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Old 04-05-2012, 01:08 PM   #1
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Compression ratio for supercharged cobra

What cr should I be running on my supercharged 1998 cobra to make the most out of my engine? What piston dish size do I need to get that cr? I plan on making around 650-700hp. I want to keep my stock bore. What else would I need to make around 15-18 psi safely? Other than the rods.
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Old 04-05-2012, 03:01 PM   #2
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Your looking at a fully forged lower end for sure, upgraded bolts, premium bearings, o rings and a little head work goes a long way with those heads. So valves too. Cams are a good idea too. A 9 compression ratio with those mods should get you very close at 18lbs what type of blower?
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Old 04-05-2012, 05:59 PM   #3
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Re: Compression ratio for supercharged cobra

What piston dish size should I get to get that compression? And a vortech centri. Yeah I've been wanting to do cams as well but they are a bit pricey. Lol
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Old 04-05-2012, 06:36 PM   #4
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Quote:
Originally Posted by vinnygt
What piston dish size should I get to get that compression? And a vortech centri. Yeah I've been wanting to do cams as well but they are a bit pricey. Lol
Mhmm. I would talk to a pro engine builder. I wouldn't recommend anything as far as poisons go because I don't know enough about it. The cams are pricey when you need 4 of them. Getting the vortech to that body level is gonna be expensive. f1a unit probably. the head work and cams will serve you well if you want to make big power.
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Old 04-05-2012, 07:32 PM   #5
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Re: Compression ratio for supercharged cobra

What piston dish size should I get to get that compression? And a vortech centri. Yeah I've been wanting to do cams as well but they are a bit pricey. Lol

---------- Post added at 07:32 PM ---------- Previous post was at 07:26 PM ----------

If I port my heads will I need to get new cams? Yeah I was planning on just taking it to a shop instead. Does 2k sound about right for forging out the bottom end including labor? I know a friend at a shop that will do all the labor for 350 I just need to take him the parts. No tuning or anything like that though. He'll just put it together for me.
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Old 04-05-2012, 07:46 PM   #6
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Quote:
Originally Posted by vinnygt
What piston dish size should I get to get that compression? And a vortech centri. Yeah I've been wanting to do cams as well but they are a bit pricey. Lol

---------- Post added at 07:32 PM ---------- Previous post was at 07:26 PM ----------

If I port my heads will I need to get new cams? Yeah I was planning on just taking it to a shop instead. Does 2k sound about right for forging out the bottom end including labor? I know a friend at a shop that will do all the labor for 350 I just need to take him the parts. No tuning or anything like that though. He'll just put it together for me.
that's stupid cheap, a forged bottom end I was looking at was 3100$ for my mach 1. 350 for a rebuild is a crazy good deal. I was planning on doing the build myself but a shop would cost 1200$ minimum for the build. Have you worked out your budget for this build? I would estimate you're looking at 13000$ for the forged engine, big blower, and the drive train needed to put the power down reliably. That doesn't even include suspension, brakes etc...
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Old 04-05-2012, 10:24 PM   #7
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Originally Posted by DaBluedude

that's stupid cheap, a forged bottom end I was looking at was 3100$ for my mach 1. 350 for a rebuild is a crazy good deal. I was planning on doing the build myself but a shop would cost 1200$ minimum for the build. Have you worked out your budget for this build? I would estimate you're looking at 13000$ for the forged engine, big blower, and the drive train needed to put the power down reliably. That doesn't even include suspension, brakes etc...
Yeah hes good mechanic but he just doesn't know much about performance engines but I'm sure if I give him enough info and all the proper parts he can build me a good setup. And I already have the blower set up but I'm only making around 420hp. I just want to forge out my internals to make it hold up to some more power. But with that I know my little t45 will give out so I already started looking for a t56. Ive never had a dyno tune or had work done at a performance shop so I don't know what prices I'm looking at in that aspect but with forged pistons and rods plus gaskets and all that extra stuff I'll need and labor I'm estimating around 2500 plus another tranny and all the stuff I'll need with that would probably add another 2k. I've already got a pretty good suspension set up. And I already have my cobra brakes so I think I'm pretty good with those. Maybe just some drilled roters.. But ive been looking around and the more I look the better the prices get. Specially with labor. 13k would be crazy lol Being that I only paid 12k for the car.

---------- Post added at 10:24 PM ---------- Previous post was at 10:22 PM ----------

Quote:
Originally Posted by DaBluedude

that's stupid cheap, a forged bottom end I was looking at was 3100$ for my mach 1. 350 for a rebuild is a crazy good deal. I was planning on doing the build myself but a shop would cost 1200$ minimum for the build. Have you worked out your budget for this build? I would estimate you're looking at 13000$ for the forged engine, big blower, and the drive train needed to put the power down reliably. That doesn't even include suspension, brakes etc...
Damn 3100. Was that with labor included?
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Old 04-06-2012, 12:25 AM   #8
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Originally Posted by vinnygt

Yeah hes good mechanic but he just doesn't know much about performance engines but I'm sure if I give him enough info and all the proper parts he can build me a good setup. And I already have the blower set up but I'm only making around 420hp. I just want to forge out my internals to make it hold up to some more power. But with that I know my little t45 will give out so I already started looking for a t56. Ive never had a dyno tune or had work done at a performance shop so I don't know what prices I'm looking at in that aspect but with forged pistons and rods plus gaskets and all that extra stuff I'll need and labor I'm estimating around 2500 plus another tranny and all the stuff I'll need with that would probably add another 2k. I've already got a pretty good suspension set up. And I already have my cobra brakes so I think I'm pretty good with those. Maybe just some drilled roters.. But ive been looking around and the more I look the better the prices get. Specially with labor. 13k would be crazy lol Being that I only paid 12k for the car.

---------- Post added at 10:24 PM ---------- Previous post was at 10:22 PM ----------



Damn 3100. Was that with labor included?
3100 is parts alone. Includes gaskets timing chain etc.

Your also going to need an upgraded fuel system, a better drive shaft, upgraded axel shafts etc... Etc... Etc. lol. . What is your current blower setup.
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Old 04-06-2012, 08:44 AM   #9
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Re: Compression ratio for supercharged cobra

the CR on a stock 03/04 cobra is 8.5:1~
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Old 04-06-2012, 03:17 PM   #10
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Originally Posted by DaBluedude

3100 is parts alone. Includes gaskets timing chain etc.

Your also going to need an upgraded fuel system, a better drive shaft, upgraded axel shafts etc... Etc... Etc. lol. . What is your current blower setup.
Yeah that's a lot of money. And yeah im having a bit of a problem with my fuel system. Im not sure what kind of fuel pump I have because it's an out of tank after market one but the stickers are all worn off on it. And also is there any way of know what kind of fuel injectors I have just by looking? I don't want to spend 400$ on something I already have. Lol. I keep getting a check engine light Everytime I remove my gas cap. I've changed it 2 times already and it keeps doing it. Not always though. The code says its lean on bank 1 and 2 so idk. And I have a vortech v2. The pulley is huge on it tho. So I'll need to get a smaller one. Also should I get the intercooler for it if I plan on making more psi?

---------- Post added at 03:17 PM ---------- Previous post was at 03:17 PM ----------

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Originally Posted by SpectorV
the CR on a stock 03/04 cobra is 8.5:1~
Would u recommend that for mine?
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Old 04-06-2012, 04:36 PM   #11
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Originally Posted by vinnygt

Yeah that's a lot of money. And yeah im having a bit of a problem with my fuel system. Im not sure what kind of fuel pump I have because it's an out of tank after market one but the stickers are all worn off on it. And also is there any way of know what kind of fuel injectors I have just by looking? I don't want to spend 400$ on something I already have. Lol. I keep getting a check engine light Everytime I remove my gas cap. I've changed it 2 times already and it keeps doing it. Not always though. The code says its lean on bank 1 and 2 so idk. And I have a vortech v2. The pulley is huge on it tho. So I'll need to get a smaller one. Also should I get the intercooler for it if I plan on making more psi?

---------- Post added at 03:17 PM ---------- Previous post was at 03:17 PM ----------



Would u recommend that for mine?
8.5 is consecutive for a mean build. I would go 8.9-9.4 . Something in that range. Your vortech v2 won't support that much boost. You will have to upgrade to a new unit. You will definitely need the intercooler. I'm more concerned about your lean codes. That could be a serious issue and you should have it looked into. In general, injectors are usually color coded to their size. if I were you, I would scrap your plans to go huge hp, add an intercooler to your current setup, fix your fuel issues and get that lean code fixed. Then get custom dyno tuned with a smaller pulley. The build you want to do is very involved. You will see nice gains from the intercooled setup too. Maybe as much as 50hp with a better maf and tune. Choler air is important. I would definitely get it into someone who can help you better in person to get the car tuning well. Nothing wrong with a 480rwhp car.
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Old 04-06-2012, 05:44 PM   #12
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Originally Posted by DaBluedude

8.5 is consecutive for a mean build. I would go 8.9-9.4 . Something in that range. Your vortech v2 won't support that much boost. You will have to upgrade to a new unit. You will definitely need the intercooler. I'm more concerned about your lean codes. That could be a serious issue and you should have it looked into. In general, injectors are usually color coded to their size. if I were you, I would scrap your plans to go huge hp, add an intercooler to your current setup, fix your fuel issues and get that lean code fixed. Then get custom dyno tuned with a smaller pulley. The build you want to do is very involved. You will see nice gains from the intercooled setup too. Maybe as much as 50hp with a better maf and tune. Choler air is important. I would definitely get it into someone who can help you better in person to get the car tuning well. Nothing wrong with a 480rwhp car.
Awesome man thank u. And your right. With the right tuning I guess I don't need that much power. But will my stock pistons and rods hold up to that? And yeah I would really appreciate it if u could help me out with that because I really have no clue in tuning. Finally someone who could really help me out and give me some advice. Lol. I've posted like 3 different times and nothing. Lol. Basically did as much research as I could. But yeah..I'd much rather have a 480hp car that runs smooth than a 700hp one that has a bunch of issues.
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Old 04-07-2012, 01:59 AM   #13
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Originally Posted by vinnygt

Awesome man thank u. And your right. With the right tuning I guess I don't need that much power. But will my stock pistons and rods hold up to that? And yeah I would really appreciate it if u could help me out with that because I really have no clue in tuning. Finally someone who could really help me out and give me some advice. Lol. I've posted like 3 different times and nothing. LolI . Basically did as much research as I could. But yeah..I'd much rather have a 480hp car that runs smooth than a 700hp one that has a bunch of issues.
You should be ok but definitely intercool and get a safe tune. I would really recommend doing the bottom end before you go too crazy. You will also have to find someone to write you a custom dyno tune
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Old 04-08-2012, 11:47 PM   #14
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Originally Posted by DaBluedude

You should be ok but definitely intercool and get a safe tune. I would really recommend doing the bottom end before you go too crazy. You will also have to find someone to write you a custom dyno tune
So definitely get the intercooler and forged and then get a good tune?
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Old 04-09-2012, 01:21 AM   #15
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So definitely get the intercooler and forged and then get a good tune?
That's what I would do.
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Old 04-17-2012, 01:50 PM   #16
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Originally Posted by DaBluedude

You should be ok but definitely intercool and get a safe tune. I would really recommend doing the bottom end before you go too crazy. You will also have to find someone to write you a custom dyno tune
What exactly is considered a "safe" tune in terms of what would constitute a safe tune i dont mean specific numbers? If this doesnt make sense i can re word my question. I just hear safe tune all the time and i dont really understand what thats in regard to. Forgive my inexperience to the lingo.
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Old 04-17-2012, 02:58 PM   #17
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What exactly is considered a "safe" tune in terms of what would constitute a safe tune i dont mean specific numbers? If this doesnt make sense i can re word my question. I just hear safe tune all the time and i dont really understand what thats in regard to. Forgive my inexperience to the lingo.
A "safe" tune would be tuning the car within the rated fwhp #'s before its breaking point
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Old 04-17-2012, 03:10 PM   #18
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A "safe" tune would be tuning the car within the rated fwhp #'s before its breaking point
Exactly
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Old 04-17-2012, 03:17 PM   #19
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Tuning to factory specs seems to be a waste of time. If i did read your post correct?
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Old 04-17-2012, 03:17 PM   #20
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Ok so I keep looking every where to find the pistons that will keep my compression as close as stock but none say it will keep me at 9:85:1. I have b heads right ? With 52cc combustion chambers? Where can I get these pistons? I checked on lethal performance and also on je. The closest ratio I can get to is 10:3. Is that too high?
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Old 04-17-2012, 04:05 PM   #21
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Originally Posted by vinnygt
Ok so I keep looking every where to find the pistons that will keep my compression as close as stock but none say it will keep me at 9:85:1. I have b heads right ? With 52cc combustion chambers? Where can I get these pistons? I checked on lethal performance and also on je. The closest ratio I can get to is 10:3. Is that too high?
Check out dss racing they will have no problem taking care of you're needs all you have to do is give them a call let them know what you want and bam! Done! They do custom pistons with custom compression ratios .
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Old 04-17-2012, 05:08 PM   #22
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Check out dss racing they will have no problem taking care of you're needs all you have to do is give them a call let them know what you want and bam! Done! They do custom pistons with custom compression ratios .
Nice I had no clue. Thank u bro. Stock compression should work fine right?
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Old 04-17-2012, 05:54 PM   #23
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Nice I had no clue. Thank u bro. Stock compression should work fine right?
Ya if you're supercharging I would use stock compression maybe a bit lower depending on the amount of boost you want to run
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Old 04-17-2012, 06:30 PM   #24
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Ya if you're supercharging I would use stock compression maybe a bit lower depending on the amount of boost you want to run
Yeah sc. Maybe around 15-18 pounds. Will the smaller pulley get me boost sooner? Cuz with my current set up I get around 9psi but way up at around 7k rpms. If I'm pushing more boost will I also get it sooner?
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Old 04-17-2012, 07:57 PM   #25
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Originally Posted by vinnygt

Yeah sc. Maybe around 15-18 pounds. Will the smaller pulley get me boost sooner? Cuz with my current set up I get around 9psi but way up at around 7k rpms. If I'm pushing more boost will I also get it sooner?
I know the smaller pulley will give you more boost but I don't think it will give you boost sooner , and max boost at 7k seems a bit high I would think you would be hitting 9psi at 5200-5500 rpm
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Old 04-17-2012, 08:37 PM   #26
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I know the smaller pulley will give you more boost but I don't think it will give you boost sooner , and max boost at 7k seems a bit high I would think you would be hitting 9psi at 5200-5500 rpm
That's what I'm thinking. It kind of bugs me that I have to shift really late in order to feel the boost
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