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Discussion Starter #1
I understand running richer under boost to cool the charge and prevent detonation but what does varying the timing do? Does anyone have a good explanation?


dave
 

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Discussion Starter #3
thanks Dave. I imagine you also lose a fair degree of torque as a result too. Does increasing the octane allow you more advance?

dave
 

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Does increasing the octane allow you more advance?
Yes up to a certain point. That is why guys who run race gas while getting their car tuned with a blower end up having problems when they put in regular pump gas. Higher octane=higher timing allowed in most cases.

For every degree of timing on a *blown* car you see around 6-10 RWHP is what I have noticed on most cars.
 

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Discussion Starter #5
So, if i get tuned on 104, then i should pull several degrees of timing on the MSD if i intend on running 94 octane on the street? Or maybe get an entirely different chip burned for 94.

Right now with the JT trim installed and 42#s, I've set the MSD to pull 10 degrees of timing starting at 4000rpm. On the street, I'm running around 97 octane and shifting at around 4000rpm to 'keep it safe'. I've only seen 5# boost. I'm afraid to push it any higher until I'm re-tuned.

dave
 

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Where do you find 97 Octane for the Street?? The Highest I have seen at Gas Stations around here is 93 Octane. The cheap ones only sell 91 or 92 Octane.
Are you using an Octane Booster or is there a Gas Station that sells 97 Octane Gas??
 

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it just keeps the cyl pressure's in check.

with a power adder the mix tends to burn faster and their is more in it so you need to start the burn a bit later to keep the flame front from slaming into the piston on it way up on the compression stroke(which is what detonation is most of the time can also be casued by hot spots but basicly does the same thing.).
 

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Discussion Starter #8
Thanks SKYWLKR! That's what i was wondering.

Sting, we have 100 octane here at one of the gas stations for $3.99 per gallon (lucky,lucky, lucky!). I just mix 1/2 tanks or 100 and 94 and estimate it as 97. I will occasionally mix 93 with Torco Fuel Additive to make 104 octane.

Dave
 

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Soapbox time. Get it tuned for 93 octane. If you just have to have the extra HP get a flip chip for race gas, and have that tuned too. Trying to get that last little bit of HP out of an engine is usually when things go BOOM.
 

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Discussion Starter #10
Dave, my original tune with SHM was on 104. I would love to make good HP with 93 octane but i was under the impression that you couldn't go much over 500rwhp(if even that) with 93 and on a GT. If so, then maybe two chips! There's so many tuners down where you are. I really wished i were in Georgia (or Virginia)! :)

dave

P.S. What does a good tune cost per hour? I recently heard someone is charging $1000 per hour!!! Must be God...
 

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rammer said:
I've set the MSD to pull 10 degrees of timing starting at 4000rpm.
All thats doing is killing a ton of power up top. You need to pull the most timing at the point of highest cylinder pressure, which is your torque peak. Continuing to pull timing above that simply kills power, which is why BTMs suck ass and are no more than a bandaid solution. You should even be able to put a degree or two back in up top.
 

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Discussion Starter #12
What are BTMs? I went back to 5 degrees starting at 4 grand. Anyway, that's where i start heading to peak torque territory. Torque is a flat 450ft-lbs from 4500-6000. I can't wait to get this thing tuned! Gonna cost me $$s.

D
 
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