Lambda Sensor

[D.Carmichael]

I'm not quite clear on this topic, so I am asking again.

What are some of the reason's for disconnecting the Lambda sensor if you have a BB Power Chip?

And has anyone tried it with positive results

[SteveN]

Sorry for the long post, but this is interesting stuff...

Several posts have questioned the role of the lambda sensor and performance. Well I certainly found the combination for my bike.

Last week I installed the San Jose performance air filter and a new air snorkel/InDuct. Seat of the pants feelings was that the bike pulled much better from about 3000 rpm to the red line in all gears. This was shown to be true by 60-80mph and 80-100 top gear timed roll-ons and quarter-mile runs.

Compared to past times with my bike PRIOR to the air filter and snorkel installation, the bike was now faster:

60-80 mph and 80-100---

Stage 2, 3, 4 .1-.2s faster

Quarter mile times improved from an average of:

Pre-air filter, etc.---
12.03s

Post-air filter, etc.---
11.85s

I then DISCONNECTED the lambda sensor and another big improvement! Previously (prior to the air filter/snorkel) I had reported that disconnecting the lambda sensor, at least on my bike, decreased mid-range performance at all stages with the BBPower chip.

However, AFTER installing the air filter/snorkel, disconnecting the lambda sensor made a BIG improvement in performance. I also found that the BBPower chip settings changed dramatically from pre-air filter/snorkel setup.

Stage 5 is now best for mid-range through 8700+ rpms with little to no popping and overall a very smooth running bike.

Stage 4 is quite close in performance and smoothness. In fact gas mileage may be the only improvement if even that turns out to be true.

Stage 3 less improvement and Stage 2 doesn't give any improvement over times with the sensor connected.

Quarter mile times with the lambda sensor disconnected + the air filter combo have now improved to:

11.65s

60-80 and 80-100 mph top gear roll-ons improved on average another .1-.2s. I consistently get 60-80 mph times of 3.9-4.0s.

The Ducati ST4 (2 of them) that previously pulled my bike about 1 bike length on a 60-80 top gear roll-on now falls behind by about 1.5-2 bike lengths.

Just to make sure I wasn't imaging all this I re-connected the lambda sensor and retested roll-on times for stage 2, 3,4, and 5. The findings confirmed the improvement AFTER disconnecting the lambda sensor only WHEN the performance filter/snorkel are also part of the package.

SUMMARY: On my bike I find the best mid-range to red line performance combo to be-----

Current Setup:

Full Laser exhaust (open) + Laser cat replacement
BBPower chip
San Jose performance air filter
Snorkel/InDuct

Stage 5 (4 still very good)
Lambda sensor DISCONNECTED.

Without the air filter and snorkel, disconnecting the lambda sensor gives the poorer mid-range to red line performance at each stage setting.

As Lennie has suggested, lots of changes can occur when the bike starts gulping more air and not all these changes are apparent on a dyno.

Some may find this setup strange or question it, but it sure works for me. While I don't have any dyno numbers, quarter mile times at the same strip with nearly identical environmental factors certainly confirm these differences, not to mention the huge smile on my face everytime I hit the throttle in any gear.

And isn't that what all this is about. Good luck in your performance search.

steve

[This message has been edited by SteveN (edited 08-26-2001).]

[Bob Hancock]

Very interesting post, especially the part about the ST4. I had an ST4 for awhile and my S didn't stand a chance of keeping up with it once the Duc got above about 6000 rpm. I dyno'd the ST4 and it was making 107 at the rear wheel.
Since I haven't been happy with the supposed performance improvement of my Remus Race exhaust with BBP chip, I think I'll try your setup. (The only improvement has been the sound.) The only thing I don't have yet is the snorkel.
Thanks for the data and the suggestions.
Bob Hancock
'99 R11S
'01 996

[roger albert]

Wow, Glad you started this thread D.C.

Steve, that was one ass-kickin' post. Great info. I know testing and documenting and then reporting all of that stuff takes a fair amount of time, but besides you're own edification, please know it's appreciated. Except for the mufflers and filter, that's the exact setup I'm about to have. That would imply I'll want something around stage 4 and will have to play with the Lamda sensor to see what happens. Anyway, thanks.

Back to D.C.s question. The way most engine controllers work, is that when a sensor is detected as failing or disconnected, the computer substitutes a fixed value. On most systems this limp-mode is on the rich side (though my stupid '86 Audi is on the lean side and sucks - corrected by Audi in '87, btw) Anyway, it would seem that dumping the sensor put's this particular ECU into a pretty rich mode. The minus is of course very likely worse economy, but probably not bad if you're correspondingly light on the throttle. Though you're still getting the rev limiter and ignition curve advantages of the BBPower chip, you've essentially thrown away the fuel mapping benefits.

The question in my mind is, where is the limp -home/failed-sensor fixed fuel value stored (probably the ROM) and if so, is that assumed value different for the BBP than the stock chip (i.e would pulling the lambda have more, less, or the same effect on ECUS that are stock vs BBPower fitted) ?

Anyone know?

later
roger

[SteveN]

I'd like to clarify one thing and agree with Bob. I'm not deluding myself into thinking I now have a bike faster than an ST4. No, I don't!!

I can handle the Duc at the ranges I've been testing and where I ride alot...50-100 mph. Above 100mph the Duc starts driving away. Quarter mile times are also much better for the ST4; low 11's at 120+ mph versus mid-11's at 115+,

The new "found performance" combined with riding comfort and uniqueness of my bike make me quite happy.

[rob_wijhenke]

Hi all, if you plan to do similar testing can you please be so kind to post the results? I would very much like to compile it to something for posting on my site.

thanks
rob