thinkbrianthink bu

I know the classic ideal is low compression for boost, high compression for n/a.

BUT if one wanted to run higher compression, logically the lower the boost you run the higher the compression you could run safely. Ideally, the higher compression would benefit you when not in boost but the low boost level would keep this safe.

My question is, on a given setup...
b20
pistons
rods
blockguard
hondata
8lbs daily - 10lbs max
What would be the safest compression you could run?

9.5:1?
10:1?

filetofit

https://honda-tech.com/zerothread?id=292297

The_Head

The lower the compression, the safer it would be. Ceteris paribus


I once had this idea, I think it would be a killer setup for the street.

built B16A
10:1 pistons
smaller turbo, say a T3
medium boost (~11psi)

4.745:1 or 4.9:1 FD ratio
LSD

*shrugs shoulders*

*Boostwerks*

All that needs is a hobbs controled water/alch injection

EDIT:

QuickHonda runs a 10:1 CR in his ZC. Runs 14psi on his Drag3 kit on pump gas. High boost and high CR CAN Be done safely. It is a FACT.


[Modified by Bryson, 1:35 PM 10/11/2002]

thinkbrianthink bu

Good info in the link... If you can understand it (i did... kinda)

I understand the fact that your talking about two different compression factors in this case and that raising engine compression will not necessarily raise your peak horsepower. What im aiming for is more "oomph" in the low end as a result of higher compression but also keeping it safe at 10lbs on the high end.


[Modified by thinkbrianthink, 2:46 PM 10/11/2002]

ekb18c

10:1 and boost is safe for the street.

<--10:1 and 14psi on street for over 1 year now.

MatT3T4

I ran my stock B16A (10.4:1?) between 10-17psi every day, for two years before I decided to build it. Lowered the CR to 9.5:1...bad choice...pound for pound, it was weak as ****.

I think that one thing enthusiasts need to understand, is that wehn we are talking about high compression...we're talking 12.5:1, etc...STOCK Honda compression, really isn't that high afterall...Not even close to being high enough to cause such catastrophic failures that all of the low comp guys are always talking about.

MatT3T4

thinkbrianthink bu

Good info.

This is the type of responses i was looking for. You always hear of ppl saying 8.5:1 and 9:1 but then these figures are also mentioned full race setups. I figured there had to be a happy medium for a small boost application.

Thanks guys,
brian

-tech.com


[Modified by thinkbrianthink, 3:19 PM 10/11/2002]

filetofit

Higher engine compression will raise the temperature of the compressed air/fuel mixture by definition. Higher temperature mixtures put you closer to the spontaneous ignition point ( =detonation, bad) all other things being equal like octane, timing etc. But if you can get away with higher compression at the boost level you want to run with pump gas and not too much timing retard, hell more power to ya. It just means your closer to the edge that's all. All together now, tuuuuning.

MatT3T4

tuuuuning.

I like your style.

I guess what a lot of people don't understand is that, for a STREET application, the stock compression in the B-series motors is fine. Even in the R motors it's alright (kinda pushing it, but still alright...if it wasn't for the lightweight internals).

ee8T

Also planning on building b16a1 for street. 10:1 and bout 14psi. In Europe we have 98 octane.............

What tuning should you guys advise? Already running 6psi GReddy kit, lost blue box, Vortech FMU, Bosch inline 220lph.

dustin

"It's all in the tuning".. I hate that phrase..

Uh huh... Well on pump gas .. you have to run so much timing retard to avoid detonation that there is an obvious point of diminishing return in running high boost.

Read this, these people know what they are talking about:

http://www.sdsefi.com/meltdown.htm

On 91 octane, with 10:1 compression you can run about 10psi at most before the thing pings. Then you get to pull so much timing that you start losing power per extra pound of boost..

MatT3T4

Ok, here is what I don't understand.

Stock B-series compression...anywhere from 9.2:1-10.6:1 or so...is not high. We are talking about street cars here. That amount of static compression does not warrant extreme timing retard, and 116 octane fuel. I think that some people confuse HIGH compression for stock compression. When hundreds of enthusiasts can easily and successfully boost their motors, and have it last a long time, with no problems...on stock compression, what is the problem?

You know where the point of diminishing returns becomes a problem? It becomes a problem when you are making so much power, you can't keep traction. That is why I don't see the purpose of building a street car. You WILL reach the point of diminishing returns with stock compression, safely...so why spend $4,000 just so you can lower your compression, and hit that threshhold anyway?

It works well both ways, don't get me wrong...lowering compression makes sense and it a feasable option, but on a race car. It doesn't make too much sense on a car that can't reap the benefits of being able to boost 69864599psi on a 7.0:1 motor...on the street.

dustin

Here is another good link from people that actually know about engines

http://www.sdsefi.com/techocta.htm

dustin

Stock honda static compression ratios are not high for naturally aspirated motors. Understand that boost directly affects DYNAMIC compression ratio. If your dynamic compression ratio was 10:1 N/A, then at 15psi of boost the dynamic compression ratio cannot be any lower than 20:1. You're putting twice the volume into the same space. Do you not think that if Mitsubishi, Subaru, etc could reliably yield better gas mileage and higher power output by increasing static compression ratio, they would?

They do not last a long time. Look how many people here crack ring lands. You can't run high boost (>10psi) with reasonable ignition advance on pump gas RELIABLY with 10:1 compression. It might work now. It might work for a friend. It might work for a guy in your 'krew'. It might work for this guy you know that talked to this other guy who has this really sweet *** car. But it's not going to work forever -- You will break something.

I do know where the point of diminishing return is. When you with your 10.2:1 B16 motor want to go from 10 psi to 15psi of boost, you realize that you have to retard timing so much that you are barely making any extra power.

Seriously, lowered static compression ratio has nothing to do with race/street/whatever. Cars with lowered static compression drive just fine. When was the last time a WRX owner complained about their 8.0:1 static CR? Torque is torque. Who cares that the static compression ratio has been lowered to allow the car to make more power on pump gasoline. Octane and static compression ratio ARE the limiting factors of power output. You can't have your cake and eat it too.

brian b

My new motor is 11.4:1 with 25psi.. I wouldn't try to run high without standalone though, you need a way to acurately control timing and fuel..

dustin

And lots of race gas

MatT3T4

"We have a hypothetical engine."

They're talking about a hypothetical engine, I can make a hypothetical engine look like anything. I'm not disagreeing with you, but I am saying that all of this whoopla about things being so dangerous with their stock motor is just that...whoopla. Unless you've actually done it numerous times, you won't know it. We're talking about street cars here, race cars are a different story.

There are a lot of factors that come into play: weather conditions, driving conditions, octane, timing, etc...In NORMAL street conditions, the average enthusiast knows what he is doing, and on a stock motor, isn't endangering himself too much. It's like a mass hysteria that I just don't understand.

Maybe I am special though, because I can run for 2 years on a stock B16A boosting 10-17psi revving up to 9,000rpm. Well, myself, and all of the other cars I had my hand in building. I am blessed.

MatT3T4

NOTHING lasts. Reliability is only a matter of time factor when you take a motor designed for NA, and turbocharge it. Built or stock, I've NEVER seen ANYTHING last. I lasted 2 years stock, then built it because I wanted to. Mistake on my part. Every built motor I have come across has suffered the same consequences as stock ones.

Replace a built motor: $4,000
Replace a stock motor: $400

dustin

Hey mat, a google search with your username revealed this

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

I think you wrote that, or someone who stole your name did...

Your argument is that adding boost to yield higher dynamic compression will not make more power than the motor that started with higher static compression...

But, understand, that the power output of an engine is directly related to its ability to burn FUEL. When you add boost, you get to add fuel! Increasing static compression ratio sure does increase peak cylinder pressure... But burning more fuel yields more area under the "cylinder pressure curve"!

Bottom line.. the engine that burns more fuel is gonna win.

falcongsr

nah pump gas and set ignition timing 10 degrees after TDC.

edit - this post is a joke. just so you know. ha ha. you're not laughing. nevermind.

dustin

This sounds like a cop out argument to avoid the laws of physics and thermodynamics...

MatT3T4

Yeah I know. A mistake on my part, I failed to go deeply into the whole enchilada. That is my fault. I did not get into the aspects of octane, temperature, etc...I kinda assumed most people would know that when I made an allusion, it was to a motor with appropriate fuel/ignition setup, etc...That was my fault.

MatT3T4

Hey, cop out or not...if it works it works. One thing that I have realized after years of doing this, is that A LOT of what looks one way on paper, looks totally different on the street. Like I said...if it works, it works. It's up to the individual to choose which way they want to do it, but it's not fair to only feed them ONE side of the argument.