I have a feeling this might open a can of worms, but I wanted to pose the issue of comparing dynos from different locations against one another. I've always been one to say that disparate dynos really can't be compared. While I still generally believe that, Russ & I happened across something interesting. I have a graph of my latest 5th gear pull plotted against his latest 5th gear pull. We were both quite surpirsed by the results. The graph is attached to the post.

What I find interesting is just how close the two graphs are. There's a slight gap before 3k rpms, but that's a result of the operator loading the dyno before the recording actually begins. After 3k rpms, the two plots are nearly identical.

He and I both have 05 6MT sedans, with the mrev and stillen gen1 exhaust. We both also have the ztube, but I have the k&n filter as opposed to his stillen intake. But keep in mind that my dyno was done in Birmingham Alabama, and his was in (I'm assuming) San Antonio, Texas. two different dynos. Different days. Different conditions. Different operators. However, the dyno's might be the same model; that's unknown.

I'm not proposing that different dyno *manufacturers* can be compared. Yet, I'm still blown away by the closeness of the results.

 

Though there are a lot of items to factor in, most of the corrections now a days are done through the computer.

There are some things we could go over but with so many variables its pretty unbelievable that they were so similar.
My next proposal would be to have the same cars dyno on the opposite dyno...
Unfortunately you too far away to do such a thing. Now if there were two other cars closer to each other than it would be a little more feasable.

nonetheless- pretty nice graph.

 

Just to mention I am Russ for those who do not know.

Also, The Red line is my car and the Blue is Treys.

 

I'd like to say that I think this probably has more to do with the model of the dyno. The place where I dyno'd last is at least 5hp higher than the place I use to dyno. They're both dynojets, but different models.

 

Wow, I should send you my dyno graph- I'm pulling the same numbers at the moment. 256 RWHP, 245 RWTQ.

This is on a 5AT.

 

Good numbers man. Saw that you had good gains with the unichip. Go ahead and post the files up here. But be sure to zip them up; .drf's aren't valid extensions for attachments here.

I assume this is on a dynojet right?

 

I agree, assuming the machines are the same make, the numbers will usually be pretty close unless the conditions are wildly different. Big correction factors will typically skew the data a bit. Now comparing a Dynojet pull to something like a Dynapack pull is a no-no because they're completely different machines and Dynapacks typically read a good bit higher. Take a gander at a Church's dyno and note how much higher those cars dyno.

 

It's not just church's. Dynapacks in general are like that. As has been discussed, dynapacks measure power to the hubs, wihch largely does away with many of the variables involved in a dynojet.

After I changed out my wheels(new tires are something like 4 tenths of an inch shorter), I have yet to be able to match my last dyno numbers with the stock wheels/tires. With a dynapack, this variable doesn't even exist in the system. I've read where dynapacks can vary as little as .5% run to run to run; excellent for tuning and repeatability. Dynojets, on the other hand, in my own experience, show gains run after run after run, even without cooldowns. One would have to assume that there would be some upper limit, but I've not found it yet.

For example, back in december when we did the muffler swap on Cheryl's car, it was dyno'd 8 times. 3 times for the baseline, then two more times after the muffler swap, when we noticed that the a/f sniffer was not hooked up. So she got another 3 tunes(for a total of 8). Each run was better than the last. Not very repeatable IMHO.

 

A Dynapac is brake dyno so the operator an vary the load, so yes, they are great for tuning. As for Dynojet repeatability, it's been my experience that they're dead on (within 2-3whp), run after run, assuming the car has gotten cooled a bit between passes. However, I've watched a handful of 350Zs and g35s dyno and they're terribly inconsistent. Like you said, run after run they keep gaining power. I've never seen another car do this except for turbo/SC cars. What is odd is the G/Z is inconsistent on the dyno, but it's very consistent on the track. Even on back to back hot laps or with 1 hour cool downs, my G35 is within .1 seconds and .5mph on each run.

 

From all the dyno runs I have seen from a Z/G if they do run for run and not stop, they keep loosing power due to heat not gain.

 

I noticed the same thing on my G. The best run was the last one, whic was about 4 bhp higher than the first. Seems counterintuitive but...

In terms of consistent track times, you're going to need a lot more than ~+5 bhp to make a noticeable difference.