Saturday, June 11, 2005

Dyno day

My car's been tuned, retuned, tweaked and retweaked that I thought it would be time to see if it's healthy. Not having a wideband, I decided to go to a dyno. My mechanic put in a nice Mustang Dyno earlier this year, so I decided to see how it's going to do.

The car's been in Speed Density more often than not, as it always allowed me to look at VE's without MAF screwing it up. Since I was going to the track the day after, I decided to reenable MAF, as the weather report for the weekend predicted everything from sunny 60F to thunderstorms and mid 80F.

So the night before going to the dyno I do a last run and check my LTFTs and everything is perfect. To save time (and money) at the dyno, I prepared a bunch of different setups, differing mostly on AFR, as timing was supposed to be changable using the live controls in HPTuners scanner.

I put in one of the MAF setups in, and drive over the next morning for some dyno time. It's hot, it's humid, and my LTFTs are going absolutely nuts, about 10-20 points on the lean side. At this point I say screw it, put Speed Density tune on, as it seemed to be less nuts, and go on the dyno. Of course, all the prepared setups I had were useless, as they were in MAF mode.

First run:
We run it to 5252rpm, just to see how badly off I am. Turns out that my SD tune I quickly put together didn't have High and Low Octane tables equated, so I got only about 18 degrees of timing, still resulting in right under 350rwhp and still climbing! Suprised but happy, I make spark adjustments, and run it to 6500rpm to see the true powerband, at a fairly low, safe 22degrees of timing. Power peaks at 353rwhp@6000rpm and it starts to drop off after that.
My AFR at that point to set up to do 13.0-12.6-12.2 as the rpm's rise. While I can see the general trend of AFR having 3 separate areas, every run has a different value for each section.
Question 1: timing adjustments--can they alter the resulting AFR?

So I start to screw around with different AFR/timing combinations, slowly working my way up to more stressful settings of 13.0AFR and 29degrees of timing. That run was my last one, resulting in 364rwhp, strangly enough resulting in AFR bouncing back and forth between 12.2 and 12.7, which is exactly what I wanted. Knock did not occur anywhere, so I figured the car is healthy.

For the day after, the trackday, I decided to start with my last tune, just go back to one of my other tunes with AFR at 12.6 timing at 25degrees, which netted 359rwhp. I'm not sure what the AFR really ended up being, as my PE mode didn't seem to have a clear correspondence to the real world results.

All and all, a good experience, albeit an expensive one. I did 13 pulls, but because of the last minute changes to Speed Density modes and not having any setups ready, I spent a lot of time poking around in bins changing AFR and timing, wasting time.

Few observations:
1. go to a dyno on a day with normal temperature/dyno, otherwise you have no idea what you're really measuring.
2. have your setups ready for loading. don't waste time and money on making changes on the fly, unless there's a real reason for it.
3. setup a log, or better yet a spreadsheet in which you note all your settings, results, observations. note time and order, otherwise you'll have a problem matching them with the dyno results.
4. dynos are not the most precise devices. don't use it as some sort of ultimate result. I have not seen as much airflow as on the street, the temperatures were off, the MAP pressure was off too. you can't really simulate the real thing, unless you get out there and do it.

I'll post some graphs later, right now my dyno guy has a problem with his software, all his datalogs got cut off at 5777rpm for some reason :(

1 Comments:

At 8:57 PM, July 09, 2005, Blogger 405HP_Z06 said...

It sounds like you had a good time at the dyno and learned a lot. Did you use any of the bi-directional controls for timing on the dyno?

 

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