the limits are your cylinder compression. you can lift heads on these cars readily without taking the proper precautionary measures. fuel is your biggest limit in general though, as it is what is creating the power. obviously if you knock early enough and frequently enough, your limits would be whatever your pistons/rods/crank/bearings can take.
upsides are that you can make the same power at a lower boost level. to be honest, the honda platform doesnt even tune for knock detection, they tune for most power made. i have a lot of honda buddies that are actually knowledgeable and not just honda fanbois, and they have made some impressive numbers out of their little engines. they last as well, but that has a lot more to do with honda materials engineering than anything. they are durable little engines.
there is also a benefit of more torque with higher compression, whereas you can have a higher horsepower with lower compression. higher compression changes quite a few things, and depending on your ecu, it may not like it as well.
im being nice and playing this question game here, but what is your goal? high compression boosted engines are nothing new, not even for this platform. there is no secret to it, its physics and intuition that will tell you what you can and cannot, should and should not do. if you are sticking to super charging, you very well may want higher compression because you probably wont push that much boost. you will need to make sure your intake temps dont get too high because that will set off detonation earlier as well.
are you the older (40's maybe) guy that came to NG with the red supercharged 3k?
rise and rise again until lambs become lions
I'm not sure what you're looking for...? A lesson in simple physics? how a motor works? Maybe I'm not grasping the question, but it seems pretty simple to me... Do you understand why you can't run 20:1 compression in a gasoline motor? If you increase the volume of air in the cylinder by one atmosphere, you've already compressed it 2:1. Do the math, and you'll find that the difference in compression between our N/A motors and turbo motors is no accident...
You raise a good question, maybe I can help shed some light without talking about specifics.
The higher the compression ratio (CR) the more power an engine will deliver. With that said The rule of thumb is that a higher compression engine (HCE) will perform much better 'off boost' than a lower compression engine because it has its own natural compression to generate power. Generally speaking a HCE will not have as big a jump in power as will a lower compression engine (LCE) will have as boost is applied. Normally the boost threshold will be much lower in a HCE than in that of a LCE.
Normally speaking the higher the compression ratio, the more basic or natural torque the engine will produce. By adding boost, regardless of the means, increases the effective compression of an engine. This increase in cylinder pressure will translate into more power and torque due to greater expanding exhaust pressures.
By dropping the compression ratio allows a higher amount of boost to be used, which translates into a greater volume of fuel and air to be introduced into the cylinder. Naturally this generates more hp and torque - so long as the greater volumes of air and fuel are being delivered. Off boost the LCE will perform more poorly than that of the HCE.
As said by others, forced induction devices which increase effective compression ratios can and will cause denotation but that problem and well as other issues, due to increasing cylinder pressures, will have to be dealt with as boost pressures increase.
IMHO, a higher compression engine with moderate levels of boost make a good combination for a street machine.
There's also the benefit of better off-boost performance. Turbo lag is not as noticeable.
As for why you can't run higher compression and higher boost? There's no reason why you can't really. You'll be spending more money to use less boost, and I don't believe the higher comp is going to offset the hp loss from less boost. This chart isn't for our cars specifically (don't think anyone has done one specific to our vehicles) but it's not going to change much:
Not taking credit for this chart at all, but I can't find the one I had made for the Starion/Conquest group a decade ago so I have to make do.
Using this chart and knowing how much work 3S guys put into their cars to run specific psi on their cars can give you an idea of how much you will have to do as well. Want to run 15psi on 10:1? Prepare to build the car as if you were going 22psi on an 8:1 motor and you should be safe.
There are other variables that will change this depending on your setup (direct injection motors run higher compression and higher boost due to how the fuel charge is injected), but general rule when not talking about new, high tech motors is that higher boost + higher compression = lot more build money and more things to break.
Let me see if I understand, by lowering compression you are able to run more boost effectively by adding more air to the cylinder thereby generating more power. In higher compression engines power is derived not so much by adding air but more along the lines of compressing the air tighter.
Is this why big supercharged dragsters run compression ratios as low as 5 to1?
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