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500, 472, 425, 368 Discussion, 500 V864 - is this even theoretically possible? in Cadillac Engine Technical Discussion; Originally Posted by big block fiero so to keep it simple I cut the throttle shaft on my two barrel ...
  1. #46
    BluEyes's Avatar
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    Re: 500 V864 - is this even theoretically possible?

    Quote Originally Posted by big block fiero View Post
    so to keep it simple I cut the throttle shaft on my two barrel throttle body.I shut off four injectors to one plane of the dual plane manifold then open just one barrel of the throttle body.
    Hmmm, interesting. Let us know how that works. Just thinking through the basic physics, I don't think it will work as well as leaving the valves closed.

    I noticed that the V8-6-4 system would limit total lift when I was looking at it first. Have you tried disassembling it to see how much room there is to alter the deactivation part? It is possible that you would be able to modify it to accept greater lift by grinding the slots deeper on the bit that is rotated by the solenoid.

    Another idea is to run it on all 8. Make it kinda like variable valve timing. Your lift would be substantially reduced and valve timing as well. Only thing I would worry about is that the rocker would be slamming into the deactivation parts since the valve would only start opening mid-way through the cam ramp when the lifter is really moving. Basically you'd be bypassing the opening/closing ramps on the cam like having the valve lash super-loose. It's a thought, but use at your own risk...

  2. #47
    big block fiero is offline Cadillac Owners Member
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    Re: 500 V864 - is this even theoretically possible?

    It is true that my deactivation method doesnt create a good air spring hence not able to deliver the fuel economy of a system that closes the valves. If someone figures out how to increase the travel (ive studied it and it would be a tough complex job) I would like to purchase a rocker set and i have cores.If theres enough travel there would not be any slamming effect when the valves are closed making an air spring and with the valves turned on the motion would use the ramps of the cam.

  3. #48
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    Re: 500 V864 - is this even theoretically possible?

    Quote Originally Posted by big block fiero View Post
    Mine also has purpose for the car to sound like it has a four cylinder motor because my 500 caddy motor is concealed and the car looks stock.
    Why not use a large sound system with a recording of a Honda with coffee can exhaust? Put a couple Electrovoice horn speakers in back of the grille.

  4. #49
    big block fiero is offline Cadillac Owners Member
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    Re: 500 V864 - is this even theoretically possible?

    I have discovered that altho the fulcrum travel is only 1/4" that is enough to accomodate .520 lift and even a little more so I am back on this project with the airspring feature as of 4/8/07

  5. #50
    danomac is offline Cadillac Owners Member
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    Re: 500 V864 - is this even theoretically possible?

    I actually own an 81 Coupe DeVille with the V864. If you can get everything to fit mechanically you'll have to find someone to hack/reprogram the ECU. When it goes into 4 or 6 cyl modes the dead cylinders do act like an air spring. After one full 4 stroke cycle finishes then it operates like an air spring.

    6 cylinder mode does indeed shake a little bit, but with bad motor mounts it feels much worse. They couldn't do much for the balancing in 6cylinder mode.

    The system monitors engine load and speed and the 3rd gear switch on the transmission. Most people that hate the system put a switch on the dash that breaks the circuit to the switch on the transmission as the system will only operate when it's in 3rd gear.

    The other problem is fuel metering - with more displacement you'll need more fuel. The ECU also compensates for different cylinder modes (it lowers the amount of fuel being delivered depending on which mode it is in) so that would have to be reprogrammed for the displacement as well. This is why I mention reprogramming the ECU.

    Edit: The best mileage I've recorded was 24.3 MPG on a 600km trip. My last trip I was a little more heavy footed and I still kept it around 19-20MPG.

  6. #51
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    Re: 500 V864 - is this even theoretically possible?

    Actually, any modern fuel injection system shouldn't have much problem handling the cylinder shutdown. If you switch off the ground wires to the injectors that feed the deactivated cylinders then there will be no fuel going there and the computers feedback system (through the O2 sensor) should manage injection to the remaining cylinders and keep the mixture correct. Of course, this system would rely on a manual switch to go into 4 cylinder mode. I think that everybody converting to this has given up on the 6 mode, as has GM with their current cylinder deactivation system. There are vacuum switches available though that could make the system automatic if one wanted to work with that. Look for a torque converter lockup kit.

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    danomac is offline Cadillac Owners Member
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    Re: 500 V864 - is this even theoretically possible?

    The system on my '81 is far from modern... throttle body with 2 big injectors... I doubt that it just turns one completely off.

    Most modern fuel injection systems will balk if you break the circuit at the injector. They'll set a failure code and go into limp-mode. I wonder if aftermarket EFI could be programmed to deal with this.

    There are set limits that the ECU can adjust the mixture. Outside of that the fuel maps need to be reprogrammed. We're talking a fairly large jump in displacement for the stock system (368 -> 500) so it wouldn't run properly. That's all I was saying.

  8. #53
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    Re: 500 V864 - is this even theoretically possible?

    Who's talking about using the stock injection system? I had thought pretty much everyone wanting to swap on the cylinder deactivation system was using a carb or aftermarket EFI anyways and a manual switch for deactivation. You are right about the factory EFI being pretty poor on that car (slow processor speed), and that is one of the big reasons attributed to the system not being very successful. Obviously the deactivation idea is quite valid as it is widely used today (finally!).

    Cutting out half the injectors would definately set an error code, but the rest of the computers inputs would still register in the normal range so it should be able to cope just fine. Most error codes do not trigger limp mode, which is why you see so many people driving around with a check engine light that comes on occasionally and never do anything about it (not that I advocate this!) The GM ECU's are pretty throughly hacked, so adapting a system off of a TBI equipped truck (the 454 motors would be ideal) to a Caddy would not be that big a feat and has some distinct advantages over an aftermarket EFI system.

    If using TBI and you limit it to 8-4 operation. Just cut one injector - the way a dual plane intake is made each injector feeds four cylinders. The four that get cut are either being fed by one plane of the intake or the other. So in 4 cyl mode you would just have one side of the intake go 'dead'. No air would be moving through it (valves closed) and no fuel in it (injector off). This is why I say that the original system probably cuts one injector (under four cylinder operation). It is the absolute easiest way to achieve the goal. The fuel requirements of the other four cylinders have not changed at all, so the original map should be fine. If things are slightly off, the O2 sensor will tell the computer and it should trim mixture accordingly.

    Six cylinder mode would be difficult to achieve with TBI (aside form the '81 system) because you would want to run one injector normally and the other at half rate. But the computer on most TBI systems wouldn't know this, so it would be running both injectors at 3/4 rate and two cylinders would be running with 50% more fuel than they need and the other four would be getting only 75% of what they want. Pretty crappy way to run. Probably could be fixed with some programming wizardry, but note that the modern deactivation systems have dropped the six mode entirely.

    For point injection, the principle is the same but here 6 cyl mode could actually be achieved easily except for that pesky vibration thing. You cut air and fuel to two or four cylinders and the other cylinders really don't know what has happened. They are still drawing in their air charge and getting the fuel they need because the computers feedback system keeps the a/f ratio correct and fuel is being injected to each cylinder individually instead of to groups of cylinders.

  9. #54
    danomac is offline Cadillac Owners Member
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    Re: 500 V864 - is this even theoretically possible?

    Eh, I thought someone mentioned the stock system. My memory sucks bad though, and I don't feel like reading the last 6 pages of posts to find out.

    In the case of using a different EFI on the car and cutting the circuits to the injectors, may as well put a piece of tape on the check engine light.

  10. #55
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    Re: 500 V864 - is this even theoretically possible?

    ok guys sorry i havn't posted in a long time.

    i was going to simply install the 368 heads i have onto my 500 so that i could try 4 cylinder mode (sure it wasn't going to have as much power but i had to try) but i ran into a little problem

    the gaskets for the 368 heads leave some of the gasket exposed to direct flame because the 500 bore is so much bigger and the 500 gasket doesn't cover up some of the water jacket passages and burning lots of water doesn't work so well

    so does any one know 1. if the gasket will handle open flame?
    2. if i could make it do this somehow how long

    3. where can i get some custom gaskets made without spending a fortune(is there a way to make your own?)
    4. if there has been any progress made with the adapter plate to allow this hardware to be put on 500 heads

    5. how does this system work( i know how it works in principle but i cant see how the solenoids keep the valves from opening i just dont want to spent money on blind faith i want to see how this functions

    any input appreciated thanks

  11. #56
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    Re: 500 V864 - is this even theoretically possible?

    I'm not sure I can help on the headgasket, but I do know that some engines have copper headgaskets available. It seems that a copper gasket could have the bore cut out larger. The downside is that I have heard copper gaskets are more tempermental to sealing - they want a very flat surface, some sort of sealer is usually used and retorquing the gasket may be necessary.

    As for the rockers, it's pretty simple. Look carefully at the fulcrum of the rocker arm and specifically the part that is turned when the solenoid engages (you can push it in by hand) and the slotted plate beneath it. Under normal running, the raised areas on the part controlled by the solenoid line up with the solid areas of the plate beneath it so the rocker functions normally. When the solenoid rotates the part, the raised areas come over the slots in the plate beneath it. When this happens, the fulcrum of the rocker arm is free to move upwards when the pushrod moves upwards. What happens is that the entire rocker arm pivots at the valve tip and the valve never sees enough pressure to open it. There is a reasonably strong spring at the rocker funcrum so it is a bit hard to do this by hand, but that spring is needed to provide some downward pressure on the lifter so it stays in its bore.

  12. #57
    eldrewado is offline Cadillac Owners Member
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    Re: 500 V864 - is this even theoretically possible?

    well i figured out how to get the 368 heads not to leak water but it is a moot point because i have been told ( and suspected) that they will create so much pumping loss that i wont just lose power ill be losing mileage as well.
    it looks like making the system work on 500 heads is the only way.
    oh i read this and as i understand it, it wont work

    "If using TBI and you limit it to 8-4 operation. Just cut one injector - the way a dual plane intake is made each injector feeds four cylinders. The four that get cut are either being fed by one plane of the intake or the other. So in 4 cyl mode you would just have one side of the intake go 'dead'. No air would be moving through it (valves closed) and no fuel in it (injector off). This is why I say that the original system probably cuts one injector (under four cylinder operation). It is the absolute easiest way to achieve the goal. The fuel requirements of the other four cylinders have not changed at all, so the original map should be fine. If things are slightly off, the O2 sensor will tell the computer and it should trim mixture accordingly."

    in saying that the requirements of the other 4 cylinders havnt changed you are correct but the dual plane intake feeds the right and left side separately, right? But the engine makes a v4, not an inline 4 in deactivation mode so cutting off one whole side would mess it all up. i would go with a carb but im using port efi for other reasons so now i have more to deal with but it shouldn't be too hard, once i spend alot of money that is hehe

  13. #58
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    Re: 500 V864 - is this even theoretically possible?

    Quote Originally Posted by eldrewado View Post
    but the dual plane intake feeds the right and left side separately, right?

    Nope. The dual plane intake feeds every other cylinder in the firing order from each side. Basically, it works perfectly for how the V4 mode is implemented.

  14. #59
    eldrewado is offline Cadillac Owners Member
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    Re: 500 V864 - is this even theoretically possible?

    upon closer inspection, it seems i am wrong. it does seem that the intake feeds the cylinders in that manner. i stand corrected.

  15. #60
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    Re: 500 V864 - is this even theoretically possible?

    This thread has been going on forever. You folks have reached the BIG issue. All the factory intakes will not behave properly in the 4 cylinder mode except for the factory 8/6/4 intake. Take a look at one sometime. Quite interesting as are the exhaust manifolds. You want performance from a 500 and then economy by making it a 250. That cannot be done with the big intake. One has to suffer. Either use the puny plumbing from a 368 or the stuff from a 500. Of course the 368 intake will limit power with the 500. Maybe there is a way around this... Another issue is to see exactly what the modulated displacement does to modulate the EGR valve while activating cylinders. A very nasty ping happened on 8/6/4s when cylinders were turned on.
    Seems like an overdrive transmission would be a proven way of increasing fuel economy and making it pay off. Still it would take a long time to recoup all the $$$ unless it is a daily driver.

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