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Deciding a compression ratio.; How much needs to be taken off?
Topic Started: Sep 8 2011, 06:38 PM (1,816 Views)
Bigshane90


Alright I've got an 8valve 1.3 that I'm ordering a 260 torque grind cam for from delta cams "thanks to you guys for finding that for me"
I also will be doing a port and polish on my head.
The problem I'm having is that that I'm not sure what compression ratio to go with, how much is too much? Whith this cam when does this turn into an interference motor? Because I'd rather keep from that if I can.
Also I need to know how much needs to be removed from the head because the machine shops around here most likely won't know material removed=what compression ratio.
Thank you guys for all the help!
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dayle1960
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Fastest Hampster EVER

Aw, heck, Bigshane. Just tell your engine guys to shave 1/4" off the head. Get that compression up to 100:1 and put that delta cam to the test. :D Maybe even throw in a turbo setup to get off the line even quicker. Nitrous would be boss also. ;)

Wish I could really answer your question, but that's way over my feable shadetree abilities. But just wait and someone will gladly answer. Sit back and have some :beer .
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starscream5000
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Got 70 MPG?

I'm no expert either, but 3Tech shaved off .040" on my eco head. He also states that you can take .100" off the G10 and it would still be non-interference, but this is no G10. I do suspect that Suzuki didn't design them very differently though.
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Bigshane90


Yea I figgured 3tech would know I was just wondering if he would chime in or if it's a top secret kinda thing "haha"
.100 is a jump. I think normal is .040-.060 to raise compression, correct me if I'm wrong of course.
I can't wait to see what this g13 will do with this combo. I'd love to see a 20-30 horse gain
If all goes well I might do a 5speed swap for more improvement
Edited by Bigshane90, Sep 8 2011, 10:06 PM.
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starscream5000
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Got 70 MPG?

You wouldn't see those power gains without some type of forced induction.

Sorry :(
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Bigshane90


Not even 20? I would think the higher comp. Ratio would give at least 10-15
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Scoobs
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:D

Wouldnt be much, i notice a significant difference in performance on my 75 mm bore G10 than i do the stock one in my red geo. But thats fresh build, compared to 100k mile motor. With a weak transmission
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starscream5000
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Got 70 MPG?

Bigshane90
Sep 8 2011, 10:17 PM
Not even 20? I would think the higher comp. Ratio would give at least 10-15
You're expecting a 28%--42% incrase in power just from a cam, that's not going to happen.

A mild turbo setup would get you a 25% increase in power.

Dump a ton of money into a lot of head work, P&P, vales, crazy ass cam, injectors and fuel pump, along with a turbo and laughing gas and you may see a 30%--45% (depending on boost and jet size),increase in power as long as your bottom end and clutch do not give out.
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Coche Blanco
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Troll Certified

I believe the 95 had around 78hp new.

13% jump (10hp) is possible with a cam/compression change, imho.
Edited by Coche Blanco, Sep 8 2011, 11:38 PM.
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Murf 59
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If you are gonna drive this thing on the street and live with it day to day. Only go to about 10.5 to 1. Much higher than that and you will start having problems with knocking and pinging. If your racing it go higher.
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starscream5000
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Got 70 MPG?

Coche Blanco
Sep 8 2011, 11:37 PM
I believe the 95 had around 78hp new.

13% jump (10hp) is possible with a cam/compression change, imho.
I based mine off of 70 HP as that's what I thought all G13BAs had.

I also thought that the G13BB had 80 HP... I could be wrong though.
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91 ragtop
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It was my understanding that the G13BA was 67 hp and the G13BB was 79 hp. If you're thinking a cam and compression bump is going to gve you 30 horses you're dreamin.


Ken.......
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Coche Blanco
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You are right 91, I got my years/numbers mixed up.
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starscream5000
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Got 70 MPG?

Damn, then even my answer was an optimistic one :lol
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Bigshane90


A cam, port and polish,compression bump. I already have cai and exhaust.
You guys are dream destroyers! Lol
Just messin. That really stinks if you think about it that way. It would be like a 15% increase in power Wich is like 9-10hp...
Maybe I was being optimistic it just seems every little thing I do I can feel it in the seat of the pants.
I guess you can feel every little bit because the metros are lighter and have less power. So it's the same percentage increase as you would see on a larger car.
Just feels more powerful because of the power to weight ratio.

So what's the deal guys is it worth it? I want a fun geo that surprises people when I press the go pedal. I'm really into that wow factor
Edited by Bigshane90, Sep 9 2011, 01:30 AM.
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