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VK Distributor Regraphing???

Maccar

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Gday new here, Ive just bought a VK EFI 202 of my brother in law. He said hes been having troubles with the pinging since the fuel changes. I have read a fair few threads on this site before posting this, so I relise changing to run on Optimax or Ultimate will make a difference. But he mentioned to me that I can get the Distributor Regraphed (dont even know if im spelling it right) to make it run better. Ive never heard of regraphing before (im not a tech head) but I dont know how good his mechanical abilitys are either. Is he talking out his ass, or does he have a point? My first instincts were to run on Unltimate for at least 1000kms before changing anything. Im sure this fuel topic has been through here a few thousand times but any help/advice would be appreciated.
 

synoptica

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A dizzy has a graph which, dependent on certain conditions, decides exactly how much advance (ie, how soon before the piston hits the top of it's stroke) the spark plug fires. In the VK it's simply based on RPM. Stock is 12 degrees for a VK EFI... but if the plug fired at the exact same point regardless of RPM, you'd get pretty crap performance. This is because no matter how fast the piston is moving combustion always occurs at the same rate... so for faster speeds, you need to fire the plug earlier to compensate for this (a bit of a simplistic view but you get the idea.)

A regraph for any VK (EFI only or ones with converted dizzies, carby VKs run EST which sucks balls and can't be regraphed) is a very good idea - old leaded was 97RON... chances are you're only running 95 or worse still 91 - as these fuels are of lower octane ratings you need to get them regraphed to ensure optimum performance and prevent pinging. I've got my carby with a VH dizzy which runs at 9 degrees, regraphed for PULP... runs perfectly.
 

vee ka

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or ya could just advance or retard the timing to suit the fuel!! thats all i do and have no problems what so ever. on ultimate i can advance it quite a bit but when running premium or even standard unleaded i just retard the timing and it runs fine. i set mine just below the pinging point, have it ping then back it off till it stops, i run mine quite advanced normally
 

Sammy

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if the motors stock you may not get much/any improvement out of re-graphing the dizzy, but its if been modified you usually will ... also i'd try and put a tank of 98ron fuel in it and see if it pings, my guess is it wont.

if so then simply retarding the dizzy till it stops pinging is the go.
 

85berlina

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When you guys say regraph the dizzy, do you mean just retarding the timing until it doesn't ping for a particular fuel?
 

vee ka

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nope, in this case retarding/advancing we mean turning the distributor itself by hand etc regraphing is different.
 
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85berlina

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So, then what is regraphing?
 

Maccar

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The reason I started this thread is because the timing is as far retarded as possible without starting problems, but it still pings. Ill change to Optimax or Ultimate and see if that shuts up the pinging.
 

vee ka

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i cant answer the regraphing question cause i kinda dont know?? thats why i had to leave that bit out :thumbsup: someone on here will more than likely know. if ya retarded as far as possible then yeah, looks like ya might need someone to have a look at it.
 

Sammy

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repgrahing the dizzy means changing the amount it advances the timing at certain revs.

how it works (simply) is that there are weights inside the dizzy connected to the shaft, as the dizzy spins the weights are forced outwards and there are springs on the weights to keep them in at lower rpm's but once the rpms get fast enough the weights will move out till the dizzy is at its maximum advance.

now regraphing the dizzy may just mean limiting how far the weights can move out, this will limit the total advance of the dizzy. changing the springs on the weights can also have different effects such as making the advance earier or later in the rpm range ....

from my small experience with this area it seems that stock motor advance alot slower than a worked motor, however they advance more degrees whereas a worked motor needs more initial advance (just up from idle) but then it needs to have the total advance limited.

you can do it at home yourself if your keen enough and have the springs etc ... but i've found its easier to pay $50 (thats what it cost me) to get it done properly on a dizzy regraphing machine .....

you also have vaccum advance which is seperate from all of the above, its more a cruise fuel economy thing ... it advances the timing more when you are cruising (and is regulated by engine vaccum) to get better fuel economy.
 
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