Other than contacting a thermostat manufacturer does anyone know how I can modify a mercedes 123 thermostat myself to open at 240-250 degrees F. I can use heated oil to check calibration changes.

I wish to try an experiment on the effect of elevated block running temperatures on fuel milage. Any downside on the cast iron 123 engines anyone can think of?

No it will not boil over as high temperature anti freezes have been around for some years now.. I just want to do a test so any problems with the high temp anti freeze I am aware of can be discounted as it is only a test. The boil point of high temperature anti freeze is well above where I want to examine.

One secret to higher fuel milage may be the elevated temperature improving combustion or efficiency. The only way to truly know is to actually test the ideal.

As many may or may not be aware this general area of any possibility of increasing fuel milage has been with me for a time. Another concern is why the turbo engines really give better fuel milage. Especially if there is really oxygen left over after the burn in all areas of the cyinders on naturally aspired engines.

This has also greatly concerned me. Is it just the additional turbulance effect of the blower? I cannot quite visualise why this should be if oxygen availability is not the reason.

Also to make any improvement over the factories original design. Entails working on or enhancement of the combustion process and function to increase efficiency in these archiac designs. I have reluctantly decided some time ago.

There is some component or benifit to higher temperature air intake on some indirect diesels. Since the oxygen equivelant is less something else is going on. It almost seems that a hotter cylinder enviroment in an indirect diesel might be benificial.

There is a chance mercedes knew some of this but for many reasons with the technology of the times could not or would not introduce it. There are more than a few issues with higher temperature coolant systems I can think of safety wise. Still other than increasing milage there just might be other benifits. Plus some downsides as well of course.

Things like the efficiency of the cars radiator improving because of higher temperature gradients to the ambient air being present. The btus transfer rate per unit volume of the higher temperature anti freeze will be smaller I suspect than normal anti freeze.

Yet this has not been an issue with it that I was aware of. So any gain in transfer efficiency from fluid to air at the radiator from the increased temperature differential alone could be just a useful gain.. Those owning 602 or 603 engines are out of luck..

You'll need to find the right alloy of waxes or silicone (?) to work at that range.

The hotter you run it the tighter the pistons will get, as aluminum has about 2x the coefficient of thermal expansion (CTE) as steel/iron.

The higher the compression ratio, the higher the thermal efficiency. The turbo engines have both higher static (swept vs combustion chamber) ratio and add DYNAMIC compression ratio by forcing in extra air.

Glycols have poor heat capacity, but as you noted the standard ratio of 50:50 with water--which has fantastic heat capacity--will carry more heat per volume than a pure-glycol (non-aqueous proplyene glycol, as from Evans?). But you also noted greater heat rejection for the identical radiator/fan because of the higher delta T. A wash, perhaps. I've never seen a vehicle with enough radiator/fan to reduce the radiator outlet temperature to ambient--it's pretty much impossible with a cross-flow heat exhanger.

__________________
James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k

I have been wondering the same thing since our conversation the other day. My car has been operating at 70 degrees celius which is lower than the typical 80-85 degrees. I am thinking the lower operating temperature is part of the reason I'm experiencing lower fuel milage. Either way I was wanting to replace the thermostat so if one w/ a higher opening temperature exists I would definately like to know before I go replacing it.

As you are unable to articulate the scientific reason and rational behind your theory of increased operating temps effecting fuel economy increase and it seems extremely unlikely that you will ever be capable of actually in practice verifiably doing so, 602 and 603 engine operators will have to remain satisfied with the mere 30% - 50% fuel economy increases not to mention the overall performance increase!

It is interesting that with the emphasis on fuel economy over the last 30-40 years that if it was as simple as running engines at higher operating temps to realize any significant fuel economy increase one would think every vehicle would have evolved to sport a high heat operation engine!

Boisebenz, A really good response to my questions. Efficiency increasing may equalise things a little. The burn may be different enough..

The radiator would seek ambient temperatures of course but since this is not reached in stock configuration I was only interested in the thermal tranfer being adaquate to support the system with the evans coolant. If an efficiency gain is not present somewhere it will fail with the evans coolant I suspect.

Since you are aware of the evans product I feel it is only good for the experiment as I believe there have been product issues. Unless perhaps they have dealt with them by now. You probably know substantially more than I do in that area.

I though like you perhaps might conclude. The best and easiest possibility of getting an elevated thermostat would most likely depend on the makers of the normal thermostat. Other than that we could be reduced to an external control circuit. Basically totally manual with a control shaft out the neck to some form of hybrid electrical/electronic control. This would enable operator control of the set point of the opening of the thermostat. A much bettter approach perhaps both during the experimental phase and if the ideal becomes practical.

I think there is enough evidence from other things I have observed to at least try to make it happen. There are just too many unknowns to speculate about. What a test like this would show is almost anyones guess. It's rough enough to deal with the knowns.

At least the early stage tests seem very cheap and easy to set up. If any positive results occured that were worthwhile in nature would then lead to further exploration. If some encumberance was too impractical to work around then quitting the experiment would be easy.

There are just too many casual observations and experience with other diesel indirect injection engines like the volkswagon to ignore an attempt.Something seems to be going on at higher block temperatures that is difficult to rationalise with some of them. Or at least to a simple person like myself.

Whenever I quietly start rolling this around in my mind the only thing I can conclude is that it may provide both suprises and effects in unsuspected areas. I understand your logic yet it may still produce some effects that we might have a hard time reducing to logic at this point.

My thoughts will clear up somewhat over the next few days hopefully with members input. Right now I can only wonder why someone else has not explored this area in depth on these engines sparing me the mental agony.

I assumed everything there was to know about internal combustion engines was well known. So they were basically at the end of their development cycle.

For example if you lower the block temperature fifty degrees below operational design temperature. Fuel milage really declines. If logically say it were to continue increasing with 50 degrees elevation above normal design. Providing some design paremeter was not seriously exceeded. The efficiency and resultant fuel milage may increase. Or possibly decline in a piston tightning situation as you suggest as a possibility. It would be nice to hope a worthwile milage increase was just sitting there. I have not reached that point yet. All i really am pretty sure of is something unknown at present may be lurking there.

I guess I could use a torque wrench to find the turning torque of the same engine with a normal thermostat after a good warmup to operational temp. Remove the thermostat and install the elevated example. Rewarm the engine fully and recheck the torque required to turn the crank as soon as shut down . Same identical drag does not totally really prove there is no issue. Just indicates destruction is not certain perhaps.

If nothing else the experiment could be entertaining.

There is a yes and no to your Idea.
Like the member runing at 70 degrees C; If he changes to Thermostat that opens at a higher degree setting he will see some better Fuel Milage and less Carbon deposits.
He also has a good case for checking his actual Coolant Temp with Thermometer to see if his Gauge/Sending unit is working OK.

More that one member has reported better mileage after replacing a Thermostat that was stuck open.
I had the same situation on my Volvo and I clearly was not burning my Fuel well as I had hazy gray smoke; a result of incomplet combustion sticking my Pistonrings.

But, there is a limit to how much Fuel Milage you can gain by changing the Thermostat to a higher opening temp one.
The problem is how much is too much. Without a good accurate way to monitor your results you are taking a chance of ruining your Engine.

A ruined Engine is not economical.

If it was me I would not raise the temp higher than the recommended safe temp.

I believe I read on the forum 90 something degree C Thermostats used to be available; but are not now.

Another way to control the temp would be to convert to an Electric Coolant Fan that has an adjustable Temp Switch on it.
This would also be good for testing because you could start of at a normal temp and work your way higher and record the Mileage you get at various temps.

Another thing to consider is that if the Coolat Temp gets higher the Crankcase Oil temp is also going to go up.

__________________
84 300D, 82 Volvo 244Gl Diesel

In my opinion this effect if you will is not applicable to all engines. It is very early to even attempt to reduce it to scientific terms. Even if it were practical manufactures would not embrace it because of liability issues.

For a few years now the requirement for oils in many four cylinder engines has been more demanding. They are running hotter. The reasons could be many yet may be only to increase engine durability. With gas cars you do not also want to get into not only any form of uncontrollable pre detonation. But too short a burn either perhaps.

They no longer make engine designs that may respond to this serious elevation I am reffering to. I am still waiting to read somewhere or have an explanation in a scientific format or otherwise explain the thermal increase of efficiency that occurs with volkwagon indirect non tdi engines on hot days. The same does not occur on the tdi engines for practical purposes.

Although dissimular in many ways this is just an attempt to see if elevated block temperature has a positive effect as well. There is something there that I have never heard explained clearly or adaquatly. I have also seen positive evidence something is happening.

Can it be duplicated or a portion of it in mercedes vintage diesels? I do not know. Is it worth the effort of having a look? Who really knows except the cost of the examination potentially is very cheap.

If money where no object is an entirely different proposition. Things that are arrived at have to be conditional as easily affordable to implement for and by the site members.

602 and 603 engines probably should not be subject to operation at elevated temperatures. The additional aluminum head expansion compared to the block would be increased. They already seem to have a higher efficiency over the cast iron engines anyways. I not only do agree with your posting on the 602 and 603 but suspect even if you risked the head by increasing the operating temperature of that engine there may be no difference anyways.

The scientific rational can wait for later. No matter who develops it. At present that is like putting the horse before the cart. What transpires if anything during testing is what we will have to scientifically explain. If nothing then there is nothing to explain. How can it be otherwise?

We are not even sure something is there yet. I look at all the possible causes of the known increase on those volkswagons and just have a long list of probabilities. I even watched for volkswagon to mention it. As soon as it is mentioned by someone outside the corporation all seems to go very quiet instead.

There have been unexplaned inconsistantcies for well over ten years now. For example the famed tdi engine generates almost marginal heat from the heater in comparison to the indirect engine. And the heat is slow to kick in by comparison with the earlier engine. Volkswagon dealers were told it was because the engine was so efficient it did not generate heat. Of course that was an obvious smoke screen.

I think the tdi engine was a mercedes design manufactured under licence to volkswagon. The old indirect engine perhaps a volkswagon in house design. Maybe not.

These exercises are just that. To probe into areas hoping to find things. Nothing more really. If we do not attempt the experiment can anyone guarantee there is nothing different? It is so easy not to try or originate approaches that seem abstract initially.

No I certainly am not capable of sitting here and projecting a quasi scientific answer or otherwise suggestion of why an unknown at this moment might actually exist. If it were possible I think it would have already been done.

To rationalise an effect has been charactaristicly done after the discovery. The laws of thermodynamics for instance are not going to be re written. On occasion an effect occurs that turns out to be a combination of existing laws.

Abstract thought is a very bumpy road. First the strong suspicion must develop. Then the methology to get there. There is always an attempt to define logic. Many thoughts flounder and fail along the path. Ultimatly something connects or something is learnt. Cynasisim has no place.

Constant doubts certainly should be present and expressed. When I seriously start to think about something as an individual I require outside stimulation. I have to sort out incoming information from others.

This alters my thinking so I can develop possible senarios and ideals. I already know what is desired. What I do not know is if it exists. It is not a simple thing for me to balance. On top of that I have to project the ideal in a way that gets your input. I got it by the way and it helped believe it or not.

At the end failed or not it is a joint effort. If failed I assume the guilt or whatever. If it works out the event is shared by all participants. Overall few of my approaches are total failures. In the process something or other is learnt that is signifigant in itself. If anyone knows where this one will really land up I wish they would share.

Can you possibly visualise all the places I looked and rejected with out conducting any experiments. The intense personal exposure required to open a can of worms? Scientifically or otherwise I systamatically over time kept an open mind to see if there was any possible way to increase fuel milage on this archaic engine design. I did ultimatly develop one slight possibility. Do you know of anybody else that did? This was a pretty hard nut to crack from my perspective.

There are lots of forum members that are far more intelligent than myself. I know that intuitivly. I just over the long haul want to make a contribution or contributions as others do in my own way.

Never wanting to argue or really disagree with any member. At my age I still manage to take in at least some information I did not know every single day. Why at my age is beyond my simple reasoning ability. I also have a major flaw in that I really like people. Possibly because our family lives have been good with few potholes and many challenges. Or perhaps that was just the result of the wife and myself liking people. Who again really knows?

I did not read this post before posting the last one. As expressed in it and obvious there is a very important contribution in this post. I will not have to mess around with the internal thermostat system initially if this ideal works and it should.. The block temperature should be controllable with a thermostatic fan.

Mentioning the oil issue was a good ideal as well. Basically I considered it and rejected it as a probable issue. At the absolute worse I felt a one grade increase might be a good ideal in the summer.

Yes there is a risk of damage to a good engine. The resuts of the testing in my humble opinion are worth the risk. I can slowly stage the temperature upward and check for issues along the path.

To intentionally destroy or damage a sound engine does not please me in any way. It is an ethical rather than monetary issue to me. The engine is an inanimate object so that is not a particular rational though.Still it is what it is.

The test does demand a fairly sound engine though. Well tomorrow I will try to find a source of the evans anti freeze. I will probably manually try to control an electrical fan for temperature control initially. Or have a passenger do it. I will also have buy and to rig a higher reading temperature gauge up. For safety I will remove the heater hoses and loop them . The system cannot make more pressure than the cap will release.

I just do not want fluid well above the boiling point of water anywhere near me. I was burnt in an explosion years ago. Burns of any sort do not interest me at all. Kind of a paranoia thing I suppose.

Barry,
If you increase the operating temp by this amount you will damage the motor.
A 10C increase in temp doubles the rate of burn in the combustion chamber.
You will have too much pre burning.
This temp will also increase EGT's, & so you can expect burned exhaust valves & melted pistons.
At your proposed operating temperature, some of the internal surfaces of the motor in contact with the oil will be hot enough to cause thermal decomposition of the oil. The increased temp will also substantially reduce the oil lubricity.
As mentioned before the increased temp will also cause excessive piston swelling & likely seizure, If not It is likely to cause sufficient oil fuming to cause a runaway motor.
I dont know where you have got your information from, but it appears that you have made a very exaggerated prediction by extrapolating some information that a few degrees increase in temp results in an improvement in efficiency.
It is a very bad idea to attempt such a change.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Good information as I never knew that the effects of such a rise in block temperature would do so much. If a 10 c rise or about 20F in temperature causes all the above.


I originally was going to gradually increase the temperature to study any effect. From what you indicate only a very small increase in operating temp may be benificial and all that is required. Or is the engine already operating at it's upper limit? Unfortunatly I had no source of information on what was really known already. So I did not really extrapolate anything known to me .

From what you indicate is a very small relative change in block operating temperature has a pronounced effect on combustion. Is the efficiency of that combustion better?
So at least we got it right in that there is a change. These blocks are pretty robust. Is there any upside with very slightly elevated temperature. The standard thermostat is 80c? There used to be a 90 c available has been mentioned.? Is there a chance we could pick up some reasonable improvement at all in your opinion. Or do you feel it would be all downhill.

I really do not want to activly engage in anything that may prove destructive to people. Most engines of my time will operate at 100c with a good pressure system with no apparent difficulty I thought. These 123s would possibly have to employ the evans coolant to enable this. Probably not possible because of the more limited heat capacity for transfer purposes. Unless efficemcy climed substantially.

Their normal cooling system does not seem to have enough reserve capacity to deal with loading without increasing temperature because of inability to get it out of the rad quick enough .I always wondered if middle east versions had a better capacity rad.

If we could find out if the 90c thermostat really existed for these cars. Plus it was not discontinued because of engine difficulties other than perhaps easier overheating of the coolant to the point the radiators could not easily cope.

Would we have something or not in your opinion. Mercedes may be able to help as well in supplying some relavent information. Again from what you state these engines are quite touchy in their burn charactaristics in relation to block and head temperature in the background so to speak. It may answer the pronounced shift in fuel economy I observed repeatly on the volkswagon engines. I can easily understand them gaining a few degrees upper block temp on a very hot day. I just though it had to be a lot more to get the effect. They have a massive rad for the size of the diesel engine displacement as well. Would a slightly changed burn provide more efficiency perhaps actually reducing cooling needs to any extent? I wonder what mercedes mentions in their manuals about allowable thermostats. There might just be on optimum target temperature we can manage. If so it is going to be much lower than what I imagined.

Barry, sounds like an interesting experiment. Go for it! I bought a high temp thermostat made by Motorad from Autozone a few years ago. Still in the box. I'll look an see what the temp is. I think it's around 90C.

Other areas to explore to increase efficiency is dynamic timing control. Don't know how difficult it is to accomplish on our inline IP.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I used Evans NPG and then NPG +. If they have a new product, I'm not aware of it. The ONLY downside that I saw from years of use in two tracked and autocrossed gas Audis, one turbo one NA, was poor heater performance at idle in the winter--too thick to flow well. One advantage that you'll appreciate, since you don't have to bypass the heater, is that it runs at zero pressure; you drill out the cap and leave it installed. No more blown heater hoses or monovalve housings!

Watch the oil temps, perhaps with smaller electric fans? Running a 617A at 2500 for half an hour while calibrating the AC charge will get oil temps up to ~280 dF at 85 dF ambient. Use a synthetic with the right/matched viscosity AT YOUR NEW TEMPERATURE and you'll be fine. Synthetic suffers no viscosity/shear breakdown at any temperature lower than when the oil is actually on fire, according to Amsoil phone support. Synthetic will also have less volatility (fuming) at any temperature than petroleum lubricant, reducing Layback40's valid concerns of runaway.

Layback40, in many cases (typically according to the Arhennius equation) reactions procede much faster at higher temperatures. However, our diesels do not get a full fuel charge which can burn as fast as it wants. Rather it's injected continuously during the combustion cycle, so the reaction speed is controlled by the introduction of one of the reactants. Also, I THINK Barry is looking for increased CRUISE efficiency, NOT maximum power. At max power EGTs go way up, but not so at cruise. If in fact it's 10-25 Hp CRUISE he's looking at EGTs should only be around 400-600 dF--not harmful at all to valves or pistons.

For your experiment I like the idea of a "cold" thermostat at maybe 60 dC basically running wide open all the time. The temperature would then be controlled by an electric fan/louver setup, and ANALOG adjustable just with a potentiometer or other device. If you then find a "sweet spot" you could get a batch of 300 'stats made to your specs and sold for $75 each as "Mileage Master 617 (tm)"!

FWIW, I'm not just running my fingers here. I've been working on piston and jet engines for 30 years, and I'm a licensed Mechanical Engineer and a machinist/fabricator.

__________________
James Marriott
2003 Buick Regal
1983 300D (228k, frau Auto)
1996 Suburban K2500 (192k, 6.5 turbo diesel/4WD towmaster 10,000)
www.engineeringworks.biz
1987 300SDL junker 170k
1982 300SD junker, 265k

Well BoiseBenz you are a relative newcomer to our site. Everyone is a newcommer to this thread at present. I have been casually looking at many things for awhile. A member did point out that I am certainly not well versed from a scientific perspective. On the otherhand you appear to really be.. So if you could participate from time to time and keep an eye on things I am sure it would or should be appreciated by all participants.

At least up until my somewhat bizzare posts eventually rationalise to a point. This is sort of a brand new attempt to look in this area.. The simplicity of this engine tends to fool me a lot.

After getting a good nights sleep and reflecting on all the posts so far it has already changed the approach to this issue. Any help or suggestions yourself or others posters make will be more than welcome by everyone I hope.

The thing that has really been impressive over time is as long as non productive infighting does not arise. It never has before in the two particular other areas I spent some time and effort on by the way. All will probably benifit to some extent. I know I will.

It has to be a given at our level everyone does not know everything. Plus people will make wrong calls from time to time.I have to take credit as the raving expert in that area I suppose. Well perhaps it's better to tie down one end of the spectrum at least. Than to be stuck in the middle. You then know exactly where you stand.

I have lived with the opposite sex so long now for example I can no longer remember when I was free. In that arrangement I once again know what end of the spectrum I occupy. At the same time feeling fortunate to be there.

The beauty of those wrong calls is it brings certain things to the surface that may otherwise be overlooked at times. Personally I do not want any credit for ideals launched but instead just try to enjoy and learn from what results. Plus hope that everyone eventually benifits. It is a total non profit and non commercial effort for the common good.

We I believe tend to obviously learn things even if the end goal is not reached or practical. Everyone has a voice. I never really get out of shape when critiqued myself. It is just a part of the flow of the process and should be so. It is the personal attack type of thing that can do the destruction. It seems to so nicely obliterate the thinking process.

For example I might have unintentionally pulled someones tail when suggesting the exclusion of the aluminium head engines at this time. From previous experience we have young fellows thinking one shoe fits all in my experience. This was just suggested to deter them a litttle. The poster that may have taken offence was not one of the young fellows in my mind.

I personally would not like to see any avoidable damage occur before any risk is known or examined by hte group. We in fact can enable this to occur by inducing people to start thinking in areas that never occured to them. It is better to pre emptivly head them off or the majority of them until a lot more is known.

Time after time I mention that I am fundementally illiterate in these areas. Yet still feel with others help headway can occur over time. We are participants in a group and should welcome all insites over time. This thread is likely to be active for a very long time. Have no doubt if something practical is to occur it will take time and ongoing modifications. For all of us it is not the principal thing in life either.

Well back to subject.When I was informed potentially the ideal could result in a new volcano site. By a guy I do respect. I had to think. His thoughts indicated to me that what we may desire could be at a far more reaonable and practical temperature elevation than I percieved.If there at all. So in a way it was good news.

Try to consider we have not even done temperature scans yet to establish the current average head tempeature on these old engines. Instead it was taken as a warning by me that my thoughts might have to be changed. I expect before this is over almost every current though by many might be modified after intense examination.

I cannot go and find a 90c thermostat and do a milage comparison to the 80c thermostat at present. The time is just not there currently.

Fall is getting established here and there are too many fires to extinguish before winter arrives once again. Other than the relaxation of some time on site periodically there just is commitment and work right now. I am four thousand miles away from where I should be today.

This is retirement? Forget being concerned early in life about your retirement income level. Plan instead about how to get some time to chase your interests and dreams when you arrive there. Laying back is just a conceptual ideal if you have been busy all your life and still healthy. Maybe it's for the best yet one can entertain doubts a the same time.

I have to take the dogs out and close up the cottage so I will look forward to reading what is posted when I get back in a couple of days. We do not have internet or many other things at the cottage. This is by intent as we both do not want a duplication of our prime residence. The cottage is to get away to so even the phone remains unlisted.

There are many reasons for me posting this particular thread. Most will understand I hope. I think a great deal and have a lot of repsect for the members.Only regretting that we will never meet. Keep the insites flowing.

I think at this point the dynamic pump control is both financially beyond the average member to be for the common good. Very difficult to engineer and justify in one offs as well. Also having those pre combustion chambers would indicate to me an almost insurmountable difficulty for it to function well. The ideal shows you are thinking.

Like some of my ideals though it will not fly in my opinion. That is just my opinion remember. Pretty soon these cars will be antiques remember. Most people will want them original .Currently they are in a transition stage.

If we had to take extreme measures almost to get some gain. I personally would drop a more modern engine or power train in. As these engines over time become scarce or for all practical purposes unavailable. In the future there may be not only a few transplants but possibly an easier way to accomplsh it.

Time does change what is though. In a way we have to appreciate what they are. Time has passed them by now to some extent. On reflection it is absolutly amazing how so many are still in general service. We may be driving icons of a certain period.

Thanks for identification of a producer of the higher temp thermostat and the outlet companies name you obtained it from.

Sorry, the thermal efficiency simply doesn't exist to get that large amount of increase. Please review your science books and try again.