[AYF80]

Originally Posted by Lulz_M3

Not sure what branch of service you're in but I'm hoping you're not a pilot... It's spelled HANGAR!

Thank you...

[Transport3r]

Any data from the initial runs?
You promised numbers 'soon' 4 weeks ago, and Vishnu has had a dynosheet out for almost a week now! What are you waiting for?

I guess I'm just impatient lol..

[HPF Chris]

Originally Posted by evilstib

Dyno Results?

We unfortunately learned that with the Vishnu system and other piggybacks available for the N54 we are unable to run with both oxygen sensors after the turbo. This is because there is cylinder trimming going on with the front bank separate from the rear bank. When both oxygen sensors are after the turbo the factory computer sometimes trims the fuel incorrectly.

We will have a new turbo manifold with both banks separated mid March and will get the car back on the dyno. By then Shiv will be done with the electronic boost control so we can ditch the manual boost controller we had to use.

Chris.

[Q4P]

Now that is one update.

[OpenFlash]

Originally Posted by HPF Chris

We unfortunately learned that with the Vishnu system and other piggybacks available for the N54 we are unable to run with both oxygen sensors after the turbo. This is because there is cylinder trimming going on with the front bank separate from the rear bank. When both oxygen sensors are after the turbo the factory computer sometimes trims the fuel incorrectly.

We will have a new turbo manifold with both banks separated mid March and will get the car back on the dyno. By then Shiv will be done with the electronic boost control so we can ditch the manual boost controller we had to use.

Chris.

Just to clarify, it's the DME's fuel control logic which requires bank separation with regards to lambda/o2 feedback, not the Procede itself. In essense, it treats the engine like two individual 3 cylinder engines. Looking forward to seeing you guys back up and running soon...

Shiv

[Z3->WRX->335]

Come onnnnn, come onnnnn! (in my best cartman voice)

[dzenno]

Originally Posted by HPF Chris

We unfortunately learned that with the Vishnu system and other piggybacks available for the N54 we are unable to run with both oxygen sensors after the turbo. This is because there is cylinder trimming going on with the front bank separate from the rear bank. When both oxygen sensors are after the turbo the factory computer sometimes trims the fuel incorrectly.

We will have a new turbo manifold with both banks separated mid March and will get the car back on the dyno. By then Shiv will be done with the electronic boost control so we can ditch the manual boost controller we had to use.

Chris.

Thanks for the update Chris. Some tuners never disclosed reasons for shutting down their single turbo projects in the past and you have my respect for disclosing these details sir!

One thing I'd like to bring up is that your current manifold design may be perfectly fine for the N55 engine that has a single O2 sensor and a single turbo so you may want to try that one there...just a thought...

Good luck and looking forward to the redesigned N54 single mani Would love to see it tuned with a capable flash tune as well such as Cobb..

[turugara]

Originally Posted by dzenno

One thing I'd like to bring up is that your current manifold design may be perfectly fine for the N55 engine that has a single O2 sensor and a single turbo so you may want to try that one there...just a thought...
.

This is an excellent idea if I say so myself

[Rob@RBTurbo]

That's is correct. Find a N55 and have away at it! You will need to do some minor flange tweaking for proper mounting, but that is it.

[F80M]

Originally Posted by HPF Chris

We will have a new turbo manifold with both banks separated mid March

Chris.

This year?

[scottp999]

Originally Posted by HPF Chris

By then Shiv will be done with the electronic boost control so we can ditch the manual boost controller we had to use.

I think he finished up the procede boost control yesterday. Good luck guys, keep up the good work.

[335iJWC]

Originally Posted by HPF Chris

We unfortunately learned that with the Vishnu system and other piggybacks available for the N54 we are unable to run with both oxygen sensors after the turbo. This is because there is cylinder trimming going on with the front bank separate from the rear bank. When both oxygen sensors are after the turbo the factory computer sometimes trims the fuel incorrectly.

We will have a new turbo manifold with both banks separated mid March and will get the car back on the dyno. By then Shiv will be done with the electronic boost control so we can ditch the manual boost controller we had to use.

Chris.

very sad news hope fully soon the beast will be back on its feet

[import36]

thanks for the honesty Chris...looking forward to continued progress/updates come March.

[MilehighM3]

Can't you get a flash tuner to turn off the unused post cat O2 and nothing else? Ten tune from there with the procede if that's your choice of tuners at this time. Shit, turn off both post cat O2 sensors. It's not like it'll have cat(s) any way. Then tune away! Work smarter, not harder guys. Just my .02...

[OpenFlash]

Originally Posted by Bmw135er

Can't you get a flash tuner to turn off the unused post cat O2 and nothing else? Ten tune from there with the procede if that's your choice of tuners at this time. Shit, turn off both post cat O2 sensors. It's not like it'll have cat(s) any way. Then tune away! Work smarter, not harder guys. Just my .02...

The issue has nothing to do with post cat lambda monitoring. But rather front lambda (pre cat) fuel control. The DME employs two closed loop fuel control routines. One for cyl 1-3 and another, running in parallel, for cyl 4-6. So merging all 6 cylinders and feeding the DME the signal from the front lambda sensors (now reading all 6 cylinders) allows for the two closed loop systems to "fight" each other. And opens up the possibility for one bank to run lean while the other to run rich. The average of all 6 cylinders, in such a case, would still read "normal" and the DME wouldn't know anything is wrong.

Some "tooners" haves suggested modifying the DME code to employ only 1 closed loop fuel control routine for all 6 cylinders. Now THAT would be a step in the wrong direction as you are giving up 1/2 of the stock DME's fuel control precision. Something much welcome when making big power. Heck, if I had a genie, I'd wish for a DME that employs 6 closed loop systems running in parallel, each being fed a lambda signals from 6 individual o2 sensors mounted in each exhaust runner (pre turbo). But you'd only see such excess in extreme cases. But for real world street use, dual bank fuel control is great and just adds to the beauty of the n54 control control system.

Shiv

[dzenno]

rear o2 sensors ARE responsible and DO play into fuel modes which piggyback based tunes just don't have the visibility into...

Regardless of that, the more front o2 wideband sensors the higher the refinement in fuel control and I definitely wouldn't go to a single when a dual wideband provides for twice the accuracy...

Also, not to stir the pot, we all know what sort of tuning has the ultimate in fuel control, speed, refinement and visibility -> you guessed it, the engine computer (DME)...for me, coupling the fuel control logic in the DME along with both front wideband o2 sensors would be the way to go, but that's just me

I just can't wait to see some proper numbers out of these singles on stock engine hardware as I'm sure we all do...huge respect to those pushing forward on this front, both HPF and Vishnu!

[bryce]

Originally Posted by dzenno

rear o2 sensors ARE responsible and DO play into fuel modes which piggyback based tunes just don't have the visibility into...

do you have a link or source for that? not trying to be argumentative, but everything i've learned on this platform and previous platforms has indicated that secondary oxygen sensors merely detect catalytic converter efficiency; not fuel control or anything more than that. on previous cars, i turned off rear o2 sensors to avoid having cat codes

[bryce]

Originally Posted by HPF Chris

We unfortunately learned that with the Vishnu system and other piggybacks available for the N54 we are unable to run with both oxygen sensors after the turbo. This is because there is cylinder trimming going on with the front bank separate from the rear bank. When both oxygen sensors are after the turbo the factory computer sometimes trims the fuel incorrectly.

We will have a new turbo manifold with both banks separated mid March and will get the car back on the dyno. By then Shiv will be done with the electronic boost control so we can ditch the manual boost controller we had to use.

Chris.

this fact/concern was brought up several times in this thread. it's a shame hpf couldn't monitor this thread closer, there were several members (including myself) bringing up concerns of the primary oxygen sensor placement (or lack there of) on the HPF manifold.

[bryce]

^page 26 in particular
http://www.e90post.com/forums/showth...8#post11273538

[dzenno]

Originally Posted by bryce

do you have a link or source for that? not trying to be argumentative, but everything i've learned on this platform and previous platforms has indicated that secondary oxygen sensors merely detect catalytic converter efficiency; not fuel control or anything more than that. on previous cars, i turned off rear o2 sensors to avoid having cat codes

All you would need to do is plug a Cobb AP into your car, unplug your rear o2 sensors or run the stage1 map and be catless and we all know what happens then, you get a CEL for cat inefficiency...ONCE that is triggered, the DME will run a different fuel "mode" on your car...how that reflects on power at this point I can't say for sure but it does impact "fueling"...if you'd like any further details don't hesitate to ask cobb or post in their thread...

another example: when a car misfires, fuel mode changes as well, different from the above...normal running fuel mode is fuel mode 2, when a car misfires DME goes into fuel mode 15 (fuel system shutdown) to prevent damage to your catalytic converters from unburnt fuel...it goes back to 2 once you restart the car if everything is fine and no more misfiring

there are literally massive numbers of monitors in the dme and these are just some of them

[OpenFlash]

Originally Posted by dzenno

rear o2 sensors ARE responsible and DO play into fuel modes which piggyback based tunes just don't have the visibility into...

Rear lambda sensors do have influence on fuel trims because they are known to be very accurate around stoich. So the DME uses them as reference for lambda calibration/plausibility checks. Which is why you will trigger trimming codes if one of the rear sensors starts to fail. Or if you are using a "downpipe fix" that is too strong. During engine load when AFR target is rich, they are largely ignored since they aren't accurate on that side of the response curve.

Regardless of that, the more front o2 wideband sensors the higher the refinement in fuel control and I definitely wouldn't go to a single when a dual wideband provides for twice the accuracy...

Also, not to stir the pot, we all know what sort of tuning has the ultimate in fuel control, speed, refinement and visibility -> you guessed it, the engine computer (DME)...for me, coupling the fuel control logic in the DME along with both front wideband o2 sensors would be the way to go, but that's just me

Not sure how that could stir the pot since this is already implemented. The factory lambda sensors are fast-acting widebands. What's more is that they require almost no exhaust pressure compensations to provide accurate readings. This isn't the case with most aftermarket widebands that I've tested.

my 2c
shiv

[GeorgiaTech335coupe]

Originally Posted by shiv@vishnu

Some "tooners" haves suggested modifying the DME code to employ only 1 closed loop fuel control routine for all 6 cylinders. Now THAT would be a step in the wrong direction as you are giving up 1/2 of the stock DME's fuel control precision. Something much welcome when making big power. Heck, if I had a genie, I'd wish for a DME that employs 6 closed loop systems running in parallel, each being fed a lambda signals from 6 individual o2 sensors mounted in each exhaust runner (pre turbo). But you'd only see such excess in extreme cases. But for real world street use, dual bank fuel control is great and just adds to the beauty of the n54 control control system.

Shiv

Plus I'm sure rewriting the control system that works as well as the DME would be a very tough task, even for those who are educated in control systems. A lot of people don't have a full understanding and under-appreciation of the complexities of control systems, how they work, why they are needed, and how to go about testing before implementing them. Controls is always one of the tougher courses in the mechanical engineering discipline - lots of diffEQ involved.