2 interesting topics. Warming up your engine before leaving the drive. Piston travel.

B

Bob Dunahugh

New member
Sep 17, 2012
2,784
4
3
We were with some GMC people last weekend. And it was mentioned that one pe=
rson wouldn't leave till the engine was to full operating temps. It's true =
that there is less wear at full engine temp. But that temp is reached much =
faster while driving. As there is more fuel burned while on the move. Thus=
the engine has more BTU's used up in the process. The cylinder walls, an=
pistons have had 2000 degrees put to them. As to the oil getting moved aro=
und. In one minute. The oil filter, and all oil passages were full to start=
with. The oil pump has delivered about another 6 qts to get every moving p=
art lubed. The engine has had the crank rotate around 700 times in that min=
ute.. I'm sure there are lots of thoughts on this one. I use the one minut=
e idea. One of the things that help these engines last so long. ( As long =
as there maintained properly.) Is you don't use them for short trips. Thus =
less cold starts per mile. As a interesting side note. The 403 piston trave=
ls less feet per mile then a 455. So does a 403 piston/rings last longer? =
Bob Dunahugh 78 Royale.
 
Bob,
I am going to respond to these inline and based on log time engine test lab experience.

> We were with some GMC people last weekend. And it was mentioned that one person wouldn't leave till the engine was to full operating temps.
> => There nothing good that happens to in an idling engine.
>
> It's true that there is less wear at full engine temp. But that temp is reached much faster while driving.
> => In my durability dynos, the rule was always to stay under 1500 and 15"Map (~14" vacuum) until lube oil it 100°F. This never took very long.
>
> As there is more fuel burned while on the move. Thus the engine has more BTU's used up in the process. The cylinder walls, an pistons have had
> 2000 degrees put to them. As to the oil getting moved around. In one minute. The oil filter, and all oil passages were full to start with.
> => Whether the oil passages were full or not is an open issue and depends on the engine and how long it had been sitting. It can take 30 seconds
> to a minute for all the places that get oil to actually get any after a long sit. That 100°F is never very far behind.
>
> The oil pump has delivered about another 6 qts to get every moving part lubed. The engine has had the crank rotate around 700 times in that
> minute.. I'm sure there are lots of thoughts on this one. I use the one minute idea. One of the things that help these engines last so long. ( As
> long as there maintained properly.) Is you don't use them for short trips. Thus less cold starts per mile.
> => You are very correct about cold starts being tough on every thing. This is why capital engines (like it ships) are kept hot with heating
> systems when not actually running.
>
> As a interesting side note. The 403 piston travels less feet per mile then a 455. So does a 403 piston/rings last longer?
> => Hang on tight, here we go....
> Piston travel is a definite issue, but it takes a back seat to BMEP (Brake Mean Effective Pressure). BMEP is what makes the force to push the
> piston so then engine makes torque. More BMEP is more load on the rings.
> The larger piston 4.351 (403) vs 4.126 (455) would make for lower BMEP at the same torque,
> BBUUTT
> The shorter stroke 3.385 vs 4.250 means it takes more BMEP for the same torque output.
>
> Bob Dunahugh 78 Royale.

To move the coach down the road will take XX horsepower. HP = RPM X Torque / 5252
So, if you put a high numerical final drive on a 403 so it does not need as much BMEP to get down the road, you can unload the rings and probably
before you get to the same piston travel per mile, you may beat break even. It is a given that spinning the short stoke engine will be more to its
liking. (This is exactly why I am such a great proponent of 3.70s in for 403 coaches.)

Now, did that clear anything up for anybody?
If you can form a question, I will do my best to provide an answer that you can understand.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Matt,

With reference to the idling before setting off issue, and the piston feet per minute, I am assuming that the higher compression, the higher BMEP, all
things else being equal, the greater ring and cylinder wall wear?

That, if true, might mean that the new Mazdas with their "Skyactiv" technology with 14 to 1 compression will wear out sooner. There is the factor as
well, that I have read that engines last far longer with fuel injection due to the excessively rich condition with carbs when cold. Like, about twice
as much mileage on a engine before it is worn out.

Looking at the factor that friction increases as the square of RPM, it would also make sense that operating at low RPM would add engine longevity as
well, assuming that the friction increase at least is partly located in the piston-cylinder interface and will result in increased wear. Hard to see
where if there is no friction, that any wear at all will occur.

Not anything I have measured, to be sure. I have been an advocate for setting out immediately with a cold engine, not asking more than the minimum
until there's an indication on the temperature gauge, or on my Toyota, when the green "cold engine" light goes out. I've never worn out an engine in
my life. Oops, those chain saws I lunched due to using on-hand outboard oil in the fuel mix, I wore them out. How easy it is to believe I am smarter
than the company engineers. And to find out the hard way they were right. It took two chain saws before the light came on. You have to use 2-stroke
oil rated for "air cooled engines", at least my experience has bought me that knowledge.

Thanks for sharing your hard-won knowledge with us. It's really interesting.

Carey

--
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
 
Your not going to wear out an engine, but you will start consuming oil.
The new synthetic oils will protect the warm engine even at higher rpm

Sent from my iPhone

>
> Matt,
>
> With reference to the idling before setting off issue, and the piston feet per minute, I am assuming that the higher compression, the higher BMEP, all
> things else being equal, the greater ring and cylinder wall wear?
>
> That, if true, might mean that the new Mazdas with their "Skyactiv" technology with 14 to 1 compression will wear out sooner. There is the factor as
> well, that I have read that engines last far longer with fuel injection due to the excessively rich condition with carbs when cold. Like, about twice
> as much mileage on a engine before it is worn out.
>
> Looking at the factor that friction increases as the square of RPM, it would also make sense that operating at low RPM would add engine longevity as
> well, assuming that the friction increase at least is partly located in the piston-cylinder interface and will result in increased wear. Hard to see
> where if there is no friction, that any wear at all will occur.
>
> Not anything I have measured, to be sure. I have been an advocate for setting out immediately with a cold engine, not asking more than the minimum
> until there's an indication on the temperature gauge, or on my Toyota, when the green "cold engine" light goes out. I've never worn out an engine in
> my life. Oops, those chain saws I lunched due to using on-hand outboard oil in the fuel mix, I wore them out. How easy it is to believe I am smarter
> than the company engineers. And to find out the hard way they were right. It took two chain saws before the light came on. You have to use 2-stroke
> oil rated for "air cooled engines", at least my experience has bought me that knowledge.
>
> Thanks for sharing your hard-won knowledge with us. It's really interesting.
>
> Carey
>
>
> --
> Carey from Ennis, Texas
> 78 Royale, 500 Cadillac, Rance Baxter EFI.
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
> Matt,
>
> With reference to the idling before setting off issue, and the piston feet per minute, I am assuming that the higher compression, the higher BMEP,
> all things else being equal, the greater ring and cylinder wall wear?
>
> That, if true, might mean that the new Mazdas with their "Skyactiv" technology with 14 to 1 compression will wear out sooner. There is the factor
> as well, that I have read that engines last far longer with fuel injection due to the excessively rich condition with carbs when cold. Like, about
> twice as much mileage on a engine before it is worn out.
>
> Looking at the factor that friction increases as the square of RPM, it would also make sense that operating at low RPM would add engine longevity
> as well, assuming that the friction increase at least is partly located in the piston-cylinder interface and will result in increased wear. Hard to
> see where if there is no friction, that any wear at all will occur.
>
> Not anything I have measured, to be sure. I have been an advocate for setting out immediately with a cold engine, not asking more than the
> minimum until there's an indication on the temperature gauge, or on my Toyota, when the green "cold engine" light goes out. I've never worn out an
> engine in my life. Oops, those chain saws I lunched due to using on-hand outboard oil in the fuel mix, I wore them out. How easy it is to believe
> I am smarter than the company engineers. And to find out the hard way they were right. It took two chain saws before the light came on. You have
> to use 2-stroke oil rated for "air cooled engines", at least my experience has bought me that knowledge.
>
> Thanks for sharing your hard-won knowledge with us. It's really interesting.
>
> Carey

Carey,

Unfortunately, higher compression does not make for a universally higher BMEP. Compression ratio is a static number and BMEP is completely dynamic.
There is a lot that goes into BMEP, but all BMEP does come out as torque.

Skyactiv is a Mazda label for lots of new stuff. It covers a diesel, a transmission and a direct injection SI engine. The claimed 14:1 may be real,
but for it to be an SI (Spark Ignition) engine - even while direct injected, it needs to control the manifold pressure. Direct injection for SI
engines is not new. The DB605 used in the BF109 was a direct injected engine.

Just in my working lifetime, engine building technology has made amazing changes everywhere. One of the biggest has been the capability of
manufactures to make round cylinder bores. The round bore allows a low tension ring. The low tension ring allows the use of both a better oil
control hone finish on the bore wall and a better wearing alloy for the compression rings. This all adds up pretty fast.

There is a variety of engine dynomometer that is just a big DC machine on bearings. The reason I said machine is because they are capable of both
motoring and absorbing. Very early in every engine program, we would do a motoring curve. With the intake at WOT, spin the engine at continually
increasing speed to see that A: Everything works as it should (disasters are less exciting with cold engine) and B: Actually measure the internal
friction. The observed friction increase was typically very linear until higher speeds when the pumping loss for the charge air would get in the way.
If you happen to notice, the more recent engines pay a lot of attention to the intake and exhaust design. This is not just your imagination. There
is a lot that can be done there. And with the EPA pushing so many things, smaller engines doing more work can be an advantage to many things.

The wet fuel issue was first noticed when passcar engines were converted to gas fuel - either LP or natural - and it is real, but they do still have
wear issues. Those engine still do not live forever, but an industrial 455 on natural gas will come pretty close. Those were shipped with hard
exhaust seats and forged cranks.

Let's not get into the problems of crankcase scavenged 2-stokes. They are a breed all to there own. You are not nearly the only person to discover
that the wrong lube oil is a bad idea.

It is my honor to share as much as I can. I get to where I am with the help and guidance of many good people.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Observations about wear from compression ratio and stroke:

If static compression were an issue, diesel engines wouldnt last very long.

I don't know that the marginal increase in stroke itself [ie piston travel]is a significant factor in ring wear. What I have observed though is that
longer stroke engines, particularly with shorter or less than optimim rod length:stroke ratio seem to have much worse bore wear, probably from the
side load. The bores almost always seem to be out of round

May be less of an issue with lower RPM/load and higher nickel blocks.
--
76 Glenbrook
 
Water. Water is the issue during a long cold and lazy warm up. More than a gallon is produced for each gallon of fuel burn. Thankfully most exits via
exhaust but the rest ends up in the oil until it boils off. After about 60 Secs (and bags have reached auto level) I drive off gently to minimize
idling. Then drive normally but not aggressively til normal temp. On a sliding scale I would adjust times with temp drop. Might be 2 mins below zero
and driving more gently at first as well. But road load is your friend in the anti watering war. Also the dash heat will work much sooner and forward
progress beats 0 MPG any day.
--
John Lebetski
Woodstock, IL
77 Eleganza II
 
Ring reversal under combustion pressures wears rings, cylinder bores and
piston ring lands and grooves about as much as anything else. Compound that
with dirty intake air fuel mixture, and not enough lubrication at the top
of the bore and you can see why the top of the bores wear more than the
bottom does. Further compound that issue by doing it when the engine oils
and coolant is not at operating temperature and you have your answer to why
cold engines wear more quickly than warmed up ones do. Many more factors to
consider here, but that's enough to keep this conversation going for now.
Jim Hupy
Salem, Or (currently at a GMC CASCADER rally at Westport, Washington. It is
a balmy 39 degrees farenheit and the sun is just peeking over the clear
cloudless horizon. Travel home today, where it currently is 28 degrees.)

> Water. Water is the issue during a long cold and lazy warm up. More than a
> gallon is produced for each gallon of fuel burn. Thankfully most exits via
> exhaust but the rest ends up in the oil until it boils off. After about 60
> Secs (and bags have reached auto level) I drive off gently to minimize
> idling. Then drive normally but not aggressively til normal temp. On a
> sliding scale I would adjust times with temp drop. Might be 2 mins below
> zero
> and driving more gently at first as well. But road load is your friend in
> the anti watering war. Also the dash heat will work much sooner and forward
> progress beats 0 MPG any day.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
With flat motors, we said as soon as it would take full throttle without stumbling, it's warm enough to fly. By the time you do your runup, and cycle
the prop, it'll be that warn. Same with the gmc, by the time you check everything after you crank it and get out on the streert, it's ready to ride,
and uless you live at an exit, the GMC should be warm enough for freeway speeds.

--johnny
--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased
 
Well....my brain turned to OATMEAL on this thread. Happy someone understands it.
--
Ray Erspamer
78 GMC Royale
414-484-9431
 
Ah, Man...as my guru John Muir said... " Fire it up and roll one, that's
how much warm up it needs !"

Peace Brother...

https://en.wikipedia.org/wiki/John_Muir_(engineer)

> Well....my brain turned to OATMEAL on this thread. Happy someone
> understands it.
> --
> Ray Erspamer
> 78 GMC Royale
> 414-484-9431
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Michael Beaton
1977 Kingsley 26-11
1977 Eleganza II 26-3
Antigonish, NS

Life is too short to hold a grudge; slash some tires and call it even !
 
Matt,

Thanks for your response with regard to motoring (running by electric motor with no fuel to the engine), a gasoline automobile engine when it was cold
to graph the friction to rpm factor. I was surprised to read that your experience that the friction was pretty linear. I have since looked on the net
and found some engineers at MIT have done the same thing, and their graphs, both predicted and measured look much like a linear relationship with some
mild upward curve until as you say pumping losses begin to rise quickly. I have also glanced at equations of total engine friction vs RPM and one
factor does increase as the square of RPM, but it is only one of a number of factors, the others being linear, if I understand them. Real world
experience as you have related to us is helpful. (I imagine you ran with throttle plates fully open?)

With reference to the comment by Jim K on never wearing an engine out but seeing them increase oil consumption. I have never worn an engine to the
point that the oil consumption was over, say, 1000 miles per quart. Most were negligible. I don't like to burn oil. Not too religious about oil
changing, but I do avoid high RPM if I can.

Got a story Chris, about a friend who bought a diesel over the road truck new some years ago. It used a 3208 Caterpillar engine. In the first three
months, he cracked a piston. Took it back to the Cat dealer, and when he picked it up, he asked the dealer what he did. "Just replaced the piston."
He said, "What, no boring, no honing, just replaced the piston and rings?", Dealer says, "Yes, you will be OK." He ran the truck 750,000 miles and
sold it and it ran years afterward. So, even with diesel fuel having some lubricating properties, the high compression is no problem for it, as you
say.

One more story. I have gone to China 12 times now, and remember the Volkswagen Santana taxis all over the place. Gasoline, manual shift. The first
few times I rode in them, I had to bite my tongue. They short shifted them, first to about 7 mph, second to 12,skip to fourth and lug the engine up a
ways and to fifth, to get the rest of the way to 35 mph. I confidently predicted to myself that they were beating the bearings out of the engine. I
looked at the odometer, 270,000 kilometers. Other taxis were achieving like mileages. Got back from China last month, and on that trip they were doing
the same thing. I figured more economy due to two factors, lower friction, and the largest factor, smaller pumping losses due to greater throttle
opening. Fuel injected, ordinary cars otherwise. Four door midsize sedans.

Carey



--
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
 
> Well....my brain turned to OATMEAL on this thread. Happy someone understands it.

Ray,

I am glad that you made this statement....

What you need to know is:
Nothing good happens at idle.
Never abuse a cold engine.

So, if the engine is stable enough to pull the vehicle, go.
If the temperature gauge is off the pin, run it.

It that not easier to grasp?

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Absolutely! Thank you. My techniques has been.....start it up, let it fast idle for a minute....and if the choke is set right it will either go and
cough....if it coughs I let it warm up a bit more. If it pulls steady I drive it without abusing it.
--
Ray Erspamer
78 GMC Royale
414-484-9431
 
It is all about setting the choke.
Too much is not good either.
Ray, I feel your procedure is good as it is better on the lean side during
choke mode.

> Absolutely! Thank you. My techniques has been.....start it up, let it
> fast idle for a minute....and if the choke is set right it will either go
> and
> cough....if it coughs I let it warm up a bit more. If it pulls steady I
> drive it without abusing it.
> --
> Ray Erspamer
> 78 GMC Royale
> 414-484-9431
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
I like reading thru this but I'm in the se boat, half of it is over my head. I'm kinda thinking the conclusion was let it warm up a couple minutes
and drive on?? Not sure, but anyhow I wanted to mention for me after the crossover ports were blocked, this has been a bear to keep running after a
cold start. When it gets 20 or 30 here in KC iif I have to drive her somewhere then she not too happy about it unless she gets 5 or 10 on the warm up.
Am I missing something on that mod?

Tom
76 Eleganza 2
KCMO
 
CallTom,
So you have an electric choke?
If you did not you neglected to make a required change.
Call me and I will advise you as to what you need to do.
There are always somethings that are not pointed out as it is assumed
people should know. I for one tend to over explain as I never know that
they do not know.

> I like reading thru this but I'm in the se boat, half of it is over my
> head. I'm kinda thinking the conclusion was let it warm up a couple minutes
> and drive on?? Not sure, but anyhow I wanted to mention for me after the
> crossover ports were blocked, this has been a bear to keep running after a
> cold start. When it gets 20 or 30 here in KC iif I have to drive her
> somewhere then she not too happy about it unless she gets 5 or 10 on the
> warm up.
> Am I missing something on that mod?
>
> Tom
> 76 Eleganza 2
> KCMO
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
Hey Jim, I do have a electric choke. I will give you a call. No worries on over explaining with me, not at ground zero but still hovering below the
tree line.
 
> I like reading thru this but I'm in the se boat, half of it is over my head. I'm kinda thinking the conclusion was let it warm up a couple
> minutes and drive on?? Not sure, but anyhow I wanted to mention for me after the crossover ports were blocked, this has been a bear to keep running
> after a cold start. When it gets 20 or 30 here in KC iif I have to drive her somewhere then she not too happy about it unless she gets 5 or 10 on
> the warm up. Am I missing something on that mod?
>
> Tom
> 76 Eleganza 2
> KCMO

Tom,

By next winter, I will know more, but I suspect that you are partly correct. My experience is not with an Olds 455, but I have run more than a few
V-8s that did not have the heat riser in the intake manifold. They are always "cold blooded". One of the things that I know you will need is the
thing called a warm air stove and damper in the intake horn. While these were mostly unneeded, with the cold intake, they may now be needed.

There is another thing that is sort of hidden. If you are running the choke element off the alternator output, you may need to look up and get the
temperature switch so it does not open too soon.

As said, ask me again next year.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
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