2.4 Engine Timing and Combustion Temperature
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Thread: 2.4 Engine Timing and Combustion Temperature

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    Just Some Dude in Jersey The Scifi Guy's Avatar
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    2.4 Engine Timing and Combustion Temperature

    Dave at OGTS has tried to engage me in conversations about dizzy timing curves and he's been working diligently to try to come up with a way to test and set up the proper timing curve for these engines. Apparently, a lot of our old school lessons learned on timing our 1.9/2.0 engines have to go out the window. He says that the weak 2.4 pistons are highly susceptible to burning up if timing is too far advanced. Apparently member Crilwa recently had a meltdown in his engine due to a mechanic advancing his timing too much.

    This stuff is out of the realm of things that I have any interest or skill in, so I'm going to throw this concern out here for open discussion.

    I just had a recent talk with Dave about my 2.4 engine and it's timing situation. He says that, generally speaking, do not go past 10* of advance at idle. Then he had some confusion as to what I was refering to when I said that my advance was limited to about 20* in my dizzy. I was refering to the mechanical advance limit that RallyBob limited my dizzy to when he modified it for my 2.0. I'm pretty sure that Bob said he limited it to 20*, I could very well be wrong. I believe Dave said that I could use more than that. Don't take anything I have just said as gospel, this is all just my vague recollection of topics discussed.

    But, here is what I think is Dave's main concern: Excessive combustion temperature and this condition causing the self-destruction of 2.4 pistons.

    Is there a way to tell if I'm burning too hot or too cold?

    How would one attempt to determine combustion temperature?


    Your thoughts on these subjects and other related ones greatly appreciated!



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    Bikini Inspector Frozen Tundra GT's Avatar
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    infrared thermometer and check each exhaust port.

    32-36 degrees all in at around 3500 rpms applies to most vehicles
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    Opeler
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    Temps

    Depending on your manifold you could put in an EGT gauge,it does help in tunning.
    Gary likes this.

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    Project 1450 supporter... Site Supporter RallyBob's Avatar
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    The general rule of thumb is, the bigger the engine, the less total timing needed.

    Of course it also varies greatly with modifications.

    Example: most racing 2.4's (high compression, big cam) have a total timing of 24-26 degrees. They make less power with more timing.

    A stock 2.4 indeed has a tendency to break pistons. But the pistons are notoriously weak. And stock tuning is very lean to pass emissions standards. So broken ring lands and cracked exhaust manifolds on stock 2.4's are very common.

    Gordon, if you kept total timing to between 28-32 degrees, you should be fine. You also have no lean running EFI to worry about. Nor do you have autobahn-like driving conditions to do you harm.
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    Project 1450 supporter... Site Supporter RallyBob's Avatar
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    Gordon, some more food for thought. While overly advancing the timing can certainly cause detonation which can damage your pistons, overly retarded ignition timing will actually cause HIGHER exhaust gas temps and can burn valves and melt pistons down.

    My point is, too much OR too little are equally a bad thing.
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    7,000 Post Club wrench459 (R.I.P.)'s Avatar
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    Gordo AFR and spark timing goes together.

    A wack-a-doodle video with a low compression 74 engine.:-)


    Si vis pacem, para bellum "If you want peace, prepare for war"

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    Quote Originally Posted by The Scifi Guy View Post
    But, here is what I think is Dave's main concern: Excessive combustion temperature and this condition causing the self-destruction of 2.4 pistons.

    Is there a way to tell if I'm burning too hot or too cold?

    How would one attempt to determine combustion temperature?


    Your thoughts on these subjects and other related ones greatly appreciated!


    A check of your spark plug's.......too rich would be indicated by blackened, sooty insulators. Too hot; by a hot or lean condition could be indicated by flecks like pepper. Pinging, that sound of a marbles being shaken in a can could be an indication of too much advanced timing; so too is a hard start. To some extent, your temperature gauge is something to pay mind too as well.

    One part of our engine room rounds on the bigger diesel powered boats I was on; was a check of the main diesel's pyrometer readings. Basically a temp probe mounted inside each cylinder head, read on the gauge panel; a single switch allowing you to go from one cylinder to the next, read in degrees F.... All were basically within a few degrees of each other; one cooler than the rest would indicate that cylinder was not firing for some reason. Hotter than the rest? Never recalled that condition, but it could have indicated a faulty injector spray pattern, a broken injector tip or nozzle tip or somebody done plain forgot to set the fuel rack on that baby (if she were a EMD or Detroit Diesel) wrong (it does happen!) or someone misadjusted the fuel pump setting (if on a 4 stroke Caterpillar).


    Don't sell yourself so short, my friend! I've a feeling when all is said and done, you'll have this tune-up stuff down pat cause you have more than a passing interest in it.



    Link: Tech Talk #89 – The Eyes Inside Your Engine | Reher Morrison Racing Engines
    Link: Reading 101: How to Read Your Spark Plugs - OnAllCylinders

    Mike

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    7,000 Post Club wrench459 (R.I.P.)'s Avatar
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    Quote Originally Posted by MikeNotigan View Post
    ...temperature gauge To some extent, your is something to pay mind too as well.


    Mike
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    Just Some Dude in Jersey The Scifi Guy's Avatar
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    Bob, do you remember how many degrees of mechanical advance you set my dizzy to?

    Another question for the general populace:

    How does venting our crank cases(pcv) into the carb or manifold affect engine temperatures? Hotter or cooler temps? Many side drafters vent the engine with a hose out the bottom of the car. If those gases can help reduce combustion temps, could us 2.4 dudes with sidies possibly gain a measure of piece of mind in knowing that pcv'ing to the carb or manifold is helping keep the temps down? Or do the pcv gasses increase temps?

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    7,000 Post Club wrench459 (R.I.P.)'s Avatar
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    PVC or was it PCV? is to help ring sealing.

    With to much oil vapor getting into the intake track.
    Well that will lower the orange-a-tang..octane
    Greatly raising the risk of detonation.
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    Just Some Dude in Jersey The Scifi Guy's Avatar
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    Quote Originally Posted by wrench459 View Post
    PVC or was it PCV?

    Hey, I ask the stupid questions around here!





    Your job is to give the stupid answers!



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    Project 1450 supporter... Site Supporter RallyBob's Avatar
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    Quote Originally Posted by The Scifi Guy View Post
    Bob, do you remember how many degrees of mechanical advance you set my dizzy to?
    Offhand, I seem to recall restricting it from 30 degrees to 20 degrees of mechanical advance, and deleting the vacuum advance. With your old cam and 2.0 liter engine combo, I'd have likely recommended 15 degrees BTDC at idle for a total of 35 degrees.

    With your 2.4 and stock cam, you certainly don't need as much at idle OR total timing. If you're at 10 degrees BTDC @ idle now, then you'd have 30 degrees total.

    One nice feature on the reworked distributor, the mechanical advance limits can be adjusted. I made provisions for that.
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    7,000 Post Club wrench459 (R.I.P.)'s Avatar
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    Quote Originally Posted by The Scifi Guy View Post
    ...

    Your job is to give the stupid answers!
    Sorry, bud nipping dude
    I'll try to stay inline
    How many cylinders 4-6-8
    Or the master of disaster big bore..long stroke sweet 16 cylinder?

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    Project 1450 supporter... Site Supporter RallyBob's Avatar
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    As Dan said...venting crankcase fumes (oil vapor) into the carb inlets might be great for the environment, but it sucks for performance. Oil dilutes fuel octane. That increases the chances for detonation. Which increases the chances of blowing the engine.

    I'd hook it up to a remote breather if possible.
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    Food for thought: my stock 2000 VW TDI was slowly loosing power to the point it was becoming dangerous to come up to speed entering a highway or interstate ramp. Took it to a VW shop and they advised me that the crankcase vent into the EGR tract had coked up the intake valve ports on the cylinder head to where the ports were nearly closed off. This is a common occurrence on those tdi's (nothing related to their latest tdi issues).....

    They physically scraped up and vacuumed the carbon deposits and disconnected the crankcase breather to the EGR. I've run a length of hose from the valve cover vent outside, down and out, under the chassis mounted engine cover. Tree huggers may hate me, I'll just hook up the stock set up come inspection time. One of these years I may get around to installing a proper crankcase vent/oil separator that VW never got around to doing....maybe not!

    Routing your crankcase vapors into one of your side draft barrels will eventually have the same effect as had happened to me; in addition to mucking up the one barrel bore and throttle plate with gunk.....my two cents.
    Last edited by hrcollinsjr; 04-22-2016 at 07:42 AM.

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    Senior Member Timbo's Avatar
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    My daughter's Kia Soul has direct injection. The check engine light came on and it turned out to be carbon build up on the intake valves. They cleaned out the engine and told her to use Chevron Techron at each oil change, which is a Kia recommendation. Not having the fuel in the intake reduces the natural cleaning.

    I saw this on MotorWeek. The solution seems appropriate to this discussion.

    Catch Can/Oil Separator | MotorWeek

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    Just Some Dude in Jersey The Scifi Guy's Avatar
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    Quote Originally Posted by RallyBob View Post
    As Dan said...venting crankcase fumes (oil vapor) into the carb inlets might be great for the environment, but it sucks for performance. Oil dilutes fuel octane. That increases the chances for detonation. Which increases the chances of blowing the engine.

    I'd hook it up to a remote breather if possible.

    Aaarrgghh!

    And this coming on the heels of me nuking my new dual stack screen filter to try to put a crank case vent in it!

    Dang it, this means I'll have to run 8-10' of hose out to the back of the car. I can't deal with venting to the air anywhere near the engine or passenger compartment. I can't handle the fumes. I have to spend a LOT of time in traffic to get to the good roads. Like, 20 of the first 30 minutes of my drives is spent parked at lights. I always drive with both windows down and my hood looks like Swiss cheese. If I vent to the air below the engine or passenger compartment, while stuck in traffic, it looks like I blew a radiator hose!

    I tried this earlier a few weeks ago with 6 feet of hose ending just behind the tranny. Fumes wafting in through the windows. I didn't put a vent filter on the end, though, so when I run a longer hose to at least the rear axle, I'll put one of those valve cover vent filter/breathers I showed a few weeks ago on the end. Hopefully that will congeal most of the oily fumes.

    Dang it, Dave. I wasn't even concerned about this temperature thing and now it's all I can think about! I know that your intentions were to make sure I was totally happy with my 2.4 experience and I appreciate your concern.


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    Googled PCV air/oil separator. It looks like some are using air line oil separators.

    https://www.google.com/search?q=pcv+...hrome&ie=UTF-8

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    Quote Originally Posted by MikeNotigan View Post
    Food for thought: my stock 2000 VW TDI was slowly loosing power to the point it was becoming dangerous to come up to speed entering a highway or interstate ramp. Took it to a VW shop and they advised me that the crankcase vent into the EGR tract had coked up the intake valve ports on the cylinder head to where the ports were nearly closed off. This is a common occurrence on those tdi's (nothing related to their latest tdi issues).....
    Mine at ~350K.

    Harold
    Attached Images Attached Images
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    Quote Originally Posted by Gary View Post
    Googled PCV air/oil separator. It looks like some are using air line oil separators.

    https://www.google.com/search?q=pcv+...hrome&ie=UTF-8
    Installed a PCV oil separator | Mechanical /Maintenance Forum | Bob Is The Oil Guy
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