AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 26,611
- Reaction score
- 13,844
All this Compression Ratio talk is hurting my head.
Our gasoline engines are heavily throttled, so the average EFFECTIVE compression ratio on every trip around the block, or whatever, is gonna be paltry. So then our engines really need tiny chambers to force the molecules of air and fuel into close proximity to eachother, before lighting it off so that it will All have time to oxidize, and be finished burning, leaving nothing but hot expanding gasses to do their work at the appropriate time before the piston gets away.
Really, the only time a streeter cares about Scr is at WOT.
If you only have a very small carburated engine, I guess Scr is important.
But a 318+ cid streeter is rarely over 1/2 throttle. Most of the time it could be a 1-barrel, and still make enough power to be streetable, so in this situation, Scr is relatively unimportant especially to the driver.
But because the engine is seeing operationally Effective compression ratios that vary so drastically from one moment in time, to another, how can emissions be controlled over the whole range? With a butterfly-valve carb, that's gotta be a pretty tall order.
What gasoline cars really need is a mechanically variable compression ratio engine.
And I suppose that, the iVVT engine is a step in that direction by being able to vary the Dynamic Compression Ratio, by manipulating the intake valve timing events, which does about the same thing. Unfortunately, iVVT is a lil complicated and somewhat failure prone.
==================
I built my engine to be able to arrive at an Scr that varies about a 1/2 point, yet has adequate squish, just by the use of gaskets of various thicknesses. Then I varied the Ica, to arrive at a place where I was personally satisfied by the power/versus economy thing (DD), and the bonus was that it ran on 87E10 at full power with full-timing.. I was hoping it would, but didn't actually plan that. I was just hoping it would run on 91, and was even prepared to run water/alcohol injection; I was very pleasantly surprised, when neither was required.
Emissions was not on my radar.
As for emissions, well that is just too complicated for this cowboy. Well,some aspects are.
I think that most of what was or is called "emissions regulation", was engineered to drive profits of, more low-octane gas being able to be produced from a barrel of crude, making rich folks richer. But I readily admit, that I just don't know that. It's getting harder and harder every day, to sift knowledge, to find the facts. I think that I might have been happier before I ever heard of the internet. I know for a fact that I was more productive.
Our gasoline engines are heavily throttled, so the average EFFECTIVE compression ratio on every trip around the block, or whatever, is gonna be paltry. So then our engines really need tiny chambers to force the molecules of air and fuel into close proximity to eachother, before lighting it off so that it will All have time to oxidize, and be finished burning, leaving nothing but hot expanding gasses to do their work at the appropriate time before the piston gets away.
Really, the only time a streeter cares about Scr is at WOT.
If you only have a very small carburated engine, I guess Scr is important.
But a 318+ cid streeter is rarely over 1/2 throttle. Most of the time it could be a 1-barrel, and still make enough power to be streetable, so in this situation, Scr is relatively unimportant especially to the driver.
But because the engine is seeing operationally Effective compression ratios that vary so drastically from one moment in time, to another, how can emissions be controlled over the whole range? With a butterfly-valve carb, that's gotta be a pretty tall order.
What gasoline cars really need is a mechanically variable compression ratio engine.
And I suppose that, the iVVT engine is a step in that direction by being able to vary the Dynamic Compression Ratio, by manipulating the intake valve timing events, which does about the same thing. Unfortunately, iVVT is a lil complicated and somewhat failure prone.
==================
I built my engine to be able to arrive at an Scr that varies about a 1/2 point, yet has adequate squish, just by the use of gaskets of various thicknesses. Then I varied the Ica, to arrive at a place where I was personally satisfied by the power/versus economy thing (DD), and the bonus was that it ran on 87E10 at full power with full-timing.. I was hoping it would, but didn't actually plan that. I was just hoping it would run on 91, and was even prepared to run water/alcohol injection; I was very pleasantly surprised, when neither was required.
Emissions was not on my radar.
As for emissions, well that is just too complicated for this cowboy. Well,some aspects are.
I think that most of what was or is called "emissions regulation", was engineered to drive profits of, more low-octane gas being able to be produced from a barrel of crude, making rich folks richer. But I readily admit, that I just don't know that. It's getting harder and harder every day, to sift knowledge, to find the facts. I think that I might have been happier before I ever heard of the internet. I know for a fact that I was more productive.
