Tuning Technical Point #2 Borderline Timing VS MBT Timing

[mattr66usa]

Yes.. in the simplified case where all else is equal, methanol’s faster effective burn rate tends to move MBT toward less advance (closer to TDC).

However, that trend only holds if exhaust backpressure, residual fraction, and effective VE are unchanged — which is not the case on stock-location, drive-pressure-limited turbo systems.

Given that methanol can simultaneously improve burn rate and alter exhaust energy, residuals, and drive pressure, how are you separating MBT changes caused by combustion chemistry from MBT changes caused by increased exhaust backpressure if turbine inlet pressure is not measured?

Since I think we have put the MBT timing topic to bed first (https://shoforum.com/threads/tuning-technical-point-1-what-is-mbt-timing.147778) Okay so now what is borderline timing in the Ford tuning universe?

 

[mattr66usa]

Let's make it a visual representation. Let's pull a spot of engine operation at about say 5500 rpms at a load of 1.65 and intake temperature of say 100 degrees running on 93 octane.

So the first graph is a snapshot at a single load/rpm point at WOT showing stockish calibration running on 93 octane.

The second chart is a base tune that has been optimized for 93 octane where the borderline knock is optimized at 93, but the knock sensors are allowed to add timing up to the MBT point at that operation area of the power curve as the cylinder pressure limit has been removed in this case. This is the case of the AO file where the borderline spark is already optimized for 93 when OAR is maxed and the knock sensors can add timing up to the MBT point.

The third graph is showing that the MBT timing spot is actually less timing than the gasoline MBT point.

So you can see from a timing standpoint, running at less than MBT timing is not any danger to the engine because the engine is almost always operating at less than its MBT point at wot unless you are on race gas or ethanol/methanol. MBT can be considered a "timing ceiling" if you aren't using the cylinder pressure table to cap timing. So from a timing perspective, you can either add the timing in manually where the methanol will be running or give the knock sensors authority and extra speed to add timing up to the chosen MBT point. The latter is the "safer" way to do it since if the meth isn't flowing properly, the engine's base spark won't be over-timed.



Now are there any questions on this?

 

[TheRedBeardedFury]

The second chart is a base tune that has been optimized for 93 octane where the borderline knock is optimized at 93, but the knock sensors are allowed to add timing up to the MBT point at that operation area of the power curve as the cylinder pressure limit has been removed in this case. This is the case of the AO file where the borderline spark is already optimized for 93 when OAR is maxed and the knock sensors can add timing up to the MBT point.

So here you have removed the pressure limit ford has placed and it comes down to knock sensor to add/remove timing up to the limit of mbt. In this case your unlikely to hit mbt point before knock comes into play right? Here knock is your limit and will start pulling timing.

The third graph is showing that the MBT timing spot is actually less timing than the gasoline MBT point.

So you can see from a timing standpoint, running at less than MBT timing is not any danger to the engine because the engine is almost always operating at less than its MBT point at wot unless you are on race gas or ethanol/methanol. MBT can be considered a "timing ceiling" if you aren't using the cylinder pressure table to cap timing. So from a timing perspective, you can either add the timing in manually where the methanol will be running or give the knock sensors authority and extra speed to add timing up to the chosen MBT point. The latter is the "safer" way to do it since if the meth isn't flowing properly, the engine's base spark won't be over-timed.

Once higher octane or meth is added to reduce the knock from pulling time you can get closer to mbt limit that's been set. In this case I would agree to lean on the knock to adjust timing vs doing it manually for the safety of meth not to flow and be overtimed without it.

 

[mattr66usa]

So here you have removed the pressure limit ford has placed and it comes down to knock sensor to add/remove timing up to the limit of mbt. In this case your unlikely to hit mbt point before knock comes into play right? Here knock is your limit and will start pulling timing.

That is correct. IMO Ford used the cylinder pressure limit to not let the timing get out of control in the factory calibration in cold weather etc and was an easy way to cap things for other reasons. I still use that table heavily to prevent torque spikes below 4000 rpms, so even if all the octane in the world was available, a normal calibration will not run at MBT timing below 4000 rpms (at WOT).

Once higher octane or meth is added to reduce the knock from pulling time you can get closer to mbt limit that's been set. In this case I would agree to lean on the knock to adjust timing vs doing it manually for the safety of meth not to flow and be overtimed without it.

That's how I feel about it and why I chose to do it that way. The knock sensors are very sensitive and do their jobs well on these cars.

I added the Methanol MBT line to show that the optimum timing of methanol is actually closer to the stock borderline timing than gasoline.

Now, on some vehicle applications, the factory MBT maps are set a little bit too low. I've especially found this on the 17+ raptors on E30 (which should have lower MBT than factory). Normally if at the 500-600 whp level, a degree of timing added only adds 2-3 HP, I stop because it is approaching MBT timing. I've seen 10 HP with a degree of timing on the gen 2 at high rpm going past the factory tables, so I do bump MBT tables in that case.

Now I'll concede that if we were running total Methanol by itself, it would make more power than gasoline even both at MBT timing somewhere in the neighborhood of 3-6%, but we are running a supplemental fuel system with major compromises, not total replacement. So if we were running 100% mix at 50% substitution we could make 2-3% more power at the same airflow, but I sure don't recommend putting that much liquid down the intake manifold for starters.

 

[TheRedBeardedFury]

That's how I feel about it and why I chose to do it that way. The knock sensors are very sensitive and do their jobs well on these cars.

Given this information what would happen if you where overtimed from meth not flowing? If we relied on the meth flow vs the knock sensor is there any power gained from this way or just a safety risk? We know the lambda and fuel correction is done in pretty much real time. If we relied on knock for timing it is also done in real time right? With the only adjust having to be done if knock is detected?

I added the Methanol MBT line to show that the optimum timing of methanol is actually closer to the stock borderline timing than gasoline.

Now, on some vehicle applications, the factory MBT maps are set a little bit too low. I've especially found this on the 17+ raptors on E30 (which should have lower MBT than factory). Normally if at the 500-600 whp level, a degree of timing added only adds 2-3 HP, I stop because it is approaching MBT timing. I've seen 10 HP with a degree of timing on the gen 2 at high rpm going past the factory tables, so I do bump MBT tables in that case.

I find this reasonable as I don't see a gain of 2-3 HP being worth it in this case. Would like to point out you test this within logging and adjust with revisions correct?

Now I'll concede that if we were running total Methanol by itself, it would make more power than gasoline even both at MBT timing somewhere in the neighborhood of 3-6%, but we are running a supplemental fuel system with major compromises, not total replacement. So if we were running 100% mix at 50% substitution we could make 2-3% more power at the same airflow, but I sure don't recommend putting that much liquid down the intake manifold for starters.

Okay then where not talking huge gains then in this case. Huge risks with little gains correct? Will we touch on the cleaning benefit to using meth at some point?

 

[mattr66usa]

Given this information what would happen if you where overtimed from meth not flowing? If we relied on the meth flow vs the knock sensor is there any power gained from this way or just a safety risk? We know the lambda and fuel correction is done in pretty much real time. If we relied on knock for timing it is also done in real time right? With the only adjust having to be done if knock is detected?

In the case the mentanol isn't flowing properly, the care may need to pull 5 degrees very rapidly and that isn't a good thing. That's why I PREFER to set them up the way I do so that the knock sensors are adding timing between the borderline and MBT timing numbers. But yes this would give instant optimum timing at launch if set up to be meth dependent.

Also if the octane is bad there is some lag time when you go wot until the timing reaches the maximum power output. 2-4 seconds is typical to get to MBT if the timing starts 5-6 degrees lower than optimum. The 13+ SHO tunes are on their 792nd revision. It was a chore to get all the timing tables across all the mapped points to be uniform and allow for the dynamic timing adjustments to work properly at WOT. On E30, the timing is pretty much already set at MBT so there wouldn't really be any more timing added with the meth flowing, so in that case, the methanol is there for extra octane margin and cooling. This is why some people get confused and say we only use methanol for cooling.

I find this reasonable as I don't see a gain of 2-3 HP being worth it in this case. Would like to point out you test this within logging and adjust with revisions correct?

Gains are gains, some of us chase every little hundreth, some just want a fun ride that doesn't run the risk of tearing stuff up. I try and ask every customer what the goals are and take it to that point. Yes and for the most part on a stock car or a car with normal mods, the base tune is usually 99% where it should be, and I don't need to make changes. I do feel like with the way I tune these cars, from the outside looking in, it may seem like GH is a one and done operation, but in reality I always recommend looking at datalogs after the customer drives for a few days just in case the car isn't acting correctly.

Okay then where not talking huge gains then in this case. Huge risks with little gains correct? Will we touch on the cleaning benefit to using meth at some point?

Don't go there as you will now have me labeled as "meth is only for cleaning if Gearhead is tuning" moniker... LOL But yes, the methanol helps get rid of the oil coking up on the valves that is super common on these engines.

 

[TheRedBeardedFury]

In the case the mentanol isn't flowing properly, the care may need to pull 5 degrees very rapidly and that isn't a good thing. That's why I PREFER to set them up the way I do so that the knock sensors are adding timing between the borderline and MBT timing numbers. But yes this would give instant optimum timing at launch if set up to be meth dependent.

Also if the octane is bad there is some lag time when you go wot until the timing reaches the maximum power output. 2-4 seconds is typical to get to MBT if the timing starts 5-6 degrees lower than optimum. The 13+ SHO tunes are on their 792nd revision. It was a chore to get all the timing tables across all the mapped points to be uniform and allow for the dynamic timing adjustments to work properly at WOT. On E30, the timing is pretty much already set at MBT so there wouldn't really be any more timing added with the meth flowing, so in that case, the methanol is there for extra octane margin and cooling. This is why some people get confused and say we only use methanol for cooling.

Me personally I believe I would prefer your way as well. Given at worst case it would only take 2-4 second to reach maximum power and still have the safety net. Gezzz 792 revisions is wild lol.

Gains are gains, some of us chase every little hundreth, some just want a fun ride that doesn't run the risk of tearing stuff up. I try and ask every customer what the goals are and take it to that point. Yes and for the most part on a stock car or a car with normal mods, the base tune is usually 99% where it should be, and I don't need to make changes. I do feel like with the way I tune these cars, from the outside looking in, it may seem like GH is a one and done operation, but in reality I always recommend looking at datalogs after the customer drives for a few days just in case the car isn't acting correctly.

So for a customer that's wanting every gain possible and doesn't care for the safety you will still tune for them after informing them? With 792 revision I'm sure it's pretty dialed in. So when someone buys a tune from you it's pretty dialed in so all that is required of them is to put miles on it and then pull a log for you to verify. At this point tune is good or you will make the adjustments for there specific setup or wants. Rinse and repeat until both is satisfied.

Don't go there as you will now have me labeled as "meth is only for cleaning if Gearhead is tuning" moniker... LOL But yes, the methanol helps get rid of the oil coking up on the valves that is super common on these engines.

Well the reality of meth is even if your on a "baby" spray there are more benefits then just cooling. With this said are there more benefits of spraying others then cooling, cleaning, helping octane, and keeping from running out of fuel rail pressure?

 

[mattr66usa]

So for a customer that's wanting every gain possible and doesn't care for the safety you will still tune for them after informing them?

Yes, but I don't do it often because I feel responsible if things go badly even if I warned them

With 792 revision I'm sure it's pretty dialed in. So when someone buys a tune from you it's pretty dialed in so all that is required of them is to put miles on it and then pull a log for you to verify. At this point tune is good or you will make the adjustments for there specific setup or wants. Rinse and repeat until both is satisfied.

I have customers that don't want any changes, I have some that need the 2-3 shift tweaked once in a while to not shift too early because the 2-3 needs to shift above 6000 RPM because the drop is so large that you get out of the "sweet spot" of the power curve. the 3-4 needs to happen much sooner because the gear spilt is much closer and doesn't drop the rpms so hard. Very seldom i need to turn boost down because the fuel pump can't keep up with the base tune even.... Stuff like that. Sometimes we are chasing false knock. Sometimes we have an engine with heavy carbon fouling that won't tolerate spark. I've even seen oil brand and length of time on an oil change have an effect on knock at wot. It's crazy.

Well the reality of meth is even if your on a "baby" spray there are more benefits then just cooling. With this said are there more benefits of spraying others then cooling, cleaning, helping octane, and keeping from running out of fuel rail pressure?

I like methanol. I just don't always trust it and try to take precautions.

 

[TheRedBeardedFury]

Yes, but I don't do it often because I feel responsible if things go badly even if I warned them

I get this!

I have customers that don't want any changes, I have some that need the 2-3 shift tweaked once in a while to not shift too early because the 2-3 needs to shift above 6000 RPM because the drop is so large that you get out of the "sweet spot" of the power curve. the 3-4 needs to happen much sooner because the gear spilt is much closer and doesn't drop the rpms so hard. Very seldom i need to turn boost down because the fuel pump can't keep up with the base tune even.... Stuff like that. Sometimes we are chasing false knock. Sometimes we have an engine with heavy carbon fouling that won't tolerate spark. I've even seen oil brand and length of time on an oil change have an effect on knock at wot. It's crazy.

Yeah I can understand different issues coming along. I'm trying to figure out a new knock issue on mine now too. It's driving me nuts . I don't think a lot of people realize how much the tuner can tell when looking at logs. Especially when chasing an issue. How many people actually come back after having the tune a little while for help figuring out a newly developed issue? Not implying an issue from the tune itself but like sensor issues or routine stuff?

I like methanol. I just don't always trust it and try to take precautions.

If it wasn't for the trust issues I'd be more interested in running it myself.

 

[mattr66usa]

Yeah I can understand different issues coming along. I'm trying to figure out a new knock issue on mine now too. It's driving me nuts . I don't think a lot of people realize how much the tuner can tell when looking at logs. Especially when chasing an issue. How many people actually come back after having the tune a little while for help figuring out a newly developed issue? Not implying an issue from the tune itself but like sensor issues or routine stuff?

Usually the customer blames the tuner no matter what.... LOL But there a lot of things that can cause false knock.

 

[TheRedBeardedFury]

Usually the customer blames the tuner no matter what.... LOL But there a lot of things that can cause false knock.

Oooof that's off putting im sure. It's really beneficial to be able to somewhat read logs and understand it when looking for issues or causes. Working with the tuner who's seen hundreds of the same logs would be smart not working against them . Yeah there's so many things for false knock it might be the worst thing to chase lol.

 

[mattr66usa]

So to sum things up. MBT timing is above the borderline timing for pump gas meaning you can't run at MBT timing because of lack of octane. E30-40 (depending on base fuel) gets you to full MBT as well as methanol injection 70-100% at a 10-20% substitution ratio (again depending on base fuel) on a 100% direct injection car like the SHO (need more on a split injection vehicle like a gen 2 EcoBoost). The MBT for alcohols (either ethanol or methanol injection) is slightly less than the MBT for race fuel.

If you aren't running at MBT you aren't running at maximum power, but there is no damage to anything, other than you aren't taking advantage of the power available. Having timing "pre-adjusted" for the high octane makes the most power instantly, but if you don't have the octane available, your knock sensors will have to pull all the timing back very quickly an in that time you can do damage to the engine in some cases. The way GH sets the tunes up, on pump gas plus methanol, you start at the timing for pump gas and creep up on the MBT timing over a 2-4 second period (depending on rpm) and it holds that added timing throughout the entire time at wot.

On E30-E40 the timing is already at the MBT point even if you stack alcohol on top of it. Maybe this is where the confusion lies when people say we don't tune for methanol injection. If this is the case, the customer can decide to use the methanol to support additional airflow (raises boost) that normally wouldn't be supported on the fuel system they have because of lack of flow. In the case of more boost, we call this a meth dependent tune because without the methanol flowing, fuel pressure would drop.

Also, all the fancy stuff with torque modeling etc is handle by the computer. In the event of more timing, the computer adds more torque to the calculation. Whether timing is added via the IAT2 temp dropping when the methanol comes on, the knock sensors adding the timing automatically, or it is "tuned for it" as some are saying, the torque being reported by the calculation rises and everything is happy. The torque model doesn't care what factor is adding the timing. The fueling side of things isn't for this topic, but I expected more responses on this topic first. There is lot of "topic mixing" going on, so I am attempting to distill everything down so we can go from the ground back up to the total end result.

Merry Christmas,
Matt