Thread: V8 Bruce Davis chip upgrade

Originally Posted by ozscott

Andrew I understood that all oz discos only had upstream o2's unlike NAS that have both.

Cheers

From what Bruce said there are 2, 1 I think is up in the engine bay end and the other I believe is under the car somewhere, where ever they are he had to let it cool down for an hour before he could get to them or he said he would burn the hell out of his hands.....from his expression I'm guessing he learnt that lesson the hard way lol

Thanks hoges that prob explains it! Would that be why it was in limp mode then?

Interesting..mine only has 2 in total.

Cheers

AU spec only requires 2 O2 sensors, both are located (at least on the D2) on the down pipes, pre cat. The other 2 in US spec models are located post cat.

Originally Posted by clubagreenie

AU spec only requires 2 O2 sensors, both are located (at least on the D2) on the down pipes, pre cat. The other 2 in US spec models are located post cat.

x2
The NAS vehicles AFAIK also have extra kit bolted on such as EGR and SAI (secondary air injection). Having the extra set of O2 sensors downstream of the cats monitors the cats' performance/ efficiency, data from which no doubt feeds back and regulates the EGR/SAI...

Originally Posted by disco2_dan

Thanks hoges that prob explains it! Would that be why it was in limp mode then?

I really don't know re. the "limp mode" for the EFI. Can understand why it may have felt sluggish prior to taking it in for the rechip given that the MAF was deficient and the O2 sensors disconnected. Possibly BD meant that when the system detects these problems it may have been programmed to use a restricted data set from the full fuel mapping database as a compromise performance profile pending faults being cleared.

Somewhere I read that disconnecting the O2 sensors and/or a faulty MAF will trigger the MIL light on NAS spec vehicles, but not on non-NAS variants. So, it's no surprise that without physically checking them, you were not to know that the O2 sensors were 'off the air'.

Re fuel range: It really does depend on load /distance and traffic density. My P38 drinks fuel at around 20+ l/100km on short, heavy traffic trips (which is why I generally won't drive it unless I'm doing about 50km ...) yet for Bris-Toowoomba return (250km all up) this figure drops to 11.5-12 L/100km (at the pump). Mind you, the wife's ASTRA 1.8 automatic only gets 12.5 L/100km around the inner city (Bris) but 6.1 -6.4 L/100km on the Toowoomba run...

When the MAF fails the system may flip into open loop mode and if the MAF completely dumps sending a signal then it'll stop fuel (no air coming in according to MAF) but then the O2 sensors see unburnt O2 and say add fuel.

Had this issue a while back and lead to a rebuild of the auto as the symptoms were just like a slipping auto.

Well filled the tank up the other night and went to ourimba today to see relo's and well it a different car, no probs accellorating up any hills in 5th gear at hwy speeds plus did about 20-30km off road prob 10km of which was low range and I'm pretty sure it's on par with before, about 12.5L per hundred, but won't be 100% sure till I fill up again I'm upto about 300km and its in the same spot as usual only difference is the amount of power, now I know the O2 sensors and airflow meter will account for quite a percent too but taking that into account I'm still happy with the difference..... I would like to be able to go for A run with someone who has got a stock one just to guesstimate how much difference there actually is, I would think as an absolute shot in the dark but compared to what it was and is now its about 40% difference... Now I'm prob going to get shredded for saying that but hey it's just my "feeling" the difference....