AFR Changes Across a Turbo

[CTX-SLPR]

I know WBO2's aren't rated for pre turbo operation but most of the tuning proceedures I've read want you to directly replace the narrowband with the WB and the NB is pre turbo. I don't really see the difference in putting it before or after except for the heat but is this something I should be worried about actually affecting the AFR readings off of the sensor?

Thanks,

[JoeyG]

You can also monitor EGT's while in conjunction with the downstream wideband. The sensors are made to live in a high heat/transfer area. Just make sure to get a wideband with a good sample rate for accuracy.

[CTX-SLPR]

Going to be using an Innovate LC-1 unit with an XD-16 gauge eventually but for the time being tied into the HPTuners box. EGT port is preturbo next to the stock NBO2 bung.

[JoeyG]

I run dual LC1's in my Vette and use another spare LC1 for working on other cars. Its a good unit, especially for the price and it's capabilities, although somewhat limited compared to the other units out there.

[Two Lane Blacktop]

Speaking of dual WBs, there's a vid on this link:



http://www.compperformancegroupstore...ct_Code=170402

[Matt Cramer]

The heat and pressure upstream of the turbo, particularly the heat, will kill the sensor in short order. Innovate recommends putting the sensor about 18" downstream of the turbo, or just downstream of the turbo but with a heat sink or heat shield. (This assumes a normal setup with the turbo in the engine bay; rear mounted turbos are another story.)

The AFR doesn't change across the turbo; it will only change once you get to smog things like an air injection pump. You'd either need to run upstream of these or disable them temporarily for tuning.

EGT is different; it will undergo a bit drop across the turbo.

[dieselgeek]

Matt - CTX is using an OEM EMS with a MAF on a 4.1 liter engine (EMS came off a blown 3.8 I think?)... and I believe the plan is to use the LC1's configurable voltage outputs to mimic a factory narrowband. This works awesome, I've seen it done before...


CTX, I would suggest mounting it where Innovate recommends. Then I would monitor it's output and adjust the scale to be in the range you need for the OEM ECU (and HP Tuners) to be happy. I think that part is going to be easy for you to dial in. The LC-1 is a great little unit for the money. Other suggestion is that it's happier with a long exhaust pipe AFTER the sensor.


-scott

[CTX-SLPR]

The ECM is off of an OBDII L67 FWD supercharged 3800 V6. I think I'm going to leave the stock NBO2 in the stock pre-turbo spot then put the LC1 18in down the downpipe. I plan on running the LC1 output for tuning and then hooking the NBO2 back up for daily driving and monitor the AFR with the gauge. That way I can compare the O2 milivolts off of the NBO2 on the Aeroforce scan gauge and the AFR on the WBO2. Then again I could just hook up the WBO2 to the computer and then run the WBO2 output for the WBO2 gauge.

[dieselgeek]

I think with the LC1 you have lots of options. Would be interesting to see what the narrowband does though, since the EMS did come from a boosted engine it should expect to see richer conditions at WOT.


as much as I don't dig MAfs I think this project is probably going to run pretty good. What kind of things will HP Tuners let you adjust on the GM computer - got any links I can read?

[CTX-SLPR]

It varries from engine to engine. HPTuners is really focused on the Gen III/IV engines as thier main market but they do have a good support for the L36 and L67 3800 motors. I've not bought mine yet, waiting for the check to cash from the sale of my Regal so I can order it up. If I can ever make it to a pull a part yard I'll be grabbing the last 2 sensors I need.
I just thought about something though on the L67 turbo cars.... the O2 is after the turbo since its mounted in the back on the downpipe. The LC2 Turbo6 is what has the NBO2 in front of the turbo. Everyone in the Turbo6 community has stated I'll melt the WBO2 sensor if I stick it before the turbo so I think I answered my own question. Now I just have to plug the stock port unless I wanted to put the "rear" catalyst performance O2 into the pre turbo position and disable the reporting but I should still be able to log the output of the sensor.... hmmm interesting.