V8 split ditributor

[camnefdt]

Hi guys

So i live in South Africa, and im interested in building a V8, distant future project ^^.

Now to do this i am busy designing and researching all the different bits and pieces, and one of the parts im on now is the distributor and ignition system. From what iv been looking around and searching on this sight, the biggest problem that many have is that they cant get the distributer and coils to keep up with the spark at higher revs.

Since im planing to stick the motor i make in a R/C car i need it to run in the higher rpm smoothly and effectively.

The idea i have is instead of using one coil and distributor with 8 separate contacts to power each spark plug, would it be possible to split it between 2 distributors and have 2 separate coils. in turn having an ignition system for each side of the engine, essentially driving 4 spark plugs per ignition. i understand that each ignition would have to be timed in completely separate to the other.

Another question i have is, how much does these ignitions draw? would i be able to power them off 3 cell 2200mah lipo batteries?

Sorry if i dont come across very clear or precise, but im still new to all this and trying to learn how it all works ^^

Any questions are welcomed and any advice and criticism is encouraged.

Thanks all
Cameron

 

[123RWO]

2 - 4 cy distributors will certainly work. but each would fire plugs on both sides of the engine. You want each distributor to fire alternate plugs in the firing order to give even time between sparks and to allow each circuit to max. time to recover. For example, a common firing order is 18436572. Therefore one distributor would fire cylinders 1467 and the other 8352.

The old standard GM electronic ignition ( before they went to coil per plug) was good to about 8000 RPM on a V8 and it was inductive storage. You would think a capacitor discharge system could go faster yet, but I don't have any data.

RWO

 

[camnefdt]

thanks for the reply. and i realize that it wont be split for each side, makes sense, cause using four contacts evenly spread at 0, 90, 180, 270 (degrees obviously), in each distributer, then timing them offset so that it will fire in between the other distributors cycle. if you can make sense of my thought process ^^

does anybody have some plans or tips on building my own ignition system. . .

 

[123RWO]

Building model ignition systems from scratch is usually not practical. Better to spend your money on commercial units of known quality and performance. One good source is http://www.cncengines.com/ I'm sure there are others.

RWO

 

[camnefdt]

im just weighing up the options and if i can do it myself, will just add to the satisfaction of the project once completed.

 

[gerritv]

The older V8 Ferrari's (1974-1980) often had 2 distributors each with its own coil, one for each bank.

Using a photo interrupter and a simple disc with 4 holes would do the job, then use electronic advance. The bigger problem is making the cap.

Ferrari V8's also use a flat crank (easier to make) and contribute to the distinctive exhaust note due to firing patterns.

Gerrit

 

[jpeter]

I run my 44 cc v8 using a single distributor, 1 inch in dia. I use electronic ignition and can rev it up to maybe 6000 rpm with out too much trouble. Haven't tried much higher. Keep in mind its not under load. I also use 3s, 2200 lipo batteries for power. My batteries are not the best cuz they're tired 450 helicopter batteries, generally turnigys. Never-the-less I think I could run the motor for 15 minutes or so before recharge. I usually run it in short bursts so its kinda hard to tell. I just keep checking the voltage. to see it do a youtube search for "worlds smallest v8."

 

[camnefdt]

Thanks for the reply peter, would it be possible to see your ignition setup? and a list of the parts you used.

I don't really understand the electronic ignitions and not 100% sure of how they work or what components they comprise of.

Cameron

 

[trumpy81]

Cameron, Bob Shores wrote a book titled 'Ignition Coils and Magnetos In Minature' for model use, it would be a good source to help you understand ignition systems and also give you some valuable designs to work with.

The book is available from a number of sources at a reasonable price of around $30.00 US. You'll find it on Amazon or sometimes eBay but you can also get it from Plough Book Sales in Australia or a number of other sources in the US.

http://www.model-engine-plans.com/books/index.htm
http://www.ploughbooksales.com.au/007938.htm

Check out this site also:
http://www.minimagneto.co.uk/

Also, see this thread http://www.homemodelenginemachinist.com/f25/ignition-no-condenser-no-points-17441/

My copy of the book should arrive soon I hope

I also plan to build a V8 of my own design, but I have plans for Steve Hucks Demon V8 (Can't decide what engine to build first ... ). Steve used an ignition system from http://www.cncengines.com/ and it works quite well with a single distributor.

For my own engine though, I plan to put it in an RC Boat so I have the same sort of requirements as you. If I come up with a good design for the ignition system I'll let you know. You will probably need a system that offers automatic timing advance, which is what I'm looking for, if you want easy starting, reliable slow idle and good high speed performance. I think the ignition that Steve used has that feature but I'm not 100% sure. Of course, you could always use a mechanical advance unit if needed.

Search the forum for the thread titled 'Small V8' That's Steve's build thread. Unfortunately, the links to the photos are broken but if you need them, I have all of them

HTH

 

[gbritnell]

Attached is a link to my V-8 engine running. I have 2 different ignitions that I use, one is of the Jerry Howell design and the other is the S&S design. Both work fine. The distributor has a single magnet trigger with a timing disc to interrupt the magnetic field. The cap is a Bruce Satra cap now being sold by S&S. The link is in the previous post (c&c engines). My ignition has no advance and the engine will idle from 900 rpm (light flywheel action) to 7800 rpm. (honest rpm, not free revving). In the video you can see the 3 wires coming from the side of the distributor where the Hall effect transistor is located. I have never had any trouble with the high energy spark burning out my Hall transistor but one thing that will kill it in a heartbeat is to have the ground wire come loose. I do have a 4 cylinder engine with a mechanical advance and I must say it helps on that particular engine. Why the V-8 doesn't need it I can't say.
gbritnell
[ame]http://youtu.be/fRVYYtdhG_8[/ame]

 

[trumpy81]

GB, I love your 302 Ford Engine, I wish you had plans available for it Being a Ford nut, it would look great on my mantlepiece

I'm wondering if the Ford has a low compression ratio 5 or 6 to 1 or less? That may help explain why it doesn't need timing advance, although I think the S&S ignition does have auto advance?

Also, the Jerry Howell Ignition, are you referring to the T.I.M Ignition or something else?

 

[gbritnell]

Hi Andy,
The compression ration is 8:1. The S&S ignition is just the basic single spark ignition. The Jerry Howell ignition is in fact the TIM ignition. It seems like it will rev a little higher with the Howell ignition but as far as numbers I've never checked them.
I played around with all different types of carburetors over the years and finally settled on the simple RC air bleed type carb. I then took the dimension from that carb and copied them into an Autolite (Ford) style 2 barrel carb. Normally I run it with the RC carb and leave the other carb out for display so that people can see it but it runs almost identical to the RC carb.
The engine has a full pressure oil system and has complete cooling through the block, heads and intake manifold. When I built it I wanted a 'scale' working model engine.
gbritnell

 

[trumpy81]

GB, that sure is a sweet looking carb. I have pulled a few of those apart in my day but I doubt very much that I'd remember where all the bits go now ... lol

I have thought about getting hold of an old Cleveland (Australian Version) or Windsor 302/351 and preparing drawings, but I have so many projects on the books and illness keeps me out of the workshop a lot of the time, but I will get it done one of these days.

I wish I had drawn up plans for the 289 that I had in my '67 XR Falcon GT. I had that stripped back to the bare unpainted block. But in those days my pursuits were a little different

I also used to own a '78 Ford Fairmont GXL with a 351 Cleveland but it was fitted with a 4-barrel Carter carburettor. I didn't like the Carter, it went out of tune just by looking at it ... lol

I crashed and then sold it before I got around to putting a Holley on it ... lol

Most of the 302's here have now had the customary Holley 2 or 4-barrel fitted and it is quite hard to find an original Autolite 2-barrel. I'm sure there would be one floating around somewhere though.

I've had lots of other Fords also, but they were mostly 6-cylinders including my current '05 Falcon XR6.

As for the ignition, I can't think of anything else that might allow the 302 to run as nicely as it does without advance. You probably have the cam timing tweaked to just the right spot scratch.gif Who knows, it runs sweet so I wouldn't worry about it too much

If you happen to stumble across the reason for it one day, I'd sure like to know ... lol