Raceservice4u Twin plug systems

 

Twin plug systems were used on many flat 6 Porsche race engines.
Examples are 917, RSR 2.8 and 3.0, 914/6,  935 etc.

Experts recommend installing  a twin-plug ignition system if the compression ratio is higher than 10:1.

911 engines need a high dome piston to get this high compression ratio.

The combustion chamber will then almost be split in 2.

It will take too long for the ignition flame front to spread  across the combustion chamber.

For a high performance engine you need a  twin plug system.

Most Historic race regulations will not allow you to use contact less, a modern ignition  system or a 964 dual distributor.

If you must use contact points raceservice4u has the reasonably priced solution.

 

 

This page explains how the distributor  is  made for a  Twin plug system.

Here your find pictures of twin plug cylinder heads.
Raceservice4u can do that for you   @150euro per cylinder head.

 

Here your find some pictures of other Twinplug distributors reproduction as  well very expensive original ones.

Raceservice4u  Twin  plug  systems  is  a Marelli replica   which is  based  on  a 911 distributor and reproduced rotor and cap.

The other alternative with Bosch cap and Rotor is extreme expensive. More than 2500,- euros for  the  cap  and rotor only.

The rotor is the biggest problem in this Marelli replica project.

Raceservice4u  found  a 150-degree rotor in the US, which is  used, for the project.

 

Samples from customers UK and Germany.

 

The construction has evaluated  now. The main  body  is now a one-piece aluminium. Which is a much solid but  also lighter construction. The outside is sandblasted and light polish for a vintage look.

 

 

 

Specifications

• Reproduction of the Marelli twin plug distributor based on a 911 distributor

• Extra bearing for the rotor. This is a must to have for a reliable distributor
• Jaguar V12    cap. Also available from Magneti Marelli.
• US-made rotor
• Adaptor made of HQ aluminium and TIG welded to the mainbody.
• Maximum advance angel can be changed rather easy. See below.
• The design  is tested on hard race conditions
• All units will be tested on an Allen syncrograph before delivery.
• Delivered with data sheet is availble on request.

 

Available Twin plug systems

1. Twin plug distributor turning clockwise for 911 2.0L  and 2.2L  with points and shaft 27mm

2. Twin plug distributor turning clockwise for 911 2.4  and 2.7L with points and shaft 30mm
3. Twin plug distributor turning anticlockwise for 911 3.0L. with points.
4. Twin plug distributor turning anticlockwise for 911 3.0L. contactless SC/Turbo system.

New now also available with Bosch cap.

The prices are from 1450,- Euros. See the RSR Shop.

 

Or do you want the original?  Which  is available now  for all 911 engines   prices are from 4900,- euro.

 

This one has 4 sets of contact points.

 

 

Caps and Rotors available

Here we show you 4 examples of Cap and rotor combinations. Which are available in the market.

A and B are the exact copies of the original Marelli twin plug distributor.

The original rotor and cap of Magneti Marelli is not produced any more and only available as very expensive NOS.

B is the best availble copy off the Marelli rotor and cap. The quality is  even better than the originals.

 

C and D caps are the Jaguar type. C is of the Magneti Marelli brand and quality. D is a plastic brandless cap.

The D cap is our experience better in wet conditions then cap C.

The rotor for C and D are the same and the just best available.

 

Both rotors need the extra bearing to hold it in the centre.

Not all suppliers have this option. For Raceservice4u is this standard.

There is a risk damaging the expensive rotor and cap.

 

For orders, quotations, information or questions please mail to raceservice4u@base.be

You get a respons within  2 workdays.

 

 

A new option for Twin Plug systems  or  high  PRM tuned  singel  plug  engines.

Price is 80 euro per set.

 

Example Report Twin plug distributor for Porsche 911 2,4L     Customer         Supplier www.raceservice4u.com Damsheide 59 (B) 3910 Neerpelt Tel 011-640665   Mobile +32 4 77 46 55 73 E-Mail raceservice4u@base.be               Twin plug distributor data sheet Turning clockwise for 911 2.4  or 2.7L with one set of points Reproduction of the Marelli twin plug distributor based on a 911 SC or  2,7 L distributor. Extra bearing for the rotor. Reproduced distribution cap US-made  rotor Adaptor made of HQ aluminium and TIG welded to the main body. Maximum advance angel 27 degrees plus static advance angle. The unit is tested on an Allen syncrograph before delivery.

 

 

Special Instructions for dual plug cars (two ignitions firing simultaneously).

To reduce maintenance and to synchronize ignition on dual plug, dual points ignition systems, both ignition systems can be triggered by the same set of points.  This is most commonly done on the early Ferrari Dino and Porsche twin plug engines. 

Diodes are required to eliminate feed back between the ignition boxes so that independent control of both upper and lower spark plugs can be retained by the two ignition switches on the dashboard. Refer to the drawing for installation of the diode.  Any one-amp diode will work.  Install the diode in series with each wire  to  connection  C.  And with the end of the diode marked with the band on the breaker points as shown in the after picture below.

This setup will work with Perma-tune boxes aswell with Bosch boxes with 3 connectors.

   

 

How to change advance curve

 

When you use a twin-plug system for your flat-6 and more than 10:1 compression ratio, experts say the maximum ignition advance must be 25 degrees or less.

Raceservice4u experience is that the 911 engines can handle more ignition advance for more power.

The other example is the Porsche 911 RS 2,7 with MFI. This stock engine has an  ignition advance of 36 degrees and maximum 38 degrees are  allowed, which is written in the factory data.

 

The  raceservice4u engine runs with 33 degrees at high RPMs.   We did a test to increase it to 36 degrees and the result was an increase of 4 Kw.   We need to do more tests to find the optimum.

 

Changing the advance curve of a centrifugal advance system is not difficult to explain but not easy to get the right settings.

 

 

You can change the springs or the weights(blue  arrows) to change the advance curve.

To change the maximum ignition advance is easier. Bend the stops (red arrows) to the center for reducing the max degrees.

 

You can do that also from the outside.

 

 

On the button of the distributor is an opening. With a screw-driver you can bend the stops or even the change the spring settings.

Test the result with a syncrograph or on the engine and a flashlight.

 

 

Copyright Jan van Elderen