These dynos are good for ballpark figures and talking points/bragging rights. Dynos need to be calibrated and no dyno has the same atmospheric conditions everyday. Also there are several different correction factors that will change the outcomeI’m confused on why there is such a big difference in each dyno runs
I would assume Hennessey would be using correction factor. They are kind of tuning/dyno experts. But who knows.If that is SAE correction factor than 428 from the auto is good. If that is standard then not so much. Wish they showed what correction factor they used.
Speaking of porting, I also heard that the 22+ gen 3s (the ones that had the black IM and not the grey IM the 18-21 had) had a lot more, and consistent, casting imperfections which hindered power. Early gen 3s also had a viscous damper that was changed back to a harmonic balancer around 21/22 (possibly due to covid and supply issues). The gen 3 really got dialed back over the years in so many ways. Hopefully the gen 4 has the opposite experience.A couple things to note
1) much like ported manifold the gains from carbon trap removal seem to be all over the place, but one consistent thing I’ve seen is big gains down low and it’s free so why not. Also porting plastic intake manifolds is kind of an art because while you can get a few hp smoothing everything out, most of the major gains you see “ especially from the Boss and CJ intakes” is because the porter take the intake apart, epoxies the inside and smooths everything over. It’s expensive and very time consuming but on cobra jet when done correctly it’s 20whp all day long. This is the main reason why you see conflicting results when guys port a stock manifold it comes down to the engine lottery. You could get a really crappy manifold with a lot of flash and bang 10-15hp because it wasn’t made very well. Or get an manifold that was made on a good day and gain absolutely nothing, I’ve seen it both ways
2) the gen 4 coyotes both GT and dark horse are rated right on the money. The reason why you have a lot of people talking crap is because with the new tier 3 emissions, and how ford hit there Hp targets are by changing the powerband in much more progressive top end kinda of engine. Not a bad thing but it doesn’t exactly translate well into dyno graphs, it also didn’t help that the 18-21 gen 3 coyotes where kinda underrated, I’m not saying they’re making 500hp but really 470hp was a more appropriate rating for them. This is why the American muscle dyno comparison showed a 10whp gain over gen 3, where this gets interesting is the 22-23 gen 3s are nerfed significantly because of the carbon traps, the 450hp rating was much more realistic and why guys showed a 20whp drop over the previous gen 3s. Late model did a 22 vs 24 and it was a massive difference in favor of the 24 “gen 4” car
keep your expectations in spec and you’ll be happy