EB thanks again for the advice. I've been running 'round the last couple of days trying to find a machine shop I trust to machine my parts. I read what you said about port and polishing the head and was still wondering: Is back pressure a key ingredient in 'Yota performance? I've thought about going ahead and porting and polishing the exhaust side to let it breath a little easier with just a little work on the intake (just smooth up a few rough spots, not a full port on the intake.) I know what happens when intake porting get's out of control: high rpm engines are born and "bye-bye gas friendly daily driver." Would a good exhaust port cause any harm or do I need a certain amount of back pressure? I hate to keep aggravating but I've found that the answers from here are a lot better than the ones from the grinning, "built a hundred of them" teen-ager working down at the NAPA!
>>>*Remember the one rule of thumb is that most exhaust systems are adequate for the design. The only time real gains are made is when the system is overly restrictive, other than the obvious due to torque multiplication.
Now the typical 22R/RE is a bit on the restrictive side in stock form. The factory goal appeared to be to keep the engine nice and quiet, yet responsive at lower speeds.
So normally opening up the exhaust will improve the power numbers because the engine will peak at a higher RPM and typically rev to a higher RPM.
So the answer is yes, within limits. And yes, some back pressure is needed, this is because it takes time to get air/fuel moving and once we do we want it in the cylinder and not the exhaust system. So to make an engine create acceptable power at very low RPM's we restrict cross flow with back pressure, this keeps the goody, (the air and fuel) from reaching the exhaust port, giving that valve time to close and seal it off.
This keeps the fuel and air from going out the exhaust before it does any work. At higher speeds, we don't need as much if any back pressure, and there is a point in there where a vaccum is a benefit.
So any design is a compromise to get the best of both worlds. Now if you are tearing around out in the woods, or trying to get to the other end first, we don't really care about backpressure.
*Sitting at a stoplight with a load of Cows in the back? Then you do....*LOL**..or climbing up over some rocks at low RPM where instant throttle response at very low RPM's can mean you don't dent the roof? You bet backpressure matters then.
Mild work to smooth up the exhaust ports really doesn't hurt anything at all. Working on the intake side can add actual power through better cylinder fill. Of course again there are limits, run a port that might work on a big bore Chevy with the much smaller 22RE cylinder and at low speeds all you will get is flames, the velocity drops, fuel falls out of suspension.
Manifold standoff, that is called. It creates nice burnt spots on the hood..
When that happens, the air runs into the cylinder nicely, the fuel just sits there. The fast flamefront escapes out the open intake valve before it can close and seal off the works.
It's all a balance, porting on the 22RE head is touchy so be careful and don't remove very much...*EB
