schpenxel

No problem. There's plenty of room to get it in prior to the cats.. it looks worse than it is. You'll have to cut off some of the heat shielding. What I'd do is remove the heat shield in the area you want the sensor installed so you'll all but have it ready to weld for the exhaust shop. Makes it easier on them and probably cheaper for you.

Amazon has sensor bungs that are straight or cut at a 45* angle. I think I used a 45* angle bung in the picture

hippy

A friend of mine is welding it for me, I already purchased bungs so now I just have to wait for a good time to get it done. It'll happen when I can drive the car more than 1 day at a time.

mvvette97

I was wondering the same thing about having the wideband before or after the cat. So I did it both ways on my chevy silverado. After tuning it with the sensor before the cat I was reading 12.8 afr at wide open. So then I removed the rear o2 after the cat and put the wideband in there. Tested it for days and it read a constant 13 afr. So from what I found was after the cat the widenad read .2 leaner than before the cat. I also did the same test on a ford crown vic and had the same results. I was also using an AEM wideband. So I just tune to 12.5 to 12.7 after cat to get an actual of about 12.8 or 12.9. So not really alot different like one would think. So just remember the wideband will read just a tad leaner than you really are. Going to be tuning my 07 vette pretty soon and I also put the widenand after the drivers side cat. Not sure what software you are using but I use efi live

schpenxel

That is interesting to hear.. I always put mine before cats just to be sure it's not making any difference, but it sounds like the readings you're getting before/after are quite close, only 1-2% difference. Good to know.

mvvette97

Yea thats what it seems on both cars anyway. Just got home from doing some tuning on my vette and was really shocked how far the tune was off. it;s stock with 19k on it other than an axle back exhaust. Trims were in the plus 6 range. Got them down to about -2 so that's good. Then on the wideband it was running 12.2 so really near 12 afr. Have it about 12.9 on the wideband so should be 12.7 if it's like the other cars I have done

schpenxel

+6 isn't that bad considering GM has to use one tune for hundreds of thousands of cars that ship all over the world. Different elevations, etc. I've seen tuners send stuff out wayyyyy worse than that

Sounds like you're getting it dialed in though

mvvette97

No it isn't horrible but I would rather see them in the negatives. the bad part of being in the positives is that how ever much positive you are running when going into power enrichment mode that is added to the PE. So say it's running +6 trim entering PE then that is added to the already rich commanded setting. I didn't know this for many years but that's why it's always best to beat 0 or just under on the trims. i was chasing my tail for a long time with the wide open tuning on my truck when a guy on efi live forum looked at my logs and seen my trims. After getting them around -2 or so my commanded PE came right back around where it was commanding.

schpenxel

I know, I do quite a bit of tuning (and I'm a mod on the HPTuners forum)

Or you can go the 2008 route and just run in open loop.. Or the 2011 route and disable LTFT's altogether

mvvette97

The 08s are open loop tuned? I didn't know that. Wonder why they did that? I love this tuning stuff. Just when I think I have it all figured out I learn something new, haha

schpenxel

I meant circa 2008 tuners thought they were awesome if they put cars in open loop and left them that way.. I'm not sure if that was the exact year, it was more of an unfortunate trend that went on for a few years... then they started enabling STFT's but leaving LTFT's off, which at least has the advantage (or disadvantage depending on how you look at it) of not affecting PE fueling.

GM def. hasn't shipped any cars in the last few few decades that run in open loop on the factory tune

mvvette97

I got ya now. That makes sense now.

truth.b

Can someone breakdown why +6 for the LTFT (long term fuel trim) is not as advantages as a 0 or -2. Also I'm assuming that PE stands for Power Enrichment which is what happens when you go WOT?

schpenxel

Positive fuel trims are carried into PE mode, meaning a +6 will add 6% more fuel to however much fuel it thinks it needs to inject while you're in power enrichment mode. It can make you run 6% richer then you intend to be running

Negative fuel trims are not carried into PE, so people like to try to get them every so slightly negative so they don't have any affect on PE fueling.

Something weird, lately I've noticed that I sometimes do show 1-2% negative FT's while in PE.. and I don't know if it's just a weird quirk of what's being displayed or if it's actually factored in.

Some posts on EFI Live's forum say that E40 and E38 ECM's actually do factor in negatives, but other says they don't.. so who knows. I know everyone says they don't, but has anyone done the math to be sure?

mvvette97

I have wondered that as well but all I can say is that yesterday while tuning my c6 i was at one time -1 trims and them made a backwards adjustment and got my trims in the -6 range but my pe on the wideband reading did not change. The thing I did notice is that after a flash it takes 2 wide open runs for the pe to become accurate. Seems the first full throttle pull is always more rich. After that all the pulls are consistant. Maybe it takes the pcm a bit to know what it's doing after a flash.

schpenxel

Someone on the HPT forum actually ran an ECM (E38 I believe) on a simulated engine where he could control all the inputs precisely. Basically it was an Arduino board that he programmed where he could control MAP, ECT, Throttle, etc. by potentiometers on the board he setup.

After a flash, even when he held every single input exactly the same, injector pulsewidth still changed for the first little while (can't remember how long, but it was long enough to really matter). It's pretty weird and I don't think we ever figured out the true reason of WHY it happens, but you're right.. it does happen

I usually log intake valve temp and once it gets back up to the normal'ish range the rich after flash thing dies down.. though two WOT runs probably takes care of that real quick

mvvette97

Something I was wondering is after flashing the e38 do the fuel trims need to be reset? I know it seemed to worked best to reset them on the ls1 ecm but I thought I read on the e38 that the trims are reset during a calibration flash. No Idea if it's true. I do reset them like I always did on the older ecm just because it seems like the trims will come around faster. Maybe it's just in my head or an old habit, haha

schpenxel

They are reset during the flashing process (but it can't hurt to do it anyways)

truth.b

So I'm slowly learning about tuning. At this point are there any note-worthy differences between HP Tuners and EFI Live? My goal in the distant future is to lightly tune my Grand Sport.

BTW: I'm an engineer so I'm not afraid on diving deep in the technical aspect of learning how to properly tune.

schpenxel

EFI Live seemed to be concentrating more on the diesel market there for a while

The only significant differences between the two were EFI Live could work with virtual VE coefficients where HPT could not, BUT HPT released new software a few weeks ago that makes them even on that front

The other thing you might see is EFI has serial inputs for external sensors but HPT is coming out with a solution on that as well. They have 0-5V inputs of course on HPT that you can connect a wideband/fuel pressure sensor, etc. up to

I've been happy with HPT but I'm sure others are happy with EFI too. If they had been the same price I'm not sure which one I would have picked... but since HPT was cheaper and the capabilities were basically the same, I went with HPT

mvvette97

I can't speak for hp tuners but I love this efi live. I downloaded a demo of hp lastnight and to me it seemed very confusing compared to efi. That said i have been using efi for years now and have it figured out. It's probably just what you get used to. I just got done tuning two silverados tonight. One was mostly stock just doing a cleanup on the tune tweaking the tranny some and the other was a heads and cam 5.3. It was a bit more of a task getting everything dialed in because of the healthy cam and all but got her idling like a champ at 700rs and trims all perfect. Fixed that terrible idle hunt that you hear on alot of cammed cars. It was pretty fun