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Raceservice4u Twin plug systems
Twin plug systems were used on many flat 6 Porsche
race engines. 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.
This page explains
how the distributor is made for a Twin plug system. Here your
find pictures of twin plug cylinder heads.
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. 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
Available Twin plug systems
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.
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.
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 Copyright(c) 2002 Jan van Elderen. All rights reserved. |