What A/F for Paxton Viper on 8 psi pulley?

[r25558]

So, I took JoeCool's old Viper to the dyno, wanted to check the state of the tune before removing the front cats.....

The tune, done by A.R.T., was rather lean up top (12.5 to 13.0) from 5000-redline, and I dont feel comfortable with that on cast pistons.....

I'm in NO WAY implying that the car didn't leave ART perfectly tuned, but now in my possession, I'm not liking what I see on the dyno.

After pulling the side sills, I could see that ART has removed the second set of cats and welded in straight 2.5" pipe in their place...explains the reduced heat under the side sills...

I pulled off the front cats and replaced the entire piece with the Mopar 3" Midpipe and o2 simulators from Roe Racing....

Basically just ran a 3" straight pipe from the headers to the factory muffler....

I did find the car does not have Corsa exhaust, but rather just Corsa welded on tips...which was a letdown, as Joel thought they had been exchanged.

I say all of this to say that it's time for A/F tuning and I wanted to see what the tuners on here aim for.

I'm thinking target of 11.5-11.8 under boost...still factory cast piston bottom end.

This will all be done on 91 octane fuel.

Any guidance?

I plan to have it tuned tomorrow on the dyno...the Vec software is so basic, I dont think this is going to be very complicated.

 

[EllowViper]

That's were I've dialed in my AFR. I like to keep it in the low 12's until over 5K and then tip into the high 11's. Runs like a ***** ape in the 12's. In the 11's it seems noticably more sluggish. I am ABSOLUTELY tied to my W/M to control detonation so yes I'm living a bit more on the edge than most...but I do not want to leave anything on the table. Just to prove it I gernaded a stock cast piston learning where that edge was...You can also look at the timing and see if you can advance it. That wil lower your AFR too if you have some timing to work with. A real balancing act all in all.

 

[ViperGeorge]

I like to keep my under 12 throughout the RPM range. I believe that DC and Viper Specialty both like to see the A/F below 12, like mid-11s. Better safe than sorry, already detonated one motor that showed 12.2 at its leanest on the dyno. The car will run leaner on the road than on the dyno because of more air being pushed into the intake at speed (or so I'm told). I now use forge rods and forged pistons with lower ring lands to protect them from the heat. I've also added the 08 swinging oil pickup and chrome molly pushrods.

 

[r25558]

I like to keep my under 12 throughout the RPM range. I believe that DC and Viper Specialty both like to see the A/F below 12, like mid-11s. Better safe than sorry, already detonated one motor that showed 12.2 at its leanest on the dyno. The car will run leaner on the road than on the dyno because of more air being pushed into the intake at speed (or so I'm told). I now use forge rods and forged pistons with lower ring lands to protect them from the heat. I've also added the 08 swinging oil pickup and chrome molly pushrods.

I think Mid 11's is ideal for any supercharged/turbocharged car on pump fuel...just curious to hear from the tuners on this board on what they shoot for on the factory bottom end cars.

Will shoot for 11.5 in boost.

Of course A/F is only 1/2 the equation, timing plays just as large a part in the engine living...it's a fine balance...

Thinking 20-21 degrees @6000 RPM?

 

[SquadX]

I agree with what some said above 11.5 in boost. my paxton(tuned by DC Perf) was 11.5 in boost to redline and would sometimes drop to 11.0.
My current paxton, i dont even have a a/f gauge in (soon to be installed) installed but thats how comfortable I am with its tune by DC Perf. Im having it retuned to lean out the rich condition. The gas smell is a killer, especially at WOT with the cats removed.

 

[pteam]

hey Gbatejan,

Which do you like better your supercharged 06 or your 08?

 

[plumcrazy]

Talk to whoever is going to time it for ya. See what he says but I'd say 11,5

 

[99 R/T 10]

I run 12-12.2 up to about 5000, after that, I like to see 12.0-11-7 or add some 110 octane for safety.

 

[ViperGeorge]

hey Gbatejan,

Which do you like better your supercharged 06 or your 08?

That's like asking if I like my wife or my girl friend better. JK

The 06 is my track toy and I like the style of the coupe better than the vert especially after putting the Gen 4 hood on the 06. The 08 vert is the tool of choice though for a nice cruise with the wife. In terms of performance, the SC 06 gets the edge I think. The dyno says 646 RWHP which I would think is higher than the 08 although I haven't dyno'd the 08 and I've not really beat on the 08 either. I save that for the 06 on the track.

 

[r25558]

Car made right at 680whp/623wtq @11.5 A/F at the tailpipe...considering that's about 11.0 at the header...it's more than safe...

Very happy with how it turned out, just need to get some stickier tires....