I have an 05 350z, with headers, cat-back exhaust, ssv manifold, cai, and just recently I had the turbo xs installed and tuned at Japtrix. The car ran great for the first week and I deffinatley noticed the difference. Now my car feels sluggish and I'm having a hard time keeping up with stock Z's. I have no check engine light and no uncommon noises. If anybody could tell me what they think is wrong or if they've had the same problem I'd appreciate it.

Billy

 

Try resetting your factory ECU (battery or pedal method)

 

What's the pedal method?

 

And why would you not return with the car to Japtrix?

 

DEAR BILLY if you are not happy with the way the car is feeling please call john and we will dyno test it for you no charge .

 

Japtrix has a good rep.......I am sure if you bring it to them they will make things right.

 

A utec is not a good way to have a naturally aspirated Z tuned at all. The reason why is there are 3 to 6 maps that your car will flip back and forth through all the time. When you have a utec tuned, it will be on one of those maps. When the temp. and humidity change, so do the maps. Now you have a car that was tuned on one map correctly, completely change maps and run like crap. The ONLY way to tune a VQ NA correctly so it runs perfectly all the time is with either A) A full standalone or B) a stock ecu reflash (UpRev or any other company that can reflash your ecu)

Don't waste time with tuning a utec NA unless you have all the maps flashed to the same map, if you are going to pay for that to happen well then it's the same price almost as having it tuned with UpRev or a reflash altogether.

 

Moved...

 

sounds like a case of the mondays

 

What? Where did you get these info?

First, most NA Utec tune uses the MAF pullup/pulldown so it is just basically scaling the ECU.
Second, Utec dont change from Map to Map unless you flip the switch or intentionally switch to another Map.
Third, Utec dont care about Temp/Humidity unless you are tuning using Speed Density. This is why most NA uses MAF Pullup/Pulldown since the MAF already incorporate the intake temp.

If you are boosted then yes you are most likely going to use Speed Density but your Map will not change switch to anther Map when temp changes... Utec has a Temp Compensation table that Utec uses on Speed Density.

Have you tuned the Utec or even own one? Did you get all this info from Jeremy? I doubt it coz he knows Utec very well. You are right though that a flash is better than Utec for NA.

 

^^ exactly why the UTEC isnt very good for NA tunes. since its just scaling the stock ecu values, the stock ecu wants to re-scale them.

for a NA only tune, reflashes are the best bet.

 

I think you missed his point, he said the stock ECU will switch maps not the Utec, and since the utec doesn't change along with the stock ECU maps, the Utec is tuned for one of the maps not all of them.

 

My bad but I didnt see him say stock ECU so I thought he's talking about Utec. I was thrown of by his last paragraph that to properly tune Utec that it needs to flash all map then he compare its cost to an ECU reflash tune. It is not the stock ECU changing map that is causing the main problem because if the stock ECU start changing it's timing because of high IAT, coolant, knock..etc the Utec is basically just scalling the value of what the ECU wants to run. If the ECU change to its High_Detonation Map and start pulling timing then that is OK since there is knock detected or if the ECU start pumping more fuel because of the colder temp then that is still ok. In the end it is basically scaling the ECU values.

I think the main problem is when the ECU try to re-learn itself and start making adjustment and basically voiding out what ever you have changed. I got to look at the manual on Maf Pulldown/Pullup (I mainly tune using Speed Density in Utec) but I believe the Utec has full control of the timing so the ECU can change its timing all it wants and the Utec will still have full control on the timing side. I believe it is the Fuel Table that is getting changed when using a Maf pullup/pulldown.

 

The UTEC will make the car think the MAF is dirty. The stock ecu has a base fuel schedule inside of it. You can not keep the utec in tune without changing this.