It depends on how you use it. I presume you will use it on your Viper (and not Subaru) and you will use a VEC to calibrate your fuel/ignition/water.
On Gen2 Vipers it's primary purpose is to act as a chimical intercooler. Your boost level will also increase by 10-20%. So you reduce intake temperature and you increase boost level.
For instance:
- Intake temperature drops from 160F to 110F. (I had 180F thermostate and Roe cooling duct). That's a fantastic result. This is very important for higher boost superchargers in order to reduce knocking.
- Boost goes up from 7psi to 9psi. There is also a sealing effect.
The quantity of W/M is tuned through the VEC. There is no need to change the injectors.
Use the charts in the Roe W/M kit to start. Usually there is not much to change in the W/M quantity.
Once you have the W/M chart it stays like that for a long periode. You rather play with ignition and fuel.
When you are bored with Fuel and ignition tuning you will return to W/M tuning.
I had a couple of custom W/M adjustments but rarely I tuned them.
Timing adjustement is the big challange. You will have to rely on your ears as the Viper does't have knock sensors. Roe gives you very good base timing charts. Usually you adjust 2-3 degrees around those values depending on: outside temperature, fuel quality (93 oct is not the same everywhere, I can certify this), driving style so on.
The
weakness in the GEN2 Vipers is the ageing PCM. Many cars with advanced PCMs can easily achive 8-12psi boost because of the built-in ignition tuning features.
If I was you I would set very
conservatively my ignition on a Viper so you are always on the safe side. Fortunately it is easy to hear detonations in the engin. In addition there is not much HP to gain from ignition tuning. It is better to loose 20HP from 650hp than break your engin. Whereas adjusting your AFR by just 0.5 you can gain 50hp !
HP is gained mainly by leaning out your AFR. When you add too much W/M you also loose considerable amount of power. W/M helps to lean out your AFR without causing detonation by reducing intake temperature.
Start your target AFR at 11.5. Then once you get familiar with tuning lean it out to 12.0. Add W/M in the rpm and boost ranges where you hear detonation then mesure your power gain. If you loose power try to retard ignition and reduce maybe W/M. The best is test everything yourself.
There are a couple of tuning exemple in the Roe W/M kit. Basically when you add W/M you can "advance" your ignition. That's the start. In my case I used w/m to increase boost level and reduce intake temperature. It allowed me to run leaner without knocking. The idea is to get more power without altering the ignition. It is a real science to tune the Vipers. There is no magical procedure. You have to learn it by tuning your own Viper. Sean Roe has so much experience that he is able to tune your car by phone or fax.
Fine tuning the Viper is a time consumming task since the PCM doesn't have automated
advanced features to adjust timing and AFR. The timing and AFR features are very basic in the PCM. Fortunately the VEC is a great tool. It is the best "video game" that you can have. It is likely the most expensive too. I have spent a lot of early mornings on the hwy speeding and tuning my Viper. I managed to pool 600rwp from the 6.5lb pulley on street fuel ! However that was a record for chatting.
