More on Oil Cavitation, Efficiencies, Thinner Oils

Joined
Jan 9, 2005
Messages
1,452
Location
Sarasota, Florida
I rounded up a few references regarding oil at start-up and thin oil usage. Also, make a note that the collection of oil related articles from this year’s SAE congress will be available as publication SP-1967. Order it. The following are from earlier papers: From Physical Processes Associated with Low Temperature Mineral Oil Rheology: Why the Gelation Index Is not Necessarily a Relative Measure of Gelation, Webber et al: A high viscosity may lead to engine failure because of inadequate lubricant supply. One failure mechanism is from air-binding (? related to cavitation?) and another is from limited or low flow. Wax crystal formation and oil thickening occurs at much higher temperatures than gelation. Borderline pumping temperatures are much lower than air binding temperature related engine failures. (We often look only at the pour point thinking that operation above this is safe. What we see here is that problems occur at temperatures more often encountered.) Low Temperature Oil Pumpability in Emission Controlled Diesel Engines, Mc Geehan et al: At 4 F it took 100 seconds to get up to pressure at the camshaft using a 15W-40 oil, 60 seconds for a 10W-30 oil and 40 seconds for a 5W-40 synthetic oil. The others was mineral oils, all were SJ rated. The final pressure was 10 PSI higher for the synthetic, “thinner” oil. The sequence was 500 RPM x 5 sec., then start, then idle at 1,200 RPM. The 15W-40 oil had zero pressure at the camshaft for 90 sec. The oil only took 8 sec. to get pressure into the main oil gallery. (? 1 - 2 sec to show pressure at the oil filter where the sender is usually located). The oil flow deficiency is from oil vortex formation in the pump and gelation. (If we extrapolate that the oil is half as thick at 40 F then according to some people you should get 1/2 the time lapses as recorded in this study. Also, if the oil is moving this slow (impossible according to the constant volume pump theory) then it would continue to flow this slow and only gradually increase flow as the engine oil temperature increases with operation. Even though the pressure is there we can see the flow must be slow. No flow, no lube.) Similar data was found in: The effects of Crankcase Oil Viscosity on Engine Friction at Low Temperatures, Cockbill et al. The Use of Low Viscosity Oils to Improve Fuel Economy in LD Diesel Engines, Bennett et al: The thinner oils had less friction, better gas mileage. Going from a mineral 5W-20 (7.62, 42, 2.6 - 100 C, 40 C, HTHS) to a synthetic (8.95, 46, 2.7) oil gave 1 percent better gas mileage at a steady state 90 Km/h. There was over a 3 percent improvement over a 10W-30 mineral oil (11.8, 77, 3.4). Fuel Efficient Lubricant Formulations for Passenger Cars or HD Trucks, Benard et al: Friction using a 50 wt oil decreased with less engine speed. Boundary lubrication is negligible. This is confirmed by the lack of effectiveness of friction modifiers. With a 20 wt oil friction decreases with increasing speed. Friction modifiers have an important role. Hydrodynamic lubrication increases with increasing engine speed. In an additive test, friction was tested using a 10W-30 mineral base oil without friction modifiers. 1 percent molybdenum dithiocarbamate increased friction 0.5 percent in one oil and decreased friction 5 percent in another oil. This is secondary to interaction with other additives in the base oil. When using 0.05 percent molybdenum dithiophosphate the friction decreased 8 percent. There was a 9 percent friction reduction adding 1 percent fatty acid C18 ester. (We see the effects of friction modifiers. It is clear you cannot just mix them together. One must look at the whole package to gain benefit with modifiers. Thicker oils gain little with the addition of friction modifiers. Are thick oils with a lot of modifiers just for marketing?) Engine Oil Pumpability Study in a HD Diesel Truck Engine, Neveu et al: This basically was a similar test at 5 F to the first test paper I reviewed, similar results. Additional information was taken. They showed that the oil filter was bypassed with all oils for up to 150 seconds with the thickest 15W-40 oil. This was because of the relief valve opening from excessive oil pressures through the filter, as if the filter was clogged with particulates. (The dirty oil on the bottom of the sump gets picked up first and run through the engine without filtration. I always wondered if oil bypassed the filter on start-up.) They recommended a better SAE test correlation for oils reaching wear prone areas as the upper engine in cool, rather then cold testing. More testing at realistic cool start-up weather needs to be studied. aehaas
 
Joined
Sep 28, 2002
Messages
39,802
Location
Pottstown, PA
quote:
(impossible according to the constant volume pump theory)
Not at all. A pump can be of low enough volume and the oil of high enough viscosity to merely spin around in an open relief setting. In fact, I would feel totally assured that this is the case with the differences between the lower flowing/higher viscosity fluids mentioned in the quoted studies. In extreme cold conditions with thicker mineral based oils ...for that matter with all mineral based oils regardless of specified viscosity this is typically the case. Even our moderately cold climate here in southeastern PA used to yield the (pre EFI) "stalling engine" ..where a car would start and then stall repeatedly until oil pressure could be maintained. This was one of the pleasent side effects of using M1 back in the mid 70's that I noted. It was only available in a 5w-20 at that time.
 
Joined
Dec 6, 2003
Messages
7,409
Location
Austin, TX
quote:
Originally posted by AEHaas: Low Temperature Oil Pumpability in Emission Controlled Diesel Engines, Mc Geehan et al: At 4 F it took 100 seconds to get up to pressure at the camshaft using a 15W-40 oil, 60 seconds for a 10W-30 oil and 40 seconds for a 5W-40 synthetic oil. The others was mineral oils, all were SJ rated. The final pressure was 10 PSI higher for the synthetic, “thinner” oil. The sequence was 500 RPM x 5 sec., then start, then idle at 1,200 RPM. The 15W-40 oil had zero pressure at the camshaft for 90 sec. The oil only took 8 sec. to get pressure into the main oil gallery. (? 1 - 2 sec to show pressure at the oil filter where the sender is usually located). The oil flow deficiency is from oil vortex formation in the pump and gelation. (If we extrapolate that the oil is half as thick at 40 F then according to some people you should get 1/2 the time lapses as recorded in this study. Also, if the oil is moving this slow (impossible according to the constant volume pump theory)
It gets down to 4F in Sarasota? [Eek!] [Big Grin] Some points: From 4F to 40F the typical 15w40 will be roughly 4-5 times less viscous. Even with a positive displavement pump, if the oil galleries are drained, they have to be refilled. I think you're assuming that lack of noticeable oil flow implies the engine is deprived of all hydrodynamic lubrication. And in another study: Engine Oil Effects on the Friction and Emissions of a Light-Duty, 2.2L Direct-Injection-Diesel Engine Guntram Lechner, Alexander Knafl, and Dennis Assanis, et al "For low speed and low load and mid speed and mid load cycles, the 5W-30 oils outperform the 5W-20 and the 10W-40 oils on Fuel Consumption (g/kWh)" One also has to be careful that the results are statistically significant, not just lower or higher. [ February 23, 2005, 07:37 PM: Message edited by: 427Z06 ]
 
Joined
May 1, 2003
Messages
9,448
Location
USA
First of this should be in your exsisting thread on this topic not a new thread! I happen to live in a state that gets down as low as -30F from time to time! I have tested Redline 5W40 down to -18F and had no I repeat no oil starvation issues at all. I started on first crank and ran quite the whole time. Not once was their any oil related noise. The light aircraft I learned to fly on ran 20W50 and 10W40. They were air cooled and were outside a lot waiting for the next student. While they had a tanice heating system on them that does not help first thing in the morning. We had to have full oil presure within 30 Sec. or we had to shut them down! Not once in 4 year in the university flight program did I ever have to shut down due to oil pressure. I flew in -20F weather at ground level. This is in engines designed in the 1920-1940's running dino oil!The turbines are a different story. My Mothers 03 Tundra has M1 10W30 in it and it has full oil presure within 8 seconds at -18F I timed it my self! My Dodge had full oil pressure in 13 seconds. Vechiles with mechanical oil pressure guages and no buffering will show positive oil pressure while cranking! All vechiles show positive pressure one the engine is running. The studies you cited were in some cases not even useing fully formulated oils and must be really old. Very few good conventional oils use a group I oil base stock any more. Once you more up into GII, GII+, and GIII you do not have much wax left to crystalize! Chevron,Havoline,Mobil all use group II,II+,or III for most of their dino base stock! Once you get into the modern 5W40 like Rotella,Delo,Redline, M1 TSUV,Castrol,Amsoil Delvac-1 or 0W40 like M1 and Esso XD-3 what wax is their??? How much longer do you tink it takes for a 0W40 to pump then a 0W30? How much longer does a 5W40 take then a 5W30 or a 5W20? You can also hear the change in the engines pitch once the oil pressure is up and flowing completly and it is usaly about 1-2 sec. after the oil presure has peaked. Again I think you need to do some hands on with a real engine, fully formulated oil and a freezer. You can turn the oil pump on a small block with out even starting it. This would allow you to time how long it takes for positive pressure to reach each part. The diesel studies you cited are about as useful to 90% of the member here as my light aircraft observations. Where are all the gasoline UOA of vechiles runing 5W40,0W40,15W40,10W40,10W30,5W30,5W50,10W60 that show oil starvation or excessive wear for that vechile and engine type etc???? Where are they???? They do not exsist becasue it is not a problem. Anyone that puts a 15W40 in and expects good flow at 4F deserves what they get!! Most sane people cut off 15W40 before winter comes unless they have a block heater etc...15W40 is not even a common weight used in cars anymore by most people. Even Castrol's 15W40 Truck Blend states clearly on the bottle that 15F is the cut off for the product!!4F and 15W40 come on!!! Real world UOA and observation just does not match your theory! To many people with 200,000-300,000 miles Toyota's that ran 20W50,10W40,15W40 etc.... Toyota used to recomend 20W50. To many BMW's with 10W60 still on the road and running great! Kia and Hydai(sp) still recomend 20W50. I belive that Merceds also still spec.'s 15W40 and 20W50 for some conditions as well. I am not saying their is anyting wrong with 20Wt. oil in applications that call for. I am not saying you should not run the thinest oil that will work in your application based on UOA and consuption. What I am saying is that your big agenda to push 0Wt and 20Wt. oils as grossly supior to all other weights of oil for all applications is flawed in my opion! Have you considered makeing a plexi-glass base plate and mounting an oilpump to it. You could then turn it at 500-5500 RPM to simulate an average engine. You could then test your 5W40 at 70F and see what happens. Youcould cool the oil or room to any temp you wanted. I would make sure to turn the oil pump within the RPM range of the engine it is intended for. [ February 24, 2005, 12:07 AM: Message edited by: JohnBrowning ]
 
Joined
May 1, 2003
Messages
9,448
Location
USA
I still think that this is like a tribology "Roseta Stone" and until we have something better published refureing it from a reliable source I think this preety much sums it up! Three Exxon Researchers found that a minimum HTHS of about 2.8 mPA.s was the MINIMUM HTHS viscosity needed for normal wear, with the higher the HTHS being better for minimum wear. IN general, the higher the viscosity, the greater the HTHS. For example, in a fleet of taxicabs using a GM 4.3L V6 engine, if the HTHS was 2.35, the startup film was 0.097um and 2.56 um at running; if the HTHS was 2.98, cP, the Startup oil film thickness was 1.231 um while the running film thickness was 3.22 um. In Dynomometer wear tests using four GM 3.8L engines, the wear mass of a connecting rod bearing was as follows: HTHS 2.1 mass loss (gm.) - 190 HTHS 3.2 mass loss (gm.) - 28 For "mains" bearings: HTHS 2.1 mass loss (gm.) - 150 HTHS 3.2 mass loss (gm.) - 40 A jump in HTHS by about +1.5 results in approximately 1/5 the wear. Now this relationship is not linear and flattens as one nears a 40+ weight oil. I should also mention that this test showed little differences in wear between a high quality 5W20 and a 10W30 for oils of close HTHS. For example, The average wear of one of the 3.8L V6's showed a total wear of the Connecting Rod bearings as 48.4 grams for the 5W20 verses 44.3 grams for the 10W30. For a 10W40 oil, the wear was 39 grams!!!
 
Joined
Apr 25, 2004
Messages
507
Location
Tennessee
I think you guys need to lighten up a little on Dr. Haas. He came here because he has a passion for oil. He has given us more references to read than everyone else put together. If you have a problem with test results from references that Dr. Haas has quoted, don't blame him. He's just the messenger. I don't always agree with Dr. Haas' conclusions and may debate him about it. But lets keep it civil. I'm sure he is also learning here, as all of us do. Having said that, I find the low temperature pumpability information fascinating. I agree that 100 seconds sounds like a long time, and other engines will have different times. But the interesting thing is the relative difference between 15w40, 10w30, and 5w40 oils. The synthetic oil took developed full pressure more than twice as fast as the 15w40, and 50% quicker than 10w30. I'm sure there is some truth to this. Think of all the UOAs during hard winters that show elevated iron and lead numbers. It's always blamed on cold starts. And how many of us use a thinner oil during the winter because of this? The quoted reference gives some hard numbers on this. Thank you, Dr. Haas.
 

AEHaas

Thread starter
Joined
Jan 9, 2005
Messages
1,452
Location
Sarasota, Florida
The SAE chooses what papers will be presented at a Congress. I once reviewed a paper in a negative manor and questioned the reason for publication. I learned something that day, that papers are SELECTED for a reason. The paper I "bashed" had a very important message. What I learned that was more important, is that any paper, when picked for publication has something to offer. It is up to us readers to gain knowledge if we are able to do so. Read as much as you can then you can make a more educated decision in the end. We do not have to agree but we should be able to defend our positions. Raw observations have meaning as well. 'You changed oil brands of the same exact viscosity characteristics. The engine's mechanical noises diminished. That means something to me. My wife sometimes asks me why I waste time reviewing articles for people who do not appreciate the information. After all, I really do the research for my own edification. I happen to know there are people out there who are thankful so I keep going. aehaas
 
Joined
Mar 20, 2004
Messages
4,378
Location
Camas, WA
Is the mass loss grams (gm) or milligrams (mg) ? The results need to be reposted some of the other 'thin oil' threads.
 
Joined
Dec 9, 2004
Messages
242
Location
Connecticut
quote:
Originally posted by C4Dave: I think you guys need to lighten up a little on Dr. Haas. He came here because he has a passion for oil. He has given us more references to read than everyone else put together. If you have a problem with test results from references that Dr. Haas has quoted, don't blame him. He's just the messenger. I don't always agree with Dr. Haas' conclusions and may debate him about it. But lets keep it civil. I'm sure he is also learning here, as all of us do. Having said that, I find the low temperature pumpability information fascinating. I agree that 100 seconds sounds like a long time, and other engines will have different times. But the interesting thing is the relative difference between 15w40, 10w30, and 5w40 oils. The synthetic oil took developed full pressure more than twice as fast as the 15w40, and 50% quicker than 10w30. I'm sure there is some truth to this. Think of all the UOAs during hard winters that show elevated iron and lead numbers. It's always blamed on cold starts. And how many of us use a thinner oil during the winter because of this? The quoted reference gives some hard numbers on this. Thank you, Dr. Haas.
I'm with you on this Dave,I think we can all agree to disagree on topics and open discussion is what this is all about,did the Dr come here and shout out to all gather round for the real deal with engine's and engine oil????No,someone asked him to visit and talk about "his" studies and experiences with oil over what 30 years??? I have found his information interesting and educational,the pure unadulterated truth,of course not!!! The Dr gave his reccomendations as to the way he see's it as do all the "guru's here do and for that I thank you all.. [HAIL 2 U!]
 
Joined
Sep 28, 2002
Messages
39,802
Location
Pottstown, PA
Well, I tend to ...the word isn't quite suspect ..but I often look at some of these papers as where they "lead" me. Not all data is simply presented FWIW in revelation ..it has a purpose that may extend beyond its apparent intent. They may also infer certain things that are then assumed to be "truth". Research is funded for the purpose of finding a desired result (in most cases). That often leads to finding that given result ...or the absense of data that detracts from that given desired result. You merely tune the test battery to avoid the unfavorable outcomes. The yin to the yan never comes into view. If the research is on time with current schools of thought (which are at times like herding cattle ..they kinda follow the leader that starts moving in a given direction) then it is granted "weight" and assumed validity. That all being said, I don't discount the advantages of lighter weight lubricants in the instances that you quote. One must comment that these instances (start up, exteme cold, etc.) are but one dimension to a much larger construct and cannot be taken blindly as a panecea for everything under the sun in terms of superior lubrication. One would reason that if diesel engines could benefit in any measurable costs of operation with the use of lighter weight oil ..that they would use them. They don't ..this is in spite of alleged bona fide data like the quoted text. The sensible conclusion would be that this issue, although having some effect, has little impact on typical diesel operation where other factors trump exteme cold start up conditions. These series of papers are geared towards proving the assertion that lighter weight oils are superior to heavier weight oils. I don't think that anyone, within certain limitations, would disagree with that. As the resilience of lighter weight oils is improved through advancing technologies and refining processes ..we may see further practical applications for them ..or have our engines evolve to making proper use of them possible if some plateu is reached (for example adopting the NASCAR high volume/low pressure theory). I think you're creating the semon too far in advance of the practical reality. Although ...if you do publish a book ..it might actually be "on time" by the time it hits the presses ...or you could be considered a man "well ahead of his time". (this is not meant to be a slam/insult) and, yes, in spite of my not agreeing with you on what you extract from these publications ..I do enjoy challenging their findings ...so don't stop. [Smile]
 
Joined
Dec 12, 2004
Messages
83
Location
Southern U.S.
quote:
Originally posted by AEHaas: Fuel Efficient Lubricant Formulations for Passenger Cars or HD Trucks, Benard et al: Friction I think they are referring to the total effort required to move the parts, which would include "friction" in the usual sense (bad because of wear), plus the work done to push the oil around, or to move the parts around within the oil (bad because it burns more gas). using a 50 wt oil decreased with less engine speed. Because the dominant contributor to the total drag is this pushing around of the oil. Boundary lubrication is negligible. In other words, the hydrodynamic mode is dominant. In other words, the parts swim safely within a sea of oil, the metal parts separated. This is confirmed by the lack of effectiveness of friction modifiers. They are not being used because the parts are not squeezed that tightly together. This confirmation they cite I see as evidence that the modifiers are less needed: the bulk properties of the oil are keeping the parts separated. This is the mode I desire. With a 20 wt oil friction decreases with increasing speed. An explanation that comes to mind is that here, the dominant contributor, initially, is actually "friction" (the bad kind), until the oil films build up in thickness with increasing speed. This has been explained (by someone else) elsewhere here. Friction modifiers have an important role. Because the parts are being squeezed together to minimum separation (of molecular proportions?) Here, "friction modifiers have an important role" means "friction modifiers are needed", which means "in this case the bulk properties of the oil are inadequate to float the parts apart". My non-expert view is this: that whenever the oil film is this thin, you risk running on a paste of polishing compound whose abrasive particles are all of those wear metals that are too small to be removed by the filter. Hydrodynamic lubrication increases with increasing engine speed. And only then do the parts float in the desired bulk-oil bath. This is what the above statement means.
I don't know the vocabulary, but this is the way I read the above passage. I hope this is helpful to other non-experts. Constructive criticism is Good. If AEHaas *is* writing a book, we are helping him.
 
Joined
May 1, 2003
Messages
9,448
Location
USA
I want to make sure that you realise that while I disagree 100% with the clonclusion AEHass has put forward I am not being rude or anti-civil!! I am useing the same tone I would use with anyone else. So please do not confuse disagreement with anger or rudeness. I would also invite people to look at the recently posted 4 UOA of a Duramax Light Duty Diesel. It has lower wear numbers then some gassers running 8000 miles oil change intervals and has been run on 15W40-5W40. The vechile is in Ohio so it see's a few cold days much more so then in Sarasota Fl. You will note that these low wear numbers could not be produced if cavitation or oil starvation were issues! I also want to bring up again the lack of significant amounts of wax in GII,GII+, GIII and GIV and GV oils. GI base stocks are not the primary basestock anymore. This is especialy true with a lot of modern 5W40,15W40,0W40,10W60 oils! SO the whole premise of wax crystal forming is really greatly reduced. We also do not see a lot of 15W40 or 10W40 used by most car owners anymore. No one is giveing him a hard time. If someone did not welcome coment even negative then they would not post. Disagreement offers room for growth. Disagreement also exposes weak spots in an arguement and allows the author to go back and re-think his argument to better it for future debate! I also offered constructive methods of testing his theory under controled conditions that would be easy to document. Surely you would not want your docter to operate on you with no real world experince after jsut reading a book! You would not want you mechanic to simply read a paper and then with no experince tear into your engine! That is one thing I really enjoyed about BOB! He would perform real world expermints to see if a theory was right or wrong.
 
Joined
Feb 21, 2004
Messages
2,149
Location
USA
AEHaas does bring out some interesting points and tries to reason his view on THIN oil. John your a season mechanic who has and seen heavy duty engines and things many normal dudes don't experience. I respect your points and see where you are coming from. When guy's like you sees and experience things like that, your tend be conservative in your view of thicker oil(cause of engine proctection). Them Aussie luv that thick oil cause of their driving conditions. Tuff act to follow and to express your point of view where others haven't experience. I tend to favor thicker oil myself, it's just in the nature cause it protects the engine and that's the bottom line.
 
Joined
May 30, 2003
Messages
5,117
Location
Airlie Beach Australia
Hi, Mamala Bay - actually the most popular selling synthetic here is M1 5w-50 (15w-50 is not sold here retail) and the most popular HDEO is of course a mineral 15w-40 New Euro cars are delivered here with their Euro factory fill intact - either a 0w-40 or a 5w-40 and they stay on it "for life" via their dealers These two viscosity lubricants are gradually becoming our "standard" fare! Many independent workshops in OZ use an HDEO 15w-40 as their "in everything" service fill Our new Fords and Holdens (IL6,V6and V8) are sold with a 10w-30 as a factory fill Very high viscosity oils such as 25w-50 or higher are purchased for use in "oil burners" etc. I believe that the biggest selling oil here is Castrol's GTX 15w(or20W)-50 - it is sold on discounting in Supermarkets and etc Regards Doug
 
Joined
May 1, 2003
Messages
9,448
Location
USA
Yes, It is no secret that I favor thicker oils then most. I do think though that their is a place for ever oil. I think that the old method of selecting an oil based on ambient temp. still has some merit! I also acknoldge that modern multiviscositys oils are capable of some amazeing wide viscosity oils. I would even agree that once can use the thinest oil that "UOA" shows will work well in your engine. Now I do worry that many people do not realise that if you decide to use the thinest oil that will safely work in your application you do open yourself to a greater margin of risk! Mamalabay, I am a big promoter of M1 15W50,15W40,5W40 and even 0W40 in more and more cases!!! I do not though think I could ever put 25W70 in my engine anymore then I could put 0W20 in!!! My problem with AEHass is not personel in nature at all. I have just never seen any evidence of what he claims unless someone was running 10W40 or 20W50 dino in extreme winter conditions! My M1 5W40 is about as thick as milk and my 0W40 is even thinner Terry calls it a 0W30! Tell me any problem in OZ with all those engines running 25W70??? [Cheers!]
 
Joined
Aug 20, 2003
Messages
283
Location
uk
John, RE ambient temperature although the sump temperature may increase, will the operating temperature within engine actually follow as controlled by water temperature. If you step on gas the oil temp. will rise rapidly and thickness of oil may be more dependant upon use rather than ambients. I agree that going below a 40 is taking you closer to the edge especially when the car is used hard. However there appears to be a oil self regulating system thinner stays thicker and thicker with additional temp. runs thinner. The more you push the oil the more adaptive it becomes perhaps even working with your engine in that if better film in bores with thin oil, the higher viscosity generates a bit additional temp. and thins to provide additional protection. However the cam does not experience such increases in temperature and may still require a thicker oil for protection. Therefore it becomes a balancing act between the needs of bore, bearings and cam to provide the right oil depending upon use. Having established these requirements then cold flow can be considered. Perhaps this is why a 5W oil may work better overall than a 0W as the oil has a better balance between cold and hot requirements. The answer may be better warm up as Doug has mentioned elsewhere rather than just a thinner oil. If you wish to drive a car very hard then increasing HTHS via esters appears to be a good investment re protection and probably with Redline etc you can drop a viscosity. Keep going aehaas and John etc as makes great reading and very thought provoking. Has cavitation ever been an issue with 20W50 oils from days gone past, as I have never noticed this aspect being of any concern and for modern engines this must be considered when specifying the required oil. I can see there would be perhaps a problem if using a thicker oil than specified but normally only used in high temp. race applications or ambient temperature extremes. The other aspect on oil reaching the parts on start up is whether polar esters have a major part to play? Gary, Interesting point on stalling as I still use carbs and even at 0c in UK with 0W40 there is a tendancy to try to stall with a cold start. This is more apparent in morning but not in evening despite fairly even ambient during day.
 
Joined
Sep 28, 2002
Messages
39,802
Location
Pottstown, PA
quote:
Gary, Interesting point on stalling as I still use carbs and even at 0c in UK with 0W40 there is a tendancy to try to stall with a cold start. This is more apparent in morning but not in evening despite fairly even ambient during day.
I imagine that you mean the "first start of the day" after an overnight cooling ..as oppose to starting it 8 hours later after your run to work (projecting on my part, admittedly)?? Add radiant heat of the sun to retart cooling ...voila~!. I think it's more a function of fuel management where the carbed engine just has no power to sustain itself and any drag/friction kills it. You probably would not experience this event with a 5w-20 or 0w-30 synth. This could only be "ideal" for that event and other operating considerations may take precedence.
 
Joined
Aug 20, 2003
Messages
283
Location
uk
Gary, Basically but devoid of sun, but a residue of heat in oil especially with a run during day. However raise overnight temp slightly and any idle drop disappears. Mind you Holley automatic chokes are not that sophisticated, and not a particular problem in mild south UK.
 
Top