[Eman911]

Is there anyone out there in Alfaville that can quantify the HP difference twixt the two styles of 10:1 pistons for our beloved 2L? Actual dyno numbers are much preffered to educated guesses.

 

[nunki]

Pistons are far from the only determinate of horsepower or torque in the NORD engine.

When the same care and craftsmanship are used to build up two identically configured engines save for the piston sets, I've always been hard pressed to see a statistically significant difference in HP that can be attributed to the use of one manufacturer's piston over the other on dyno runs.

bob

 

[Andrew]

Not hard numbers, but Norman Racing prefers the Motronic for flatter dome shape, allows more advance. Motronic is 10, HC is 10.4 if I remember right. Higher, rounded dome 10.4 gets in the way of burning, you have to scale back advance. You sort of lose what you gain, if not more.

Andrew

 

[alfaparticle]

I recently measured a Motronic piston in an uncut head and the CR was only 9.7. I don't know what the true CR is for 10.4 Borgos. Andrew and I disagree on ignition timing and CR's. The 10.6 Venolia's in my Spider have higher domes than 10.4 Borgo's and it makes maximum power at 34 degrees BTDC. More advance does not give more power beyond that and it eats into your safety margin against detonation. For lower compression motors that number could be 36 or so.

My understanding is that 12:1 is the compression ratio above which there is little to gain due to the long burn time. I think that you will find that most of the successful Nord race motors are running about 12 to 1.

If you are building a hot road motor and you are in the market for pistons you could buy Motronics and shave the head to get it to 10.5 or so.

My Motronic pistons were made by the same company that made the 10.4. Borgo and Federal Mogul are the same these days.

 

[Eman911]

Here's the deal- I run an Alfetta in ChumpCar. (endurance racing for those that don't know). I currently run the domed "10:1" pistons. I will be due for new pistons and liners by the end of the season. All else remaining the same (11.5 mm cams, Sperry ported head, tweaked Spica) will there be a measureable difference between the two designs after dyno tuning? If so, how much? 1%? 5%? I have read all the circumstantial evidence "we have found the Motronics to make more power", and understand the theory, I'm hoping that someone has done the testing and is willing to share that little bit of data.

 

[Alfar7]

Misinformation

Not hard numbers, but Norman Racing prefers the Motronic for flatter dome shape, allows more advance. Motronic is 10, HC is 10.4 if I remember right. Higher, rounded dome 10.4 gets in the way of burning, you have to scale back advance. You sort of lose what you gain, if not more.

Andrew: That is perfectly incorrect! Exactly backward.