Technical Timing vs PSI

[SlowE93]

At what point is it better to have cleaner timing vs psi ? I have seen logs of say 27 psi and timing drops of say 4° on a few cylinders. Would say 24 psi and perfect or near perfect timing make more power ? I would think zero timing pulls would be safer, but from a power perspective, what would be stronger ? Or get you down the track faster.

 

[Hydra Performance]

I guess 60-130/100-200 pulls on a Vbox/Dragy would be the best way to answer your question above

 

[langsbr]

I would think the 27psi with a few cylinder drops would make more power than 24 and perfect. I think @suspenceful had a couple 1/4 mile passes posted recently and the cleaner pass timing wise didn't make that much difference. Granted, if you are dropping in all cylinders I could see a major reduction, but isn't the 'generally accepted principle' that it's better to add a pound of boost at lower timing than to add more timing?

As hydra said, the best way is by testing. Hard to simulate the timing drops though. I would also ask, why are you getting the timing drops? Random undiagnosed, or is it octane limitation? That would help determine what would make more power too.

 

[SlowE93]

Straight E85 scenario. I run my car on 26. I CAN pull a perfect 3rd gear log. Not every time though. This is just a random question to discuss. So lets use my car as an example. Down to 23 psi I can pull a perfect log 99% of the time. 3rd gear or running through the gears. I run 25 or 26 psi and can pull a perfect log maybe 70% of the time. I have not tried 27 psi or greater. Assuming I did and could never get a perfect log at that point. Would I still be making more power ?

 

[SlowE93]

I would think the 27psi with a few cylinder drops would make more power than 24 and perfect. I think @suspenceful had a couple 1/4 mile passes posted recently and the cleaner pass timing wise didn't make that much difference. Granted, if you are dropping in all cylinders I could see a major reduction, but isn't the 'generally accepted principle' that it's better to add a pound of boost at lower timing than to add more timing?

As hydra said, the best way is by testing. Hard to simulate the timing drops though. I would also ask, why are you getting the timing drops? Random undiagnosed, or is it octane limitation? That would help determine what would make more power too.

I have also heard a lb of boost and less timing. Is that to make more power or to add safety and stress the motor less ? I guess what im asking is when is 1or 2° of timing more beneficial to 1 lb of boost.

 

[Rob09msport]

Boost stresses turbos more , timing is more dangerous for motor cause knock and cylinder pressure . However it's not that simple cause to much boost can fall out of compressor efficiency and spike iat. That's why experience on a platform is very important for e tune and why I don't tune myself. I would only attempt editing a good base map unless I was on a dyno in which case a good tuner will require less time then I would and also manipulate vanos and other variables that can net positive results. You want to run as much boost as you can with timing preferably right below mbt and with little to no corrections while still having good logs "afr in check ,iat not to high, wgdc not to high, fuel pressure and stft in check" that is a pretty safe bet for good power does it mean the most def not but will be close to it.

 

[Rob09msport]

7

Straight E85 scenario. I run my car on 26. I CAN pull a perfect 3rd gear log. Not every time though. This is just a random question to discuss. So lets use my car as an example. Down to 23 psi I can pull a perfect log 99% of the time. 3rd gear or running through the gears. I run 25 or 26 psi and can pull a perfect log maybe 70% of the time. I have not tried 27 psi or greater. Assuming I did and could never get a perfect log at that point. Would I still be making more power ?

Need to know what you consider perfect log as less then 3 degrees on random cylinder is no prob but if you are seeing pulls on 3 adjacent cylinders that is a knock event

 

[SlowE93]

Perfect meaning zero timing correction on any cylinder. This is with all else considered. HPFP, LPFP, iat, stft, AFR, etc in check.

 

[MoreBoost]

To get the answer to your question you either need to measure the torque on a dyno in each situation or the acceleration on a road. Otherwise we are just guessing.

 

[Rob09msport]

Can confidently say i would go with the 70 percent of time not one correction at all as most likely you are not losing and really aren't leaving much if any power on the table and sounds like your in good shape. For a track not dragstrip type application I would always go with the lower map aka where you have 0 corrections all the time

 

[glachhman]

Are timing pulls strictly and almost completely based solely on knock sensor feedback?

 

[BQTuning]

Are timing pulls strictly and almost completely based solely on knock sensor feedback?

No. There are timing corrections that are elaborate functions of the DME that are adaptive related, and ceiling related.

The best way to understand what is what is by studying on/off corrections vs knock sensor voltage. Not much people invest in R&D to do this so just read the cheat sheet for the basics.

https://blog.protuningfreaks.com/20...rrections-and-tuning-for-more-reliable-power/

Of course the goal is to strive to minimize as much timing corrections as possible. Keep in mind I didnt say zero(0) timing correction. This concept can lead down a very dark road

 

[Jeffman]

I remember reading that ProTuning Freaks article by Dzenno and friends from 2012 when it was first posted. Jake H did my first Cobb e-tune back then...

Before reading that article I remember being concerned about all of my timing corrections, especially under cruise conditions. So the article helped to allay my fears that something was wrong with my engine. But I believe (in retrospect) that the article is not so much a “cheat sheet” to understand the various conditions under which timing is altered, but rather is a palliative attempt to explain that we should trust the genius German engineers who finally crafted the N54 DME logic. Indeed, the article ends with, “If BMW’s own original tuning is allowed to have some timing corrections, well, we won’t pretend we can do it better than them.
Enjoy your N54s, some timing corrections are A-OK! ”

Now fast-forward six years later - we know so much more about the N54. In fact, @jyamona and Martial / MHD have been able to decompile and rewrite the engine control software, understand its logic, and include many new features, including interpolation of a number of tables to permit FlexFuel operation. We’ve come a long way since 2012 and I suspect we’ll be able to better understand and control timing corrections as the platform evolves.

 

[Rob09msport]

Are timing pulls strictly and almost completely based solely on knock sensor feedback? I have an annoying pull on #4, built motor. Pulls 7 degrees at 19psi or at 29psi. Straight e85, no other cylinder has any correction. With MHD box desensitized it's still pulling #4.

Built motors I know have had issues with false knock 7 degrees is a huge pull . I think you need to get on a dyno and listen for knock manually then you can adjust any false alarms with a Potentiometer or maybe someone who know more has better way but ya I wouldnt drive with a 7 degree pull cause if it's really an issue that's bad and if it's not that is alot of power down on that cylinder. I would think that can throw the whole motor out of balance, I'm sure it isnt good no matter what.

 

[iminhell1]

My fastest passes are on ZERO timing corrections.

Most all of the corrections i do get come from lack of HPFP pressure. I run just above 800psi most times. That doesn't leave me any room for error. I also can't run the AFR that I'd like to, or what I'd consider a safer ratio. I run leaner so i have to be on top of what's going on or kaboom.



You don't need a dyno or anything really to understand that power is pretty basic. It's derived from instantaneous tq and averaged tq.
The goal with averaged tq is the highest cylinder pressures over the longest rotation. When you pull 4* you'll loose power over quite a bit more than 4* of rotation, and this varies based on rpm. I don't have the math in front of me but I don't doubt that dropping 4* results in a loss of pressure over 15* of crank rotation at like 5,000rpm. And when you only have about 72* of crank rotation to make good power in ...

Then you can talk about the actual cylinder pressure. 3 psi of boost isn't going to change cylinder pressure at all. It's the added fuel and minimal air it brings with it that adds cyl pressure. The added fuel adds burn duration, averaged tq.
-- part of the reason WOT runs richer it to slow the burn and generate more tq over a longer rotation.




In a general sense, more timing less boost is a better scenario to making more power.
The problem becomes when you get near that MBT range with good fuel. How far past can you push before catastrophe.
err on the side of caution is the norm. Which is more boost and less timing. It's safer, but won't make as much power.

 

[Rob09msport]

Obviously if fuel is maxed then you are not going to be able to run as much timing or boost as you can and in that case timing will make more power but one thing I think you are mistaken on is pulling 4 degrees will lower cyl pressure for the entire stroke ,the plug is firing before tdc in either scenario you just may not burn as much fuel but also if you are at mbt then more timing will reduce power as you will be creating more resistance at the end of your compression stroke for no reason


Not to mention are really pushing your octane more than you have to for no gain actually if you talk to exp tuners usually last few points before mbt are diminishing returns

 

[SlowE93]

So im still a little confused. Problem is depending on weather, humidity, etc. logs can be perfect 1 min, then pull timing the next. Unless I drop to about 21/ 22 psi then logs are pretty consistent regardless of weather conditions or how hard I run the car. So how do you determine what is SAFE and consistent MAX power ? At 26 psi I can pull a perfect log with zero timing corrections and all else in check, but cant pull that log everyday. Sometimes timing even looks scary so I dropped back down to 24psi which is a little more consistent than 26, but as I said, I can every now and then pull a CLEAN log on 26.

 

[iminhell1]

So im still a little confused. Problem is depending on weather, humidity, etc. logs can be perfect 1 min, then pull timing the next. Unless I drop to about 21/ 22 psi then logs are pretty consistent regardless of weather conditions or how hard I run the car. So how do you determine what is SAFE and consistent MAX power ? At 26 psi I can pull a perfect log with zero timing corrections and all else in check, but cant pull that log everyday. Sometimes timing even looks scary so I dropped back down to 24psi which is a little more consistent than 26, but as I said, I can every now and then pull a CLEAN log on 26.

Do a GOOD leak test.
and maybe replace boost solenoids for good measure.

 

[Jeffman]

Weather will also play a factor, obviously. Not just heat leading to higher IATs, but also relative humidity.

 

[SlowE93]

Do a GOOD leak test.
and maybe replace boost solenoids for good measure.

Why ? Car performs well. Boost is always on target, ff is usually 100 or under. No signs of boost leak and everything is fresh. Solenoids, boots, connectors, fmic, tbolts, etc