Interesting comment..

[Chuck Leeper]

on the Speedtalk engine forum, regarding turbo head design...
"Do these heads almost like you would do a set for a normally aspirated combination except,

(1) make the intake and exhaust seats .055 wide. Use 45° seat angles (wider seats will lower valve operating temp.)
(2) Intake throat at 90%
(3) Exhaust throat at 90%. Need to keep the exhaust throat this size for two reasons. The seat ring footing on the register needs to be strong and if your running a nail head Inconel (which you should) it will breath better.
(4) Do a "soft" chamber. In a turbo engine you want ZERO quench. The chamber must be total soft with no squish/quench anywhere in sight.
(5) Do not run a dish piston if you can help it. In high boost application it will pop the top of the piston right off. Putt all the volume in the chamber and piston to head clearance.

A link to the thread.. [requires registering to get into the advanced engine forum.]
http://speedtalk.com/forum/viewtopic.php?f=15&t=28450&start=15

 

[turbofabricator]

Uhmmmm................great website. Go there often. That info is pretty much interesting. I would never argue with Darrin Morgan. He's forgotten more about cylinderhead development than I will ever know. It contradicts everything I know about combustuon chamber design. I surely don't know everthing though. Maybe Buick had their heads up their butts too with both production and StageII development. But.............Buick still holds the record at Indy, so probably not.?

 

[gtfrede]

So how does this information apply to the lc2? I'm no expert with our motors and am wondering how our cylinder head differs or is similar to this theory...what about the 231 makes it a good turbo motor? DID buick know what they were doing?

Just mixing the pot so this thread can go further with some good engine theory and information....come on wisemen lets hear some thoughts

 

[Jerryl]

Subscribed!

 

[Turbo-Archie]

What is a soft chamber?


..

 

[DoubleD]

from how he was describing it, the chamber has absolutely no quench zones left (maybe reducing the number of sharp edges at the edge of the quench zone?). Probably looking to equalize the cylinder pressures over the top of the entire piston versus highly concentrated pressures in the quench area? reminds me a little about that "singh's grooves" article that was on here a while back. seemed like his concept was to relieve some pressure from the quench area.

-D

 

[KL Mallender]

So called "soft chambers" are not in your best interest, nice theory and valid if other protections are used to prevent upper ring land removal, I'll guess that many looking at this do not really understand the concept of "quenching", it is not about flame travel.
Detonate an open chamber exposes the rings the ability to grab the cylinder wall, and thats as far as I care to discuss the matter.
Good luck,

Kevin.

 

[turbofabricator]

Interesting information. I too feel quench is needed especially for a street/strip application. A soft chamber "may" work in a all-out turbocharged application though. Same as a hemi works well in a Nitro application, but not in a NA application. Boost solves and creates many problems. Kevin, why do you not wish to discuss this further? Oh, please do keep the info flowing. The only way to help others out. One of my pet peeves is not sharing info that may be vital to others. If it's classified info, then fine. (don't want to violate ITAR rulings)

 

[bison]

So they want us to run hemis to avoid quench and avoid dished pistons. Good luck to that and have a nice day. Guess 99.9% of turbo applications out there are not ideal.

 

[Chuck Leeper]

Next....
How many of the above respondents have registered, and read the entire thread???

 

[charlief1]

Next....
How many of the above respondents have registered, and read the entire thread???

Haven't read the whole thread Chuck, but I've been a member over there for a while. They really do have some interesting tech threads over there and it is worth doing some reading over there.

 

[turbobitt]

So they want us to run hemis to avoid quench and avoid dished pistons. Good luck to that and have a nice day. Guess 99.9% of turbo applications out there are not ideal.

I take this as comments on what they would prefer to see, but not absolutely necessary. Much like everything else, it’s just one opinion on an optimal design for a particular engine platform but may not be applicable for all. For example, take the statement about not running dished pistons with high boost. WTF is his definition of high boost ?? Very open statement. "They will pop the top of the piston off" - Is this true to every dished piston design ? If you look at the load path of the piston to the pin, I would highly doubt this to be true, at least for small bore configurations vs. big bore configurations.

Allan G.

 

[turbobitt]

Next....
How many of the above respondents have registered, and read the entire thread???

It appears you quoted the highlights, Did you not post this for us to comment on ??

Allan G.

 

[Dusty Bradford]

"Soft" chambers are used by nitrous motors as well as boosted and will increase power and reliability when pushed hard. This is geared more towards heads who have very efficient chambers intended for n/a use. When using these heads for lots of nitrous or boost there is a large benefit to softening the chamber.

 

[Turbo-Archie]

Thanks Dusty.

Do you consider a stock 3.8 head "soft"?


..

 

[gtfrede]

Write what a wealth of information there! That will keep me entertained for a while....registered and reading now

 

[Chuck Leeper]

It appears you quoted the highlights, Did you not post this for us to comment on ??

Allan G.

I posted a part of the thread and noted that you must register to see the entire thread.[Currently, 49 replies to the thread]. Might be some useful info there. That's the purpose behind my posting it. Accept or reject the premise, opinions, etc, and draw your own conclusions.
I don't have a dog in this hunt....

 

[bison]

"Soft" chambers are used by nitrous motors as well as boosted and will increase power and reliability when pushed hard. This is geared more towards heads who have very efficient chambers intended for n/a use. When using these heads for lots of nitrous or boost there is a large benefit to softening the chamber.

Those types of heads are the exact opposite of what is commonly used on street application where the car is going to be driven thousands of miles, be emission tested, and be able to have thousands of miles of service. Now if I was building a max effort 116+ octane, or alcohol boosted engine I'd be all over that design.

 

[NCTURBOS]

Uhmmmm................great website. Go there often. That info is pretty much interesting. I would never argue with Darrin Morgan. He's forgotten more about cylinderhead development than I will ever know.

Agree, and also believe he's not really talking street car application in the above listed thread. For the most part Darrin's cylinder head design involvement is for max effort applications.


K.

 

[ijames]

One of the posters in that thread (Erland Cox) said that in his opinion quench was fine up to about 15 psi boost but over 20 psi you needed to get rid of it or it would cause detonation. That puts almost all of us into the no quench group . No one else commented on that (so far), and Darin hasn't personally posted in the thread.