Easy dual plug on a 3.2?

[Bob Gruen]

Is there an easy dual plug solution for the 3.2 Carrera engine besides the almost unattainable Andial system? I have read that you can run an MSD on a Carrera, would it be as simple as running two of them in parallel, along with an appropriate dual distributor and the required head mods?

Bob

[Trackrash]

Twin Plugging 3.2 Carrera question
Twin Plug 3.2 Motor?
3.2 to 3.4L twin plug conversion

[darrin]

sal carceller (scarceller on pelican) has reverse engineered the andial splitter and has helped put together a few twinplug setups that retain the carrera's factory motronic setup-- combined with his chip mapping, MAF and fuel injectors, you'd have what appears to be a good "plug and play" setup. You might want to contact Sal directly on this?

[juanbenae]

excuse my ignorance, but what would be the advantage to going 2x plug system with an otherwise stock compression and cam'd 3.2? does it have to do with modifying a chip to squeeze a bit more out of it on pump gas?

admittedly I did not read the RL build sheet in OP's sig, but I always assumed 2x was for higher compression application. please advise.

[prschmn]

That's a lot of money when said and done for not much on a stock engine for sure.

[911bruce]

[Tippy]

Originally Posted by prschmn

That's a lot of money when said and done for not much on a stock engine for sure.

If you're talking about Sal's setup, it's not just the hp increase. It's the overall driving experience enhanced with a smoother running engine that's feels peppier from better throttle response due to better atomizing injectors and ditching the barn door AFM.

[fred cook]

Well, "easy" is relative, but I used the Clewett Engineering XDi twin plug system when I built a 3.3SS engine. The system costs about $1400-$1500 but does away with the distributor entirely and eliminates having to buy expensive distributor caps and rotors. Also, the timing is infinitely adjustable via a 4 knob control box. The wiring can be a bit of a head scratcher and you will have to find a place for the two coil units. I have been quite satisfied with the one in my car. Hope this helps.

[Bob Gruen]

Originally Posted by juanbenae

excuse my ignorance, but what would be the advantage to going 2x plug system with an otherwise stock compression and cam'd 3.2? does it have to do with modifying a chip to squeeze a bit more out of it on pump gas?

admittedly I did not read the RL build sheet in OP's sig, but I always assumed 2x was for higher compression application. please advise.

Juan,

One design issue in the 911 combustion chamber is that the spark plug sits over to one side on a chamber that is basically a dome. This results in slow flame front propagation as the burn has to cross over 2/3rds of the piston's diameter to reach the far side for the burn to be complete. This makes the pressure in the cylinder rise more gradually, which is less than ideal. Think of it like a 'shove' verses a 'hit'. To compensate for this Porsche has to advance the timing sooner than what would be optimal, giving away power. The other posters are right in dual plug being required for high compression engines, you want a quick hit of force in the cylinder so that you can walk the edge of pre-detonation. Also, the domed nature of a high compression piston may be effected by a slower burn process.

There are some posts here and on the Rennlist forum that say dual plugging and remapping your ignition curve can gain around 12HP, and the engine runs better and cooler. I recently broke a head stud so I am looking at opening up the engine anyway, so if I am ever going to do it now would be the time. At this point I'm just trying to place an actual cost on it.

Bob

[Raceboy]

Easiest? Drill heads for 2nd plug, buy VEMS PnP with 2x 6cyl coilpacks and you are done. Works on stock sensors and allows for much better power, driveability and throttle response.
Works on stock sensors and you can remove AFM as a restriction.

[juanbenae]

Originally Posted by fred cook

The system costs about $1400-$1500 but does away with the distributor entirely and eliminates having to buy expensive distributor caps and rotors.

yep, caps and rotors are very price prohibitive....


bob, I am aware of the domed shape of the pistons tops and ignition characteristics they present. seems like a ton of effort and money for 12HP +/-.

[1979-930]

Toby, you know that the cost of HP increases exponentially up to that last 10 or 20 HP.

[fred cook]

With the reduced timing required by using twin plug ignition, you will have less chance of detonation on pump gas and, if you wished, could probably drop to a lower octane fuel to save some bucks! On my SC, the twin plug ignition makes for a much smoother idle and starts easier. I can let the car sit for a month, reach thru the open window, insert the key and it starts right up! I have not checked it but the twin ignition will probably help it run cleaner also. It's also nice to have the distributor out of the way!

[darrin]

Originally Posted by Bob Gruen

Juan,

One design issue in the 911 combustion chamber is that the spark plug sits over to one side on a chamber that is basically a dome. This results in slow flame front propagation as the burn has to cross over 2/3rds of the piston's diameter to reach the far side for the burn to be complete. This makes the pressure in the cylinder rise more gradually, which is less than ideal. Think of it like a 'shove' verses a 'hit'. To compensate for this Porsche has to advance the timing sooner than what would be optimal, giving away power. The other posters are right in dual plug being required for high compression engines, you want a quick hit of force in the cylinder so that you can walk the edge of pre-detonation. Also, the domed nature of a high compression piston may be effected by a slower burn process.

There are some posts here and on the Rennlist forum that say dual plugging and remapping your ignition curve can gain around 12HP, and the engine runs better and cooler. I recently broke a head stud so I am looking at opening up the engine anyway, so if I am ever going to do it now would be the time. At this point I'm just trying to place an actual cost on it.

Bob

Bob:

Seems to me that going dual plug would only really make sense if you also increased displacement by going with larger diameter pistons/cylinders. The underlying issue with the off-center sparkplug is further accentuated in these situations and (like the factory 3.6 liter solution), that much more "bang for your buck" would be realized through the combination of twinplugging and bumping displacement to 3.4 or 3.5 liter.