Those running vec 2 got questions

[SVIPER`]

I bought a viper that has a vec on the car. I have been screwing with it since i got it. Im having a problem with tip in. The second you floor the car it goes instantly lean then the map clears up. This only happens in 1-3rd gear. Fourth gear is not really an issue. I spoke with sean roe and he seems to think i need to send the box back to have it updated for air temp correction and a wot problem that 04-05 had. I also spoke with a shop in Nevada and they said that I should just get rid of the vec because ill have problems with it till i sell the car. I have has a lot of experiencing tuning cars with fast systems/big stuff and DFI. The vec isnt as diversified as the other boxes but if i can get it to work i dont really care.

Your thoughts?
The car has a paxton kit on the car that makes 663rwhp.I dont plan on taking it past that point

 

[plumcrazy]

mine has been on for 2 years i guess now and not one single problem cause of it. when i install the paxton this winter im keeping it and expect the same results from it.

if sean says to return it for an upgrade, id do it. the guy is very helpfull and im sure he can fix the problem for ya.

hang in there.

 

[Joseph Dell]

The tip-in is by far the hardest part of tuning. Most cars I've seen lean out a tad at the tip in. But here's the deal... if your car leans out but you aren't under boost, big deal. and if it 1-3lbs (which it would be if you tip-in at 2-3k RPM) then you have nothing to worry about. Sounds a little more like a tuning issue than a VEC problem, although the VECs are known for a few quirks.

Updating the firmware on it can't hurt. BTW - how is your #10 spark plug? check that for ultra-richness... that too was cleared up w/ a firmware update.

JD

 

[SVIPER`]

forth gear the cars a/f is at 10.8 from 3k-3,500 same rpm 1-3rd gear the a/f is 20.0 so its a pretty big problem..seems vec 2 related to me. Any other vec 2 thoughts?

 

[KenH]

What are you measuring the A/F with? Does the car stumble or have any other symptoms when this occurs? Have you done any logging with the VEC2 to see if the TOT Fuel line shows any odd transients when you see the lean condition?

 

[viper spray]

Mine works great with my Paxton.

 

[Jack B]

KenH:

there is no fuel pressure monitor on the viper, you have to go aftermarket. Whenever there a change in volume at high flow you will get a tranisent fuel pressure condition. It looks sinosidal and will depend on the physical attibutes of the system. On my car when the second nitrous stage would hit it was very pronounced. I added a fuel pressure damper to stop this anomoly, I believe the mfg was Marin.

After the fact I found out this is very common, therefore, the need for an off-the-shelf fix.

 

[KenH]

KenH:

there is no fuel pressure monitor on the viper, you have to go aftermarket.

Yeah, I was just referring the injector pulsewidth signal to the injectors from the VEC2. If it went flaky at 3000-3500rpm, I would suspect the VEC2 as a possible culprit, but if it was steady, then I would look for external reasons for the A/F to go lean. You idea of a transient on the fuel pressure seems to make a lot of sense.

What I couldn't reconcile is why only 1-3rd gear was affected, but not 4th. The only real difference I would think from a systems standpoint is the general amount of g-forces to the system being higher in 1st-3rd which I could image aggravating a fuel flow issue or possibly a poor electrical connection.