Bruce
01-14-2004, 04:08 PM
So, you've installed a block off plate, and have no EGR worries, right?.
Well, there's what called self-EGRing.
Well, what the Heck is That?.
For the purpose of this thread, ie EGR 101. We going to ignore the fact that in some limited applications you can reach Cross-Over. Cross-over is when you have less backpressure then amount of boost your running.
In some street car applications you can have as much as 35 PSI of backpressure with as little as 15 PSI of boost.
And in that same car you might have just a 1-2 of backpressure, while the engine is in vacuum, while idling.
Next is something that alot of folks don't get, don't want to accept, and will just be in denile about. Overlap, which is when the exhaust valve is closing, and the intake just opening is a really critical component of breaking the fuel gobules into small enough particle that will react in the combustion chamber. What happens during overlap, is that there is a wave formed as the intake valve opens, and that wave is so strong that it atomizes the fuel into very small particles. Also, that wave, under just the right circumstances can pass on up the runners, intake tract, in a condition known as reversion. Reversion is just mentioned here as a primer.
So you've installed a bigger cam.
And off thing is you have to add fuel and timing now to get a decent idle.
Any insights?.
Now with the faster closing, and opening rates, mixed with possible a longer amount of time. The wave action is being diluted. So the fuel doesn't want to get broken up into really tiny particles. You have gobules, that are poor burning so you have to give em more time to burn, so you have to add more timing. The wave is more an more lost so, the whole process to a certain degree defeats getting a really nice idle. More cam, more fuel, more timing, rougher idle. There even comes a point where the idle is soo poor that you have to increase the idle speed, and use the energy in the flywheel to keep the engine running. And with a lighter converter, there is less inertia, so again we have things snowballing.
But, as the rpm come up, the engine's VE vastly improves, and you get to where the corrections aren't too large until you get to where you've actually improved the engine's VE, and then you need to get really serious about tuning.
Well, there's what called self-EGRing.
Well, what the Heck is That?.
For the purpose of this thread, ie EGR 101. We going to ignore the fact that in some limited applications you can reach Cross-Over. Cross-over is when you have less backpressure then amount of boost your running.
In some street car applications you can have as much as 35 PSI of backpressure with as little as 15 PSI of boost.
And in that same car you might have just a 1-2 of backpressure, while the engine is in vacuum, while idling.
Next is something that alot of folks don't get, don't want to accept, and will just be in denile about. Overlap, which is when the exhaust valve is closing, and the intake just opening is a really critical component of breaking the fuel gobules into small enough particle that will react in the combustion chamber. What happens during overlap, is that there is a wave formed as the intake valve opens, and that wave is so strong that it atomizes the fuel into very small particles. Also, that wave, under just the right circumstances can pass on up the runners, intake tract, in a condition known as reversion. Reversion is just mentioned here as a primer.
So you've installed a bigger cam.
And off thing is you have to add fuel and timing now to get a decent idle.
Any insights?.
Now with the faster closing, and opening rates, mixed with possible a longer amount of time. The wave action is being diluted. So the fuel doesn't want to get broken up into really tiny particles. You have gobules, that are poor burning so you have to give em more time to burn, so you have to add more timing. The wave is more an more lost so, the whole process to a certain degree defeats getting a really nice idle. More cam, more fuel, more timing, rougher idle. There even comes a point where the idle is soo poor that you have to increase the idle speed, and use the energy in the flywheel to keep the engine running. And with a lighter converter, there is less inertia, so again we have things snowballing.
But, as the rpm come up, the engine's VE vastly improves, and you get to where the corrections aren't too large until you get to where you've actually improved the engine's VE, and then you need to get really serious about tuning.