.

yes, the car adjusts itself (to a degree) all the time but as you have seen, it can't make perfect adjustments at elevation.

it makes adjustments so it runs within it's given set of parameters. (ie. need more air we're running rich, need more fuel we're running lean, retard the timing we're getting knock, move it forward we aren't getting any knock, etc. etc.)

as altitude (oxygen content) changes the perfect ratio also changes. remove oxygen and you need to remove fuel.

 

While I agree with everything you said above and you know one of my pet peeves is somebody attempting to convert RWHP to FWHP, you missed the point of my post.

HP losses due to altitude is calculated from FWHP to be exact although I also showed it's pretty close if you use RWHP. No big deal...you know me, I was just playing with numbers.

 

And that's exactly what the computer does. As altitude increases, air density decreases which means it has less heat capacity (BTUs) due to fewer molecules or less mass. In closed loop operation, the mass air flow sensor "sees" less mass at the higher altitudes because the air doesn't have the heat capacity to remove as much heat from the heated wire. As such, it goes to a different point on the fuel tables to provide less fuel to get close to Lambda=1 (14.7 A/F ratio) and then the O2 sensors adjust the fuel trims to get Lambda=1. In open loop/full throttle operation, it's a speed/density system where the computer senses the altitude/barometric pressure and goes to that part of the fuel table. I think you've gotten loss of power at altitude confused with the ECM's ability to compensate for altitude...both are a fact of life.

PS The perfect ratio (Lambda=1) never changes...it's always 14.7:1. (Google "lambda air fuel ratio" for some interesting reading.)

 

My solution is to never bring my car to my Colorado home(8600ft.) so I don't have to explain why I ran so slow at the local track! lol

 

Actually, the EPA requires all cars sold in the US to be capable of running on 87 octane. As far as Corvettes are concerned, there are a lot of times when a smart user in NJ fills up with 87 octane. There are times and places where I'd even fill up with 85 octane.

 

Like when it is frigg'n freeeeeezing outside?

 

Nor can it make perfect adjustments at sea level. The adjustments it makes at altitude are the same and have the same effect as the ones it makes at sea level.


WRONG! The ideal ratio is ALWAYS 14.7:1, regardless of what elevation your at.

Right.

 

Very interesting read guys, Powerlab,Tom400 CFI, glass slipper, on the subject of elevation.

 

I am sorry, you have demonstrated that you lack even the most basic foundation to understand what you are arguing about. Please re-read my posts, and if you actually care to learn about what you discuss, instead of just repeating your misconceptions, I strongly suggest that you buy yourself a copy of:



Its $20 on Amazon. I'll paypal you the money if you don't want to spend the 20 bucks just for the sake of you and I hopefully having an edcated conversation on this subject in the near future. PM me your paypal info if you want to take me up on that offer.

I don't claim to know everything, but one thing I always make sure of is that I at least have some educational foundation for the things I discuss here Have a good day.

--Sam Barros.

 

Since you will never know for sure what a car ismaking FWHP you cant use the number in a calculation unless the engine was on an engine dyno. You yourself said you never agree on what a motor makes in the conversion I fail to see the point of saying the formula is meant for flywheel. Since the rerlationship between the flywheel HP and rwhp is proportional until you do drive-line mods such as gears and alum flywheel, the results are proporttional losses to what you would have FW. The error in the conversion from rw to fw is going to be even less accurate.

I fully understood your post but it isnt an option to try to convert rw to fw. The calculation is off either way. Showing the loss is as big as it is wasnt my point either. The thread was made to find fixes and ask residents there what they did mod wise to have a fast car.

It appears that boosted cars are the way to go there since the boost level can be adjusted with a pulley and the power level is the limit in high elevations.

 

OK, you are saying yes that you would tune the car to run leaner than 14.7 in stoic.

Now how much leaner than 13:1 at WOT?

These fixes you say would give you back some of the losses experienced at higher altitudes? You think running a stroker like RJ's at leaner than 13:1 is a fix and safe?

I think most people already see the truth on the first statement above but I need to hear more. Please elaborate further. Any timing changes? What amount of the lost power do you think these things would get you back if a 403 had 510rwhp and lost 75 to the altitude?

 

try, high altitude octane gasoline

what's the fix for low octane?

i'd have to see, touch, and feel before i could really say.

 

I did a search for high altitude octane gasoline and didnt find anything. Please explain what it is.

The fix for low octane is torco. If you put torco in your tank and drive through Co with HPtuners and a new tune you will still lose the same amount of power. Aintqik did exactly that when he moved there.

Why do you have to see and touch? I was under the impression that you did this before or saw it done by someone and that is what you based your answer on...ie factual info. Is there anyone running 500hp and say 14:1 or 15:1 at WOT?

 

Using your 74.88 HP loss from your equation will result in a new HP level of 405.12 RWHP (not 435.12) if you adhere to your methodology.

Actually, you don't understand what I'm saying. Your methodology to determine HP loss at altitude is incorrect...you can't use RWHP period.

Also, there is no proportional relationship between RWHP and FWHP at anytime as the majority of losses are constants. A proportional relationship means one is a percentage of another.

As an example, a C6 M6 at 480 RWHP has about a 60 HP loss to the drivetrain giving 540 FWHP. While 60 and 540 are not accurate numbers, they are close enough as an educated guess +/-10. Using 540 FWHP, we have 5200*.03*540/1000=84 giving us 456 FWHP. Now subtract the 60 HP loss to the drivetrain and you have 396 RWHP compared to your 405.12 RWHP. As the elevation goes up, the error using RWHP goes up. An educated guess at FWHP will result in significantly less error for HP loss due to altitude than using RWHP. Since you took your new RWHP number out to the one hundreths position, that means any number in the one tenths position is exact which we know isn't true. Sorry, it's just the engineer in me coming out...like I said, no big deal as the error is small in the overall scheme of things. I wish I hadn't said anything now...it was really meant more in fun. Actually, with Zig here, it's really funny...I feel like I'm watching the movie "Dumb and Dumber". I'm playing Jim Carey's character, he's the smart one isn't he???

 

At higher altitudes the gasoline available has less octane because less is necessary. Premium is 91 here, and works just like your sea level 93.

As for the PCM tuning for less air at altitude, it also does very well. I had my heads/cam C5 dyno'd in Los Angeles, it made 418 SAE rwhp with an A/F of 12.8. I drove it to Albuquerque and dyno'd it at an altitude of 5,300 feet and it made 417 SAE rwhp with an A/F of 12.8. The actual uncorrected rwhp was only 345, but that's the effect of low density air.

There is no way you can keep a carburated car running as well as our computer controlled cars do over varying conditions.

 

ok.

i was making reference to what happens to octane at altitude.

i was having fun, you know, one can tune his own car best. what's the first thing you do when you tune a car? you take it out and romp on it, i was having fun with getting seat time.

my apologies if i implied i have performed the required adjustments for this exact configuration.

be back momentarily....