Saturn ION RedLine Forums banner
1 - 8 of 8 Posts

·
Registered
Joined
·
4,965 Posts
Discussion Starter · #1 ·
I was going to get my CAI installed today, and I decided I wanted a baseline dyno so I know what each part roughly gives me. I brought it to a shop, and about midway through the session, I saw a sign that said "Mustang Dyno-MD". I put down 187WHP and 177FT-LBS. I was wondering why on a mustang dyno, did my car make so much LESS HP than so many others have made on the dynojet dyno's? I don't know the actual differences, but I know that cars like ours make less HP on the Mustang one, I'm just not sure why. Anyone know?
 

·
Registered
Joined
·
293 Posts
It all lies in the method used to produce a horsepower figure. I may be wrong, but I think it works like this:

A Dynojet measures by how the car accelerates a constant mass (the roller).

A Mustang Dyno actually loads the roller and has some sort of resistance. It's arguably more accurate than the Dynojet, but almost always reads lower numbers.
 

·
Registered
Joined
·
1,243 Posts
linenoyz said:
It's arguably more accurate than the Dynojet, but almost always reads lower numbers.
Argued only by mustang salesmen. The mass of the dynojet is always constant and the dia of the roller is always constant. Formulas used by the computer will read an accurate HP every time from session to session. THe mustang dyno uses an electric motor that is loaded for resistance and this is used by the computer for the calculation of the HP. The electric motor IS NOT the same every time. Heat build up varies the output of the electric motor and can and does lead to a variance of numbers from run to run (even on the same day at the same location). The static roller of the dynojet is what it is and nothing else. THe mustang dyno can be loaded to varing degrees to simulate different situations and some shops prefer it for this reason.
 

·
Registered
Joined
·
4,965 Posts
Discussion Starter · #4 ·
Blu_Redline said:
Argued only by mustang salesmen. The mass of the dynojet is always constant and the dia of the roller is always constant. Formulas used by the computer will read an accurate HP every time from session to session. THe mustang dyno uses an electric motor that is loaded for resistance and this is used by the computer for the calculation of the HP. The electric motor IS NOT the same every time. Heat build up varies the output of the electric motor and can and does lead to a variance of numbers from run to run (even on the same day at the same location). The static roller of the dynojet is what it is and nothing else. THe mustang dyno can be loaded to varing degrees to simulate different situations and some shops prefer it for this reason.
For this reason (well, these reasons) which dyno would be more "accurate" for our cars. I knew the Mustang dynos seemed to always read lower, and that the rollers have a resistance, so what if the resistance is set wrong? Will it actually read lower than intended? And how are these resistances determined? I would have prefered to be on a Dynojet dyno, but this is what was available when I needed it. Living in SUNNY (and very hot) south Florida, the heat thing bothers me. When it's constantly 90+ degrees in the shop area, plus whatever heat is generated by use, the Mustang dyno just doesn't seem to be the most reliable one for numbers.
 

·
Registered
Joined
·
1,243 Posts
I talked to the guy that owned the dyno that did mine for quite a while. (he is a former autox'er and still does a ton of work on SCCA cars) He checked out both dynos and checked out shops that had each. His conclusion was that the dynojet was better for a list of reasons. Major one was he only needed one dyno to do 75 HP to 1500 HP whereas the mustang dynos only have a limited range (ex. 100 - 300, 300 - 500 or something close). With a mustang dyno he would have been limited to what his shop does the most ( low HP Mazda Miatas and such up to 200 HP) and cut him out of doing Corvettes, Porsches, AMG Benz's, yada yada. THe drum and roller dia never changes and is not affected by temp. Math formulas never change, therefore the computer calculates how fast the car moves the given mass and logs it to the rpms. It takes X amount of HP to move the mass in Y time. How long did it take your engine to move the drum to 6250 rpm? That answer yields the HP of the engine. The mustang dyno is dependant on the info that loads the resistance of the dyno being correct and those who are running it to be properly trained. THat and the electrical resistance builds up heat which changes things - constantly. That and the shop owner pointed out that you have a drum belt and resolver on the dynojet while the mustang has a roller with a belt to the motor and another belt to their resolver, more parts- more variables. He did say that each style of dyno had their good points and an area where they stood out. He also said that mustang now makes a model similar to the dynojet's static drum for those who prefer that type of dyno and that Dynojet is making an electrical resistance dyno similar to the mustang to answer the segment that prefers that style. He went on to say that each company's salesmen will tell you why their's is the best but the ultimate test is what it is doing in the field. That is where he said he found the dynojets reflected HP readings that were constant with published figures more than not. The dynojet that did mine had a weather station on it and corrected for altitude and converted to SAE, so the same dyno hauled out to Denver would yield the same numbers out there assuming the higher elevation would allow the test car to make the same HP. Good enough for me. Oh, and he said that in the case of the dynojet doing 5 spd FWD cars, a 3rd gear pull or a 4th gear pull is almost identical to a one to one axel ratio. Third being over 1:1 and 4th being under 1:1 on my car gave me 216 and 214 respectively, that's less that 3/4 of one percent difference.
 

·
Registered
Joined
·
4,965 Posts
Discussion Starter · #6 ·
I didn't feel like quoting that whole response ^^^ becuase mine would have looked REALLY long, but thanks for the info. I had actually heard most of what you said at some time or another, but it was good to see it all in once place. There were a few other things that had bothered me about the shop, so, I will be looking for a shop down here with a Dynojet instead. Anyone in south Fla. know of any?
 

·
Registered
Joined
·
4,965 Posts
Discussion Starter · #8 ·
I am currently down in Ft. Lauderdale for the summer, but I've been to a shop down here called CarTek Tuning, and they have an in house dyno, which I believe is a dynojet. They are Honda/Acura specialists, so I would assume they would have a dynojet. I'm probobly gonna run over there Mon or Tues. Thanks for the place though. Once I get back to school, if I need a shop, I know where to go.
 
1 - 8 of 8 Posts
Top