jr50rider

Two more questions for you guys.

1.) I have an appointment to get my car dyno tuned next tuesday. is there anything i should do to it prior to bringing it?

2.) My car has 4:10 gearing and the speedometer is off 15-20 miles an hour. i do not know if it has the trans gear replaced to correct this. although i was told that even with the gear the speedo will still be off. Anyone have this issue?

Z28KLR

1) Ask that question to your tuner. I read a post here a while back about somebody who once grenaded their engine during a dyno session and blamed it on dirty oil and swore that it would never have happened had they gone in there with fresh oil. Don't know if that really has any truth to it though.
2) The speedo gear should correct that. If your speedo is off by that much, my guess is that the speedo gear was not replaced and is still calibrated for 3.27's or whatever '98's had.

jr50rider

thanks for the reply. i need to check the gear and i will call the shop to find out.

dastangman

I don't see the oil necessarily being the issue with the engine grenading. If oil was changed at the necessary intervals and was at the necessary level, something else is wrong. The car isn't going to see loads on the dyno that are any higher than what can be achieved on the street, only difference being that the dyno is trying to match those loads. Furthermore, the dyno operator is able to see many variables and should have a pretty good idea of what is going on with the car as he's tuning.

If he's tuning correctly, he's not just going to jump in the car and floor it and see what happens. He'll instead begin by working up slowly, making sure A/F and other variables are okay at each RPM level and various throttle positions. In my opinion, if the car was tuned correctly, the problem with the dirty oil or something not being right (which would later blow the engine) should have been caught earlier.

I would though, just make sure your fluid levels are good, that you don't have any leaks going on, and then also make sure tire pressure is okay. Bring any information you can about the car that might affect what's done, such as modifications that he might not see or know about, and also have a good idea of what the weight of the vehicle is.

And lastly, perhaps most important of all, have a good idea of what you want from the car. Do you want a conservative tune, something for a specific octane of fuel, do you have a specific horsepower goal in mind that the dyno tuner can meet or either give you suggestions on reaching. If you haven't used the tuner before, I'd begin by keeping things simple for him, unless you've heard NOTHING but good things from him.

The reason I say this is because, not all tuners are great. Some take pride in tuning cars that make insane power very safely, but others seriously just want to make big numbers to make you happy while you're there, take your money, and then not accept responsibility two days later when you detonate a piston. Keep things simple the first time, see if you like how it drives, if it makes a tad more power, if things sound okay, and then see if there's room for improvement.

lizzyfan

You cannot correct exactly with a different speedo gear. Gonna need a Speedcal to correct it