Chassis Dyno Mini-FAQ

[Matt95GT]

*Pardon the dust - this is a work in progress.*

Q: How can I locate a chassis dyno in my area?

A: Try one of these web locators:
Dyno locator (http://www.raceindustry.com/dyno_search.php)
DynoJet specific locator (http://www.dynojet.com/dyno_centers/automotive/index.php)

Some larger events at dragstrips or sometimes car shows will often have a portable dyno. The even coordinator could most likely confirm this.

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Q: How much does it cost?

A: Typical price is about $70-100 for 2-3 pulls.

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Q: Can I split up the pulls with a friend or 2 to save money?

A: No. Most of the time and labor involved with a chassis dyno is vehicle loading and preparation. The actual pulls are done consecutively with very minimal or no time wasted in between.

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Q: The stock horsepower & torque specs are much higher than my results, what gives?

A: Automakers specify horsepower an torque ratings at the crank of the engine. Since a chassis dyno measures this at the wheels, losses will occur due to mass/friction of the transmission and other components such as drive shafts, bearings, etc.

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Q: Is there a minimum performance requirement or minimum number of mods needed?

A: No. Any stock Grand Am can be run on a chassis dyno.
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Additional links:
http://www.ktrperformance.com/dyno_tuning/dyno_faq.htm
http://www.bristoldyno.com/info/procedure.htm

[JoeyK]

Hey man, that's a great link to have. Thanks!

[99GrandAMSE]

Very cool information!! :)

[urweak]

Some places do offer a discount for 2 or more people (but like you said, you cant pay 70 bucks and then run two cars, you might get a deal down to 50-60 per car)

And most places with dynos will run a dyno day.

Something good to know for twin cam (maybe even quad4 owners) the pink wire that connets to the ignition module is where they want to clamp onto to get a tach signal.

[Bjornboy81]

Do you have to know what you're doing when you go in or are most places willing to help you out?

I've never done it before, so I'm not sure how it works, I'm not sure of the process of dynoing...I don't want to walk in and look like an idiot :)


Good info BTW...thanks Matt :)

[Matt95GT]

Originally posted by urweak
Some places do offer a discount for 2 or more people (but like you said, you cant pay 70 bucks and then run two cars, you might get a deal down to 50-60 per car)

And most places with dynos will run a dyno day.

Something good to know for twin cam (maybe even quad4 owners) the pink wire that connets to the ignition module is where they want to clamp onto to get a tach signal.

Yup, good point... if a couple buddies go together you can often talk em into a few bucks off for each of you.

Dyno day rentals... info I need to add. I want to get some going prices for hourly/day rentals to add.

Planned on adding specific tach signal info too... especially for 2.3/2.4 owners. The guys spent nearly 20 minutes trying to get a signal on mine... I was the only customer to end up up on the dyno helping them.

Originally posted by Bjornboy81
Do you have to know what you're doing when you go in or are most places willing to help you out?

I've never done it before, so I'm not sure how it works, I'm not sure of the process of dynoing...I don't want to walk in and look like an idiot :)


They do everything at most places (especially the portable trailer units that use a lift). You sign waiver, specify max RPM they rev to, pay, hand over keys, get printed graph. Dyno tuning shops (permanent dyno installed) offer a bit more "hands on"... although most have a tech working with you to operate the dyno itself.

Another good one to add... thanks. Keep em coming... I'm trying to get a few more together until we have a nice little collection of useful information.

[Bjornboy81]

If and when I go, I'll see if I can get some info on what wires their tapping (if any) so you can add some stuff for the 3400 guys :)

Thanks for the info Matt.

[xonelith]

The few dyno's i've been to, ask what gear should they run the dyno in.

I've heard some mixed answers on this question. For the 4 spd auto's, some say 2nd, some say 3rd (don't do 4th, it's overdrive). Maybe add some info on what gear to run in.

[Matt95GT]

Originally posted by Bjornboy81
If and when I go, I'll see if I can get some info on what wires their tapping (if any) so you can add some stuff for the 3400 guys :)

Thanks for the info Matt.

Easy for any traditional (non-IDI) ignition system... clip goes around any spark plug wire.

Thanks for causing me to think of more good questions and answers to add. :)

[Matt95GT]

Originally posted by xonelith
The few dyno's i've been to, ask what gear should they run the dyno in.

I've heard some mixed answers on this question. For the 4 spd auto's, some say 2nd, some say 3rd (don't do 4th, it's overdrive). Maybe add some info on what gear to run in.

Great idea... and that reminds me of other needed details... gear, automatics and preventing mid-run shifts, speed governor, etc. Thanks.

[urweak]

for the isuzu in the 95-98 (99?) GAs 4th gear is closest to 1:1, but you will hit your speed governer, so you have to do the pull in 3rd

[VanishingImage]

yea 3rd on the auto is what I see most of the time. Thats what gear I run when I go at the track.Plus it has more torque

[99blackSE]

With 99+ SE's with the 4T-45E and the 3.05 FDR, 3rd will run into the governor, have to do it in second.

[Pte Socks]

wouldnt 2nd run into the govenor? I cant remember which gear I ran my dyno's in, as the shop that does mine did all the work. I do konw that drive will be 10 hp and 10 ft-lbs of torque lower than other gears.

[Azrael]

For the 3x00 V6's the tach signal for the dash cluster is the white wire coming from the ignition control module.

Something good to add to the FAQ: How do you keep an autotrans in one gear? As soon as you floor it it'll downshift to 2nd or first.

[Matt95GT]

Good stuff, I'll get to updating soon.

Originally posted by Azrael
For the 3x00 V6's the tach signal for the dash cluster is the white wire coming from the ignition control module.



An inductive pickup for tach signal going to dash often doesn't work. Mine didn't. On a 3x00 a plug wire would be a better choice.

[DontPassTheFence]

Originally posted by Azrael
For the 3x00 V6's the tach signal for the dash cluster is the white wire coming from the ignition control module.

Something good to add to the FAQ: How do you keep an autotrans in one gear? As soon as you floor it it'll downshift to 2nd or first.

With all GM transmissions Ive driven (89 auto retta, 01 GASE, 03 Cavy) I dont remember the transmission models...

They all will stay in second if you shift it into '2', and third if you shift it into '3' You can manually shift an automatic transmission, its just not a good idea for fuel economy, or transmission life.



Also, on the note of the 1:1 f the izusu 4th gear, you can get a good graph of most of the usable power ifyou use 4th, the limiter shuts it down at 5K, or near there. Id want to do 2 dyno runs, one in third (to 5k) and one in fourth to see the actual difference (even though I know peak hp comes a bit later than 5K on the LD9)

[slowbird]

Our 4 speed auto should be run in 3rd...that is the gear that is 1:1

If the Dyno guys say it's okay if you just start at 120KM/h with the gear selector in 3...the car shouldn't downshift. That'll start you around 3300RPM.

I also heard something about unplgging the tranny connector...which will default the car into 3rd gear.

[gectek]

yah ur right, itll do 3rd only, and also you should only do trans in 1:1 gear ratios, or the nearest gear to it. 3rd will not put out more torque than 1st or 2nd, that is basic gear theory, also if you put the trans in 1st, itll run only in 1st to the rev limiter, which in the 99+ ga stock is about 5800-5850maybe even 5900 on the tach, but you cannot use that as an accurate rep of the acutal RPM, that is why you need the pickup and even a scan tool on it. also if you put the shifter in 2nd it does not pick second gear, it will start out in 1st, then shift to second and will still downshift to 1st, and 3rd is the same way...i wouldnt start the car at 3300 rpm because then you are losing the place where the torque curve starts to engage and you cannot start to gauge your powerband right. just unplug the conn to the trans, it will disable both solenoids and it will run in 3rd, just put the range selector in D or 3rd, it doesnt matter. the reason you cannot in reality gauge the output of the trans in another gear like any overdrive or underdrive gear is the fact that some torque will be lost in the heat transfer and the extra power needed to turn a larger gear in any underdrive gear and the speed in any overdrive gear in a manual, and also with an auto, with all the different fluid passages that engage and the differences in rotating mass and engaged parts, plus the fact that the TCC doesnt lock up until you hit 3rd, or if you discon the electrical connector, then you cannot just say ok well the 3.05 FDR says that 3rd is 1:1 and 4th is .68:1 and use that to factor in more power...also in the 4 cyls the stall speed of the converter is different than the stall speed on the 6 cyls and not all the 6 cyl trans are stalled the same either, so that will give different readings as well until you reach the stall speed of the converter and go into lockup also. and also the 4 cyls are geared different than the FDR of what you see in the 6 cyls, due to an underdriven chain drive, which usually puts the FDR at 3.42 or 3.63, and also 3.05, so in second gear or 4th they will not be the same with power output...

if you go to a dyno shop and they ask what gear to do the pull in, i would seriously go somewhere else. if they do not know what gear to use, then they should look it up and the should know how to run the pulls and how to hook up the leads. they get training on the dynos, so they should know how to use them. if it seems to you like they dont, then save your money and go somewhere else. if they mess up then you are going to have skewed results and you really arent going to know because they have the dyno and they SHOULD know what they are doing. also changing the tires/rims on your car to anything other than stock will also change the output of your car, not only in weight and rotating mass and the extra dimensions of the rim/tire, it also changes the effective ratio of your overall gear ratio. that is why it is better to run stock sizes to get the right numbers