My LS6 is running strong, but a little funny....
04-12-2011, 07:42 PM
#1
Le Mans Master
Thread Starter
My LS6 is running strong, but a little funny....
I have a new crate engine in my T1 car. It is running strong in the mid-range to top-end at 7100 RPM, but it is not quite right.
In mid RPM range, around 2500-4000 RPM and less than full throttle it runs kind of like a loaded up two stroke and then as I put my foot into the throttle near full or more and as it crest 4000 RPM the somewhat blubbering exhaust note clears up and she takes off... kinda' like a two stroke, but not as pronounced.
I did get the engine retuned as the crate engine went in two months ago. I don't recall this problem at my first two races at WSIR, but I did notice it my past two track days including this past Sunday at Buttonwillow. I have our biggest local double national race coming up in three weeks at BRP so I want to have this cleared up.
I plan to take the car to RPM Motorsports on Friday and have them refine the tune then. We kept it ever so slightly rich during the break-in period. I will have them look at it too.
It is not throwing any codes.
Any ideas?
Oli
In mid RPM range, around 2500-4000 RPM and less than full throttle it runs kind of like a loaded up two stroke and then as I put my foot into the throttle near full or more and as it crest 4000 RPM the somewhat blubbering exhaust note clears up and she takes off... kinda' like a two stroke, but not as pronounced.
I did get the engine retuned as the crate engine went in two months ago. I don't recall this problem at my first two races at WSIR, but I did notice it my past two track days including this past Sunday at Buttonwillow. I have our biggest local double national race coming up in three weeks at BRP so I want to have this cleared up.
I plan to take the car to RPM Motorsports on Friday and have them refine the tune then. We kept it ever so slightly rich during the break-in period. I will have them look at it too.
It is not throwing any codes.
Any ideas?
Oli
04-12-2011, 09:23 PM
#5
Le Mans Master
04-12-2011, 10:41 PM
#7
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Member Since: Oct 2000
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I get nervous when fuel trim does strange things in the 4k rpm range since melting numer 7 last year. My rpm demonstrated a hiccup in the 4000-4500 before letting go. Transition wasn't quite right.
04-13-2011, 10:04 AM
#8
Melting Slicks
Member Since: Sep 2003
Location: If you don't weigh in you don't wrestle Road America
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Ohm out the plug wires - if it's only happening at "lower" RPM it may be loading up because of that. I've had to replace wires in the past.
04-13-2011, 11:23 AM
#11
Melting Slicks
I'm also pulling code P0343 - cam position sensor high input voltage. Hopefully it's just a bad sensor or bad connection. Oli, I agree plug wires and plugs would be the first place to look and then do some logging with hp tuners.
Edit: just re-read varkwso's post and noticed you said it only runs bad when not at WOT, so maybe that's not my problem.
Last edited by redtopz; 04-13-2011 at 11:26 AM.
04-13-2011, 11:35 AM
#12
Safety Car
^ The front O2 sensors are not supposed to be crossed, the rears are. Some LT headers only use the front O2s but move the bungs farther back and people mistakenly cross them side to side.
The rear O2s just check that the cats are working so on my build I plugged the holes and deleted them with HPTuners... onle less thing to worry about when dropping the H-pipe.
The rear O2s just check that the cats are working so on my build I plugged the holes and deleted them with HPTuners... onle less thing to worry about when dropping the H-pipe.
04-13-2011, 11:51 AM
#13
Melting Slicks
^ The front O2 sensors are not supposed to be crossed, the rears are. Some LT headers only use the front O2s but move the bungs farther back and people mistakenly cross them side to side.
The rear O2s just check that the cats are working so on my build I plugged the holes and deleted them with HPTuners... onle less thing to worry about when dropping the H-pipe.
The rear O2s just check that the cats are working so on my build I plugged the holes and deleted them with HPTuners... onle less thing to worry about when dropping the H-pipe.
04-13-2011, 11:52 AM
#14
Safety Car
If your car is tuned in Speed Density then it doesn't use the MAF or the O2s at all... just the MAP sensor at the back of the intake manifold.
04-13-2011, 01:20 PM
#15
Safety Car
Running speed density is unrelated to use of the front O2s, it only affects whether the MAF is used. Open vs. closed loop involves the O2 sensors. You can run speed density in either closed (during idle/partial throttle) or open loop.
04-13-2011, 02:49 PM
#16
Safety Car
You're right... been awhile since I messed w/ SD. My old cammed Z06 was tuned in SD to get the around town manners back.
04-13-2011, 03:00 PM
#17
Safety Car
You can always retune the MAF as well, to give you the benefits of the OEM hybrid MAF/SD system.
Anyway - Oli - as mentioned, you need a log file to figure out what is going on, with a wideband would be ideal. May be a PITA, but way easier than swapping in a new engine.
Anyway - Oli - as mentioned, you need a log file to figure out what is going on, with a wideband would be ideal. May be a PITA, but way easier than swapping in a new engine.
04-13-2011, 03:04 PM
#18
Drifting
Oli, pick up an innovate LC-1, they're fairly cheap, and theres a hack where you put one of its outputs into the unused-on-the-c5 egr input on the PCM (pin 55 on the blue connector IIRC), that lets you log AFR via the obd2 port instead of a separate cable.
04-13-2011, 03:17 PM
#19
Safety Car
The LC-1 is kind of sketchy (reliability, accuracy). Power AFX seems to be the best bet for a budget wideband. But, if you don't have a HPTuners already, I'd bring it somewhere that knows LS engines, do a dyno pull and ask for the log file and see if they notice anything amiss.
04-13-2011, 03:19 PM
#20
Safety Car
The LC-1 is kind of sketchy (reliability, accuracy). Power AFX seems to be the best bet for a budget wideband. But, if you don't have a HPTuners already, I'd bring it somewhere that knows LS engines, do a dyno pull and ask for the log file and see if they notice anything amiss.