what should my timing advance be?
Apr 30, 2008, 08:29 AM
#31
so let me see if i understand this you are saying that 10.9 logged from a wbo2 is good for a tuned evo 8? if so i hope and pray you will never tune another evo. last time i checked the accepted and proven afr is 12.0 at spool and 11.5 to redline for maximum power. 10.9 idk wat to even say to that.
The car runs stock at 9.5:1 by redline. So running it at 10.9:1 is already 1.4 afr points leaner than stock.
People who tune on CA 91 octane follow similar AFRS. I am not re-inventing the wheel here.
Ask Razrolab. He has tuned more Evos on 91 octane than anyone else that I know of.
Apr 30, 2008, 08:37 AM
#32
so let me see if i understand this you are saying that 10.9 logged from a wbo2 is good for a tuned evo 8? if so i hope and pray you will never tune another evo. last time i checked the accepted and proven afr is 12.0 at spool and 11.5 to redline for maximum power. 10.9 idk wat to even say to that.
First of all there is no "accepted and proven afr". Secondly 10.9 on 91 octane is not excessively rich.
Real tuners know that you don't find rich best torque on the internet.
Last edited by Mr. Evo IX; Apr 30, 2008 at 08:50 AM.
Apr 30, 2008, 08:59 AM
#36
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its not NJ's car we are talkin about he has a IX he is saying that he tunes all VIIIs to that AFR and im saying that is rich. and it is. read anything about tuning cars in general not just evos and it will say anything in 10's is rich.
Apr 30, 2008, 09:04 AM
#39
I know that 12.5:1 is the AFR the produces the best power from gasoline. But running anywhere near that AFR on an Evo 8 with the boost levels you claim to be running will make the car knock.
I have tuned many Evo 8s on 91 pisstane and they almost all like ~11:1 AFR by redline. BTW it will make little to no difference if you run 10.9:1 or 11.2:1 by redline.
Apr 30, 2008, 09:25 AM
#40
This is a question without a simple answer. It is definitely easy for members and Tuners to just throw out a given AFR and say optimize timing by advancing spark to Minimum Best Timing (MBT).
I have been tuning cars for roughly 7 years and although I do follow a strategy each time I tune a car, each tune comes out just a little bit different because no car is identical, even if it has exactly the same mods! And honestly that is what I find so rewarding with tuning, sometimes its like solving a little puzzle.
I tend to side with l2r99gst in tuning technique. I like to shoot for an AFR and hit it right before Peak Torque and hold it till about redline. You need the most amount of fuel at peak torque because this is where your engine load is the highest and also where knock is most prone to start and occur. Obviously this is not the only place it can occur though.
At crusing loads I shoot for somewhere between stoichiometric (14.7:1 .... its actually more like 14.6 now days with the additives in our gasoline) and 15.5:1. By cruising loads I mean between 20 and 50 KPa (kilo pascals). Between these loads and under them, although you will rarely see under 20 KPa except for decel, you can truly run the car much leaner than stoich, even to the point where the car is audibly pinging and almost not enought fuel to keep the car running without much worry about engine damage. The reason being is that there is no real engine load at these conditions. (Obviously timing needs to be set accordingly)
At atmospheric pressure ( right around 100 KPa depending on elevation) I shoot for 12.5:1 AFR. In general this is the Max load a Naturally Aspirated engine sees.
Research has shown that an 4-stroke gasoline combustion engine will make the most power between 12:1 and 13:1 AFR. But as all of you seem to know, we run richer than this on turbo cars. The reason we do this is for the thermal management of our engines. Adiabatic Flame Temperatures (think of it as cylinder temperatures) are the hottest at a stoichiometric AFR. On either side of stoich, whether it is richer or leaner, flame temperature is cooler.
From cruise loads to atmospheric pressure I taper from stoich to this 12.5:1 AFR.
As an engine comes onto boost I progressively richen the car to my target just before peak torque and hold it at this AFR depending on the characteristics of the particular engine.
*If the car hits peak torque and holds that torque through redline, I hold my target AFR and possibly richen it up a bit to redline. (Ex: bigger turbo in its efficiency range)
*If the car hits peak torque and immediately begins to drop and continues to do so, I will sometimes begin to lean the car back out a bit to redline. (Ex: small turbo out of its efficiency range)
Again, it really depends on the engines setup and characteristics.
It is important to remember that as RPM goes up, Load goes down. This happens on both NA and FI engines and is because as RPM does go up, there is less time for the cylinders to fill with air. By 10,000 Rpm the intake valves are open for an incredibly short period of time, its a wonder that the air actually has time to move! Thank God for pressure differentials!
One last thing.... and one of the reasons it is so hard to just say "Use This:". It is completely possible to make the same amount of torque (and hp, which is related to torque by an algebraic equation) at a given Load and RPM with a fairly wide range of AFR's. Timing does "create power" as some have said, but only to the extent of maximizing it for a given AFR. At a given Load and RPM, I can be on the dyno and make XXX lbft at an AFR of 11.7 and 17 degrees advance, then richen the AFR up to 10.2 and use 23 degrees advance and make the same amount of torque. (The mentioned numbers are just an example to get the point across)
So to say use this AFR is really pointless if you know what you are doing, and the AFR you choose is within the window where the car will make the most power, and you optimize your timing accordingly. Too much timing advance without enough fuel will cause irregular combustion (detonation) and if there is enough fuel, too much timing can cause pressures to be so high before TDC that the piston is actually having a hard time moving up. Too little timing (or to much retard) can cause EGT to become extremely high. Timing greatly effects EGT's.
Just thought I would share some info.
I have been tuning cars for roughly 7 years and although I do follow a strategy each time I tune a car, each tune comes out just a little bit different because no car is identical, even if it has exactly the same mods! And honestly that is what I find so rewarding with tuning, sometimes its like solving a little puzzle.
I tend to side with l2r99gst in tuning technique. I like to shoot for an AFR and hit it right before Peak Torque and hold it till about redline. You need the most amount of fuel at peak torque because this is where your engine load is the highest and also where knock is most prone to start and occur. Obviously this is not the only place it can occur though.
At crusing loads I shoot for somewhere between stoichiometric (14.7:1 .... its actually more like 14.6 now days with the additives in our gasoline) and 15.5:1. By cruising loads I mean between 20 and 50 KPa (kilo pascals). Between these loads and under them, although you will rarely see under 20 KPa except for decel, you can truly run the car much leaner than stoich, even to the point where the car is audibly pinging and almost not enought fuel to keep the car running without much worry about engine damage. The reason being is that there is no real engine load at these conditions. (Obviously timing needs to be set accordingly)
At atmospheric pressure ( right around 100 KPa depending on elevation) I shoot for 12.5:1 AFR. In general this is the Max load a Naturally Aspirated engine sees.
Research has shown that an 4-stroke gasoline combustion engine will make the most power between 12:1 and 13:1 AFR. But as all of you seem to know, we run richer than this on turbo cars. The reason we do this is for the thermal management of our engines. Adiabatic Flame Temperatures (think of it as cylinder temperatures) are the hottest at a stoichiometric AFR. On either side of stoich, whether it is richer or leaner, flame temperature is cooler.
From cruise loads to atmospheric pressure I taper from stoich to this 12.5:1 AFR.
As an engine comes onto boost I progressively richen the car to my target just before peak torque and hold it at this AFR depending on the characteristics of the particular engine.
*If the car hits peak torque and holds that torque through redline, I hold my target AFR and possibly richen it up a bit to redline. (Ex: bigger turbo in its efficiency range)
*If the car hits peak torque and immediately begins to drop and continues to do so, I will sometimes begin to lean the car back out a bit to redline. (Ex: small turbo out of its efficiency range)
Again, it really depends on the engines setup and characteristics.
It is important to remember that as RPM goes up, Load goes down. This happens on both NA and FI engines and is because as RPM does go up, there is less time for the cylinders to fill with air. By 10,000 Rpm the intake valves are open for an incredibly short period of time, its a wonder that the air actually has time to move! Thank God for pressure differentials!
One last thing.... and one of the reasons it is so hard to just say "Use This:". It is completely possible to make the same amount of torque (and hp, which is related to torque by an algebraic equation) at a given Load and RPM with a fairly wide range of AFR's. Timing does "create power" as some have said, but only to the extent of maximizing it for a given AFR. At a given Load and RPM, I can be on the dyno and make XXX lbft at an AFR of 11.7 and 17 degrees advance, then richen the AFR up to 10.2 and use 23 degrees advance and make the same amount of torque. (The mentioned numbers are just an example to get the point across)
So to say use this AFR is really pointless if you know what you are doing, and the AFR you choose is within the window where the car will make the most power, and you optimize your timing accordingly. Too much timing advance without enough fuel will cause irregular combustion (detonation) and if there is enough fuel, too much timing can cause pressures to be so high before TDC that the piston is actually having a hard time moving up. Too little timing (or to much retard) can cause EGT to become extremely high. Timing greatly effects EGT's.
Just thought I would share some info.
Leaner fueling does not equal more HP necessarily. I think of Fuel as thermal management of the combustion process. I try not to think of fuel as a way to get more power as is commonly believed. What you want to do is start out on the rich side of where you believe your engine wants to run, and lean your mixture till you come into the "window" of proper fueling. You need to be able to measure power output while your adjusting your fueling so you'll know when you have the correct fueling for your engine. It's a bell curve and you want to be on the rich side of the bell (Rich Best Torque). You do the same thing for timing, start on the conservative side and add timing till you hit peak power and then back off - obviously this is all more tricky with knock limited fuels.
Example
AFR DYNO POWER OUTPUT
7.0:1 95 may misfire from being too rich
9.0:1 98
10.0:1 105
10.5:1 110
11.0:1 125
11.5:1 128
12.0:1 130
12.5:1 132 Rich Best Torque
13.0:1 132
13.5:1 131
14.5:1 130
15.0:1 125
16.0:1 120
18.0:1 110
19.0:1 100
20.0:1 95 misfiring from being too lean
Note: the window from about 11:1 - 15:1 power stayed roughly about the same, give or take ~7 hp. Which engine do you think will last longer? hint 11.1
So based on the example I would say for this engine's RBT is at 12.5:1. . I made this example up for the sake of explaining proper fueling but you get the idea. Once you tune your fuel, then you tune your timing. Obviously, you may have to revisit fueling after adjusting ignition timing as well. Also when tuning on higher boost, lower octane fuels, or pushing things to the edge, your "window" of proper fueling / ignition timing narrows.
My engine likes 12.2 at spoolup, quickly to 11.5:1 tapering to 11.1:1 at redline with a 25psi spike tapering to 19-20psi.
Why do the OEM's tune cars to run pig rich 9:1 AFR? Richer mixtures burn cooler and equal cooler combustion chamber temps. Cooler combustion temps = engine longevity.
Example
AFR DYNO POWER OUTPUT
7.0:1 95 may misfire from being too rich
9.0:1 98
10.0:1 105
10.5:1 110
11.0:1 125
11.5:1 128
12.0:1 130
12.5:1 132 Rich Best Torque
13.0:1 132
13.5:1 131
14.5:1 130
15.0:1 125
16.0:1 120
18.0:1 110
19.0:1 100
20.0:1 95 misfiring from being too lean
Note: the window from about 11:1 - 15:1 power stayed roughly about the same, give or take ~7 hp. Which engine do you think will last longer? hint 11.1
So based on the example I would say for this engine's RBT is at 12.5:1. . I made this example up for the sake of explaining proper fueling but you get the idea. Once you tune your fuel, then you tune your timing. Obviously, you may have to revisit fueling after adjusting ignition timing as well. Also when tuning on higher boost, lower octane fuels, or pushing things to the edge, your "window" of proper fueling / ignition timing narrows.
My engine likes 12.2 at spoolup, quickly to 11.5:1 tapering to 11.1:1 at redline with a 25psi spike tapering to 19-20psi.
Why do the OEM's tune cars to run pig rich 9:1 AFR? Richer mixtures burn cooler and equal cooler combustion chamber temps. Cooler combustion temps = engine longevity.
Last edited by Mr. Evo IX; Apr 30, 2008 at 09:50 AM.
Apr 30, 2008, 11:55 AM
#41
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so let me see if i understand this you are saying that 10.9 logged from a wbo2 is good for a tuned evo 8? if so i hope and pray you will never tune another evo. last time i checked the accepted and proven afr is 12.0 at spool and 11.5 to redline for maximum power. 10.9 idk wat to even say to that.
Apr 30, 2008, 02:57 PM
#42
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On a *Properly* tuned car, the 10.9 AFR car at redline will last just as long as the car tuned to 11.5 AFR at redline, all other things aside.
I am not so sure as to why people think that a riched AFR means a car will last longer.
Apr 30, 2008, 07:03 PM
#43
Optimal tune I have found on my car was about 23.5 tapering to 20.5 and the AFR was 12.5 spoolup 11.8 peak tq and 11.5 at redline. Timing was not that high and egts were still under 950*C. This was done in 100* temps and the intake temps were about110*.
Apr 30, 2008, 07:15 PM
#44
I agree with 12.5 at spool-up, 11.8 at peak boost/torque, but I do not agree with 11.5 by redline. I will never go higher than 11:1 AFR by redline on 91 octane gas. Nor would I run more than 18-19 psi AVERAGE boost (ie average of 3-4 runs) by redline on 91 octane. You need to build a margin of safety in a tune. To each there own, however.
