Paxton Fuel Tuning

[GR8_ASP]

Anyone with a Paxton done any fuel tuning? If so I would appreciate any helpful advice short of buying a Vec2 or a whole new fuel system. As posted previously my a/f ratio starts to rise after 5000 rpm and gets too lean for my tastes after 5700 rpm.

I do measure fuel pressure and it has the following characteristics:
ignition on engine off 50 psi
- engine idling 55 psi
- at +0 boost pressure jumps to about 75
- as boost rises the pressure rises to just under 100 psi (95 psi at 5500 rpm, I have not looked at 6000 rpm)

 

[BigCarrot]

A competant shop can tune it for you. You really need bigger injectors though. The stock injectors are really already stressed with the Paxton, so when you start adding more power, it just makes it worse.

 

[VIPER D]

you could put the cats back on



vd..

 

[Joseph Dell]

Actually, with an FMU (Which is what the paxton kit uses), it is tough to really tune the sucka. you can't dial-it in like you could with a VEC2 or an alternate fuel controller. I've been tuning several cars with the VEC2 as of late (all gen II's) and have been extremely impressed with it. If that were a fuel curve of a car with a VEC2 on it, we could clean that up to near perfect in about 2 dyno runs.

It isn't that bad, actually (though the scaling makes it look bad)... but i wouldn't wind it up past 5750 on a hot day...

JD

 

[BigCarrot]

JD it also comes with a Split Second box, so you have some room.

 

[VIPER D]

Actually, with an FMU (Which is what the paxton kit uses), it is tough to really tune the sucka. you can't dial-it in like you could with a VEC2 or an alternate fuel controller. I've been tuning several cars with the VEC2 as of late (all gen II's) and have been extremely impressed with it. If that were a fuel curve of a car with a VEC2 on it, we could clean that up to near perfect in about 2 dyno runs.

It isn't that bad, actually (though the scaling makes it look bad)... but i wouldn't wind it up past 5750 on a hot day...

JD

on cast pistions and that much hp you will 1000% have problems. Its way to lean. If it had bullet proof internals then you would be fine but you don't. Then people will blame paxton for a bad product. when its just a bad tune.

vd..

 

[VIPER D]

JD it also comes with a Split Second box, so you have some room.

he needs more fuel the split sec only does timing not fuel.


vd..

 

[DSR207]

Get Vec2...it's a great complement to the Paxton kit

 

[BigCarrot]

Get Vec2...it's a great complement to the Paxton kit

As it comes from Paxton, it doesn't, but with some modifications it does control fuel. Ask Doug about it.

 

[Viper X]

Viper SRT,

Too bad you're in Michigan. John at West Coast Viper ( Murietta, CA) tuned mine using the factory computer. Air / Fuel is a constant 13:1 from idle to 6200. Mileage is about 13 all around, 18 - 20 on the road with 3.07's. rwhp is now about 750 at only 7 psi. Way more power than I can use, extremely drivable. You should really call John.

Good luck,

Dan

 

[DSR207]

Viper X, BC or Viper D, any worries at all about the cast pistons, I kept mine at only 678 rwhp for that reason, I can go up to 750rwhp easy, but Paxton and many others advise against it, what do you think ?

 

[VIPER D]

13:1 all the way thru. wow sounds like a time bomb. Either you are mistaken or you have forged internals or its a time bomb.


choose one


vd..

 

[BigCarrot]

Yeah, 13:1 is no bueno with a blower car! DSR207, mine is tuned back to right around 700 to make it safe. They said they could make a lot more power, but I do not want it flying apart. I've been there and done that with my 01 RT/10, and I don't want it happening again.

 

[DSR207]

Thanks BC
Mike

 

[VIPER D]

Viper X, BC or Viper D, any worries at all about the cast pistons, I kept mine at only 678 rwhp for that reason, I can go up to 750rwhp easy, but Paxton and many others advise against it, what do you think ?

All I know is that I spent a whole lot of time to tune in my bad boy, The tune was based around a 10.5 to 11.5 afr. Since i have a wireless wide band with data logging i can make some adjustment without haveing to throw it on the dyno. But Sometimes i even hit 10:1 witch is very rich but i havent had the beast out in very hot weather yet so thats my saftey net. If in 95 deg weather the afrs are still good i will lean it out a bit and go from there.

my advice is better rich than lean.

vd..

 

[GR8_ASP]

I kind of expected the f/a to become richer in warmer weather (fuel staying about the same while the air density decreases).

I also would like a more constant 11.5 to 12.0. Has anyone found a new injector with enough capacity to work with stock pressure? That would be the cats meow as then the base cal could be remapped and avoid the split second unit entirely.

 

[VIPER D]

ron the split sec does not do fuel it only turns on the pumps thats it. It does timing only as it comes from paxton. You need more fuel or more back pressure. More back pressure is less hp.


I think that you should 1000% spend the $$$$ on a vec 2 Its a great tuning tool plus it will save you thousands on motor rebuild. The reason I said hot weather is more chance of detonation due to hotter inlet temps kinda like running a paxton with no charge cooler.

vd..

 

[GR8_ASP]

I agree VD. I guess I would be happy to get rid of the high pressure fuel system (and my concerns over a fuel leak). With higher flow injectors the ECU could be reprogrammed for the injectors and for spark retard with boost.

Now do you use both the VEC2 and the split second? If so are you able to get back the lost 1.5 degree of spark advance the spit second adds across the board? That would bring back some part throttle fuel economy and performance (non-boost periods).

 

[Viper X]

DSR207, I added the stage three heads and have the B & B headers, mufflers and 3-inch exhaust. The tuning / boost is set at minimum, so no worries at this time about hp / tq. I plan to stay at minimum boost until the rebuild (which is inevitable in a supercharged engine with stock internals). Some of the tuners put the boost up on a stock motor (stock heads and exhaust in particular) without the ability to "breathe" quite as well and can get higher numbers, for a while. Roller rockers go in next week (as a safeguard) and the 3.07s are back for traction purposes.

ViperD / Carrot, The air / fuel ratio (very small graph type lines on my print out + old eyes) are actually closer to 12.5 to be more precise. It's always interesting how you guys in the cold climates have to deal with weather more so than we do. I think we take that for granted. My tuning was done at 85 degrees, so not much to worry about it terms of higher temps leaning anything out where I live. Besides that, using the stock computer to tune with, it will change the air / fuel ratio based upon sensor input, one of those being heat, as I understand it.

Time to feed the Viper, gotta go.

Dan

 

[DSR207]

"Now do you use both the VEC2 and the split second"

I'm using VEC2 only...

 

[Qualitywires.com]

Viper SRT, I don't know too much about the Vec 2 but do know a lot about the split 2nd computer, but if you have not used the r4 software to access your split second box then I would get someone to help you out on it. If you can send me a base map of what you have I can send back a richer map based off your dyno.

The Gen III viper fuel system you should still have a little bit more fuel left to go...What I would also think about doing is adding on a water **** system to what you have...lots of good benefits of having that. DLM can help you out there in that.

The FMU that comes with the Paxton kit should have 2 disc...one will give you a higher pressure disc which will increase the fuel...also...your fuel pressure looks to be correct.

 

[VIPER D]

I agree VD. I guess I would be happy to get rid of the high pressure fuel system (and my concerns over a fuel leak). With higher flow injectors the ECU could be reprogrammed for the injectors and for spark retard with boost.

Now do you use both the VEC2 and the split second? If so are you able to get back the lost 1.5 degree of spark advance the spit second adds across the board? That would bring back some part throttle fuel economy and performance (non-boost periods).

I do use both, but the split sec is only used as a trigger to turn on the pumps. I have modded the vec2 to use it as a shift light. Thats why i have to use both.


vd..

the way your srt sits you don't need bigger injectors you just need to be able to open them up on top rpms

 

[DSR207]

Some info about VEC2
VEC2( ROE)

 

[VPRTKMIKE]

If you need help, you can give me a call at work 516-249-1040. I have done many of these on 03- up.


mike

 

[GR8_ASP]

AB - sent you a PM about the split second

 

[Qualitywires.com]

I sent my phone..number...give me a call.

 

[GR8_ASP]

AB - Will do. I have to locate a serial cable ist. Loaded R4 software on my laptop last night so I should be ready. When is a good time. It is snowing here so I have time on my hands. Damn!