High Compression VS Low Compression Opinions

[No disintegrations]

I'm interested to learn what timing high compression builds get away with.

Pretty low, in the teens.

 

[750H.P.V6]

it's always a balancing act between static compression, boost, timing and octane. There are other factors too but those are the heavy hitters.

Neal

 

[Mr.Spool]

I'm interested to learn what timing high compression builds get away with.

A lot more than you think with the right fuel and tune.

 

[Mr.Spool]

Pretty low, in the teens.

Lots of factors but we run high comp motors a lot more aggressive with the right build and fuel

 

[Wahoo]

Pretty low, in the teens.

So I've been hearing of timing closer to 20 with 30psi of boost and high compression.

If timing is too low you can melt down your turbo, the exhaust gets much hotter.

 

[Wahoo]

I feel like I should go with 10:1 instead of 9.5:1

 

[No disintegrations]

I feel like I should go with 10:1 instead of 9.5:1

bottom line is the dyno is great for finding a good number for timing. go with what makes the most torque then back off a pinch.

 

[dank GN]

I just got my final numbers in and I'm going to be at 10.5 to 1. I'm running e85 for fuel . This picture is of my rod mocked up in its home . my first attempt I had the piston in the hole .125 @TDC which wouldn't have worked lol now with a new set from earl I'm at .003 in the hole

 

[Ttype6]

I just got my final numbers in and I'm going to be at 10.5 to 1. I'm running e85 for fuel . This picture is of my rod mocked up in its home . my first attempt I had the piston in the hole .125 @TDC which wouldn't have worked lol now with a new set from earl I'm at .003 in the hole

The pin bosses,of those pistons,have a lot of girth. Since the rods don't reside in the center of the pistons,you'll want to make sure the rods don't hit one of the pin bosses. I'm using these Racetech pistons and had to remove material from one of the bosses on each piston because the rods were hitting or too close.

 

[earlbrown]

Dank has an on center block. It was still awfully close with the meaty pin bosses coupled with a huge little on on the rod.

 

[dank GN]

The pin bosses,of those pistons,have a lot of girth. Since the rods don't reside in the center of the pistons,you'll want to make sure the rods don't hit one of the pin bosses. I'm using these Racetech pistons and had to remove material from one of the bosses on each piston because the rods were hitting or too close.

I had to remove alil from both sides of my rod to get the .040 clearance all the way around . They are beef cake right there though

 

[TTipe]

I had to remove alil from both sides of my rod to get the .040 clearance all the way around . They are beef cake right there though

Improved mass flow at lower pressures substitutes for a lot of boost and timing constraints.

 

[BEATAV8]

I have an old 109 motor here which I'm going to update. This engine was originally built circa 2004, back when pump gas and low compression was more or less the norm. It has an early chinese forged 3.400 crank, some genuine K1 rods, and some old deep dish JE pistons. FTS 215/220 cam.

I'm gonna update it with some new slugs. Compression Ratio: How high would you dare to go if you knew you wanted to go high?? E85 is the fuel.

 

[750H.P.V6]

11 to 1 works in my combo with E85.

Neal

 

[earlbrown]

With E85 (and that big cam) I would go as high as possible. Which basically means, measure all your stuff and put the piston crown .040" off the head. The static rate will be whatever it ends up at.

 

[BEATAV8]

I’m considering 11.5:1 to 12:1
Probably staying with the same cam shaft

 

[jasjamz]

11.5:1 sounds interesting... iron heads or aluminum?

 

[BEATAV8]

11.5:1 sounds interesting... iron heads or aluminum?

Could use either. Have a new pair of GN1’s I could put together or use a set of irons

 

[BEATAV8]

Also have a 3.625 crank available too. The assembly needs to be re-balanced anyways.

 

[earlbrown]

To get compression that high, you'll have to use the stroker crank. (or heads with a really small combustion chamber)