Surging Condition

[Shep927]

I have an '04 Cobra that has a 2.80 upper pulley, Bassani X and Catback exhaust and JLT CAI. We used a Predator to tune her last Fall after the pulley swap was done.

The performance is great at anything over 2000 rpm, but once you are cruising at 36-40 mph and the rpms are around 1800-2000, the car surges and feels like its misfiring. It's noticeable through the exhaust note as well. Touch the gas or downshift and everything smooths out again.

At the advice of a friend who's done a lot of tuning, I did a data log and looked at the timing. In that 1800-2000 rpm range, timing is around 46. Once the rpms go above 2000, timing drops back to 25 and the engine smooths out and runs fine.

I spoken to a couple of other folks who've had the same issue with their Cobra's. One actually spent the time to put together a custom tune and drop the timing back in the 2000 rpm curve, which totally resolved the problem.

I don't see any way to do this with the Predator, as there are no timing selections available for under 2000 rpm. Other than dumping the Predator and going for a custom tune, does anyone have any suggestions?

Thanks.

 

[pr0minence]

I had a surging condition a while back. It turned out to the air coming in from my cold air intake was swirling around the maf and it made it surge. I ended up buying a different cold air intake and it cured my problem. I actually went to a JLT 12" from the Kenne Bell CAI. Might check or maybe even clean your maf since you put on a new filter. New filters can make them dirty due to excess oil and the way the maf is positioned effects it as well. My surge was very similar, it done it at cruise speeds only and if I let off or accelerated it seemed fine. Hope this helps.

 

[jad0414]

Surge

Shep927, I also have the weird surge, and am looking on here for suggestions. I have about the same setup as you, pullies & JLT cold air, exhaust, ect.. I was told to try my stock air box, or get a short stack cold air that keeps the filter & meter under the hood. I'm going to do one or the other this weekend-I will let you know, or if you find anything out sooner, let me know! Thanks!

 

[Shep927]

Jad - I've checked everything else on the car and found no problems. The surge appeared immediately after we did the pulley change and loaded the Predator tune, so we're definitely suspecting that. The car's going to my tuner tomorrow. He'll load the factory tune back and then use a tuner that allows full adjustment under the 2000 rpm range. He's done this on a few cars so far and it's solved the problem every time.

I'll let you know how we make out.

 

[jad0414]

Surge

Please let me know what you find! Jason

 

[Shep927]

Jason - Just got her done and went out for an hour+ ride. Can't believe its the same car! Cruises right along between 1700-2000 rpm with no issues at all. Bottom end power is way stronger and the supercharger kicks in much sooner.

Used a Sniper instead of the Predator. The Sniper lets you play with timing below the 2000 rpm curve. Took the timing back to 35 from 47 in that range, drove it a bit and still had a bit of a surge. Knocked it back to 32 and that turned out to be the sweet spot.

We checked the timing with the Predator tune and again after we put the factory tune back. The results were the same, so its Ford that's putting the high advance in there, not Predator.

Good luck with yours, hope this helps.

Shep

 

[jad0414]

Surge

Shep, thats great info-I will try doing the same since you had good results! Jason