Competition Simple Performance In Relation To Temp Question

[ProMac1K]

This is probably a simple one-reply question but I thought I would post it since there could be several opinions, and this could be a good debate. What is the preferred or optimum engine coolant temp for HP or going after performance on a diesel engine? Also what about ambient temp? There has to be a few variables for optimum ambient temp considering for instance humidity affecting an air-to-fuel ratio or something to that effect. But I thought that I would throw this out to get a feel for everyones opinions and experiences.

 

[COMP461]

This ought to be an interesting subject, here goes.

I go to the line with an almost dead cold motor, but that is predicated by several other factors, I run different clearances then some, and the oil I run is a Lucas Oil pro stock oil with a friction modifier. This oil is a synthetic, and has very good protection quality. In the old days in performance driven classes, you would bring the motor up to operating temperatures to thin the oil and put heat in the aluminum rods. Now with the new rods there is no need, and the oils we run now are very thin. The oil I run is Lucas 0 w 5, there are 5 grades thinner then that, and it starts to look like Coca-Cola.



The key is warm your motor up to a reasonable temp, and make some pre heat in the exhaust tract . Before you stage, bring the motor up gently and build heat on your pyros, this doesn’t have to bellow out smoke in copious amounts, but it builds heat. When it get as high as possible, you can role in and have a reasonable chance of getting up on the chargers.

What a lot of guys should start understanding is that drag racing Diesels are not tractor pulling Diesels , we run the motor differently, and have different requirements of them. Just like a 555 CID Reher Morrison motor is built differently if its intended use is in a boat, and not a 8. 90 super comp car. A tractor puller has no restriction on the amount of time he has to spool, the amount of smoke, and leaking what ever on the track. A drag racing Diesel must also have the ability to REV GAIN, which is to accelerate up the rpm band with out losing a significant amount of power.

 

[J.Davy]

Not sure about a diesel ,I would like to know what the continued operation ideal temp would be?Two stroke gas engines are around 90f to 100 f and I think 4 stroke superbikes make their best power around 140 f.

 

[ProMac1K]

Hmmmm... ... . I guess no one on here knows anything about performance besides Comp! I guess it didn't take a new topic to figure that out.



Thanks for the info Comp!

 

[J.Davy]

I would think it is going to change for application,for drag racing it is going to be like Comp posted but for everyday driving you would proably have to run the oil temp hot enough to boil of any moisture or condensation that would accumulate,but providing you keep the oil hot I would think the colder the coolant the better untill atomization becomes a problem.

 

[mcoleman]

I agree with Comp on being cool. My truck will loose power on the dyno on each pull as heat soak occurs. Usually about 1 to 2 horsepower per pull. I always tried to pull to the lights at 160 degrees with my bracket cars. But I was after consistentency in those.

 

[RustyJC]

If you want maximum theoretical BHP, it's all about air density. That means you want everything as cold as possible - the engine needs just enough heat for good combustion. You can always add more fuel - the limiting factor in producing BHP is how much air you can shove into the cylinder to burn with the fuel. The colder the air is, the more mass of air you have in the cylinder per unit of volume at the end of the intake cycle when compression begins.



If your definition of performance includes specific fuel consumption, the rules change. Now you want to reject as little heat to the cooling jackets as possible, so hotter coolant temperatures (up to a point) are better. This serves to reduce the thermal gradient between the combustion area and the cylinder walls, combustion chamber surfaces, etc. , thereby minimizing heat loss. As an example, remember the engine builders' efforts to develop a ceramic engine that didn't even have a cooling system?



Rusty

 

[Ted Jannetty]

Excellent answer rusty but maybe above and beyond what he is asking.

Strickly from expereince having owned, driven, and modifed diesels for the last 15 years I will say this.

Ambient temps of around 40 degrees farenhiet gives the best all around performance and mileage, power degrades on either side of this temp in a linear fashion.

This has to do with final charge air temps, below this there is too much heat loss to the charge air for good combustion and above this the available oxygen degrades.



Water temps of 180-190 give the best all around performance and fuel economy, same sinerio as above.

 

[COMP461]

The question of heat loss thru the water jacket, and the need to have in a gas motor a cool cylinder head, has been something a few prostockers have tried. They only circulate cooled fluid in the head, letting the block remain dry or wet with circulating static fluid in the block. This has been tried several times as some teams go back and forth. The loss of BTU of heat energy in the chamber is most critical fro about 30 degrees after TDC then it doesn’t mater, because the push of expanding combustion gasses is not sufficient to chase the piston down the bore.

I believe in a diesel the same could be true , keep the block as hot as possible to not cause ring scuff , , this requires different ring clearances ,and cool the head as much as possible. I have a new head gasket just for that, it doesn’t allow water transfer between the head and block. Obviously this is in a race only application. I will also blank off the oil and intend on sending it in another fashion. I think some times the symptoms of what we think is a head gasket leak is really the or several things first the BHJ tool most people use to put O-rings groves in , is not very consistent , I have check several head done by other, and found then to very by as much as + -. 004 when the wire is only out 12 this causes a big problem , this should be done on a mill. The leaks we see is what I think to be head gasket seep, this is common in top fuel and the alcohol ranks. In that they have no water or oil transferring between the head and block, hence no problems.

Just a few thoughts this morning , maybe I should wake up ,

 

[RustyJC]

The loss of BTU of heat energy in the chamber is most critical for about 30 degrees after TDC then it doesn’t matter, because the push of expanding combustion gasses is not sufficient to chase the piston down the bore.

You might want to look at a pressure-volume (PV) diagram for a diesel engine. Although cylinder pressure drops as the piston travels down the bore following the injection event (during injection, combustion is theoretically at constant pressure), so long as the pressure above the piston is greater than crankcase pressure, useful work is being extracted. Cylinder pressure is higher than crankcase pressure all the way to exhaust valve opening (the blowdown event) and even after, but pumping losses are the subject of another discussion.



Heat flux (the loss of BTU's to the cooling system, to radiation, etc. ) isn't nearly as important to a racer who's throwing unburnt fuel out the stacks as it is to an engine designer who is trying to squeeze every last iota of power from a gram of diesel fuel to maximize thermal efficiency and minimize brake specific fuel consumption for industrial or over-the-road applications.



Rusty

 

[COMP461]

You might want to look at a pressure-volume (PV) diagram for a diesel engine. Although cylinder pressure drops as the piston travels down the bore following the injection event (during injection, combustion is theoretically at constant pressure), Rusty

Where did you get this misinformation a diesel is no different any other internal combustion engine , I have seen piezio sensor graph of most all forms of internal combustion engines, this is a pressure transducer of the environment inside the combustion chamber. The pressure is a sudden spike at around 2500 to 3000 lbs psi if the tune is right then that happens about 15 to 20 degrees ATDC this pressure falls off very rapidly after that, the amount of power added after that is almost nothing. Your just misinformed.

so long as the pressure above the piston is greater than crankcase pressure, useful work is being extracted. Cylinder pressure is higher than crankcase pressure all the way to exhaust valve opening (the blowdown event) and even after, but pumping losses are the subject of another discussion. Rusty

That work is just like 4 guys pushing a fraternity chariot in a Greek race, you might still be pushing, but the amount of work you’re doing is not worth it. The pressure in the crank case in my motor is a vacuum, at best with the smog pump on my motor, but the reason for that is windage the pressure should never get to any appreciable amount.

Heat flux (the loss of BTU's to the cooling system, to radiation, etc. ) isn't nearly as important to a racer who's throwing unburnt fuel out the stacks as it is to an engine designer who is trying to squeeze every last iota of power from a gram of diesel fuel to maximize thermal efficiency and minimize brake specific fuel consumption for industrial or over-the-road applications. Rusty

With the thought of the unburned fuel out the stacks, that in a real racing diesel is a total waste , its heats the exhaust track but doesn’t produce one more hp then a total clean stack with a hint of gray. Remember lean is mean, as long as you use all the oxygen in the chamber. The extra fuel is carburized; in to the black useless soot every one loves so. And in the process absorbs heat, and the potential energy, but also using the oxygen in a fassion the dose not release energy.

 

[JoshPeters]

Where did you get this misinformation a diesel is no different any other internal combustion engine , I have seen piezio sensor graph of most all forms of internal combustion engines, this is a pressure transducer of the environment inside the combustion chamber. The pressure is a sudden spike at around 2500 to 3000 lbs psi if the tune is right then that happens about 15 to 20 degrees ATDC this pressure falls off very rapidly after that, the amount of power added after that is almost nothing. Your just misinformed.







.

What he is saying is exactly what you are saying... . just in different wording.



What you both are trying to say is this. Compression occurs, and pressure is lets say 1000psi. Combustion/injection occurs and it spikes to lets say 2750psi. Once it spikes it plateau's out for a time as the gasses expand/Combustion occurs till you hit approx 15-20 degrees of crank rotation, then they drop off. When he says "combustion event" he is speaking of the 20 degrees of rotation that the gasses are still expanding and pressure is close to a constant. During that time combustion is still taking place.



Hopefully I've helped clear this up..... rather than confuse anyone!



Josh

 

[RustyJC]

Where did you get this misinformation a diesel is no different any other internal combustion engine , I have seen piezio sensor graph of most all forms of internal combustion engines, this is a pressure transducer of the environment inside the combustion chamber.

Check THIS out insofar as the PV of a diesel is concerned. Thermodynamically speaking, the ideal combustion process in a Diesel cycle is isobaric - i. e. , constant pressure during the injection event. After the completion of combustion (injection cutoff), the remainder of the power stroke sees pressure decline as cylinder volume increases, but energy is still being extracted. Isobaric combustion is one of the primary differences between the Diesel and Otto cycles. All internal combustion engines are most certainly NOT all alike. Even within the basic Otto cycle (spark ignition) design, we see such variations as the Atkinson cycle, the Miller cycle and others.

Your just misinformed.

Actually, the correct usage is "you're". Well, let's see - I'm a mechanical engineer who has worked for a diesel engine manufacturer for 31 years, 25 of those in technical management. I was involved in the design of the EnSpec 2000 maintenance and EnSpec 3000 performance engine/compressor analyzers. I guess one of these days I'll have to get you to explain to me how diesel engines work!



Rusty

 

[Cooker]

Excellent answer rusty but maybe above and beyond what he is asking.

Strickly from expereince having owned, driven, and modifed diesels for the last 15 years I will say this.

Ambient temps of around 40 degrees farenhiet gives the best all around performance and mileage, power degrades on either side of this temp in a linear fashion.

This has to do with final charge air temps, below this there is too much heat loss to the charge air for good combustion and above this the available oxygen degrades.



Water temps of 180-190 give the best all around performance and fuel economy, same sinerio as above.

Ted, good to see you are still around.

 

[Ted Jannetty]

Ted, good to see you are still around.

Yeah I am still here busy and bigger than ever.



We added 4000 sq. ft. building with Superflow Chassis Dyno and Hunter alignment equipment to our already impressive arsnal of equipment.



I do more reading than writing though.

 

[BushWakr - RIP]

I wonder if anyone can give me some thoughts on something I read in the literature from one of the guage makers.....

The statement was that with every one degree of ambient/intake air temp increase, your EGT will rise 3 degree's F... .

Is this an accurate statement ... assuming all other factors remain unchanged... :?????



bob...

 

[JoshPeters]

I would think you could talk to..... I can't remember... please correct me it was either Jim Fullmer or Jetpilot that had Intake air temp sensors, one pre intercooler, one after intercooler, and of course the EGT guage. That person would be able to tell you best!



Josh

 

[ProMac1K]

Think that was Fulmer.