Is warming up an engine a good thing?
01-03-2013, 07:39 AM
#1
Member
Thread Starter
Is warming up an engine a good thing?
My 218K mi 1991 190E has always been warmed up when the temps are below 40 degrees F. I let it warm up not all the way to 80C...but at least to get the temp needle off the step.
Piston engine aircraft require warmups to make sure they are at operating temps before the engine forces for takeoof. I used the same logic for cars.
Any thoughts on this welcome as its an ongoing family discussion.
BTW its 5 degrees F right now in Ohio...
Piston engine aircraft require warmups to make sure they are at operating temps before the engine forces for takeoof. I used the same logic for cars.
Any thoughts on this welcome as its an ongoing family discussion.
BTW its 5 degrees F right now in Ohio...
01-20-2013, 12:53 AM
#2
It does make a big difference for Mercs of this vintage. The oil journals seem complex as there is a dramatic difference in pressures between warm and cold engines, I'd guess if you made a habit of driving cold you'll start blowing seals prematurely, lot of seals on these jetronic vacuum masterpieces. The bottom end is near bulletproof but it's carefully designed to bring different metals within to similar operating conditions, failing to warm them up means some parts are expanded to running condition and some aren't, bulletproof can become fragile when you run them outside their normal tolerances and too cold is as bad as too hot.
It does work the same for aero engines, which can't afford to just break down in the sky. So pilots strictly enforce operational guidelines, which concentrate on things like oil temp and pressure, induction vacuum/boost, fuel grade, piston speed/temp, exhaust temp.
Race cars also have many of these guages for similar reasoning. You run them like an engineer, you have operational parameters and guages to ensure the operator keeps the vehicle operating within the guidelines. Only half the game is driving it.
These parameters include operational temperatures.
Anecdotally I find the engine kept in better tune, lower workload in normal driving, and more ready to operate at peak performance suddenly. I notice the difference and debilitation between cars I'm looking after and warming up, and ones I don't and just brutalise. You can feel the horsepower loss over time.
It does work the same for aero engines, which can't afford to just break down in the sky. So pilots strictly enforce operational guidelines, which concentrate on things like oil temp and pressure, induction vacuum/boost, fuel grade, piston speed/temp, exhaust temp.
Race cars also have many of these guages for similar reasoning. You run them like an engineer, you have operational parameters and guages to ensure the operator keeps the vehicle operating within the guidelines. Only half the game is driving it.
These parameters include operational temperatures.
Anecdotally I find the engine kept in better tune, lower workload in normal driving, and more ready to operate at peak performance suddenly. I notice the difference and debilitation between cars I'm looking after and warming up, and ones I don't and just brutalise. You can feel the horsepower loss over time.
Last edited by vanir; 01-20-2013 at 01:03 AM.
01-20-2013, 04:01 PM
#3
Member
Thread Starter
Thanks much!
Hi Vanir...thanks for the commentary...I do think that my modest warm ups have led to my 190E having a pretty good life so far. Will save this link for future reference during family discussions...
I also plan to post this question on the ML board as well...likely the same benefit I think...
I also plan to post this question on the ML board as well...likely the same benefit I think...
01-21-2013, 06:02 AM
#4
Cheers mate, you're quite welcome. Clearly it gets very cold where you live, -15C is roughly a typical Russian winter, the kind that killed Napoleon's troops 
Tell you a bit of trivia about auto and aero engine relationships, since you brought them up and I like talking about these things...
Firstly the engine speed range of auto engines is roughly analoguous to altitude pressure effects on the operation of an aero engines. When looking for performance variation in aero engines, basically the same things you do to make an auto engine work better at high rpm are what you do to make an aero engine work better at higher altitude. They proverbially substitute rpm for altitude range from an engine builder's point of view but are basically the same animal, just something interesting I noticed. The basic aero engine is equivalent to fully race prepped in build quality, but tuned for operational speeds of 1800-3000rpm typically (means high velocity induction rates where with a high rpm engine you want low velocity rates for bigger volume). So aero engines have a lot of features you might see in autosport, like dry sump oiling to avoid g-loading problems. Auto engines already use pressurised cooling or air.
Another point of difference despite being the same animal is output ratings and why. Any four stroke develops horsepower and torque because they're different kinds of measures, one is a force and the other an amount of work achieved.
What this means is at 100% efficiency a motor puts out the same torque as it does horsepower. The torque curve measures the force applied, the horsepower curve the reciprocal momentum keeping it going.
In aero engines they work fairly simply like this with actual power ratings dependent upon flight management settings, but essentially torque pushes horsepower and they're not real far apart among engine settings. Technically throttle/boost sets torque and prop pitch induces drag, influences engine speed and between them sets horspower, you do lose less with reduction gear so bigger props are better if the torque can handle it.
With auto engines you detune this efficient concept and actually reduce the volumetric efficiency in order to split the torque and horsepower curves wider apart in the engine speed range. Then you build the motor to handle engine speeds at peak horsepower which might be at 5000rpm, and induction/valve tuning for low rpm so it drives nice under the torque curve at 2000rpm.
The reason is engine flexibility, building engines to higher volumetric efficiency raises power output significantly and with it economy, but tuning a single minded build for maximum output gets you an aero engine with a normal speed range of maybe 2250-2800rpm but great performance at its rated altitude. To get a driving range of 2000-5000rpm for autos you have to kill efficiency and point build efforts to low speed qualities, but build the motor to handle high speed operation, there's your typical car engine. You fatten the torque curve, sacrifice some of that potential, and you kill horsepower because by the time torque peaks and reciprocal mass takes over the flow dynamics have run out of puff because it's up around 3500rpm and the tuning is for 1500rpm airspeeds to fatten the torque curve down the driving range for towing and acceleration. That's why older engines have much higher torque than horsepower.
Newer twin cam multiple valve setups also handle high speed induction demands, so their significant contribution to automotive performance is much higher horsepower ratings for the same torque, but tuning has to be a bit split personality (enter variable length manifolding, variable timing camshafts, hyperfast ECUs and improved management).
In some ways auto engines are more demanding and refined that aero engines. Their driving range is not designed by the best mechanical decision, but by the best circumstantial compromise to ensure the engine conforms to requirements, in aeronautical engineering to an extent it has to be the other way around for safety reasons.
Auto engines also are engineered by their induction rates and mechanical timing to balance the two power curves for a usable driving range and best performance compromise. With so much room to move the bar with auto engines it also means tremendous variation among and within manufacturers, some engines focused more on high efficiency and bringing horsepower and torque curves back together (ie. 5000-7000rpm max performance operating speeds), and others focused more on high efficiency under economical conditions, with a strong mid range and crisp low speed response.
An aero engine you just tune for its 4-5 preset power settings (2 economy, 2 normal and 1 emergency/overboost). You don't exactly rev the engine.
Tell you a bit of trivia about auto and aero engine relationships, since you brought them up and I like talking about these things...
Firstly the engine speed range of auto engines is roughly analoguous to altitude pressure effects on the operation of an aero engines. When looking for performance variation in aero engines, basically the same things you do to make an auto engine work better at high rpm are what you do to make an aero engine work better at higher altitude. They proverbially substitute rpm for altitude range from an engine builder's point of view but are basically the same animal, just something interesting I noticed. The basic aero engine is equivalent to fully race prepped in build quality, but tuned for operational speeds of 1800-3000rpm typically (means high velocity induction rates where with a high rpm engine you want low velocity rates for bigger volume). So aero engines have a lot of features you might see in autosport, like dry sump oiling to avoid g-loading problems. Auto engines already use pressurised cooling or air.
Another point of difference despite being the same animal is output ratings and why. Any four stroke develops horsepower and torque because they're different kinds of measures, one is a force and the other an amount of work achieved.
What this means is at 100% efficiency a motor puts out the same torque as it does horsepower. The torque curve measures the force applied, the horsepower curve the reciprocal momentum keeping it going.
In aero engines they work fairly simply like this with actual power ratings dependent upon flight management settings, but essentially torque pushes horsepower and they're not real far apart among engine settings. Technically throttle/boost sets torque and prop pitch induces drag, influences engine speed and between them sets horspower, you do lose less with reduction gear so bigger props are better if the torque can handle it.
With auto engines you detune this efficient concept and actually reduce the volumetric efficiency in order to split the torque and horsepower curves wider apart in the engine speed range. Then you build the motor to handle engine speeds at peak horsepower which might be at 5000rpm, and induction/valve tuning for low rpm so it drives nice under the torque curve at 2000rpm.
The reason is engine flexibility, building engines to higher volumetric efficiency raises power output significantly and with it economy, but tuning a single minded build for maximum output gets you an aero engine with a normal speed range of maybe 2250-2800rpm but great performance at its rated altitude. To get a driving range of 2000-5000rpm for autos you have to kill efficiency and point build efforts to low speed qualities, but build the motor to handle high speed operation, there's your typical car engine. You fatten the torque curve, sacrifice some of that potential, and you kill horsepower because by the time torque peaks and reciprocal mass takes over the flow dynamics have run out of puff because it's up around 3500rpm and the tuning is for 1500rpm airspeeds to fatten the torque curve down the driving range for towing and acceleration. That's why older engines have much higher torque than horsepower.
Newer twin cam multiple valve setups also handle high speed induction demands, so their significant contribution to automotive performance is much higher horsepower ratings for the same torque, but tuning has to be a bit split personality (enter variable length manifolding, variable timing camshafts, hyperfast ECUs and improved management).
In some ways auto engines are more demanding and refined that aero engines. Their driving range is not designed by the best mechanical decision, but by the best circumstantial compromise to ensure the engine conforms to requirements, in aeronautical engineering to an extent it has to be the other way around for safety reasons.
Auto engines also are engineered by their induction rates and mechanical timing to balance the two power curves for a usable driving range and best performance compromise. With so much room to move the bar with auto engines it also means tremendous variation among and within manufacturers, some engines focused more on high efficiency and bringing horsepower and torque curves back together (ie. 5000-7000rpm max performance operating speeds), and others focused more on high efficiency under economical conditions, with a strong mid range and crisp low speed response.
An aero engine you just tune for its 4-5 preset power settings (2 economy, 2 normal and 1 emergency/overboost). You don't exactly rev the engine.
01-21-2013, 09:56 PM
#5
Member
Thread Starter
Vanir...thanks for the exhaustive readout!
Very helpful details...indeed that car engines are more refined and demanding than aero engines....one only needs to look at our CAF Dixie Wing SBD to see how it gets thru the air...just a big radial out there with gallons of oil...
www.dixiewing.org
www.dixiewing.org
01-22-2013, 06:22 PM
#6
Radials...face painters You know the reason they started putting cowlings on radials? Not aerodynamic reasons but purely because they spray oil over the windscreen or pilot's face. NACA further developed the radial cowling later to improve aerodynamic qualities but it was never the reason they were first fitted.
There are these old 50s Russian 6-seaters that use a big shvetsov radial, I'd love to own one of those, maybe a floatplane version, be like a mobile air home. Some friends are actually building an airfield on a property they bought in Queensland (I'm in Oz), his wife is ex-Hellenic fighter pilot so they know what they're doing. They're waiting on local government clearance for it (they're offering it as an air-ambulance refuelling base).
You know the reason they started putting cowlings on radials? Not aerodynamic reasons but purely because they spray oil over the windscreen or pilot's face. NACA further developed the radial cowling later to improve aerodynamic qualities but it was never the reason they were first fitted.There are these old 50s Russian 6-seaters that use a big shvetsov radial, I'd love to own one of those, maybe a floatplane version, be like a mobile air home. Some friends are actually building an airfield on a property they bought in Queensland (I'm in Oz), his wife is ex-Hellenic fighter pilot so they know what they're doing. They're waiting on local government clearance for it (they're offering it as an air-ambulance refuelling base).
