Quote:
Originally Posted by mikels
First Thomson 427SC engine was built and run way back in 2008. This was for his Pontiac Solstice and utilized LSX block, LS7 heads and Harrop 2300SC. Engine made 990+ crank HP with an aggressive cam, and dropped to 850 crank HP with milder cam as installed in car. After over 100 dyno pulls and 5000+ miles installed in car, engine was disassembled and all parts blueprinted / inspected for wear. All looked great. Keep in mind this was never used for road-race or extended high duty cycle use, so powertrain cooling was never an issue.
At same time this was ongoing, Thomson was developing a twin-turbo LSX generating 2000+ HP. Original engine was 440 CID and dyno testing reveled that after few pulls, crank bearings were distressed, and had they not been coated bearings, a bearing failure would have been likely. Issue was traced to crank deflection under load, so stroke was shortened (increased overlap of throws and mains) to increase strength. Engine then completed 150 full power pulls on dyno (2058 HP average) and subsequently disassembled. All bearings looked like new.
Fast-forward to today:
Based on these and countless other engine builds, testing and further development, Thomson 427SC engines have proven themselves robust even under extreme racing type usage (Mark's cars being one of the most aggressive test beds used). We continually refine and improve package based on knowledge gained over each build and test data. This includes not only hardware selection, but assembly clearances, powertrain cooling requirements and calibration refinement.
Mark has said on many occasions that not only are the Thomson 427SC engines the most powerful he has ever utilized in his builds, they have also been the most reliable and driveable as well. And hard to dispute the results.
Not sure if this directly answers your question as we lack the technology to measure oil film thickness, but empirical data based on many, many engines supports where we are today (with headroom to grow  ). |
And...
Quote:
Originally Posted by mikels
In this case, there is 3 sources of heat - engine, supercharger and AC. Breaking that down further, engine heat in form of coolant and oil, supercharger heat in form of air and AC in form of refrigerant.
Engine heat in coolant and oil comes from the inefficiencies of an IC engine - only about 1/3 the energy released from combustion actually makes power, another 1/3 goes into cooling system (coolant & oil) and 1/3 goes out exhaust.
Since this is a SC engine, also have to take into account mechanical energy used to drive supercharger - in Red Devil and Mayhem, this worked out to ~120-140HP. So Mayhem generating an output of 878 HP is actually generating over 1000 HP already - and that also nearly equals the amount of energy we need to release from cooling system.
Complicating this further, we have the heat from the intake air charge to reduce as well - and use air-to-water heat exchanger with a stand-alone cooling system to then convert this with a water-to-air heat exchanger in front of car. Since delta-T is critical for heat exchanger effectiveness, we package the intercooler radiator in front of the cooling stack (all the heat exchangers in front of car) to get greatest delta-T for charge air cooling. This adversely effects radiator efficiency as air temp reaching front face of it is already heated above ambient. And we have 1000+ HP worth of heat to dissipate from it.
Packaged between the CAC (charge air cooler radiator) and the coolant radiator is the AC condenser. At least Mark hasn't become too much of a wimp is his old age to want to race with AC on, so while this doesn't add heat to air flowing through, it does add pressure drop of airflow through entire cooling stack.
We also have engine oil to contend with - and can either use oil-to-air heat exchanger, or oil-to-water. If oil-to-water, this is more KW to release through radiator. If oil-to-air packaging, airflow restriction and preheated cooling air have to be considered.
All this is converted to heat transfer equations and calculated to optimize the entire cooling system of heat rejection balance.
Drag racing is easy - you can get away with a whole lot if only running in <10 second bursts of WOT. Road racing makes this much more difficult as entire system reaches equilibrium.
And haven't even talked about trans and diff oil cooling yet....
Dave
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Wow... This is above and beyond the most informative, real-world experience information I have ever read on a forum of any kind. On occasion I think I have most all the knowledge I need to accomplish a goal, then I get slapped into reality with posts like these and it makes me thirsty for more information.
I am so grateful that you guys share this information with us, I learn something every day on this site. Being a "fly on the wall" has never been so interesting!
Thanks!!!
