high altitude adjustments

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3,329
Location
Bolivia
Its clear that the flow rate of the diesel fuel has to be reduced for the reduced air at 13,000 ft, but does anyone know whether Toyota diesels or other small diesels need to have the fuel inyection timing advanced also?
 
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12,385
Location
Northern CA
I'm pretty sure some late model diesels compensate for atmospheric pressure. I dunno if that has filtered dwon to smaller diesels or not. Some timing advance should help a bit too.
 
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2,364
Location
sebring, florida
what i meant was that the altitude compensators just reduce the maximum fueling. you can accomplish the same thing by not using as much throttle as you normally would at low altitude. the small engines do have compensators, atleast the little 1.6 vw's from the 80's did.
 

widman

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3,329
Location
Bolivia
no, these engines produce a lot of soot at idle. I'm looking for a solution for 6 of them (min) that are frecuently generating over 12% soot in 2000 miles, increasing viscosity to >100 cSt at 100C. My 3.0 Turbo 4Runner compensates pretty well, but the non-turbo engines need some adjusting.
 
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1,801
Location
Saint Paul (ex-San Diego)
Quote:
Its clear that the flow rate of the diesel fuel has to be reduced for the reduced air at 13,000 ft, but does anyone know whether Toyota diesels or other small diesels need to have the fuel inyection timing advanced also?
Don't know about all small diesels, but the VW TDI's engine control module (ECM) has a built-in barometer. Fuel injection doesn't need adjusting, but I am pretty sure the EGR works differently at higher altitudes. And maybe the amount of turbo boost.
 
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267
Location
Idaho
Quote:
no, these engines produce a lot of soot at idle. I'm looking for a solution for 6 of them (min) that are frecuently generating over 12% soot in 2000 miles, increasing viscosity to >100 cSt at 100C. My 3.0 Turbo 4Runner compensates pretty well, but the non-turbo engines need some adjusting.
A normally aspirated diesel expects to draw in the same amount of air on every intake stroke in order to generate enough heat from compression to properly burn the fuel. They are throttled by varying the amount of fuel injected. At high altitudes there isn't as much mass to the intake charge so it simply cannot develop the compression pressures required to get a good burn. Advancing the timing a few degrees would help raise combustion pressures but don't get carried away with it. Higher static compression ratio would be a good thing but probably isn't practical. A turbo is a wonderful gadget at higher altitudes but they don't typically add a lot at idle. Joe
 
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3,845
Widman, find a less restrictive but high quality air filter for the units. Maybe even change the air filters more often. If soot is a serious issue and sounds like it is, order some FP and LC from Odis Beaver 214 929 2704. The combination in a SA toyota diesel should be sufficient to compensate for the Ecuadorian altitude and poor quality fuels. LC was used in KC97 recip engines in the 50's and 60's to fight the same issue.
 
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3,845
Sorry, I meant Bolivia. Quito or La Paz are certainly high enough for any IC engine to struggle to function especially if not SC or TC.
 

widman

Thread starter
Messages
3,329
Location
Bolivia
Actually, the air filter is not too restrictive. The other fight I have with drivers is that they take the 200 psi air hose to the filters. I have samples where we can keep the soot under 1% in 6000 km, which whoud be fine, but most end up between 6% and >12%. I've got some samples with >600 cSt at 100C from soot. Some suffer from being abused for 200,000 km with high dirt and soot, causing increased wear of the cams, which of course reduces the amount the valves are open and delays their opening. Because of the abuse they were all rebuild at around 100,000 km, but valve train was not replaced. I've told them to turn back the pump flow, but some engines hava a timing adjustment as well (Volvo, at least). Was wondering about Toyota.
 
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