Automobiles Forum banner
1 - 16 of 16 Posts

·
Registered
Joined
·
186 Posts
Discussion Starter · #1 ·
Ever since i moved from seattle to utah my car seems like its running worse everyday. It bogs and dies at low rpm and just doesnt feel like it has full power. im going to do some dyno tuning but just wondered if you people had any ideas or suggestions.

FYI it was tuned at 034 in california (AWD) they came up with 212hp and 236tq. I dynoed it last week in Orem utah which is about 4800ft and it did (RWD) 200hp and 218tq.

Thanks...
 

·
Registered
Joined
·
1,990 Posts
I was wondering the same thing myself. My car felt so sluggish at higher elevations and I was always wondering if there was something that could be done to lessen the effects of high elevation. I hope someone can offer some info on this.
 

·
Registered
Joined
·
75 Posts
40v4kq said:
I was wondering the same thing myself. My car felt so sluggish at higher elevations and I was always wondering if there was something that could be done to lessen the effects of high elevation. I hope someone can offer some info on this.
Turbo...?

Less air to breathe means less fuel to burn, means less powers.

Simples.
Take your average airliner for example, say your engine make 60k lbs of thrust at sea level, at cruise 38000ft, the engines will be making roughly a third of their sea level thrust, but at the same time burning less fuel, and due to the less dense air there is less air resistance.

There's no way round it, other than a turbo, which is why they were used on piston engined props in the first place.

Sent from my HTC One X+ using Tapatalk 2
 

·
Registered
Joined
·
8,147 Posts
40v4kq said:
I was wondering the same thing myself. My car felt so sluggish at higher elevations and I was always wondering if there was something that could be done to lessen the effects of high elevation. I hope someone can offer some info on this.
lol, that is what the turbo was originally designed for. Ever hike a tall mountain? noticeably less oxygen at the top.
 

·
Registered
Joined
·
2,486 Posts
Do you have a wideband O2 sensor with a readout on your car? If so, how are the AFRs compared to what you used to see at lower altitude?

Actually, if the dyno numbers are not corrected for altitude, you're not doing badly. Air density at 5000 feet (the table I found on the 'net goes in increments of 500) is about 85% of that at sea level. So in theory, at that altitude you should get 85% of the horsepower and torque measured at sea level, or 180 HP and 200 tq.
 

·
Registered
Joined
·
5,698 Posts
Yup, Just as they said above, altitude robs power, less air, less power.

For example, I organized a Dyno Day for the audi crew here in Utah a while back. We had 3 v8 RS4s dyno. one stock, one with a fresh carbon clean and open exhaust, and one with open exhaust fresh carbon clean and deflapped and something mods. Stock one was like 278ish awhp, the clean one was 290ish and the highly moded one like 312. This is a "420Hp" car according to Audi.
 

·
Registered
Joined
·
1,990 Posts
No, my car isn't turbo. NA 4.2 V8, but it will be getting turbos now that it needs a new front end. Im running VEMS so yes I do have a WB readout. The AF looked similar to what it normally reads but not that I was looking at it much while driving around with a pack of audis 100 miles from home. I've heard that VEMS self recalculates for altitude everytime its turned on, so that may explain the similar AF readings.

What I was wondering was if there was something that could be done to lessen the effects of altitude as I already stated (besides boost) i.e. run just a tad bit more timing, run a little leaner, etc. ??? Sounds like its just something you have to suck it up and deal with it ;)

Jim, every time I drove back from Reno/Tahoe it felt like cylinders were added to my engine for every 1k feet I dropped, went from a four banger to V8 by the time I got home.
 

·
Registered
Joined
·
8,147 Posts
40v4kq said:
. Im running VEMS so yes I do have a WB readout. The AF looked similar to what it normally reads
AFR should be the same as normal, air is less dense, the map sensor in vems detects this and give you less fuel at the same ratio that it was when you had more air available.
 

·
Registered
Joined
·
3,250 Posts
IIRC, there's a baro-compensation table in 034. It might need to be adjusted as it probably just has some default values in there.
The IIc has two pressure sensors, one for engine and one for barometric.
 

·
Registered
Joined
·
686 Posts
From the MTM dealer in Denver....interesting read... http://champagne-motors.com/tips/

Audi Performance Computer Chips

A lot of our customers ask about Computer Chip tuning their turbo Audi.

Here is a brief overview of tuning:

Computer chips will make your engine run more smooth, with more power, and better fuel economy. Many tuners boast that they can give you lots of horsepower and torque with their computer chips. I would tend to agree… maybe at sea level, but think about this…

We live 5,280 feet above sea level! Have you noticed that you may have a hard time breathing here as compared to sea level? What about driving over some of the 12,000 feet passes. Hmmm, what about your Audi's breathing?

Most tuners only think about lower elevations and therefore, never understand what high altitude does to your turbo if you use the wrong chip. With more boost pressure at sea level and the thick air the turbo(s) spin up properly. At the high altitude the turbo(s) has to turn faster because of the thiner air to deliver more boost; therefore with the sea level chips you get serious over-boost and a broken turbo.

Many turbo's at this altitude fall apart because of the boost pressure that the lower elevation computer chips deliver. The Audi computer will not adjust unless the MTM chip tells it to. All Audi computer chip tuners live at lower elevations and have no idea or care what high altitude does to your turbo. Our Computer Chip market is very small. MTM is the only computer chip tuner that has tuned at this altitude for your turbo Audi's. Their audience is worldwide. If you decide to purchase one of the other computer chips that are available, make sure you ask if their computer chip is high altitude compatable. Then you can make your own decision..
 

·
Premium Member
Joined
·
7,644 Posts
Leave the altitude tables alone unless you are using Tps vs rpm mapping.

Think about it, speed density systems use the map sensor and Rpms of the motor to estimate how much fuel you need. The MAP sensor is already compensating. The only thing that really changes is turbo efficiency, like they tried to state above. So you might get less boost, and more heat.
 
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top