I have a 94 Z28 that I put a CC503 cam in and I am trying to find a way to get rid of the cam surge. It happens at light throttle and around 1500 to 2000rpm. When I first put it in I could unplug my O2's and all of the surge was gone so I replaced them and it is better than it was but still there. I am tempted to run with the o2's unplugged. Does anyone have any suggestions? Thanks in advance

 

Before I get into things to try... do you have tuning and logging software ? otherwise it's only a crapshoot to try and solve the problem. Most likely requires adjusting TB stop, idle RPM, closed TB timing, and transition from closed TPS to main spark tables. Ya need to insure there are no flat spots or jumps in timing from a stop to cruising speed as you progress through the cells in the main timing tables. Also in MAF mode make sure BLM's are good in all fueling cells as you accelerate and maintain cruise parameters. If you go SD then same goes for VE table cells.

 

I do have some logging software and I will try and get a scan tonight. I have to be honest I am a noobe at the tuning process and trying to read it. I have an older scan from before i replaced my o2's if you want me to post it up.

 

Post it up, if it's CSV data or DataMaster .uni I can read it. Would also be good to look at a tune file if you have a .bin format ? If other format maybe someone else on here can take a look. Besides the Moroso CAI, is the TB and intake manifold stock ? Did you de-screen or alter the MAS ? Also have you contacted MadZ28, they may be able to look at a trace and see where the surge and cause is..

 

Yes it is stock and still has the screen in it. This one is after i installed the cam. I will get an updated one this afternoon. Thanks again Here is a link to it http://gh94z28.diinoweb.com/files/

 

For sheets and giggles, richen up the open loop fueling in the affected area to about 13.4 and see if that helps any.

 

What software would I need to get to do that? Like I said I am a noobe when it comes to tuning.

 

I just uploaded my log file from this morning. Let me know what you think.
http://gh94z28.diinoweb.com/files/

I forgot to clear my O2 dtc codes before starting the log. I have had them disconnected earlier this week but they were plugged up in the log file.

 

I was looking for RPM fluctuations coming off of 0 TPS going to light throttle. I noticed your IAC counts are not incrementing when you are at 0 TPS between 12 and 30 MPH. EG: at record 7524 you RPM was at 675 at 27 MPH . Have you changed your Throttle Follower Offset vs MPH table. With speed over 12 MPH at TPS=0% your RPM s/b about 200 over the idle setting. I could not see anything else obvious, cruising along at 2K RPM cycles 3668-5648 (4 mins) everything looked good, BLM's , MAP, O2's were switching normally. Timing was constant at 41* (do you run that high on purpose). RPM did not have any dips or highs. Sorry I could not really see the surge.

 

This is a tune i got from ion when i installed my cam. Well this morning i noticed it bad at about 2000 2100 rpm about 50 55 mph. If i disconnect my o2's all of the issues go away. Should i try another tune?

 

This is covered alot in delail in other posts, but it's clear your tune is good while in open loop, so another tune will likely not help since closed loop takes over and adjusts fuel based on what the 02's are saying which for me resulted in an actual lean surge. I always wanted to try disabling the Long Term fuel trims (BLM's?) and running purely short term fuel trims, not sure if that would lessen the affect but thought it would be worth a try.

I tried everything from new 02's to ultra sealing the exhaust system to valve adjustments and finally realizing no matter what I do the 02's keep pulling fuel (but showing 14.7afr) and making the surge worse. I now run open loop and life is great.

Obvously your case could be different than mine, but check the obvious with the 02's such has leaks, misfire, etc, but if it always gets worse only when in closed loop then your likely running lean due to the cam/02 combo and one of the two will have to go.

I would think by now there would be a target 02 AFR but there's not, if there was maybe have it set to richen up a little in the area's you mention.

 

What could tear up by running it without the o2's plugged up? I know my fuel mileage would suffer.

 

nothing would tear up unless you saw black smoke coming out your tailpipe other than WOT.

 

Same here. That was the best solution possible. You need tuning and logging sowftware and a wideband if yhou really want to nail it down.

If your car is an M6 you are still going to notice some surging at very light throttle.

 

I expected a little surge but this is a little more than normal i think. Thanks