Interesting dyno test (cats and boost)

[GregO]

@engineermike
Being I’m an old school Mikuni, Lectron, Crank Shop carb guy and been around standalone engine dynos is there no longer a use for BSFC ?
All this dialogue about Lambda, MBT, AFR, Mass air etc. and never do I see BSFC or BMEP…..

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[engineermike]

I think the lambda correction for borderline timing is an artifact of the MBTorque lambda relationship.....Hopefully you see and agree the borderline correction is mostly just an artifact of the MBT lambda correction applied over the RPM range. Not an actual representation of lambda effect on borderline at those RPMs like MBT lambda correction is.

If I'm understanding correctly, you are saying that the lambda borderline correction tracks with the MBT correction because the same phenomenon controls both. I tend to disagree because you have one main factor affecting MBT but two affecting Borderline. As you move lambda closer to optimum power, combustion becomes faster and MBT falls. Due to the faster combustion, Borderline can fall as well due to the higher cylinder pressure...but more often it rises due to the charge cooling effect and there is no dip to the rich side of stoich. The Predator cal seems to indicate that the lambda MBT and Borderline correction tracks with one another pretty closely, just as you appear to be stating. However, in other calibrations such as the Gen1 Coyote and Gen2 3.5 Ecoboost, the curves are very different, and Borderline gets a lot more "help" from lambda than it hurts MBT once richer than optimum power. The Gen3 Coyote is somewhere in the middle, as they start tracking one another well once richer than optimum power. I do wish that the MBT table had a load dimension though.

Same goes for the lambda effeciency correction on the torque tables.

Again, if I'm understanding correctly, you are saying the torque efficiency correction is merely a result of MBT changes and the resultant distance from MBT. As far as I know, the torque calculation accounts for timing by comparing actual to MBT then using the Spark Delta S-curve to find the timing torque correction multiplier, but uses the lambda efficiency correction multiplier on top of that. That is my best interpretation of the calibration unless I see some official documentation stating otherwise. I do believe torque will rise and fall as lambda changes even if you maintain MBT the whole time, which supports what I am saying.

You keep saying power lambda, Im sure you mean torque lambda. ...Power is just the product of RPM and the best torque curve.

When comparing at static rpm, power and torque are directly proportional to one another, so it is irrelevant which terminology you use. This is semantics and does not affect any results or conclusions. 1% change in one = 1% change in the other. And since we are all chasing power, I thought the typical reader would appreciate discussion of peak power numbers moreso than torque@rpm.

I also don't see how the rich side of this MBT plateau with increasing MBT is benefiting an engine thats detonation limited by gaining an extra degree of timing. The MBT is increasing there because of worsening combustion so the same "detonation limited" S curve rules don't apply. All engines running rich bog, NA coyotes do it, boosted coyotes do it. Very unlikely this bog is of lesser effect than the increase in detonation resistance the little extra fuel is giving it.

Again, if you plot Gen1 Coyote or Gen2 3.5 Ecoboost curves you'll see that the effect on MBT and Borderline is quite different. I did all the math and plotted all the curves for the Ecoboost example and found optimum power lambda, once distance from MBT was corrected for, and found optimum torque lambda to be .70, not the .86 where the lambda efficiency curve peaks. I shared this plot in an earlier post. Lo and behold, Ford commands 0.70 lambda when in Power Enrichment mode. I refuse to believe this to be a coincidence.

Lambda effect on detonation is not that great, its not like you gain a bunch more evaporation from .85 lambda to .75 lambda.

My own observations have been that running richer allows more timing. Ford seems to agree. From .85 to .75 lambda, the following are the increases in borderline timing:

Gen1 Coyote: 4.9
Gen3 Coyote: 2.1
GT500: 1.3
Gen2 Ecoboost: 2.6

Just to name a few. I guess "not that great" is subjective, but I when a degree is worth 20 hp, then I'm willing to dig there for more power.

...Pedicting anything out of a calibration assuming you will be detonation limited is not something you should be tring to do.

I'm not sure why you wouldn't use OEM calibration to help get you closer to a more accurate starting point, or to help explain an observed phenomenon.

I think the models and corrections around it are too general. If they ween't, there would be no need for the knock sensors and computer advance at this point with how many corections there are.

The way I see it is that the Borderline and MBT corrections are all as accurate as Ford can practically make them, so they have a more accurate starting point, as you said. However, they do not have a humidity sensor nor do they have control of the octane. These 2 things could affect borderline timing by 10 degrees. Since I've committed to 93 octane, then I've reduced that variability to about 4 deg, mostly affected by humidity. I had planned on using Knock Adaptive to help account for humidity, but it appears as though it's disabled in my strategy (open to suggestions). Anyway, I've found that aside from humidity, I can keep my engine very close to knock without actually experiencing knock in a wide variety of conditions. You might have noticed in an earlier post that this dyno session was done with 1.5 deg less timing than I can run at higher dew points. I've personally found that humidity can affect timing 2 deg, maybe 3 deg at my location. Up north where dew points can go negative, it can be much more. I've heard that some OEM's are moving to install humidity sensors and some may already have. I'm toying with the idea of adding one to mine so I can run closer to knock in even wider environmental variations.

You certainly shouldn't take the borderline lambda correction 6250rpm column and apply it to a 10* detonation limited scenario that would probably only occur at low much RPMs.

Nobody is doing this.

 

[engineermike]

U do a lot of tinkering, tuning and testing and I love your posts but imho it would be more interesting to see how it would've reacted to the stock GT cats vs no cats. The GT500 cats may have been the whole reason why you seen those results and like you said adding them can be a pita.

Perhaps. I have dyno'd on stock-ish cats (stockers with the convergent cones replaced with conical transitions and 3" piping. It was in the ballpark but at that time I was dyno'ing in 7th gear. Apparently, if you pull a dynojet to 170+ mph, the tire rolling resistance starts getting a vote and can mute the top end power. I'd say my stockers didn't affect power much but I also didn't have the 2.5" s-pipes or 2.25" factory connection.

But still in the end, if your tuning isnt spot on and any cat melts and bricks up on boost, BAD THINGS CAN HAPPEN real fast

In hindsite, I don't think melting is the primary failure mode. We aren't melting the ceramic at our exhaust temps. More likely it's thermal stress due to rapid, uneven heating. Many calibrations run low timing and lean lambda at low rpm, which is a recipe for sudden high EGT and thermal shock.

 

[engineermike]

... I have no idea what lambda and half of the other stuff mentioned even means ...

Lambda = Actual Air Fuel Ratio / Stoichiometric Air Fuel Ratio

It allows you to compare air/fuel ratio across different fuel types and ethanol contents.

 

[engineermike]

@engineermike
Being I’m an old school Mikuni, Lectron, Crank Shop carb guy and been around standalone engine dynos is there no longer a use for BSFC ?
All this dialogue about Lambda, MBT, AFR, Mass air etc. and never do I see BSFC or BMEP…..

I don't find much use for BSFC, but I definitely use BMEP and learned some fascinating things from it. When you get bored, start comparing BMEP vs compression ratio of OEM engines, both forced induction and naturally aspirated.

 

[markmurfie]

The only RPM, 1% change in torque = 1% change in power is 5252RPM.

And to keep this short, rev it to higher RPM if peak power is your goal. Both catted and FFE were still climbing in power. You may only see where the cats choke flow higher in the RPMs.

 

[Stymee]

Perhaps. I have dyno'd on stock-ish cats (stockers with the convergent cones replaced with conical transitions and 3" piping. It was in the ballpark but at that time I was dyno'ing in 7th gear. Apparently, if you pull a dynojet to 170+ mph, the tire rolling resistance starts getting a vote and can mute the top end power. I'd say my stockers didn't affect power much but I also didn't have the 2.5" s-pipes or 2.25" factory connection.



In hindsite, I don't think melting is the primary failure mode. We aren't melting the ceramic at our exhaust temps. More likely it's thermal stress due to rapid, uneven heating. Many calibrations run low timing and lean lambda at low rpm, which is a recipe for sudden high EGT and thermal shock.

But u wouldn’t disagree a clogged melted brick can be a common problem on a boosted setup and can be disastrous. So in the end, the safest boosted setups should run cat deletes for that very reason?

Again you have a lot of knowledge plus u monitor, tweek & test different ideas because of your mindset and I really enjoy your findings.

That said, Most guys don't, so imho if your the average guy building a street/strip setup you cant deny the most important things with boost are a very good fuel system, great tuning, a NON catted free flowing exhaust and very good fuel

Still though I find your post excellent, u seem to enjoy sharing your knowledge freely, I know your making great power safely and have backed it up with nice ET’s plus u have a real street car which makes it even better

 

[engineermike]

But u wouldn’t disagree a clogged melted brick can be a common problem on a boosted setup and can be disastrous. ..That said, Most guys don't, so imho if your the average guy building a street/strip setup you cant deny the most important things with boost are a very good fuel system, great tuning, a NON catted free flowing exhaust and very good fuel

It's no secret that the Gen3 Mustangs can make ridiculous safe power with E85 no cats. What can I say...I like to do things the hard way. Actually, I like having a daily driver that passes emissions and can be filled up anywhere yet still pull a 140 trap. As far as the cats go, in the majority of cases when the substrate starts to get cracks in it, you get a code before any engine damage is done. But as with many things, tuners make all the difference by disabling the SES light and not managing cat temp well which is a recipe for disaster. That said, I failed a few myself in the learning process.

So in the end, the safest boosted setups should run cat deletes for that very reason?

The safest boosted setup would be cat deletes, E85, FR OPG, forged pistons and rods, transmission, axles, etc....or just buy a GT500.

Again you have a lot of knowledge plus u monitor, tweek & test different ideas because of your mindset and I really enjoy your findings.

Still though I find your post excellent, u seem to enjoy sharing your knowledge freely, I know your making great power safely and have backed it up with nice ET’s plus u have a real street car which makes it even better

Thanks!

 

[Stymee]

It's no secret that the Gen3 Mustangs can make ridiculous safe power with E85 no cats. What can I say...I like to do things the hard way. Actually, I like having a daily driver that passes emissions and can be filled up anywhere yet still pull a 140 trap. As far as the cats go, in the majority of cases when the substrate starts to get cracks in it, you get a code before any engine damage is done. But as with many things, tuners make all the difference by disabling the SES light and not managing cat temp well which is a recipe for disaster. That said, I failed a few myself in the learning process.



The safest boosted setup would be cat deletes, E85, FR OPG, forged pistons and rods, transmission, axles, etc....or just buy a GT500.



Thanks!

Oh for sure. Forged bottom is the icing on the cake, hell even on a stocker opg’s are a smart idea for piece of mind

GT500 = WIN
Could u imagine a 10r80 in one

Yea we think a like, as I get older having a fast DD with emissions would be very important to me, and I live in Fl so if I wanted to go boost I could run no cats here but those days are over. Hell I’m driving a bone stock GT Convertible now and honestly all I’m gonna do to it is a axle back.

I’m done

Plus these EV’s are fast and I think thats gonna be the future for me, a mid 10 Sec EV looks very appealing and prices will come down soon

 

[Platinum_5.0]

As always, great testing and writeup, but I'll be honest, I'm more shocked over the fact that you are running 3.5 pulley (13-14psi) with 17* timing and only pump 93....lol...seems extremely aggressive. Am I missing something? lol

 

[engineermike]

As always, great testing and writeup, but I'll be honest, I'm more shocked over the fact that you are running 3.5 pulley (13-14psi) with 17* timing and only pump 93....lol...seems extremely aggressive. Am I missing something? lol

XDI gdi pump running 3500 psi pressure and low backpressure exhaust help with knock. I can actually run up to 18.5-19 deg timing on the 3.5 pulley when humidity is higher.

 

[illtal]

XDI gdi pump running 3500 psi pressure and low backpressure exhaust help with knock. I can actually run up to 18.5-19 deg timing on the 3.5 pulley when humidity is higher.

have you tuned any turbo cars?

 

[Platinum_5.0]

XDI gdi pump running 3500 psi pressure and low backpressure exhaust help with knock. I can actually run up to 18.5-19 deg timing on the 3.5 pulley when humidity is higher.

Crazy. I have actually went to a full 3' exhaust after the write up and testing you did. V-band from the headers to complete 3''. Maybe I need that gdi pump now lol

 

[illtal]

Crazy. I have actually went to a full 3' exhaust after the write up and testing you did. V-band from the headers to complete 3''. Maybe I need that gdi pump now lol

The tuning window gets larger with it.
I dunno how many of the tuners have actually tuned on 93 for this.
probably worth asking around if you can only have 93

 

[engineermike]

have you tuned any turbo cars?

Yes, just one. It was a Hellion with 62s on a 9.5/1 aluminator and made 1100 on e85.

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