Just wondering if anyone is using a MSD DIS-2 6212 w/ a map sensor refference to retard stock timing and run a leaner 12.5-13.0 A/F???
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Quote: Originally Posted by Bell Intercoolers
Regardless of the [Thermal] efficiency, if too much pressure is lost, then the intercooler is either useless or can actually decrease performance...Corky Bell
Just wondering if anyone is using a MSD DIS-2 6212 w/ a map sensor refference to retard stock timing and run a leaner 12.5-13.0 A/F???
Hello!
Just a question, why would you want to run that lean of a mixture on a boosted engine? The A/F range you are talking about would be ok on a NA car, but not an SRT-4 or any boosted engine for that matter.
Not trying to bash you or stir the pot, but I think someone has pointed you in the wrong direction as far as tuning goes. I just do not want your engine to let go on you my friend.
good luck
Chris Macellaro
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Macellaro's Performance Tuning
EFI University Instructor
Just wondering if anyone is using a MSD DIS-2 6212 w/ a map sensor refference to retard stock timing and run a leaner 12.5-13.0 A/F???
why would u wanna retard the timin on stock turbo.. that is where makes it power... why u think toys help out so much... most peeps are using meth to advice and keep timing.. you are trying to retard it... that is just retarted.
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No one has pointed me anywhere. I've drawn my own conclusions.
You have to ask yourself whats the goal to optimizing timing. Its simply to "time" the peak cylinder pressure to about 10 ATDC. Max burn speed occurs with a A/F bewtween 12.5-13.0 regardless of wether its N/A or not. The thought that a boosted engine needs a particular A/F is incorrect.
Fact: supercharging increases the burn rate which requires a retard ignition event to optimize the peak cylinder occurance back to ~10 ATDC.
Fact: Over rich mixtures burn much slower
Fact: Over rich mixtures need advanced timing to make any power
So the thinking is, for a given octane and a set A/F(12.5-13.1) along with a "matching" or "properly timed" ignition event that gives the best BMEP.
Retard the timing and lean the mix for a higher BMEP, instead of over-enriching the mixture and an over advanced timing to get a lower overall BMEP.
Bottom line:
First off: i wish a had a EMS so all this mickey-mouse games wouldn't be needed.
I'm looking into retarding the timing while leaning the A/F. This is nothing new really. Consider it a rediscovered practice.
I'll have to defer defending the argument to Klause. He explains things better than I do.
Quote:
The problem is that rich mixtures burn slower and with less energy. Technically this is not cooling. It's just less energy release, which means you don't get the power out of the fuel that you could get.
If you are, for example, putting a N/A engine into a pressure chamber and raise the pressure to 14.7 pounds over atmospheric, by the boost = richer theory the engine now would have to run rich like many people tune turbos. But it's still a N/A engine.Same if you raise compression ratio on a n/a. Raising that increases the peak temperature at begin of combustion, and increases the mixture density at begin of combustion. Nobody I know of has ever suggested that a high compression n/a engine has to run very rich.
The conditions on a fi engine at beginning of combustion are very similar to a high compression engine in regards to how the combustion progresses. Except it has typically less swirl and lower compression caused temps because part of the heat-rise due to compression is taken out by the intercooler. Otherwise, the intake and exhaust valves are closed at that time. The behaviour of the gas in the comb. chamber is just determined by it's temperature, pressure and amount of swirl. How it got there is irrelevant.
Also, don't forget the time factor. Most of the research on these research engines is done at relatively low RPM (<2000 typically). Knock precursor chemistry is not instant, but takes time to occur. At higher RPMs, where boost typically comes on, there's less time for these to form. But running rich compensates for that somewhat because more fuel burning slower (but with more advance) gives more time for that chemistry.
I read on another forum where a guy actually took the advice on these articles. He ran a boosted Honda engine that needed to run at 10 AFR to prevent knock at his boost level. He run it up to 12.5 AFR, way retarded to start out and slowly advanced timing for MBT, but still way retarded from where he was originally. He gained ~12 hp on the dyno while the engine ran cooler.
Regards,
Klaus
No one has pointed me anywhere. I've drawn my own conclusions.
You have to ask yourself whats the goal to optimizing timing. Its simply to "time" the peak cylinder pressure to about 10 ATDC. Max cylinder pressure occurs with a A/F bewtween 12.5-13.0 regardless of wether its N/A or not. The thought that a boosted engine needs a particular A/F is incorrect.
Fact: supercharging increases the burn rate which requires a retard ignition event to optimize the peak cylinder occurance back to ~10 ATDC.
Fact: Over rich mixtures burn much slower
Fact: Over rich mixtures need advanced timing to make any power
So the thinking is, for a given octane and a set A/F(12.5-13.1) along with a "matching" or "properly timed" ignition event that gives the best BMEP.
Retard the timing and lean the mix for a higher BMEP, instead of over-enriching the mixture and an over advanced timing to get a lower overall BMEP.
Bottom line:
First off: i wish a had a EMS so all this mickey-mouse games wouldn't be needed.
I'm looking into retarding the timing while leaning the A/F. This is nothing new really. Consider it a rediscovered practice.
Very good sir! I actually like to read this forum when someone has more to offer than what everyone else is doing or what someone else has told them to do. All the points you made are right on target and would be the ideal tune for max power considering ATDC timing and A/F, although, I would stay closer to the 12.5 A/F for a small margin of safety.
Some of the members on the forum mostly know that advancing the timing leans out the A/F and increases power, which is true. This also confirms your point that "Over rich mixtures need advanced timing to make any power". The SRT-4 is overly rich and this is why it makes more power. BUT what the members need to realize is that this type tune is only good for a marginal amount of additional power before it becomes dangerous to the engine.
I also see a lot of members advancing the hell out of the timing and dumping more fuel in the combustion to compensate for an acceptable A/F. This is also an undesirable tune due to the slow and possibly erratic combustion burn.
I would like to see this thread go further than simply opinionated members bashing. Good luck with your tune.
Very good sir! I actually like to read this forum when someone has more to offer than what everyone else is doing or what someone else has told them to do. All the points you made are right on target and would be the ideal tune for max power considering ATDC timing and A/F, although, I would stay closer to the 12.5 A/F for a small margin of safety.
Some of the members on the forum mostly know that advancing the timing leans out the A/F and increases power, which is true. This also confirms your point that "Over rich mixtures need advanced timing to make any power". The SRT-4 is overly rich and this is why it makes more power. BUT what the members need to realize is that this type tune is only good for a marginal amount of additional power before it becomes dangerous to the engine.
I also see a lot of members advancing the hell out of the timing and dumping more fuel in the combustion to compensate for an acceptable A/F. This is also an undesirable tune due to the slow and possibly erratic combustion burn.
I would like to see this thread go further than simply opinionated members bashing. Good luck with your tune.
Yeah there's a lot of "the blind leading the blind" around here (Chris Macellaro excluded, I respect his opinion, although we disagree here)
With the stock timing being "unadjustable" for the most part, there's not many options but to run over rich with more boost. Sans an EMS, i was just thinking the MSD box might be an option.
Last edited by duster360 : 03-14-2007 at 08:14 AM.
-1: find a decent chassis dyno in area to get a baseline
0: get a DIS-2 6212 wire to map sensor
1: Start timing way retarded 6-10 degrees from its current max.
2: Lean A/F incrementally to around 12.5:1
3: reduce the amount of retard(advance timing) 1 degree, while monitoring knock, up to the MBT (best minimum timing)
4: dyno to evaluate changes
duster, I was going to respond to the above posts, when I noticed this post.
Simple question... Have you ever done this before, honestly?
And I would like to see proof if possible. If you tune a force inducted engine to 12.5:1 to 13.0:1 you will vastly shorten the life of your engine. A/F mixtures are a matter of thermal management.
People, please do not tune your SRT-4 engines to 12.5:1 to 13.0:1.
If you do not believe me.... please come to one of my classes.
I will address this later, my 10 month old daughter just started crying. When I have more time I will come back guys.
-1: find a decent chassis dyno in area to get a baseline
0: get a DIS-2 6212 wire to map sensor
1: Start timing way retarded 6-10 degrees from its current max.
2: Lean A/F incrementally to around 12.5:1
3: reduce the amount of retard(advance timing) 1 degree, while monitoring knock, up to the MBT (best minimum timing)
4: dyno to evaluate changes
duster, I was going to respond to the above posts, when I noticed this post.
Simple question... Have you ever done this before, honestly?
And I would like to see proof if possible. If you tune a force inducted engine to 12.5:1 to 13.0:1 you will vastly shorten the life of your engine. A/F mixtures are a matter of thermal management.
People, please do not tune your SRT-4 engines to 12.5:1 to 13.0:1.
If you do not believe me.... please come to one of my classes.
I will address this later, my 10 month old daughter just started crying. When I have more time I will come back guys.
Chris Macellaro
In this specific application no, I have not(only had the car 6 months). I have tuned several N/A motors but none were boosted apps. But there's no difference, as i see it, in the methodolgy, as one or two were pretty high static compression ratio but wanted to be able to run on pump fuel too. With that said, I'm used to more flexibilty in tuning also as all the others used standalone efi systems, so fighting against the ecu might be a bigger issue than i think.
Chris I know what you're getting at. Tuning in this way is all dependant on the octane of the fuel availible, of course. I realize MBT w/ 12.5:1 may not be possible for a pump octane and will be limited by knock so a comprise in A/F might be best. So in the end, I might wind up, for this engine and boost lvl with an A/F of 11.5 w/ 30 degrees of timing for 93 octane. But if 110 octane fuel is use a leaner mix should be the goal before advancing the timing to a new MBT to match the better detonation lvl of the higher octane fuel.
My main argument is over-enriching JUST to get the most timing advance is a ass-backwards way to tune.
The closest A/F to 12.5-13.1 you can get with the minimum best timing but still avoid detonation is the way to go.
Last edited by duster360 : 03-14-2007 at 12:19 PM.
If you do not believe me.... please come to one of my classes.
Chris Macellaro
I'm no dumby so don't assume I haven't thought this through.(BS Mech Egineering, ASE cert in Engine Performance) I always wanted to go to one of Ben's classes. I've tuned less than a dozen cars so im not naive enough to think i don't have more to learn.
I going to see about getting into the Naperville,IL 101 class May 5-6. I have to go to Chicago for Pro-e training anyway. I'll see if i can get the training scheduled the same week.
Last edited by duster360 : 03-14-2007 at 01:56 PM.
lol, Thanks for the vote of confidence SpeedEuphoria!!!
The argument behind it is sound.
Example. Two engines of the same cid Tuned by "Rickey Racer"
One engine is high compression the other low compression but turbocharged.
AIT same
Octane of fuel is equal Dynamic compression pressure is equal between the two
Rickey knows that the correct A/R for best power is 13.0:1. So he tunes the N/A engine to a proper 12.5-13.0 A/R at WOT and adjust timing to get the the best torque with any detonation.
With the other engine, Rickey decided to take all the advice of the tuning "geniuses" on his favorite internet forum, and tuned the turbo car to 11.0:1 for no other reason that "turbo cars like to run rich" and/or to get as much timing advance as possible.
Does it make any sense to you that the tuning methodology between the two engines would be any different? It doesn't to me.
Last edited by duster360 : 03-16-2007 at 08:12 AM.
Does it make any sense to you that the tuning methodology between the two engines would be any different? It doesn't to me.
It does to me. The boosted engine starts it's combustion process with compressed air in the chamber at BDC. The N/A motor does not. You're not seeing the whole picture, and your examples of power increases don't accurately display the whole picture. Sure the Honda gained some power. Doesn't mean it was the most it could have gained. I've seen similar tune-ups, and they have never been optimal.
Go back to the root of how an engine makes power. It burns fuel during a timed combustion event. The more fuel you can burn within that event, the more power you can make. I'm over-simplifying, but there are a lot of other factors going on at the same time that contribute to how much your ignition timing should be set at, including whether the engine sees boost or not.
The SRT comes programmed to run a little rich, doesn't have very agressive ignition timing, and uses small cams, because that is the best compromise for keeping the engine alive for the length of the warrantee. If you just retard the timing on one, it shoots flames out the back, and loses a little power. If you pull some fuel out on top of that, you get back some of that power. Maybe even gain some extra. If you could merely advance the timing without changing the stock fuel settings, it would gain even more power, since you would be burning more fuel. Too much and you get knock.
That's it in a nutshell. You're limited to the burn rate of the gas you're using.
Last edited by Specimen Kane : 03-17-2007 at 12:09 AM.
Who uses MSD DIS-2 6212 to retard timing???
Linear Mode
