Tech

iTrader: (1)

How much overlap is too much to tune using factory sensors in closed loop?

AFR225 heads, LSX intake, 90mm TB, 1 7/8 headers w/ 3" duals and an H-pipe.

98Z28CobraKiller

iTrader: (17)

I think that the MAF is going to max out. I went SD and have had alot of success taming the cam and getting my idle close. I have a similar setup I just couldn't swing the LSX intake and big TB yet.

Tech

iTrader: (1)

I don't think the MAF will max at idle. Thanks for the reply, tho.

Tech

iTrader: (1)

Why is it so difficult to get an answer on this site sometimes? Seems like if it isn't an appearance mod or contain flow/dyno numbers, nobody can offer any advice.

white2001s10

iTrader: (4)

There isn't any magic cutoff number for overlap since so many factors play into the oxygen content of the exhaust.
Being that you're even asking this question, I'd think it's safe to say that you'd be better off with a OLSD tune. Then you'll never have to worry.

Unless you have a very good reason for running O2's and closed loop, then don't.

98Z28CobraKiller

iTrader: (17)

I didnt mean at idle. I meant at WOT. I had a hell of a time with my idle with the MAF on. It is much easier to get idling in SD mode and since you have to disconnect it to get the VE tables dialed in anyways, why not just leave it out? JMHO. It's really up to you.

Tech

iTrader: (1)

I would prefer to keep all of the sensors functioning however, it seems as tho the 02 sensors can't get accurate info with nearly 20* of overlap. The base tune was done on an engine dyno and there are a few things that have raised an eyebrow. One thing being, the cylinder volume is stock. Another is the values the tuner used for the IFR.

We are going to start completely over with it. The thing I'm having a hard time with is that the oxygen sensors (WB and NB) will never get an accurate picture of what's happening in the CC. How will I know for certain that the engine is getting the proper mixture if I can't get accurate measurements out of the exhaust? Wouldn't even an EGT sensor be slightly skewed with the outside air entering the exhaust port?

Tech

iTrader: (1)

Most of the time the car idles like a champ. It has an intermittent problem. Seems to happen more when the temps are cooler.

TAQuickness

iTrader: (28)

to get accurate readings from you wb, you will need to be in open loop

SmokingWS6

iTrader: (1)

Hey Jason, give me a ring this weekend.

Tech

iTrader: (1)

I realize this. I think you've been talking to the owner of the car on EFIlive's website. The question I am having is.... can we not trust the 02 sensors (either kind) at idle (OL or CL is irrelevant for this question) with nearly 20* of overlap? Outside air is passing through the exhaust valve into the header. This is going to skew the readings of the 02s and not give us an accurate reading of what is going on in the CC.

I think Beau (or Bo?) was the only person to understand my question. I think the idle is actually rich because the 02s are reporting a false lean.