Why does a lean engine run hot?

[goku]

Originally Posted by alexander

you want me to take a picture of my dad's intake manifold in his tdi, or will you just trust my word... they throttle air like any other car does....

what is "tdi" ?
none of my diesel tractors throttle air intake, or restrict air flow

[DFINITLYDISTRUBD]

Turbo Direct Injected

Is a Volkswagen/Audi group diesel motor.

[alexander]

first, jab, props for having a unimog, you certainly dont see a lot of those in the states, and too bad, they are some cool machines, and very, very reliable, i might add

ok, ok, i think i finally figured it out, after doing much research and scratching my head i got around the hurdle of controlling air intake in diesels...

i think it really depends on the maker, and i think most, in their later development and testing have refrained from using air throttling in diesels... there is very little need for it, because the burning process is controlled solely by the amount of fuel that is injected and its timing, vs the mixture ignition... its mainly due to the timing of when the fuel is injected, i was stuck in the gasoline engine world, but i think i'm over it... my dad's tdi still has a valve, i think the newer jetta's no longer have that design, i will check (i know someone who has a new one ) but my understanding of engines is yet again progressed

I loves learning

[jab2]

Alexander, how's your access to USSR (Russian) military vehicles. The ones I've seen also do not use throttle bodies.

All the diesels I have ever seen in such detail, did not utilise a throttle body as power control is as you mentioned by way of fuel quantity. The newer diesels, Tdi/CDI etc, are so covered in decorative plastic covers that it is virtually impossible for one to get a clear view of the engine auxiliaries without disassembling all those stuff, so I do not have a clue how my Tdi operate. I have also read that one of the reasons for lower fuel consumption for a diesel is that it has no pumping loss due to absence of a throttle body.

Yes, the Unimog is a nice vehicle. A pity I'm losing mine to rust. My 1979 model (416.162) was imported into SA as a running chassis under agricultural equipment to circumvent the arms embargo in place during the apartheid era. It was give a mild steel body with square tubing, angle iron and sheet metal by the military supply organisation. Due to cost and presumably "low life expectancy" it was not even galvanized. At the moment it is not running and I do not have a covered space for it, so it weathers the full force of sea wind. That is really eating away the metal. I also do not have money to work on it now, so have to see it disintegrating by the day. Hopefully the chassis/drivetrain will be more immune to the rust ants.

[alexander]

back home i was too young, now, i wish i had access to it, there are some REALLY nice vehicles in it

actually my dad used to work for some people that had a MAZ-547, it runs a 700bhp turbo diesel with direct injection in a really weird drive shaft configuration... it runs 6 axles front 3 pivot to turn, 3 front axles are linked separately to the transmission from the 3 rears, and they can be driven in different directions (3 axles going forward, 3 reverse) to dig the truck in, at 700bhp the truck can only go 40km/h, but has a fuel capacity range of about 500km. (the pressure in each tire can be adjusted separately too, and it comes with hydraulic stabilizing legs that, once the truck digs in, lift it completely off the ground and level it to an accuracy within less then a millimeter... oh the truck is designed to carry up to 80 tonnes, you know, two of those really big ballistic missiles with a 10000km range, though as a launch platform they can carry only one..

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my dad got to ride one when they had to pull a tractor out of a marsh

they do have a new one MZKT - 79221 (there is a civilian modification) that's 8 axles (all pivot) and an 800bhp diesel that finished development in 97 and has started being delivered to the army in 2000, i think there are a total of 6 now, they look sweet too.

since i mostly deal with civilian engines, they are always quirky and different, the only reason i say i know that my dad's tdi has a butterfly valve is because i had just finished putting it back together after getting a glow plug machined out (so we had to take the head off, and that meant taking everything apart. It's no wrx, you cant take that engine out by yourself in 2 hours, or an s13... my friend, when not rushing, lifts his engine out in 45min, and with the amount of head gaskets he blows (something about his highly turboed, intercooled and auto nitris injected engine), i tell you, its a really neat trick to have...