I would say the discussion has taken a few twists... but sure... even in a running engine....
An engine running at 160* F with the same compression ratio as one running at 220*F will be more resistant to knock... will it not?

Cause I can sure show you in TunerPro where the BIN has a SA compensation for temperature and it is not increasing advance as the temp goes up.

 

Yes, this has gone way, WAY off the rails.


It will. That is why....

 

Lol! Is there anything else obvious you want to get off your chest?

 

Well, if it is so obvious what is your issue then... cause external heat not from immediate compression seems to be the debated point here...

You left out heat there obviously, but...
While we are talking obvious things... heat can come from many sources for a running or non-running engine too. Residual heat, ambient heat, radiant heat...etc. There also is indeed heat in a resting engine, if only from ambient air, there is a measure of heat energy... just to be obvious which it must not be for you since you said there wasn't.

Less impact than timing or compression, but sucking in and resting in air above 100*F is going to make an engine more susceptible to knock than being in 50*F air... not to mention the less dense ambient air would actually bring down the density of the air in the cylinder and drop dynamic compression ratio as I understand it. Just as we discussed about diesels, they sure start easier when in warmer weather.

 

Sorry Kyle there is no other source of ignition in a diesel engine. Just the HOT compressed air mixture burns the fuel

"Diesel engines work by compressing only the air. This increases the air temperature inside the cylinder to such a high degree that atomized diesel fuel injected into the combustion chamber ignites spontaneously."

Glow plugs and Ether are used in extreme cold weather environments on vehicles that need to be ready to run. The Coast Guard uses block heaters to get the oil warm before cranking. Remember that there are two stroke diesels and four-stroke diesels. Old marine diesels were frequently two stroke diesels which is another ball of wax. I literally had nothing on my 4-236 to assist in starting the engine except the starter motor. My little 4-236 would light off almost instantly when you cranked the engine as long as the fuel was turned on at the mechanical pump. On my boat it was sitting out in the open where a Chrysler 318 sat before and it was awesome, it burned 1.3 gallons per hours at 12 mph cruising. The Chrysler 318 used 10-15 gallons per hour at cruising and could go faster than the diesel. Being in a marine application I had no radiator, I simply had a sea-water heat exchanger for the engine coolant and another cooler on my transmission lines. I had to use a thermostat to get the engine to stay above 180* or it would blow black smoke.

On my way up the coast I arrived at the river coming from Wilmington N.C. and all the big sailboats and cruisers were waiting for the tide to change. Not me, with all the torque that little diesel made I was able to go upstream where the current was flowing downstream. I got the choicest anchorage as I was anchored and having dinner when the other boats started to show up. The buoys were at a 45* angle (towards the ocean) when I was going upstream at 7 knots.

My 427 with the 12.25-1 will not detonate at lower temperatures like 160* (Unless you advance the timing too much). It will start getting more iffy when the engine is 220*, the hotter the engine is the more likely it can and will detonate. This is the primary reason I have the L88 Hood set up like the factory used to. It assures the engine is getting the coolest air possible, the entry point for the combustion air is at the base of my windshield. With higher compression you can have more intake roar as it is using a lot of air. The folks at GM were experimenting with this hood setup from 1963 on and used it very well on their race cars. Even when the air outside is hot it is still cooler than what most Corvettes get from under the hood. The cooler the combustion air the more power you can make. Yes, the extremely fine mist released by the water/methanol injections system does help cool down the intake manifold. My spray is released at 150 psi through two misting calibrated injectors, I shoot one side to half of the dual plane manifold and the other to the opposite side (Left side and right side). Just imagine two injectors spraying towards each other while the engine is running and that is the method I am using with the Snow Performance water/methanol injection system. The Holley Sniper Software will be ultimately controlling the injection of the water/methanol and only squirt when the engine is above 160* and I can control it using a vacuum switch on the Holley Stealth Sniper.

The utter Simplicity of the diesel is the Beauty of the diesel!

We used British Lister Petter air cooled diesels at my work, these engine came in 1, 2, 3 and 4 cylinder configurations. The only time I ever had to put a cold start kit on a diesel was for an application far up in Alaska. It simply squirted Ether into the engine and would then crank and that little engine worked fine. Everywhere else in the world I used nothing but a good fuel filter in these and the Lister engines would run for decades. These engines are all over the world and the only thing to help starting them is a compression release so you can hand crank. Have any of you ever tried to hand crank a four cylinder diesel? It takes a bit of energy and lots of muscle. Excessive use of Ether will damage the rings on your diesel so heating the coolant is probably the best way. This is why most Fire Stations in the cooler climates plug their vehicles in allowing them to be used in an instant being pre-warmed. It is done on boats as well. Trying to start a big diesel cold takes a lot of energy. This explains why so many big rig truckers keep their engine running all night, if it cooled down it could be hard to get on the road quickly the next day. Our 3 kw Lister Petter diesel Generator used a 4.5 kw electric starter motor, kind of silly. High Compression makes cranking harder on the starter so I pull 20* off my timing and crank it with a gear drive starter. Now it sounds like a Chrysler engine cranking

Today we are seeing a resurgence in the popularity of High Compression in Motorcycles and cars. I was looking at one bike with 13.4 compression ratio. They are able to do this with the newer technologies available and they do it just to make more power! There is a company who makes a Ignition control system that uses knock sensors and will retard a particular cylinder only if it detects a knock from that particular cylinder. This technology was used by Bosch and is what allowed the C5R's to finish a race with the piston rings intact. Today GM uses it in all the new Corvettes.

Cool combustion air and cool Fuel can make more power on virtually any engine. It allows more overall timing without any issues and makes more power. I have a Be Cool radiator in it currently but after speaking with Tom at DeWitt Radiator, he will be making the next radiator with more effective cooling capacity than anything off the shelf. I have insulated my fuel lines bringing the fuel forward and covered them in fire protection hose inside the engine compartment.

To make my power steering system happy I installed a larger reservoir that hold about a quart and a half in it. I also insulated the s.s. braided lines that carry the power steering fluid. If you want to keep your steering system happy just keep the fluid cool and your seals and other parts will last longer. The cooler the fluid the longer it will last. This makes the parts last a lot longer as seals don't do well with excessive heat.
I think even Humans do better when we are kept cooler...

 

Hahaha... OK.

Run a cold diesel engine in -40* Alberta and tell me that. It will run a lot better after it has ran for a few minutes and built up heat.

To be technically accurate, even -40*F has "heat" energy. Any air ingested above absolute zero, -459.67*F, does have heat energy that is coming into the combustion chamber.

If there is no other heat, why do diesles have cooling systems.... come on now. Yes... even air cooled fins.

Cause all engines retain heat from combustion cycle to combustion cycle. Too much actually and some has to be carried away so the materials don't start to swell and lock the engine up. So, there is plenty of heat in the combustion chamber and piston dome. Which is what external sources or glow plugs are introducing... or utilizing a fluid with a lower flash point, is heat to the chamber.

 

But why if there is no other heat sources

As I said, heat can come from many sources, even when the engine is at rest.

Diesel and Gas are the same in the respect of waste heat and heat retention.

 

Since this thread is so far gone, I'll tell a story, too....
One ski resort I worked at had an '84 F-250 4x4 with a 4 speed and a 6.9 diesel. Anyone know what I pile of dog turd that engine is? The whole truck, for that matter.
Anyway, when I started that job, that truck was hard starting. Every morning the crews struggled to get it to start. I did the basic things; filters, batteries, replaced the glow plugs, glow plug relay, new starter...it helped....for a little while. The glow plugs didn't last. Neither did the glow plug relay. I put more in...they helped for a while. It got so bad, that we had to start roll starting it. Then it got so bad, it would take 4 trips around the shop, chucking black smoke but not really "running" before it would finally roar to it's 120hp "life". Then it got hard to start, even warm. I did a compression check; it was fine, so I got a new injection pump, glow plugs and glow plug relay, put it all in there...and voila! It worked great! ...For a little while.

By this point, I was "over it" with that turd. I bought an Ether start kit designed for our snow cats, and installed it on to the F-250. It had a feature that would only allow ether activation while cranking, and it would only shoot a metered amount. Well....that worked...for a little while. Then the starter couldn't really deal with the ether -like over advanced timing on a gas engine trying to start. It would fire every time, but too soon and the firing would stop the crank, dead for a second. I installed a later model "power stroke" starter which was a Mitsubishi, gear reduction unit. That sort of worked....for a little while. Then it struggled too. It just wouldn't spin the engine fast enough.

Finally, I found the "silver bullet"; I re-wired the starting system so that in "crank", the starter was getting hit by both batteries in series giving the starter motor 24v. Release the key to "Run" and everything functioned as a normal 12v/2 battery system in parallel. Good god...that sum - bee fired up and fired up FAST, every morning after that! That starter motor spun that engine over SO fast, then you hit the ether button...and she's running....no matter how much she didn't want to!

Turd.




That is old skool. Modern diesels can start right up cold, and drive away w/in 5 minutes. Idling your diesel, now days is DUMB. It's what the ignorant do.

 

One last try. No one is disputing that a diesel will run better when warmed up. Any engine will run better when warmed up. In the days when carbs and chokes were used, the engine did not perform to its max until the choke came off. What IS being disputed is your assertion that a diesel will not start or run without an external heat source such as a glow plug. You said so in post #71. It's there in plain English. You have said that the heat of compression is not enough to cause ignition. This is totally wrong. I don't believe you are a dumb person. Just admit you are wrong. In a very cold environment, I totally agree with you that external preheat is necessary but that is for a totally different reason. To claim that a diesel cannot start without external heat is just totally wrong.

PS: I have lived in -40 Saskatchewan my entire life(right next door to Alberta, which you mentioned). I can assure you that I don't need any schooling as to what will or will not run in this environment.

 

My comments are in bold.

 

Never saw a test that proves any of the snake oils work other than an unscientific testimony. I have bench tested my injectors, sent them out and retested and found higher flow values and closer to spec. They do change the filter and clean the varnish build up.

 

So at what point does a 350 CID N/A gas burning engine cross the line into a high compression high performance engine that should be burning 93 octane ?

 

If said 350 can have detonation quelled by the 3 point difference, why not? If you increase the timing till you get detonation and you can quell it with 3 points more of octane, why not?

 

Depends....on "everything".
Head material
Combustion chamber design
Timing
Tune
CAM timing/duration
Operating Temp
Operating environment
Operating conditions (a 350 in a 'Vette Kart? Or a 350 in a 1 tone truck pulling a trailer?)
Elevation
Air temp
Intake tract design
Intake tuning

Many factors involved with this, that make it hard to pin point a specific number where it needs one octane vs. another.

 

I use 91 in my LT1. Shell. But it really doesn't have an impact on performance compared to 93, of any other brand. You don't need to pay any attention to "armchair chemists" who prattle on about diesel engines, for some unfathomable reason, they seem to be desperately seeking relevance.

 

It depends. If you're advancing the timing, and noticing/measuring a performance improvement (but hearing knock/detonation), then going to a higher octane to get rid of the knock makes sense.

But, if you're just advancing the timing ( without measuring any performance changes), following the old wives' tale of more advance means more power, then it's foolish to purposely make the engine knock, and economically foolish to spend additional money to bandaid the timing error.

 

In addition to the good information Tom400CFI posted earlier, vehicles driven in low humidity locations will tend to knock more than in humid areas.

And as in your avatar, the later LT5s make so much internal mechanical noise that it overwhelms the knock/detonation frequency at certain RPMs, requiring the "broad use" of higher octane (93) gas to quell any detonation in those conditions/RPMs that the knock system can't hear the actual detonation.

 

If you suck air in at any temperature above 0*K it has external heat energy in the combustion chamber. That is the most technically correct answer there is. I also showed were someones referenced engine's own manual said use some external method or expected extended cranking times... read has to build up some heat. If you don't think an engine retains heat from compression cycle to compression cycle I just don't know how else to explain it. If you can't understand a hot chamber contributes to resulting detonation in a gas motor

Sorry, I don't feel the need to write an extended term paper for every comment. Heat in any engine contributes to ignition, warm engines start and run easier because of this (unless something else is wrong).

Then there is this...

"A diesel engine is started by driving it from some external power source until conditions have been established under which the engine can run by its own power. The simplest starting method is to admit air from a high-pressure source—about 1.7 to nearly 2.4 megapascals—to each of the cylinders in turn on their normal firing stroke. The compressed air becomes heated sufficiently to ignite the fuel. Other starting methods involve auxiliary equipment and include admitting blasts of compressed air to an air-activated motor geared to rotate a large engine’s flywheel; supplying electric current to an electric starting motor, similarly geared to the engine flywheel; and applying a small gasoline engine geared to the engine flywheel. The selection of the most suitable starting method depends on the physical size of the engine to be started, the nature of the connected load, and whether or not the load can be disconnected during starting"

The bold being what I am getting at... heat needs to build for conditions to be right. Sorry if an off the cuff comment or a quick reply misstated my position... My position still remains heat must be present in a diesel in some form or another before it will just fire off. Same as heat building in a gasoline motor will contribute to pre-ingition. So do read this as I agree a diesel engine can start on its own after enough compression cycles have occurred for the conditions to be right.


I picked that as it was the coldest place I ever was with my diesel for an extended stop. Even after remaining plugged in, it was not too happy to run for about 10 minutes.

 

I would say that more advance gives the POTENTIAL for more power. Now once you hit that magic point, it will slide backwards. I probably won't advocate something like simply advancing the timing without testing. I would probably do it on a dyno where we can see what brings what and try it with both 89 and 93 and see which gets better power with the tuning

 

Thanks Tom & 69427, I'm right at 500chp with intake and head porting headers custom dyno tune and 11.4 CR, was tuned at 93 octane. I do monitor the numbers and knock with a live time scanner several times a year and never had any issues but never used 91 gas. 69427 you are correct as to engine noise the LT5 sounds are very unique to say the least...