Tell me about "quench" - Team Camaro Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools Display Modes
post #1 of 14 (permalink) Old Jan 9th, 10, 04:03 PM Thread Starter
Gold Lifetime Member
Tom
 
Join Date: Mar 2008
Location: the 02176
Posts: 5,985
Tell me about "quench"

I've heard the term "quench" mentioned here with respect to engine building. I have a vague idea that it involves how to burn the combustion charge evenly but would like a more technical explanation.

What is it?

When do you need to consider it?

How is it calculated? Are there units of measure?

Is there a quench target in engine building?

Examples?


Thanks!

'67 rs - ordered new by my Grandfather
327 L30, K-K, Deluxe int, tach & gauges, 12 bolt posi, 4 speed.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
-
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Melrose RS is offline  
Sponsored Links
Advertisement
 
post #2 of 14 (permalink) Old Jan 9th, 10, 04:09 PM
Gold Lifetime Member
Steve
 
Steve69SS396's Avatar
 
Join Date: Nov 2005
Location: Modesto, CA
Posts: 2,372
Garage
Re: Tell me about "quench"

Read this: http://www.chevyhiperformance.com/te...ide/index.html

Quench is only one aspect of an engine build. Don't get overly concerned about it.

'69 Camaro - 429 SBC Dart Iron Eagle 9.325" block, Crower crank, Crower 6" billet rods, Ross pistons (10:1), Total Seal rings, AFR 245 heads, T&D steel body shaft rockers, Cloyes Timing set, custom ground 4-7 swap solid roller 274/286 @ .050" with .704" lift, Dart single plane, Holley Dominator EFI on E85, Injector Dynamics ID2000 Injectors, Stef's #1705R oil pan, F2 Procharger, Lemons 2" primary 4" collector, ATI 9" blower converter
Steve69SS396 is offline  
post #3 of 14 (permalink) Old Jan 9th, 10, 05:26 PM
Gold Lifetime Member
Harry
 
dawg's Avatar
 
Join Date: Mar 2004
Location: Colebrook CT.
Posts: 4,025
Re: Tell me about "quench"

Quench, or squish area is typically the flat area on the top of the piston that's almost level with the top of the block deck. It must have a corresponding flat area on the deck surface of the head to qualify as quench.
If you look at a combustion chamber, you will usually see these flat areas, and they will have the volume of the actual combustion chamber between them. When the piston is compressing the mixture, as the piston nears the head, the flat areas on the head and piston come together and force the mixture from those areas to "squish" into the chamber, where the spark plug and burning mixture reside, so you achieve a more complete burn.
The quench area also runs cooler than the rest of the chamber / piston. These lower temperatures are where the "quench" comes from.
When properly designed, the quench areas can have a tremendous effect on the quality of combustion, and allow higher compression ratios, and due to this they are considered "artificial octane" by scientific types.
Bottom line is "properly designed, quench is good".


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

434 stroker
US Navy retired

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
dawg is offline  
 
post #4 of 14 (permalink) Old Jan 9th, 10, 05:28 PM
Senior Tech
Todd
 
Join Date: Aug 2006
Location: Henderson, NV
Posts: 1,664
Re: Tell me about "quench"

I'm going to the bar in about an hour to quench my thirst.
Vegas69 is offline  
post #5 of 14 (permalink) Old Jan 9th, 10, 06:11 PM
 
Join Date: Apr 2007
Posts: 183
Re: Tell me about "quench"

"Don't get overly concerned about it. "

NO, get seriously overly concerned about it, doing it wrong can break an engine.

Quench (squish) is the distance from the flat deck of the piston top to the flat deck of the combustion chamber, measured in thousandths of an inch. Good quench distances are between .039 to .045, measured with the piston at TDC.

If quench distance is too large, mixture will migrate out of the quench area, letting that area go lean, heat past reasoable levels, and cause detonation.

If quench distance is too small, mixture will be pushed out of the quench area, leaing the chamber out, and causiong heat, detonation.

Correct quench distance holds mixture in the quench area, letting the piston cool form mixture, and cool down the side of the piston to the top ring. .

Example of bad quench, too large, piston down in the bore .025, .055 compressed head gasket, add .025 and .055, distance would be .080, way too large. too small, piston at zero deck, flat with the top of the block, .020 steel shim head gasket, distance too small, .020.

Correct quench examples, piston down in the bore .022, .020 head gasket, distance is .042, just right. Piston at zero deck, .044 thick head gasket, .044 quench distance. Perfect.

YES, be very overly concerned about quench, it makes a BIG difference in any engine. I have seen engines done extremely well, should have been just a terror, but they are dogs, quench is way off.

I had a Ford 289 engine that had been professionally built before I got it, always had tuning/performance/overheating issues. A friend explained quench, and we measured mine, .095. We pulled it apart, engine had a .050 thick pack type head gasket, and Silv-O-Lite "destroked" pistons in it, down in the hole the stock .025, PLUS the destroked piston compression height distance of .020. Quench was .050 + .025 + .020 = .095. I had the block decked .045, made the pistons zero deck, used a .042 head gasket, quench went to .042, NO OTHER changes except new gasket set, engine stopped overheating, stopped being a slug. Proper quench is vital.

Regards,

Milton
The Devil's advocate is offline  
post #6 of 14 (permalink) Old Jan 9th, 10, 06:33 PM
Senior Tech
george
 
Join Date: Sep 2006
Location: detroit
Posts: 2,291
Re: Tell me about "quench"

Theres quench and squish.Are they the same?
Yes and no.Depends how you attack it and how you view it.
Quench to me is cooling some far off fuel kernal that wants to auto ignite due to compression heat but is quenched by its close proximity to the cooler running head material.
Squish forces these far off kernals into the burn chamber for a more homegenized mix and requires less ignition advance=less work on the piston top prior to tdc.
Imo..with a street deal,6000rpm with steel rods and limited piston rock,.040" would be safe..clearance wise.

George
68 Camaro
8-71 blown 461 Rat on E-85
fatblock is offline  
post #7 of 14 (permalink) Old Jan 9th, 10, 06:41 PM
Gold Lifetime Member
Steve
 
Steve69SS396's Avatar
 
Join Date: Nov 2005
Location: Modesto, CA
Posts: 2,372
Garage
Re: Tell me about "quench"

When my 355 was originally built in '98 it had a quench distance of .055. Which is supposedly "Bad". It had 11:1 SCR with a 264/274 @ .050" .630 lift 106LSA cam. Cold compression test showed it had between 215 and 230 psi. With a "Bad" quench distance the car ran fine on 91 octane and there were no signs of detonation. It ran mid 11's at 118 on the motor and mid 10's at 129 on a 175 shot in a 3,350 pound car.

Obviously, quench distance that is too tight is of concern and can destroy the engine if parts crash into each other. Unless this is a professional racing engine, I would not worry if your quench distance is greater than .040"

Quench is not the only factor affecting detonation in an engine.

'69 Camaro - 429 SBC Dart Iron Eagle 9.325" block, Crower crank, Crower 6" billet rods, Ross pistons (10:1), Total Seal rings, AFR 245 heads, T&D steel body shaft rockers, Cloyes Timing set, custom ground 4-7 swap solid roller 274/286 @ .050" with .704" lift, Dart single plane, Holley Dominator EFI on E85, Injector Dynamics ID2000 Injectors, Stef's #1705R oil pan, F2 Procharger, Lemons 2" primary 4" collector, ATI 9" blower converter
Steve69SS396 is offline  
post #8 of 14 (permalink) Old Jan 9th, 10, 06:54 PM
Gold Lifetime Member
"Tri-Tip"
 
Gary L's Avatar
 
Join Date: Aug 2002
Location: Clovis , CA, USA
Posts: 10,079
Re: Tell me about "quench"

I will back you up on that Steve. My little 302 is at .053. No problems.

"Government is not reason; it is not eloquent; it is force. Like fire, it is a dangerous servant and a fearful master." ..... George Washington

Gary,TC Member with a Lemans Blue/Ivory 02D X33, DZ, M20, MS, flat hood. Only the BU code rear end is original.
Gary L is offline  
post #9 of 14 (permalink) Old Jan 9th, 10, 07:12 PM
Senior Tech
Rich
 
Join Date: Jul 2009
Location: North Jersey
Posts: 1,463
Re: Tell me about "quench"

There are 2 different quench terms.Quench area which is the amount of deck surface the cylinder head has that is directly over the flat part of the piston top,and quench distance which is the space between the top of the flat area of the piston and the deck of the cyinder head.Quench distance will usually be measured in thousandth of an inch and is adjusted by either milling the deck of the block to decrease the distance or using thicker head gaskets to increase the distance.For street and strip engines with steel connnecting rods a safe quench distance would be between .035 and .040",while a steel rod race engine can go as tight as about .030" but aluminum rod engines need as much as .070" clearance when cold to allow for expansion of the rod when the engine heats up.Tighter quench raises compression and allows the quench AREA to do it's job more effectivly.

Quench area is not really adjustable,but you can improve it by selecting cylinder heads with better combustion chambers.When a combustion chamber is too big and the spark plug is located all the way at one end,there is a higher chance of secondary combustion or detonation taking place,and the fuel charge that is in the chamber is more stagnant and may allow some of the fuel to not burn fully.Engines like Oldsmobile V8's have a combustion chamber that covers almost the entire top of the cylinder,and because of this it doesnt tolerate higher compression as well as an engine like a small block chevy which has a chamber that only cover a little more then half the cylinder.In the Chevy engine the quench area forces the mixture toward the spark plug side of the chamber as the piston gets near top dead center,then most of the charge is near the spark plug and ignites quickly.In the case of an engine like a Chrysler Hemi where the entire chamber is shaped like one big dome,and there is no quench whatsoever,the spark plug is located right in the middle of the chamber so it ignites all the mixture evenly from the center out.That setup is actually superior to any quench setup and is why very high boost engines such as top fuel engines work so well with this setup.Whenever a chamber is shaped like a wedge with the spark plug at one end,the more quench you have the better.Modern cylinder heads that tout heart shape combustion chambers are actually designed to give maximized quench area by only having the combustion chamber in the area directly around the valves and the flat area of the deck is increased.Such a setup tolerates more compression,and burns the fuel more completly which makes both more power and less emmissions.It is just on of the reasons that engine like the chevy LS engines have a leg up on older designs.
So now you know.
RichSchmidt is offline  
post #10 of 14 (permalink) Old Jan 9th, 10, 07:40 PM
Senior Tech
AJ
 
Join Date: Jul 2006
Location: AUSTIN TEXAS
Posts: 3,842
Re: Tell me about "quench"

Some what off topic but, I'd like to see a medium chamber head with a domed piston and a normal deck height with around 11:1, then an identical set up but compression is achieved with a small chamber head, milled block and thin head gasket to achieve 11:1, I guarantee the motor without the big dome would make more power.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
ace's68 is offline  
post #11 of 14 (permalink) Old Jan 10th, 10, 10:49 AM
 
Join Date: Apr 2007
Posts: 183
Re: Tell me about "quench"

Excuse me, but the two terms mean the exact same thing. Quench is what automotive people call the distance. Squish is the exact same thing, what MOTORCYCLE people call it.

And, sure, some engines may tolerate the distance being a little more, or less, but if the distance isn't optimal, the engine isn't doing what it should be, and can be better. Just because "it works for me" doesn't mean it works as well as it should/could.

How do I know all this? Well, I know a fair amount of really good engine builders, and two factory engine design and development engineers, factory racing and production engines, both automotive and motorcycle. The person that helped me fix the Ford quench problem has done both auto and motorcycle engine development, for many years.

As I alluded to, saavy engine builders adhere to the quench.squish rule very closely, others build 'em as they see 'em, and if they have problems, go every other direction than this distance for answers, when it is the simplest of answers, the distance isn't correct, within the tolerance for optimum performance/efficiency.

Nobody is forcing anyone to set these distanced any way other than what they want. I, however, will continue to do it the way the actual experts say to do, and have NO trouble with my engines.

Regards,

Milton
The Devil's advocate is offline  
post #12 of 14 (permalink) Old Jan 10th, 10, 12:17 PM
Tech Team
Dave
 
Join Date: Jun 2009
Location: Nocal
Posts: 37
Re: Tell me about "quench"

What effect does a dished piston have on quench? Just curious.
stratrex is offline  
post #13 of 14 (permalink) Old Jan 10th, 10, 12:25 PM
Gold Lifetime Member
"Tri-Tip"
 
Gary L's Avatar
 
Join Date: Aug 2002
Location: Clovis , CA, USA
Posts: 10,079
Re: Tell me about "quench"

Aren't full dished pistons a smog thing....low compression? Maybe "D" shaped dish still gets the quench distance.

"Government is not reason; it is not eloquent; it is force. Like fire, it is a dangerous servant and a fearful master." ..... George Washington

Gary,TC Member with a Lemans Blue/Ivory 02D X33, DZ, M20, MS, flat hood. Only the BU code rear end is original.
Gary L is offline  
post #14 of 14 (permalink) Old Jan 11th, 10, 08:37 PM
Tech Team
Dave
 
Join Date: Jun 2009
Location: Nocal
Posts: 37
Re: Tell me about "quench"

Yea, I'm sure it's for smog. Put zz4 aluminum heads with 58cc chambers on it and the zz4 roller cam. Not sure what the compression is now though. Runs good on pump gas. No idea what hp it's developing. Put in a '69 nova.
stratrex is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome