Removal of VEC and install of SCT tuner

[msdnga]

We dynoed a 2005 RC SRT 10 today, zeroed out the VEC 3 and installed the SCT. I'll let Sean elaborate for you.....

 

[hemifever]

I put a preliminary tune on in place of the VEC 3. We kept a conservative timing curve of only 32 degree's per my friends request. I think one of the only gripes about the VEC was the fact it had a terrible a/f and power curve from an initial punch at 2500 rpms through about 4000 rpms. a/f was VERY lean, around 15 recalling from memory and a nice tq dip right off the bat. After it recovered from the lean condition it was difficult to command the fuel to the desired ratio. So we saw a lean condition followed by a really rich condition to where it finally leveled off about 4000 rpms.

With the SCT tuner, the power dip was removed and a/f was immediately in our control at the 2500 rpm punch. The power curve was nice and linear from 2500 on up and a/f was exactly where we put it.

Peak power was pretty much the same but we had a/f where we wanted it. And again, we only hit 32 total timing above 3500 rpms. 36 may have gotten us another 10 hp but it wasn't something my friend cared much to see.

What the VEC couldn't do was provide a nice timing table for all ranges of driving. The initial part throttle timing table could really be improved but we'll see how much driveability tuning we really get to. The comments were that it had improved low end power and really smoothed out the transition to WOT. After a few days of driving, the part throttle power will increase a little and if he ever wants to tune on that, there's a good bit more to unleash.

 

[msdnga]

Someone asked me about this mod in a PM...this is in no way a stab at the VEC. This is just to clearly explain what can be controlled by the SCT tuner in the right hands.

 

[TNVIPER]

Lean torque killing condition followed by rich over compensating AF....yes...exactly my dyno/AF chart.....SCT might be the way?...

 

[ZCx]

does the Roe SCT tune run the same as the VEC. as far as the timin tables, a/f, etc. ????

 

[mauiSRT/10]

This sh#t just keeps getting better!!!! :burnout: I am afraid to ask how much better you guys can make my truck!!!:burnout:


patrick

 

[msdnga]

The SCT and the VEC are not the same. The SCT changes everything by flashing custom parameters to your PCM, the VEC modifies the stock pcm signals. Someone running Roe's (Torrie McPhails) SCT tune will have to answer that for you.

 

[FlyingLow]

I'm going to have my truck tuned by MSDNGA with the SCT sometime in the next couple of weeks. My current tune is with a VEC3 and was tuned by Sean Roe himself. I also think mine will be the first STS QC that Marty is going to try and tune. I will post up the results when they are done. I would like for Marty to do a before and after on his dynos so the numbers to compare are more consistent.

 

[Roe Racing]

The initial lean area on the newer engines (whether it's stock or modified) is the PCM's wide open throttle timer function that holds closed loop for approximately 1.5 seconds. Generally, you can get around it when a VEC is programmed to set the O2 output voltage to the PCM at stoichiometric voltage, which is the voltage the PCM adjust the fuel pulse to attain (if it sees a richer mixture, it decreases fuel injector "on" time accordingly, hence the "closed" loop).
The SCT is a better option, no doubt about it. The only problem, it wasn't available until a few months ago. The VEC was developed in 2002 for the '96-'02 Viper Supercharger kits. I'm very glad to see the technology improving and making better tuning options available. It's good for everybody.

Regards,
Sean

 

[mmmmtorque]

This sh#t just keeps getting better!!!! :burnout: I am afraid to ask how much better you guys can make my truck!!!:burnout:


patrick

I had my truck SCT tuned yesterday and was able to make at least two improvements.

-Cleaned up the lower RPM HP/Torque curve: During the 1.5 second delay in going to open loop, the PCM would pull timing and fuel and thus resulting in an ugly transition into open loop. It is now a smooth throughout the entire pull.

-Improved partial throttle response/performance. Its something you have to experience to appreciate the improvement. Daily driving the truck, you get used to the irregular performance at partial throttle and in the lower rpms. Its not a night and day difference but definitley noticable.

I plan to keep the VEC3 installed and use it for my nitrous activation, windowing, tune, etc...

 

[Marc T]

I had my truck SCT tuned yesterday and was able to make at least two improvements.

-Cleaned up the lower RPM HP/Torque curve: During the 1.5 second delay in going to open loop, the PCM would pull timing and fuel and thus resulting in an ugly transition into open loop. It is now a smooth throughout the entire pull.

-Improved partial throttle response/performance. Its something you have to experience to appreciate the improvement. Daily driving the truck, you get used to the irregular performance at partial throttle and in the lower rpms. Its not a night and day difference but definitley noticable.

I plan to keep the VEC3 installed and use it for my nitrous activation, windowing, tune, etc...

Ditto on the above, I am also experiancing much better gas mileage!! :rock:

 

[tidnab]

Ditto on the above, I am also experiancing much better gas mileage!! :rock:

if you're getting better milage you need to push the pedal on the right harder ... that'll fix that 'problem' you're having :rock: :elefant:

 

[Marc T]

if you're getting better milage you need to push the pedal on the right harder ... that'll fix that 'problem' you're having :rock: :elefant:

I do, just not as often anymore since I got my first ticket in 9 years!!

 

[mauiSRT/10]

I had my truck SCT tuned yesterday and was able to make at least two improvements.

-Cleaned up the lower RPM HP/Torque curve: During the 1.5 second delay in going to open loop, the PCM would pull timing and fuel and thus resulting in an ugly transition into open loop. It is now a smooth throughout the entire pull.

-Improved partial throttle response/performance. Its something you have to experience to appreciate the improvement. Daily driving the truck, you get used to the irregular performance at partial throttle and in the lower rpms. Its not a night and day difference but definitley noticable.

I plan to keep the VEC3 installed and use it for my nitrous activation, windowing, tune, etc...

The open loop part.......when do you feel/notice that when driving ie, what mph in what gear??

Partial throttle response/perf. Again when would you notice that? I know with my truck in first gear going slow and letting off the gas the truck wants to jerk around a lot......I figure its how mine is setup, 4.88's, no cats, DC stage two computor etc.....all make it very torquey.

Of course your gonna keep the Vec 3...............your sig says "mods, got all of them".........You really do!!! LOL

Great post Sean...........This SCT tuner is really turning out to be something special.

patrick

 

[mmmmtorque]

The open loop part.......when do you feel/notice that when driving ie, what mph in what gear??

Partial throttle response/perf. Again when would you notice that? I know with my truck in first gear going slow and letting off the gas the truck wants to jerk around a lot......I figure its how mine is setup, 4.88's, no cats, DC stage two computor etc.....all make it very torquey.

Of course your gonna keep the Vec 3...............your sig says "mods, got all of them".........You really do!!! LOL

Great post Sean...........This SCT tuner is really turning out to be something special.

patrick

The delay is there regardless of gear...typically feels like bad turbo lag. Power is smoother with the SCT tune.


Partial throttle is noticed in day to day driving...Its not a huge difference but a very noticable one. I will have to get the dyno results printed out and can show the difference on paper.