From the input about on board O2 sensor monitoring and input Brad has given, I'm seeking information/experience about the Gunson gastester CO analyzer. I am interested in using this method of adapting my D-jet to increased displacement, but at wide open throttle and throughtout the range vs just at idle. Suggestions?
L. McC

Ive never used the Gunson gas tester, but remember seeing many threads about it on Pelican.. why not try a search there?

i've got one and used it to get my MFI car on the map; all the Bosch MFI documents reference adjusting to %CO. what do you want to know ?

i think you'd have a bit of difficulty arranging things to run the hose back into the cabin from the tailpipe (i've thought about it, and haven't found a good way ...) ideally you'd do any kind of part-throttle and full-load tests on a rolling-road chassis dyno.

I'm not thinking of using the gasTester for a continuous A/F meter, but was wondering how we could use it to confirm that we are not getting lean at WOT. You must have thought about running a hose from the exhaust to the cab for sampling.
Has the unit been reliable and accurate?
Thanks,
L. McC

i have, because kinda like a carburetor, a Bosch MFI pump has two "circuits" that control idle and "part-throttle." idle is easy enough to check and correct in the driveway but part-throttle has a long rigamarole that involves long constant-load pulls at 3000 rpm. and naturally, an adjustment to the part-throttle setting affects idle, but not vice versa ... at the moment, i'm going by general performance, fuel economy, and plug reads to have a clue on the part-throttle but i'd really like to have a better handle on it. this is tricky due to the need for a draft-free, exhaust-free environment for the main unit.

i believe it is pretty accurate, certainly for the price. it -does- tend to drift some, which is the standard complaint. IOW - you calibrate it in free air, make some changes, get your readings, re-compare to free air only to discover that it's drifted a bit. not a lot. but if you're playing "anal retentive tuner" and want EXACTLY 4,5% CO it can take a few tries to have the degree of confidence you want.

it is A LOT more accurate than trying to tune by smell, plug reads, "feeling" the lean-surge/rich-hunt zone, or any other kind of shadetree voodoo tuning. sure, i'd rather have a 5-gas analyzer and rolling-road chassis dyno, but for me trying to get my tune 'on the paper' from the total unknown state i got it, it was worth the money for me. and this is a "known combination" all-spec engine, so pretty much all i need to do is turn the knobs until i get the numbers specified in the factory manual.

it's not like i'm trying to dial in a whole new setup (yet...).

Thanks,
I read some of the 911 board postings using the gastester for on the road analysis. It seems that you need a heat resistant tubing, brake liner/ fuel tubing, and a better mechanism, such as a hose clamp, to hold the extension tube into the exhaust and extend into the cab. Then, it is the calibration process and holding for 30sec to obtain an accurate CO reading. Seems a reasonable subsitute for the WBO2 controller and sensor for modifications.