Opinions - B18CR Bottom End with Alaniz head

[fatboyz39]

The ideal is to design the piston dome and chamber roof to match each other for profile.
The welding of quench pads is done to reduce chamber size and add compression, it can also hinder flame propogation if it is not done with consideration of piston dome profile.
When i am designing a chamber shape i will tend to profile shape the piston moreso than the chamber roof (head). This is not because one is better than the other, just that removing the obstructions from the piston dome also reduces the piston mass, so it is win, win.
As for chamber modification, I would bias the design of the chamber to assist flow past the valve seat and across the chamber floor more than look for ways to bump the compression up with mods to the chamber.

Cheers Greg..

I know of a B18b that is being built now with CTR's an ITR crank and rods it has the same PR3 ITR 2000model head on it as our current B20Vtec engine with the CNC combustion chambers done and STD ports.It will be running in 4-5 weeks so we will have to wait and see what happens with it .

[tinkerbell]

I will be removing AC at minimum to reduce parasitic drag.

i thought the AC compressor has an electric clutch?

i.e. it is only parasitic when AC is on?

[82911]

I know of a B18b that is being built now with CTR's an ITR crank and rods it has the same PR3 ITR 2000model head on it as our current B20Vtec engine with the CNC combustion chambers done and STD ports.It will be running in 4-5 weeks so we will have to wait and see what happens with it .

Sorry, I don't understand your point?

[tinkerbell]

Sorry, I don't understand your point?

point is perhaps that the use of CTR pistons is about to be empirically tested...

[tinkerbell]

I will be removing AC at minimum to reduce parasitic drag.

however - you WILL improve lap times by reducing weight!!!

power isnt everything

[82911]

point is perhaps that the use of CTR pistons is about to be empirically tested...

Yes, I understand the intention, but the method is flawed. Tested against what? Is the engine builder going to back to back the CTR's against say a wiseco slug?
I think the biggest thing going against the CTR piston is it's weight. It's heavy. The fact that it's dome is large didn't seem to stop the Honda engineers from extracting amazing power from the B16B.
Just a thought.....

[tinkerbell]

Yes, I understand the intention, but the method is flawed. Tested against what? Is the engine builder going to back to back the CTR's against say a wiseco slug?

hmmm, yes, well, i guess it wont be so empirical then will it...

also - the B16B has a very high R/S ratio - 1.8 or higher? maybe the piston weight helped it spin?

or is all extra reciprocating weight bad?

[Benson]

Stock B20 > B18c with CTR piston

[fatboyz39]

Yes tinks there r/s ratio is 1.84

[Benson]

however - you WILL improve lap times by reducing weight!!!

power isnt everything

Power is everything!!!

[82911]

or is all extra reciprocating weight bad?

Mostly, yes. Unless you are chasing a smooth idle or building stationary type engines (gensets etc) But you can't race a genset!!!!

also - the B16B has a very high R/S ratio - 1.8 or higher

You are correct, a high rod stroke ratio does offset some of the problems with flame propogation through the chamber. To be specific. It allows the use of less timing and a later spark initiation because the piston dwells at TDC longer but accellerates away faster.

[tinkerbell]

i see a few 'built' B20V's with >12:1 CR's making high WHP numbers in the US...

does having larger diameter pistons also help flame propagation? or does the long stroke hinder this?

meaning they rely on displacement?