have engine tolerances really changed

[edwardh1]

people sometimes say engines are made now with tighter (closer) tolerances. Is that really true? compared tp 1920 , yes but compared to 1985 have there been many changes in main bearing or rod bearing clearances ?
seems they were back then less than 0.001? like maybe 0.0005? are they still in that range?
and what about piston to cylinder bore clearances? changes there? or not
anyone got any real numbers?
I would think modern engine life might be due to other factors- maybe better oil and maybe better quality control

 

[lars11]

surface properties, like hardness, micro patterns, etc have been steadily improved and understood and it has actually reduced the need for break in a lot since 70s 80s.
Actual dimensional tolerances have been improved too, mainly due to automated active measuring of both tooling and work pieces. That have made all machines closer to design parameters and also cheaper, which have reduced the number of lemons, post production "#adjustments" and longer service intervals in all machines.

 

[sciphi]

Yes, they have.

As an example, GM got the cylinder dimensions precise enough on the 1.4T engines going into the Cruze that they could safely pick out random piston assemblies and be sure they'd fit.

 

[BreakerBreaker]

When you get street or shade tree mechanics talking about either "clearances" OR "tolerances," be on alert for a scam artist.

Or, a very good point was made above about how mechanical knowledge and fact from the 70s or so has changed into the 80s, again into the 90s, and I would say from the 90s to today is about the same ballpark - vehicle specific, of course.

Some late 90s cars or even mid to late 2000s cars were same architecture from the 89s or 90s, but those are only a couple or few examples. Mercedes-Benz S, Cadillac's entire line through 2004, and Lincoln Town Car, for starters.)

Thick oil, sprays on gaskets, break-in periods, oil additives primarily ZDDP, and use of premium gas (??) and etc dtc are some things almost exclusively from a by-line era, most of the time. Please note that I said most, not always.. vehicle specific will always prevail, especially on gas, and, sometimes, oil.

If you are like most, when someone gets to talking about why you are supposed to put 10W-40 or Lucas or 20W-50, in a car that maybe says 5W-30 - or 10W-30, or 5W-20! Or whatever, "No matter what the manufacturer says".. and gets to talking about "engine clearances wearing out" .. Or the "tolerance" or parts needing that thicker oil, when oil pressure and engine operation are fine.. you are probably dealing with either an idiot, or a scam artist. Or both.

 

[zeng]

Manufacturing tolerance range has been tightened for the past 30 years or so.
Tighter tolerance, if any, is more of consequential ..

 

[BreakerBreaker]

Originally Posted By: zeng
Manufacturing tolerance range has been tightened for the past 30 years or so.
Tighter tolerance, if any, is more of consequential ..


This another reason why thicker oil is like a dinosaur, most the time, IMO - The thinner oil flows in those smaller galleys and such better than the thick stuff that feels nice and flows fine when warm or full hot, but, that's it.

 

[Pontual]

Much talk, little evidence makes it.

 

[goodtimes]

It's interesting Mercedes with their AMG engines, each engine is assembled, or "fitted" by a human, who signs their name to it. Those are supposed to be their best engines. I would have to guess and say clearances haven't changed much, some have tightened up, but tolerances depends. In 1920 quality machines were hand fitted and absolutely works of art.

 

[andyd]

Soulless machines making soulless transportation appliances. Taunting displaced workers with their soulless perfection...

Makes me glad/ sad I was raised in an analog world. Robots cannot make art.

 

[fdcg27]

I think you're right in looking at improved oils as a primary source of increased engine life.
I think that another major contributor is the universal use of fuel injection coupled with tight operating conditions controlled by the PCM.
Manufacturing tolerances have probably improved, but looser tolerances are accepted in some cases, particularly piston fit.
You won't find very many if any volume production engines where the piston assemblies are measured and matched to the bores, which was fairly common practice not so many years ago.

 

[ShotGun429]

Yes,we have better engines today, Better oils, and unleaded Fuels help Engines Live much longer today, But also I see the old tech engines from the mid 1950's-1960's living a very long life also with todays great oils and unleaded fuels.

 

[SandCastle]

Tolerance and clearance are being used interchangeably in this thread, yet they are not same thing. Tolerance refers to the variation of the characteristic. Whereas bearing clearance (gap) is the result of a combination of several dimensions (eg, cylinder bore diameter minus piston diameter).

I suspect tolerances (variations) have gotten smaller in recent years due to improvements in machining. However, in the case of piston-to-cylinder clearance, in the new generation engines this is getting BIGGER to reduce sliding friction and thus fuel consumption.

 

[Chris142]

Clearances beteen say a rod bearing and a crank have not changed.you must have a certain amount of clearance per inch of circumference.that cant change and has not changed since the 50's. What has changed is the tolerances.everything now is on the tighter side where older stuff was allowed a larger gap

 

[CT8]

Clearances is the term you are wanting . Tolerance is the permissible limit or limits of variation of the clearances. It is easy to look up the clearances . They are not a whole lot different. Though as mentioned the newer machining and processes are better all due to the stricter emission standards and warranties.

 

[FowVay]

I took a brief moment to browse AllData and get a couple of numbers for comparison. Vehicles are a 1985 Honda Accord 1.8 liter VS. a 2012 Honda Accord 2.4 liter:

Camshaft oil clearance for 1985: journal 1 = .002"-.004", all others are .005"-.007"
Camshaft oil clearance for 2012: journal 1 = .00118"-.00272, all others are .00236"-.00390.

Con rod oil clearance for 1985: .0008"-.0015"
con rod oil clearance for 2012: .00126-.00260

crank bearing journal 1985: .001"-.0022"
crank bearing journal 2012: .00067-.00161

piston-to-bore clearance 1985: .0008"-.0016"
piston-to-bore clearance 2012: .00079-.00157

So you can see that there hasn't been a whole lot changed over the years in terms of clearances and variances in tolerance.

Materials and procedures have certainly improved though. Even the serviceable limits on worn components has remained steady between these two examples.

 

[edhackett]

Originally Posted By: sciphi
Yes, they have.

As an example, GM got the cylinder dimensions precise enough on the 1.4T engines going into the Cruze that they could safely pick out random piston assemblies and be sure they'd fit.


BMW did that with the K bike engine first sold in 1983.

Ed

 

[edwardh1]

Originally Posted By: FowVay
I took a brief moment to browse AllData and get a couple of numbers for comparison. Vehicles are a 1985 Honda Accord 1.8 liter VS. a 2012 Honda Accord 2.4 liter:

Camshaft oil clearance for 1985: journal 1 = .002"-.004", all others are .005"-.007"
Camshaft oil clearance for 2012: journal 1 = .00118"-.00272, all others are .00236"-.00390.

Con rod oil clearance for 1985: .0008"-.0015"
con rod oil clearance for 2012: .00126-.00260

crank bearing journal 1985: .001"-.0022"
crank bearing journal 2012: .00067-.00161

piston-to-bore clearance 1985: .0008"-.0016"
piston-to-bore clearance 2012: .00079-.00157

So you can see that there hasn't been a whole lot changed over the years in terms of clearances and variances in tolerance.

Materials and procedures have certainly improved though. Even the serviceable limits on worn components has remained steady between these two examples.


wow real numbers, and from a company who makes smooth running engines but other factors may cause that.

 

[A_Harman]

Originally Posted By: edwardh1
Originally Posted By: FowVay
I took a brief moment to browse AllData and get a couple of numbers for comparison. Vehicles are a 1985 Honda Accord 1.8 liter VS. a 2012 Honda Accord 2.4 liter:

Camshaft oil clearance for 1985: journal 1 = .002"-.004", all others are .005"-.007"
Camshaft oil clearance for 2012: journal 1 = .00118"-.00272, all others are .00236"-.00390.

Con rod oil clearance for 1985: .0008"-.0015"
con rod oil clearance for 2012: .00126-.00260

crank bearing journal 1985: .001"-.0022"
crank bearing journal 2012: .00067-.00161

piston-to-bore clearance 1985: .0008"-.0016"
piston-to-bore clearance 2012: .00079-.00157

So you can see that there hasn't been a whole lot changed over the years in terms of clearances and variances in tolerance.

Materials and procedures have certainly improved though. Even the serviceable limits on worn components has remained steady between these two examples.


wow real numbers, and from a company who makes smooth running engines but other factors may cause that.


Interesting how the cam bearing clearance has been tightened up, yet the tolerance band has also tightened.

But the rod bearing clearance has gotten larger, despite the migration to thinner oils. That is opposite the direction I was expecting to see.

 

[TFB1]

Originally Posted By: BreakerBreaker
Originally Posted By: zeng
Manufacturing tolerance range has been tightened for the past 30 years or so.
Tighter tolerance, if any, is more of consequential ..


This another reason why thicker oil is like a dinosaur, most the time, IMO - The thinner oil flows in those smaller galleys and such better than the thick stuff that feels nice and flows fine when warm or full hot, but, that's it.

Who has ever said the oil galleys are now smaller?? If galley size was so critical a 5W-20 had to be used to insure adequate lubrication, the bearings would oil starve at temps below freezing...

 

[benjy]

todays manufacturing is both faster + more exact for sure! i am not a sure but wonder even on CNC machined parts if the cutters wear does the machine compensate for this. makes you wonder where the USA pushes thinner oils for mpg some of the same exact cars sold in europe spec heavier oils, i smell a rat!!! a few mpg VS a longer lasting engine i think!!! unless ALL the parts are made "in house" NOT globally there is still room for error. look at the recalls these days, cheaper parts from the lowest bidder cause problems, even some high $$$$ models have issues so unless an engine is "bluprinted" hand built + all clearances checked there will always be variations + expect more with low $$$ cars even today, car manufacturers are too GREEDY always looking for more profits!!!