Different wheels and tires shouldn't make that much difference. I think the most likely issue is the tuner doing a crappy job, and the second most likely issue is that it was done on a different day and probably different dyno.

Make sure your tires are properly inflated, and your air filter is clean before getting it tuned / dyno'ed again.

 

They can and do make that much of a difference. The only way they made no difference is if the OP was dyno'd on a dynapak.

 

I'm not saying that bigger / heavier wheels make no difference. I'm saying that they don't make THAT big of a difference unless they were MUCH heavier and you were using a low gear (short load times). When I dyno'ed my AP1 with OEM 16's then again with super heavy 17's, there was only about 4 RWHP difference. We also never noticed any significant difference from big wheeled S2000's when we had local S2000 club dyno days. Even on my software dyno (which I believe is more consistent than conventional dynos), the only difference I see on my AP2 with my OEM 17's compared to my super heavy Work 18's is the difference in gearing from the change in outer tire diameter.

 

OP is leaving something out. Even if the rims and tires only lost a few whp and not 12 like he lost. That's still only 6-7 whp missing from his tune on top end power. Is the tuner really so bad he lost you 7 horsepower?

 

I totally geeked out tuning my VAFC on my AP1, and I've totally geeked out again tuning my FlashPro on my AP2. I can easily see why there should be a gain going from a VAFC to an EMS, so the fact that he lost power means that the tuner either really sucked, or this is a significantly different dyno, or there is something mechanically wrong with the car.

 

To bad he didnt dyno with the VAFC again after the wheel change to see the real difference. I agree it might make around a 5whp difference with bigger wheels/tires, but you shouldnt lose that much with a full EMS over a VAFC and smaller wheels. He should be putting down at LEAST what he put down with the VAFC with smaller wheels with his current set up, and honestly should be making more since there is alot more settings to tune with.

Like I said, try to find a different tuner.

 

the op is on 17's which come stock on the ap2.. so whats all this i hear about losing power, its like saying an ap1 will be slower if its on stock ap2 wheels. im sure his rolling diameter is close to stock ap1 specs, so not even the gearing should change much. there are to many factors to take into consideration such as the op being located in fl and for all we know he could have tuned the afc in the colder months down here and now the aem being tuned in the hot summer months. could have been a different dyno or maybe just some uncorrected numbers from his first tune.

 

the ap2 is geared completely differently. So yes, an ap1 is slower with ap2 wheels on it... sorry.

As long as you get 245/40/17's you'd be about the same diameter though.

 

The OEM tires for the AP2 wheels are actually about 1/4" smaller in diameter than the OEM tires for the AP1, so I would wager that an AP1 with AP2 wheels might still have an advantage in a drag race.

 

yeah to the tune of .3%

Or 3 tenths of 1 percent faster...