So had my tune (using uprev) done yesterday and while the tuner was running the logs, it showed a consistent difference in a/f correction. bank 2 was around 100% +/-5% but bank 1 was between 110-125% at idle/cruising. They could not figure out why it was that way, and I could not figure it out either.

I was looking through other threads and am thinking it could be bank 2 downstream o2 sensor? It seems that if upstream and downstream sensors do not agree, the downstream reading can cause it to be rich. I'm assuming that if the upstream sensor was bad it would read lean(take out fuel to improve post-cast readings) or throw codes. the car seems to idle ok and does run ok but the problem still bothers me.

The car is an 03 g35 coupe(no oem widebands) with oem cats, procharged with supporting mods. Anyone have similar issues or any theories to confirm which o2 sensor is bad? Seems to be definitely a sensor on bank 1(passenger side?) but not sure of upstream or downstream.

 

Sounds like you either have an intake or exhaust leak. The car thinks its seeing more air so its dumping more fuel on that side. The downstream sensors only tell the car if the cats are working, the dont effect fueling.

 

I need to go to the car and try and do some logs at idle to monitor sensor voltages. In one of the threads djamps said the front and rear o2 sensors need to match up, or it would start dumping fuel on that side if the rear o2 sensor is bad or is using non-foulers. will check in a few and report results of logs.

 

so here is the log I just took. there is a big discrepancy between both rear o2 sensors. It looks to me like sensor 2 bank 2 is bad because it pretty much stays ~.4 and doesnt change much even with rpm changes. If anyone has some insight it would be appreciated.

 

do you have cats?

Swap both rear o2s and report what happens.

 

yes I have OEM cats. I ordered 2 new rear sensors (oem aftermarket) so will see if it fixes it. I am pretty sure that the bank2 Sensor 2 should have some movement. I didn't rev it high but some of the revs are WOT so the voltages should have changed a lot like bank 1 sensor 1 I'm pretty sure.

 

How much power did you make

 

383/330 on 91 revving to 7k lost quite a bit of boost due to altitude. maxed out at ~9psi and at sea level these pullies should put out 12-13. disappointed with the power, but I kind of expected it to be low with the altitude.

 

What pulley combo.

 

42/24 no belt slip either. but according to the calculations at 7k with that pulley setup and oem crank pulley I am at 80k rpm on the blower. I am still debating on pushing it further or not.

 

Running the belt under or over idler? I have 39/26 and 44/22. But it destroys the belt with 44/22. So I have 39/22 on now and it makes 11psi

 

im running it over(original configuration) as I could not get it to fit even taking off the pulley with total teeth equaling 66(42+24) but with my old setup 39/26 I made 9psi at sea level and ran the belt under. would you sell the 44 pulley if its not worn or torn up?

im at 6500ft elevation though so losing a good amount of boost to that as well here.

 

I think once I fix this issue I will go from a 24 to a 22 pulley and that should get me to 87k rpm at 7k engine rpm and hopefully I can break 400.

 

I think il try a 42/22 and see what happens. I made 17psi with 44/22 but the belts shredded after a few pulls.

And yea with a little more boost you should see 400. I have a lot more mods but I made 400 with 39/26 when I first put the engine in. And I upgraded to a bigger intercooler that made a huge difference on top end.

 

You think I would see any improvement with intercooler upgrade? Im guessing I would see more boost with less restriction. What intercooler did you use?

 

Definitely the stock unit is super small and IATs are out of control . But with the unit I went with I can't run a crash bar. I think you could go with the treadstone unit that's the same size as the PC core except has 3" ports and gain some power.

Here is the one I used
https://www.treadstoneperformance.com/product.phtml?p=86214&cat_key=63&prodname=TRV259+Series+Inte rcooler++1300HP

 

were you able to retain the original piping? If so I would be willing to modify the crash bar to do it.

 

Yes. Just have to figure out a way to transition the piping from 2.5 to 3". The bottom pipe will stay in the same place you will just need a 2.5-3" straight coupler. If you get the intercooler I have its taller so you will have to tweak the top pipe a little or get a 3-2.5" 45 coupler. But it all fits.

 

cool ill have to look into it then. did you gain any boost by upgrading intercooler? and do you have any gains purely from the IC upgrade?

 

Not sure if it gained boost. I rarely look at my gauge. And I'm more sure about power because I just street tune. It dropped my IATs 40* on a 20-120 pull. Andre said he gained 20hp on his vortech setup with larger intercooler. No tuning