|10-01-2010 08:36 AM|
|10-01-2010 06:31 AM|
Its a combined effect, the heads usually present more of a problem than the pistons though so they are worked on more. For pistons you can use flat tops and be okay, for the chamber you need good flame propagation characteristics.
|10-01-2010 12:56 AM|
Well all this and back to the process.
This whole quench effect,, I was under the impression that piston design has more to do with the effective gains than the head design.
Chamber design is more or less riding shotgun. There is the quench distance always constant and grooves effect it but I would think that pistons have more to do with whats going on,,,grind if you want.
|10-01-2010 12:41 AM|
|Silverback||that's sort of simlar to the may fireball jag heads. there was almost no volume under the intake valve and all the volume was under the exhaust valve. The production setups were all in the high 11.x to 12.5:1 compression and I believe that they considered running as high as 14:1 on pump gas|
|10-01-2010 12:10 AM|
|4 Jaw Chuck||
Thanks for those links Tech, I had forgotten about Jim and his designs for low volume combustion chambers.
Increased dimension quench zones is essentially all your doing with the grooves anyway, I'm sure he found the perfect clearance that works with a particular fuel for his heads...not so great for Mom and Pop who get varying fuel quality throughout the year though.
Makes one wonder what you could do with a flush mounted valve in the chamber and all the volume in the piston...though its been tried and piston weight becomes excessive for performance applications not to mention durability.
Jim Fuelings accomplishments makes Mr. Singh look like Homer Simpson nailing his thumb to the wall though doesn't he!
What a career!
|09-30-2010 08:01 PM|
|Silverback||Like I hinted before, I don't think it would... a lot of his ideas are similar to Larry Widmer's, and I believe that the effect that they are trying to achieve with their chamber designs accomplishes what it does in the opposite way that that I believe grooves do.|
|09-27-2010 11:47 PM|
Now, I have to wonder how Singh grooves would work on the Feuling head.....
|09-27-2010 10:14 PM|
Will grooving chambers get you there? I don't know, that engine was before I'd experimented with grooves, I haven't run _that_ much compression with grooves, yet, and I get the feeling that they are not entirely compatible with what I was experimenting with before I ran across the grooving idea. I think that AB probably could answer that.
BTW, there have been production engines with compressions in the 12.5:1 range that ran on pump gas.
|09-27-2010 08:42 PM|
The best way to increase the combustion chamber size is to work the valve
shroud. It's not difficult at all, clean the head and apply layout fluid, or paint
it with a permanent type felt tip marker. Scribe the bore diameter on the
head deck, avoid cutting in this area at all costs. (people do cut bigger than
the bore, don't go there now)
Install a set of valves that you are willing to ruin. Use the chamber I posted
earlier as a guide. Think about how the fluid flows around the valve face into
the cylinder. I can post more pictures if needed.
|09-27-2010 08:03 PM|
so lets just say your 11.8 compression on 87 octane is BS as everyone else knows
what would be the best way to increase the combustion chamber size. I am doing some research on unshrouding valves but I am not sure if this is something that I would be able to do. I would like a link or even a book link to some good information on doing this. How many cc's can you pick up by doing this?
|09-27-2010 08:02 PM|
|09-27-2010 07:58 PM|
|09-27-2010 07:14 PM|
|crussell85||Silverback, so if the engine started out at 9.8 compression how did you get to 11.8? Do you have a link to this other thread that you were talking about this car in?|
|09-27-2010 08:29 AM|
|4 Jaw Chuck||
Thats pretty amazing considering a friends brother managed to get 31-33 mpg in 1991 from his 3.1L Firebird when it was broken in, and that was Imperial mpg not US mpg which works out to 26-28 mpg US.
That bird was slippery and not that heavy too, surprisingly good performance from 140hp with the 5 speed.
Your car wasn't black and called Kitt by any chance? David Hasselhoff is that you?
Knight Rider Intro
|09-26-2010 11:01 PM|
I've posted full details in other places and had nothing to do with this thread but the car was an '83 Trans Am with a crossfire injected (basically throttle body with long intake runners) 305 with a TH700r4, 3.23 gears and fairly tall (27") tires, headers, 2 high flow converters and no muffler. No dramatic changes, just a good, well matched combination with years of tweaking and small changes till it got as good as it was going to get (when I was in college and didn't have anything better to do besides playing with my car). It helped that it wasn't incredibly heavy and was one of the most aerodynamic body styles ever built, and I took that further also. The engine started with a good combination for this kind of thing also, small bore, high compression (9.8:1, which was really high for early 80's with iron heads), good valve size, iron heads, long, narrow runners that.
After college my wife (then gf) lived in RI for a while while I was in the DC metro area, so many weekends I'd head up that way and that is where I clocked some of the best MPG numbers, and it wasn't uncommon for me to make it up there (over 400miles), drive around a bit and not have to get gas until i was headed back. It also still managed some pretty crappy mileage around town, in the 16-19mpg range, which I always attributed to a primitive ECM setup in it.
Funny how now I'm pretty happy now when I can mange 20mpg in my LT1 powered TA or either of my TPI powered cars (TA and formula)
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