Hello ,
I purchased an aem afr guage to help with my afr readings since I have put a few mods on my 2004 mini cooper s and to help with dialing in with the tune.

I know people reccomend placing wideband before any cats. My question is could it be run after the pre-cat on a oem r53 manifold ? ( between pre-cat and stock cat)? Would the readings be totally off or just minimal? I am curious as when they do dyno tuning dont they run the wideband on the tailpipe?



Thanks a million

 

You'll be fine to run it after the pre-cat if that's your only option.

 

can you? Sure but it's far less accurate. The instructions for your wideband will say before cat.

 

Yes I understand that the wideband is much more accurate before any cats. I am still curious as to how does a tuning shop do afr readings when tuning via the exhaust then? Woulnt the afr values be off? I am trying to understand how much more difference the readings would be between sensor being before the pre- cat or right after the pre-cat. Are we perhaps talking a 10% variance or more like 40 to 50 % off ?

Thank you

 

It's less accurate, but can get him close to a good tune.

If a dyno is tuning via exhaust with a wideband probe, they'll get you a solid tune. But, if you want the BEST tune, you mount the wideband pre-cat.

From what it sounds like, you're just trying to compensate your tune for the new mods... putting the wideband between the cats will be fine for that.

 

tail pipe sensors are ok at best, wideband after cat can be up to a full point off it depends on how close to stoich, flow, and the cat not all are equal.

If welding a bung on, just do it right.. There is room right next to the stock bung just point it the other direction. That said the stock header is garbage do it all the way right and put a 4:2:1 or 4:1 on, they are cheap now. Go with obx thing graphite header gasket not the ones that look perforated. Summit has a nice 4:2:1 that also gets rid of the dumb flex pipe and puts a proper donut on

 

I see , thank you. Got the wideband to keep eye on afr , but mostly to update tune properly to accommodate the cam mod . Reasoning was that I have an existing extra bung ( long story....) between the cats and instead of paying shop to drop manifold for new bung I would just use the existing .

 

Thank you, yes def would like to put it before the cat, just trying to save some funds as I have an existing bung between cats. Would def want the more accurate readings .

As for the summit racing 4-2-1 manifold are u referring to the xforce? I was actually considering a manifold if my stock one has to be dropped anyway. I was looking atbthe obx and scorpion , but they both have gone up quite a bit in price especially having to ship.it out of usa. Do u run the xforce and are u happy with the quality and fitment out of the box. ?

 

yes the xforce, pretty sure it is a obx.. I have the xforce on my bvh car and it works well it's nicely built

 

u are right I did notice it looks quite similar to the obx . I was leaning towards the scorpion , but the flex basket has me a little worried from the info I gathered online .
as for the header gasket u recommend, is it available on summit also? Can't seem to find it ?

 

i've been using ebay to source them

 

are u running decat or with cat? Did u find the car got way louder with the manifold? Will probably be welding the manifold to the stock cat and didn't really want to make the car loud . Currently have stock manifold and cat to magnaflow catback exhaust

 

one of my cars has a high flow, the other has no cat. no cat has quite a bit more volume

 

From what I am reading, the OP is more asking "can it be done" vs. "should it be done", based on using an existing bung for the wideband (and thus saving some time and effort)

Can it be ran between the pre-cat and main cat, and still get a reliable and good tune... yes.
Should it be ran prior to the pre-cat... also yes.