# just wanted to do a couple dyno pulls (JR TUNE INSIDE) **URL:** \ **Category:** Shift518 Automotive\ **Created:** [August 31, 2010, 4:43pm UTC](https://forums.speedlife.net/t/just-wanted-to-do-a-couple-dyno-pulls-jr-tune-inside/254252 "2010-08-31T16:43:42Z")\ **Posts on this page:** 1\ **Showing post:** 20
**Author:** ![bennyfizzle](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/bennyfizzle/32/6291_2.png) [@bennyfizzle](https://forums.speedlife.net/u/bennyfizzle)\ **Post date:** [August 31, 2010, 9:13pm UTC](https://forums.speedlife.net/t/just-wanted-to-do-a-couple-dyno-pulls-jr-tune-inside/254252/20 "2010-08-31T21:13:49Z")
> [@Ice hockey players; I need 4 of you!](https://forums.speedlife.net/t/ice-hockey-players-i-need-4-of-you/34733/4): > > The MAF doesn’t know how dense the air is. The cyl airmass is estimated by the ecu using math calculations. So if it sees the same amount of air being sucked in and uses the parameters that you told it to in the summer time, it then sprays the same amount of fuel and the car will obviously be lean. This is why MAF-only tunes can be dangerous, especially if you run the same one year round. > > Of course, whether or not a narrowband o2 will pick up on that is anybody’s guess, however I can guarantee you that they will not under heavy loads and WOT because the computer uses a preset afr at those times and ignores the input from the o2. > > Maybe Pete’s car/ecu operates a bit differently. Does the evo have a wideband from the factory? Granted I don’t know much on the matter, but I’m referring to a MAF that bases it’s voltage on how much a heated wire/film cools as intake air passes over it. That means it knows exactly what the air density is, because air density is a function of temperature and humidity, no? --- _[View the full topic](https://forums.speedlife.net/t/just-wanted-to-do-a-couple-dyno-pulls-jr-tune-inside/254252)._