CC'ing the combustion chamber

[acannell]

QUESTION #1: head volume for a G head

im trying to find a simple "G head volume from 198x is xx cc's" but i've yet to see it in mopar performance 4th ed. BUT:

pg 93: "the fast burn chamber typical of the 4105782 casting is approximately 6cc smaller than the other chambers". for what THATS worth.

so we know the G head is 6cc bigger than the 782 fast burn head.

pg 87: they run through an example of calculating compression ratio for a 2.2L where they list the cylinder head volume as 55cc's, but they dont specify if its a G head.

i just dont see the g head volume listed directly anywhere. wow that is so lame. i am pretty sure it could be calculated from the vast array of other numbers in the 80 to 95 pg range of this book though.

QUESTION #2: piston dish volume for a 2.2 turbo I

MP 4th ed. pg 83: "The Turbo I piston has a 4.8mm deep dish in the top. The actual deck height of the piston is the same as on the standard piston, but the engine's compression ratio is dropped to 8.1 (nominal) by the 8cc dish". I'm pretty sure this is referring to a 2.2 turbo I and not a 2.5 turbo I piston, because next to this snippet is a table listeing the 84 to 88 turbo I piston dish at 4.84mm, while the 89 to 92 2.5L turbo I is listed at 5.10mm.

QUESTIONS #3: stock compression ratio for an 85 2.2L turbo I

from a FSM for 1986, 2.2L turbo I is listed at 8.5 to 1

strangely, MP 4th ed pg 83 lists "Approx. C.R." as 8.10:1 for 84 to 88 2.2L turbo I

make up your mind chrysler.

[Tbone]

>>The main question is Why? lower CR and more boost will make more HP on pump gas.<<
The main reason is that I want this car to be fuel efficient (when not under boost) and powerful. If I go much lower on the compression ratio, I'm afraid I will loose some efficiency. I'm not looking for crazy horsepower since I have an early block. I am limitied to 225-250 hp.

Thanks for the info, guys. I have a better idea of what the head volume is, but still not exactly sure. If I use 8cc for the piston dish and 0.068" for the head gasket, then I have to adjust the head volume to 49.9cc to get a compression ratio of 8.1:1. I have seen the compression ratio listed as 8.1:1 more often than 8.2:1 so I will assume that is correct (8.5:1 doesn't seem right). Although, if I adjust the head volume to an even 49cc, the compression ratio goes to 8.2:1. If no one knows for sure, I will assume 49.9cc is the correct head volume for the G-head. Once I cc my head, I will have a better idea of how much material I grinded away.

[Tbone]

I did a little bit of CCing on my head and piston. Found the piston has a 9 cc dish. Some of the literature said 8 cc. One of the chambers measured 53.8 cc and the other measured 54.1 cc (I had a few issues with the first one). That is also different from what I have heard from others. I know my head probably has a little more volume because I deshrouded it. The other thing I found is that the compressed head gasket thickness is not 0.068" That is the un-compressed thickness. The compressed thickness is around 0.040" but I don't have an actual measurement on that yet. With those new numbers, I found my compression ratio to be 7.79:1. That tells me I need to mill my head by 0.018" to get 8.1:1 CR. I hope this is right. I don't know if I can trust it because I used 2 other compression calculators and got 2 different answers. The other two calculators seemed wrong because they showed my compression ratio was higher than before. That's not possible. If I figure this mess out, I will let the rest of you know.

[puppet]

Quote:

Originally Posted by Tbone The other thing I found is that the compressed head gasket thickness is not 0.068" That is the un-compressed thickness. The compressed thickness is around 0.040" but I don't have an actual measurement on that yet.

This ain't a MP gasket your measuring. Everyone I've mic'ed comes out to .065-.068" compressed dimension.

[Tbone]

I did a quick check on my new, un-compressed gasket and it was measuring right around 0.068" at the edge. I will check right at the bore and see if that makes a difference. Once I find my old compressed gasket, i will measure that and report back.

[Tbone]

This is how I CCed my combustion chamber. Don't laugh. That is a medicine dropper but it has fine increments (2/10ths cc).

[Tbone]

BTW, I used grease around the perimeter of the combustion chamber to help seal the plexiglass and on the valves to help them seal. I also used clamps on the plexiglass to hold it down tight. I have a few more cylinders to do.

[Tbone]

I averaged around 53.9cc between the 4 combustion chambers. I also added in the volume of the head gasket (thickness and bore). This helped my numbers come out perfect assuming I used 8cc for the piston dish instead of 9. I measured 9cc but I must have made a mistake. That makes the stock head volume 52cc for the G-head to get an 8.1:1 CR. I figure I will now need to mill the head 0.019" to get back to 8.1:1 CR.

BTW: I double checked my head gasket. The new one averages 0.076" thick before being compressed. I am assuming it compresses to 0.040".

I am planning on adding 2 singh grooves per cylinder and radiusing (edging) the squish pad pretty agressively. I have heard good things about doing this. Anyone else have an opinion? Below is an example of both, but not my head (swirl head, I think).

[speeduphoria]

there is a long thread on the other site about the singh grooves, nothing has been proven or dis proven AFAIK

[Tbone]

I read a lot about it on mpgresearch.com. MPGMike and Automotive breath have been doing it for years. I willing to give it a try.

[acannell]

wow that singh groove site is pretty much the epitome of rambling nonsense.

i'm thinking that in the past 30 years that one of the thousands of engineers and scientists who spent their lives trying to increase power and reduce emissions cheaply probably would have noticed this along time ago since it would have made them a millionaire and famous. yeah but what do they know right? this guy sounds EXCITED and says all the things I want to hear! like obama!

why do people always latch on to mystical crap? as soon as there is something to worry about in the world like gas prices out comes the bull****. why dont we do a rain dance and sacrifice some sheep while we're at it.

gotta go buy some more dr bronner soap.....

engineering and emotions NEVER go together. if something is proven its PROVEN. if its not its NOT. there is no middle ground. evaluating singh grooves could have been completed LONG ago and absolutely determined if it worked or not. there is no "opinion" here. there are ways to absolutely confirm this kind of thing. a dyno and an exhaust gas analyzer could have settled this years ago and if it was real singh grooves would be in every engine today.

[Tbone]

You might be right. There needs to be a definitive test. The people I have read about say they have positive results, though. And I'm not talking about sommender singh's site.

[detobias]

Tbone - you are doing some fine work , and you are on the right track.. BUT

I'm not sure why you are intent on maintaining a near stock CR... I guess if it was me I would just get the head whacked .030 or so and know that my CR was a bit higher than stock..

having said that - you will KNOW much better than most of us what your engine is actually running

PS I am running the Singh grooves and can show you pix of the clean portions of the quench pad on my swirl head where the Singh 'jet' has done what it is sposed to do - blast the unburned HCs out of the quench pads 'crevice'

[Tbone]

>>I'm not sure why you are intent on maintaining a near stock CR<<

detobias:
I have been struggling with that decision for a while. If I run less CR I can actually run higher boost and make more power, but I don't think that's necessary because I'm not trying to make a drag car. If I raise the CR, I can have more power with less boost, but it will limit me to how much boost I can run before detonation problems. If I pick the stock CR, I figured I would be at the most optimal CR for the ECU settings I have (regarding spark advance and fuel tables). I want to get a custom cal in the future, but I really wanted to make sure the car is going to run first before I buy a custom cal. I guess I am a little nervous about changing the CR without having a custom cal for that new CR. On the other hand, If I am being too conserative, I can be easily swayed. I would rather run a higher compression ratio to get better efficiency and good gas mileage, but I don't know if I will get detonation or not with my stock cal.

Does your oil stay cleaner with the singh grooves?
Did you raise the CR with the singh grooves?
Any problems with pinging or detonation?

[scott_s]

That pic is of my spare 782 I had on the car. With that head in its non grooved, non ST valve form I had to run 91. Tried 87 once, she would get knock retard like crazy. Could not drive it, it was that bad... With the above changes, 87 octane no problem, boosting to 14psi, that was with a S70 turbo and log exhaust mani. Before it was the stock Tii turbo and a ported exhaust mani. I do not recall what the head CCed out at.

Btw, there was a very in depth set of dyno testing with the grooves. I believe the info was release in January.

Detobia, I am interested in seeing a pic(s) as well