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Need a few final bits of info 

 

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 Post subject: Need a few final bits of info
Posted: Mon Sep 20, 2010 8:32 pm 
Getting Side Ways
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1- Can somebody please give me a reference point to work off for re-installing the dizzy? For example:

"With the 30 BTDC mark lined up in the notch on the timing indicator, the dizzy rotor points at lead number 1"

2-The HO upper mani has 2 small vac line ports on the top.

I have connected one of these to the fuel reg, and one to the long flexible rubber vac line that goes all the way over to the passenger side. There is still a rigid plastic vac line that ends behind the manifold too. Which ones go where? Basically there are two small ports, and three small lines?

3-The coolant pick up points for the throttle body are the small metal line coming off the metal heater lines attached to the lower manifold, and the upright port on the right hand rear of the manifold, correct?

Any help would be greatly appreciated. Everything else is ready to go!
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 Post subject: Re: Need a few final bits of info
Posted: Mon Sep 20, 2010 9:31 pm 
Getting Side Ways
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tdc on compression stroke should be 0* on the balancer, install dizzy on #1 terminal.

Will require timing to be reset.
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 Post subject: Re: Need a few final bits of info
Posted: Mon Sep 20, 2010 10:29 pm 
Getting Side Ways
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Thankyou! Would you recommend setting the base timing a bit further advanced like 32 deg btdc? Or just leave it?

Any idea on the other questions? You seem knowledgable. In any case thanks for the reply.
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 Post subject: Re: Need a few final bits of info
Posted: Mon Sep 20, 2010 11:24 pm 
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If the compression is standard you could run 32* - 34* with 98 octane.
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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 7:24 am 
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The stock engine system is designed to run 91 RON petrol. Using a higher octane petrol than it needs to acheive optimum spark timing will actually decrease power output as the slower burn rate of higher octane fuels increase the anti-work component (ie. BTDC portion which pushes the piston backwards down the bore) of the combustion cycle due to the spark needing to be fired earlier to maintain peak cylinder pressure just after TDC.

Only when the optimum spark timing can't be acheived with a low octane fuel should a higher octane fuel be used. eg when compression ratio is increased and timing must be backed off to below the optimum spark timing point to avoid detonation.

So stick with 91 RON fuel. The timing can still be increased by 2-4° for a small increase in HP but remember this also pushes you closer to the detonation point.

 

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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 11:57 am 
Getting Side Ways
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That info makes sense, but why do I get noticeably better economy on 98? I haven't tried 91 for years, but remember it using a lot more fuel when running it. The car is back on a standard ECU these days, so I might knock back the timing and see how it goes.

Mike

 

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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 12:24 pm 
Getting Side Ways
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Again pinging doesnt need to be heard to be present, running 98 ensures it wont..
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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 1:08 pm 
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V8 Ghia Mike wrote:
That info makes sense, but why do I get noticeably better economy on 98? I haven't tried 91 for years, but remember it using a lot more fuel when running it. The car is back on a standard ECU these days, so I might knock back the timing and see how it goes.

Mike


Most 91 fuels have 10% ethanol. Ethanol burns quicker thus poorer fuel consumption.

 

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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 3:47 pm 
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Something to be aware of when you set your dizzy statically. If you set the rotor posi by eye it will actually be out by quite a bit. The reason is, the spark energy is very large on these cars and the spark will actually jump long before the rotor gets lined up with the post. So if you get it roughly close by eye then, turn the ignition on and turn the dizzy back then forward to the point where the coil fires you'll pretty close.
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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 10:14 pm 
Getting Side Ways
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Thanks, sounds like that will save some frustration and confusion lol. I really should have marked it all before removing it. Lessons learned....

xafalcon wrote:
The stock engine system is designed to run 91 RON petrol. Using a higher octane petrol than it needs to acheive optimum spark timing will actually decrease power output as the slower burn rate of higher octane fuels increase the anti-work component (ie. BTDC portion which pushes the piston backwards down the bore) of the combustion cycle due to the spark needing to be fired earlier to maintain peak cylinder pressure just after TDC.

Only when the optimum spark timing can't be acheived with a low octane fuel should a higher octane fuel be used. eg when compression ratio is increased and timing must be backed off to below the optimum spark timing point to avoid detonation.

So stick with 91 RON fuel. The timing can still be increased by 2-4° for a small increase in HP but remember this also pushes you closer to the detonation point.


I'll just set it to 30 and leave it, should have no problems that way. Thanks mate.
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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 11:04 pm 
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RAPTOR_XR8 wrote:
Again pinging doesnt need to be heard to be present, running 98 ensures it wont..


Yes, but a properly functioning stock HO won't ping on 91 either. In fact it even has a small built in "safety margin" which many people take advantage of by increaing static timing by a couple of degrees. An engine makes maximum power on the verge of detonation ie. just before it starts to happen, not when it's "only happening a little".

But at the end of the day just run whatever fuel you like. If you get an advantage from 98 you doing better than the Ford Motor Company.

 

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 Post subject: Re: Need a few final bits of info
Posted: Tue Sep 21, 2010 11:31 pm 
Getting Side Ways
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V8 Ghia Mike wrote:
That info makes sense, but why do I get noticeably better economy on 98? I haven't tried 91 for years, but remember it using a lot more fuel when running it. The car is back on a standard ECU these days, so I might knock back the timing and see how it goes.

Mike


Higher octane fuel contains pretty much the same amount of energy per litre as lower octane fuel. In fact lower octane fuel is marginally higher in energy because more ethanol and/or other oxygenated hydrocarbons are usually added to the higher grades to boost the octane (because ethanol etc is cheaper than highly branched hydrocarbons). Ethanol etc has both a lower AFR and lower energy content per litre than petrol. So burning a litre of low octane petrol produces slightly more heat than a litre of high octane petrol. It is this heat which drives our engine by expanding gases inside the combustion chamber and pushing the piston down.

Then add to this the slower burning characteristics of higher octane fuel which increases the "anti-work" component when spark lead time is increased to maintain peak cylinder pressure just after TDC. And so the situation gets even worse for running higher octane fuel than an engine needs.

The manufacturers can claw this disadvantage back (and more) by increasing static compression ratio so that more "work" is extracted from each combustion cycle. The higher compression also increases burn speed and so reduces the "anti-work" component as well.

But an engine that operates with optimum spark timing on 91 will not benefit from higher octane fuel unless something is wrong with the engine/ignition/fuel system etc. The manufacturers are desperately trying to improve milage to boost sales. If it was possible to do this in such a simple way, it would already have been done.

I would suggest that your engine may not have been running optimally for some reason.

 

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