Greg1959

Well-known Member
I didn't know what to title my question....anyway....

In 1989,1990 and 1991 I drove around the country. The first 2 times I drove a 1987 Pontiac Firebird and the last time was a 1989 Ford E-150 conversion van w/351 windsor.

While going over the Rockies in CO, WY and MT I experienced a lot of engine miss and loss of power. I found out later that the computer chip was not programmed for high altitude. (Is this true???)

I'm looking at buying a new motorhome. My question is....do newer vehicles have programs to adjust for higher altitudes and air density?
 
'87 Firebird would have been carbureted, I believe. I assume the '89 Econoline would have had rudimentary electronic fuel injection. Both would have had fairly simple ignition controls.

Modern vehicles have much more sophisticated engine control systems. Emissions and fuel economy requirements dictate them In particular, cars today all have either mass airflow or manifold air pressure sensors, which inform the computer about air density. I've driven a variety of late model vehicles over 11K+ mountain passes with no problems. Sure, the engine will be much weaker than at sea level, but it will run just fine.
 
Most of the fuel injected engines will run without missing at higher altitude, as the computer will adjust the mixture accordingly. You will still notice a lack of power though, as there is no way around the lighter air charge short of a turbo or supercharger.
Also, most newer vehicles have more power than those built just a few years back, so the power loss might not be as noticable.
 
back in 75 I took a 71 TR-6 thru Wolf Creek Pass. the higher I got the less power. near the top I had the "pedal to the metal" and nothing was happening. never did stall tho.
 
steve19438- Yup, I had the '89 Ford E-150 pulling a 35 foot camper...I thought I was going to push my foot through the floorboard while going up those mountains! LOL
 
I have never heard of a chip problem at altitude. Any vehicle sold would need to be able to be driven anywhere, the manufacturer would have no control over where it went.

Fuel injection would be self adjusting. The systems goal is to keep the fuel mixture at optimum efficiency regardless of altitude. Problem is, there just isn't as much oxygen to mix with the fuel, so the fuel cuts back, less charge to burn. Combine that with gravity and you get the double whammy!

I've heard carbs need to be jetted leaner for altitude, but never did it, never lived there. I have found them easier to flood when cold if the auto choke was too tight. Seemed to do better with little to no choke.

I've driven some of those Ford vans with the 351. We used to have one at church. It was terribly under powered, got bad mileage. Checked everything, could never get it to run as well as I thought it should. Seemed to be geared too tall.

All I can say about choosing a motor home, drive it first, or read the reviews. If you plan on doing a lot of mountain driving a turbo diesel might be the answer.
 
Steve@Advance- "If you plan on doing a lot of mountain driving a turbo diesel might be the answer."

That's how I'm thinking.
 
I live at over 5000ft,frequently go to nearly 10,000. You are right you need smaller jets,Also you need to advance timing. More advance the higher you go. Todays computerized vehicles self adjust. I think it is the 'oxygen senser' that tells the engine what to do.I drive a '70 F100.It's jetted/tuned for this altitude. I really don't notice a whole lot of performance issues when I go higher than home. However,the few times I drove down to lower elevations(Kansas)It seemed to wake up. got lots more power. ,
 
Hello Greg1959,

Your old drivers were affected as the fuel to air mix were set and non adjustable on the fly. New engines with 02 sensors will fare much better at higher altitute even though SAE HP is for 77*F. 29.31 in. Of Hg @ 500ft above sea level. Not sure if the ASE number still apply, if not they may be even more stringent.
For every 1000 feet of elevation, engine, are derated 3%. Turbocharged engines are derated at 4%,for each 1000 ft above sea level. My references are from my school days, your mileage may vary,
Guido.
 
Hello Steve@Advance,

High altitude jetting is necessary when poor performance is an issue. Briggs and Stratton has been listing jetting changes in their manuals. Main jet is changed to achieve proper engine performance. Because more air is used to feed turbo engines, they are derated 4%, while naturally aspirated engines are derated 3%. That loss of HP is for each 1000 feet above sea level,

Guido.
 
I spent almost 30 years in a Ford dealership. All summer long there would be tourists stopping to complain about loss of power. The teachers at the Ford training center said there would be about a 25% loss of power from sea level to where I was at about 5400 feet. For locals I would advance the timing. For tourists I couldn't do that because they would have serious spark knock problems when they got home. Nowadays the computers can make some adjustments but they can't get all of the power back.
 
Not answer of fuel adjustment. However in pulling 40 foot 3 slide out RV and also 40 foot tandem implement trailer over wolf creek and others just west of Salida CO. some modifications were very good. Best thing I did to 3/4 ton ford with 480 engine was to install a Brownie Lite auxiliary transmission. some are different ratios. My best set up was straight with a 15 per cent reduction and a low of 2 to 1 ratio. Three different ratios. Topping Wolf Creek or other high passes with 2 to 1 gearing speedometer read 60 MPH while actual speed was 30 MPH. Passed many with steam and or oil smoke or just stopped was often. Also downgrade was good while saving hot brakes. The 15 per cent ratio was very good in a head wind. I found both of mine in older junk yards, usually on 1 and one half or 2 ton trucks. They were common in 1950 era. Very easy to replace bearings giving a like new unit. Other reduction or overdrive setups are around, however I would only want one with shifting capabilities between ratios. Stopping to shift is usually necessary. E mail open if you should want more information.
 
Hello Greg1959,,

You are welcome. Have fun traveling, and post some pictures as well. Drive safely......

Guido.
 
Hello Arvin Haslem,

That teacher was wrong! Without going to a lot of number I will try to explained it in a shorter way.
Engine rating is done according SAE ( Society of automotive engineers) specifications. From that point of sea elevation,(500 feet), engines are derated ( Loss of HP), per each 1000 feet higher elevation.
3% is the loss of HP for a naturally aspirated engine, which includes two cycles Diesel. While turbocharged engine suffer a loss of 4% of their rated HP. I have never read the 25% loss in any text books that I haver used in my class room,

Guido.
 
One of the peculiarities that I found when working in Ford dealerships was when folks came in with loss of power complaints at high altitudes. Then, power would return once they "floored" it. The explanation was that the computer adjusts the mixture to the altitude when the engine is started by reading the barometric pressure sensor - which was built into the B/MAP sensor on the firewall. while climbing a steep hill and increasing altitude, the mixture would keep getting richer and richer due to the lack of air volume. Once the driver opens the throttle fully, the system does a soft reset and the computer recalibrates for the current altitude and the engine picks up and starts running properly. Back in the years of 1989, 1990, and 1991, the 351W engines used a B/MAP sensor. Starting somewhere in the early to mid 1990s, they started changing over to MAF (Mass Air Flow) sensors which are more sensitive and more accurate. Loss of power results from less density of the air charge entering the engine.
 
81 I transferred from Lake Charles to Farmington, NM. They wanted me to take a new Chevy crew cab for the shop. Did great all the way to Amarillo, but going on I40 into Albuquerque it was losing a lot of power and burning a lot of gas.

Also notice that people who were passing me on the interstate were like getting all the way on the apron, off the main interstate. Thought it was a little strange, but i had never been in New Mexico so thought it might be normal. Anyway, looked out the rear view mirror , and every time i let off the gas, a 3 foot flame came out the tail pipe LOL. Then, we stopped at a Denny's or something, got out, went inside and maybe 5 minutes later a huge backfire.

Fun trip.
 
I've always believed that power loss in turbo engines didn't follow the same rule of thumb that naturally aspirated engines do. If the turbo is set up to maintain absolute pressure there should be no power loss since you'd be stuffing in the same amount of air. This assumes the turbo could spin fast enough to accomplish this. However, if it maintains relative (or gauge) pressure that is referenced to the atmospheric pressure there will be a loss. Even in this case, though, the percentage of total intake pressure lost will be a lower percentage than with a naturally aspirated engine since the reduction in atmospheric pressure will be a lower percentage of the total. For example, the loss of 2 psi from 14 psi at low elevation to 12 psi higher up is a greater percentage of pressure (and power) lost than if running 10 psi of relative boost giving 24 psi and 22 psi, respectively. I easily could be wrong in my understanding, though.

Makes me think of the first car I owned - a 1986 Buick Skyhawk T-Type with a turbocharged 1.8L engine. (Only years later have I learned how rare that car was - I should have hung on to it!) At my home in southeast Colorado (around 4000 ft) the boost pressure gauge would top out around 12-13 psi but in the mountains it would struggle to get to even 10 psi with a noticable power reduction. At 1500 ft in Kansas it would peg the 15 psi gauge which resulted in audible pinging unless I used high octane fuel. I figured that the little turbocharger simply couldn't spin fast enough to maintain even relative pressure at high altitudes.
 
Hello Brendon-KS,

WELL?......they do. Turbocharged engine loose 1% more power then the naturally aspirated engines. Cummins engine school hand out May 1974, that is where the numbers came from,

Guido.
 

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