Redline in a modified B18?

[doug294]

Ok heres the question guys. If I have a B18 with low compression pisons, rods, stage 3 crane cams, turbo, etc, etc...how do I know when I redline? I mean it will totally change the factory redline.

[91civicDXdude]

just a thought, but stage 3 cams + turbo doesnt sound right unless stage 3 cams are the turbo profile.. and in that case, you want to dyno your car and look at the powergraph. more than likely, with the boost you're not going to need to rev that high anyways. The B18B's stroke is pretty long compared to a b16, and it revs to 8200, so i'd say that your engine would live revving to 7500 or so, but dont quote me, its just an estimate.

[doug294]

They are the stage 3 turbo cams from crane.

[1320B4U]

I've read not to take a built (forged internals) LS/VTEC past 7800rpm.
91civicDXdude is right about that stroke. The Rod to stroke ratio is not good. Its like 1.54:1. Perfect is considered 1.75:1. A B16 has a R/S ratio of 1.74:1. My Mitsu 4G63 R/S ratio is 1.70:1 I believe. A GSR B18C1 is 1.68:1 I think. The lower you go from 1.75 the more likely you are to throw a rod. Just dyno it with your current setup and see where the max HP is, if its a street car it will probably be 7000rpm at the most.

[mellowboy]

He didnt mention anythin about ls v-tec?


Anyways its gonna stay on stock rev limit unless u chipped the ecu.

[1320B4U]

I mention LS/VTEC because it uses a B18A or B18B bottom end. And that's what he is using in a turbo application. You can throw some lumpy cams, double valve springs and titanium retainers on any engine to help the high RPM, but some engines are flawed from the factory. No, not flawed-but not designed for high performance. Internal geometry of the engine has a lot to do with how it well perform. Even the old school Chevy 350 from the 60's to the present day LS6 has a rod/stroke ratio in the 1.70's. R/S ratio is vital, look it up.

[redmanjd]

i have a 8200 rev chip but i dont take it past 7200 cause you run the chance of valves floating. And by running high rpms you wear out the cylinder walls quicker cause of the rod stoke.

[doug294]

So can a use a B16 stroke kit to resolve it? Or is there an aftermarket solution? I'm trying to figure all this crap out. I got to rebuild a B18 to drop in my civic. Just trying to figure out if it would be better to buy all the parts for my A6(already have the money) or get the B18 and go from there.

[redmanjd]

if you put b16 rod and crank in a b18 you will have exrememly low compression cause the b18 stroke is longer im guessin the comp would be 7.5:1

[doug294]

Lower compression = higher boost

[mellowboy]

Just build up your ls motor. I would go all ls for turbo. A guy around here is running high 12s STOCK with upgraded fuel, clutch and light flywheel. Hes running around 12 lbs of boost. You build your head up to handle high rev. I'm pretty its ok to do so if you're keepin it all ls and no v-tec head. I also recommend that you build your bottom end and balance the crank and blueprint everything so that way it can handle high rev. Get it tuned and you are set. By the way lower cr does mean high boost but does NOT mean its always better. Alot of ppl thesed days are goin high cr turbo but on lower boost but just as fast.

[doug294]

Thanks for the help guys.

[91civicDXdude]

also just to add, you can run high compression with high boost but you also need high octane fuel (118 octane race fuel)

[redmanjd]

lower compression the more turbo lag . high compression turbo is the best

[CRXtc]

Originally posted by mellowboy
Just build up your ls motor. I would go all ls for turbo. A guy around here is running high 12s STOCK with upgraded fuel, clutch and light flywheel. Hes running around 12 lbs of boost. You build your head up to handle high rev. I'm pretty its ok to do so if you're keepin it all ls and no v-tec head. I also recommend that you build your bottom end and balance the crank and blueprint everything so that way it can handle high rev. Get it tuned and you are set. By the way lower cr does mean high boost but does NOT mean its always better. Alot of ppl thesed days are goin high cr turbo but on lower boost but just as fast.

thats not stock