Okay so as some my know, I've been doing an s/c build on my LS. Today I finally got my tune on and the car running. It's drivable as it is right now but I'm having some issues.

A little about my setup before I go into the issues. It's an 08 LS XFE with 70k on the odometer. It's got a stock exhaust with the exception of a flowmaster series 40 and resonator delete. Stock internals and valve train. It's got an M62 with a 3.1 pulley and LSJ throttle body. 3" intake and 60# injectors. It is being tuned by Trifecta.

So right after uploading the base tune file Vince sent me I was having a hard time keeping it running in idle. After a couple short drives it seems to be ok now. Still small fluctuations but not bad.

After the idle was right I took it out to datalog it to send back to Vince for modification. I noticed I wasn't really getting any power and had a lag at about 3500 rpms in first gear. Every gear after that I get the lag and hesitation around 4000 rpms. I'm also not getting full boost. I was told that I should see around 13psi on a 3.1 pulley. Currently I'm only seeing 9psi max.

I've also got another concern. I have a wide band hooked up in the rear o2 sensor port behind the cat with the cat still intact. During idle my wide band reads 14.5. During a pull with boost it goes rich to like 10.3-10.5. When I let off the gas to let the engine coast back down it leans out to 20. The rich don't concern me near as much as the lean does. When it goes lean, if I give it has it comes right back to normal. It also goes back to normal if I down shift. But it only does it after a boosted pull. If I drive normal and keep it out of boost when I left off the gas it doesn't do that, it stays in the optimal range.

This is my first boosted car so I'm not sure if this stuff is normal or should be cause for concern. I also dont know if it's a tuning issue that will be resolved with further datalogging or what. So I turn to y'all for some help and advice.

 

This is called DFCO (deceleration fuel cut off) it is supposed to do it when your get off the throttle and coast. This is completely normal.

Idling issues are from the large injectors, more tuning should help.

The loss in power I have no idea, stock exhaust isn't a good idea though.

 

Ok cool. I was a little worried. I know the stock exhaust isn't the best, but for right now it will have to do.

Could heat soak cause a loss in power like that? I mean it was hot as hell down here in Texas today and I was also in the process of bleeding and completely filling my I/C cooling system.

 

stock exhaust is bad....having the wideband after the cat is bad...

you could have vacuum issues, or bypass valve issues.

and i have never heard of a good tune from vince for a 2.2 or 2.4 blower car. every one i personally know with his tunes always has issues, and gets better tunes VIA HPT.

 

trifuckta i like to call em..lol.. im going hpt after i rebuild. id get a new header back exahust if i were you

 

Well every 2.2 I've seen go s/c leaves the extra nipple on the bypass valve open and has no problems. I know the bypass valve works though. And I don't believe it's a vacuum issue because all of the vacuum lines are good and tight on where they are supposed to be.

And to get the car running Vince was my only option. Later on I found a shop that will full dyno tune with HPT for $500 including buying credits.

As far as stock exhaust and wideband placement, as I said it'll have to do for now.

 

Having the wideband after the cat is just fine.

Check your bypass valve on the S/C. Could be why your not seeing the correct PSI. Whats your vacuum at idle?

Idle issues and not full boost could be vacuum leak.

 

I have a 0-30 full sweep boost gauge. It doesn't go below 0 so that's where it sits at idle. I'm not real sure though where it would be a vacuum issue cause everything is hooked up good.

 

is your car manual or auto.. and auto needs both lines on the bypass hooked up a manual only needs one. vaccum issues could be anything. any line at all. bad crankcase venting could even be an issue. but i can already tell that you are the type to ask for help then tell people that their advice is wrong so i am going to bow out of this thread.


also, IMO a wideband shoud NOT be after the cat in any way shape or form.

 

Also, the idle seems to have worked itself out. After a couple of pulls it now seems to idle better an stay right around 800rpms at idle.

 

Wow. Suit yourself. I don't expect much less from this forum anyway. Only a handful are actually helpful.

Anyway, tomorrow I'll start checking vacuum lines and making sure everything is on tight and there are no cracks. The car is a manual also.

And as far as the wideband placement goes, performance shops tune with a sensor in the tail pipe, so I think after the cat will be fine.

 

Wrong. Other nipple is for boost controlling that only LSJs can do. Im an auto and i dont have the other hooked up at all.

Wideband works fine after the cat too. I have mine after my cat.

 

Wideband really should be pre cat but it doesn't sound like the cat is really affecting it much. The lack of boost could possibly just be because of how hot it is. That would also explain the lack of power. You may have a slight boost leak but I'd say heat is the main culprit. Heat and humidity absolutely kills performance on the sc'd cars. Enough heat soak and it will feel as slow as it was stock.

 

Ok, so I checked the vacuum lines. The PCV line from the valve cover to the intake was a little loose so I got that tightened up. One thing I was thinking of though, when I did the install I had a guy helping me. I asked him if I needed to cut the gasket to allow the crank case vent passage from the head to the manifold to be open Nd he told me no. So could by not cutting the gasket would that cause these problems?

 

Haha who told you that? I don't understand why people do stupid **** like this when doing it right is as easy as a $5 part and a 2 minute weld.

 

I know it wasn't directed at me, but my wideband instructions said that I needed to position the sensor at least 18" away from the head and no more then 36" away from the head. For me there was no room to mount it other then behind the cat. Plus, I have to have my cat for state inspections and I'm not risking a federal felony by removing it.

 

I understand that, im not saying get rid of the cat I'm saying to get a bung welded in pre cat would cost $20 with parts at any muffler shop. Is saving $20 really more important than possibly blowing an engine?

 

Well for me to do that I would have had to drop the down pipe and take that to the muffler shop. And I've only got the Balt. So I can't drive it without the downpipe. Sure it's cheap, but the margins that the wideband will be off behind the cat are fairly minimal as opposed to before the cat. Besides, where do you think the performance shops stick the sensor when tuning cars that don't have a wideband installed? Just saying.

 

I didn't read all of the post but you did use different spark plugs with a different gap, correct. I really doubt with the extra going into the engine the stock plugs will work. That could be why your lossing power and explain the hesitation.

 

^^^^ this. People shouldn't mod cars that don't know what they're doing. The 36" is for a turbo car. I have mine right in front of the cat. Weld a bung in and call it a day.

 

Those tailpipe "sniffers" are notorious for being inaccurate though.

 

Yeah I did use one step colder plugs.

And if they are accurate enough to time 700hp muscle cars, I would assume they are accurate enough for our cars.

But this has turned into a debate about afr sensor placement and that's not what this is about. This is about why I'm having The problems I am. Afr sensor placement has nothing to do with that.

Now I've got a local friend who sc'd his 2.2 and he's not having these problems and he's on stock exhaust with a 2" cat back. So exhaust isn't the problem either.

 

ok ill jump back in. and once again say check all vacuum lines and read read read read read. it could be heat and humidity and lack of proper cooling for you, but it still could be a vacuum issue. and YES IT COULD BE your wideband placement.

as far as the PCV hole in the head, having it blocked is fine as long as you have the VC nipple being either vented, or plumbed to the intake seeing atleast some vacuum to evacuate the crankcase. a pressurized crankcase COULD cause this type of issue too. has your dipstick blown out?

tuning a car with a wideband post cat can change afrs as much as 2 whole points. ask me how i know. the sniffers that shops use and the programs they use are DESIGNED to be used post cat. any tuning shop will or at least should ask you if you have a cat or not before tuning your car on a dyno. it makes a big difference.

 

The dipstick hasn't blown out. And the nipple on the valve cover is plumbed to the intake.

I drove it a bit this morning and noticed that its only bogging when boost kicks in, if I gradually raise the rpms without going into boost, it drives just fine. However if I floor it and go into boost, at 3500 it bogs down. Almost like the fuel maps are wrong and it's getting too much fuel under boost. It's also running incredibly rich under boost. Somewhere around 10.0-10.3.

 

False. Your seeing a leaner AFR than your engine is actually getting. So if your seeing 10.3-10.5:1 your engine is actually seeing around 9.5:1. This is incredibly too rich, even 10.3:1 is way too rich, and I bet it's the reason for the dead spot your feeling.