-iLLuZioN-B18C1

"we installed oversized JDM ITR dome pistons good for almost 20 hp"

they put this in a 94 gsr block, is this statement true. also, this raises my
compression ratio doesnt it????

JiggyKooAndy

20 hp maybe at the crank. not to the wheels...but yes, they probably can.

-iLLuZioN-B18C1

what i really want to know is will this raise my compression b/c im planning on turbo and if it raises that SUCKSSSSS!!!!!!!!!!!!!!!!!

NickGSR

Yes it will raise your compressions!
USDM GSR is 10:1
I think that jdm itr is around 11.3:1
Don't quote me on that.... I know for sure that its higher than the gsr's though.

JiggyKooAndy

TURBOCHARGERS & COMPRESSION: THE MYTH!!!
There has been a long-standing myth with turbocharged Honda cars. For as long as I can remember, people have been quite concerned about having too high of a compression ratio, on their turbocharged Honda. The myth is: the lower the compression...the better. Well, this is not entirely true.

Why is a low compression motor good to turbocharge?

In essence, a low compression motor is good to turbocharge, because it is just easier to do so...and not worry about it. But is that what we really want to do as enthusiasts? Do we want to just slap a turbocharger on a car, and call it a day? Absolutely not. With turbocharging, comes the responsibility of tuning and care. If you are just going to turbocharge your car, and call it a day, then frankly, you don't deserve the luxery of boost! As well, might I add...that simply because it is easy to slap a turbocharger on a low compression motor and not worry about it, does not mean that it is right. I can guarantee you, that if you turbocharge a low compression motor, and fail to tune it correctly, you will end up on the side of the road, with blue smoke coming from your exhaust pipe.

Generally, a lower compression motor affords you more margin of error, when tuning. A slightly imperfect a:f ratio probably won't lead to the demise of your motor...unless you drive like a total jerk.

Why should I consider a higher compression motor, while making my decision of what motor will suit my needs?

Different from a low compression motor, a higher compression motor will not give you a large margin of error, when tuning. As stated before, if you expect to slap on a turbocharger, and call it a day, well then stay away from the higher compression motors all together. A higher compression motor demands slightly more TLC than a lower compression motor. But oh, the rewards are plenty.

Bottom line...a higher compression motor, pound for pound, will make more power, than a low compression motor. This works along the same lines as naturally aspirated Honda motors. You never see an NA enthusiasts spouting off about low compression do you? No, one of the keys to NA performance is high compression. So, why should it be any differnt for turbocharged applications? Of course, the routes to high compression are different (NA uses lightweight rods and pistons, that a turbocharged application would simply tear to shreds), but the end goal is the same.

Let's make an observation here. I am going to throw a scenerio for you...

Car A:
B18B (stock 9.2:1 CR)
Rev Hard Stage II
Thermal 3" exhaust
MSD 6AL
MSD Pro Cap
MSD Blaster 3 Coil
Holley 255lph in-tank fuel pump
AEM fuel rail
RC440cc injectors
A'pex S-AFC

Car B:
B18B (JE pistons, 10.5:1 CR)
Rev Hard Stage II
Thermal 3" exhaust
MSD 6AL
MSD Pro Cap
MSD Blaster 3 Coil
Holley 255lph in-tank fuel pump
AEM fuel rail
RC440cc injectors
A'pex S-AFC

Now for the sake of argument, let's say that both cars are well tuned, by the same tuner, both have an identical weight, both have the same slicks, both are boosting 1.0bar, and both are being driven by the same guy...at the same time (yeah, yeah, yeah...just roll with me here)! Now, which one do you think is going to come across the finish line first? Mythological thinking says that the guy with the low compression is best suited to win...right? Wrong. The guy with the 10.5:1 compression ratio is going to smoke the guy with the low compression.

Another point I would like to bring up is the misuse of the term "high compression" when it comes to Honda motors, and turbocharging them. In all honesty...10.6:1, 11.0:1, etc...aren't even really that high. Most NA monsters utilize 12.5:1 or higher...and some even as high as 14.0:1, in cases of extreme race. If you do some snooping around, you will realize that most of the really fast Hondas, and I'm talking sub-10 second monsters, utilize high compression setups, to achieve enourmous horsepower goals. Most of these guys won't openly discuss it though, so you are likely to come across terms such as "undisclosed compression", or something along that line. As I stated before, the myth is that low compression is key...so these guys want to stay on top, and the way to do it is hide the fact that they are using high compression, turbocharged motors...to propel themselves into sub-10's.

Reliability, and compression...

This is a regular question that pops up, and is quite valid. Frankly, as soon as you modify a Honda at all...reliability becomes an issue. A lot of us can testify that the proverbial "can of worms" sprung open as soon as we made our first modification. Many times, Honda enthusiasts will spout off the reliability factor, in Import vs. Domestic wars, when in actuality, they fail to realize that we are in just as much danger as those old pushrod V8's are, as soon as we modify our Honda engines.

Now, what is the solution? I have been saying it for a long time, as have several others such as Tuan, neouser, texan, and st00pid...TUNING IS KEY! That's the bottom line.

A well tuned higher compression motor will last just as long as any low compression motor. Tuning is not a factor that can afford to be sacraficed. You will not survive with an untuned higher compression motor, just as you will not survive with an untuned low compression motor.

So, with all of that said, it basically boils down to your own personal choice. Do not fear the B16A, the B18C1, or the H22A...etc. If you have the monitary requirement to turbocharge a higher compression VTEC motor, I would say, do not hesitate to do so.

As i saw in a someones signature the other day...
You can have either Cheap, Reliable, or Fast

Cheap and Fast can't be Reliable

Fast and Reliable can't be Cheap

Cheap and Reliable can't be Fast

Tuning is not necessarily cheap when you have to do it every month on a turboed honda, but the above statement says it all.

J-i-g-g-y

baonest

jiggy: well ill be damned.. thats some interesting info. gonna have to look into that. im runnin 11.5 for NA. ive been a bit curious also about high compression turbo, i would like to see a real dyno of the cars u used in your example and see the real difference.

JiggyKooAndy

yes, wish i had the money to perform such a project.

1158

I agree completely with this. I'm going to turbo my stock GSR (10.0:1). With PROPER tuning it can be done and done reliably. As I said, I agree 100% just don't let some of those guys in the FI area see this.

RedTeg95

Amen to all of that. This is something I've tried to tell people before but there is this belief that if you boost you need to have low compression.

But Jiggy you should give credit to Hondalife for the info since that is where the artical is from.

http://www.hondalife.com/articles/tu...ompression.htm

There is also another artical on the site that has a more techinical explination of the subject...

http://www.hondalife.com/effectivecompression.htm


[Modified by RedTeg95, 2:57 PM 8/28/2002]

jeebusm3

nice reply

SIK IN DA HED

true... but i still think a motor with lower compression is best suited for turbo. sure.. you get more horsepower from a higher compression motor... but even at its tuned potential... you can boost more on a lower compression motor. the difference between the b18b and b18c1 (20 horsepower) does not even put a gap between the 2 motors. ill give you an example.

identical setups.
one with a b18b... the other with a b18c1
9.2:1 vs. 10:1 (no huge difference in compression)
lets say for example... 13max psi on b18b and 10max psi on b18c1
3 psi of boost will more than compensate for the extra hp you get from higher compression. its been proven on the dyno.

theres always this "tuning" issue when it comes to a higher compression motor. have you ever thought about a tuned b18b? no one really does when they try to convince each other that higher compression is better. more power, depending on certain variables... yet, not better.

Comp97GSR

With all this talk about F/I on higher compression motors, it seems that there isn't alot of talk about the intake temps. In a nut shell, the cooler your intake air is the more boost you can run and it is much safer. When I can tell everybody more about a project that ATI is working on, I can show dyno graphs of the theories and myths of what we are all talking about. What I can say is a completely stock 00 Si put out 270 whp @ 11psi with stock 10.2 compression with intercooled intake air. Sure it could have even more boost (and probably will) but it is a womans car and reliability is a major factor in the setup.

JiggyKooAndy

i have actually heard of someone running dry ice between the filter and the tube, it makes the air much colder, and i could even tell the huge gain he got from doing it. i wonder if it ruins the engine though...

JiggyKooAndy

o_Rage_o

no one said that upping the compression does not give you power. The problem with a high compression turbo is definetly the reliability because of the MUCH smaller range margin of error for tuning, and the fact that you gotta be running some high octane (due to the compression), and be sure that the mixture is ALWAYS right.

Of course with more compression you will beat out a car with the same turbo and lower compression, high compression means more power any way you look at it period.

The reason why the myth exists is because with lower compression, its easier for one to tune, and leave room for errors / problems that arise and still have an overall high horsepower car, in fact, most people lower their compression so that they can boost safer, and more. Boost is more efficient and the loss of power by going to lower compression pays off in the tuning and reliability aspect.

-Rage

MikeSarr_GSR

most people tune with a VAFC and thier butt, slap on a cheap *** turbo kit
that they bought second hand and try to make that work. they actually think
a honda with 3K invested will make a good turboed car. the reality is, you need
to totally re-engineer the setup. I agree that you can boost on a middle CR up to 11:1, the off boost power will be agressive and powerful before the spool. Cooling and boosting, turbo sizing and ECU tuning will be some of the battles in such a motor. For one, you dont have to boost as much to see the same gains and two man would it ever be expensive. people turboing at all should not expect reliability like and OEM car. expectations are the biggest problem I see with this power hungry crowd. I dont see the B series motor making any more than 250 to the wheels reliably driven daily without eventual component failure wether it be stock of aftermarket. If you drive like a maniac, things break wether they are stock or not. These motors are great... but they are not bulletproof. NO MATTER what, things can go haywire. I say if you have a $10K budget for your motor and you plan on going turbo and plan to do so reliably, kudos. That sounds someone who has considered the *** end of a project where the rubber meets the road. If you are looking to impress friends for a few weekends go the cheap way out. If you want to play with the big boys, total immersion and money is the only way... thats considering the fact that you have the people that know what they know and can make your animal work at the end of the day. If you want to break stuff, kewl if you plan on boosting reliably it will take a huge investment of everything to make it happen. Turbo hondas must be fun... God knows I'd love to have a turbine in my engine bay but every time I look at thinking about one... the economics for such a car daily driven seems unattainable.

rice r0cket

Nice copy and paste. Anyways, you (or the author of this fine piece of work) spout off a lot about these professional drag racers running 14 : 1 CRs, etc...but you miss a couple pts. #1, they have total control of the fuel put into their cars. #2, they rebuild their engine after EVERY EVENT. That's the "big secret"...there is no reliability. First, with pump gas...do you actually know what's going in your car? No...you just assume. These little factors are things you can't control, but something professional drag racers can, and thus, will cause you reliability problems. If you think you're gonna be able to run that high CR w/ a turbo and NOT detonate, you're insane. Also, with any increase in hp, you're gonna stress your rods and rod bearings to something that wasn't factory spec'ed, and thus, you're gonna have reliability problems. A turbocharger + high CRs is gonna make this even more of a prominent problem. Also, you complain a lot about tuning...and we don't "deserve a turbocharger" if we don't spend time to tune our cars. With ECU controlled fuel maps feeding in from O2 sensors, MAFs, and everything, how is a consumer going to "tune" their car? As a consumer, it's unrealistic to create our own ECU program. Use carbs and then you can whine about that.


[Modified by stealthx32, 7:20 AM 8/29/2002]