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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Optimum AFR for DI?



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      01-15-2008, 08:16 PM   #23
BzzzBom
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Originally Posted by shiv@vishnu View Post
I think Malekreza11 hit it right on the head. There is really no reason to run a DI engine as rich as a convention engine. Just a waste of gas.

The usual knock tendency you see crop up with running a conventional moderately boost non-DI turbo engine in the 13-13.5:1 range does happy with the N54 engine. In fact, you can almost run it on either side of stoich and not see much difference in power or allowable advance. It's pretty neat.

Shiv
Doesn't this mean that piggybacks that control boost only are all that is needed for moderate levels (11-13 PSI) of peak boost? I have never seen one reported SES or CEL reported with the SSTT or JB1 and both products keep the AFR under 13 at higher rpms. How much boost can safely be run using the stock AFR maps (i.e., intercepting the TMAP sensor only)
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      01-15-2008, 08:59 PM   #24
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Quote:
Originally Posted by shiv@vishnu View Post
I think Malekreza11 hit it right on the head. There is really no reason to run a DI engine as rich as a convention engine. Just a waste of gas.

The usual knock tendency you see crop up with running a conventional moderately boost non-DI turbo engine in the 13-13.5:1 range does happy with the N54 engine. In fact, you can almost run it on either side of stoich and not see much difference in power or allowable advance. It's pretty neat.

Shiv
Is this consistent with the post listed below from March 2007?

Without adjustments to fuel and timing, that 2-3psi bump in power is going to dig right into the margin of safety that BMW left in the tuning. Really not a good idea in my opinion. Especially for a car that runs so lean from the factory. But what you are proposing is easy to do. All you need to do is isolate the signal wire in the MAP sensor (simple 0-5v) and attenuate the signal a bit (perhaps 10%).

-shiv
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      01-15-2008, 09:32 PM   #25
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Quote:
Originally Posted by BzzzBom View Post
Is this consistent with the post listed below from March 2007?

Without adjustments to fuel and timing, that 2-3psi bump in power is going to dig right into the margin of safety that BMW left in the tuning. Really not a good idea in my opinion. Especially for a car that runs so lean from the factory. But what you are proposing is easy to do. All you need to do is isolate the signal wire in the MAP sensor (simple 0-5v) and attenuate the signal a bit (perhaps 10%).

-shiv
It's pretty consistent. Timing adjustments was/is the biggest contributor to knock threshold. Fueling is a small contributor once it steps out side a certain range. But with DI, that range is surprisingly wide and lean, as discussed in this thread.

Shiv
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      01-16-2008, 10:57 PM   #26
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A/F is for thermal management. Contrary to what people might believe, It really has no big effect on hp. DI has a cooling advantage over port type injection. Thus allowing for a more leaner mixture.. Cleaner burn and better gas mileage. Ignition timing is where you make the power. Hope this helps.


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Max
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      01-17-2008, 09:16 PM   #27
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Originally Posted by Max@Logic View Post
A/F is for thermal management. Contrary to what people might believe, It really has no big effect on hp. DI has a cooling advantage over port type injection. Thus allowing for a more leaner mixture.. Cleaner burn and better gas mileage. Ignition timing is where you make the power. Hope this helps.

All the Best,
Max
It very much does. Thank you.
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