Thread: Common rail explained

Originally Posted by uninformed

since they are making more hp per cc, what about the stresses on their components and their long term durability?

Serge I can only comment on the last 2.4 Tdci engine I had apart, due to a failed piston oil jet, the rest of the engine including all the other 3 cylinder bores, pistons, crankshaft and bearings, camshafts and followers/ rocker arms etc etc were all AS NEW at 137,000km. I would say had the lack of lubrication to number 1 cylinder bore not occurred, then this engine would have the same lifespan as a Tdi or even a Td5. Structurally, and materials quality I could say this with confidence.

JC

Originally Posted by uninformed

since they are making more hp per cc, what about the stresses on their components and their long term durability?

Certainly they are more highly stressed, however materials science, manufacturing methods and FEA/FEM computer optimisation have progressed vastly since mechanical injection diesels were designed.

However, for the size of engines that we are talking about, it should be pointed out that the industry regards them as "toy" engines that are essentially throwaway items.

Originally Posted by PAT303

John,aka Bush65 steady up tiger.What many people believe is modern vehicles are not suitable for outback travel which is wrong,look at Brians post above,funny I've never had constant issue's and I live and work in outback Oz,my L322 never had any trouble and they are loaded with electrics,remember also that modern engines stop because of the self protect systems built into them,like water sensors in the filter and airbox,in a way they are better as the motor stops before damage happens.It has been posted on many forums about complete fuel system changes on modern vehicles,thats warranty,if you could buy a modern mechanical injection vehicle like an 80's county you would still have all the fuel system replaced,thats the way it works.Like all new technology people who don't understand it or don't like it will critisise it,look at the RR in 1970 with coils,or when it came out with an auto,if we all thought like that we would still be driving series 3's. Pat

Steady up yourself Pat.

I don't have time to look at more than a small number of forums here, and withing those forums I only open a few threads.

However, from what I have seen you would appear to be the most vocal critic of the reliability of modern vehicle technology.

I happen to believe, based upon my observation, that these modern vehicles are more reliable than you claim.

I find it laughable that in this thread you are taking an opposite stance and are slapping down others for questioning modern technology.

Originally Posted by uninformed

since they are making more hp per cc, what about the stresses on their components and their long term durability?

In general there should be no greater increase in the stresses to affect durability.

The design process of mechanical components is unchanged. if the load increases, the size of the component needs to be chosen to keep stress within acceptable limits.

To obtain higher performance from a CRD (or any other direct injection diesel), unlike a petrol engine, increasing the engine speed substantially is impractical. So the only way is to increase the BMEP (brake mean effective pressure). ECU's and brilliant tuners, can't walk on water, nor can they change the laws of physics.

The high combustion pressures and temperatures are mainly a headache for the piston design. This is why there has been a radical change in the design of pistons in, for example line haul truck engines.

If you do a search you should find information on
Mahle topweld steel pistons
Federal Mogul monosteel and durabowl
and Monotherm pistons

With conventional one piece pistons, manufacturing and material advances include
Anodising and ceramic coating
SCFR, Squeeze Cast Fiber Reinforced using ceramic fibres.

Ceramic fibers have a polycrystalline structure consisting of Alumina, Zirconia, Carbon, Boron nitrate, Boron carbide and Silicon carbide.

SAE paper 910460 (The Effects of Ceramic Coatings on Diesel Engine Performance and Exhaust Emissions, 1991, by Assani, Wiese, Schwarz, and Bryzik) reports a variety of tests using plasma-sprayed zirconia-coated and insulated pistons with thicknesses of 0.5 and 1.0mm (.020 and .040 in.). The thinner ceramic coating generally resulted in improved performance over a noncoated piston due to the reduced heat loss. Fuel efficiency gains with the thinner-coated test pistons produced 10% higher thermal efficiency and 9% higher BMEP and torque than an uncoated piston with the engine running at 1000rpm. The thicker 1mm (.040in.) coated piston exhibited inferior performance to the noncoated piston. In addition, the emissions characteristics of the insulated engines at full load showed a reduction in CO (carbon monoxide) levels of between 30% and 60%, unburned HC (hydrocarbons) levels that were 35% to 40% lower, and NOx (nitric oxide) concentrations that were between 10% and 30% lower due to the changed nature of the combustion in the insulated engines compared to a non-insulated model. However, volumetric efficiencies for the ceramic-coated piston engine were lower than those of a noncoated piston engine because of the hotter cylinder temperatures and residual gases that decrease the density of the inducted air.

re these exotic piston and liner materials, I had some involvment in testing of OS .46 FX model aircraft engines (glowplug) in the 90's using ceramic 'plasma' coated pistons and liners (made in Russia)

Included stressing the engines to the max by running on minimum (or no) oil, props too small & too large for engine, and purposely ingesting dirt and grit into the engines, and blocking off cooling fins.

My brief was to 'destroy' one, The pistons and liners passed all tests and were indestructible, showing no signs of wear whatsoever, even after a year of sustained abuse, could not say the same for the bottom ends, The cost was too expensive and did not go into production, but I think they do now have ceramic bearings for the engines.

IMO The technology works, and I think that is in the future of Automotive engines

Originally Posted by Bush65

Steady up yourself Pat.

I don't have time to look at more than a small number of forums here, and withing those forums I only open a few threads.

However, from what I have seen you would appear to be the most vocal critic of the reliability of modern vehicle technology.

I happen to believe, based upon my observation, that these modern vehicles are more reliable than you claim.

I find it laughable that in this thread you are taking an opposite stance and are slapping down others for questioning modern technology.

I don't like modern pointless gizmo's that are sold as technology,modern drivetrains on the other hand are great bits of kit,having manufactuers refuse to release software so we can diagnose issue's is the biggest complaint we have in the trade as fault finding is very easy with it but very difficult without it. Pat

Originally Posted by uninformed

since they are making more hp per cc, what about the stresses on their components and their long term durability?

Non event Serg. Pat

Originally Posted by isuzurover

Certainly they are more highly stressed, however materials science, manufacturing methods and FEA/FEM computer optimisation have progressed vastly since mechanical injection diesels were designed.

This is what Im thinking, but in my usual sinical way, im thinking it allows them to design/build things closer to the edge. Why, well $$$ is the only reason. If you can make something last JUST long enough, usually it can be done with either less material or a lesser material..........

I would hope the Tdci last longer than the Tdi I and others have had