S55 JB4 lean AFR

[AC1981]

Hy

I installed the JB4 / DP combo, while monitoring some parameters with the jb4 connect app im seeing AFR of 14.5-13.8 under load which seems pretty lean to me.

Is this normal for a direct injection engine?

It catches the signals from the OBD port so they should be accurate.

Thanx for the help

Chris

[sA x sKy]

Originally Posted by AC1981

Hy

I installed the JB4 / DP combo, while monitoring some parameters with the jb4 connect app im seeing AFR of 14.5-13.8 under load which seems pretty lean to me.

Is this normal for a direct injection engine?

It catches the signals from the OBD port so they should be accurate.

Thanx for the help

Chris

That's not a lean AFR. That's rich. Those values are normal.

[s2k750]

Originally Posted by sA x sKy

That's not a lean AFR. That's rich. Those values are normal.

Thats rich?! My last turbo car was tuned about a mid 11 and my LS S2000 mid 12.

[Sleeper]

Originally Posted by AC1981

Hy

I installed the JB4 / DP combo, while monitoring some parameters with the jb4 connect app im seeing AFR of 14.5-13.8 under load which seems pretty lean to me.

Is this normal for a direct injection engine?

It catches the signals from the OBD port so they should be accurate.

Thanx for the help

Chris

DI runs significantly leaner than regular injection. BMS has some graphs, IIRC, that show AFR's at full boost similar to what you're stating. I still wouldn't say those values are "rich" though .

[AC1981]

Thanx guys, might post some loggs later on.

Sameet

Thanx for the input man, but your mixing up things or have no clue what your talking about.

[sA x sKy]

Originally Posted by AC1981

Thanx guys, might post some loggs later on.

Sameet

Thanx for the input man, but your mixing up things or have no clue what your talking about.

It's not super rich but anything under 15 is richer. Anything lean to me is above 15. It also depends what kind of load you're talking about.... so how would I know what you're talking about without a log?

[Cloud9blue]

Originally Posted by AC1981

Hy

I installed the JB4 / DP combo, while monitoring some parameters with the jb4 connect app im seeing AFR of 14.5-13.8 under load which seems pretty lean to me.

Is this normal for a direct injection engine?

It catches the signals from the OBD port so they should be accurate.

Thanx for the help

Chris

DI or not, 14 is too lean even for E85, let alone pump gas, assuming your readings is from WOT not just partial throttle... Make sure you set the JB4 correctly, if not you need to contact BMS.

[CaryTheLabelGuy]

Guys, the S55 is a DI (Direct Injection) engine and can tolerate much leaner AFRs, even at peak VE. It is totally normal and perfectly fine to be running AFRs in the 13-14:1 range at peak spool (WOT). The DME will taper AFRs down to the 12.0-12.5:1 range after about 4.5-5k RPM. Anything richer than about 11.5:1 and the S55 will experience misfires.

The S55's DME is very smart and actually operates in closed-loop fuel feedback at WOT. The stock DME will target the AFR it needs to and will use fuel trims to achieve said AFR target.

In other words, don't worry about AFRs. The DME knows what it is doing.

[CaryTheLabelGuy]

Originally Posted by Cloud9blue

DI or not, 14 is too lean even for E85, let alone pump gas, assuming your readings is from WOT not just partial throttle... Make sure you set the JB4 correctly, if not you need to contact BMS.

This isn't true with the S55 or even the N55. Plus, the JB4 has zero control over AFR targets. Like stated above, the DME will target and AFR in the 14:1 range at peak VE.

[BMW M4 PWR]

Originally Posted by CaryTheLabelGuy

Like stated above, the DME will target and AFR in the 14:1 range at peak VE.

Cary, for traditional 9:1compression port injection motors like a 2ZJ we targeted ~11.8 a/f ratio as a solid yet conservative figure to make strong HP while keeping it safe & cool on 93oct pump. What a/f ratio would YOU say is the equivalent for the S55 on 93oct?

And what do you find the DME's targeting exactly?

[ASAP]

Definitely not lean... but I would also expect low 12's, high 11's out of a DI motor...

[Cloud9blue]

Originally Posted by CaryTheLabelGuy

This isn't true with the S55 or even the N55. Plus, the JB4 has zero control over AFR targets. Like stated above, the DME will target and AFR in the 14:1 range at peak VE.

I would like to see logs of people running high 13 and 14 AFR target on S55/N55. I bet they would have massive timing corrections. There is very little difference in terms of DME control and fueling between N54, N55, and S55. If anything, the newer engines are actually a step back since they used cheaper and more reliable solenoid based direct injectors instead of piezo ones on the N54, which has better flow and more accurate injection timing and pattern.

Anyway, this is what a good log on the S55 should look like. http://www.n54tech.com/forums/showthread.php?t=38243

[AC1981]

Thanx for the infos guys

I might get some loggs to show wenn im out next time.

[CaryTheLabelGuy]

Originally Posted by Cloud9blue

I would like to see logs of people running high 13 and 14 AFR target on S55/N55. I bet they would have massive timing corrections. There is very little difference in terms of DME control and fueling between N54, N55, and S55. If anything, the newer engines are actually a step back since they used cheaper and more reliable solenoid based direct injectors instead of piezo ones on the N54, which has better flow and more accurate injection timing and pattern.

Anyway, this is what a good log on the S55 should look like. http://www.n54tech.com/forums/showthread.php?t=38243

The logs you just pointed to prove my point. At peak VE, AFRs are exactly in the range we're talking about, tapering down to the 12:1 range.

I've analyzed hundreds of datalogs on the S55 from multiple cars (including two of my own) this AFR is perfectly fine.

What's the issue?

[Cloud9blue]

Originally Posted by CaryTheLabelGuy

The logs you just pointed to prove my point. At peak VE, AFRs are exactly in the range we're talking about, tapering down to the 12:1 range.

I've analyzed hundreds of datalogs on the S55 from multiple cars (including two of my own) this AFR is perfectly fine.

What's the issue?

You conveniently failed to mention it tapers down to low 12 at upper end of the rev curve...

Anyway, OP needs log. 13-14 AFR at lower mid range is fine, but not under WOT at top of the rev curve where you are making most of the power on this engine.

[CaryTheLabelGuy]

Originally Posted by Cloud9blue

You conveniently failed to mention it tapers down to low 12 at upper end of the rev curve...

Anyway, OP needs log. 13-14 AFR at lower mid range is fine, but not under WOT at top of the rev curve where you are making most of the power on this engine.

Did you actually read my first post in this thread? You conviently failed to read my first post.

You should recuse yourself from this discussion as you clearly don't know what you're talking about and are derailing this thread with gross incompetence.

[Cloud9blue]

Originally Posted by CaryTheLabelGuy

Did you actually read my first post in this thread? You conviently failed to read my first post.

You should recuse yourself from this discussion as you clearly don't know what you're talking about and are derailing this thread with gross incompetence.

Well. I am sorry that I skipped your first post. No need to get this defensive though... Gezzz

[CaryTheLabelGuy]

Originally Posted by BMW M4 PWR

Cary, for traditional 9:1compression port injection motors like a 2ZJ we targeted ~11.8 a/f ratio as a solid yet conservative figure to make strong HP while keeping it safe & cool on 93oct pump. What a/f ratio would YOU say is the equivalent for the S55 on 93oct?

And what do you find the DME's targeting exactly?

All engines are different, particularly DI engines. Static Compression Ratios play only a small part in this equation. Effective compression, cylinder head design, piston design.....etc all play a part in what a safe and Effecient AFR.

The best AFR for the S55 is what the DME is targeting, at least on the stock turbos.

[CaryTheLabelGuy]

Originally Posted by Cloud9blue

Well. I am sorry that I skipped your first post. No need to get this defensive though... Gezzz

I'm not getting defensive, you were and I called you out on it.

[JamesGames]

Originally Posted by CaryTheLabelGuy

All engines are different, particularly DI engines. Static Compression Ratios play only a small part in this equation. Effective compression, cylinder head design, piston design.....etc all play a part in what a safe and Effecient AFR.

The best AFR for the S55 is what the DME is targeting, at least on the stock turbos.

Thanks for your informative posts regarding the S55s DME. So removing cats and adding intakes and what not used to make my older car run lean (350z) but assuming the DME targets certain A/F ratios, would that not be the case for the S55?

[CaryTheLabelGuy]

Originally Posted by JamesGames

Thanks for your informative posts regarding the S55s DME. So removing cats and adding intakes and what not used to make my older car run lean (350z) but assuming the DME targets certain A/F ratios, would that not be the case for the S55?

The S55's Bosch DME is probably the most advanced ECU/DME I've ever been privy to. It operates in full-time closed-loop fuel feedback, even at WOT. It will meet its target AFR regardless, using its fuel trims, until it runs out of trim headroom. The stock fuel system, however, is capable of much more headroom than the trims allow. If fuel trims go too lean, the DME will enter protection mode and will lower AFR targets down into the 11.0:1 range and richer, which will cause misfires, especially on ethanol mixtures (which is usually what causes fuel trims to be too lean).

I've worked with lots of platforms, and I can honestly say that the S55's DME is pretty amazing and very trustworthy.

[JamesGames]

Originally Posted by CaryTheLabelGuy

The S55's Bosch DME is probably the most advanced ECU/DME I've ever been privy to. It operates in full-time closed-loop fuel feedback, even at WOT. It will meet its target AFR regardless, using its fuel trims, until it runs out of trim headroom. The stock fuel system, however, is capable of much more headroom than the trims allow. If fuel trims go too lean, the DME will enter protection mode and will lower AFR targets down into the 11.0:1 range and richer, which will cause misfires, especially on ethanol mixtures (which is usually what causes fuel trims to be too lean).

I've worked with lots of platforms, and I can honestly say that the S55's DME is pretty amazing and very trustworthy.

Good to hear.. so it's safe to say people running intakes / downpipes without tune don't have a/f ratio issues?