Thread: Running rough and lacking power

Steve

That makes sense, as I am driving around 150k per day it seems to be improving.....or am I just getting used to it

Gary

Originally Posted by TheTree

The nanocom docs seem to suggest that the MAF, temperature sensors and other things play a part in the this, not just the O2 sensors

Certainly resetting the adaptive values cannot do any harm

Steve

Ummm.. there are no "adaptive values" to reset on the GEMS system.
Prior to the Bosch Motronic system the GEMS fuel maps were developed over hundreds of hours using a dyno and real life testing plugged into an exhaust gas analyser. The database of fuel map values for a given set of conditions associated with the sensors above, were then laboriously fiddled with based on what the exhaust gas analyser was telling the engineers to get the optimum fuel burn. Hence Arctic cold weather /African desert hot weather etc etc

with the bosch motronic system, the incorporation of oxygen sensors did away with the need to drag around an exhaust gas analyser... the system gets the feedback instantaneously and through an "adaptive learning" mechanism plugs new "trimmed" values into the EMS databank for its closed loop operation... like a constant fine tuning exercise.

Resetting these values essentially deletes all the trimmed values, the system reverts to the 'factory default' setup and the system begins all over.

hope this helps

Hoges

This is from the nancom manual for GEMS and it seems to suggests there are other things apart from the O2 sensors.

"Reset all adaptive values: As the GEMS runs, it keeps a long-term tally of the constant adjustments it is making to keep values on target. After a while it realizes that it is always adding or subtracting more or less the same amounts and so stores these adjustments as long term adaptive values (those it always uses). These adjustments are really designed to compensate for tolerance in components, natural leakage through gaskets, or air spillage etc. If, however, major rebuilds are undertaken or major components replaced, these values could suddenly become very wrong. This function deletes the current adaptive values (except short term idle) for the stored closed throttle position, which controls the idle speed, and for adaptive AMFR, which controls the fuel mixture, and makes the system re-learn them. "

Steve

Hi Steve
That's really interesting! I wonder what the system measures against to know what changes to make... and whether it's "adaptions" are based solely on driving style... if that's the case then an "Italian tune-up" might be just the thing to make it more lively around town
Cheers
Hoges

EDIT: AhHa! managed to find the Nanocom explanation: the Adaptive Values probably also 'learn' various settings and adjust spark and fuel timing in conjunction with feedback from knock sensors--for example.

WRT fuel however, the GEMS engines brought to Australia were without Oxygen sensors but they were fitted for other markets. Thus "...On vehicles with no oxygen sensors the Adaptive AirMass Flow Rate (AMFR) will have to be manually set as the system has no feedback to learn this value. This can be done in the Settings section and requires an external CO meter."

So, the Australian versions of GEMS always run "open loop"...but the definition of "Adaptive values" applying to GEMS is slightly different from that applying to Thor engines which includes adaptive values derived from "Fuel trim"
Which stirs memory of some folk from this forum retro-fitting O2 sensors to GEMS engines???

Hoges

I have retro-fitted O2 sensors but I had to get a later ECU as well so it would recognise them

This is in prep for a Mark Adams Tornado chip

Steve

Dont rule out air leaks, they cause all sorts of bizarre issues.

I battled a number of o2 sensor and rich condition errors on my D2 V8, changed MAF, o2 sensors etc - no change.

One day I went over it with a hose to my ear and could hear obvious hissing from the manifold area, stripped it down - no inlet manifold gasket fitted!!

I also think the injector seals were perished and leaking.

Sorted all that and it has been good as gold since.

Originally Posted by ashhhhh

Dont rule out air leaks, they cause all sorts of bizarre issues.

I battled a number of o2 sensor and rich condition errors on my D2 V8, changed MAF, o2 sensors etc - no change.

One day I went over it with a hose to my ear and could hear obvious hissing from the manifold area, stripped it down - no inlet manifold gasket fitted!!

I also think the injector seals were perished and leaking.

Sorted all that and it has been good as gold since.

Good tip!

Vacuum gauges are cheap and very easy to use as well

Steve

With the new muffler quietening things down several notches it has also helped out with the roughness. Not completely but has certainly helped. Power still seems a bit light on until around 2200 rpm and is particularly rough around 1800 a 2000 rpm.
On a really positive note though I did fix my cruise control.....the usual split vacuum hoses (x2) in the engine bay. The short one that goes from vacuum pump to tee, and the long one the goes to the brake pedal switch. Fortunately the long one was long enough to trim a little bit off the end. As for the shot one it's been replaced with some fuel line that I had laying around....it works .

Gary