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Old 07-23-2008, 06:09 AM   #1
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Default FIDLE mod flyback diode

I am just putting the final touches to my MS standalone and whilst doing the FIDLE mod with the TIP120 I noticed that the megamanual states that there should be a diode across the Idle valve itself for flyback purposes.

Does anyone use the flyback diode described in the megamanual? I didn't see anything mentioned in Brains writeup and a quick search didn't reveal anything.

Thanks
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Old 07-23-2008, 07:30 AM   #2
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I use the diode on my setup (parallel install) on my 90 with a NB engine. My cars idle is fine and the time that my first diode broke, the car didn't want to idle at all. So in my experience the diode is a must do mod.
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Old 07-23-2008, 07:41 AM   #3
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Thanks for the quick reply.

Where did you put the diode? On the valve itself or in the MS? I'm integrating my MS into a stock case and wondered if I can put it in there.

The FIDLE mod is switching to ground right? so the diode goes from the 12v supply to the FIDLE wire from MS. Can someone who is a bit more savvy with electronics tell me if it would have to be the 12v supply to the valve or could I go from the 12v supply in the ECU case to the FIDLE wire?
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Old 07-23-2008, 09:14 AM   #4
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I found it! looks like it can be any 12v source.

Name:  pwm-tip120.jpg
Views: 27
Size:  22.0 KB
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Old 07-23-2008, 09:43 AM   #5
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i don't even know what fiddle is. Any help out there?
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Old 07-23-2008, 09:47 AM   #6
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I do it




+12v at S12 IIRC.
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Old 07-23-2008, 10:22 AM   #7
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Hustler, Fast IDLE controls the amount of air that bypasses the throttle plate so you get a nice steady idle (in theory)

Brain, Thanks for the pics, might be worth updating the HOW TO to include a little more on the FIDLE because atm its only got one pic lumped in with the EBC mod.
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Old 07-23-2008, 10:45 AM   #8
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yeah, there's a lot i could add, and fix for that matter
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Old 07-23-2008, 11:13 AM   #9
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Is there any reason NOT to do this? Mine doesn't have it. Should I add this while I'm reworking it from 1.6 to 1.8 spec?
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Old 07-23-2008, 11:18 AM   #10
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Brain, make me a Mod for a weekend and I would be only too happy to update it and add bits like stock ecu case integration

Solo, I cannot think of a reason not to do it but without it Aussie Driver experienced big problems with getting the car to idle properly. More info required - Is yours a MSPNP? did you build or buy it? is it standalone or parrallel?
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Old 07-23-2008, 11:23 AM   #11
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something like this?




full of win.
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Old 07-23-2008, 11:26 AM   #12
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I'll post some pics of mine when I get home. Almost identical to that but with a few extra bits.
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Old 07-23-2008, 11:51 AM   #13
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i has another in my possession that i could do that same with has integrated map sensor, serial port, and spare serial port for extra stuffs like wb and whatnot.
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Old 07-23-2008, 03:40 PM   #14
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Brain built it for someone else with a 1.6. I bought it in the spring but have done nothing with it yet. I'm putting it on a 95 w/ SC for now.

I acquired some injectors and sent them out to Injector rehab this week. Anticipating they'll be back soon, I've been digging into the Mega Manual for a more thorough understanding before I change anything to prep it for parallel install on a 1.8. I want to have a to do list and some knowledge before I fire up the soldering iron!

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Originally Posted by Duckie_uk View Post
Brain, make me a Mod for a weekend and I would be only too happy to update it and add bits like stock ecu case integration

Solo, I cannot think of a reason not to do it but without it Aussie Driver experienced big problems with getting the car to idle properly. More info required - Is yours a MSPNP? did you build or buy it? is it standalone or parrallel?
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Old 07-23-2008, 06:29 PM   #15
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Does the MS have a TIP120 in it? If not then the original cars ecu handled the idle/warmup. If it does then either Brain was a lazy *** and forgot or the original car had the diode fitted to the valve itself in the engine bay.

I would avoid doing a parallel install on a 95, theres no need to, the only reason was to keep AC but now Joe has engineered us a workaround. A standalone will simplify wiring no end.
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Old 07-23-2008, 06:58 PM   #16
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what?! im so lost.

the tip120 is added to control idle. i dont have one, my stock ecu handles it. you can see the diode was added to the tip120 in the picture I posted above...


while the a/c works with Joe's circuit, when the stock ecu controls it alone with idle, there's no idle quality loss. BUt I agree not only is standalone easier...it's simpler and saves a ton of time building. If/When I build MSs again, I'll probably only offer a PNP a/c enabled standalone version, no more parallel.
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Old 07-23-2008, 07:12 PM   #17
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Sorry Brain my last post was aimed at solo trying to figure out why he didn't have one.
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Old 07-23-2008, 07:41 PM   #18
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oh i cant read. i started doing it after I built a few. man i still have to point out what solo needs to do to make his work for his 94, which isn't much.
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Old 07-23-2008, 07:47 PM   #19
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Easy as 1,2,3
1.FIDLE mod 2.fans mod 3.wire db37 harness for standalone

optional second fan mod to control purge valve for AC antistall
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