Tricks to running just a tad more timing up top
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From: Butt**** Nowhere
Tricks to running just a tad more timing up top
I'm right at the point where my 6500-8000 rpm range makes good power with 10* of timing on my '03. But it knocks here and there. Sometimes 1 count, sometimes 4 counts. I lowered it down to 8, but the power is not there. You guys have any tricks to help the car run more timing up top?
Thanks!
Thanks!
go up to you periphery bits (FCA) and turn off the p0300 checks by setting bits 4 and 5 to 0.
Then do a few pulls and see what kind of knock you get near peak torque and in the 4500-5800 rpm range.
I get a couple of 1 & 2 counts, up to 3 at peak torque but I am still able to get around 11 degrees at the rev limit. I am not running a lot of boost either. You will have to put up with a "reasonable" amount of boost taper and make sure you have no large jumps in timing as you move from one load cell to another in the fuel and timing maps. That's really the most important part, keep the load cell transitions as smooth as possible.
Then do a few pulls and see what kind of knock you get near peak torque and in the 4500-5800 rpm range.
I get a couple of 1 & 2 counts, up to 3 at peak torque but I am still able to get around 11 degrees at the rev limit. I am not running a lot of boost either. You will have to put up with a "reasonable" amount of boost taper and make sure you have no large jumps in timing as you move from one load cell to another in the fuel and timing maps. That's really the most important part, keep the load cell transitions as smooth as possible.
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From: Butt**** Nowhere
I'm just running a ported 9 turbo, 24psi, 91octane
So chrisw, you just run it with the counts of knock that you get up top? Am I hurting anything with 1-4 counts of knock?
I've smoothed out the map as best I could. I'm going to try and give it a bit of fuel and see how it likes it. I'm running a MBC so it tapers off pretty badly.
So chrisw, you just run it with the counts of knock that you get up top? Am I hurting anything with 1-4 counts of knock?
I've smoothed out the map as best I could. I'm going to try and give it a bit of fuel and see how it likes it. I'm running a MBC so it tapers off pretty badly.
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From: mnt vernon ny
1-4 knock isnt bad... if it isn't consistent.. i had the same prob i ran 17* up top at about 19-20psi (thats what it tapered too) when the i.c got heat soaked it would knock so i just pulled a * just because it was getting warmer out side. also your running 91 oct.... 93oct may allow you to do more.. but find a smooth road to do your pulls and try VDR5.1 and see which helps out more or enriching to 10.5 to add more timing or pulling that 1*. do you know what load your at up top redline? i drop to 200-210ish... maybe your hitting high so there for you cant get away with much....
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I'm just running a ported 9 turbo, 24psi, 91octane
So chrisw, you just run it with the counts of knock that you get up top? Am I hurting anything with 1-4 counts of knock?
I've smoothed out the map as best I could. I'm going to try and give it a bit of fuel and see how it likes it. I'm running a MBC so it tapers off pretty badly.
So chrisw, you just run it with the counts of knock that you get up top? Am I hurting anything with 1-4 counts of knock?
I've smoothed out the map as best I could. I'm going to try and give it a bit of fuel and see how it likes it. I'm running a MBC so it tapers off pretty badly.
If your transmission hasn't been rebuilt it's possible that you also need the TSB applied for the 5th gear syncro's. In the '03, these gears would throw off harmonics that caused false knock. typically (ok, 99.9999999999999999% of the time) you see this when you get a p0300 on light throttle in 5th gear.
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From: mnt vernon ny
get rid of the MBC. Like hediki12 said, 1-4 counts are not bad as long as they are not consistant. I would keep the AFR's in the low 11 to high 10's. If you run too rich you will not be able to raise the timing as much. It's really kind of a balancing act between how much timing you run as opposed to how rich or lean the mixture is.
Here is a post i made back in 07 regarding AFRs.
Originally Posted by iTune
It's a known fact that a lower mixture density burns slower than the reverse. The speed of the flame front resulting from the ignition sequence, is dependant on the the density of the mixture and AFR's amoung other obvious factors. i will leave out the other factors because we are not debating them. Factors like fuel octane, temps ect. are not what we are discussing, since we are not targeting a specific condition, rather, a general condition. we are talking about AFRs, all else considered.
richening up the Air/Fuel mixture results in a slower flame front speed, thus results in a slower burn. This effect allows you to move the peak pressure later in the combustion process, which allows for more ignition advance, which creates more torque, because the peak pressure, is later in crank angle.
The faster the burn rate and the closer the peak cylinder pressure is to TDC, the more likely conditions will be right for detonation.
If you lean an engine out more, you will have to retard ignition timing to create the same conditions and to keep detonation in check. IF you lean an engine out too much, and are forced to retard ignition timing a lot, your EGT's could be higher than ideal.
Of course, we all know that using leaner AFR's and less ignition advance will make a little more power, but is it actually safer? Is the few extra ponies gained actualy worth tuning on the ragged edge? My personal opinion is that richer mixtures do result in less power, but are safer.
I DON'T combat detonation with richer AFR's, i combat detonation with ignition timing. I'm not like some tuners that feel as though it's OK to throw a bunch of ignition timing at a engine and if it knocks, well just add more fuel. I tune for conservative AFR's and what ever the engine wants for ignition timing, i give it.
I think it's important to understand when and why you want to slow the burn rate. There are some incidents where the burn rate is not out of control, therefore there would be no reason to slow it further. But, to make it clear, a leaner AFR can eventually become unstable in some conditions. These conditions can be detonation rich enviroments if a lean condition is allowed to continue. The extent of what is considered lean is whats in question.
Quote:
Originally Posted by iTune
The faster the burn rate and the closer the peak cylinder pressure is to TDC, the more likely conditions will be right for detonation
Quote:
Originally Posted by iTune
richening up the Air/Fuel mixture results in a slower flame front speed, thus results in a slower burn. This effect allows you to move the peak pressure later in the combustion process, which allows for more ignition advance, which creates more torque, because the peak pressure, is later in crank angle.
Think of why we use high octane race fuels. By using a slower burning, less erratic combustion fuel, we can run leaner AFR's and more ignition advance, which results in more power. This also allows us to run more boost safely. Fuels are measured by knock resistance. The higher the octane, the slower more controlled the fuel burns. This raises the detonation threshold of the fuel.
Quote:
Originally Posted by iTune
If you lean an engine out more, you will have to retard ignition timing to create the same conditions and to keep detonation in check.
The key is to make peak pressure, later in crank angle, where there is more leverage on the crank. This creates more torque. Slowing the burn process, allows us to use more ignition advance, which will put the peak pressure, again later in crank angle.
Like stated above, if you lean an engine out more, you WILL have to retard ignition timing a bit to control detonation. This speeds up the burn process, but puts ignition advance later. Both will put peak pressure later in crank angle, although a leaner mixture will make a bit more power, because it can actually be tuned to put peak pressure even later in crank angle.
There is no question that a leaner AFR will make more power, which means the engine is obviously more effecient. But at what point do you reach the point of diminishing returns? Where you sacrifice power for reliability? Running a leaner AFR leaves little room for error. Unfortunatly, we don't live in a perfect world and conditions are always changing. ECU's do have correction factors, they must be set-up properly in order to work properly. But, there are other unforseen factors that can happen. Especially when dealing with turbocharged, high powered engines. Where the margin or error is greatly reduced.
CJ
richening up the Air/Fuel mixture results in a slower flame front speed, thus results in a slower burn. This effect allows you to move the peak pressure later in the combustion process, which allows for more ignition advance, which creates more torque, because the peak pressure, is later in crank angle.
The faster the burn rate and the closer the peak cylinder pressure is to TDC, the more likely conditions will be right for detonation.
If you lean an engine out more, you will have to retard ignition timing to create the same conditions and to keep detonation in check. IF you lean an engine out too much, and are forced to retard ignition timing a lot, your EGT's could be higher than ideal.
Of course, we all know that using leaner AFR's and less ignition advance will make a little more power, but is it actually safer? Is the few extra ponies gained actualy worth tuning on the ragged edge? My personal opinion is that richer mixtures do result in less power, but are safer.
I DON'T combat detonation with richer AFR's, i combat detonation with ignition timing. I'm not like some tuners that feel as though it's OK to throw a bunch of ignition timing at a engine and if it knocks, well just add more fuel. I tune for conservative AFR's and what ever the engine wants for ignition timing, i give it.
I think it's important to understand when and why you want to slow the burn rate. There are some incidents where the burn rate is not out of control, therefore there would be no reason to slow it further. But, to make it clear, a leaner AFR can eventually become unstable in some conditions. These conditions can be detonation rich enviroments if a lean condition is allowed to continue. The extent of what is considered lean is whats in question.
Quote:
Originally Posted by iTune
The faster the burn rate and the closer the peak cylinder pressure is to TDC, the more likely conditions will be right for detonation
Quote:
Originally Posted by iTune
richening up the Air/Fuel mixture results in a slower flame front speed, thus results in a slower burn. This effect allows you to move the peak pressure later in the combustion process, which allows for more ignition advance, which creates more torque, because the peak pressure, is later in crank angle.
Think of why we use high octane race fuels. By using a slower burning, less erratic combustion fuel, we can run leaner AFR's and more ignition advance, which results in more power. This also allows us to run more boost safely. Fuels are measured by knock resistance. The higher the octane, the slower more controlled the fuel burns. This raises the detonation threshold of the fuel.
Quote:
Originally Posted by iTune
If you lean an engine out more, you will have to retard ignition timing to create the same conditions and to keep detonation in check.
The key is to make peak pressure, later in crank angle, where there is more leverage on the crank. This creates more torque. Slowing the burn process, allows us to use more ignition advance, which will put the peak pressure, again later in crank angle.
Like stated above, if you lean an engine out more, you WILL have to retard ignition timing a bit to control detonation. This speeds up the burn process, but puts ignition advance later. Both will put peak pressure later in crank angle, although a leaner mixture will make a bit more power, because it can actually be tuned to put peak pressure even later in crank angle.
There is no question that a leaner AFR will make more power, which means the engine is obviously more effecient. But at what point do you reach the point of diminishing returns? Where you sacrifice power for reliability? Running a leaner AFR leaves little room for error. Unfortunatly, we don't live in a perfect world and conditions are always changing. ECU's do have correction factors, they must be set-up properly in order to work properly. But, there are other unforseen factors that can happen. Especially when dealing with turbocharged, high powered engines. Where the margin or error is greatly reduced.
CJ
To add to ITunes post, it's possible to cause knock by running too rich as well.
Running too rich can cause uneven burn rates inside the combustion chamber. The uneven burn produces lean spots in the chamber where detonation thresholds can be reached.
Running too rich can cause uneven burn rates inside the combustion chamber. The uneven burn produces lean spots in the chamber where detonation thresholds can be reached.
Think of why we use high octane race fuels. By using a slower burning, less erratic combustion fuel, we can run leaner AFR's and more ignition advance, which results in more power. This also allows us to run more boost safely. Fuels are measured by knock resistance. The higher the octane, the slower more controlled the fuel burns. This raises the detonation threshold of the fuel.
Maybe this will help you.
Maybe this will help you.
Great post but I don't agree 100% with this quoted part. Race fuels don't burn at any slower rate than pump gas by any means they simply have a better ability to increase deflagration with much less chance of knock or detonation.
An octane rating is related to a fuel's auto-ignition temperature. The higher the octane rating, the hotter the cylinder has to be before it auto-ignites aka detonation. Detonation resistance does not directly correlate to burn speeds (again, refer to detonation vs. deflagration: they are two completely different forms of combustion).
Octane rating tells us absolutely nothing else: not burning speeds, not energy content, not engine temperatures, etc etc. High octane gasolines are harder to explode (i.e. detonate) they are not harder to burn or ignite (i.e. deflagrate). Methanol (114 octane +/-) actually is more easy to ignite than gasoline but it being almost half the energy content it still burns at a very similar rate to gas.
A "true" race fuel should actually help create a better contact with the air molecules causing a faster burn speed aka deflagration then due to "octane" allow for higher cylinder pressures and more heat.
Evan Smith
Last edited by esevo; Mar 16, 2010 at 10:56 PM.
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