quench effect on blower motor
 

I am trying to find the truth on the quench effect on blower engine and is still confuse me.

Someone say the perfect quench for n/a motor is at .040'' to crate turbulance (flame front) and also they are say this is the perfect # for blower engine also.

On the other hand someone say on a blower engine it is not so important to maintain a .040'' of quench and i notice that they have some engine run with as much as .100'' and more of quench on boost engine and someone say that is ok because the a/f mixture are in turbulance in the combustion chamber on boost condition that turbulance are need to help to burn all a/f mixture.

We need to consider that the detonation is an effect at ATDC and pre ignition a effect at BTDC and they are cause by detonation because detonation make hot spot in the combustion chamber.

So if i understand right a smal quench # are use to make turbulance and make a more efficient mixture burn to get to a no a/f mixture for the rest of the stroke (ATDC firing) Thats help for detonation occur.

Pre ignition occur BTDC and before spark firing due to hot spot in combustion chamber (due to detonation event) at inlet stroke,
In blower engine they have more hot inlet air and more cylinder pressure, as wee know all is there to promote pre ignition.

I am not an expert so if i am not right corect me, I just trying to understand the squich effect on boost engine vs n/a engine.

So which quench is promote to make the burn faster .040 or
.100'' ?

Don't know the answer to your question but I'm running .040 quench my blower engines.

Quench (a tight squish) is an excellent thing to have on any motor that has to run on marginal octane.

Quench doesn't necessarily MAKE extra power, but it "snuffs" detonation from the outer edges of the combustion chamber, and creates turbulence that makes it less likely for detonation to occur in the center of the chamber. This "stretches" your octane and lets you run closer to the detonation line.

A 8:1 N/A motor will run fine on pump gas, with full expected timing advance (36*) with no quench (squish clearance more than .070" is essentially "no quench").

Push that motor up to 10:1 (still no quench) and you are gonna start fighting to keep the dreaded knocks away. Same 10:1 motor with .038" quench will have no problems - even on up closer to 11:1 with the right cam.

Blower motor same thing. Many people lower their compression for blowers, and that's fine but you STILL want to match the deck heights and such to keep a tight squish with the piston and heads you've selected. Sometimes if there's not the right piston available, you may have to get a custom. BBC and SBC are pretty much available in every sort of combination you can think of, but if you are running a 360 Mopar, you can find it difficult to match a target CR with your preferred squish.

Squish/Quench is good for any motor - especially blowers.

How about this? If, on a NA motor, .040 is good quench; Then on forced induction, when you pack twice the A/F into the cylinder, why wouldn't .080 be the same?????

Can we can get the same effect of quench on a open chamber head style?

I am ok with you for a tight quench on n/a engine to make that turbulance need to help to avoid detonation, I have make some recherch on the net on that question on boost engine and they have 50% of peapole still run .040'' quench and the other 50% peapole say that is not so importan in boost engine
that in n/a engine and they run at more quench like .100''.

So i am still confuse on that for my built and even more with open chamber head style.

mcollinstn has it right

The actual clearance when running is much less than the static clearance. After the piston grows from heat, rocks in the bore a little, and the rod stretches a bit at RPM the piston is close to kissing the head at .040 - which is actually a good thing.

We used to run a reverse dome (dish) if needed to lower compression that mirrors the combustion chamber to leave the quench area intact as opposed to just increasing the deck clearance.

Here is a good article

http://www.chevyhiperformance.com/te...e/viewall.html

From the article: "According to Ken Duttweiler, the tightest quench he recommends is around 0.050-inch. He has built engines with far tighter clearances than this, but much of this depends on the piston-to-wall clearance. All pistons tend to rock slightly as they transition through TDC and this rocking motion reduces the piston-to-head clearance. Smaller-diameter pistons with tight piston-to-wall clearances don’t rock nearly as much in the cylinder bore compared to larger-bore pistons with wider piston-to-wall clearances."

My normally aspirated 489 has the piston .008 in the hole, and I was planning to run a set of Cometic head gaskets with .030 compressed height for a quench of .038. I was running a set of Fel Pro's that were .039 previously, but I thought the tighter quench would be beneficial. This article makes me wonder if I should go back to the .039 gaskets for a quench of .047. Pistons are Mahle flat tops with a 3 cm single valve relief.

Thoughts? Oh, sorry for the :hijack: :)

You know what opinions are like .. .040 is what most builders will shoot for .You want the quench area almost kissing........
Maybe Ken was talking about tightest quench for those that aren't real good with math, measurements and machine work

Kind of what I thought. When I measure deck height (how far down in the bore), do you take the measurement closer to the intake side of the bore, close to the exhaust side, or more in the middle? Logic says in the middle, to address piston rock, but want to be sure. I don't have a depth gauge, just a Mitutoyo dial caliper with a machinists rule on it that can check depth to some degree. Thought about zeroing a dial indicator on the deck and then swinging it over across the bore, but not sure if I could maintain accuracy.

From what I've read on drag racing web sites, you want to run a tight quench on n/a and supercharged motors up to about 15lbs of boost. Over that and on heavy nitrous motors, you want to open up the clearence to slow the combustion process. Quench causes turbulence which speeds up combustion and that is a good thing for detonation control up to a point. Beyond that point it increases detonation. Also, there is a zone of clearence from about .060 to .100 that is supposed to be avoided at all times as this will increase detonation.