Ok, so I dyno'd at ~500' above sea level at MachV Motorsports (Dynojet) in Sterling, VA, a few months ago. Then, I moved to Colorado and wanted to see the loss of power due to altitude, so I scheduled to hit the only Dynojet in CO today before my cam install. Here are 3 comparison graphs: overlay showing conditions, overlay showing uncorrected comparison, and overlay showing how stupid SAE correction can be. These dyno pulls were done with 0 change in tuning, boost, or octane between dyno trips.

Conditions - notice it was warmer in CO than in VA just on this particular day


Uncorrected direct comparison, although the CO graph is ~15 degrees warmer


Awesome SAE comparison showing how my Evo supposedly gained 36whp/53wtq just by climbing up nearly 5000'!!!


3 things of note on the graph comparisons:

1) Spool is about 300rpm later (ouch)
2) Peak power differential is 13% on WHP and 10% on WTQ
3) Peak differences don't tell the story, because look how my 5300' peak WHP is up near 5200rpm, and then the 2 curves diverge as I approach 7000rpm, so the most power is lost in the drag racing range (5500-7000rpm)

I did notice my boost was lower, as it should have been due to the lesser atmospheric pressure, but when I turned up my boost 2 lbs, I got an extra 20wtq, but I gained 0 whp after about the first 500rpm, so I'm at the turbo's efficiency range for this altitude...or at least for my current setup.

 

Did your AFRs change? Do you have those to post up?

 

Clay I apologize about leaving you yesterday when that light turned yellow. I didn't want to lose those guys and my car LOL! I hope everything went well last night for you and it was great meeting you.

 

His A/F's were still very solid, I don't know if he was happy with them though. Were a little lean, but I think that was addressed last night with Al and tuning for altitude and his new cams.

 

Unfortunately, no. The AFRs from the first dyno were being read by Al's tuning equipment, not the dyno sniffer. The AFRs from the second dyno were ready by the dyno with one of those probes that sends the exhaust through a box with a Bosch plug or something. They were 11.8-11.9 most of the way and very steady up here, but back at MachV, they were 11.3 or so. I don't know what would cause the difference other than the sniffer type maybe?

 

Great post Mr. Warr! Could you post up a graph in STD correction just to see if it does any better correcting for a turbo motor. That SAE correction goes a very very long way to proving how a few tuners have lied with high altitude corrected dyno graphs.

 

STD gives me the highest numbers near sea level, but only slightly lower-than-SAE numbers at altitude (3whp/3wtq):

 

Good info Warr!!, what I noticd when I was there is that the car feels a bit sluggish.


I can't wait until you put the cams on your car, I think what you are doing no one has attempted. We will get to benefit of the Cams choice base on your testing and the great speonsors and tuners that are behind the scene.


Carlos

 

Thanks Clay.

Well, it looks like STD is significantly more accurate than SAE, but still very exagerrated. I wish we could look at the exact same test on a 400 horsepower NA car just to see if Dynojet corrections are ever accurate when calculating different altitudes. I guess altitude is one parameter that is not corrected for. Temp - yes. Humidity - yes. Thin air - no.

 

I don't know if I'd consider STD significantly more accurate. STD gave me HIGHER than uncorrected numbers down near sea level and then was within 1% of SAE at altitude. This is why I decided a while ago only to use uncorrected. I will record and report SAE for others to see, but I personally only care what I'm actually putting to the ground, because no correction factor is going to change my trap speeds.

 

Warr,
STD is significantly more accurate. STD only reads 24whp higher, whereas SAE is 36 higher. In torque, STD is 40tq off while SAE is 53 different than uncorrected.

BTW, I'm going to hold you, Al, and DB to this uncorrected dyno preference this summer when it gets hot. That preference is definitely a two edged sword... I'm willing to bet that yer boy Al will not be using uncorrected #s in 100 degree + weather when it makes his tunes look less powerful to the general public.

 

Very Interesting.

 

very good point....and I'd bet you are 100% correct

 

Smoggy, you can't look at STD that way. It's only closer, because it INFLATES the sea level numbers to even higher than uncorrected. That makes no sense when I was in cool weather. The variance between the two when using STD isn't as much, but the numbers taken in isolation are both wrong in their own ways. I suppose it just comes down to perspective, but I still don't see either correction as being viable.

As for the summer, I don't care what anyone else does. I only care about uncorrected always. Even here, this dyno was in 80 degrees in freakin early March in Colorado. It should have been like 30-40 degrees, but I'm not going to try to speculate what the numbers would have been in the normal temps we have up here this time of year. I have what I have, and that's all that matters at the track, you know?

 

I know, I know Warr. Just havin' some fun. The most important part of this post is that Dynojets correction factor at altitude for Evos is WAAAY off. That doesn't mean at all that the correction factor isn't valid at a shop that is at 800 feet above sea level. I can show you charts corrected and uncorrected from Tuning Technologies that make perfect intuitive sense.

I'm poking fun at Al because just a few months ago he was posting up corrected dyno charts from Pruven when it suited him and then, when the weather got cold, he all of the sudden doesn't believe in using correction factors....