twin plug or not

[manuyc]

Hello engine guru's guys.
i have an 81 targa that I'm having restored with about 80k documented miles. I have a thread on here of the build.
im going for the outlaw set up it has the RS bumpers turbo wing. plus a/c delete the previous owner used to track car on weekends so it has some engine mods already.
I would like to know is it worth twin plug the engine?
would twin plug hurt value of car or not?
thanks in advance

[Steam Driver]

I don’t consider myself an engine guru, but here’s my take on twin-plugging.

I don’t think for your engine the end justifies the means. The main reason Porsche twin-plugged the 964 was for emissions reasons, not power. This was because of the bore size of the engine. This also is one reason why aircraft piston engines are twin-plugged; without it combustion just doesn’t progress across the piston well-enough. The other reason is redundancy, of course. This isn’t a factor in the 911 of course. (One thing a lot of people don’t know is that the mags on an aircraft engines are not timed identically; I don’t know if the dual distributor does this or not but I doubt it.)

I have also had some experience with a BMW R100 engine that was twin-plugged. Looked cool, good bragging rights, but I didn’t notice any significant performance benefit.

So my bottom line it’s not worth the cost, additional complexity, and maintenance. But that’s just my opinion, and we all know about those!

[Trackrash]

I can't imagine twin plugging would hurt the value of your car, unless it is a pristine, low mileage, all original car. But value is often debated.

Why do you want to twin plug the motor? Is it to be used in conjunction with other mods that may dictate the use of twin plugs? Such as much higher compression and or larger bore.

Have you priced a twin plug setup?

[Steve@Rennsport]

Originally Posted by Steam Driver

I don’t consider myself an engine guru, but here’s my take on twin-plugging.

I don’t think for your engine the end justifies the means. The main reason Porsche twin-plugged the 964 was for emissions reasons, not power. This was because of the bore size of the engine. This also is one reason why aircraft piston engines are twin-plugged; without it combustion just doesn’t progress across the piston well-enough. The other reason is redundancy, of course. This isn’t a factor in the 911 of course. (One thing a lot of people don’t know is that the mags on an aircraft engines are not timed identically; I don’t know if the dual distributor does this or not but I doubt it.)

I have also had some experience with a BMW R100 engine that was twin-plugged. Looked cool, good bragging rights, but I didn’t notice any significant performance benefit.

So my bottom line it’s not worth the cost, additional complexity, and maintenance. But that’s just my opinion, and we all know about those!

Well,.....I'd respectfully take a different tack here.

1) Twin-ignition has zero downsides (besides cost) and plenty of benefits that make it very worthwhile if one has the resources. More HP, more torque, reduced cylinder head temps, easier starting, and of course, reduced octane sensitivity. The latter may allow more timing depending on CR (remembering that twin-plug engines need 1/3 less total for complete combustion).

2) Porsche twin-ignition systems all fire both plugs simultaneously.

3) Porsche used twin-ignition for more power with the fuel grades of the day, using higher CR going back to the 4-cam Carrera engines. Emissions wasn't a consideration. 3.6 litre engines NEED twin-ignition to safely run high CR's with pump gasolines.

[trond]

with the shape of CIS pistons no point in twin plug. Or are you considering other pistons

[Trakrat]

My observations...
1st... you post the HP of your cars in your signature. This tells me that you want to let people know how much power your car produces. So... in this respect, you're going to want to twin plug it, otherwise you will NEVER reach 300+hp.

2nd... twin plugging is expensive. You have to get the heads drilled for twin plugs, change out the P&C for a higher compression, buy a twin distributor, 2nd set of plug wires, a better engine management system, etc.... I chose NOT to twin plug my car, because I just can't afford to do it.

3rd... what would twin plug really gain? Let's be honest here... let's say you DO twin plug and have spent $10-15k+ in parts (not including labor) to give yourself a better engine. Now you need to upgrade brakes, and you'll need bigger wheels and tires, and then you'd probably want some more safety equipment, and on and on and on.


As for the value of the car, it REALLY depends on everything else. My thought was, if I wanted a twin plug engine, I'd buy a 964 or 993 and keep my car the way it is. Then again, if I wanted an extremely fast, high HP car.. I would have NEVER bought a 30+ year old car to begin with. LOL

[safe]

Originally Posted by Trakrat

2nd... twin plugging is expensive. You have to get the heads drilled for twin plugs, change out the P&C for a higher compression, buy a twin distributor, 2nd set of plug wires, a better engine management system, etc.... I chose NOT to twin plug my car, because I just can't afford to do it.

You will make more power with twin plugs all things equal, if its worth the cost I don't know.

If I was going to do twin spark I would skip a twin distributor and go with a COP stand alone system (maybe just ignition), wasted spark etc.

My next engine (not 911) will have a standalone system and LS1 coils, cheap and powerful.

[Iciclehead]

My Kremer was single plug with 9.8 compression on a 3.2SS, at the edge of what is safe. I ended up putting a J&S Safeguard on it, tuned it with huge care and the whole time I had wished I had it twin plugged, even if I would have run it single plug until I could have afforded the twin plug set up.

So, new engine is twin plugged out of the box, and the extra expense is actually negligible in this case as it already will get Motec with CoP, additional parts count is fairly low so well worth it. I won't be running it that near the edge and the driveability is a bonus, big relief though to not have to worry too much about gas quality....

Dennis