Competition which dyno has the true readings.

[Turbo Thom]

Just my opinion, but I don't think any dyno will give you real time numbers. I think David and his Dyno Jet is problably one of the best in the country. Even on his, the numbers, and what's run on the strip, will vary. There are just to many variables in a stationary position and runnin 100 mph down the strip. The numbers will be close, but the racing numbers will be higher.



Maybe what I'm looking at is 770 on the dyno runs a 10. 30 on the strip. Calculate that out to weight and it sure ain't 770. That's why I would like to see these 870 HP truck make some passes down the strip. They may even surpass 950, if they made it at all. Moving a 5500 truck from 0 to 60, takes unreal luck to not break something just from the shear stress. Earl broke his pinion shaft at Houston, and his is 5500. A lot of stress. Still, it would be nice to see these dyno truck on the strip and just see what they woud make.



. . Preston. .

 

[JVolpe]

I do agree that dyno numbers are very subjective and not what I use the dyno for. It is just a baseline to help me with starting combinations at the track. I have dyno'd 7 times this year I think. I have over 150 1/4 mile and 1/8 mile drag strip time slips in my envolope for this year. Made 17 passes Saturday using different settings and launch boost. The number that means the most to me is last 1/4 mile ET and I only know one accurate way to get that one.

 

[Hohn]

well i might get grilled for this but i think hes right

Greg isn't just right, he's EXACTLY right.

Dynos are good diagnostic tools. But a typical DJ or Mustang is pretty limited.

Now, Keith L knows Dynojets pretty well. Gee, I wonder why

But even he will admit that a DJ will require multiple runs to show how the engine's performance will vary from gear to gear.

Moreover, a DJ would require changing the drums out to vary the load.


Imagine you are dynoing a 6-speed truck on a DJ248C. Do you think you'll get the same hp curves in all 6 gears? Of course not!

How about an auto transmission truck-- you think it will be the same with the converter locked as with it unlocked??



Now a chassis dyno is far superior to an engine dyno for testing the whole package, because it allows you to see the effects of gearing, tire size (and rotational inertia), transmission loss, etc.

But you SHOULD have a chassis dyno that has the engine dyno capabilities that COMP mentioned-- the ability to hold the engine at a constant RPM, or vary the rate of rev gain. We don't have practical CVTs yet, so engines MUST vary RPM to account for gearing limitations.

In the end, each dyno is "ideal" but only for certain purposes.

If you want to test ONLY how fast your truck accelerates in top gear, then a DynoJET cannot be beaten. For passing power on the hwy, you can best optimize your tuning using a DJ inertial dyno.

However, if you want to test how well your truck will be able to maintain speed pulling a heavy load up a grade, then a MUSTANG dyno is best. It simulates the increasing load the engine will see as the truck enters and climbs a grade.

Each of the above is limited to really optimizing just ONE GEAR.


If you are building a race package with a vehicle that actually has to use more than one gear in the course of a race, then you MUST have a more sophisticated dyno that can control the rate of RPM gain or loss by varying the load across a wide spectrum.

That, to me, means one of the more sophisticated SuperFlow dynos, or a Dyno Dynamics dyno.


Parting shot: why can't they the build an intertial dyno that had heavy weighting on the end of thr drums in a special apparatus? I'm imagining a setup that slides the weights in or out towards the center of the drum or towards the outermost edge, and thereby varies the intertia of the drum across a wide range??

With this type of setup, you could have the precision of an intertial dyno along with the ability to vary the inertia of the rollers on the fly

jh

 

[Hohn]

The number that means the most to me is last 1/4 mile ET and I only know one accurate way to get that one.

Namely, running at the track, right?

 

[JVolpe]

Namely, running at the track, right?

Yes Sir, that's right.

 

[COMP461]

If you only look at ¼ mile times and mph then they are loosing a big opportunity to run fast. First you must have a data logger , with out it you are just guessing !!!!!!



You must look at ever incremental of the track and the splits between them. Everyone is just as important , and every part of the track has a profound effect on the total et. If you chance something that gains you . 08 in the back half , of second 1/8 mile and loses you . 06 on the first half you only know you went faster , but you leave on the table the ability to put the two parts together. The 60 foot times are a factor of chassis , gear , track and leave configurations like base in your clutch or leave rpm in a converter. The 60 to 330 are a reflection of you first gear splits and power is starting to make a play, tune of the motor for that gear is important. 330 to 1/8 is all about power , and is the biggest tell tail of converter selection or clutch lock up. The 1/8 to the 1000 is just plain hp and you laying on the clutch or converter and almost minimal motor acceleration the drive line is catching the motor in a converter car , and the clutch is tugging at the motor in a stick car. 1000 to 1320 is grinding metal , nothing more , the gains are less , and the motor is making power to gain a few more mph , but most of all its just trying to stay in one piece. ¼ mph is a good representation of total hp. But the mph at the 1000 would if you had traps .



To tune for each part of the track you must dyno for each part of the track. And you make the tune fit .



Data Loggers , I have used them al Race Pack , AutoMeter, and now the RPM by the same guy that did the AutoMeter. If you don’t invest in one your lost . the RPM will hold 10 to 20 runs stored inside , and is the most easily set up. The goal of the RPM computer was to make it simple so that the average racer could use it.



http://www.rpmperf.com/

 

[JVolpe]

Thanks for the information.



I understand that there are tools that would certainly make it easier to tune everything to an optimal level for my particular truck and application(1/4 mile racing). Unfortunately I only have the desire and not necessarily the means to do things the correct way. For now all I have is the simple baseline HP numbers from a dyno, a few gauges, SOTP meter, 1/4 mile time slips and a whole lot of trial and ERROR.



If someone would like to help sponsor or provide the tools I would be very happy to use them. Until then I have to wait for the money tree to grow.

 

[Dl5treez]

I agree 100%. I use the superflow dyno where I work(Cat dealer). To get an accurate HP reading on any diesel, you need to lug it down, not rev it up. When your accelerating, the engine is constantly trying to "catch up". It's also very difficult to get good down low power on a dyno meant for a gasser.

Someone else in the know---scary...

 

[KLockliear]

Now, Keith L knows Dynojets pretty well. Gee, I wonder why



But even he will admit that a DJ will require multiple runs to show how the engine's performance will vary from gear to gear.



Imagine you are dynoing a 6-speed truck on a DJ248C. Do you think you'll get the same hp curves in all 6 gears? Of course not!



How about an auto transmission truck-- you think it will be the same with the converter locked as with it unlocked??



jh

I can see the direction this thread is going. LOL.



Actually though, you can do an "all-gear" run through the gears in one dyno test and overlay the individual gears over each other by RPM if you wish.



The HP is not the same in every gear, as you said. This is because with the mechanical advantage, you use more HP to accelerate the drivetrain in 1st (because you're spinning it up faster), than in 5th. Obviously, with a turbocharged engine, you need boost to make the power, and you won't have that on the dyno (or on the street) in that gear - at least not like you would in a higher gear.



The converter lockup vs. non-lockup will also show the deficiency of the converter to put the full power to the ground while not in lockup. The chassis dyno shows what gets to the ground, not what the engine produces - they make engine dynos for that.

 

[mhuggler]

Don't forget about tire slippage. Wheel torque really starts to go through the roof when you start gearing much lower than direct.

 

[DavidTD]

These threads are always fun and I agree with Keith on which direction it will go.



To answer the original question of which dyno has the true reading? Nobody really knows do they?



YOUR real number will be the one you want to believe, which is going to be the highest number a dyno will give you.



If loading is the only way you can tell real power then answer these questions for me.



1) does any dyno take into account Coefficient of drag? If so what is it for your truck and what is it after you have added a brush guard, big tires and fender flairs?



2) Is the load the same on a truck in 1st as it is in 4th gear? If not, which dyno accounts for that or do any?



3) If a dyno has to create a load, how does it know what the proper amount is for the tested vehicle? Who enters the data and who validated the data as being accurate? The Dyno company? DOT?



4) If 1/4 numbers are the true test of power, then who's calculators are correct? How do they deal with CD, not knowing the power curve of the engine, not knowing weather conditions etc. ? In other words how can there be one formula that works for everyone or every car without adding more data than weight and mph.



5) If my 5000lb truck makes 500hp and I put it on a diet to 4000lbs, I have less load on the engine. Did I lose HP too?



My point here is it is all data. You will not find proof that one dyno is more accurate over the other, you will not find proof that one formula is more accurate then the other. What you will find is opinion on all of it.

 

[Hohn]

Good Post, David. You hit the nail on the head.

So did Keith.

The problem is that people try to take dyno DATA and extrapolate that to mean things that it doesn't.

The flaw isn't the dyno so much as what we do with the dyno results. A dyno is only as useful as the person's wisdom in applying the data towards productive tuning.

jmo

 

[KLockliear]

The problem is that people try to take dyno DATA and extrapolate that to mean things that it doesn't.



The flaw isn't the dyno so much as what we do with the dyno results. A dyno is only as useful as the person's wisdom in applying the data towards productive tuning.

jmo

Those are the most true statements I've seen on here in a long time. I agree completely!

 

[Dl5treez]

If loading is the only way you can tell real power then answer these questions for me.

OK I'll try, just for fun.

1) does any dyno take into account Coefficient of drag? If so what is it for your truck and what is it after you have added a brush guard, big tires and fender flairs?

Horsepower and torque at the flywheel or to the ground aren't affected by brush guard, fender flare, or big tire drag. Big tires do affect the actual gear ratio to the ground so they do affect power to the ground. Now I guess if someone could build a combination wind tunnel/chassis dyno you could figure in all of it. Be fun to watch that puppy run. :-laf

2) Is the load the same on a truck in 1st as it is in 4th gear? If not, which dyno accounts for that or do any?

Not entirely as the gear ratios will enhance an engine's ability to handle the load. A dyno with variable load settings can account for that if required.

3) If a dyno has to create a load, how does it know what the proper amount is for the tested vehicle? Who enters the data and who validated the data as being accurate? The Dyno company? DOT?

From the info I have from "dyno school" LOL the manufacturer builds the dyno with a given amount of 'power' to create the load. If a dyno can hold the vehicle or engine being tested at it's peak torque RPM at 100% throttle, then the dyno has loaded the vehicle or engine to 100% capacity. If the engine/vehicle is loaded any further it will quickly lose power and die. Quickly means very quickly, like a couple seconds quickly. If the dyno cannot hold the vehicle/engine at a set RPM at 100% throttle, then the dyno is not big enough to handle the vehicle/engine being tested. If the tires are slipping that's another matter entirely, and goes back to what I said earlier about proper vehicle restraining.

4) If 1/4 numbers are the true test of power, then who's calculators are correct? How do they deal with CD, not knowing the power curve of the engine, not knowing weather conditions etc. ? In other words how can there be one formula that works for everyone or every car without adding more data than weight and mph.

1/4 miles times are a true test of a vehicle's power, traction, driver ability, many things. Big power doesn't mean a low E. T. or high trap speed, there is WAY more tuning needed to get that.

5) If my 5000lb truck makes 500hp and I put it on a diet to 4000lbs, I have less load on the engine. Did I lose HP too?

Nope, but if you can keep it hooked up you'll go faster.

My point here is it is all data. You will not find proof that one dyno is more accurate over the other, you will not find proof that one formula is more accurate then the other. What you will find is opinion on all of it.

Some dyno's have more capability to deliver more data.





All my humble, no-mind, no expert, no god opinions. Have a nice day!

 

[mhuggler]

We're not worthy! We're not worthy! :-laf I couldn't have explained it any better. Are we done here? I gotta take a crap!

 

[Evil Otto]

hey guys thanks for all the info. has any used a dyno jet Model 224xLC?



ED

 

[Dl5treez]

hey guys thanks for all the info. has any used a dyno jet Model 224xLC?

I haven't, sorry.....