Dyno Question

[Marc Lublin]

Hi all,
I have a question about dyno's. I was recently told that a tuner can actually massage his dyno to make the numbers better by changing the ambient temp setting in the computer. Forgive me if this sounds stupid, I don't know much about dyno's, but thought this was interesting.

 

[LTHL VPR]

1badgts is correct, and they are MANY more ways someone could 'alter' the numbers including the placement of the measuring equipment, adjusting altitude, bar, pressure, changing correction factors, etc....and the list goes on!

And to top it off, not all dynos are the same either. There are Dynojet, Mustang dynos, Clayton dynos,etc... and all will give you drastically different readings.

As I mentioned in a previous post about dynos, the proper way to use a dyno is for a baseline comparison after modifications are made. It is important to keep as many factors as possible consistent. At APEX, we use a real time engine diagnostic software to try to keep the variables consistent (IAT, ECT, etc...) when using the dyno. But again, it is very difficult to keep everything 100% consistent. As a result, typically we will do a minimum of 3 runs but as many as 10 in order to get consistent numbers, and normally take the average. Some dynos tend to have more conservative numbers and some more agressive. Why? Too many factors to pinpoint normally. Dynojet has even changed the software versions a few times in the last couple years, and this may effect the readings as well.

In the end, I always say honesty is the best policy. If someone inflates numbers, they are only hurting their credibility in the long run. It is discussions like these that make me feel better about the fact our dyno tends to be on the 'conservative' side. For example, we have never seen a Viper with headers and exhaust ever hit more than about 445rwhp, and on average are around 430-400rwhp.

Hope this helps!!
-Wayne

 

[Marc Lublin]

LTHL & 1 Bad,
Thanks for the responses. I guess what it ultimately comes down to is the honesty of the shop running the dyno. Wayne if you are an honest shop, which you guys seem to be, then I guess people would trust your numbers. What about tuners that don't have your honest reputation? Just a little food for thought.

 

[Jason Heffner]

Marc, I have had my dyno for about seven or eight months now and I am not aware of any way to alter temperatures or barometric pressure on the latest software. Things like tire pressure and engine coolant temperature however can slightly alter the numbers. Lower tire pressure can give a slightly lower number and an extremely cold engine can give slightly higher numbers depending on the car. I guess if your ever in doubt, just have your car dynoed at two different places before and after modifications. Like joe said, you'll know when you go to the track.

 

[Marc Lublin]

Joe,
Of course the track is the ultimate test of the car's power, but there are a multitude of Viper owners out there that don't race and would like more power on the street. The way the tuners sell the packages is through dyno HP #'s. Therefore you have rely on the tuner's honesty in his dyno graph #'s.

 

[TOOOFST]

I nominate 1badGTS as official viperclub tuner MODERATOR!

 

[Tom Welch]

I've seen lots of Vipers with just headers and exhaust make well over 450 hp on dynojet 248 chassis dyno's throughout florida. THE MODEL YEAR VIPER MATTERS.

Dynos are a tuning aid. Thats it. Find a dynojet facility and use it for all of your testing of modifications. Use the same facility for each mod. There are 8 dynojet dyno facilities within an hour and a half drive of my shop. All of them are within 10 hp of each other on any given day.

Want to know the real horsepower, take it to the 1/4 mile. The MPH clock can't be paid off, tricked, fooled and manipulated and most importantly it has no favorites!

Tom
Http://btrviper.com

1997 GTS BTR 900 SuperSnake 142 MPH 1/4 mile trap speed

 

[LTHL VPR]

Justy for reference and clarification, when I posted:

It is discussions like these that make me feel better about the fact our dyno tends to be on the 'conservative' side. For example, we have never seen a Viper with headers and exhaust ever hit more than about 445rwhp, and on average are around 430-440rwhp.

it was to provide an example of how our in-house dyno tends to read more conservatively than most.

I have seen other dynos that have posted 450+ rwhp numbers for headers and exhaust mods. My 98 GTS even posted 450+ numbers on a different dyno.

This is why I feel confident that the numbers we achieve on our dyno with our packages are conservative and repeatable.

I am not sure why these differences exist between dynojets, but they do. It could be because of the 'correction' factor dynojet uses or the software version, or the parameters,etc... In the end my advice is to stick with the same dyno machine and try to match the conditions as closely as possible between modifications.