Ignition Retard Under Boost
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- topcatcustom
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Ignition Retard Under Boost
Hi, is there a rule or guide line as to how much retard the ignition should have under boost, whether it be per lb or rev related?
Running about 6psi (on the gauge) and rev limit will not be any more than 6500 tops.
Running about 6psi (on the gauge) and rev limit will not be any more than 6500 tops.
TC
hi Tom,
a general rule is 1 degree at the distributor for 1 Lb boost, but as I posted on your other thread I would just dump out about 5 or 6 degrees of additional vac advance over what you would normally have off the vack advance and use a conservative mechanical curve that comes in late.
Best regards
Mike
a general rule is 1 degree at the distributor for 1 Lb boost, but as I posted on your other thread I would just dump out about 5 or 6 degrees of additional vac advance over what you would normally have off the vack advance and use a conservative mechanical curve that comes in late.
Best regards
Mike
poppet valves rule!
- topcatcustom
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Ta Mike, I'm going to try using the vacuum advance to retard for boost, I have 3 different vac cans, they are something like 6, 7 and 8 degrees so wasn't sure which to use as a starting point.
I do have an MSD BTM but didn't have any joy with it when I was trying to start the car for the first time so I disconnected it and haven't tried again, though I will hook it up again before I go messing around! If it is kaput I dont fancy spending £300+ on a new one as I am only running low boost and not professionally.
I do have an MSD BTM but didn't have any joy with it when I was trying to start the car for the first time so I disconnected it and haven't tried again, though I will hook it up again before I go messing around! If it is kaput I dont fancy spending £300+ on a new one as I am only running low boost and not professionally.
TC
- daxtojeiro
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Me chime in ?
If youve got an EFI setup then you will need to sort out the fueling by either having the Lucas chipped or by going with an aftermarket ECU, there is no other way and the Lucas simply will not fuel for the blower without it.
Of course if you have a carb then forget the above
Personally I feel youd be far better with wasted spark and a full mappable system, for the sake of 4 or £500 for it all I wouldnt mess about.
Up to you though,
Phil
If youve got an EFI setup then you will need to sort out the fueling by either having the Lucas chipped or by going with an aftermarket ECU, there is no other way and the Lucas simply will not fuel for the blower without it.
Of course if you have a carb then forget the above
Personally I feel youd be far better with wasted spark and a full mappable system, for the sake of 4 or £500 for it all I wouldnt mess about.
Up to you though,
Phil
http://www.extraefi.co.uk/cobra/accobra.htm SuperCharged 5325cc V8 Cobra Replica (Full sequential Fuel and Ignition MS3 management)
- topcatcustom
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Thats cool, as you say Im sure its up to the job.topcatproduction wrote:Thanks for the input Phil- but I'm staying old skool and happy with my carb and dissy for now! The combo has worked ok since the 60's on the scene so it'll do me on this one!
I'm thinking of going for a blower again now, all this talk about them has made me miss mine
Ohh, as for the question, the rule of thumb is cut 1 deg for every 2 psi of boost, certainly worked ok for me up to 8psi on my old 3.5, hotter plugs too if I recall,
Phil
http://www.extraefi.co.uk/cobra/accobra.htm SuperCharged 5325cc V8 Cobra Replica (Full sequential Fuel and Ignition MS3 management)
Jaycar do a programmable ignition unit that can be used with an existing dizzy and will alter the advance curve either way to your requirements . It has an optional MAP sensor and should do what you want to the vacuum advance too.topcatproduction wrote:Thanks for the input Phil- but I'm staying old skool and happy with my carb and dissy for now! The combo has worked ok since the 60's on the scene so it'll do me on this one!
The only snag is it uses its own hand held programmer rather than a laptop.
But is pretty cheap for the DIY kit - under 100 quid complete. It would be very easy to install it so it could be disabled and revert to the original ignition setup.
Dave
London SW
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London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
Thats what I run too.kiwicar wrote:hi Tom,
a general rule is 1 degree at the distributor for 1 Lb boost, regards
Mike
Have advance set at 38 total at 4000 rpm ( 14 initial & 24 advance).
BTM module is set at 1' retard / 1psi
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'73 Ford F250, 6.7ltr V8
Building a GT40 mk2
- topcatcustom
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