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 Post subject: C/R Question
PostPosted: Fri Aug 23, 2013 5:47 am 
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Location: Lancaster PA
I just bought a buggy with a 1915 in it. It has all scat internals c35 cam and 044 big valve heads. Also has a type 3 turbo off a sabb on it. With a weber side draft carb. Is there a way I can find the compression ratio without tearing the engine apart? Also he said to run nothing but 108 octane in it. He says its around 7.5/1 C/R. Seems low to me but im new to turbo engins. The thing hauls a** :mrgreen: Im just not sure it needs to have 108 octane in it. I read that you can run 93 octane up to like 9.5/1. Thanks for the help

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 Post subject: Re: C/R Question
PostPosted: Fri Aug 23, 2013 6:37 am 
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When you add boost the ratio goes up, here is a calculator to figure out what compression ratio your at at a give PSI of boost. http://www.rbracing-rsr.com/compression.htm


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 Post subject: Re: C/R Question
PostPosted: Fri Aug 23, 2013 7:42 am 
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I plan on adding some boost to my engine in the future. At 12.5:1 C/R I will have to use a thicker head gasket to lower C/R to avoid certain meltdown!


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 Post subject: Re: C/R Question
PostPosted: Fri Aug 23, 2013 9:28 am 
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Also. It has like no power untill it spools up. Kind of like a big dead spot. Is that normal on a turbo engine?


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 Post subject: Re: C/R Question
PostPosted: Fri Aug 23, 2013 11:58 am 
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Yea it's called turbo lag, the bigger the turbo the worse it is.
Your about 11.5:1 if your running around 8psi


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Last edited by Psycho Alpha on Fri Aug 23, 2013 7:01 pm, edited 1 time in total.

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 Post subject: Re: C/R Question
PostPosted: Fri Aug 23, 2013 6:05 pm 
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Ok thanks. I ran it around for a while today and it did get better or I got used to it lol. Either way I love it. Thanks for all the feedback. I wish I could make the Bella ride tomorrow :(


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 Post subject: Re: C/R Question
PostPosted: Fri Aug 23, 2013 10:25 pm 
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U can pull a spark plug out and measure the fall with an old weding rod to give you a rough idea.


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 Post subject: Re: C/R Question
PostPosted: Sat Aug 24, 2013 6:44 am 
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Never thought of that. Thanks


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 Post subject: Re: C/R Question
PostPosted: Sat Aug 24, 2013 9:32 am 
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The only way to really know the C/R is to pull a head and measure everything. You could get away with 8:1 on a turbo motor running pump gas,as long as the boost was kept low and the timing should be around 24 degrees total.


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 Post subject: Re: C/R Question
PostPosted: Mon Aug 26, 2013 1:16 am 
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It has a 009 dist. with electronic ignition. I just adjust the advance stop to max out at 24* advance?

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 Post subject: Re: C/R Question
PostPosted: Mon Aug 26, 2013 6:00 am 
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Or do I lock it at 25*? Wouldn't that make it run bad at idle if the timing was always at 25*?


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 Post subject: Re: C/R Question
PostPosted: Mon Aug 26, 2013 2:15 pm 
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Ripinitup wrote:
Or do I lock it at 25*? Wouldn't that make it run bad at idle if the timing was always at 25*?


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22*-24* I like to weld the advance to lock it...the prob is starting with that much timing so u may b closer to 22* it will idle and come off idle fine.


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 Post subject: Re: C/R Question
PostPosted: Mon Aug 26, 2013 4:45 pm 
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Where do I weld it? Under the cap? And how will I know how much advance Im at? Sorry for all the questions. Ive never done this before and I want to get it rite. Thanks :mrgreen:

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 Post subject: Re: C/R Question
PostPosted: Tue Aug 27, 2013 10:04 am 
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Remove the dizzy take the igniter out and the plate under it. If u hold the bottom of the shaft and top you can see how the advance works by twisting the top while holding the bottom. You need to lock the 2 shafts as 1. Adjust timing with a light after its locked.


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 Post subject: Re: C/R Question
PostPosted: Tue Aug 27, 2013 3:39 pm 
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Ok. Thanks


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