Megajolt installation Firenza 2000SL

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Megajolt installation Firenza 2000SL

Postby fistfullofV5's » Sun Aug 23, 2015 3:57 pm

Hi, this is a thread to chart my progress and setbacks (hopefully not too many) during the process to install a Megajolt programmable ignition ECU on my Firenza 2000SL.
For the uninitiated there is no finer guide to the Megajolt than that here http://www.autosportlabs.net/MJLJ_V4_ve ... tion_guide
There are of course other systems available but for information availability and popularity wise,the Megajolt takes some beating. The one I'll be fitting has seen previous service on my girlfriends classic Mini and seeing as that's currently off the road,I've pinched it for the Firenza loving partner that I am!
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This is the trigger wheel I'll be using. It's cut from 5mm steel and a pretty sturdy item with a diameter of 130mm. The diameter of the Firenza's crank pulley face is 120mm so it's just right. To help me mark out the trigger wheel for drilling mounting holes to fit it to the pulley I'll be using this
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It's the clear packing disc from a pack of CDR's and by happy coincidence it has a diameter of 120mm matching the crank pulley so it should help me to keep things accurate.
Regards, Dave.
Last edited by fistfullofV5's on Mon Sep 14, 2015 7:57 pm, edited 1 time in total.
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Re: Megajolt installation Firenza 2000SL

Postby Retro morgs » Sun Aug 23, 2015 8:52 pm

Sounds interesting,i'll be waiting for updates :D
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Re: Megajolt installation Firenza 2000SL

Postby fistfullofV5's » Sat Sep 12, 2015 11:04 pm

So after my holidays it's time to crack on. First thing to do was mark out the clear disc so I could use it to drill the mounting holes that will hold the trigger wheel to the crank pulley.
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VR is variable reluctance, the sensor that makes the magic happen,and the 9 teeth refers to the offset of the trigger wheel which I'll explain later. It's essential that the engine is set to TDC on the power stroke (both valves shut) of number 1 cylinder and any accuracy you can employ here will pay dividends later. If you don't have the engine cover fitted or have any factory timing marks,you'll need to establish exact TDC. If you watch a piston when you turn an engine you'll know that there's a certain amount of dwell at the top of it's stroke so it's not so easy to accurately gauge TDC by eye. There are a number of ways to do find true TDC,but I used the engine stop method and printed a degree wheel which I stuck onto the crank pulley with 0 degrees lined up on the notch in the pulley. I set up a temporary pointer,took out number 1 plug and turned the engine while feeling for compression with my finger so I knew the piston was getting close. Then I peered down the plug hole and made sure the piston had risen to TDC and turned the engine a little further so I had enough clearance to screw in my engine stop made from an old sparkplug and M8 bolt.
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Turn the engine backwards until the piston touches the stop. Mark on the degree wheel where your pointer is aiming. Turn the engine in the normal direction until the piston touches the stop again. Once more mark the degree wheel where the pointer is aiming. Then locate the midway point between the two marks you have made to find true TDC and move your pointer to line up with this.
Now we need to trial fit the trigger wheel to the pulley so we can fabricate a sensor mount. Now to get that pulley bolt out I used an impact gun. I got this electric one from Machine Mart for Christmas and it's likely the most useful tool I've ever had. If you can justify the cost (around £70) treat yourself and any nut or bolt will run up the white flag within seconds.
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Last edited by fistfullofV5's on Mon Sep 14, 2015 9:12 pm, edited 2 times in total.
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Re: Megajolt installation Firenza 2000SL

Postby fistfullofV5's » Sat Sep 12, 2015 11:31 pm

The sensor mount you make will need to be fairly beefy or at least have enough stiffness to resist the harmonic vibrations produced by the engine throughout the rev range. It's not unknown for vibrating sensor mounts to move the sensor enough to cut the signal to the EDIS module and produce a mystery misfire which could be a real headscratcher to troubleshoot. I made mine from 3mm stainless as that was what was in the scrap bin in work,and I like shiny things.
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Those who have access to a tig welder would be able to achieve a much neater finish than my slighty agricultural efforts but I know its strong.
It mounts to two of the engine front cover mounts on the block and keeps the sensor clear of the cooling fan.
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Now that the sensor is mounted, we need to determine the final positioning of the trigger wheel. EDIS/Megajolt requires that the missing tooth of the trigger wheel passes the VR sensor 90 degs before the engine reaches TDC. To set this,put the engine to TDC on cyl 1 if if isn't already there. Then move the trigger wheel so that the missing tooth is inline with the VR sensor
Last edited by fistfullofV5's on Mon Sep 14, 2015 8:51 pm, edited 1 time in total.
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Re: Megajolt installation Firenza 2000SL

Postby fistfullofV5's » Sun Sep 13, 2015 12:03 am

The teeth on the triggerwheel are spaced 10 degs apart so remembering the direction the engine turns normally,turn the triggerwheel clockwise whilst counting 9 teeth back from the missing tooth and mark tooth 9. This will offset the triggerwheel relative to engine TDC so the missing tooth will always pass the sensor 90degs before the engine reaches TDC.
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Try to get the VR sensor to tooth clearance as close to 1mm as you can to ensure a strong and stable signal for the EDIS/Megajolt
My pulley has two untapped holes which back in the day were used to fit a tool to turn the engine,but I'm going to tap these and bolt the triggerwheel to the pulley. I used my clear disc again to mark the position of the holes and drill mounting holes on the triggerwheel.
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Clearance issues with the cooling fan will mean that I will have to countersink the two mounting bolts and cut the centre out of the triggerwheel so that the pulley bolt is recessed once more,but that can't be done until I'm satisfied that the wheel is running with minimal runout,but that will have to wait till next week.
Last edited by fistfullofV5's on Mon Sep 14, 2015 8:57 pm, edited 1 time in total.
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Re: Megajolt installation Firenza 2000SL

Postby droopsnoot » Sun Sep 13, 2015 6:30 pm

I'd really like to follow this, but your photos are too big. It's taken five minutes so far and they haven't finished downloading yet - is there any chance you can resize them down to something reasonable before you post them?
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Re: Megajolt installation Firenza 2000SL

Postby fistfullofV5's » Mon Sep 14, 2015 7:21 am

Hi,I'm really sorry about that, and I'll try to sort it tonight. Have got the Imgur set at 800×600 and it looked fine on my preview pages. What would be the best size to upload?
Regards, Dave.
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Re: Megajolt installation Firenza 2000SL

Postby fistfullofV5's » Mon Sep 14, 2015 9:05 pm

Hi all and apologies once more for the issues with pic sizing. I've not used Imgur before and my auto resize to 800x600 caused some issues. To this end I've resized all the images to 640x480 and hope this will fix the problem. Any advice from more seasoned Imgur users will be gratefully received.
Regards,Dave.
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Re: Megajolt installation Firenza 2000SL

Postby droopsnoot » Tue Sep 15, 2015 10:25 am

That's much better, thanks. I haven't used imgur myself, I tend to use photobucket and resize to 800xwhatever before I upload (again, with the limited bandwidth, no point uploading massive photos and letting pb resize them).

Interesting about the positioning and alignment of the sensor, I was under the impression (from the small reading I did a while back) that you could program the ECU to deal with the sensor point being anywhere in relation to TDC to make these things much simpler. I might be confusing that with the Emerald ECU which I think is much more expensive.
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Re: Megajolt installation Firenza 2000SL

Postby fistfullofV5's » Tue Sep 15, 2015 5:24 pm

Hi,glad we got there in the end with the photo sizing, it's been a learning curve for me. Regarding sensor positioning,I think offset correction can be achieved on the Nodiz ecu and probably any that don't use EDIS to drive the coil pack. You can position the VR sensor freely but you have to abide by the EDIS rule which is the missing tooth must pass the VR 90degs before the engine reaches TDC . It's the mechanical offsetting of the trigger wheel relative to the pulley is the key to it.
Regards, Dave.
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