WeaselGSR said:
Your math is a little off, but the idea is good
First of all, you would multiply your compression ratios
You would multiply the compression ratio of the turbo time the compression ratio of the engine
For an ideal gas
14.7 psia air (atmospheric) fed into a 10:1 engine would have a cylinder pressure of 147 psia at the end compression stroke
When running 10 psig of boost to a 10:1 engine would have a cylinder pressure of 247 psia at the end of the compression stroke or 1.68 x 10
Neither my math, nor your math are off...we both arrive at the same number, we just use different entrances.
Everything is a give and take. You take some of #1, then you have to give some of #2, and vice versa.
The aim of this article is to those who have posed the question of whether they want to build their motor, or leave it stock.
Here is the deal, and I will explain it with a hypothetical situation:
Johnny Smith has a 2000 Si. Stock motor, nothing done to it. Johnny wants to turbocharge his car and make around 320hp. Conventional knowledge says that Johnny MUST build his motor, thereby spending close to $4,000 just for the motor itself, then add $3,200 for a turbo kit, and another $1,500 for fuel and spark, and then $1,200 for engine management...don't forget $200 for a dyno session. Johnny just spent close to $10,000 building his motor and turbocharging his car. Don't forget about hidden costs, maintainence, gauges, electronics...etc.
Now Johnny has a fully built motor, and his car is fast.
But wait...little does Johnny know that his stock engine can sustain that amount of power indefinitely, should it be well taken care of and properly tuned. It's not hard, it's not taboo. Subtract the $4,000 for the built motor, and add maybe $250 for a spare B16A shortblock, should you get overzealous one day and blow your shit.
Now, all of us who have had, or who have a POWERFUL street Honda know, that anything more than 300hp is somewhat poinless on the street. Traction limitations are rampant at that stage. So what is the point of making 550hp boosting 32psi on your 7.0:1 motor, when my little 260whp Civic will leave you in it's dust (as you leave yourself in tiresmoke), at the stoplight?
I write my articles, and base my tech around street enthusiasts. If I were writing for another aspect, my articles would be different.
Stock compression (otherwise known as high), is your best bet for the street. Not only does it afford you a more even powerband, power coming in earlier and faster...but in reality, it isn't even that high. If stock Hondas were running at 12.5:1...then yeah, we're breaking the rules, but the stock compression is not high. It is ideal. Far more efficient for a streetcar, than a low compression engine is. If it's hot as hell out, just make sure you are using high octane (you should regardless), be careful...don't get overzealous...and if it comes down to it, back down the timing a bit.
I have had two stock/high compression turbo setups, and there was a reason that my car was king of the valley I live in, lol...sounds corny, but it was true.