With regards to advance springs on my RV8 Lucas distrubutor. Where do people usually end up with regards to everything at maximum advance?
The Des Hammill book is saying a standard distributor is fully advanced at about 4500rpm and for best performance you need to set it somewhere between 2700-4000rpm. I have mine set at 3500rpm fully advanced at the moment but I haven't got a clue if that is the best setting without putting it on a rolling road which isn't so easy where I live.
Where do people usually end up with the rpm setting for full advance?
My engine is a 3.5 with Viper Hurricane cam, stage 2 head by Real Steel, 9.75 to 1 Vitesse pistons and Edelborck 500 type carb, so a medium state of tune.
Thanks
Kevin
Distributor Advance - 3.5 RV8
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MendipWursel
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I'm reading Des's book on ignition systems at the moment!
He reckons that the max advance should be in at the start of the plateau of the torque curve. This is a bit tricky to find on my engine as the curve is virtually flat from start to finish!
I used to run my 3.5 with the all in at round 2750 RPM. I ran 14 static (The static and the idle being the same with this setup). I ran 36 all in with no vac system fitted at all. (Eddy carb)
I now have a 4.6 with a programmable MSD system. My inital curve for this engine was 12 static/idle, 32 all in at 2700 RPM, this worked OK. This was the setup that that my bob weight dizzy ran so it was a good starting point for MSD setup.
I then started to mess about and it got worse!
As everyone goes on about 28 being the magic figure for this engine I thought that I run 12 static/idle, 28 in at 3300 RPM, it then holds at 28 until 4500 RPM at which point the torque is slightly dropping so I advanced the igintion up to 32. The result was not that great. (Using my bum on seat dyno)
I've just tried 18 idle (not static) because the book bangs on about how to find the best idle timing. This figure could be a bit tough on the starter motor so I only run 11 degrees at 0 RPM (static), this advances to 18 at 700 RPM. It is held at 18 until 1000 RPM. It then advances to 34 at 3000 RPM. My bum on seat dyno indicates good results, the engine must like the extra 6 degrees at low-ish RPM (up to 3000 RPM) over the very first setup.
I remember my old 3.5 liking the ignition being quite advanced when ticking over, the problem is that if you lock the dizzy down with this much advance the starter motor could be in trouble. Also the total advance would be too much but this could be sorted by using collars to restrict things.
The book does explain ways round the above issues but I bet its a right old fiddle with springs and stuff (That's where my MSD wins!).
Basically Des reckons that you could run the static timing quite low (the figure when the engine is not actually turning over at all). This is good for the starter motor. You fit weak springs so that as the engine fires the bob weights start to work at idle speed bringing the timing up to say 16-18 (what ever figure you found to give the highest idle speed and softest exhaust note). Also listen for an slight mis-fire in the exhaust, this indicates too much timing at idle according to the book! The system then advances the ignition to 36 at say 2750 RPM (or the start of your torque plateau). For this to work the total sweep of the mechanical system might have to be increased. (This is possible with some fiddling!)
....I read too much!
Cheers,
Pete
He reckons that the max advance should be in at the start of the plateau of the torque curve. This is a bit tricky to find on my engine as the curve is virtually flat from start to finish!
I used to run my 3.5 with the all in at round 2750 RPM. I ran 14 static (The static and the idle being the same with this setup). I ran 36 all in with no vac system fitted at all. (Eddy carb)
I now have a 4.6 with a programmable MSD system. My inital curve for this engine was 12 static/idle, 32 all in at 2700 RPM, this worked OK. This was the setup that that my bob weight dizzy ran so it was a good starting point for MSD setup.
I then started to mess about and it got worse!
As everyone goes on about 28 being the magic figure for this engine I thought that I run 12 static/idle, 28 in at 3300 RPM, it then holds at 28 until 4500 RPM at which point the torque is slightly dropping so I advanced the igintion up to 32. The result was not that great. (Using my bum on seat dyno)
I've just tried 18 idle (not static) because the book bangs on about how to find the best idle timing. This figure could be a bit tough on the starter motor so I only run 11 degrees at 0 RPM (static), this advances to 18 at 700 RPM. It is held at 18 until 1000 RPM. It then advances to 34 at 3000 RPM. My bum on seat dyno indicates good results, the engine must like the extra 6 degrees at low-ish RPM (up to 3000 RPM) over the very first setup.
I remember my old 3.5 liking the ignition being quite advanced when ticking over, the problem is that if you lock the dizzy down with this much advance the starter motor could be in trouble. Also the total advance would be too much but this could be sorted by using collars to restrict things.
The book does explain ways round the above issues but I bet its a right old fiddle with springs and stuff (That's where my MSD wins!).
Basically Des reckons that you could run the static timing quite low (the figure when the engine is not actually turning over at all). This is good for the starter motor. You fit weak springs so that as the engine fires the bob weights start to work at idle speed bringing the timing up to say 16-18 (what ever figure you found to give the highest idle speed and softest exhaust note). Also listen for an slight mis-fire in the exhaust, this indicates too much timing at idle according to the book! The system then advances the ignition to 36 at say 2750 RPM (or the start of your torque plateau). For this to work the total sweep of the mechanical system might have to be increased. (This is possible with some fiddling!)
....I read too much!
Cheers,
Pete
Last edited by sidecar on Sat Feb 19, 2011 12:53 pm, edited 2 times in total.
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MendipWursel
- Newbie
- Posts: 27
- Joined: Sat Jan 01, 2011 6:16 pm
- Location: North Somerset
- Contact:
Ignition Advance
I must say a brilliant response. My current max advance of 3500rpm looks to be too high based on what is being said. Max advance at the start of the torque curve is a very good starting point and as suggested I need to be careful of too much advance at tickover.
Brillaint and thanks
Kevin
Brillaint and thanks
Kevin
Kevin
Re: Ignition Advance
No problem, thanks for the kind words!MendipWursel wrote:I must say a brilliant response. My current max advance of 3500rpm looks to be too high based on what is being said. Max advance at the start of the torque curve is a very good starting point and as suggested I need to be careful of too much advance at tickover.
Brillaint and thanks
Kevin
The book is worth getting (the third edition one). It was 13 quid on ebay.
Its not as good as his book on Rover engines but its not bad.
Jaycar do a programmable ignition unit for less than the cost of a new dizzy. It will trigger from points or virtually any other sensor. You can then try any mod from the standard curve and reverse it immediately if that doesn't work.
http://www.jaycarelectronics.co.uk/prod ... BCATID=347
Costs about 60 quid including all the bits needed.
http://www.jaycarelectronics.co.uk/prod ... BCATID=347
Costs about 60 quid including all the bits needed.
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
Quagmire wrote:In the old days i would have said....
Megajolt!
But now its not available in kit form i dont think its cheaper than a dizzy.
Does a mega jolt fire coil packs then? If not you would still need a dizzy to distribute the HT.
Also I guess that you would need a crank trigger if the unit did work without a dizzy.
I guess that there are many ways to skin a cat. (Or electrocute one!
)There are. If you want a standard looking setup but programmable ignition, a locked dizzy using an internal trigger (DLM type works fine) and the Jaycar unit is the cheapest route. The snag is it needs its own hand held programmer rather than a PC to set it. But that could be an advantage in that you can leave it in the car.sidecar wrote:Quagmire wrote:In the old days i would have said....
Megajolt!
But now its not available in kit form i dont think its cheaper than a dizzy.
Does a mega jolt fire coil packs then? If not you would still need a dizzy to distribute the HT.
Also I guess that you would need a crank trigger if the unit did work without a dizzy.
I guess that there are many ways to skin a cat. (Or electrocute one!
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
Yep, Megajolt fires ford EDIS coil packs, which make truly massive sparks...
The system basically has two parts, the "stupid" bit (which is still very clever) which is made up of the EDIS module and coil packs, EDIS gets its info from a trigger wheel and VR sensor behind the front pulley. EDIS will just give 10 degrees advance if left to it own devices.
The higher level bit is the Megajolt itself, which communicates with the EDIS in the same way a Ford ECU would and gives the EDIS the command to advance or retard as it sees fit (based on how you have programmed it).
If the EDIS sees no commands to change value (for example if Megajolt died or was unplugged) then it will default to the limp home mode of 10deg.
When the kit was available it used to work out (just about) cheaper to install Megajolt than it did to buy a new Lucas dizzy
The system basically has two parts, the "stupid" bit (which is still very clever) which is made up of the EDIS module and coil packs, EDIS gets its info from a trigger wheel and VR sensor behind the front pulley. EDIS will just give 10 degrees advance if left to it own devices.
The higher level bit is the Megajolt itself, which communicates with the EDIS in the same way a Ford ECU would and gives the EDIS the command to advance or retard as it sees fit (based on how you have programmed it).
If the EDIS sees no commands to change value (for example if Megajolt died or was unplugged) then it will default to the limp home mode of 10deg.
When the kit was available it used to work out (just about) cheaper to install Megajolt than it did to buy a new Lucas dizzy
1974 Rover 3500s
1984 3.5 90
1959 2.25 series 2
1984 3.5 90
1959 2.25 series 2
All good stuff and it makes my MSD seem quite expensive!
Having said that I fitted my MSD for several reasons, just one of them being the ability to control the advance curve along with the total advance.
Other reasons include the six sparks per 'firing' below 300 RPM, the rev limiter, the fully programable NOS retard function, the launch control, (not set up yet), and the 45,000 volts across the plugs which should prevent the NOS blowing out the spark.
One final feature that Muscle Manta and I are looking at is the MAP feature which might actually allow the use of a vac advance system that can be setup to work properly with the 'squerks' of the Eddy 500 carb.
Having said that I fitted my MSD for several reasons, just one of them being the ability to control the advance curve along with the total advance.
Other reasons include the six sparks per 'firing' below 300 RPM, the rev limiter, the fully programable NOS retard function, the launch control, (not set up yet), and the 45,000 volts across the plugs which should prevent the NOS blowing out the spark.
One final feature that Muscle Manta and I are looking at is the MAP feature which might actually allow the use of a vac advance system that can be setup to work properly with the 'squerks' of the Eddy 500 carb.
