Crank Fire Advance???

[nomad]

Wondering if some folks knowledgeable on crank fire ignition systems can tell me if one can mimic what the vacuum advance is supposed to do with these. It seems to me that if they were to use an O2 sensor or something along that line that it would be possible.
I have NO knowledge along these line's and am hoping for a little education!


Kurt

26/3754

[CBUEB1771]

Kurt,
I am far from an expert but have been noodling about a crank trigger system for my +2. One common approach is to put a throttle position sensor (TPS) on the throttle shaft. The following is a link to Weber's TPS kit for the DCOE range:
http://www.burtonpower.com/parts-by-bra ... 2-660.html
This can be used with any number of engine management systems that support multiple input control of ignition timing.

[nomad]

Well, Russ, I suppose that would work though not mimicing vac advance exactly. I imagine all that would be needed to fit it would be a longer throttle shaft. What kind of prices have you come across for crank trigger unit's? I imagine I need to start googling!

Kurt

26/3754

[GrUmPyBoDgEr]

The Weber throttle position sensor fits without any alteration to the existing carbs.
That along with the crank sensor & a coolant temperature sensor add up to what is required for what is commonly called a 3D management system.

Cheers
John

[CBUEB1771]

Well, Russ, I suppose that would work though not mimicing vac advance exactly. I imagine all that would be needed to fit it would be a longer throttle shaft. What kind of prices have you come across for crank trigger unit's? I imagine I need to start googling!

Kurt

26/3754

Kurt, I agree with your point. However reasonable inferences about inlet manifold depression can be made with crankshaft speed and throttle position data. High crankshaft speed + small throttle opening = high depression, low crankshaft speed + large throttle opening = low depression. Doing this the right way will involve dynamometer time. Burton Power has many options for crank trigger ignition and QED has castellated crank pulleys and crankshaft position sensor brackets for the Twin Cam:

http://www.burtonpower.com

http://qedmotorsport.co.uk/qed-shop/lotus-twin-cam

Quite a few people on this forum have made this modification so I hope a few more chime in. I am not sure if a wasted spark system can be used safely with carburetors. I have seen a few installations with a cam position sensor that inhibits the wasted spark.

[nomad]

Guess I was thinking in one dimension! Forgot that the electronic brain could analyse something equivalent to what the vacuum advance does and do it better I'm sure.

Kurt

26/3754

[Chancer]

If you want to mimic it completely then use a MAP sensor but a TPS is the best unless you are looking for the last degree of refinement, emissions and fuel economy.

Trying to control vacuum advance using a lamda sensor is a no-no.

[CBUEB1771]

If you want to mimic it completely then use a MAP sensor

Absolutely, if you are also using fuel injection. If you retain carburetors then the AF ratio is still controlled by our old friend Bernoulli.

[GrUmPyBoDgEr]

Well, Russ, I suppose that would work though not mimicing vac advance exactly. I imagine all that would be needed to fit it would be a longer throttle shaft. What kind of prices have you come across for crank trigger unit's? I imagine I need to start googling!

Kurt

26/3754

Kurt, I agree with your point. However reasonable inferences about inlet manifold depression can be made with crankshaft speed and throttle position data. High crankshaft speed + small throttle opening = high depression, low crankshaft speed + large throttle opening = low depression. Doing this the right way will involve dynamometer time. Burton Power has many options for crank trigger ignition and QED has castellated crank pulleys and crankshaft position sensor brackets for the Twin Cam:

http://www.burtonpower.com

http://qedmotorsport.co.uk/qed-shop/lotus-twin-cam

Quite a few people on this forum have made this modification so I hope a few more chime in. I am not sure if a wasted spark system can be used safely with carburetors. I have seen a few installations with a cam position sensor that inhibits the wasted spark.

The Zetec engine in my S4 uses 45 DCOE's with a Weber Poti' on the end of them.
The 3D management system utilises the Ford Zetec wasted spark coil pack with no problems.
John

[CBUEB1771]

The Zetec engine in my S4 uses 45 DCOE's with a Weber Poti' on the end of them.
The 3D management system utilises the Ford Zetec wasted spark coil pack with no problems.
John

John,
As always, you are quite helpful for a GrUmPyBoDgEr. Thanks.
Russ

[GrUmPyBoDgEr]

The Zetec engine in my S4 uses 45 DCOE's with a Weber Poti' on the end of them.
The 3D management system utilises the Ford Zetec wasted spark coil pack with no problems.
John

John,
As always, you are quite helpful for a GrUmPyBoDgEr. Thanks.
Russ

John

[CBUEB1771]

The 3D management system utilises the Ford Zetec wasted spark coil pack with no problems.
John

John,
I am sure your have covered this amply, but could you please remind us which ECU you used and did you do the mapping yourself?

[GrUmPyBoDgEr]

It is over 10 years since I finished that project & back then "the Zetec man" was Paul Dunnell of Dunnell Engineering.
He with his band of merry helpers designed & built his own lovely little ECU & software.
Since then it has gone through many iterations & he can provide units to manage any number of cylinders etc.
Since then Paul has developed stuff for the Ford Duratec but his ECU's may be used for any engine you have in mind; just contact him & send him my love.
Paul has a great pedigree being the nephew of the man who founded "Holbay" engines back in the 60's
The ECU he sold to me was "plug & play" & has continued to do a good job.

A mutual love of things mechanical has made us pen pals of sorts but he's never let me have anything other than full retail price---------------- so no financial connection.

Cheers
John

[nomad]

Thanks for giving me a little education on this. My original question is answered. The reason's for my considering it would be to get the sparks out from under the carburetors and to try to improve fuel economy. At cruise the advantage of a long ignition advance acquired in the old days by a vacuum advance is something I would prefer to not do without.

Kurt

26/3754

[jono]

I've done this - see pictures attached.

It's not too difficult using the Megajolt system. I made up the bracketry and drive peg for the TPS and bracket for the crank trigger sensor as the cost of proprietary versions seemed very high.

I obtained my parts (notched wheel, TPS and crank sensor) from Trigger Wheels.com in the UK.

The main reasons for my wanting to go this route was the ability to remove the worrysome ignition source (dissy) immediately below the carbs. However I also look forward to easy starting and smooth running.

I have had it running on the supplied base map in the chassis using the rig shown on the photo and it fired immediately and settled into a very smooth idle with excellent and immediate response to light throttle inputs (engine is freshly built). Once the car is on the road I will have it mapped.

I can really think of a reason not to do this. It's all fully reversible so it's a bit of a no brainer IMO.

I have approached the installation on the basis that I could go to full EFI in future. I have put a FI fuel tank in with integral swirl pot and return pipe boss (beautifully made by Andy Wiltshire) and have run flow and return pipework through the chassis. The price of TB's and the ECU put me off going the full hog at this stage.

Go for it I say.

Jon