Tune?

[911teo]

So

after swearing to myself I would never touch the GT I am sitting here contemplating a pulley swap, new exhaust system and a tune.

But I would really like to understand what the tune does.

I am planning to drive this car hard on long distances (read through Europe - Germany) and the 1k mile weekend is not going to be that rare.

So my concer is maximum reliability.

The pulley swap is easy to understand.... more power as there is more torque avaliable at all rpms...

But after that what does a tune do? Lean out the mix, advance the ignition, higher rpms? I mean how do they get 50hp over the base? What if you get substandard fuel? I will not be able to always get the best gas out there?

I am a bit skeptical, well not skeptical, cautious... Can you explain in plain terms what the tune does and why it is safe?

Thanks

 

[kumar]

You probably need the tune if you are going to do the pulley. A safe tune, like one you would get from one of the sponsors, shouldnt hurt reliability one iota.

A tune can do several things: adjust air fuel ratio, timing, change rev limiter being the basic things. As long as the tuner doesnt push the envelope in any of these areas, you wont sacrifice reliability.

 

[B O N Y]

Buy a Heffner pulley and their tune.... 110% reliable, only difference will be performance, better cooling, same idle as stock. email me at bonyhadi@gmail.com and I will send you my dyno pull with this system and the accufab x pipe. Today I would buy the Heffner exhaust because of the sexy tips.:thumbsup

 

[nota4re]

Matteo,

I am happy to write as much as you would like to satisfy your curiosity - as I really like the topic of engine managagement.... and I could go on for a long while.

Here's a gross simplification. A smaller pulley will force the SC to spin faster and create more boost. A tune is needed to insure that more fuel is injected into the engine to preserve desired air/fuel ratios. When you're not on the "go pedal" hard, the car is running in closed-loop mode. It is looking at the O2 sensors and using them to achieve a perfect 14.7:1 a/f ratio. Regardless of a tuner's intent, closed-loop mode is never changed. If a car cannot achieve 14.7:1 as reported by the O2's, the ECU will throw a check engine light. However, when you are on the throttle harder, the ECU wants to run the car a little bit richer - especially under boost conditions. Regardless of popular belief, narrow-band O2's can only report a/f's above or below 14.7:1. They are essentially binary devices and therefore cannot be relied upon to report on a richer target mixture, say 12.5:1. So, OEM's switch to a mode called "open-loop". In this mode, the ECU is looking at critical sensors (boost, air inlet temp, mass air, etc) and determines through INTERNAL tables, how much fuel to inject. Over-simplified, an aftermarket tune changes these tables.

I for one, have complete trust and confidence in the tune developed by Heffner. I have installed in in multiple cars and I have NEVER experienced a single adverse effect.

 

[Chris A.]

Don't forget about Jack at MMP's kit....it’s very comprehensive. Gave me a great boost in HP and torque without affecting reliability.