Dynamo Dynamometers - Engine Builder Magazine

Dynamo Dynamometers

Not every engine shop has one, but every engine shop could benefit from installing one. Sure, it can be expensive, it is loud, but engine shops with these in-house offer an extra source of income and the ability to test engines and parts. I’m talking about a dynamometer.

This dynamometer was installed by Ison Racing Engines for durability and long-term testing.
This dynamometer was installed by Ison Racing Engines for durability and long-term testing.

Not every engine shop has one, but every engine shop could benefit from installing one. Sure, it can be expensive, it is loud, but engine shops with these in-house offer an extra source of income and the ability to test engines and parts. I’m talking about a dynamometer.

Making the decision to add a dyno can be a daunting one, but it doesn’t have to be. Engine Builder spoke with a couple of shops that have installed dynos and got the scoop on what you’ll need to consider when diving into this investment.

First and foremost, you have to have the space available to set up a dyno test cell. These rooms aren’t enormous, but require a minimum space of 12’ in length by 10’ in width.

“The basic footprint of our dyno cell was 18’ x 15’ and the inside area is 12’ x 12’,” says Mike Hupertz, a senior test engineer at Ison Racing Engines.

Another consideration to take into account is your shop’s surroundings. A dyno is loud and you’ll want to make sure you stay in the good graces of your neighbors.

“One of the biggest things is the environment and local surroundings,” says Tom Nickerson, owner of NVR Racing Engines. “You want to make it as quiet as possible without obstructing the motor from running. NVR is in an industrial park area, but also in the city of Butler, WI. Four or five blocks away we have residential houses.

“We actually run two separate mufflers beside the engine with four cylinders running in each muffler and then those two run into a commercial muffler that runs straight up 10-15 feet above the building and is turned away from the residential area. We’re concerned about noise because the community is concerned about it.”

With dynos, the higher the horsepower engine you’re running, the more noise you’re going to produce. A 400 hp engine will make half the noise an 800 hp engine does. Engines around 100 hp – 150 hp are fairly quiet in comparision. If you have a 1,000 hp engine, noise can be a problem.

NVR Racing Engines built its room logically by placing it off of the engine assembly room, and leaving space for a workbench.
NVR Racing Engines built its room logically by placing it off of the engine assembly room, and leaving space for a workbench.

“Ironically, there are no decibel readings that we have to stay under,” Nickerson says. “However, we decibel tested ourselves and a dump truck driving by the building is louder than our dyno.”

Beside the cost of a dyno and test cell, which we will get to later, the space and noise are two important factors to keep in mind when deciding to install one. But let’s get back to what makes up the test cell.

Building a Test Cell

There is a wide range of materials you can use to build your dyno cell. If you’re unfamiliar with building a test cell there are recommendations available from larger suppliers like Granger and McMaster-Carr, and these suppliers can also recommend electrical, fans, motors and pumps you’ll need. Also, when you buy your dyno from aany of the major dyno suppliers, you’ll get room recommendations, potential locations and the requirements for the pumps.

“What we did was actually had INC and Soundmaster give us some quotes for building an enclosed room for us,” Hupertz says. “After looking at some dyno cells and getting a few ideas we decided that we would build our own cell. Some of the things that we did on that cell mimics others out there. Along the back wall we put a 3’ muffler chamber. The actual working area inside the cell is 12’ x 12’. We installed 18” walls, using two existing corner walls from the shop. We used metal stud construction and dry walled the outside. Before we did that, we used a brand of insulation called Roxul that is fireproof and soundproof and is 15 ¼” thick.

Hupertz started with the walls and ran all of the electric lines ahead of time. “You have to configure everything that you’re going to run in the cell. What are the power requirements for the cell? What is it going to take to run the dyno? How many outlets do you want? What is the lighting going to be?”

You want lighting that is going to give you good light. Hupertz has four, four-foot fluorescent covered lights in the cell so it is bright and clean, because he wants to be able to see what he’s working on.

“Going from there we lined our walls with Roxul,” he says. “On the backside for our muffler chamber we put 3’ openings on the back wall for our exhaust. At the top we cut holes in the wall and put two 36” fans in to extract the air and get the air moving. You need to exchange the air in your dyno cell at least seven to eight times a minute. On the exhaust side we had our two 36” fans, and on the inlet side we put one 48” fan. At the top of the dyno cell we installed two 48” open louvers that are electronically driven on the switch panel outside the cell. We flip that on and the louvers automatically open, and the ductwork is split in such a manner that it creates an even flow across the engine – one to cool it, and two to exchange the air in the dyno cell.

Companies such as Super Flow will give you dyno cell  recommendations much like this to help you build the room you want.
Companies such as Super Flow will give you dyno cell
recommendations much like this to help you build the room you want.

“Then, we had a company come in and build a complete plenum system because we didn’t want to build it. They built all the ductwork and insulated that,” he says.

Insulation is important because if you’re running something in the winter and drawing in cold air, it will sweat and essentially rain inside the dyno cell, which isn’t a good situation, Hupertz says. Insulating the outside of the ductwork stops that differential in temperature.

“On the inside of the dyno cell walls we used a perforated metal, which you can get from any industrial steel supplier,” he says. “That is what captures all the sound. We didn’t put in any windows. Some companies will put windows at the redial plane of the engine, but I didn’t want that because if there is any sort of failure, the redial plane of the engine is where it’s going to come from. We have one 36” x 48” window, which is a double-walled, explosion-proof window in front of the console.”

Nickerson’s advice for the dyno cell, if you’re building it yourself, is to take your time when mapping it out and do it logically. For instance, Nickerson positioned his dyno room right off NVR’s engine assembly room so the engines can make an easy transition from assembly to testing.

“We have a concrete block room inside the building that we run the dyno in with ducted air in and out, a steel door and explosion-proof glass in the window,” Nickerson says. “You don’t need a basketball court, but you’ll want enough room for a workbench and a toolbox, etc. Our dyno room has filled block for safety and quiet and we had a mason build the block wall, but did the rest ourselves such as the ductwork, the exhaust fans, etc.”

Pumps and Controls

Aside from thick, insulated walls, your dyno cell will require several pumps for water and fuel in order to function smoothly and properly.

“As far as pump requirements go, our dyno has a pressurized cooling tower, which runs a glycol mixture in the engine itself,” Hupertz says. “It uses the water from a tank. Dynos that don’t have a pressurized cooling vessel use the water from the tank to do two things – to control the dyno and to control the temperature of the engine. Ours differs in the fact that the water we’re using cools the heat exchanger and runs the dyno.”

Your dyno’s tank capacity depends on whether you’re going to run durability testing, long-term testing or do basic power pulls. Your tank size for raw water has to be in the range of 1,500 gallons to 2,500 gallons. Some bigger companies will just use city water and not hold or store any water.

2014-06-25 09.21.30“Our particular system uses a 1500-gallon tank and has two pumps set up. One is a 5 hp pump to feed the dyno capable of moving 300 gallons of water per minute, and the second pump is a 2 hp return pump, which runs on a float switch,” he says. “The way our supplier has it set up is you have a tank that gets fed and in that tank is a baffled portion. Once it reaches a certain level the float switch kicks on and pulls the water back to the tank to constantly move water.”

NVR on the other hand, is one of those shops that uses city water. “Water is very important,” Nickerson says. “You need an ample water supply. We have city water and a 5 hp electric motor pumping the water into the dyno. We also use a 500-gallon auxiliary water tank as back up.”

As far as fuel systems are concerned, you want to have the ability to run both EFI and carbureted engines. Ison

Top: Ison Racing Engines used a  perforated metal and Roxul insulation to keep noise down in its dyno. Bottom: NVR Racing Engines used a filled-block wall to keep noise at a minimum.
Top: Ison Racing Engines used a perforated metal and Roxul insulation to keep noise down in its dyno.
Bottom: NVR Racing Engines used a filled-block wall to keep noise at a minimum.

Racing Engines achieved that by talking to Aeromotive.

“Basically the fuel cell we are using is a 5-gallon capacity that is mounted outside the dyno cell and all the fuel is run inside from that,” Hupertz says. “Its one pump with several valves and shut-offs, two different regulators and everything bypasses back to the tank. Any fuel, if you’re running a carbureted version, you regulate the pressure going to the engine, and anything it doesn’t use gets bypassed back to the tank.

“With an EFI model you let it go out at full pressure and you regulate it coming back to the tank because the pressure difference is quite great. One runs at 7 lbs. and one runs at 50 lbs.”

Cost and Choosing a Dyno

As stated earlier, not every shop has a dyno, largely due to the fact that it is a big expense. However, doing a large portion of the work yourself can save you a lot of money.

“The quotes we got were between $45,000 and $70,00 depending on options,” Hupertz says, referring to the dyno cell. “These quotes, however, didn’t include the install. We did it ourselves and material-wise we ended up coming in right around $35,000.”

NVR installed its dyno room years before Ison Racing did its, so the cost difference reflects that a bit. NVR spent roughly $5,000 to build its dyno room. Today, a dyno cell would likely run you $20,000 in the low range, all the way up to $3 million for a top-of-the-line dyno cell.

The dynamometer itself is another expense and decision you’ll need to make. Both Ison and NVR have Super Flow dynos.

“Our particular set up with the options that we had was around $67,000,” Hupertz says. “We purchased a Super Flow 902 S because it has the capability to do everything we wanted to do. The absorption unit has the ability to control an engine with high horsepower and high rpm and something with lower horsepower and low rpm. The absorption unit on a Super Flow is a good design that fit our needs.”

All said and done, Hupertz’s dyno and room cost around $100,000. Part of buying a Super Flow dyno includes three days of onsite training. Once your dyno is up and functional, they give you training to be able to run it correctly.

NVR is on its third dyno. T “With our latest dyno we probably have $60,000 – $70,000 tied up in it,” Nickerson says. “Our Super Flow is rated at 2500 hp.”

With each new dyno NVR has updated the electronics and the computers for repeatability, documentation and tracking of the motor. “Each dyno lasted us an average of 10 years,” he says. “At that point they became out of date and inaccurate. Once you start not being able to repeat the dyno pulls you need to calibrate it, and when it gets to the point when calibration doesn’t hold the readings, you need to replace the dyno.” Fortunately, NVR discovered there is a market for used dynos and has been able to sell its previous ones, usually getting half of that money back.

If you’re in the market for a dyno, keep in mind that you have options, resources and recommendations at your disposal to build the dyno that’s right for your shop and your budget. In the end, the investment will be worth the effort. n

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