I will be doing the same thing soon as i get the bung welded in. I believe the optimium is 14:1.You should be able to contact the people who made it and get setup info. I have the innovations setup which i purchased from dobeck. I will call them to get proper guideance when the time comes. I aslo purchased the dynatek fs, which should be here this week.

 

14:1 is optimum for fuel economy and emmissions and is what the manufacturers shoot for, but it is NOT where max power is being made. this is why a motor tuned for max power will have a dark plug, and people who shoot for clean tan plugs in the tuning process will not be making max power.

 

I've been thinking about this for a day or two (I know, I know, I should stop thinking) about this deal. The more I think about it the more pissed I get.

I mean really, you ordered an 11.5 to 1 piston, that is what you should get!!!!!!!!
After all, these things are not like a small block Chevy that you can get a 64cc head or a 56cc head or a 76cc head, open chamber, closed chamber or whatever. In the chevy example it will throw the compression all over the place depending on the cc of the head.

This is not the case with the Bomb head. The only difference is might be on how shaved it was or the gasket crush thickness.

What's the deal here? Why don't they just tell you the correct compression?

 

I was thinkin the same thing Doc, didn't want to take the post into a new direction, but now that the ice is broken I think everybody running one of these new dandy 11.5:1/13:1 confused arsed pistons otta run 'em on pump fuel at as high a rev as possible til the detonation destroys the motor and then all jump on one big bandwagon with a classaction lawsuit.
there sure is a lot of silly compression ratio stuff going on man, pistons not really what they are billed as, some high some low, some going double up on the base gaskets to get the compression down [img]i/expressions/face-icon-small-confused.gif[/img]

if a guy has to mix fuel, might as well go all the way to 14:1 and run straight race gas (I did), cause it aint the money its the hassle, and running pure race gas is much easier than farting around with a mix IMO. if a guy buys an 11.5:1, its cause he doesn't want the hassle of aquiring race gas, and wants the convenience of pump fuel, and then later he learns its actually 13:1? If this is accurate info, and if it was me, I'd be really pissed.

 

wow, this kind of makes sense now. Last Spring i bought a JE 11.5 piston, threw her in and within 2 months of running it, she blew to pieces. I ran pump premium all the time and couldnt figure out why she blew up. well it kind of sucks that they actually are 13:1 because that would have saved me $1600 in a motor rebuild.

 

You guys are right, the whole point for me going to 11.5 was to not touch race gas. At this point, I would have gone with one of the 14:1 since its really not the cost, but the hassle of race gas. I now have to keep separate gas for my DS from all my other vehicles.

I could run a thicker head / and or base gasket, but what would that do to my cam timing. Does anyone know how much advance that would give the cams? I assume it would advance the cams since it effectively shorten the timing chain.

And, I should not have to deal with any of this as it really should jsut be an 11.5 piston.

Thanks guys!

Scott

 

<div class="FTQUOTE"><begin quote>if a guy has to mix fuel, might as well go all the way to 14:1 and run straight race gas (I did), cause it aint the money its the hassle, and running pure race gas is much easier than farting around with a mix IMO. if a guy buys an 11.5:1, its cause he doesn't want the hassle of aquiring race gas, and wants the convenience of pump fuel, and then later he learns its actually 13:1? If this is accurate info, and if it was me, I'd be really pissed. </end quote></div>
Ding, Ding, Ding, Ding, this paragraph says it all!!!!!!!! And well said it is!!!!!! TheStir and most other people that do these builds are looking for that 11.5 to 1 number because that is the magic number you can run on pump gas with an aluminum head and water cooled.

I have delt with this crap before, so that is why on my first post I put "true" in quotes. If I did one of these builds I would tell the seller of the piston that I'm going to cc the setup and it had better be within a 1/4 of a point of compression or otherwise the stuff is coming back and I get a full refund.

I have a Mopar 340 that does not like pump gas. At least the crap they call pump gas today!!!! When I was driving the car it was a pain in the butt to deal with this. I always had to have octane booster with me and most of the time I had 3 people waiting in line for the pump I was using and they were all pissed off when I was trying to get this stuff in the tank. What a pain!!!!

I'm glad you people feel the same way I do. I'm pissed and I don't even build these engines!!

 

e-mail to JE:

Good Morning,
Based on recommendations of other DS650 owners I purchased a stock bore 11.5:1 piston for my DS650 due to the fact that it could run on pump premium 93 octane fuel. I installed the piston on my 2002 DS and was using a wide band O2 meter for tuning. I was on the rich side and was leaning it out and started to have issues with pining.

At this point I posted some tuning questions on two internet forums, and got a reply from one engine builder that the new 11.5:1 piston from you for the DS650 cc'd out to be around a 13:1 piston.

The whole point in my choosing the JE 11.5:1 piston was to keep from having to use race gas, but it appears that that is the boat that I'm in now. Can you confirm to me that your 11.5:1 piston is really an 11.5:1 compression ratio?

I have lined up a local shop to cc my DS650 and let me know the true compression ratio. I do understand that there are some variations in all engines, but I would expect that this would amount to less that 1/4 point of compression ratio, especially on an original engine like I have using OEM gaskets. If the piston comes back outside of this range I would like to pursue a refund so that I can get a piston that truly meets my needs.

Thank you for your time,

Scott Mahnke


I will keep you all posted.

 

Sorry to but in, are you talking about Samoa Dunes in Nor-Cal ? if so hope to see you there or around the Redding area sometime

 

<div class="FTQUOTE"><begin quote>Originally posted by: new2-ds650

Sorry to but in, are you talking about Samoa Dunes in Nor-Cal ? if so hope to see you there or around the Redding area sometime</end quote></div>

The ones outside Eureka? How much riding is still there? Last we heard they closed it down to just the beach, can you give a little info. I am in Corning, and those by far would be the closest for some day trips.....