[tamathumper]

Is there a way to tell when detonation occurs, before the "big bang"?

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[Lear35A]

http://www.diamondracing.net/tools/

I used this web tool to play around with the static CR values. It seems to take in all the variables. I came up with the .35 difference using it.

I have a little material removed from both the head and block on my motor. Using the Diamond piston calculation I get almost exactly 11:1 with the stock 1.1mm gasket. With the 1.4mm let's say I get something between 10.6 and 10.65. Apparently most stock motors come in around this cr or even less.



I have the D1R SC Stage 3 which runs up to about 5 psi boost. Everything else is pretty much stock. The dilemna is this. Flash feels quite strongly that running at 11:1 is risky even though that is what the factory says the motor is. The D1R is tuned to a ~10.6:1 cr, not 11:1.



This is just to be a street car. I have both a 1.4mm and 1.1 wide fire head gasket available. What to do??????????

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[vliegwielolaf1234]

[quote name='Lear35A' timestamp='1359121398' post='137975']

http://www.diamondracing.net/tools/

I used this web tool to play around with the static CR values. It seems to take in all the variables. I came up with the .35 difference using it.

I have a little material removed from both the head and block on my motor. Using the Diamond piston calculation I get almost exactly 11:1 with the stock 1.1mm gasket. With the 1.4mm let's say I get something between 10.6 and 10.65. Apparently most stock motors come in around this cr or even less.



I have the D1R SC Stage 3 which runs up to about 5 psi boost. Everything else is pretty much stock. The dilemna is this. Flash feels quite strongly that running at 11:1 is risky even though that is what the factory says the motor is. The D1R is tuned to a ~10.6:1 cr, not 11:1.



This is just to be a street car. I have both a 1.4mm and 1.1 wide fire head gasket available. What to do??????????

[/quote]



If it was my car i would go for the 1.4mm on an sc car , when no sc installed i would go for the 1.1mm .

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[DaveN]

I like this solution. Sell me the stock WideFire at a loss <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" /> and use the 1.4 because I don't need that one. Problem solved. <img src="/forum/images/smilies/968/laugh.png" class="smilie" alt="" />

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[Lear35A]

I'll get back to you on that. <img src="/forum/images/smilies/968/glare.gif" class="smilie" alt="" />

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[Eric_Oz_S2]

Lance



Obviously 1.4mm will be "safer", but there is nothing to stop an 11:1 CR motor with 5 psi boost running safely if it is correctly fuelled and tuned.



On my S2 I am running AFRs around 11 to 11.5:1 at full boost/<acronym title='wide open throttle'>WOT</acronym> along with retarded ignition (from stock). I also run 98 RON fuel, I think that is something like your 93 there. Your 91 is just not good enough, so hopefully you aren't using this.



I believe the later stage 3 (?) kits address the AFR issues (I think they were a little lean on the Stage 1?), so perhaps talk to Flash about upgrading your kit.





Tama



There is a "simple" way to count engine knocks, and it involves connecting a digital counting device to the knock yes/no pin of the diagnostic port - this is what I have done. It become really evident when knocking occurs as the numbers rapidly increase.

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[tamathumper]

Hmm, so somebody really concerned about detonation could hook an Arduino to that same port and light an LED or sound a buzzer (etc) if the knock count exceeded a certain number in a given span of time...

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[Eric_Oz_S2]

The counters normally used are the curtis ones. If you search the 'other' forum ® you will find good info. I used a Redlion one using a transistor as the switch between the DME signal and counter. It was very useful during tuning. You could hook an LED if you liked, but they would be a little tricky as you would need a peak hold circuit to maintain the +5v from the DME long enough to light the LED.



See this thread:



http://forums.pelicanparts.com/porsche-9...hread.html

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[tamathumper]

Muchos gracias. I'll give it a read. If it pans out, I've been meaning to get into Arduinos anyway, and I think this would be a good tinkering project.

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[flash]

lol - nothing to stop it but the rods

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[Lear35A]

Here my final calculation. I'll end up with a static CR of 10.67. I think that's close enough to what Porsche actually put out the door a couple of decades ago. Shouldn't be blowing head gaskets or bending rods, although time will tell.

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[DaveN]

Do I know how to start an OT thread or what! I ordered my Wide fire, thanks guys :-)

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