PreCup temp ..
- Thread starter Tapage
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Interesting read 
I have a 3B with a turbo and always run at idle when arriving at my destination until the EGT's drop to about 325 or so, perhaps the slower cooling might give a longer life to the pre-cups. I left the fuel as-is as well, didn't turn it up. EGT's max at about 950 the way I drive it.
I always thought turbo timers were used to prevent excessive heat from remaining in the engine, but perhaps they are best served to slow the cooling of the engine?
Thanks for the information!
I have a 3B with a turbo and always run at idle when arriving at my destination until the EGT's drop to about 325 or so, perhaps the slower cooling might give a longer life to the pre-cups. I left the fuel as-is as well, didn't turn it up. EGT's max at about 950 the way I drive it.I always thought turbo timers were used to prevent excessive heat from remaining in the engine, but perhaps they are best served to slow the cooling of the engine?
Thanks for the information!
Bit off topic, however, turbo timer is more to cool the turbine shaft and housing before water cooling becane the norm. Jump off the throttle and watch the boost gauge drop, thats how quick a turbo loses shaft speed. makes me wince but a lot of the guys at work where i do the wrenching, shut em down as soon as they pull up, all turbo diesel, all water cooled these days. Very rare to have a crook turbo under 300k
So is the issue high coolant temps?
IDI td42s have similar issues when pushed hard although we seem to be having success with a modified fan design and different clutches, they even like to overheat in standard form and now are staying cool with 200+kw
IDI td42s have similar issues when pushed hard although we seem to be having success with a modified fan design and different clutches, they even like to overheat in standard form and now are staying cool with 200+kw
Heating and cooling metal has a predictable effect on it and I remember reading about different types of metals like inconel vs stainless steel and the "cycles" you can expect from them. When I said precups break from neglect I mean folks basicaly run their engines completely ignorant of they fact that they are an item that requires replacing just like a timing belt or an injector or any other item like that. Its life might be longer, but it still should have a scheduled maintance regime rather than wait till it breaks and curse the design. If you waited till your timing belt broke and hated timing belts cus they chuck rods out the side of engines no one would really take you too serously.
Coolant temps shouldnt be able to influence your precup temps much as its going to normalize to your incylinder combustiopn temps regardless of what the head is. Changing your coolant temp by 20 degrees wont mean much if your precup is 1000F all the time. Strangey though running cooler colant temps will lead to greater waste as there will be greater disparity between the combustion temps and the coolant leading to more thermal transfer.
Running more fuel in the engine for more power will lead to greater waste heat going into the coolant system. Something like 1/3 of the BTU of the fuel is coolant waste so if you double your fuel its not to weird to think you just doubled the thermal load on your coolant system. If your system is old and decrepid, much like many of your cruisers are, it wont take much to overwhelm it. Shoot some of our truck have a hard time driving on the freeway in the summer.
Coolant temps shouldnt be able to influence your precup temps much as its going to normalize to your incylinder combustiopn temps regardless of what the head is. Changing your coolant temp by 20 degrees wont mean much if your precup is 1000F all the time. Strangey though running cooler colant temps will lead to greater waste as there will be greater disparity between the combustion temps and the coolant leading to more thermal transfer.
Running more fuel in the engine for more power will lead to greater waste heat going into the coolant system. Something like 1/3 of the BTU of the fuel is coolant waste so if you double your fuel its not to weird to think you just doubled the thermal load on your coolant system. If your system is old and decrepid, much like many of your cruisers are, it wont take much to overwhelm it. Shoot some of our truck have a hard time driving on the freeway in the summer.
- Thread starter
- #28
I did the alum rad experiment with stock fan and fan clutch .. then did the 18K oil to the fan clutch and then got back to copper - brass rad and electric fans ( front and behind ) and that's how I sit now ..
Again .. I know the nature of the beast and how to live with it .. I can't go bigger how it sits ( out of a major front clip / grid surgery ) out that 4 core copper - brass rad ..
Gerg .. which was the result of your pre cup experiment ( modded pre cup ) ..?
Again .. I know the nature of the beast and how to live with it .. I can't go bigger how it sits ( out of a major front clip / grid surgery ) out that 4 core copper - brass rad ..
Gerg .. which was the result of your pre cup experiment ( modded pre cup ) ..?
Well im driving it right now with timing retarded. Ill bump the timing up when I intercool it some time perhaps next summer. Pulls vey hard down low due to the timing change, but it does have signifigant more power than before througout the rev range. Tuff to tell exactly what to atribute it to exactly cus I took a long time porting the head on it as well and changed the turbos at the same time. Overall egts dropped WOT at 2500 down about 100-150F even with retarded timing. Its by far the the most fun ive had driving a 3B.
Tuff to control heat in your neck of the woods Tap as ambient temps are so high. Gigantic radiator?
Tuff to control heat in your neck of the woods Tap as ambient temps are so high. Gigantic radiator?
- Thread starter
- #30
Today we had between 90 - 100F ( average of 34C or so ? ) with 90% humidity .. not easy to deal with ..
I didn't play with timing in Tencha but did in Marilu ( back when was auto tranny ) and feel like advacing timing make the most benefit from 1K rpm to 3500rpm ..
With 24 PSI on her I'm running pretty lean over 3500 rpm .. and might be part of what I feel ..
So timing works different for IDI ..?
Are you running stock air filter and piping to the intake in your IDI ..? ( 3B i guess ? )
I didn't play with timing in Tencha but did in Marilu ( back when was auto tranny ) and feel like advacing timing make the most benefit from 1K rpm to 3500rpm ..
With 24 PSI on her I'm running pretty lean over 3500 rpm .. and might be part of what I feel ..
So timing works different for IDI ..?
Are you running stock air filter and piping to the intake in your IDI ..? ( 3B i guess ? )
Snorkel, stock air box, 3 inch mandrel bend exhaust no muffler.
Timing is usually more advanced for IDI compared to DI, but increased intake temps can have the effect of thermally advancing timing. I retarded mine to compensate for my high intake temps.
Timing is usually more advanced for IDI compared to DI, but increased intake temps can have the effect of thermally advancing timing. I retarded mine to compensate for my high intake temps.
- Thread starter
- #32
that's good thinking .. are you measuring your IAT vs your EGT's .. ?
I measured my IATs a few years ago to check compressor effeciency and it was around 400f. Conbined effeciencies was like 73% so ok effecient wise, but still alot of heat. Would free up a fair bit of power intercooling. Could really bennifit from an intercooler to say the least. I rebuilt my small turbo and put a more effecient exteded tip 13t compressor on it and will be selling the whole thing evenually and just put a single turbo on as ill be selling the truck next year sometime.
- Thread starter
- #34
400°F with which ambien temps ... sadly with my ambient temps and humidity I've seen a lot more in my setup .. gotta do it again with my new IC in place ..
Really great thread. Thanx for the good info gerg.
Ahh no problem. In hind sight I could have drilled small depressions into the face of the precup that contacts the head gasket to reducae transfer as well as it represents a very large percentage of the overall contact area.
I also thought of blending the opening of the precup on the piston side, but was not sure if allowing more air into the prechamber was a good thing. Reducing pumping losses would be a bennifit, but allowing more air in might allow for a more complete burn in the prechamber and more heat to soak and be lost into the head. Im still not sure on that. I could see it agrued either way. Changing the opening so that it interferes with the jet and how it acts upon the piston contures will also allow the flame front to contact the cylinder walls to a larger degree which is a definate power loss. Lots of incomplete combustion on or near cylinder walls.
I also thought of blending the opening of the precup on the piston side, but was not sure if allowing more air into the prechamber was a good thing. Reducing pumping losses would be a bennifit, but allowing more air in might allow for a more complete burn in the prechamber and more heat to soak and be lost into the head. Im still not sure on that. I could see it agrued either way. Changing the opening so that it interferes with the jet and how it acts upon the piston contures will also allow the flame front to contact the cylinder walls to a larger degree which is a definate power loss. Lots of incomplete combustion on or near cylinder walls.