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Thread: Question for Engine and Timing Expert

  1. #1
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    Question for Engine and Timing Expert

    I have two Subaru EZ30 engines bolted together. One is at TDC on cylinder one and the other is TDC cylinder six. They fire at the same time. I did this thinking it would Balance or cancel each other out for smooth running. The engines have a bad vibration. I don't think it is the connector as it includes two flex plates bolted together rim to rim. I'm thinking that the detonation is pushing the rear engine to the right and the front engine to the left and causing the vibration. Does this sound right?


    If it would be better to have cylinders on the same side firing, here is my dilemma. The connector to the flex plates has the eight bolts like the flex plate. I could only rotate it 45, 90 and 135 degrees. I have heard that rotating one engine 30 degrees would put that engine out of sync with the other one so I could fire one cylinder at a time out of the 12 cylinders. If 30 degrees Is the Odd number, then would 90 get me into the same predicament?

    If so, I have to modify the connector$$$ or brace the two engines better to the chassis. There might be some play. What do you guys think?

    Thanks,

    Jack

    https://www.youtube.com/watch?v=bBsSs8bPrO8

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    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by JB91710 View Post
    I have two Subaru EZ30 engines bolted together. One is at TDC on cylinder one and the other is TDC cylinder six. They fire at the same time. I did this thinking it would Balance or cancel each other out for smooth running. The engines have a bad vibration. I don't think it is the connector as it includes two flex plates bolted together rim to rim. I'm thinking that the detonation is pushing the rear engine to the right and the front engine to the left and causing the vibration. Does this sound right? If it would be better to have cylinders on the same side firing, here is my dilemma. The connector to the flex plates has the eight bolts like the flex plate. I could only rotate it 45, 90 and 135 degrees. I have heard that rotating one engine 30 degrees would put that engine out of sync with the other one so I could fire one cylinder at a time out of the 12 cylinders. If 30 degrees Is the Odd number, then would 90 get me into the same predicament? If so, I have to modify the connector$$$ or brace the two engines better to the chassis. There might be some play. What do you guys think?
    Thanks,
    Jack

    https://www.youtube.com/watch?v=bBsSs8bPrO8

    Jack,

    If I understand correctly, you are using a single ecu set up for a 6 cylinder:

    coil 1a and 6b are connect to the same ECU output.
    coil 6a and 3b " " " "
    coil 3a and 2b " " " "
    coil 2a and 5b " " " "
    coil 5a and 4b " " " "
    coil 4a and 1b " " " " Is this correct?


    The Subaru engines are inherently balanced with the same number of pistons going out and back at the same time.


    During the power stroke the pressure in the cylinder is pressing equally against the head and the top of the piston. so that should not cause vibration.


    Your engine fires every 120 degrees. So any flywheel coupling change would have to be 120 or 240 degrees with associated wiring change.


    If I were you, I would disconnect fuel injector and pull the plugs on each engine individually. This will make sure the each engine runs smoothly on its own.


    To make your front engine run smoothly. You should probably use a flywheel off a manual transmission. The flexplate with out a torque converter is not heavy enough to maintain smooth rotation between power strokes.
    Bob
    Last edited by Bob_n_Cincy; 09-30-2018 at 03:13 AM.
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    Hi Bob,

    Thanks for you quick and thorough reply. That means you are a thinker and the expert I was looking for.

    1. The timing is as you stated.

    2. I originally started just the rear engine and had no vibration. I knew about the equal pressure cancelling a lateral movement but thought having the engines detonating on opposite sides at the same time might have caused the vibration.

    3. I don't have a 120 degree adjustment so that would mean grinding off one of the flanges, making a new one and welding it on so I had the pistons detonating on the same side at the same time. But, if Neither engine is vibrating separately, would there be a vibration if they are connected?

    4. The computer gets information only from the rear engine so I don't know if the front engine would even start. If it did start, I could remove the rear engine's spark plugs and injector wires to eliminate compression and just let the front engine run to see if it vibrates. But, that won't tell me if it's the engine or the flex plate and connector causing the vibration.

    5. When I took a quick look at the flex plates spinning, I couldn't tell if there was a misalignment but I imagine a tiny misalignment could make a big vibration at speed.

    6. I have the flex plates bolted together Rim to Rim which would make both stronger than just one alone but maybe not enough. If there is no misalignment, then there wouldn't be any distortion in them while they were spinning.


    I'm thinking it has to be a misalignment in the connector but the only parts that are not machine shop perfect, is the alignment of the flex plates to each other. They touched together and aligned perfectly by eye when I assembled them but maybe a minute amount could make a big difference when rotating. More than the flex plates could absorb.

    Jack20180911_112039.jpg20180911_112039.jpg
    Last edited by JB91710; 09-30-2018 at 02:00 PM.

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    I expect it would take very little misalignment in your coupling to introduce vibration. If it varies in intensity or simply gets worse with RPM rise that would suggest it's at fault. You might look into trying to measure statically. That is in the following test, if it is even slightly off I'd think you could detect the blocks deflecting. Loosen engine mounts on one engine to allow as free of motion in the block as it "wants". Clamp the 2nd engine so it should not move in the mounts. Setup dial indicator on the loose block near a mount, then rotate the shafts working from the fixed engine end so your torque to turn the shafts is kept on that engine mount. I've done things like this on a small scale when setting up miniature electric motor dyno's that I used to build and sell. I'd think it would work on any size machinery. If there is a wobble being introduced into the second block you have something to look into. If nothing happens - I wonder if you need more flywheel. Each motor I would think would need flywheel mass equivalent to what it would have alone, i.e, total mass in the ballpark of 2 engines' flywheels. (guessing)

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    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by JB91710 View Post
    But, if Neither engine is vibrating separately, would there be a vibration if they are connected?
    Should not be.

    When you say "separately", you mean engines are coupled together and only one engine has ignition. Correct?

    Quote Originally Posted by JB91710 View Post
    4. The computer gets information only from the rear engine so I don't know if the front engine would even start. If it did start, I could remove the rear engine's spark plugs and injector wires to eliminate compression and just let the front engine run to see if it vibrates. But, that won't tell me if it's the engine or the flex plate and connector causing the vibration.
    No reason the front engine shouldn't start. If there is no vibration in front engine. Then I would suspect that the TDC on the 2 engines are not exactly matched.

    Are you using solid motor mounts? How do you know the tdc is a perfect match between the 2 engines?
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    I was thinking of loosening the front engine motor mounts and just turning the motors over without the fuel pump on to see if the front engine would self/vibrate align. Like I said., the rims of the two flex plates lined up laterally and the rims touched all the way around when brought together. I figured 1/32 or less would be picked up by the flex of the plates unless they have stiffened each other by bolting them together My original plan was to make a custom flex plate like in the photo s I would have lots of flex. Then I thought about the flex plates and dropped that idea. Maybe I should cut out equal and balanced sections of the rim to make it much more flexible.

    Engine coupler5 001.jpg

    I wanted to use the items in the photos but it's not like you can just go down to the Hardware store to size and fit. I don't have much room in there anyway.

    [ATTACH=CONFIG]94471[/ATTACH Lovejoy.jpg
    Attached Images Attached Images

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    Quote Originally Posted by Bob_n_Cincy View Post
    Should not be.

    When you say "separately", you mean engines are coupled together and only one engine has ignition. Correct?

    If the engines on their own are well balanced, could bolting two together with cylinders firing on opposite sides cause a vibration? I don't think it's that as the most obvious answer which is connector misalignment makes more sense.



    No reason the front engine shouldn't start. If there is no vibration in front engine. Then I would suspect that the TDC on the 2 engines are not exactly matched.

    Are you using solid motor mounts? Yes. The blocks are bolted to the frame.

    How do you know the tdc is a perfect match between the 2 engines?
    I don't know if it's Perfect but I think it's close. I checked it two ways. With a shaft against the piston as it went through it's cam lull and brought it back to the center. Then I checked the timing mark and found it to be 120 degrees off of the 0 mark. Between the two I can't imagine being off by a couple of degrees. Do you think that's close enough?

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    Senior Member Bob_n_Cincy's Avatar
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    Jack
    By spinning the 2 engine together. With one engine having ignition at a time. You can determine if it is a mechanical induced vibration or a electrical induced vibration.

    This test will also check the wiring of the front engine. This test is an hour project. Well worth it to see if everting in the front engine is operating correctly.
    post a video so we can see or hear the vibration.
    Bob
    Last edited by Bob_n_Cincy; 09-30-2018 at 09:59 PM.
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    Senior Member Bob_n_Cincy's Avatar
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    Jack
    when driving HARD, the engine has a lot of forces going on. Watch my yellow oil fill cap in this video.
    Bob

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    You have to have soft motor mounts!

    The video I posted at the beginning shows stuff vibrating in front of my thigh.

    I'll try the test by taking out the plugs and disconnecting the injectors on the rear engine that I already know is running vibration free.

  11. #11
    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by JB91710 View Post
    You have to have soft motor mounts!
    The video I posted at the beginning shows stuff vibrating in front of my thigh.
    I'll try the test by taking out the plugs and disconnecting the injectors on the rear engine that I already know is running vibration free.
    Yes I had soft OEM engine mounts during that video. I have switch to harder rubber aftermarket mounts.

    I watched your video a couple of times and don't see what your talking about. Can you take a screen shot and circle where to look.

    To do this project correctly. The 2 engines should me mounted together solidly. The way an engine mounts to a transmission. I realize that would take much more engineering and a pretty expensive one off adapter.


    I designed an adapter to go from a 200hp electric motor into a Allison transmission.
    BalqonEqo_drive.jpg

    Bob
    Last edited by Bob_n_Cincy; 10-01-2018 at 09:53 AM.
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    Any specific reason you chose to pair 1 & 6? I would pair the partner cylinders, 1&2 instead. Line them so #1-F fires when #2-R fires.
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    Then rear engine is set at TDC on 1. The front engine is at TDC on 6. The next cylinder in the firing order. Then I spliced the coil and injector wires like this.

    coil 1a and 6b are connect to the same ECU output.
    coil 6a and 3b " " " "
    coil 3a and 2b " " " "
    coil 2a and 5b " " " "
    coil 5a and 4b " " " "
    coil 4a and 1b " " " "

    I wanted to have one fire on each side at the same time thinking it would reduce vibration rather than have both 1's firing at the same time.

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    When I stand next to the car, watch the tools and materials jumping around and rolling against my thigh. I don't know what is a lot or a little vibration but there was None when only the rear engine was running. Ill get you some videos tomorrow. I was working on a possible way to make some Money today.

    The photos below show how I made the motor mounts. I cut the long tube after it was welded where there was engine interference.

    100_0167.jpg 100_0174.jpg 100_0187.jpg

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    I understand about wanting them firing on opposite sides, but pairing partner cylinders would also accomplish this, in addition to placing both crankshafts in the same position.
    The Undead Gearhead, back from beyond the grave

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    To do this project correctly. The 2 engines should me mounted together solidly. The way an engine mounts to a transmission. I realize that would take much more engineering and a pretty expensive one off adapter.


    I figured I would be connecting them firmly through the chassis mounts but maybe not. I have to determine if the connector is good before I reinforce the mounts or the misalignment will send the vibration into the internal engine parts.

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    Quote Originally Posted by JB91710 View Post
    I have to determine if the connector is good before I reinforce the mounts or the misalignment will send the vibration into the internal engine parts.[/B]
    Mount a dial indicator to one engine and measure the movement of the other engine as you turn it over (pull the plugs) If it's true, you won't see movement.
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  18. #18
    Senior Member UnhipPopano's Avatar
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    Static alignment is only good while the car and engines are at rest. When the car is in motion, and the engines are not fixed together, the alignment will be all over the place. I would also be worried that the two engines will have common natural frequencies, and that will work against you. On the other hand, if you tie the two engines together, you might have a problem with stresses on the blocks, and where would you then put the engine mounts?

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    What are Partner Cylinders? Remember, I really don't know anything!

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    I'm going to look at the mount bracing and then the connect alignment and start the front engine only. If there is no vibration then the connector should be OK and it will probably be caused by the two engines running against each other harmonically. I'm thinking this may become a single engine car like all the other 917's. It will just have a spare sitting in front of it. Sure does sound better with 12 cylinders.

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    Quote Originally Posted by JB91710 View Post
    What are Partner Cylinders? Remember, I really don't know anything!
    Partner cylinders are the two cylinders in the engine in which the pistons are always in the same position - top, middle or bottom of the stroke - so on yours, when #1 is TDC compression, #2 is TDC overlap.
    This essentially puts the engines in as close identical sync as possible without firing on same sides, your crankshafts will be in the same position on both engines. NOT saying this WILL eliminate your vibe, but it might, and seems more mechanically harmonious to me.


    This idea may actually require the use of two ECU's. IF you did, you could stagger the second engine 60 degrees off the first and get a true 12 cyl input.
    Last edited by Brad Smith; 10-02-2018 at 02:36 PM.
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    Quote Originally Posted by Brad Smith View Post
    Any specific reason you chose to pair 1 & 6? I would pair the partner cylinders, 1&2 instead. Line them so #1-F fires when #2-R fires.
    "I understand about wanting them firing on opposite sides, but pairing partner cylinders would also accomplish this, in addition to placing both crankshafts in the same position." I didn't understand what you were saying and at the time, I wasn't interested in changing things anyway. NOW, I Have to.

    Brad I didn't know much about engine firing order and the mark on the pulley vs cylinder positions. When you mentioned what you would have done, I didn't know why. Last night I put on my thinking cap and realized what you were talking about. 1 & 2 are on the pulley mark so I couldn't go wrong with timing like I may have on 6. When I realized it, it sounded familiar so here I am. Tomorrow I will set the front engine on 2 but then I have to figure out how to bolt the flex plates together as the holes will not line up. I think I fixed the vibration by raising the rear engine with washer shims. For some reason years ago I had welded washers on the front engine mounts and that threw things off.

    So hopefully, I might have the engines running smoothly and vibration free by the end of the day.

    Thanks for your input.
    Last edited by JB91710; 10-07-2018 at 05:42 PM.

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    Senior Member Bob_n_Cincy's Avatar
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    Jack
    did you ever run the front engine buy itself?
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    Quote Originally Posted by Bob_n_Cincy View Post
    Jack
    did you ever run the front engine buy itself?
    Yes I did. The rear engine made so much noise with the plugs out I was afraid I was damaging something so I shut it down quick.

    I have since set the front engine on cylinder 2 and the rear is still on 1. I started the engines and the exhaust note sounded rough, definitely Not like a 12 cylinder. The exhaust temperature on the rear engine was 380 and the front was 110. I can't catch a break!

    Now that I'm sober again, ;-), I'm going down to check the TDC marks and inject compressed air into the R1&F2 cylinders to check for leakage and Test the spark wire splicing to each pair of spark plugs with the computer checking tool. I can't test the injectors as the pin holes are very small but I'll still try something. Murphy's Law is definitely in play.

    The heck with it. I'll go there Monday. It's hard to actually Plan to walk into disappointment! I have to put my mind in a failure mode so the fall isn't so far. I've fallen very far and many times in the last month. Every throw up Just because of stress?
    Last edited by JB91710; 10-14-2018 at 12:45 PM.

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    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by JB91710 View Post
    I have since set the front engine on cylinder 2 and the rear is still on 1.
    Jack
    what do you mean: "I have since set the front engine on cylinder 2"
    How did you do that?
    Bob
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    Quote Originally Posted by Bob_n_Cincy View Post
    Jack
    what do you mean: "I have since set the front engine on cylinder 2"
    How did you do that?
    Bob
    With the engines disconnected, I rotated the front engine until the pulley notch was on Zero. Then I blew compressed are into cylinder Two and no air came out the exhaust or throttle body. I did the same on the rear engine for cylinder One. Then I reconnected the flex plates. As of 2:20 today, I haven't gone down there to look for the problem. It's hard when you KNOW you are going to get it right between the eyes again.
    Last edited by JB91710; 10-15-2018 at 01:21 PM.

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    Do we KNOW for a fact that two engines can be run off of one ECU?
    The Undead Gearhead, back from beyond the grave

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    Quote Originally Posted by Brad Smith View Post
    Do we KNOW for a fact that two engines can be run off of one ECU?
    I've always asked that question and a number of people including Megasquirt said they should. My Common Sense says, If a cylinder gets fuel and then a spark, it should fire.

    Most of the sensors are for tuning and the rear engine crank sensor is telling the ECU when to fire and where the throttle is at.

    I was worried about the signal weakening when it was split but I think that has been put to bed. I have run a computer test to see if both cylinder coils on a splice fire a spark and they do.

    I started the engines separately and it ran.

    When I go back in there I have to check the TDC's for R1 and F2 again, and test the spliced coil firing. Kind of hard to test the fuel injector signal.

    Why, would I have 380 vs 110 temps between engines?

    When I start the engines, both my VDO pressure gauges with matching senders peg at 100 Ibs. Is this from a grounding problem?

    I think it was running on all 12 cylinders here but I had to do some work to correct a vibration. After that things went downhill.

    https://youtu.be/bBsSs8bPrO8
    Last edited by JB91710; 10-15-2018 at 02:59 PM.

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    "I've always asked that question and a number of people including Megasquirt said they should."
    I've seen enough things that look great on paper but don't fly in application to be skeptical of anything that SHOULD...just throwing it out there.

    I would compare the crank sensor signals simultaneously on an oscilliscope to be sure the signals are EXACTLY in sync...if the "dumb" engine is +or- 5 degrees, it's ignition timing will be that far off. Honestly, I think running twin ECU's might be less work.

    Exh. temp difference could be result of off timing/fuel mixture. What pressure is your gauges measuring?
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    "I think running twin ECU's might be less work."

    $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

    Plus, two computers would be just one more coordination problem.

    The ECU is only getting a crank signal from the rear engine. The TDC marks both engines being on Zero would put the engines in sync, right?

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    Why would it be super expensive?
    What would have to be coordinated beyond the throttle? Each ECU manages 6 cylinders, each set with it's own inputs.
    In sync by EYE standards, sure. But these will need to be EXACTLY in sync, or ignition timing will be off. But it's still running one engine off of a different engine's vital signs. They are NOT going to be exactly the same at the engine management level.
    Make sense?
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    This was never intended to be a Race Winner. I just wanted it to run good. I'm beyond broke so another computer is out of the question. The next owner can upgrade the car any way they want.

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    Quote Originally Posted by JB91710 View Post
    I'm thinking this may become a single engine car like all the other 917's.
    Hey Jack.
    From my experience of building a kit car. Once the engine is running you are only 2/3rds done with the car. You still have to sort out braking, suspension, and body. The dual engine setup has consumed all you energy for more than a year now.

    Below is just a suggestion from me. You can do what you want.

    Remove the coupler from between the 2 engines. Just run it on the rear engine. Temporarily just forget about the front engine. Move on to getting everything else on the car done. This will at least give you the sense that you are accomplishment. You need this to give yourself the motivation to work on the car.

    Once everything else is running, then you can drive it around an have some fun in the car.
    At that point, make the decision if you really need twelve cylinders.

    Trying to solve your problem's on a forum, you get "too many cooks in the kitchen". There are multiple ways to "skin this cat". All the advice on this forum is pretty good, but the tough part for you is deciding what path to follow.
    Good Luck,
    Bob
    Last edited by Bob_n_Cincy; 10-16-2018 at 12:55 AM.
    818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
    My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
    My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread

  34. #34
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    Bob,

    I have already done what you said. The last thing on the car itself is cleaning up the wiring. I can't do that until I am sure What the wiring IS! I've also been trying to get a switch, fuse, relay etc., wiring diagram for my simple application to no avail. I've been waiting for another engine wiring harness and the body side connectors to help clean things up, for what was supposed to take one week and it's been a month.

    The last Biggy is finishing the body work and painting it which is going to be real tough emotionally with the engine problem hanging over my head. I lost my Cheap painter so I'll have to do that myself also. It also means Completely transforming the garage into a body shop.

    Everybody says, "Finish it as a 6 cylinder car with a extra engine" but that is REALLY hard for ME to wrap my head around as the plan was for the car to be an authentic replica. To me, putting a 6 cylinder engine into a Porsche 917 just doesn't compute and will be Much harder to sell that way. This is my Retirement money now, not a toy.

    I'll keep testing things to find out what the problem is until my head tells me to give up.

    Thanks for all your help,

    Jack

  35. #35
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    Well, I had the engine running great on 12 cylinders https://www.youtube.com/watch?v=bBsSs8bPrO8 but that just created more issues that I don't have the money or emotions to deal with. I'm going to finish the car as a 6 cylinder 917 like everyone else. I'll clean up the wiring, finish the body and paint it. Then I have to sell it. I won't even get to enjoy it.

    Does anyone have a wiring diagram for the 818R? I need to figure out what goes where. The Basics like.....well.....everything!

    Does 5v go to a switch which goes to a relay which powers a 12V appliance?
    Can 12V go through a switch to anything?
    What size fusses are needed for what?

    I have a fan on the radiator which I imagine gets powered by a relay.

    My inline brake light switch gets 12v in and a wire to the lights. Of Course, when I hit the brakes the lights don't come on. Yes, they are grounded.

    It's the Theory of what goes where and why that I need to create a picture in my mind.

  36. #36
    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by JB91710 View Post
    the plan was for the car to be an authentic replica. Jack
    How was it going to be an authentic replica? The original car was a flat 12 engine and yours is 2 flat 6s coupled together?

    How much do you think you can sell it for with one 6 cylinder working, without doing anything else to the car?
    How much with both engines working?

    I personally am not interested, I just started a 21 acre mountain top project this fall.
    Bob
    818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
    My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
    My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread

  37. #37
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    Quote Originally Posted by Bob_n_Cincy View Post
    How was it going to be an authentic replica? The original car was a flat 12 engine and yours is 2 flat 6s coupled together?

    How much do you think you can sell it for with one 6 cylinder working, without doing anything else to the car?
    How much with both engines working?

    I personally am not interested, I just started a 21 acre mountain top project this fall.
    Bob
    Thanks for those Uplifting and Positive questions! It's not like I'm in a stressful enough place in my life. You Just Ruined my day! Good luck with Your project!

  38. #38
    Senior Member Bob_n_Cincy's Avatar
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    Quote Originally Posted by JB91710 View Post
    Thanks for those Uplifting and Positive questions! It's not like I'm in a stressful enough place in my life. You Just Ruined my day! Good luck with Your project!
    Jack,
    I'm sorry if I discouraged you with my questions, that was not my intent.

    Here is a link to my schematics.

    https://1drv.ms/f/s!AjxmxU-yAwK9hXL_Hxt5j4vJxVv0

    Bob
    Last edited by Bob_n_Cincy; 10-20-2018 at 01:22 AM.
    818S #22 Candy Blue Frame, Front Gas Tank, 2.5L Turbo, Rear radiator, Shortened Transmission, Wookiee Compatible, Console mounted MR2 Shifter, Custom ECU panel, AWIC soon
    My Son Michael's Turbo ICE Build X22 http://thefactoryfiveforum.com/showt...rts-818S-Build
    My Electric Supercar Build X21 (on hold until winter) http://thefactoryfiveforum.com/showt...e-Build-Thread

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