How much stress does a dyno put on a car ?

[Bo knows]

A local high performance shop in our area is having a dyno day in a few weeks and the owner has invited me to put the Viper on the dyno. I'm a little hesitant because I have heard some horror stories about this. A good friend of mine had his engine blow (start knocking ) while it was on the dyno. He said he saw his shift light come on but the dyno operator just kept reving the engine higher. I've heard other tales of woe from people who have had cars dynoed also. Looking for some input from you dyo guys. Thanks !

Bo don't know

 

[LETHAL GTS]

1. You have some interesting questions......
2. You are in control of your gas pedal, so take your foot out of it when you want.
3. Your car has a rev limiter or in the case that it is disabled for what ever reason, don't rev your car above 6000RPM.
4. Typically on these engines, you will start loosing power and torque after 5800 RPM anyway. There is no need to rev any higher.
5. Go get your car dynoed!
6. It will not hurt your car anymore than running it to the floor down the highway. With the exception that there is not as much air flow to cool your engine and components.
7. Report back with the results.

 

[Anaconda]

Make sure they do the pull in 4th gear.

 

[Casey]

I think that depends on how much power you have!

 

[Supercharged Vipermad]

Lethal...there ARE some locations that will NOT let the owner do the pull. As unnerving as it is...that is the way it is. Sadly, there may not be another facility anywhere nearby.

One has to build a relationship/friendship with the shop IMVHO. Go there, hang out, make sure they know about your car and Vipers in general. At the end of the day, they are likely gearheads like us and just need to get familiar with the car.

I plan to let a friend here (he has built his turbo Vette on his own, and works the dyno) do my car in a couple weeks. He is not new to forced induction, and has probably 100's of pulls under his belt. Mind you...that doesn't mean I am not hesitant!! !!!

 

[Bo knows]

At this dyno facility they do not let the car owner do the pull. The dyno operator gets in your car and does it. If I was allowed in the car I wouldn't be so hesitant to have it done. Here's another thing that scares me, they make you sign a release freeing them from any responsibility if anything should go wrong. So far I haven't heard anything positive that would make me wanna do this.

Bo still don't know

 

[Anaconda]

MOST places won't let you do your own pulls because of insurance reasons. A lot of shops won't even let you out in the area (though most won't say anything, even though you aren't supposed to be there).

 

[AviP]

At this dyno facility they do not let the car owner do the pull. The dyno operator gets in your car and does it. If I was allowed in the car I wouldn't be so hesitant to have it done. Here's another thing that scares me, they make you sign a release freeing them from any responsibility if anything should go wrong. So far I haven't heard anything positive that would make me wanna do this.

Bo still don't know

My GTS is bone stock and I just dynoed it for the first time in June this year with no problems. 397hp. They tie it down but like anything that wears and tears something could break. The dyno doesn't add any more in terms of risk than 6000 rpm on the road would. For the <1 minute it takes to do a run, you should do it. Does bo now know?

 

[ACELLR8]

There is a dyno shop in Southern PA that will let ya dyno your own car! They stand beside ya, and you have a visual on the air fuel mixture and rpm data on the PC. They will break the dyno once you let off the gas, etc.
Very Nice shop, even has a 4 wheel dyno.

http://www.xoticmotorsports.com

 

[LETHAL GTS]

Lethal...there ARE some locations that will NOT let the owner do the pull. As unnerving as it is...that is the way it is. Sadly, there may not be another facility anywhere nearby.

One has to build a relationship/friendship with the shop IMVHO. Go there, hang out, make sure they know about your car and Vipers in general. At the end of the day, they are likely gearheads like us and just need to get familiar with the car.

I plan to let a friend here (he has built his turbo Vette on his own, and works the dyno) do my car in a couple weeks. He is not new to forced induction, and has probably 100's of pulls under his belt. Mind you...that doesn't mean I am not hesitant!! !!!

I simply wouldn't dyno my car there.
But that's me.

 

[ruckdr]

I don't/can't do the pull: I DON'T Dyno, pure and simple.
Later,

 

[kickinasp]

Having your car Dyno'd is no big deal... most if not all shops wont let you drive your car, and frankly...I would want someone experienced do it anyways..I have seen some of you drive! Just make sure it is properly strapped down, the cooling fan is installed in front of your car (blow air thru the Rad to cool the engine), and the operator does the pull in 4th gear and runs it up no further than 6,000 RPM's. Then then lift, put the car in neutral and let it ease down with some help from the cars brakes. Its a simple procedure and will give you a great base line as to how good your engine is...they usually do 2-3 runs. On manual transmission cars the accepted standard is 12-18% loss of HP measured at the wheels. Which means the final number they give you is about 12-18% lower than the actual HP measured at the flywheel.

 

[Viper4Christ]

A stock Viper reg dyno, but on a mustang dyno where it loads against the car a stocker might not be the best choise. Unless your running Paolo or hennfer type power. And believe it or not the dyno owner where Paolo did his GTS had him lock the converter up and only rev it to about 4600 RMP, not even the standard 5200 where the Vipers TQ and HP levels cross and still made 1276 HP and 1509 FTLBS...

 

[SYNFULL]

Let me see if I understand this- when you have your car dynoed they only wind it out in 4th gear? There is no shifting through all the gears?
Gary

 

[Marv S]

That's correct. Look at a dyno graph and it is only a single gear used in the test. 4th is used because it is direct 1-to-1 ratio through the tranny.

It does build a lot of speed with stock 3.07 gears and some dyno shops want to test in 3rd gear.

as for revving the car up - I've seen these motors bounce off rev limiters at auto-x's , like at the zone events & voi's, run after run after run and not break.

Let me see if I understand this- when you have your car dynoed they only wind it out in 4th gear? There is no shifting through all the gears?
Gary

 

[Jack B]

Unless you have mods the car will see peak hp at about 5300, why go further?

The dyno does put a bit more stress on the car since you typically don't floor the car at 2000-2500 in fourth gear. Since the car is not acclerating (as quickly as lower gears) the whole drive line has more stress for longer. That is why you don't start a nitrous run till you are 3000 or over. A trick to make a run look good is to start the nitrous run before 3000, the torque goes way up versus starting later, but, it is dangerous.

I must have done 25 nitrous runs in third gear while tuning this year and all was well, on my first dyno pull this year (in fourth gear) I sheared all the ring gear bolts. On the other hand, stock or near stock cars the dyno should not be an issue.

 

[Jerry Dobson]

The Dyno definitely puts more stress on a car than street driving. That rotating drum has resistance and it is putting a load on your mechanicals. Since your tires are not spinning, your entire drive train is under stress.

Most shops would never consider allowing a customer to Dyno their own car. The liability would be a factor if something happened. In many of the newer shops, customers can not be in the Dyno area at all during a pull.

 

[Viper Specialty]

I respectfully beg to differ on a Dyno putting more stress on a car than the street. First off, dyno runs are done in 4th gear, usually. 4th gear cannot apply the same torque load to the drivetrain (read twisting of engine/trans/diff mounts against the frame) as any gear below that on the street where traction is available. In the case of most Vipers, a roll-on in first or second is quite easily possible on the street- short of Canadian roadways, they are VERY slick compared to the USA asphalt mix. Second, the internal forces (read Crankshaft-flywheel-clutch-trans-internal trans) are always going to be limited to the max TQ the engine can produce in any situation where max torque load is applied from WOT. The engine and trans are one single bolted-together system, their load will not vary based on external conditions such as shifting drivetrain, etc. Lastly, it takes much more force to linearly accellerate a 3500 lb. car, than it does to SPIN-UP a 5000 lb. drum supported on bearings. This is quite evident simply by the fact of how long it takes to do! On the street, starting in 4th gear at 2000 RPM, floor it. It will take quite a while to reach redline- a hell of a lot longer than it does on the dyno. proof enough? I would think so.

I will however concur that the temperature differece on a dyno VS. a street drive is highly different. However, the amount of time a pull takes, is not enough to cook your drivetrain by a longshot. as long as there is sufficient air to cool the engine, it should be fine.

 

[Viper Specialty]

PS- I did 22 back-to-back pulls in my personal car not more than a few weeks ago. I took temp readings of various parts of the car during these pulls, nothing out of the ordinary. the only thing to get cooked on that day was my brain!

 

[Jack B]

Dan:

It still is not good to go (high torque engines)wot in 4th gear at 2000 rpm. Compare the two:

1. Launch the car at 5000 in 6th gear - all the stress is on the drive line the car won't move and you will break swomething if the clutch holds. Do it with nitrous and you will break the crank.

2. Launch the car at 5000 in 1st gear - the drive line stresses are far less because the car can accelerate.

It is a little far fetched (maybe not) but there is a lot stress on the drivetrain with any high numerical gear pull from a low rpm. The more power you have the bigger the issue. i am not trying to knock the dyno, I have over 100 pulls in the last five years. It is just not debatable the stress is there.

There still is no better way than a dyno to do some fine tuning. However, road tuning (where possible) especially in third gear puts far less stress on the driveline. I don't know how much you have worked with logging systems, but, third gear pulls on the road with the right sensor inputs can give you as much or more data than a dyno.

 

[Viper Specialty]

Jack- while I see where you are coming from, you left out one VERY, VERY important fact in your analysis;

When you are launching a car, you have two factors to contend with. First of all, you have the torque the engine can produce, thats a given.

Second, you have the momentum of the engine components being absorbed into the driveline.

However, The second factor ONLY, and I repeat, ONLY comes into play while the clutch is being engauged- such as from a launch. However, do you ever lauch on a dyno? nope.

The forces have to be absorbed into the driveline because the upper gears are not capable of spinning the tires, even in a launch situation. the driveline itself must be able to displace the engine's torque, as well as the momentum of the crank, and slow it down in a given timeframe. For instance, an engine that makes 500 lb/ft of tq spun to 5000 RPM, and then have the clutch dropped, could very well instantaneously produce upwards of 1500 lb-ft of tq. However, that INSTANT, may be enough to break parts. a Dyno, will never see that instant, becuase there is no launch involved.


I will check back on this post in the morning- I have far too much alcohol floating around to continue with this debate at 2:51 AM... LOL

 

[VIPER D]

Dan

you can 100% launch on a dyno. I know mustang dyno's have a 1/4 mile run simulator on it that can give you et's as well.


vd..

 

[Viper Specialty]

Viper D- While that is true, that was not the basis of this argument. Thats a 1/4 mile simulator, not a "dyno run." to gauge HP/TQ. And even still, if you did use that simulator, would you be launching in a high gear? highly doubtful.

 

[VIPER D]

your right dan


vd..

ps I have a problem keeping the wheels from spining when on the dyno at about 700 rwhp they blow loose.


I will be on the dyno tomorrow to tune the levin hi hp and water ****


I hope for 800 rwhp we will see


vd..