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Hamish Janes

Fiat Uno Turbo triggers

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Hi all. I'm wiring a G4+ to a 1301cc Uno turbo. It runs a reluctor type crank sensor off the crank pulley which has 2 teeth and also another reluctor type sensor which takes its signal off the flywheel ring gear teeth. At this stage I'm unsure how many teeth are on the ring gear. From another post I read, I can use the crank sensor only which isn't ideal and I'll need to run large dwell on cranking. My question is, can the other sensor reading the ring gear be used as the sync. Or any ideas? Worst case is I convert a 4age 20v dizzy to suit. Thanks in advance. 

I should also add that even though my profile says NEWBIE, I have extensive experience with these ecu's.

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Ring gear can not be used as sync.  Best option would either to be keep the 2 teeth or install a multitooth/missing wheel. (36-1 or 60-2) on the crank.

  Dizzy triggers are not a good solution (only good for sync).  If you want full sequential you need to have a sync trigger on either the camshaft or the dizzy.

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Best option would either to be keep the 2 teeth

Two teeth on crank alone will not be enough for the engine to run (unless it is single coil with a distributer), since it will not know which tooth is cyl 1&4 and which is 2&3.

If you want to do direct ignition or wasted spark you will need to change either to a crank trigger wheel with missing teeth (would allow wasted spark) or you could stick with the two tooth wheel but you would need to add a single "sync" tooth to the camshaft or distributor (would allow seq or wasted spark).

 

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Thanks for the replies. The engine does run just 1 coil but would be ideal to have individual injection and at least a wasted spark setup. 

I can install a crank trigger wheel to the front of the crank pulley but will this give me what I need for this? I could squeeze the very large 58/60 wheel on or ideally the smaller 24 tooth wheel. 

 

Thanks again

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For sequential injection and direct spark ignition you will want a cam sync pulse in addition to the crank mounted multitooth missing pattern. The cam sync pulse should be a signal tooth.

Scott.

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Thanks Scott. I'm getting a bit confused here, this is nothing like the simple Toyotas I'm used to. The dizzy is just that, a distributor, no sensor inside. From factory this thing runs just the two crank sensors. So am i correct in thinking that my 2 tooth crank wheel is useless? Am I needing to install the 24 tooth wheel to the crank pulley and also somehow fit a 1 tooth wheel to the cam pulley? Is this my only option for direct spark and sequential injection?

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Actually, flag that, I do understand. I'll buy a 24 tooth wheel and fit it to the crank pulley. I'll run two groups of 2 injectors and single coil with distributor as per factory. I take it I'll need to remove a tooth from the new 24 tooth wheel for tdc? Or can I use the original 2 tooth wheel and sensor for tdc and the new wheel and sensor for position? 

Edited by Hamish Janes

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Hi Hamish,

Removing one tooth from a multi-tooth crank mounted trigger wheel would make the most simple setup, you would then not need your original 2 tooth crank pattern. However do not use a wheel with 26 teeth, as the total number of teeth (including missing ones) needs to divide evenly into 360. So you could have a 12 or 24 tooth wheel and remove one tooth from this.

Scott

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Next question. I have a 36-1t trigger wheel on the way which I will mount to the crank pulley. When lining up the wheel, should the middle of the the missing tooth section should line up with the middle of the sensor at TDC? Is this the same with the cam trigger? Im an Auto Electrician and feel I am putting myself out there with these possibly obvious questions but this is the first time I have had to install trigger wheels. Diagnostic work is a different ball game to setting this sort of stuff up. Thanks

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On a 4 cylinder the ideal location for the missing teeth to pass the sensor is somewhere near 90° BTDC (or 90 ATDC is good too).  In reality it will work pretty much anywhere with an engine like yours but the suggestion of 90 deg will give the most reliable detection under conditions when crankshaft speed variation is worst such as cranking when you have a flat battery.  As the piston approaches TDC the crank "slows down" and that can make it more difficult to detect a missing tooth if it is near TDC.

If you are going to have a single sync tooth on the cam as well then the only rule for this one is you don't want it occurring at the same time as your missing tooth.

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Thanks Adam. Is there information about this anywhere? I thought the idea of the missing tooth was to signal TDC, same with the cam? Or am I right in thinking that with a Link, the ecu just needs to see a signal gap (missing tooth). If the missing tooth is at 90 BTDC, does the ECU have a programmable offset because if i want my #1 spark plug to fire at TDC, and my signal is 90 degrees out then my firing time will be wrong. Or am I missing something here. The standard engines that I usually work on have the TDC signal at TDC. I cant figure out why it is different with aftermarket ECU's. I know I could just follow the instructions and it will work but id like to know why. Thanks again

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 I thought the idea of the missing tooth was to signal TDC,

Yes it is a reference to TDC, but it doesn't need to occur at TDC. 

Or am I right in thinking that with a Link, the ecu just needs to see a signal gap (missing tooth). If the missing tooth is at 90 BTDC, does the ECU have a programmable offset because if i want my #1 spark plug to fire at TDC, and my signal is 90 degrees out then my firing time will be wrong.

You set your trigger offset in the software (calibrate trigger menu).  This is the angular distance the crank must rotate from the first tooth after the gap to TDC.  However you don't need to measure anything, just take a guess then crank it with a timing light on and adjust until the marks line up.  More info in the help file and it will make more sense when you actually do it.

The standard engines that I usually work on have the TDC signal at TDC. I cant figure out why it is different with aftermarket ECU's.

I think you will find the vast majority of OEM triggers that use missing tooth wheels, the gap is never at TDC.  Ford's favourite for instance is usually 90ATDC. There are many reasons, one I already mentioned is the crank acceleration near TDC, another is if your missing tooth is in an area where your ignition event must occur (say 0-45°BTDC) there is the possibility that it would be less accurately positioned since there is no tooth to reference.  

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So I've mocked up a cam trigger wheel with one tooth. The picture is of the signal I'm getting using the sensor. It's all mocked up on a lathe at the moment but wanted to clarify that my pattern is ok. I take it the ecu only sees the positive voltage. There is a small delay between the positive and negative spikes which shouldn't matter if the ecu only uses the positive spike. Correct me if I'm wrong please. I can make the tooth narrower which will make the delay between spikes shorter. You won't be able see from the picture but I'm getting 2v at idle which should be high enough

image.jpeg

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Although it will probably work fine just the way it is (for a cam/sync), since you did ask the question...

Your tooth is too wide.  For a VR sensor the ideal tooth width is about the same as the diameter of the "pole piece".  The pole piece is the magnet inside the sensor.  If it is not visible on your sensor you can find it by wiping something like a paper clip over the end and noticing where it sticks.

VR24_E_Model.png

My understanding is with VR sensors the "trigger" point is where the wave crosses zero so you want that to be as steep as possible.  Yours with the big flat spot at zero is not ideal.

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