Alright, Im really starting to get worried and confused here.

I initially dyno'd my car on Saturday (01/20) and put down a best of 206 / 151.
I went back on Monday (01/22) and without touching ANYTHING at all...the baseline looked like this:



After tuning the car, I got a best of 208 / 153.

I went back today to do some fuel tuning..and without touching anything again...



What the hell is going on?! The car is just loosing power it seems. By tuning the fuel a little today, I was ablet to fix most of it and match it with the results of Monday, but still didnt make the same peak.

Anyone ever see this happened before? Is the motor going down the drain? Could something be wrong with the dyno?

 

what were the weather conditions for each run? is there a correction factor number that has changed? what color socks were you wearing for each?

ok, one of those doesnt matter, but those can affect the results (though i'm pretty sure you know that)

Brian

 

Temp was within 2 degrees of each other, CF was also the same on all runs.

 

man, you are a dynoing fool!!
Wish i had as much time to hit the dyno as you do
but thats just what happens when you dyno on different days.

 

You won't get the same #s everytime.

 

Its just disspointing to see...

On my non-VTEC setup..its was WAY more consistent. I could dyno one day...go back 3 weeks later and it would trace the same...maybe +/-1 HP.

Heh...yea, Ive done about 60 runs since Saturday morning

 

I find that repeatability is within 10hp. remember, thats only a few lbft
as long as the curve is about the same then its the same to me.

 

Easy there, Big Fella!

There are some things you haven't told us and there are a lot of variables involved in dyno testing. First things first......... Is the dyno operator knowledgeable and capable of operating the dyno in a consistant manner?

Is the car tied down the same? Do you have more things or people in the car at one time or the other? Are the tires about the same temperature each time? Is the hood open or closed each time and is the cooling fan in the same place each time?

Was your car thoroughly warmed up each and everytime or was it cool one time and hot the next?

There are four external variables that affect power output; barometric pressure, temperature, humidity, and actual oxygen content in the air. Racers, of all kinds wil monitor some or all of these factors depending upon how serious ($$$$) they are and their level of competition. There are SAE corrections for at least the first three and unless they are accordingly factored in by the dyno operator and his computer your results will vary.

John

 

Let me ask this...

How would octane affect the power? Specifically 91 vs 99 octane

 

it depends. if you are experiencing detonation on 91 then 99 will make more
power. If you arent, and you dont advance the timing with 99 then it
might not make any difference.

 

Could it cause the car to lose power?

 

yes, 99 can make less power if you dont adjust anything.
thats why you shold only use the lowest octane that causes no detonation

 

Alright, that is what I was thinking.

The car doesnt detonate on 91 octane, but at the end of the dyno session on Monday, we threw in some 116 octane to see what it would do. We did 2 runs and it did nothing at all..but I dont think it even mixed in with the other gas sincet he car didnt move off the rollers.

Wehn I went it today..I still had the gas in the tank..and its fully mixed by now.
That migh tbe the variable.

 

you should just buy a dyno, seems like you spend enough time on one, lol

 

Haha...I would if I could afford one

I get hooked up nicely though...Ive done over 100 passes at this dyno places so they hook me up. Hell today I didnt even pay anything for the 8 runs I did

 

60 runs!!
do a tuneup
every 10-15 times you run your motor hard...change the pluggs...u should do it anyway when dynoing along with oiling changes in the tranny and motor...believe it or not it works...

 

Why are you whining? There is only ~2-3% difference between runs. You need to take a course in statistics my friend either that or some Ex-Lax.

 

116 octane is way too high for your motor. and i bet that 116 is most likely leaded. bad bad idea. i wouldn't be surprised if you screwed over the o2 sensor on your car & the wideband on the dyno.

 

Octane is only one factor in how gasoline functions. Some gasolines also like different RPM ranges. At Daytona a few years ago, we found a blend of Amoco Gold and Union 76 got us around the track faster than either Amoco Gold or Union 76.

This year after dyno testing fuels we went back with a different Racing Gasoline that we ran at 100% and went faster than ever.

Gasoline can be strange stuff.

John