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Locked dizzy timing

Started by _Cbwardy_ , Feb 05 2014 11:42 PM

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18 replies to this topic

#1 _Cbwardy_

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Posted 05 February 2014 - 11:42 PM

Hey guys,
Just after opinions on ballpark timing figures for a locked distributor for straight lpg. The motor is an efi 202 with 11 to 1 static compression and a crow 35604 cam (226 @.050).

I've been having problems with pinging in second gear above about 2500-3000 rpm with both the blue motor electronic dizzy and the black efi dizzy. Locking the distributor seems like the only option at this stage...

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#2 N/A-PWR

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Posted 06 February 2014 - 12:59 AM

Pretty sure they are locked at 30. Dave I

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#3 76lxhatch

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Posted 06 February 2014 - 08:25 AM

You could probably build up the edges of the mechanical advance stops to reduce the amount of advance if you still wanted to keep some

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#4 rexy

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Posted 06 February 2014 - 01:16 PM

Speak to performance ignition services in nunawading.

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#5 _gmlj6_

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Posted 06 February 2014 - 02:47 PM

is the vac advance still on it?

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#6 _walpolla_

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Posted 06 February 2014 - 02:57 PM

post deleted. Wrong thread !

Edited by walpolla, 06 February 2014 - 03:00 PM.

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#7 _Cbwardy_

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Posted 06 February 2014 - 04:42 PM

Nah no vac advance. I don't have the funds to get it recurved. But the idea of building up the stops sounds good to me.

So if I locked it, 30 would be a good starting point?

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#8 _Bomber Watson_

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Posted 06 February 2014 - 07:21 PM

Depending on your cam with that comp ratio, i'd probably start at 25 and tweak my way up.

Cheers.

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#9 caterham2

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Posted 06 February 2014 - 08:14 PM

Speak to performance ignition services in nunawading.

Nah no vac advance. I don't have the funds to get it recurved. But the idea of building up the stops sounds good to me.

So if I locked it, 30 would be a good starting point?

Save your pennies and go to performance ignitions, like Rexy suggests. MUCH, MUCH cheaper than a detonated set of pistons .It is not that expensive to get it done anyway!!!!!

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#10 _Muzzy_

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Posted 06 February 2014 - 08:29 PM

The problem you have is not total advance as this doesn't occur until 3500 -4000
It's midrange, the easiest way to fix this is to change the mechanical advance springs to stronger ones
, you can check this with a timing light
Paint the outside of the harmonic balancer with a paint pen white, measure the dia and work out the circumference, then divide into 5 degree mark on the pulley with a black textra. Run the engine the engine not the advance curve , your total advance shouldn't be more than 35 at 4000 and should build at a steady rate. Not jump quickly, give this ago it will help to understand what's happening

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#11 _Cbwardy_

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Posted 06 February 2014 - 10:15 PM

thanks muzzy, sounds like a good plan. Although, the efi distributor appears to have less than half of the mechanical advance of the blue motor one. I set it at 12 degrees as per the vk Calais owners manual but still pings badly. I wouldnt've expected that it would with the standard timing, with a little more compression and on lpg even without the vac advance! Perhaps it's the cam that's causing me greif?

I'll be changing the cam shortly too though, and cant see the sense in spending money to pay somebody to mod the distributor if I'll have to get it changed in a couple of months again. At the moment, I would just like to get it running alright without detonation (even though I know it'll sacrifice power and efficiency to some extent). I've spent too long working on the car, now I m getting to the stage where I just want to drive it haha.

I've ordered a 1.5mm permaseal steel head gasket for it, which will lower the compression a tad too so i'll see if that changes anything. It's not running at the moment though, since apparently the shitty $20 head gaskets are made of cheese and blew between cylinders 5 and 6 - granted, the two times it pinged wouldn't have helped it.

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#12 Bernie

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Posted 06 February 2014 - 11:22 PM

You on LPG or ULP ? If its LPG then fatten it up a bit .If its unleaded then you need to be at least on premium ,you may need to fatten it up as well .Get a decent timing light and check what is happening at what rev range and work it from there .Have you checked your TDC reference on the balancer to piston Tdc ? You may have more advance than you think .

Bernie

Edited by Bernie, 06 February 2014 - 11:27 PM.

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#13 _gmlj6_

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Posted 07 February 2014 - 05:14 PM

LPG burns quicker than ULP so its not suprising you have detonation problems. fattening it up can fix it but its a bandaid solution. but if you are chaning things down the track and dont want to sort out the correct timing curve yet then adding fuel works. Like Bernie said make sure you know how much timing it really has in it.

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#14 Dr Terry

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Posted 08 February 2014 - 07:26 PM

LPG burns quicker than ULP

I'm not sure that is correct.

To my knowledge, the higher the octane number the slower & longer the burn is.

95 & 98 octane petrol burn slower & longer than standard (91) ULP. So they can make more power depending on mixture & tune.

LPG can have an octane rating as high as 115, depending on the butane/propane ratio, so it has a very slow burn by comparison to standard ULP.

Locking up a dissy is a bit drastic for a street car, can you image trying to start the engine hot at 30 degrees advance.

Good advice is to get the dissy recurved & the LPG set-up by a guy who knows his stuff, before you do some serious engine damage.

Dr Terry

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#15 _Cbwardy_

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Posted 09 February 2014 - 05:37 PM

Thanks for the suggestions. since you've mentioned it it's got me wondering if it is running too lean at higher revs? The system I have is a mixer ring type setup with just a screw type power valve in it. I think this might be causing a lot of my problems..

I've even doing some searching for different types or powervalves and came across a mixer that works exactly like a carby, and they liken it to an su in the ad. Does anybody have any experience with these? Looks pretty cool
http://m.ebay.com.au...e-/320994547616

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#16 _Bomber Watson_

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Posted 09 February 2014 - 06:09 PM

Hmmmm three of them would be cool....

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#17 71Ranger

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Posted 09 February 2014 - 07:29 PM

Hi cbwardy

Dr Terry is correct LPG is a higher octane fuel. You would be well served by an AFR to see if you are leaning off around 2500 rpm. Before doing anything drastic with the timing

Brian