Piston modifications..... - PeachParts Mercedes-Benz Forum

samiam4 · #1 02-05-2003, 08:52 PM

I've been reading the group lately on engine rebuilding...

If my engine was scattered and the pistons were useable. Of courese, I could cut the upper ring land for Devis 3.17 mm ring. But, I was wondering, in the MB evolution-piston coatings have changed in 20 years.
Now, tin is not so popular due to cost and noise. So, I was thinking of maybe applying Molycote( dow chemical ptfe product), or even having someone apply a ceramic coating to the top as to reduce heat loading on the piston. Should keep the heat in the cylinder better, hence aid in starting and efficency.

Michael

leathermang · #2 02-05-2003, 09:07 PM

You are trying to second guess German engineers in a company that was making engines for 90 years before they made your car....who had millions of dollars to spend on RandD...
And you are not having problems with " heat loading of the pistons"....so don't fix what is not broken.....

Just my (old hotrodder) opinion....

lrg · #3 02-05-2003, 09:18 PM

I tend to agree. The benefit is likely to be marginal on an engine that has proven itself to be extremely reliable as is. It might be fun to contemplate but the potential benefit seems not worth the effort or cost and a slight miscalculation could actually make the reliability worse. As the old saying goes, "don't mess with success." Just my opinion.

rwthomas1 · #4 02-05-2003, 10:42 PM

Nothing against the MB engineers, they certainly did a fantastic job on most MB diesels. However..... I don't see how ceramic coatings on pistons/combustion chambers and anti-friction coatings on the skirt are going to be in any way detrimental to the engine provided tolerances are maintained to specs. The only danger I can see is if the coatings started to flake off, etc. I have read of at least one hi-po diesel build that included this technology and it seemed to work fine. While there may not be a problem with heat load in MB's, keeping more heat in the combustion chamber will have beneficial effects, more power, faster boost, etc. The big question is will it be worth the money. I say if you are into it, go for it. We never got anywhere by not trying something new. RT

leathermang · #5 02-06-2003, 01:06 AM

Michael , are your cars turbo's? Even if they are .... the increase in anything will not be measureable or feelable at the drivers seat.....and the chance the stuff won't stick the 300,000 miles your rebuild should go would not be worth spending money on....these engines are already SO close to maximum output/longivity that putting more money into getting closer to blueprinting it will be money better invested..

samiam4 · #6 02-06-2003, 12:46 PM

You guys are missing my point!

Mercedes engineeers have used the latest technologies. Now look at new production 606 engines- they don't use tin coated pistons skirts anymore. I'm going to use a coating, that is more inline with current engineering practices-not old practices.

The advantages are simple- tin is a break-in coating. The applied coating will keep oil, lower friction, and cause the skirt to run closer to zero clearance. All will improve ring wear, cylinder wear, and you should hear a huge reduction in the diesel ignition piston slap.
I can apply molycote myself with minimal cost, hence the desire. Yep, if it comes loose- it will be ugly.

Coatings are common- not only in racing, but in all the industrial diesel rebuilding too- catapilar comes to mind.

Michael

leathermang · #7 02-06-2003, 03:02 PM

Your engines, when blueprinted as close to stock as possible..., have one of the very best reliability reputations in the automotive world....

rwthomas1 · #8 02-06-2003, 03:05 PM

Always room for improvement....

RT

Wasuchi · #9 02-06-2003, 03:19 PM

They do this type of things to the heavy truck Cummins engines so they can pour more fuel to them and get 700+ hp out of them. Could do that the same way here but would the bottom end hold up? I guess if you have the money and ability to do this it could be a fun experiment. Here's a link to the how to for the Cummins. http://www.dieselinjection.net/articles.html

leathermang · #10 02-06-2003, 06:41 PM

RT, OK , I guess I am going to have to spell this out further to make my point...

The question is whether or not any improvement would acrue..... balanced by the possibility of inserting a problem and the money you are spending to place that possible problem into the equation.

What if this improvement made a 3 hp increase?
That is a very high estimate of possibilities.. but it won't hurt to use it....

On a diesel you are not changing the valve timing with a cam profile change.... so you are not going to get any additional rpm's out of the 3 hp increase.

( I am assuming that the molycoat purpose is to reduce friction ... leaving more hp at the flywheel )

If you do not acquire enough extra horsepower to warrant lowering the gearing then you are not going to experience faster acceleration out of that 3 hp...

If you do not acquire enough extra horsepower to change the overall gearing you will not experience any better fuel mileage out on the road...

so you have spent money on trying to improve something which is already legendary for reliability...something later MB's dont share with our early 1980's diesel models....

John Karsey took a VW Karman Ghia and made it faster than stock while getting 55 plus miles per gallon out of it...

He changed the cooling by going to single port heads... changed the fuel system by using 134ICT Webers on each head... he designed a cam profile which slapped the valves open faster while keeping them with less overlap....

But... until he modified the VW Transaxle ( he used a 1981 superbeatle to get a higher final gear while also putting in an overdrive final ratio..)
He did not ' realize ' the extra power with increased mileage until he changed the gears....

His cam had lowered the torque peak of the engine from about 2400 to 2100....

So he got more power, while not causing overheating ( because on a gas engine the fuel ratio really effects the heat )...(one drawback is that the increased compression his engine used required Premium Fuel to be used ) OUCH...

But these type variables are not available to us because of the efficiency of the diesel design in the first place....

So you can do it .... hopefully well enough that it does not come off...but even if you do that..what have you gained ? My opinion is that you have gained nothing... and therefor lost your money... and taken an unnecessary risk...

pretty much a slam dunk to me....

rwthomas1 · #11 02-06-2003, 07:25 PM

It is thus.... We can hypothesize about expected results of a given action literally forever. Statistical models of expected results based on tons of research can be done. The fact of the matter is we really don't know what the result will be until we TRY SOMETHING NEW!! Sure many times the predicted outcomes are proven. But sometimes, often enough, something new is discovered and thats really cool. I say if you are into it, go for it. RT

engatwork · #12 02-06-2003, 07:53 PM

If you have the means then I'd say go for it and let us know how it turns out

. You could probably crank that boost right on up there if you don't have to worry about melting the pistons. I met a fella that was running 40 pounds of boost on his hot rod intercooled turbo diesel engine from a wrecked Fed Ex truck. He made a really sweet looking late 40's (White or something like that) "big truck" running the Fed Ex truck drive train. He claimed over 600 hp at the back wheels and used it to pull his car carrier (custom car show type individual). He had some diesel "tune" shop soup it up. Sounded pretty bad

.

leathermang · #13 02-06-2003, 08:37 PM

RT, Not true at all...If and only if it can be counted on to be applied in a manner which will allow it to last as long as a stock pistion would...

Then you can compare the coefficients of friction and see what gains could possibly be expected....and see if whatever top figure possibly available would actually be of any benefit...

So we can Calculate potential... and if the max potential would not be worth the expense and adds hazards then it would not be a smart move...

I don't care what samiam3 does ....it is his car.... but I am making the argument for other younger members who arrive here with the " hot rodder spirit"... some of the things which would affect a gas engine just do not count here...and to start at the top of the food chain (the MB diesel) and try to improve it does not make economic sense....

Wasuchi · #14 02-06-2003, 09:10 PM

So, to sum it up:

Can the pistons/engine be improved?

Maybe

Is it ever going to pan out either economically or by a peformance increase?

Probably not

I wouldn't mind seeing someone try this though...... just to see what happens. I would almost bet that someone somewhere has already tried something of this nature.

rwthomas1 · #15 02-06-2003, 10:34 PM

Well I'm on the "Tom Ridge" side of the fence. Give it a whirl, ya never know. You say tomatO I say tomAto..... RT