Redline in a modified B18?

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.

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.

They are the stage 3 turbo cams from crane.

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.

He didnt mention anythin about ls v-tec?


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

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.

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.

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.

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

Lower compression = higher boost

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.:smile:

Thanks for the help guys.

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

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

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.:smile:


thats not stock

Originally posted by CRXtc



thats not stock


Whats not stocK?? The bottom end is stock and the head is stock. The only thing he done to it was upgraded fuel.

Originally posted by 91civicDXdude
also just to add, you can run high compression with high boost but you also need high octane fuel (118 octane race fuel)


If its anything higher than 12 cr then yeh but anything lower then 12 is good on pump gas (93-94 octane)

Originally posted by redmanjd
lower compression the more turbo lag . high compression turbo is the best

Yep exactly!:smile:

Originally posted by mellowboy



Whats not stocK?? The bottom end is stock and the head is stock. The only thing he done to it was upgraded fuel.

and that whole turbo kit thing

Yeah, sure high c/r high boost is badass, but get real. First you gotta live on the East coast to get the 93+ octane. Second, you better have a standalone and some mad tuning skills to not get the D-E-T. And third, the engine is gonna be on the edge everytime you drive. Sure the import drag racers run insane amounts of boost with a C/R higher than factory, but the best gas, best parts, unbelievable amounts of tuning, and a whole 1320 feet at maximum throttle is a lot different than a street car.

Originally posted by 1320B4U
Yeah, sure high c/r high boost is badass, but get real. First you gotta live on the East coast to get the 93+ octane. Second, you better have a standalone and some mad tuning skills to not get the D-E-T. And third, the engine is gonna be on the edge everytime you drive. Sure the import drag racers run insane amounts of boost with a C/R higher than factory, but the best gas, best parts, unbelievable amounts of tuning, and a whole 1320 feet at maximum throttle is a lot different than a street car.


but a high compression motor will make more HP on lower boost levels then a motor with low compression higher boost

Originally posted by 1320B4U
Yeah, sure high c/r high boost is badass, but get real. First you gotta live on the East coast to get the 93+ octane.


WE get 93 and 94 here in Chicago buddy. AND OF COURSE ITS ALL ABOUT TUNING. IF i was into turbos i would choose high compression.

Originally posted by CRXtc


and that whole turbo kit thing



OK yeh but i'm sayin STOCK MOTOR meanin no work done to the internals.

AND OF COURSE ITS ALL ABOUT TUNING.

Second, you better have a standalone and some mad tuning skills to not get the D-E-T.

Ther is a guy in town running an crv-tec running 10 psi. with stock components. he ran 13.8 in the 1/4 last week.

"but a high compression motor will make more HP on lower boost levels then a motor with low compression higher boost"

Both motors have forged pistons:wink:

Okay, take a B18B with low CR (say 9.0:1) and 20psi.

Now take a B18B with 10.5:1 and what, about 8psi safely.

On a properly prepped 4 cyclinder engine(correct A/F ratio) each PSI of boost is generally good for 10-15 hp.

So that low C/R B18 is what? 140hp at a stock 9.0:1. Say the setup is good and you get 12hp per PSI. So 240HP for the 20psi of boost added to the 140 at the stock 'low' 9.0:1 and you get
roughly 380 flywheel horsepower.

The 10.5:1 C/R is gonna have what? about 180hp considering a 10.0:1 8100rpm B18C1 puts out 170hp. Say the setup is great and it gets 15hp per PSI. Which comes to 120hp plus the stock 180 and your at roughly 300 flywheel horsepower.

Thats a simple way to say it. There are many variables (turbo size and efficiency, intercooler capacity, efficiency and pressure drop, tuning, exhaust, cams, ect. ect.) but its fairly accurate.

Its what you want. The high psi motor will have gobs of top end power and mid range torque, spooled by 3000rpm. The low boost motor will be more responsive and might spool its turbo a tick quicker.

Originally posted by BigBearWest
Ther is a guy in town running an crv-tec running 10 psi. with stock components. he ran 13.8 in the 1/4 last week.

dude that is not saying much. if that is true right there i truely feel sad for that dude. a crvtec with only bolt ons should hit that time. now with a turbo you should be in the high 12's low 13's easy.

any amount of boost requires tuning skills.

Originally posted by 1320B4U
"but a high compression motor will make more HP on lower boost levels then a motor with low compression higher boost"

Both motors have forged pistons:wink:

Okay, take a B18B with low CR (say 9.0:1) and 20psi.

Now take a B18B with 10.5:1 and what, about 8psi safely.

On a properly prepped 4 cyclinder engine(correct A/F ratio) each PSI of boost is generally good for 10-15 hp.

So that low C/R B18 is what? 140hp at a stock 9.0:1. Say the setup is good and you get 12hp per PSI. So 240HP for the 20psi of boost added to the 140 at the stock 'low' 9.0:1 and you get
roughly 380 flywheel horsepower.

The 10.5:1 C/R is gonna have what? about 180hp considering a 10.0:1 8100rpm B18C1 puts out 170hp. Say the setup is great and it gets 15hp per PSI. Which comes to 120hp plus the stock 180 and your at roughly 300 flywheel horsepower.

Thats a simple way to say it. There are many variables (turbo size and efficiency, intercooler capacity, efficiency and pressure drop, tuning, exhaust, cams, ect. ect.) but its fairly accurate.

Its what you want. The high psi motor will have gobs of top end power and mid range torque, spooled by 3000rpm. The low boost motor will be more responsive and might spool its turbo a tick quicker.


when i say high compression i dont mean 10.5:1, thats LOW compression, i am talking 11.5:1 or even 12:1

Originally posted by Redline_civic91


dude that is not saying much. if that is true right there i truely feel sad for that dude. a crvtec with only bolt ons should hit that time. now with a turbo you should be in the high 12's low 13's easy.

At sea leval but we live in the rockies so say it is not a bad time