[BT M3]

Originally Posted by PencilGeek

Last week, we had a Dynapack dyno day. One car put down 390whp on just an Akra, ECU tune, air filter, and 91 octane. No 93 octane, no underdrive pulley, and no air scoops. Just an exaust, filter, a good tune, and crappy 91 octane.

At least I'm not the only crazy one - but remember i have no real X pipe

The problem with measuring air scoops, is that the dyno fans don't adjust CFM to simulate road speed. This was all discussed in the thread JO8M3 referenced (I know...because I discussed it). The dyno fans don't increase air velocity with hub RPM. Only one or two dyno's even have this ability -- and one of them that has this capability (Rototest) is finally getting installed at a US tuning shop sometime next year. Also in that thread, it was suggested to run some vBox times with and without the scoops. I'm pretty sure somebody said they'd do it...but I don't recall ever seeing the results.

I totally agree here there is ambiguity - I'm just posting what I saw.

I love the Dynapack for its hydraulic load -- just like a real motor dyno. IMO, it's the most accurate method to measure the engine itself without taking it out of the car.

I agree

But the Dynapack "SAE Adapted" correction is a bastard child. Dynapack "SAE Adapted" uses non-standard temperature, barometric pressure, and humidity references. It's a true bastard child because pre-SAE-J1349 used one set of reference values, SAE-J1349 used a new set, and Dynapack uses a mixture that conforms to neither. That's why it's a true bastard child for SAE correction. If you use "SAE J1349 (2004)" correction on your dynapack, then you will be using the correct method for correction -- the same one Dynojet (and I think just about everybody else) uses. Changing to J1349 correction, 407.7 should end up around 391whp. Still a great number.

Let me verify this when I am back on the dyno Saturday. IIRC there is only one SAE (Adapted) setting on the 4000.

Another thing affecting the results on the Dynapack is the gear ratio. If you let the dyno estimate the gear ratio, then the results won't be correct. Jon Martin's was like this. And by the time I figured out how to correct for it, his results were adjusted even higher by the results. The only way to know for sure is to post all of the files. Anybody with a decent amount of knowledge will be able to look and see if something is wrong. You've got all of the Dyno Files. Archive them, and post them for everybody to download.

I won't ever use a gear estimator, not my procedure. It's never accurate and when the car is redlining and the tach is 1000 rpm away from the limiter on the dyno that's more of an annoyance and waste of dyno time then anything. We manually input every number. For my car we've used the same standard and gear setting saved file for each run every done. No variance there.

For customers with unknown gear and rear end swaps (E30 M3 with mystery trans and euro S50) is the only time I've ever use it is to check a wild manual input that doesn't sound right and see if it matches on the tach.