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Discussion Starter #1
Im building a D15B with z6 head need a CR that will run on low octane gas. If need be using an Octane booster. Its for a enduro car and I want to spend only $75-$100 in gas a weekend instead of $150-$200 ontop of the $900 entry fees and lodging food travel ect.... Total bill is about $2000-$2500 per race Not cheap...

Whats the highest CR I can get away with on like 86-87 Octane. Not looking to make huge power just a minor bump without detonation.

Recommended Pistons for D15 with a z6 Using D15B7 Rods.

I do not know if these are correct Numbers
CR calc on line says:
Head Gasket is .027" thick:

D15B7 PM3 piston = 10.49:1 ??? Really ???
D16A6 PM6 piston = 9.02:1
ZC P29/PM7 piston = 10.78:1
D16A1 PG6 piston = 10.46:1


I got plenty of options.
If I bump to a .051" head gasket I can drop CR 0.64:1
If I bump to a .045" head gasket I can drop CR 0.49:1
If I bump to a .040" head gasket I can drop CR 0.36:1
If I bump to a .036" head gasket I can drop CR 0.25:1
If I bump to a .030" head gasket I can drop CR 0.08:1

I do my research before asking a question at least...
 

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If you're spending 2500 per race, why cheap out on fuel that will help you win? It doesn't make sense! Spend the extra 25-50 bucks on fuel and bump up your compression even more for the same price in parts and work.
24 hours of lemons $500 car race... More chance of something breaking on the car like suspension and crap. The objective is to say on the track
You asked
 

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here's the thing...the higher the compression the higher the octane needs to be OR the more timing that will need to be removed (granted this is limited, aka you can remove only so much before you start loosing too much power and gain nothing)...for your setup it will be a delicate balance that might take trial and error until you find the harmony you are looking for.

since you are looking at endurance racing here, i would recommend staying right at or under 10:1 to start with, you can always do slight raises as you go along (again the trial and error bit)...what are your limitations in the class you are running engine modification wise?
 

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Discussion Starter #7
The limitations is to have $500 total in the car not including safety items. I bought a z6 head IM header Dizzy for $60 and putting it on a D15B7 block. I have enough in my limit for a set of pistons and rings to stay under $500.

Other concern is wrist pin width and the pistons listed will the B7 wrist pin fit all listed pistons above
 

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24 hours of lemons $500 car race... More chance of something breaking on the car like suspension and crap. The objective is to say on the track
You asked
I see. That makes sense! I didn't realize it was endurance racing. I would say 10:1 should be ok. It's just a matter of tuning it for low octane. Like was already said though, You can only go so far with it before detonation and you won't be able to get the full potential out of it.
 

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if i were you i would go for a good solid mini me setup, given that the low end is in good shape, i would keep it the way it is now, put the z6 head on it with a three layer gasket (to lower the compression just a tad)...then put a good stage 2 cam in and tune the crap out of it with a good intake and exhuast system...this should give you a decent boost for about 500 :yes:
 

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Discussion Starter #10
if i were you i would go for a good solid mini me setup, given that the low end is in good shape, i would keep it the way it is now, put the z6 head on it with a three layer gasket (to lower the compression just a tad)...then put a good stage 2 cam in and tune the crap out of it with a good intake and exhuast system...this should give you a decent boost for about 500 :yes:
I think I am going with a .051" Cometic 3 Layer gasket on B7 pistons cause I have a B7 block it will be 10:1 CR.

I looked into klotz octane booster but the cost is more than running 93 octane all day long.
As for the cam too much money because I have to stay under $500 for the car I am at $250 at the moment. Lucky I picked up a Z6 transmission for $50 they guy thought it was a DX. D15B JDM non vtec block for $50 with low mileage and the z6 top end for $60 + harness parts and some axles.
 

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10:1 with 87 octane will be fine, i ran it like that on my old mini-me for a long time with no issues.
 

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LEMONS?! Yesss, I will probably be there this coming race to watch maybe. We'll see ;] Our race team at Penn State was thinking about building a car but we couldn't decide on what. I was looking for a wrecked but straight driving RWD car with some decent handling but couldn't find anything.
 

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Discussion Starter #17
LEMONS?! Yesss, I will probably be there this coming race to watch maybe. We'll see ;] Our race team at Penn State was thinking about building a car but we couldn't decide on what. I was looking for a wrecked but straight driving RWD car with some decent handling but couldn't find anything.
Schedule:
Events & Results

We are looking at
April 16-17: GingerMan Raceway, South Haven MI
OR
April 9-10: New Jersey Motorsports Park, Millville NJ

June 18-19: Summit Point Raceway, Summit Point WV

July 16-17: GingerMan Raceway, South Haven MI

August 27-28: Mid-America Motorplex, Pacific Junction IA

October 8-9: Autobahn Country Club, Joliet IL
OR
Chumpcar:
ChumpCar World Series - Events
8-9 October 2011
Nelson Ledges Road Course (Garrettsville, OH)
The Longer Longest Day - 25:25:25
 
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