Alright, after the responses that I've received here, you've definitely convinced me that having a tune done is a good idea because it can reveal bottlenecks that you don't know exist and can net some respectable horsepower/torque gains. Then again, if the car is running perfectly, it's $500 spent to do nothing more than re-assure you that your car is running great.

This sounds like a winning formula to me.

 

Speed sensors are in the 4 wheel bearings, so no calibration is needed with a gear change. If you have an auto, however, you will need your shift points changed with a tune.

 

If you don't mind me asking...
What exactly is involved in a tune?

 

C'mon, EG. With all the work you have done on Grond, you should know this. The speed sensors in the hubs are for ABS/TC/AH. The speed sensor (VSS) for the speedo is mounted on the differential and reads off the output side, hence no speedo adjustments on C5s. See Mike Mercury's page for more info.

 

Thanks to this thread, a nice TUNE is my next mod for my 97 A4. I have intake and exhaust, but also thanks to my extended powertrain warranty, Im scared to do much else.

A lovely tune would do me good...

Thanks!!!~~~JadeDragon

 

I highly agree with Patman. Before baseline, I only had a Halltech Stinger installed...then decided to do a baseline prior to installing GHL exhaust and found out the car was knocking pretty bad. I had the GHL installed and Charlie (Master Tuner) from A&A tuned the car and . The car was totally different. See sig.
Here is the dyno sheet.

 

They will strap the car onto the dyno and hook up an air/fuel ratio meter, along with some sort of scanning tool in order to check the knock retard. After the first dyno run they will check the air/fuel ratio and the knock retard, and then use LS1 edit (or other tuning software) in order to adjust both the timing curve and the fuel mapping. They can pinpoint exact areas where they want to adjust both of them, for instance they can leave the timing curve alone in the lower rpms and then adjust it up or down in the upper rpms.

Every tuner has his own idea of what is an ideal air/fuel ratio, but I believe most of them shoot for around 13.0 to 1 at WOT on a normally aspirated car. (they'll want it richer for forced induction or nitrous) The amount of timing they put in the car will depend on the octane of the fuel you're using, and the level of mods you're running. Most tuners will end up finding that the car has a bit of knock retard with the stock timing curve, so they'll end up taking out a little bit of timing until they see the scan tool show no knock retard on it.

In most cases it will take about 5 dyno pulls to get the proper tune. A good tuner will also know how to set up the part throttle parameters so that the engine feels much more responsive in normal driving too. A good tuner will also know how to tune not only for the best peak hp, but for most average horsepower overall, in other words he'll want to see a good powerband overall, with a nice flat torque curve. Peak horsepower is not the only way to gain performance, you can gain a lot by concentrating on tuning the engine in the midrange too.

With an automatic car, they can also adjust your shift points, and speed up the time it makes the shift too. They can eliminate the torque management (which retards the timing on the shifts to soften the strain on the trans, but also slows down the car) They can also play with the torque converter lock up points too. And one thing I found out on my last tuning session is that they can adjust the refresh rate for the knock sensors, so that if the engine senses knock but then the knock goes away, the computer will put the timing back in faster. There are also other things they can adjust in the tuning session too such as the rev limit (if you're running better heads and cam you'll want the engine to be able to rev past the stock limit)

With the right person doing the tuning, it is a wonderful thing!

 

Thanks Patman...just the answer I was looking for!
Ken