Popularity Contest (Dyno Machines)
02-11-2009, 03:17 AM
#16
Three Wheelin'
The dyno software is quite sophisticated and sampling is 1000 per second. A lot of data collection if you want other than the graphs. You really can tune an engine on an inertia dyno by "driving" on the dyno. Accelerate, decelerate, different gears, just like on the road. If I want to explore a certain RPM/load, I put on the dyno brake to hold in that area. The dyno brake is air operated and the pressure can be changed to suit the load needed. I made a throttle stop so I can hold a certain throttle opening to tune part throttle stages too.
02-13-2009, 02:23 AM
#18
Former Sponsor
Leslie/Kevin--
The classic Dynojet, the one with the big roller where acceleration of the known-mass drum, is an inertia dyno. It's meant for full-throttle pulls from off-idle to redline. The horsepower is calculated by how fast you accelerate the drum.
Meanwhile, to do serious on-the-dyno tuning, you'll want a dyno with a brake attached to it. Some have eddy-current brakes, a fancy name for a generator that shunts generated current to a resistive load and allows you to adjust the amount of load applied to the motor at a constant RPM. The idea is that you can tweak and tune the ignition and fuel mapping at a specific engine speed until you get it right, then move on to the next speed and tune there. This is the kind I'd be lloking for to do tuning. If you are just looking for bragging rights, the more common inertia dyno will be fine.
The classic Dynojet, the one with the big roller where acceleration of the known-mass drum, is an inertia dyno. It's meant for full-throttle pulls from off-idle to redline. The horsepower is calculated by how fast you accelerate the drum.
Meanwhile, to do serious on-the-dyno tuning, you'll want a dyno with a brake attached to it. Some have eddy-current brakes, a fancy name for a generator that shunts generated current to a resistive load and allows you to adjust the amount of load applied to the motor at a constant RPM. The idea is that you can tweak and tune the ignition and fuel mapping at a specific engine speed until you get it right, then move on to the next speed and tune there. This is the kind I'd be lloking for to do tuning. If you are just looking for bragging rights, the more common inertia dyno will be fine.
I personally think that the Dyno-Jet results are generally "optimistic". Anytime you test a car and it makes more rear wheel horsepower than the people that built it claim for flywheel horsepower (which is common), you better beware.
02-13-2009, 02:47 AM
#19
Rennlist Member
I dont know how that is possible, unless someonoe is really doing somthing funky with the test. It either accelerates the drum at a whatever rate the graph says it did, or it doesnt. the correction factors are generally less than 1-2%, and is why I always see the actual and SAE printouts and just to make sure nothing is out of wack from the expected outcome of the conditions.
mk
mk
02-13-2009, 05:22 PM
#20
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Mark--
I suspect that the DynoJet (and other) calculations may have some other K factors built in, maybe from the marketing department. It would be hard to sell dynos and dyno services to folks who have big expectations for their cars. Those would be based on brags from engine builders or car manufacturers. Surely you remember the big dump that horsepower numbers took as we rolled into the 1970's. That was to please insurance companies as much as it was to admit that the real ponies weren't always there. You are also aware I'm sure about the rash of charges to Ford over Mustang and other horsepower claims that didn't always match up with what the dynos were saying. Lots of incentives to push the envelope on reporting the ponies just a bit.
The thing that the DynoJets and other inertia dynos bring is consistency between dynos of the same make. Eddy-current dynos offer the builder or dyno operator a chance to push a motor with extra ignition timing to get a brief reading for bragging rights. Get the motor to redline and quickly crank in the loading, and you can generate some pretty wild "flash" readings that are based on inertia of the rotating parts as much as actual power generated. The software faithfully gives a very optomistic peak number though. When you are bragging about numbers that's great, but it's no help for tuning for real performance. Inertia dynos eliminate that option, but then give up the ability to tune at a constatnt and specific load and engine speed.
That's been my own experience.
25 years ago or more, I made a relatively small water-brake dyno with a roller driving a large water pump, a barrel for a reservoir, and a valve in the pump discharge. Tune to the pump discharge pressure. I couldn't tell you how many horsepower we were making from that, but it was extremely simple to see the effects of changes in tuning vs the pressure gauge.
I suspect that the DynoJet (and other) calculations may have some other K factors built in, maybe from the marketing department. It would be hard to sell dynos and dyno services to folks who have big expectations for their cars. Those would be based on brags from engine builders or car manufacturers. Surely you remember the big dump that horsepower numbers took as we rolled into the 1970's. That was to please insurance companies as much as it was to admit that the real ponies weren't always there. You are also aware I'm sure about the rash of charges to Ford over Mustang and other horsepower claims that didn't always match up with what the dynos were saying. Lots of incentives to push the envelope on reporting the ponies just a bit.
The thing that the DynoJets and other inertia dynos bring is consistency between dynos of the same make. Eddy-current dynos offer the builder or dyno operator a chance to push a motor with extra ignition timing to get a brief reading for bragging rights. Get the motor to redline and quickly crank in the loading, and you can generate some pretty wild "flash" readings that are based on inertia of the rotating parts as much as actual power generated. The software faithfully gives a very optomistic peak number though. When you are bragging about numbers that's great, but it's no help for tuning for real performance. Inertia dynos eliminate that option, but then give up the ability to tune at a constatnt and specific load and engine speed.
That's been my own experience.
25 years ago or more, I made a relatively small water-brake dyno with a roller driving a large water pump, a barrel for a reservoir, and a valve in the pump discharge. Tune to the pump discharge pressure. I couldn't tell you how many horsepower we were making from that, but it was extremely simple to see the effects of changes in tuning vs the pressure gauge.
02-13-2009, 05:40 PM
#21
Three Wheelin'
Bob,
Kinda interesting that my dyno has a "Dynojet scale" choice in the chart setup. Checking that box adds about 2 % to the readings.
Kinda interesting that my dyno has a "Dynojet scale" choice in the chart setup. Checking that box adds about 2 % to the readings.
Mark--
I suspect that the DynoJet (and other) calculations may have some other K factors built in, maybe from the marketing department. It would be hard to sell dynos and dyno services to folks who have big expectations for their cars. Those would be based on brags from engine builders or car manufacturers. Surely you remember the big dump that horsepower numbers took as we rolled into the 1970's. That was to please insurance companies as much as it was to admit that the real ponies weren't always there. You are also aware I'm sure about the rash of charges to Ford over Mustang and other horsepower claims that didn't always match up with what the dynos were saying. Lots of incentives to push the envelope on reporting the ponies just a bit.
The thing that the DynoJets and other inertia dynos bring is consistency between dynos of the same make. Eddy-current dynos offer the builder or dyno operator a chance to push a motor with extra ignition timing to get a brief reading for bragging rights. Get the motor to redline and quickly crank in the loading, and you can generate some pretty wild "flash" readings that are based on inertia of the rotating parts as much as actual power generated. The software faithfully gives a very optomistic peak number though. When you are bragging about numbers that's great, but it's no help for tuning for real performance. Inertia dynos eliminate that option, but then give up the ability to tune at a constatnt and specific load and engine speed.
That's been my own experience.
25 years ago or more, I made a relatively small water-brake dyno with a roller driving a large water pump, a barrel for a reservoir, and a valve in the pump discharge. Tune to the pump discharge pressure. I couldn't tell you how many horsepower we were making from that, but it was extremely simple to see the effects of changes in tuning vs the pressure gauge.
I suspect that the DynoJet (and other) calculations may have some other K factors built in, maybe from the marketing department. It would be hard to sell dynos and dyno services to folks who have big expectations for their cars. Those would be based on brags from engine builders or car manufacturers. Surely you remember the big dump that horsepower numbers took as we rolled into the 1970's. That was to please insurance companies as much as it was to admit that the real ponies weren't always there. You are also aware I'm sure about the rash of charges to Ford over Mustang and other horsepower claims that didn't always match up with what the dynos were saying. Lots of incentives to push the envelope on reporting the ponies just a bit.
The thing that the DynoJets and other inertia dynos bring is consistency between dynos of the same make. Eddy-current dynos offer the builder or dyno operator a chance to push a motor with extra ignition timing to get a brief reading for bragging rights. Get the motor to redline and quickly crank in the loading, and you can generate some pretty wild "flash" readings that are based on inertia of the rotating parts as much as actual power generated. The software faithfully gives a very optomistic peak number though. When you are bragging about numbers that's great, but it's no help for tuning for real performance. Inertia dynos eliminate that option, but then give up the ability to tune at a constatnt and specific load and engine speed.
That's been my own experience.
25 years ago or more, I made a relatively small water-brake dyno with a roller driving a large water pump, a barrel for a reservoir, and a valve in the pump discharge. Tune to the pump discharge pressure. I couldn't tell you how many horsepower we were making from that, but it was extremely simple to see the effects of changes in tuning vs the pressure gauge.
02-14-2009, 09:42 AM
#22
Our Porsche club for racing classes uses the factor of 1.32, it is applied to the rear wheels dyno the club uses which is a Dyno Dynamics type dyno, I know the U.S based systems come off 15 to 20% loss depending on the car being auto or manual. Our 1.32 factor at first glance may not seem to be correct, however if you do a few searches for rear wheel numbers done with the DD dyno you will find they tend to read quite a bit lower.
To be accurate of course the dyno needs to be calibrated to manufacturers specs. Below an interesting read, to give you a comparison my car does around 305 rwhp and a best number of 311 rwhp on the DD.
From a Merc forum E55s
http://mbworld.org/forums/w211-amg/2...-dynamics.html
The from a Subie forum, it is an extract as it looks like a long thread.
"When I was just a turbo-back Evo with cam gears, I made 301whp at Alamo in Dallas (Dynojet). They said that stock Evo VIIIs baselined around 235whp. At Dyno4mance's Dyno Dynamics just a few days later, I made 265whp, where stock (03) Evos baseline around 205-210whp. KTR's dyno seems to agree: http://www.ktrperformance.com/dyno_tuning/dyno_graph_car.php?id_num=68"
This is another extract, from a BMW forum. A number of Dynojet graphs had been posted previously and as such, well just read below.
"Originally Posted by cstang68
So I'm almost ebarrassed to post my graph, but I will when I get it. 204whp 188tq. 3rd gear pulls, dyno dynamics dyno unit. I was really bummed until an 03 turbo porsche put down 300whp, and a stock 04 gti put down 138whp.
you should be pretty happy with that, dyno dynamics always read a lot lower than dynojet, you could add around 12% to that to be similar to reading you would get on dynojet
dyno dynamics are also limited to 200kph, which is why our euro's are run in 3rd gear, 4th goes over 200kph "
Here's a couple of links to Porsche Caymen forums, they are around 243 rwhp
http://www.caymanclub.net/987-dyno-c...e-exhaust.html
http://www.caymanclub.net/987-dyno-c...mics-dyno.html
The ford Falcon GTs we have here are rated at 290 kw and I have seen many of these dynoed and they are always in the 215 to 225 range at the wheels.
Anyway I think we just use these dynos as tuning tools and indicative performance.
So I think we all know you can't go from dyno to dyno to compare our cars, you need to have a consistent testing format. BTW In the Shootout mode on the DD the operator can not play with various factors of calibration, it is set by the machine, a way of trying to stop fudging.
Greg
To be accurate of course the dyno needs to be calibrated to manufacturers specs. Below an interesting read, to give you a comparison my car does around 305 rwhp and a best number of 311 rwhp on the DD.
From a Merc forum E55s
http://mbworld.org/forums/w211-amg/2...-dynamics.html
The from a Subie forum, it is an extract as it looks like a long thread.
"When I was just a turbo-back Evo with cam gears, I made 301whp at Alamo in Dallas (Dynojet). They said that stock Evo VIIIs baselined around 235whp. At Dyno4mance's Dyno Dynamics just a few days later, I made 265whp, where stock (03) Evos baseline around 205-210whp. KTR's dyno seems to agree: http://www.ktrperformance.com/dyno_tuning/dyno_graph_car.php?id_num=68"
This is another extract, from a BMW forum. A number of Dynojet graphs had been posted previously and as such, well just read below.
"Originally Posted by cstang68
So I'm almost ebarrassed to post my graph, but I will when I get it. 204whp 188tq. 3rd gear pulls, dyno dynamics dyno unit. I was really bummed until an 03 turbo porsche put down 300whp, and a stock 04 gti put down 138whp.
you should be pretty happy with that, dyno dynamics always read a lot lower than dynojet, you could add around 12% to that to be similar to reading you would get on dynojet
dyno dynamics are also limited to 200kph, which is why our euro's are run in 3rd gear, 4th goes over 200kph "
Here's a couple of links to Porsche Caymen forums, they are around 243 rwhp
http://www.caymanclub.net/987-dyno-c...e-exhaust.html
http://www.caymanclub.net/987-dyno-c...mics-dyno.html
The ford Falcon GTs we have here are rated at 290 kw and I have seen many of these dynoed and they are always in the 215 to 225 range at the wheels.
Anyway I think we just use these dynos as tuning tools and indicative performance.
So I think we all know you can't go from dyno to dyno to compare our cars, you need to have a consistent testing format. BTW In the Shootout mode on the DD the operator can not play with various factors of calibration, it is set by the machine, a way of trying to stop fudging.
Greg
