I want to have Bob dyno'd but know nothing about them.

What should I look for?
Which ones are more accurate?
Which ones should I avoid?
Which ones should I look for?

Thanks for any/all info?

 

Anything will work but make sure they can give you SAE corrected numbers. That will give you a better read and more realistic numbers.

 

Well, I learned something today....I have a Dyno-Jet dyno in a shop abou 5 minutes from me.....may have o do it his spring!

 

The reason I'm asking is I've found two shops, each has a different machine, each says theirs is better than the other!

 

They were both lying.(or telling the truth)
But the both want your business.

 

Your numbers are going to be different on pretty much any dyno. Plus there are alot of variables that need to be taken into effect. Dyno numbers are as far as i can tell are more to give you an idea of whats going on.

 

I know that engine dyno numbers are very subjective. It depends quite a bit on the skill level of the operator, how recently the dyno was calibrated, the software and the actual dyno. It is impossible to get the same numbers from two different dynos, because of how the software was written and it's number rounding ability. Also, when a pull is made, a dyno only samples "X" number of times per second, the more samples, the more accuracy. However, even this can pose a problem if the sample taken is at a time in the curve when power is not at peak.
I'm not sure if I am explaining this clearly, but I do know that all the race shops employ one or maybe two people to do all of their engine dyno work. And, these people are trained to make a pull the same way, every time, to reduce the chance of "operator error". For this reason, a good dyno operator is worth his weight in gold to most professional race teams.
Most chassis dynos I have been around are really a "best guess" dyno. Their use is more to compare tuner results from one modification to the other. They certainly have their place, because not everyone can pull their engine out and put it on a SuperFlow or DTS and make changes to see what is happening to their power curve. But, I wouldn't get too worried about the actual numbers. There is an old saying in racing "We race the cars, not the dynos".
If you want good numbers, make sure you take your car in on a dry day with high barometric numbers, because most shops don't "correct" their numbers back to sea level. Like I said the numbers can be very subjective.

Pat

 

I've been loking around and it seems there are at least two basic styles; one uses drums that the car's wheels turn, and the other they remove the wheels and actually bolt on.

Opinions?

 

I would just go with the "rolling road" version. A HHR is not going to generate enough HP to cause wheel spin thereby compromising the dyno numbers. The "rolling road" dyno has been the standard in American made dynos for years. SuperFlow and Land & Sea pioneered the performance chassis dyno and most everyone compares their numbers to a SuperFlow. The hub-mount style dyno is a more recent design that I think came from Australia or New Zealand. It's an interesting concept, but I really don't think it's a better concept.
Personally, I'd just go with the group that offers the best value with the least hassle. Get it in, get your numbers, make your necessary tuner mods and get out. Do you really care if your HHR makes 199 or 201 HP? If someone doesn't believe you or your numbers, just take them out to the Gateway and settle the issue there. After all, it's one of the best racing facilities in the country.