AE_Racer

iTrader: (1)

My brother lives out in Colorado Springs, and races at Pueblo...The altitude out there really kills the cars...

rotary>piston

altitude does make a huge difference, most of you guys don't understand that. Yes, I suck at launching, but that's only part of it.
It's actually 2.5-3.0 psi lower in pressure up here. That means that bigretardhead may be boosting 8 psi, but it's only equivalent to 5 psi at sea level. So all of his work has given him only stock power at sea level.
If I were making a perfect 160 hp at sea level, then at this altitude I would only make between 128 and 136, and that's crank hp!

Damn, I really want to take a road trip to sea level now .

RarestRX

Yo,


Damn dude, you're getting me all stoked on my 15.7. *grin*

That thin air just /kills/ you. Thanks for sharin'!

You got pics of your GTUs?

Kevin
1989 GTUs "White, Red or Black?"

Piranha

No, a turbo brings the pressure back up to the actual pressure. 8 psi up there is 8 psi down at sea level. The turbo doesn't sense a difference, once the pressure can overcome the wastegate spring (which doesn't give a **** about your altitude) it will slow the turbo down.


Now, the turbos will be less efficient because they are starting out with less pressure. But 8 psi doesn't equal 5 psi....

Of course, everyone will have less power.

Turbos are also used on airplanes to bring air pressure back up.

Fingers

I'm afraid that YOU are the one that doesnt understand altitude. When a turbo boosts a certain psi, that IS the pressure, no matter what altitude.

The only thing that changes is the density of the air, and that's what causes a rich circumstance.

Piranha

Yeah, that's what I was trying to say. I suck.

chaz805

one word.......ALTITUDE!!!

West TX RX-7

Your time sounds about right for your 60ft and altitude. You go to sea level and you'll hit high 14's, you learn to launch good and you'll get to low 14's at sea level or high 14's/low 15's at 6k.

I think people don't realise how fast a low 14 second pass really is. Too much TV talked about 12's and 11's, well hold on to your *** if your runnin 11's or 12's cause that **** is fast. Low 14's on the street is enought to beat 90% of the racers out there. only like 3% of the guys are breaking into the 12's and less into the 11's and 10's.

A guy in my town has a wednesday built 2002 GT mustang with no cats, full exhaust, K&N, performance chip and he's stinky fast on the street, he only runs 14.1's at the 1/4.

gsracer

99+ GT's run low 14's and occasional high 13's stock
lt1's run high 13's- low 14's
ls1's run from low - high 13's

low 14's is quick, but nowhere near fast.

Get that 60' down. Anything over 2.5 is hard to believe if you are actually trying to launch and not doing a smoky burnout down past the 1/8 mile

Bigretardhead

I think I was actually letting the clutch out too slow, especially the first time. I couldn't hear my car, or my tires, or anything because that damn cougar was soo loud. the 2nd time was a little better - I think I heard them make little chirp, but it could have been the celica next to me, that had a 2.78 60' time I'll probably go again next high school drags, and I'm sure I'll be MUCH better by then.

West TX RX-7

The air is less dense at altitude also. Same volume of air = less Oxygen at altitude.

rotary>piston

about the boost:
the boost sensor measures the difference between the pressure inside the tube and the atmospheric pressure. It is not an absolute sensor, so it's not sea level 8 psi. Why do you think the stock sensor has that little opening thing (like the atmospheric presure sensor). The VDO guage that bigretardhead has also just measures the difference between the pressure in the intake and the outside pressure.
I may be wrong, but I really think that stuff makes sense.

And RarestRX, it's white.

Piranha

The boost sensor doesn't control boost, the wastegate does. Anyway, just because you see a hole in something doesn't mean it is meant for what you assume it to be

rotary>piston

but these sensors just meaure the difference between the pipe pressure and the outside pressure. 8psi boost is 8 extra psi over the ambient pressure, not sea level pressure plus 8 psi.
The only way it would be independant of outside psi is the wastegate, because the spring rate on it doesn't change between altitudes. So if it opens at say 6 psi at sea level (I don't remember what the real psi is), then it requires a total of 20.7 psi (14.7 psi is sea level) to open. That means you need make 8-9 psi up here to open the wastegate.

Detriuch

iTrader: (1)

wtf is wrong??? im glad i dotn liek in CO dam altitude sucks

Fingers

Your logic is incorrect. Yes, you are right, pressure is pressure... but the unit of measurement doesnt change no matter if you're here or up in the atmosphere. 8PSI of air will still be 8PSI, regardless of altitude. It's the density of the air that's different. It's like sucking in hot air instead of cold air.

rotary>piston

yes, 8 psi over 11.7 psi, instead of over 14.7 psi. In the end less pressure is reaching the engine. At sea level at 8 psi you get a total of 22.7 psi in the engine (assuming there is no resistance going through the manifolds). Up here you get a total of 19.7 in the engine. The total pressure going into the engine at 8 psi up here is the same as 5 psi at sea level.

Piranha

dude, you're wrong, have you ever had physics? The turbo brings the pressure UP TO the specified (wastegate) pressure. The sensors have nothing to do with turbo pressure. The thing is, you're starting less dense air and raising it up to spec pressure. PRESSURE is the same, but the air is warmer, and hence, less power. 8 psi is 8 psi is 8psi. What you should say is that 8 psi up there is equivlant to 5 psi at sea level, not the same...

Fingers

NOOOOOOOOOOOOO
That is INCORRECT. You're just repeating yourself.

Pressure is pressure no matter where it starts. Lets put it this way... say your car is boosting somewhat... lets say 1psi... Then you mash the throttle and hit 8psi.

Now to compare, say you're not boosting at all... like 20 inches/mercury... then you hit the throttle and hit 8 psi.

Either way, you still hit 8 psi. It doesn't matter what the atmospheric pressure is, or what pressure you begin building boost at. What matters is the final result, being 8 psi. Boost sensor senses the actual pressure @ vacuum line... not the atmospheric pressure. That's for the ECU to handle and compensate for.

Hope that explains a little better.

rotary>piston

it's all relative though. The word boost means the pressure increase over atmospheric pressure. 8 psi is 8 psi more than you would normally get.
If all the boost sensor did was measure absolute pressure then it would always read "14.7 psi" until you boosted. It doesn't though, meaning that it gets its reading from the difference in pressure between the atmosphere and the intake.

Piranha

no, it wouldn't, because YOUR pressure is under 14.7. That is standard at sea level.

You have to remember, sea level equals 1 bar in itself, you're either starting out below it (like you or me, but you to a much greater extent) or you're AT it. Then you go up from there when boosting.

rotary>piston

no, you don't.

Seriously, that makes no sense why it would go to sea level pressure, then boost. What if you could go 2 miles down (below sea level), would the guage always read 5 psi boost even when idling? No

Bigretardhead

I think you guys are somewhat saying the same thing. just in different ways.

yes, the amount of BOOST the turbo is producing is still the same, but the the total amount of air going into the engine is less at high altitude than at sea level.
does that sound right?

Piranha

Ok, go take a physics course, then come back an argue. It isn't about making SENSE, it's about how things work.

rotary>piston

no, I think you're just wrong