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 Post subject: Cold intake air
 Post Posted: Mon Jul 02, 2012 8:50 am 
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Took this quote from speedtalk. Not trying to be sarcastic. I was only wondering, is there any truth to this. Will cold air help or change the octane level?



Re: too much compression 383 SBC Help

Postby Matt Gruber ยป Mon Jul 02, 2012 5:03 am

like FBIRD said
cold inlet air is better
worth 4 octane points
my 87 cold inlet jumps to 91 with underhood air.
87 w/hot underhood air is ping city on a hot day


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 Post subject: Re: Cold intake air
 Post Posted: Mon Jul 02, 2012 9:40 am 
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May be wrong but think hot air and hot weather will build more of a "ping" issue than a cool charge but I don't see it building more obtain.

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 Post subject: Re: Cold intake air
 Post Posted: Mon Jul 02, 2012 10:44 am 
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Not sure about actually changing the octaine in the fuel but cooler air will mean cooler compressed air which will lessen the chance of detonation. That's the reason most guys that run turbos also run intercoolers!

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 Post subject: Re: Cold intake air
 Post Posted: Mon Jul 02, 2012 11:46 am 
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I'm not really sure what is meant here but cold air is denser so it carries more oxygen and would make the mixture leaner. I thought that's why when the air got cool you would step up the jets for better performance. I always thought when you got an engine too lean it would ping so the warmer inlet air should be less likely to ping than cooler outside air. I can't see how changing the air temp affects the octane unless he is referring to the octane required?

Of course I could be all wrong....

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 Post subject: Re: Cold intake air
 Post Posted: Mon Jul 02, 2012 2:37 pm 
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They are trying to dance around the compression being to high for street gas. I have never heard of cold air doing anything to octane, I guess I was wondering if turbos acutally changed the octane requirements with a cooler denser charge. I remember trying octane boosters when I had an engine that was too high and they never worked. Then later on I read that the 2 to 3 points were acually 3 tenths of a point. I tried different distributors, springs wieghts, the only thing that would work was higher octane and finally more chamber volume. Oldsmobile has very little selection for Heads. I now have the 77cc Edelbrocks and the aluminum just does not detonate very easy. I was able to raise my initial timing a huge amount, compared to before. The best octane we have here is 91. I guess if one had access to E-85 then they could re-jet or have a carb purpose built and use a lot higher compression engine on the street.


Just primer.


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 Post subject: Re: Cold intake air
 Post Posted: Mon Jul 02, 2012 2:53 pm 
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There are guys with compression up over 15 to 1 that are running E85 now and doing nothing special except for a modified carburetor to do it!

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 Post subject: Re: Cold intake air
 Post Posted: Mon Jul 02, 2012 7:53 pm 
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I know. I wish I had access to it. I am from the Midwest. Both my mother and father were the second and third generation of Iowa farmers. Before the Corporate farming took over. I miss the firefly's at night and the endless fishing ponds full of Bass and bluegill. The wild mulberry tree's. It is very humid though. Would love to install flat pistons and run a real high compression engine on the street.

Just Primer


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