Alright. This is the juicey fruit.. I bought my 8 last year in sep time frame. After buying I had to have its engine replaced.. ..... we all know this can be a headache.. any way.. After replacing the engine I had the dealer install my ap underdrive pulley and ap mid dual res mid pipe. i already had done the vfad removal and dropped a K&N in.. I picked up my COBB tuner and also had my pipes redone into a y split..

Here is the Question.......

Why does it seem faster some times and not others..?

I know cold air helps. But damn.. It gets torquey and pulls hard when I really give it gas. and then other times it feels no different then normal.. Not stock.. Just like I'm used to the power change..

I've looked up and added all the mods to the stock motor and came up with about 255hp or so.. but my cobb tells me 241.. no matter someone explain .....?

 

Ah. The classic case of "additive mod hp" ricer math. Nice. I had forgotten that people still do that. Do people still do that? I guess they do.

 

The dealer installed a midpipe? I find that hard to believe, considering how much legal trouble they could get into by doing that

Temperatures is the biggest reason. Cold air helps, cold fluid hurts, hot coils can hurt, etc... The engine is very sensitive to even faint changes, and everyone here gets that. There are times that it feels like you've gained 20-30hp, and others you are wondering if something is wrong. For example, Eric Meyer found that you can lose 5-10hp just from the transmission and diff fluid being cold instead of warm.

Chances are you took a wrong base number and added more numbers, that are probably wrong, and got a wrong number.

1-the engine, if running in absolutely perfect condition, CAN be 240hp, or 238, or 232, or 228. Depending on what official measurement you want to believe. That's a spread of 12hp.
2-drivetrain losses increase as RPM increase. You lose a higher % of power due to drivetrain at high RPM than you do at low. Since HP is basically TQ * RPM / 5252, HP peaks are usually higher RPM ranges, and our engine takes that to an extreme. So a perfectly running stock Renesis (with new transmission and diff fluids) will usually have ~180-185hp to the wheels
3-Your mods are probably overstating the gains. K&N filter has never been shown to add more than 1hp, and since it allows sand into the engine, the stock paper filter is still run by race teams. It might not add even that, depending on your engine. The pulleys might add another 1hp, but maybe not. I haven't ever seen proven gains from pulleys. The midpipe can add UP TO 10hp on the 8s, but really has to be tuned to get the biggest benefit. Catback exhausts are for sound only. HKS I think is the only one that has shown proven gains, and most of them are either the same as or worst power than stock cat back. The COBB CAN give you 10-15hp, depending on how back your ECU was in the first place. Some people can only get a couple HP out of it, others can get 15 or so. As an example, my friend got the COBB and MM tune, and it brought his 8 to the point that mine was, still stock.

N/A, the most you are going to be able to get out of your 8 on street mods and casual funding is probably 200whp. Dump more money in for porting and the like, and you can get to around 210whp. If you want to dump in $50k+, including a BOSCH complete ECU replacement for $30k, you can get 220+, the highest I have seen was "222whp+" from a funded race team.



Those other cars that you can drop these items in and pick up 20-30-40-50 hp, well, lets just say that these mods are removing some of the intentional retardation from the factory. Mazda didn't do that. They didn't leave much at all on the table. ECU re-tune and midpipe are the single biggest power gains, simply because the cat is required by law and reduces power, and the ECU is tuned somewhat conservatively as a slight nod towards the casual drivers. Everything else really is that good stock.