(i wrote this up and they made it a sticky over on DF)
There is a lot of confusion and misinformation it seems about dyno’s and dyno tuning. While I am by no means an expert I have been a dyno operator for five years and partaken in several different classes on the subject. So here is a little break down of how a dyno work, what kind of dyno to use, and how to make sure you get your moneys worth from your time on the rollers.
How a dyno works
All dyno’s measure the torque your truck produces by measuring the amount of torque your tires put on the roll set via a strain gauge built into the roll set. This information is then put into a computer program which takes that number along with your engine speed (more on this later) and puts them into a simple math equation (Torque x Engine speed) / 5,252 = Horsepower. This is the basic function of any dyno and what most people want to know when going to a dyno.
Types of dyno’s
Inertia dyno – this is the most common and cheapest type of dyno used in aftermarket shops. It uses a preset load (weight of the roll set) to load the vehicle while performing tests. While still a semi accurate test of a vehicles horsepower and torque potential these dyno’s are not really suited to large vehicles like diesel trucks or anything with a turbo.
Load cell dyno – this type of dyno looks just like an inertia dyno but with the addition of a type of brake or power absorber (eddy current) to simulate a load on the vehicle. These dyno’s are found at high end aftermarket shops, tuning centers, and aftermarket manufactures and OEM’s.
Types of dyno tests
HP and TQ run – this is what most people think of when they think of a dyno run…however it is far from the best use of a dyno. This is what will most likely be done at any dyno day you attend. You will get your truck into 4th gear (1:1 drive) and accelerate to red line. During this and just about any other test on a dyno you MUST remain in that gear to get accurate and useable data. These test can be preformed on any type of dyno with or without a load cell, normally the load cell is off when doing them on that type of dyno.
Steady state test – this is where a load cell dyno shines, because an inertia dyno cannot perform this type of test. Steady state testing is what is used to smooth out EFI maps and really get a tune up close before street testing. The truck is set at specific rpm and load is increased to run the truck the whole way through the map. As you put your foot down the eddy current absorbs the power your truck is making keeping it at that rpm while at the same time adding more load (think climbing a hill in 6th gear with a jag on…the father your go up the hill the more load you put on the motor).
Sweep test – this is really the best way to get good HP and TQ numbers out of a diesel pickup as well as good data logs to send to your EFI tuner or read for yourself. In this test a start and stop speed are determined by test runs to see how low and high of an rpm you can go in ONE gear. Then the info is put into the computer and the truck is brought to the start speed and held there with the eddy current. You can then tip into the throttle and build your boost and when ready tell the dyno operator and they will release the eddy current enough to let your truck accelerate through the rpm range while still adding enough load to keep boost up like on the street and draw the run out long enough to get good data.
What to do on your day at the rollers
Before you even make an appointment – talk to the dyno operator. Find out what type of dyno they have; is it a load cell dyno? What type of tests can you do? What engine parameters can you monitor? How much is it pre hour? If it’s a real dyno cell will your truck fit? Are they ok with diesel smoke? Do they have an optical eye to pick up an RPM single off your crank pulley? This is the easiest way to get RPM off a diesel and if they don’t have it or another way to get RPM they can not give you HP numbers only TQ.
Before you get there – make sure your truck is in good running order and clean as it can be. Fresh air filter, oil filter, oil, ect. Make sure your batteries are in good condition if you will be spending the day doing reflashes. Depending on the dyno you might want to think about removing your outside duals for the six wheeled guys (saves you time and money). Have your goals for the dyno session written down so you can hand it to the operator when you get there.
When you get there – listen to the dyno operator and do what they say. Most shops drive your truck on and off and run the tests themselves. Make sure your comfy with the way they strap it down. Four straps on the back and two in the front minimum for a diesel truck. Hand them the paper with everything you want to accomplish that day and talk about the best and safest way to get the results you’re looking for. Any and all engine parameters they can monitor easily should be hooked up to the truck (boost, EGT, ect) the more info you have on the screen the better. Most shops don’t charge extra for these they just charge the time it takes to hook up…the exception being A/F because the equipment has consumable parts…but hardly any shop will have a diesel A/F meter.
During the runs – while most shops will doing the driving some like the one I worked for let the owner drive and I rode shotgun. No one knows your truck better then you and you can tell when something is amiss before they can usually. If something is amiss on a run DON”T HIT THE BRAKES! Just let off the throttle and tell the operator to hit the abort button. If things are going smoothly be happy and enjoy your day if there not say something remember you’re paying them not the other way around.
After your done - post up how bad ass your truck is!!
There is a lot of confusion and misinformation it seems about dyno’s and dyno tuning. While I am by no means an expert I have been a dyno operator for five years and partaken in several different classes on the subject. So here is a little break down of how a dyno work, what kind of dyno to use, and how to make sure you get your moneys worth from your time on the rollers.
How a dyno works
All dyno’s measure the torque your truck produces by measuring the amount of torque your tires put on the roll set via a strain gauge built into the roll set. This information is then put into a computer program which takes that number along with your engine speed (more on this later) and puts them into a simple math equation (Torque x Engine speed) / 5,252 = Horsepower. This is the basic function of any dyno and what most people want to know when going to a dyno.
Types of dyno’s
Inertia dyno – this is the most common and cheapest type of dyno used in aftermarket shops. It uses a preset load (weight of the roll set) to load the vehicle while performing tests. While still a semi accurate test of a vehicles horsepower and torque potential these dyno’s are not really suited to large vehicles like diesel trucks or anything with a turbo.
Load cell dyno – this type of dyno looks just like an inertia dyno but with the addition of a type of brake or power absorber (eddy current) to simulate a load on the vehicle. These dyno’s are found at high end aftermarket shops, tuning centers, and aftermarket manufactures and OEM’s.
Types of dyno tests
HP and TQ run – this is what most people think of when they think of a dyno run…however it is far from the best use of a dyno. This is what will most likely be done at any dyno day you attend. You will get your truck into 4th gear (1:1 drive) and accelerate to red line. During this and just about any other test on a dyno you MUST remain in that gear to get accurate and useable data. These test can be preformed on any type of dyno with or without a load cell, normally the load cell is off when doing them on that type of dyno.
Steady state test – this is where a load cell dyno shines, because an inertia dyno cannot perform this type of test. Steady state testing is what is used to smooth out EFI maps and really get a tune up close before street testing. The truck is set at specific rpm and load is increased to run the truck the whole way through the map. As you put your foot down the eddy current absorbs the power your truck is making keeping it at that rpm while at the same time adding more load (think climbing a hill in 6th gear with a jag on…the father your go up the hill the more load you put on the motor).
Sweep test – this is really the best way to get good HP and TQ numbers out of a diesel pickup as well as good data logs to send to your EFI tuner or read for yourself. In this test a start and stop speed are determined by test runs to see how low and high of an rpm you can go in ONE gear. Then the info is put into the computer and the truck is brought to the start speed and held there with the eddy current. You can then tip into the throttle and build your boost and when ready tell the dyno operator and they will release the eddy current enough to let your truck accelerate through the rpm range while still adding enough load to keep boost up like on the street and draw the run out long enough to get good data.
What to do on your day at the rollers
Before you even make an appointment – talk to the dyno operator. Find out what type of dyno they have; is it a load cell dyno? What type of tests can you do? What engine parameters can you monitor? How much is it pre hour? If it’s a real dyno cell will your truck fit? Are they ok with diesel smoke? Do they have an optical eye to pick up an RPM single off your crank pulley? This is the easiest way to get RPM off a diesel and if they don’t have it or another way to get RPM they can not give you HP numbers only TQ.
Before you get there – make sure your truck is in good running order and clean as it can be. Fresh air filter, oil filter, oil, ect. Make sure your batteries are in good condition if you will be spending the day doing reflashes. Depending on the dyno you might want to think about removing your outside duals for the six wheeled guys (saves you time and money). Have your goals for the dyno session written down so you can hand it to the operator when you get there.
When you get there – listen to the dyno operator and do what they say. Most shops drive your truck on and off and run the tests themselves. Make sure your comfy with the way they strap it down. Four straps on the back and two in the front minimum for a diesel truck. Hand them the paper with everything you want to accomplish that day and talk about the best and safest way to get the results you’re looking for. Any and all engine parameters they can monitor easily should be hooked up to the truck (boost, EGT, ect) the more info you have on the screen the better. Most shops don’t charge extra for these they just charge the time it takes to hook up…the exception being A/F because the equipment has consumable parts…but hardly any shop will have a diesel A/F meter.
During the runs – while most shops will doing the driving some like the one I worked for let the owner drive and I rode shotgun. No one knows your truck better then you and you can tell when something is amiss before they can usually. If something is amiss on a run DON”T HIT THE BRAKES! Just let off the throttle and tell the operator to hit the abort button. If things are going smoothly be happy and enjoy your day if there not say something remember you’re paying them not the other way around.
After your done - post up how bad ass your truck is!!
