Thread:

Dyno question

Originally Posted by jimclauss

that little quake was pretty cool though. never saw one of those before. they really are something.

glad to hear your high enough to stay dry. the elevation i found to run those numbers was 49', so at 62', it'd be a hair less...

little tremors like you had aren't too bad. real quakes are a pain in the ass.

Originally Posted by bp298

temperature and altitude are two attributes that impact relative hp. but by themselves, it may be a little more, may be a little less than a generic "standard" of 3%. running a 60* increase by itself, you might only see 5% change in relative hp. an elevation change of 1000' might result in a bit more change, but that would depend on changes to other factors. "density altitude" is the usual method for describing conditions. it's calculated through a combination of elevation, ambient air temp, altimeter (pressure), and dew point. depending on the combination, i can show you conditions at relatively the same elevation where air temp is 75 vs 90, and the relative hp at 75* is way less than at 90*. from these 4 factors, you can determine relative humidity, absolute air pressure, relative density, etc. all of these factors are going to affect relative hp either up or down.
bracket racing, you need to have a pretty good idea how these factors affect your own relative hp, and compensate accordingly to hit the number. d/a changes affect different engines differently. there are myriad different ways people will compensate for changes.

Thanks! I'll have to read and re-read that a few times.

Originally Posted by Budweiser

Every time I drove to the mountains from So-Cal, I'd leave 75 degree weather at sea level and end up with noticeably less power in 35-40 degree air at 5500' ASL. Figuring 16.5% loss from altitude and 12% gain from temp decrease netting a total loss of 4.5%... basically the same loss from a 90 degree day at sea level, which I never noticed.

going from sea level to 5500', even with the way cooler temps and conditions, your most likely going to lose over 15% relative hp. very noticeable. going from 75 to 90 at sea level, you'd lose roughly 2%. and you're right, you wouldn't notice that small a change.

Originally Posted by bp298

glad to hear your high enough to stay dry. the elevation i found to run those numbers was 49', so at 62', it'd be a hair less...

little tremors like you had aren't too bad. real quakes are a pain in the ass.

first engine is back on the dyno will make some pulls tommorrow will be in touch with results/// results are in 722 hp at 6100 within 4 hp of the sister engine.. somehow it lost 78 hp over the winter must not have eat the right stuff. Not a happy dyno. engine should make 750-775 no proplem. I;m going to put one of my race motor back on there and see if that changed also.I'm going to race it next weekend at Mays Landing, NJ and then pull it out and put it back on the dyno,Or if I have time I'll do it before next weeks race. I like the coal mine air better on paper anyway.