Vortech SC stock pulley, around 4k im getting hesitation from the motor. Its like a shudder, bucking feeling. When the engine sits for 20 minutes, theres no effect, but it gradually gets worse with heat soak. Plugs are stock platinum.
This was on the dyno tring to get the utec tuned. Cant get past 4k. A/F and timing are fine. Utec is set to speed density-map sensor. No other changes to the motor. Take the glimer belt off (SC off) and the car runs to redline no problem. It's only under some initial boost. UTEC setting problem?
No CEL.

Thanks.

~Dv8

 

Definitively the tune. My car did the same thing with UTEC. At your current boost level it shouldn't do that.

*never fixed it, upgraded ems.

 

your plugs are toast.. please run 1 step colder

 

+1 agree with doug. If A/F is fine on your wideband, then its spark. I have noticed several people now with spark issues with the UTEC by the way. Changing plugs will likely fix your current problem, but keep in mind that the coils being driven by the UTEC may not be getting the power they need, esp at higher boost levels. An ignition amp may be the final solution for your problems. Either that or a different EMS.

 

Spark blowout. Take dougs advice.

 

For refrence, I was on the dyno last night with 6 brand new NGK iridiums 2 step colder (7 heat range) plugs gapped between 25-30 in anticipation for this vortech. This morning thinking it was spark related too, I swapped to the stock platinums that are gapped between 40-45. At 4k warmed up it still starts missing, shuddering ETC.. From my nitrous experience it feels like spark blow out too, but seriously, shouldn't this be more common? Ive search all over and cant find anyone else with this issue.

The stock platinums have a heat range of 5, my iridiums are 7, that should be a perfect heat range. Should i open the gap on the 7 to 35 or bigger?

Is it really possible that I need an ignition amplifier? That just seems odd.

~Dv8

 

plugs, coils, or EMS... Since the car works fine with the UTEC removed, it's got to be something in either the fuel or ignition system. If A/F is fine, then only ignition is left. One of the UTEC's transistors that generate the ground circuit for the coil may be out of spec. Maybe it has a very short interval by default? TXS has great customer service - you could ask them to swap units out.

EDIT: MAKE SURE YOU PROPERLY GROUND THE UTEC AND STOCK ECU CHASSIS.

 

I used factory gapping with my 1 step colder NGK plugs and have had no issues.

Maybe the gapping is the problem?

 

why are you using 5 or 7? 5 is going to burn up too quickly and 7 is going to give you poor performance off boost... i don't understand why you wouldn't get 1 step colder

 

Thats fine I'll try 6's. G35's come from the factory with 4-6, i pulled 5's out of my car and decided that 7 was the safest all around heat range for the app. Vortech doesnt even reccomend a change in heat range. I use 8's in my other 3.5 DIS nitrous motor without issues.

Like I said, Ill try 6's, just sounds strange to me that all this is a heat range problem.

Ill report back.

Thanks,

~Dv8

 

It doesn't sound like a heat range issue to me either, 5 or 7 should run fine (though I would recommend 6 for your application).

If it is not plugs.... have you checked your cel codes? See if there is anything crank position sensor or cam position sensor related. Is the tach solid when it is missing / breaking up, or is it doing anything odd such as giving a quick bounce to 0?

 

Iridiums or Platinums? I ordered the NGK iridiums LFR6AIX-11.

 

Iridium

 

I've had a similar problem after going FI. And, my tach bounces all over when it bucks. Usually a few RMPs up. Only a few RMPs down. Never all the way to zero, though.

Two common denoms: Happens more after car has sat. Cold. No problems second or third trip during the day. And, as odd as it may sound, happens more when near empty. Crap in the tank???

 

Since you have Utec then do some logging... your map sensor maybe reading your boost wrong and you are hitting your boost limit cutoff or something..

 

Ill check the ecu for codes.

The tach follows the engine, after 4k when it hesitates/misses the needle slightly moves back then forward; like difficulty firing.

We will data log on monday when I get it back on the dyno. We then will send the logs off to Txs for review.


Thanks

~Dv8

 

Have you properly grounded the UTEC and stock ECU? Coils are driven by transistors to ground... Didn't the UTEC have this issue reported by several before that was resolved with the new ground wire plug? Or was that another issue?

 

Right Click Download.

rev1

rev2

~Dv8

 

Hmp. Mine doesn't do THAT.

So, yours shuts down after 4K or was that you just backing off?

 

Floored it starts doing that right before 4k, I let off at around 4500. The engine shutters, and the tach needle follows it back and fourth and so on..

~Dv8