Looking at our heads...we have good fast burn shaped heads. All flow tries to swirl at the exhaust valve. Now this is all good and dandy when its sucking in air...But how about when it compresses?
Small fuel malucules (spelling??) when its swirled..then when it goes to comprssion stroke..large fuel malucules. The quench ariea is suppose to help "swirl" or "shot" the fuel/air mixture again to keep it mixed and keep large molucules from forming. I can see this vaigly happening at the edge of the pistons top. Everything else is dished. The iron head piston should help in quench. This will keep it mixed real good. THough..the skyrocket in CR will make anyone think twice about boosting it. So then they look at the Iron head...NO BOB..it has the worst quench area known to men. It has no swirl..and it has no directin to air flow. If you ever notice..Iron head engines need more spark advance than the aluminum counterpart. Also..their BSFC is higher than ours. About .03 differance or so stock. The spark advance by itself will mess with tq. Ever notice we have more tq than iron head. 2.8,3.1, or 3.4.
So now my delema. You all know im after 500 ponies. So im looking at every creves possible for more. I've been planning up a piston top for a while. But I don't know if JE or any MFG would make it. So Im now stuck with either finding another engine that has same dimentions as our engines pistons with iether a D shaped dish (like turbo 2.3 fords) or a oval dish in the middle. Get where im comming from?. The other is using a forged iron head piston and keeping the boost down alot :roll: . Though...I think theres a trade off there. I've seen some volvo guys make awsome numbers with high compression and boost. Hmm..14:1 and boost..sounds crasy enough to work :twisted: . With this..my spark advance will be less..thous bringing up the tq alot. Idealy..I want to bring my BSFC to almost .4 or .45. If you ever have a turbo engine calculator..plug those numbers and see what the idlea "HP" will be. You'll be amazed.
Airflow without direction won't do jack. ("read swril quench piston" hotrod mag oct. 98. Also the lates on hotrod about this).
Just though I would let you'll all know what im up to now. :twisted:
http://img.photobucket.com/albums/v334/TurboGTU/TurboGTU2/pistondesighn.jpg
Excuse the 2nd grade artistic skills :lol: . But you get the picture. I want the piston to be flush with the block..if anything..about .005 out of the block. I wanted it to be dished on the exhaust side and on to the intake side. But I have changed my mind after rereading "softhead" over and over again. So now..I will have a flat top with a dome on the intake side. That way all the mixture will be on the exhaust valve pocket and where the spark plug resides.
BTW..this leaves about 18-20 cc of chamber :shock: .
This inturn will make for a "faster" burn. Less spark advance and better cam timming can be utilised. Less fuel and air is needed to make X amount of power than expected.
Cool eh.
I've also confirmed my head porting based on "soft head". DAM I'M GOOD. 8) . But im still skeptical if the log manafolds will let the exhaust ports reach mach levels. I see cylinders 1 and 2 reaching mach levels..but 3 and 4..nope..5 and 6..somewhat. Now I'm looking at a shorty header desingn.
Well, what I can add for now is the raised crown of the stock piston has 2 strong benefits. One is for swirl management, the raised crown ridge helps hold the swirl while the air is rushing in and down some :shock: and doing its swirl thing allowing things to homogenize well, then when the combustion happens, kind of having a contained pocket with the crowned ridge and sunken dish to keep the combustion pressure more centralized on the top of the piston which is good for piston skirts to cylinder wall contact and piston pins and making better power with less frictional losses. Also without the ridge the fuel rich air coming in would have more oil coated/lubed cylinder wall area to wash against, a small benefit there but good none the less. All this is good for the combustion part and swirl management but next is the larger meat given from this raised crown increases the strength in a very weak area, that being right above the top piston ring land, and we have seen some abused engines/pistons where this ridge came off, just think if it was a thinner ridge over the top ring if it was a flat top assuming the top compression ring in the same location relative to the stock piston, and the loss of the benefits above containing somewhat the swirl and the cylinder wash.
As for compression, there is only one tuner guy (Corky Bell) that made a big mistake not being more thorough in his explanation when he stated lower the compression for turbos was not the best thing when it actually is 90% of the time on the engines out there. He gravely forgot to mention, at least, that no aftermarket company (unless you can R&D and make your own :roll: :lol: ) has been able to design a piston/head combo from scratch to allow high compression and a turbo setup. Some super tuner/builders have done this for drag cars but these still run super high octane not just for the high boost levels they run. Hell, Subies, AMG, McLaren (the other McLaren), Evo and many others with their superior knowledge of engine design and building still drop their compression rations when going forced induction.
JE is a very good company able to do custom, as with Wiesco and others, none are a waste or risk of money.
Jeff M
One last thing, since you are resourceful and thorough 8) , find some of those charts that show VE or BMEP or %drop in power from a lower compression on an engine, then compare to how much more boost a lower compression engine will allow for the same values, I think you will find that power gained from the higher allowable boost is greater than the little that is lost to the engine with a lower compression, which is really only a factor when not in boot/less than 1 psi :!: , boost gets things/VE etc back on track, and then some :lol: . Also know that the charts running around on less power from a lower compression are general and every head will have different results but still in the same direction so the numbers will still be meaningful to use. Good luck!!
Jeff M
I've tried to compare engines with read out BSFC, exhaust temps, and every probe posibble. I've read and reread Lean and mean (hotrod "502 torque monster") and then comprering it to their Blower builds on 454s and so on. MM&FF, Sport compact. They just can't compare. Tooo many varriables. I've tried looking. Nothing made sence. Why does the Ford SHO engine like boost? Why doen't the GM TDC respond like it? So on and so forth.
Then I put the peices together from when I started focusing more on the combustion itself. Vortech technology made sence, Lean and mean('00?) started making sence, swirl quench piston started making sence(98-), "softhead" made even more sence(just recently). I've then researed hard core and found my awswers.
http://www.theoldone.com/articles/itisdifficulttomakehardheads.html
http://www.theoldone.com/articles/The%5FSoft%5FHead%5F1999/
http://www.theoldone.com/archive/quench-area.htm
8)
If I can't get the pistons made..I will just use flatops and bow the exhaust side a few and make some swirl pads. :shock: :roll: . Im not perfect. :lol: I think using flat face intake valves will help.
Interesting readings, thanks for more info-links :D , always good to have someone shake the trees :twisted: !! Being an old guy/me, over they years (won?t state how many :lol: ) I have heard words/statement/approaches from many walks of life, those aggressive, those sedate, those purely factual, those with an ulterior motive (Kenny Bell or Jim Bell actually) and many others, this guy falls into the category of getting tired of dealing with miss-informed friends and customers, getting a bit overboard in an attempt to get people to listen and keep an open mind (and keep learners humble so they can learn, one of the approaches I live by and try to influence upon others so they may benefit as well), many times it takes a hammer approach to get results so I agree with him from that standpoint for sure, and him working to undo the damage from the Internet with people making absolutes when they should not or really do not know what they are talking about. So absolutes are dangerous to live by and can defeat the progress of technological advancement in thinking and manufacturing, but and I quote for his topic, though there were 3 other such related quotes in his statements: ?Once again some of the import crowd have chosen to read the same old worn-out book and ignore what differentiates their cars' engines from less sophisticated others?The shape of the combustion chamber? We have the less sophisticated engine/combustion chamber/piston that the rules still do have some validity to i.e. those old books and charts, we don?t have a high-tech Honda or other manufacturer?s head and piston top design. That is also why GM has been threatening to dump the old tried and true engines like the 3800 :roll: , trying all these new higher-tech for them engine families and approaches, in an attempt :lol: to compete on paper with the buzz words of better engines from other manufacturers, but also gain the many other benefits such as improving emission, fuel economy, power output per liter and such.
Just want to throw this out, listening to a seminar from GM Motorsports and Dodge Motorsports divisions they stated that Mitsubishi had some of the best turbo heads out there, flowing more on the exhaust then on the intake, cool but that also throws a monkey wrench into the old school books of keeping the exhaust to intake ratio of around 80% :shock: if I am recalling correctly :lol: AND!!!...the more HOT exhaust we can get out of the combustion chamber, the more cool intake air (higher boost) we can cram in, the higher the dynamic CR we can run on pump gas and all that, good rule breaking but we don't got those heads :cry:
So aside from that, flat top piston might not be very high-tech in an attempt to upgrade this piece, and I know there are no heads we can swap yet that are high-tech to allow us to change the rule books so till then, we still have to consider, key work there: consider, the old rules for our old school engines still have some application.
Jeff M
Well he did state that if nascar ran high compression with cheap gas on 18:1-22:1 compression..why coun't the more efficiant honda head. The cam does play a role. IE cranking pressure.
This means nascar heads in't too efficiant. So..we can make our "fast burn" head more efficiant and less prone to detonation. Well we will see. The intake valve does take about 7 or 8 CC of chamber thanks to its Bow. :shock:
I'll hunt down a 3.1 iron head short block as a test mule and find some flat face intake valves and see how it goes.
Quote from: TurboGTUWell he did state that if nascar ran high compression with cheap gas on 18:1-22:1 compression..why coun't the more efficiant honda head. The cam does play a role. IE cranking pressure.
This means nascar heads in't too efficiant. So..we can make our "fast burn" head more efficiant and less prone to detonation. Well we will see. The intake valve does take about 7 or 8 CC of chamber thanks to its Bow. :shock:
I'll hunt down a 3.1 iron head short block as a test mule and find some flat face intake valves and see how it goes.
(mainly quoting the bold) might be assuming if no actual data in hand :lol: No "statement" of what is "bad" and just how good the Honda head is, need to know the "range" of good to bad before comparing a brief statement like his :o
Here is a good link/short piece I stumbled on, more info is always good :) . Nice to see our combustion chamber style being spoken of well 8)
http://www.kitcarmag.com/techarticles/65298/index2.html
Jeff M
I want to get me six of these babies to go with some nicely designed heads...
(http://kitcarmag.com/techarticles/p134999_image_large.jpg)
http://kitcarmag.com/techarticles/65298/
Nice dimples :) Seen this thought used to the point of a combustion chamber covered with these, but only good for racing as they holes will fill with carbon and fuel additive leftovers on a street car, unless you burn some combustion cleaner regularly, or some Toulene/Xylene often :twisted: Once filled they will raise compression even more. The valve reliefs look to be for a big lift cam, or to allow the rest of the piston to be high up for good squish while not having a compression that is too high for the octane.
I have some 12:1 GM Forged Pistons that are no longer available, they are flat tops with valve releifs that are a little deeper than those shown on your piston. Have a ton of Cosworth pistons that are just flat tops, and some with valve releifs, not sure the compression right off hand but the results were to run 13.5:1 with some good flowing heads/cam and make 350hp NA running to 8,500 rpms, and Ryan Falconer did this back in the 80s.
Jeff M
The chambers are a fast burn type on the Nascar heads (im looking at and quoting from late 80s Chevy SB ). They are not like ground braking desighen..they been improved now though. No dubt nascar engines are pushing 600-800 hp now though. Its still two valves per hole, compared to twice or quadriple the valves. And a chamber that is not fully designed with a "ideal" valve angles and chamber desing. Piston is still not desighned for the 'best" quench. Theres a difference between a chamber desinged for only HP and one for most fuel econ. Well I guess the best econ won. ..because its uses less fuel for the same power per displacement. :shock: . Well I guess the range would be the fuel and air used to make the X-amout of power per displacement. :?:
Now if nascar had twice the valves in that ara...with the high compression..and the same chamber desighn as the handa head or similar. :shock:
That would be all.
Dang Jeff..If I want to think real hard..I would go back to collage real soon.. :lol: . Wait..I am :shock: . Need that dam paper that says I know what im doing. :roll: ...even if I know what im doing. 8) .
I tend to belive the "small" exhaust port is for N/A engines. As the inlet air is not "supercharged"..so the intake valve is not beeing "oversided" by the inlet flow. "increase" the intake valve size.."increase" the exhaust valve. So we would need about 250-300cfm of flow on exhaust if were "forcing" 400cfm . :cry:
Those dimples you see are called ''Eddies". They help keep the air "moving" on the surface. ..as the pad creates a swirling motion as the piston apporches TDC.
I thought I add to this old post since its related to it. Lemme know what you all think.
http://somender-singh.com
This looks as close to what I had in mind from what I learned from TOO and other people about upping the ante. THis should do nice with flat tops. Even if its a mute mod...theres plenty of FWD aluminum heads out there.