Dyno differences??

[JLEONARD]

And the DD dyno setup it ran on can be set for higher loads which is how he was able to run the

CB brings up a good point here from another thread.....



So guys, who really understands how the dynos are different, how the numbers will vary, etc?

I ask because I am planning on doing a dyno run in the near future. Last time I went was on a Dynojet with the local NE group.

But that's a 2 1/2 drive for me.

Now that Janetty has his up and running, I'm considering going there because it's 10 minutes away...

But he says his is different ... here's his quote to me:



Our Numbers will the most accurate available, we do have a Dyno Jet Correction factor in our software to show you what you would get on a Dyno Jet.

Our Dyno also simulates the exact load the truck sees on the road, A DJ can only simulate a 5000 lb. load for a short burst.

Any Time you do performance modification you should always use the same Dyno Before and after your changes.



So what will this mean to me? How are the hp and torque numbers likely to vary?



Please help educate me. I work with test equipment every day so I understand equipment differences... but usually they are calibrated to some standard.

Thanks.

Jay

 

[Grey Wolf]

I guess I'm from the old school, I liked the old water brake style. You can load the engine and get the boost up, I'm not sure but I think a lot of Dyno's around today are the inertia type, which is large roller (load) like you speak of.

 

[sparks57]

The big thing about that is not necissarily that it is skewing the numbers, so much as that it allowed him to run a huge turbo so he didn't melt the pistons.



But yes, you should always stick to the same dyno, and try to always run during similair atmospheric conditions.



I have seen over 50hp in difference between dynos before. (not on my rig, but on other's... I've never been on a dyno).

 

[KLockliear]

The nice thing with inertia dynos is the operator can't change the load, so you always get a consistent measure on the stick.

 

[Greenleaf]

I know nothing about dynos. We ran a water dyno in college with a big cam 855 and Detroit 8V 92. This thing will turn the turbo housing red. Yah baby. You could hear these engines from all across the campus grounds when we loaded them down



Greenleaf

 

[MMiller]

I went to John Deere Ag tech school, spent time at the shop dyno'ing tractors. I now work for a Cat dealer, that regualrly dynos semis on chassis dyno, and engines on a flywheel dyno.



With that being said, the way we dyno diesels is FAR different then how the trucks are dynoed that I see on videos off this website and various others. Whether it is a tractor on a PTO dyno, semi on the chassis dyno, or engine on the flywheel dyno the theory is the same. The engine is wound up to near governed limit and then slowed at increments until peak torque is reached, sometimes as low a 1200 rpms. I believe this is a very consistent way of dynoing a diesel, full fuel, full boost, real world like a tractor running in a field, semi hauling down the interstate.



This being said, most of the trucks here would not live on one of these dynos without pyro readings melting manifolds off of engines. I have never had mine on the dyno yet, some day though. Not really worried about what its putting down, it pulls plenty fine for me!



I have seen many people comment that their CTD's don't hit full boost on the dynos some run on. This tells me that the full HP/Torque reading has not been measured yet. The dynos that are used by the masses here are more geared for gas type engines, does anybody else here agree??



Sorry for the long post, I look at things a little differently because of what I see on a daily basis around the shop, and how I have been brought up around diesels. I also look more a the torque that is put down, as hp is a number from a mathmatical equation from torque and RPM. Anybody can put down good hp numbers, if they want to let the engine rev, and set it up to keep pulling in high rpms. Its just how many rev do you want.



Let me know guys if I am off base here, or educate me a little more. I aplojize if this is a little off base, but I think(unyet proven) that with a truck that can run with out high pyro readings will have better torque readings on a dyno like the one I am around then on one that the truck accelerates struggles to build boost then the run is over. This in turn I think would produce better hp numbers because your torque would be up?



Has anybody run their truck on a semi chassis dyno yet? Or is this my homework? Really wouldn't be a true test because I have no dyno numbers on any other dyno



Sorry for the rambling, hope not everybody skips this post.



Michael

 

[JLEONARD]

Sorry for the rambling, hope not everybody skips this post.

Don't apologize... . I thought it was a good post. That's the kind of discussion I was hoping to get out of this thread.

You bring up some issues that are starting to shed some light on the subject... I think.



Jay

 

[Grey Wolf]

Michael,



Well written. That's why I prefer the old water brake style.

 

[bflood]

First, MMiller (Michael) I liked the thought process in your post. No apologies needed.



A 5000# load does not seem like enough to develop full torque. If that weight simulates towed weight, you can only develop torque during the acceleration. To our trucks, this dyno sounds like the "height of optimism" . . . like a flea climbing up an elephant's tail with the intention of . . . . (well you know) . . . .



This 5000# sounds about what I experience accelerating up a very steep hill running empty. I barely reach full boost and it doesn't seem that I'm really loading the Cummins.



I've had my JD "A" tractor on a water brake dyno. Although its tricky to operate consistently, and is more time consuming, it has the capability to read any test conditions (RPM versus different loads). The key is to find the right load to match to the particular engine under test. I'm making it sound complicated perhaps but I imagine it would be simple to an experienced dyno operator.



I'm no expert, does this make sense?



Bruce



PS: I've never dyno'd my CTD

 

[JLEONARD]

TTT

So... .

A DynoJet has low nominal resistance and computes hp based on how fast you accelerate that resistance?? That would mean gear ratio, tire size, what gear you're in, std vs auto, etc. make a big difference??

That would mean the numbers are only relative to the specific vehicle and cannot necessarily be compared to another unless all those things are equal??



A Superflow (like Janetty has) or one like Michael described actually loads the vehicle as much as it can take and calculates the hp/torque from actual power that the vehicle can sustain with that load (resistance)??

That would mean a more accurate vehicle to vehicle comparison???



Or to take a stab a bit further.....

A Dynojet may indicate 1/4 mile ability, whereas a Superflow may indicate load hauling ability????



Bear with me guys, I'm an engineer and I ask a lot of questions...

Jay

 

[bflood]

#*@$**! Engineers. What do they know?

 

[JLEONARD]

Bruce,

You can ALWAYS tell an engineer... . trouble is you can't tell them much!!

 

[MMiller]

I don't know about janetty's dyno, but I believe the one we use is a superflow. It has 4 drums in the floor to dyno semi's. And it will bring a 600 hp Cat C16 running about 1900 ft lbs of torque to its knees. The test is all computer controlled and brings the engine rpms right down to 1100 1200 rpms. Very easy to do if the truck is running right. The above is why I say most of the trucks here would melt down due to EGT's, because the dyno I witness is relentless. Also the dyno operator has to put in rear gear ratio, the truck is run in a trans gear that is 1:1 ratio. Tire size and gear ratio do change HP. My buddy at the shop says I should find some stock tires to get a real hp reading, but I say it runs on 33's all the time, thats how I'm gonna dyno it.



You oughta hear a 600 horse cat breathing through tall 8" bull hauler stacks! That cat talks REAL LOUD, and doesn't give up easliy!!



I agree with your thinking though Jay, I think we are on the same path, HOWEVER, I am a mechanic and I really need to talk to an engineer sometimes!! Not ususally good stuff either!



Michael