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SimonInAustralia wrote:Does the precombustion chamber cracking only occur with boosted engines, or does that happen anyway?
but it's all about heat and a turboed engine will run hotter than a standard one.
i agree with drr fully but just to further clarify "run hotter" is not just the guage or cooling system but the little bits of metal inside the combuston chamber exposed to the combustion process
no amount of radiator or cooling system capacity can stop this as its directly on the flame front
the only way to stop it is to not have such thin bits of metal in the flame front so that the heat can be conducted away
ENTER THE 1hd series engine !!!!!!!!!!!!
with direct injection
80 series 1980 hilux cab supra twin turbo engine
1hdfte 80 series
LHD fz 80 series GX
thrashlux wrote:i agree with drr fully but just to further clarify "run hotter" is not just the guage or cooling system but the little bits of metal inside the combuston chamber exposed to the combustion process
no amount of radiator or cooling system capacity can stop this as its directly on the flame front
Exactly what I was getting at. I probably should have expanded on it myself.
Frankenyota wrote:Why don't mitsubishi etc with indirect injection turbo motors suffer from head problems?
Or is this problem related to the 1HZ head design.
Matt
the nissans 4.2's are fine as well and the old 2h can handle it better
it is just the way the 1hz is cast (its inherent design)
ie how close the valves are to the precom chamber ( the amount of metal between them to take the strain)
the precomchambers are made from a different kind of material to the rest of the head (they have some very thin small sharp edges)
they get hot expand contract etc and they do it at a different rate to the rest of the head causing cracks normally thru from the precom chamber to the valve seat ans eventually to the water jacket (this is when you start to notice) cause your truck starts to warm up when you go up hills
there is just not enough metal there
80 series 1980 hilux cab supra twin turbo engine
1hdfte 80 series
LHD fz 80 series GX
Frankenyota wrote:Why don't mitsubishi etc with indirect injection turbo motors suffer from head problems?
Or is this problem related to the 1HZ head design.
Matt
the nissans 4.2's are fine as well and the old 2h can handle it better
it is just the way the 1hz is cast (its inherent design)
ie how close the valves are to the precom chamber ( the amount of metal between them to take the strain)
the precomchambers are made from a different kind of material to the rest of the head (they have some very thin small sharp edges)
they get hot expand contract etc and they do it at a different rate to the rest of the head causing cracks normally thru from the precom chamber to the valve seat ans eventually to the water jacket (this is when you start to notice) cause your truck starts to warm up when you go up hills
there is just not enough metal there
Ok so just a thought here.. cracking heads might be exaggerated by bad warm up and warm down...
comes from my aircraft knowledge in the area.. ever been in a small plane? warm up and warm down is CRUCIAL to engine longevity.
say you jump into a 1hz thats cold, jump straight on the accelerator and flog it before it's properly warmed up.. the bit's of metal prone to heat cracks will be changing temperature fairly rapidly, creating some cracks.. now add on 12psi and some more diesel.. the temps will change dramatically, creating more of an opportunity for cracks to occur.. also warm down is just as important in engines with heat fatigue issues. if you have just gone up a big hill towing a trailer in a boosted 1hz, get to the lookout at the top and turn the engine off before allowing it to run down, the high temp parts of the engine will cool down at different rates to the rest of the engine.. again causing cracks??
crunk81us wrote:Ok so just a thought here.. cracking heads might be exaggerated by bad warm up and warm down...
comes from my aircraft knowledge in the area.. ever been in a small plane? warm up and warm down is CRUCIAL to engine longevity.
say you jump into a 1hz thats cold, jump straight on the accelerator and flog it before it's properly warmed up.. the bit's of metal prone to heat cracks will be changing temperature fairly rapidly, creating some cracks.. now add on 12psi and some more diesel.. the temps will change dramatically, creating more of an opportunity for cracks to occur.. also warm down is just as important in engines with heat fatigue issues. if you have just gone up a big hill towing a trailer in a boosted 1hz, get to the lookout at the top and turn the engine off before allowing it to run down, the high temp parts of the engine will cool down at different rates to the rest of the engine.. again causing cracks??
just thinking out loud here..
The problem is dissimilar metals and different expansion and contraction rates. The precombustion chambers are different to the head itself and a lot of the cracks start around and behind the precombustion chambers. 1kz's are the same.
Yes, it would probably help if the engine was warmed and cooled a lot slower, but who has time for that? They should just build them properly and there wouldn't be a problem
I think another problem with 1hz's are also people not setting valve clearnaces properly as its a fairly big job. Before i turboed my engine i did all the tappets and found one exhasut with only 4thou clearance. Spec indicates 6-10 on inlet and 14-18 on exhaust.
Soon as valves dont seat properly heat isnt exchanged between the valve and the seat. Gasses pass the valves and burn them out. With the hotter combustion temps of the turboed engine this will deteriate at a faster rate. Once again this isnt the engines problem. I set mine at 10 and 20. They rev and respond so much better with correct clearances, plus you will get much longer out of your cylinder head life if you keep ontop of this.
