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Mon Jun 03, 2019 8:53 pm

I feel like there should be a stupid questions thread in this forum cause ive been asking a lot of stupid, curious questions recently.

Have/are twin plug T1 engines ever made? After going down the super 90 rabbit hole yesterday I found an article that talked about different power and efficiency mods to the earlier porsche engines and the concept of twin plugs just kind intrigued me so I was curious if it was ever dont on T1s. If it is, are the heads basically always one off, or does someone actually produce something that crazy?

Mon Jun 03, 2019 9:22 pm

Revmaster makes a twin plug T1 head. It is used primarly for VW powered aircraft engines. We do use twin plug T1 heads in some racing platforms as well but not many.

Mon Jun 03, 2019 9:59 pm

Yes, it's done. It's a little more popular in the T4 realm because the bores are so large. I'm doing a set for my Type 4 engine.

Mon Jun 03, 2019 11:30 pm

Roy at MOFOCO will machine for dual plugs on request. Probably more for aircraft? Drag? IDK.

Photo take from the MOFOCO website

Tue Jun 04, 2019 12:35 am

Yes.
IN GENERAL, the modification doesnt pay off until 94 bore. But at 94 bore there can be a significant advantage. There are a few things to be aware of, or the mod will not do much difference. Done correct there will soon be a 7-10 hp gain plus more torque, better emissions and a cooler running engine.
Some years back a German gearhead built a very detailed 103 x 71 turbo type 4 with twin spark heads. There was a whopping 30 hp difference between 1 and 2 plugs active per cylinder.

The 356 is different because of the chamber. The more CR (higher piston) the more advantage with twin plug. But even a bone stock 616 90 hp engine that gets converted to twin spark normally releases about 5 hp more, better driveability, MUCH better burn and better fuel efficiency. A 616 twin spark with raised pistons and 10-1 CR typically pulls about 105 hp and 155 Nm torque.

Tue Jun 04, 2019 3:08 am

Ahhh, crap.

Now you've made me want twin sparks..

Tue Jun 04, 2019 3:22 am

Alstrup wrote: Yes.
IN GENERAL, the modification doesnt pay off until 94 bore. But at 94 bore there can be a significant advantage. There are a few things to be aware of, or the mod will not do much difference. Done correct there will soon be a 7-10 hp gain plus more torque, better emissions and a cooler running engine.
Some years back a German gearhead built a very detailed 103 x 71 turbo type 4 with twin spark heads. There was a whopping 30 hp difference between 1 and 2 plugs active per cylinder.

The 356 is different because of the chamber. The more CR (higher piston) the more advantage with twin plug. But even a bone stock 616 90 hp engine that gets converted to twin spark normally releases about 5 hp more, better driveability, MUCH better burn and better fuel efficiency. A 616 twin spark with raised pistons and 10-1 CR typically pulls about 105 hp and 155 Nm torque.

Should the spark both be firing at the same time or should they be fired
individually at different degrees apart ?

Tue Jun 04, 2019 8:27 am

They fire at the same time. Best to use a crank trigger too.

Tue Jun 04, 2019 8:40 am

bugguy1967 wrote: They fire at the same time. Best to use a crank trigger too.

They don't always fire at the same time, there can be advantages to staggering the sparks.

Tue Jun 04, 2019 10:07 am

FreeBug wrote: bugguy1967 wrote: They fire at the same time. Best to use a crank trigger too.

They don't always fire at the same time, there can be advantages to staggering the sparks.

I agree with staggering

Tue Jun 04, 2019 10:24 am

I read an interesting article on dual plugs, staggered spark, and flame fronts. I can't remember where I saw it at though.

If I remember correctly, compression chamber shape made a difference if a staggered spark made a difference than sparking them at the same time.

I think mostly the VW aircraft use them for redundancy, not so much performance, but both could be gained.

Tue Jun 04, 2019 10:34 am

Gary Peloquin picked up about 20 free horsepower when we added twin plugs to his Scat split heads ..

Tue Jun 04, 2019 4:55 pm

it's a neat idea but I don't get excited about it.
There area lots of neat ideas that gain gain you a few %, many of them simpler.