Printable Version of Topic

Posted by: Mueller Jul 30 2003, 10:48 AM

This is a Type I head, but it'll give you an idea for the 914 /4 motors.

Paul Guard, of Guard Transmission (maker of bitch'n parts for Porsche transmissions)
loaned me this head to get an idea on how to twin-plug my motor.

The secondary plug is a 10mm motocycle plug.

A modified distributor cap from a Nissan 4 cyl truck engine is adapted to fit on the stock /4 distributor...the rotor is from Nissan as well. I have the drawings for this modification somewhere in my garage

Using an aftermarket distributorless ignition would be ideal, but for cost savings, the above will work.

There is a company that'll machine these heads for about 300 dollars or so (they do this for aircraft...not for performance, but for redundancy (saftey))

The sockets in the head are to give you an idea of the angles.


Attached image(s)

Posted by: Mueller Jul 30 2003, 10:49 AM

another one:


Attached image(s)

Posted by: Mueller Jul 30 2003, 10:50 AM

********


Attached image(s)

Posted by: Mueller Jul 30 2003, 10:50 AM

*********


Attached image(s)

Posted by: L8Apex Jul 30 2003, 10:56 AM

Curious, what are the advantages of a twin plug engine?

Posted by: Brad Roberts Jul 30 2003, 10:57 AM

He just woke up.


B

Posted by: J P Stein Jul 30 2003, 11:03 AM

One can run higher compression without detonation....and spend more money.

Posted by: redshift Jul 30 2003, 11:17 AM

Also the redundancy, you don't want to be unredundant, or totally redunduntless.



M

Posted by: J P Stein Jul 30 2003, 11:33 AM

Not to be redundant, but....Mueller is talking airplanes which have 2 seperate ignition systems....magnetos, me thinks.
The down side of twin plugs & high compression is if one plug fails and the other keeps on firing, detonation will occur, you may not notice and keep on truckin'. At some point, you will notice the hole in your piston, tho.

Posted by: rdauenhauer Jul 30 2003, 11:45 AM

Given the propensity for the heads to crack at the spark plug hole in stock form why not weld up and re-tap for the 10mm plugs anyway?

Posted by: Brad Roberts Jul 30 2003, 12:12 PM

Oh.. that is a good one Rich.

B

Posted by: URY914 Jul 30 2003, 12:17 PM

Two things:

1. Is there really enough HP gain to justify the cost and PITA factor?

2. You're adding more weight (plugs, wire, cap, etc)

OK, maybe item 2 isn't that big of a deal to most of you.

Paul

Posted by: redshift Jul 30 2003, 12:25 PM

LMAO

It just hit me, you drive a kite.



M

Posted by: Brad Roberts Jul 30 2003, 12:31 PM

Words that I thought I would never see "together"

Drive a kite.

Sooner later Paul will make the car remote controlled so he can remove his weight.


B

Posted by: Aaron Cox Jul 30 2003, 12:56 PM

kiefer sotherland- flatliners right?...anyway, im back from a week long lurking experience........

Posted by: Mueller Jul 30 2003, 01:05 PM

From what I understand, the addition of the second plug was needed due to the increased cylinder pressure when RPM(?) installed the supercharger(s)* on the 914's.

*not sure how many had been installed, I have a copy of a magazine article with the /4 supercharged powered 914, it does not say if it was a one-off or if more had been built and sold.

On a bone stock motor I'm sure you'd see some gain from the second plug, but it is cost effective??? I doubt it.

Even in a run of mill aircraft powerplant, there is noticeble change in the running of the motor when one set of plugs is turned off while doing a magneto check.

Posted by: Targa Jul 30 2003, 01:09 PM

It looks as though you would have to remove your rocker assemblies, push rods & tubes to have enough room to change those 10mm plugs. Is this true?

Posted by: Mueller Jul 30 2003, 01:17 PM

Nope, that is one of the reasons for the 10mm plug instead of the 14mm(?) size of the factory plug.

The location of the new plugs have to be dead-nuts on however to ensure that dis. will not be needed.

Posted by: SirAndy Jul 30 2003, 01:19 PM

Worf in Enterprise TNG ...

Posted by: PatW Jul 30 2003, 01:24 PM

I'd like to see the set-up for that Ignition. The WOW factor for this is good. Thoughts also about timing, cams, run with D-Jet?, etc. Would make a powerfull motor. My.02

Pat

Posted by: Carrera916 Jul 30 2003, 01:46 PM

Hey Mueller,

Your idea isn't quite new as Porsche have done that with the 4 cammer engine (early Spyders & Carreras) and they were made to work right with other factors considered as piston dome shape, cylinder head combustion shape and flame proga...(can't spell the damn word, but the way the flame travels and ignite the fuel/air). The whole cylinder head & piston on these 4 cammers are more or less like the hemi design. I have grew up with these cars all my life and from one look at the picture of the type 1 head, I just felt it may not work well due to the design of the cylinder head combustion area. The timing of firing these two plugs on one cylinder on these 4 cammers beauty are a bit delayed (intentionally) and I could feel the difference when I shut down one or another. They ran two distributors with different timing setting (I think 15 deg. difference). If you want, I can look around for the close up picture of the 4 cam engine cylinder head to give you an idea....oh hell, i will look for it now and post it.

If you guys haven't see one of these beauty, you OUGHT to see it.... at least, HEAR her running....ohh man...goosebumps all over me now!!!

Try look into KAMMotors. com, they have sound effect stuff in their web! I haven't try it yet as I'm still hammering my frigging speakers to wake up ...sigh

However, Mueller, don't stop there....keep on trying and get in touch with me offline and I'd like to jump in to see what it can be done!

jerry

Posted by: Mueller Jul 30 2003, 03:21 PM

Hey Jerry,

Not my idea at all, I just like the concept

The second plug in the type IV motor is really a "band-aid" of sorts, but it's cheaper/easier than re-designing the heads and piston shape

My 3.6 is twin-plugged, but to be honest with you, I have no idea if both plugs are fired off at the same time or not

Posted by: Mike Pearson Jul 30 2003, 07:19 PM

Uh...Chief Dan George (playing the role of Old Lodge Skins) to Dustin Hoffman, in "Little Big Man", many years before Worf.

Posted by: TimT Jul 30 2003, 07:37 PM

yes they fire at the same time

to prove to yourself the merits of twin plugging, cut the belt to the second dist (j/k) or disconnect the second coil wire. Then see how your car performs.....

Posted by: KaptKaos Jul 30 2003, 08:20 PM

I think that VW&P did an article about 10-15 years ago (edit: maybe closer to 20, jeez, I am getting old) about a twin-plugged type 4 in a 914. As I recall, it was a 2.0 and the writer liked the performance. I still have the issue (somwhere??). I'll see if I can find and scan.

If my memory serves me correctly, the 914 was black, with flares and 5 bolt polished fuchs. I do not recall how they did the dizzy.

If anyone else has it, please post as it may take me a while to find it.

- Joe

Posted by: Aaron Cox Jul 30 2003, 11:05 PM

cant you run an 8 cylinder cap with a double sided rotor?

Posted by: redshift Jul 30 2003, 11:24 PM

Look at the car.. I think he may have anorexia carvosa, it looks like Karen Car penter, yeah.


M

Posted by: redshift Jul 30 2003, 11:27 PM

I think there is some way in all this to use D-jet and a choppy assed cam with twin plug.


M

Posted by: Mueller Jul 31 2003, 10:44 AM

Actually, the problem with D-jet + an aggressive cam has nothing to do with the ignition, it's the fuel injection itself (pressure sensor freaks out with massive/irregular overlap)

TimT,

I meant I was not sure if both plugs fire at the same exact time or if one plug fired a few degrees after the other one. I took my distributor apart to replace the timming belt and it looked like they supposed to fire at the same time, but the ECU might dictate other wise???

Posted by: philinjax Jul 31 2003, 11:46 AM

Mike M,

There were about a dozen sets of 2.L heads machined for the twin plug mod. by RPM German Autowerks of Port Orange, FL. Jay Richardson, RPM owner, sold the mod. kit for $850. The kit consisted of machining the customer's heads, supply of the twin points distributor, two coils, plugs, high temp. wires and instructions. He did mine turn key in his shop.

The distributor was a new unit from a 4 cyl. 81 through 85 Datsun pickup truck. RPM modified the advance curve and fitted an offset VW drive lug to mate with the 914 engine distributor drive.

The pics. are of one of the used modified distributors I picked up as a spare.

philinjax


Attached image(s)

Posted by: philinjax Jul 31 2003, 11:48 AM

Another pic.


philinjax


Attached image(s)

Posted by: L8Apex Jul 31 2003, 12:32 PM

wha? damn, long rough night sleeping. Someone has to set the alarm for me next time

Posted by: aufaber Jul 31 2003, 12:49 PM

Hey Rich, maybe I'm off here, but what would twin plugging have to do with detonation? Detonation is cused by lean or overly hot conditions in the cylinder the air fuel mixture to ignite at teh wrong time, right? Wouldn't an extra plug actualy make this worse since youy have another thin piece of metal to over heat and preignite the mixture?

As I understadn it the reason you twin plug is if you are going to run very high compression or boost pressures where your plug gaps must be very small to fire at all. Plus you gives you a more complete burn on in the right part of the downward run of the piston.

Posted by: J P Stein Jul 31 2003, 01:25 PM

Twin plugging (automotive)is a bandaid for lousy....or old fashion combustion chamber design. It is only "needed" when one raises the CR one of these old motors over a certain point. That point varies, of course, and the fuel available is also a consideration. Race gas is cheeper than twin plugging, but at some point, even that is not enuff.

As I understand it, it's all about controlling combustion.
Uncontrolled combustion is....not gud.

Posted by: TimT Jul 31 2003, 07:57 PM

The ECU fires both plugs at the same time (except if its a wankel engine) There may be some difference in the timing of the plugs firing with a dual cap distributor system, but the spark scatter will be really small.

Ive tuned some engines with TEC3 Motec and Haltech, none have the ability to "offset" time firing of plugs on a piston engine... I havent explored rotaries

My point was that to see the benefit of a dual plug system, run the engine on 6 (or 4) instead of 12 (or 8) plugs

you will notice the difference

Is the second plug worth the cost? that depends

Posted by: DNHunt Aug 10 2003, 11:26 AM

Mueller:

Here's a thought for a DIY twin plug ignition. Don't have any clue if it will work but consider this.

Ford EDIS 8 module provides 4 coil drivers with CDI
2 Ford EDIS coil packs provide 4 coils that drive 2 plugs each
Use a 35-1 tigger wheel with VR sensor in a locked down distributor which yields 2 ignition events per crank revolution that are synced to TDC #1 by the missing tooth.
Generate the digital control of timing with either MegaEDIS (up and running) or Megajolt Lite or UltraMegaSquirt (in the future)

Advantages:
EDIS components are available at Pick and Pull so that should be relatively cheap
Programmable advance, retard

Disadvantages
Experimental gonna take some testing and may have some expensive mistakes
Have to fab a trigger wheel sensor arrangement
Both plugs will fire at the same time
Not sure about tach output maybe off by a factor of 2

If you do it I might just copy you again

Dave