i know you said it was the same dyno but did the operator mention any calibrations he may have executed in the past year? i am not trying to tell you anything you dont already know but differences in tire size, psi, oil types, oil weights, etc can all affect the end results. i would not contribute one factor for that much loss but it certainly could be a combination if no calibrations had been performed. also, are these number std or sae corrected?

 

A year is a long time... the owner probably recalibrated his dyno and set it up to compensate for more this time.

 

I seriously doubt the dyno had been recalibrated - SERIOUSLY doubt it. Now, the tire pressure thing is something to consider. Hmmm....I'll have to bring this up with Trey.

 

way too many variables to be worried about 13 hp form a yr ago... My car dyno'd at CAT recently with Osiris and it was only a few hp higher than the last time I dyno'd there a yrs or 2 ago (same machine, similar conditions)... however, the car is WAYYYYY faster now - without a doubt.

So (Trey) unless you can "feel" the car is not up to snuff or it isn’t performing as normal at the track - I wouldn’t hold too much credence in the dyno (as far as validating any loss of power).

 

Went back to the dyno today. I'm not going to post numbers yet, because I've got quite a bit of analysis to do. I did check with Blake, and the dyno has not been calibrated since my last visit.

This dyno is as repeatable as I've seen a dynojet. For example, in one of my other dyno posts, I overlayed a dyno from ~March of 07 versus a pull in June of 07. The correction factor for the pull in March was 1.00, and the correction factor for the pull in June was 1.06(basically inflating the number bu 6%). The numbers were almost identical, and the curves were identical.

Additionally, also in March of 07, I dyno'd on a dynojet in Tuscaloosa Alabama, and on the same day, on a dynojet in Trussville Alabama. The peak numbers were off a bit, but the curves were identical.

Anyway - the fact is that my dyno this past Saturday was lacking quite a bit of power. The only difference between this past Saturday and my previous best numbers was the stock airbox versus the Stillen airbox, and my tires. I ran shorter-than-stock tires for right at two years: 26.0 inches. Now I'm running taller-than-stock tires: 26.7 inches. Also, I noticed this week that my tires were low; when I checked them, all four were ~25psi(no pressure sensors on my wheels). They are now inflated to ~40psi.

I checked the a/f's, and they were way off versus when the car was tuned. So the power differences can be attributed to the wacked-out ecu after the battery swap, running tires 2.5% taller, and with very little pressure.

I'll try to post more this weekend. But I'm doing another suspension swap tomorrow, so it may have to be early next week.

 

Fuel changes, air density changes [barometric pressure], carbon on valves and pistons, tire psi and tread depth, or just aging hardening compound.

 

i suggest a compression test to ensure the motor's health

 

Motor's got just under 30k on the clock. And I posted in the other thread that I've pretty much got the power back. Thanks though.

 

What facility did you dyno at?

James is an excellent guy and we're real lucky to have such a great tuner on our team. I'm James can help you figure out what was going on. I'd look at the tire pressure and size difference changing your overall numbers. One of the good ways to fake a dyno gain is to go from under pressure to over pressure on the tires, rolling resistance can show a 10-15whp change. Far too many companies will do that when proving their dyno numbers on their product.

You're right in comparing curves instead of peak numbers, dynos don't work on peak numbers, they are just there for reference on the chart they create. Even a recently calibrated dyno can be off by as much as 8% on back to back runs, it's the nature of the beast.

I can't tell you to ditch the Utec and move to Osiris (well yeah I can but...) you might want to look into some of the reasons people will use both up until this point. Now that we're more adjustable and have greater control over the ECU, we have alot of long time Utec customers making the move to just Osiris. You might want to talk to James about your options, and first thing is to find your lost power.

 

Also, it doesn't take Osiris 1000 miles to complete it's adjustments. We usually recommend a few miles, or a days worth of normal driving before doing any data logging for our eTunes. We lock the ECU down pretty tight compared to stock. Unless obviously you're using Map Switching and then switching to a Stock tune... That will take a bit longer to correct itself, but still far less than the actual Stock tune because we have some base adjustments that don't change between Maps.

 

Thanks for the feedback man. I've got it all worked out. I created a second thread that contains all kinds of charts and analysis.

I've considered ditching the utec for the osiris. But it would be a loss, and there's not any more power on the table. But it's not really that big of a deal at this point. I've got a track day in October. I figure I'll take out the utec and sell it after that, and probably run the stock ecu until I sell the car.