shanerv

ok well we have all know that the y8 head works great on na setups. but tends to have a bad rep on boost projects. My bro inlaw is currently building a budget d series and I was wondering would the y8 head pose the same problems with that low of a cr? is it the heads combustion chamber that causes the detonation or the higher cr?

p.s he's looking to push in the range of 25-28 psi and around 350-400whp.

jew

from what i understand, it is both the higher compression and the shape of the combustion chamber that contribute to the liklihood of detonation in a y8. but when using vitaras, the nature of the burn changes due to the fact that the pistons sit so low in the deck and nullify the "quench" area in a stock y8. this is my understanding. i could be wrong and i'm sure there are other members here that can give you a better, more complete answer.

shanerv

thanks for the feeback. I kinda thought the same thing but wanted to get everybody elses opionion. keep em coming

b18.

See the flat on either side?

That's the quench pads on a Y8, effectively with the vitara's you're removing any kind of quench area that you had, until you get into the limits of rod stretch, but honestly they aren't going to stretch that far.

As far as I know the swirl created by an effective quench area (N/A) maintains a lower operating temp in that area, in a turbocharged application the mean intake temp is much higher so the edges of that area run the possibility of getting hot spots because they are a fairly fine edge, (less material to disperse the heat).

Here's a sweet Cosworth turbo head:


Notice there's no quench pad, it's designed for a much higher combustion temperature and effectively has all edges rounded out.

Now I'm not completely sure but I believe that's the main issue, quench pads are geared more toward N/A applications, where the wave form of the air is dictated by the piston shape, port geometry, and head design; as opposed to being forcefed air.

Not to say that port geometry, head design, and piston shape aren't important in a turbocharged application.

Foowee

y8 head and vitaras does not = detonation.

http://www.honda-tech.com/zerothread?id=2295855

b18.

No ----, it's not like they'll magically give you detonation. I believe that heads with quench pads are just more prone to hot spotting because they were designed for inherently lower operating temperatures.