Competition Dyno Talk

[DavidTD]

I agree.



Please gentlemen I can see that this thread is a prime candidate for a big padlock.



This discussion is very interesting and I would like to get back to the technicalities of why my HP # and ET/MPH do not match...



David,



Did you get around to downloading my dyno sheets???



Justin

Justin, I just downloaded. I got the twins graph and only one. But it is ok, not sure I can tell you much by it anyway. But the weight was listed at 6800 on this one. We need to know if that makes a difference.

 

[justinp20012500]

No Justin, I have not been into the office where I have high speed. Here in the sticks, I can't get it yet.



But one thing I did notice, is that on your dyno sheet waaaay back on page 1 it list your truck as 6600lbs. If I calculate your hp based on 6600 lbs, it comes out to 409, closer to the 384 you made. You'd have to ask the dyno operator how much that weight will change the output (if at all) as I don't know.



But I would be willing to bet with timing box, fueling box, DDIII's and hybrid turbo your truck was making more than 384hp, on my dyno anyway. Maybe some others will chime in with their opinion on what they have made with similar set-ups.

Thanks for the reply David,



I too noticed that and thought it might have something to do with the different numbers. I am going to be at the shop I dynoed at tomorrow and will ask them the same question.



FWIW,



I dynoed on Gillett's dyno and the sheet had the vehicle listed as weighing 7500 LBS. It made 350. 4 RWHP. I then dynoed at Edge Products and their dyno sheet said 7200 LBS. It made 349. 8 RWHP.



At that time they both have the M1750.

 

[DavidTD]

Thanks for the reply David,



I too noticed that and thought it might have something to do with the different numbers. I am going to be at the shop I dynoed at tomorrow and will ask them the same question.



FWIW,



I dynoed on Gillett's dyno and the sheet had the vehicle listed as weighing 7500 LBS. It made 350. 4 RWHP. I then dynoed at Edge Products and their dyno sheet said 7200 LBS. It made 349. 8 RWHP.



At that time they both have the M1750.

That comment tells me it may not make a difference. But I truly don't know. But I will tell you this, if you can run 97 mph with 350hp, we gotta talk. :-laf

 

[DavidTD]

This thead is very exciting, big fancy words, aerospace tech,

I don't know how we have managed all this time!

NASCAR seems to think a lot of dynojet's product.

I personally like the tool because it gives a real world test

of how a truck will respond on the street. If your truck won't

come to life on david's dyno you will have a black smoking

pig on the street. A load will hide that problem,and show more

power. I think in the diesel world, the dynojet is the only way to

go, because pulling these engines down with no air flow is hard

on parts. Thats my 9th grade drop out,grease monkey opinion!

Sorry Jeff. Been meaning to tell you that our readings are way off. Most of those 600-700 runs have had 1. 75 correction, we only made like 10 psi boost, and in reality probably like 175-200 hp. I'm just trying to figure out how you ran that 9 second pass with 175 hp. But don't you worry. I'll get it figured out no matter what math I have to use. Just have faith. :-laf



<David in the thinking room>

Lets see, 1hp = 1 horse without shoes, then add the weight of the shoes and the rotating mass increases so we have only . 78hp, multiply that by the sum of the total weight of horse poop which decreases the weight of the horse so our mass decreases... wait, I'm starting to sound like Fletcher. :-laf

 

[J.Davy]

Brian you hit the nail on the head ,yes all engines are depenandant on fuel,and lets talk this through slowly and civil. Diesels are fuel throttled and have a limit to fuel flow,How would you rate the amont of fuel it burns?,pounds per hour?- liters per hour ?-per minute ?,whatever ,you decide?This fuel is going to prouduce a certain amount of btu's of heat when mixed and burned with air?I hope I am correct so far?If the fuel system is maxed out and not defueling in any way ,for any reason ,it is going to take a certain amount of air to burn all that fuel,or hit the stoichiometric of the fuel. Right?Now this is my question to you -as you go up in elevation does fuel delivery slow down?If not, when you give it more air to make up for the loss due to elevation and burn all that fuel what happens to all those missing btu,s that you claim are not there anymore and have to add this huge correction factor?Please keep it cool I am just trying to work through this with you. I would call you like you asked but I will wait untill you cool down a bit as well as I think there are probably a few guys that find this info interesting.

 

[J.Davy]

I appologize to any of you who have the patience to read through these long posts but I find it hard to explain it in one sentence. Basically what I am am saying is you can't recorrect for missing air after you have added it back in,does this make sense?

 

[justinp20012500]

David,



I talked to the dyno operator over at Gillett Diesel. He says they do not use correction factors at all.



"Gillett has never ran a correction factor and does not plan on running it. Sure you could throw in a 15-16% correction factor to have numbers closer to sea level but those wouldn't be accurate for what you are doing on the road in SLC. "



Maybe that explains alittle... Not sure though. I am not that familiar with dynos, other than one is a "load" and one is an "inertia. "





Justin

 

[KLockliear]

For what it's worth, the moment of inertia for our 1200hp dyno is 61. 6 ftlb^2. That figure includes both the mass of the rollers AND the mass of the eddy current power absorber.

----------------------------

Brian?? I am also curious about your dyno... when you run most trucks/cars. . in a group event. . do you have the dyno set as Interia only??

Nope. There is no such setting on our dynos. If you do not turn the load on, the engine will rev as freely as if the vehicle was up on jack stands.

WOW, I certainly don't want in on this discussion, but looking at the statement above, it just doesn't add up to me. So, the dyno has an inertia of 61. 6 ftlb^2, but without the absorber doing it's thing, the dyno would spin up like the tires were on jack stands? As in there is no inertia to work against?

 

[gtspowerstroke]

Well I've been running a dynojet for aobut 7-8 years on motorcycles for my work and for about 2 years on diesels but not on an every day basis. I have run my diesel on a mustang load dyno as well. On a dynojet you strap it down and make a run. There are NO variables to enter into the computer. If you want torque hook up a tach and you will get a torque reading as torque is a factor of hp and rpm. Hooking up the tach is the most accurate way to get torque as with dynos that try to get it through the drive train can be off especially if it isn't set up just perfect. The load dynos that I have seen, mainly mustang, have several other variables that you have to enter in wich will change the results of the dyno run. what does vehicle weight have to do with a dyno run? You are NOT pushing the vehicle so the weight is NOT a factor in a dyno run. This just gives more room for inaccuracys. The few times I have been to BD for their dyno days the dyno is VERY inconsistant and can't seem to hold any more than 500hp with out the tires spinning. One time you go there everyone is complaining that the dyno is reading 20-30hp lower than the time before. Then the next time everyone is happy that it is makeing 30-40hp more than the time before. The dynojet I run on is alway very consistant. If you want accurate hp/tq number the dynojet is the way to go. The dynojet I run on has heavier rollers than most. It is one of only two dynojets sold from what I've been told that have these heavier rollers. The twin turboed Red Rocket owned by HOSS was on this dyno awhile back and he said he was able to get his turbos up and spooling just fine when a few weeks before up at PDR he couldn't get them to spool for crap. I don't know what kind of dyno PDR has but haven't heard very consistant numbers from it either. I think load bearing dynos are very good for driveability/runability diognostics but NOT for consistant hp/tq numbers between trucks.



I agree that altitude has an impact on our turbo diesels. However it is NOT to the extent of the SAE correction factor. The correction facotrs are WAY off for our application and I think a huge reason for the huge variance between similar set up trucks in different areas. I alway dyno my truck uncorrected as it is what it is putting to the ground here in WA and an accurate representation of what it actually makes.

 

[Turbo Thom]

GTS PS... . The weight factor is for calculating the 1/4 mile run. When David gets the HP numbers, has the weight of the vehicle, then the speed can be figured in the quarter mile. The same with ET. There are sites that have the calculations for that. I think one is www.smokemup.com.



. . Preston. .

 

[jetenginedoctor]

I think I know another way to explain this to you that will make more sense. It is comparitively EASY to make fuel flow at the rate we need it to. You could flow fire-hose flow rates to these engines if you wanted to, but the engine couldn't make use of all that fuel. Long before it stop being able to flow enough air to BURN the fuel, it'll stop flowing enough air to keep the hot parts of the engine from melting down. It's the exact same thing in gas turbine engines. There's plenty of 02 unburned in turbine engine exhaust, which is how afterburners work. By adding fuel to this unburned air and lighting it off within an extended exhaust nozzle, we're able to augment power at huge expense in fuel consumption.



Anyway, getting back on track, increasing fuel flow is easy. Increasing airflow, is not easy. Bolting on a fuel system and building a pump capable of flowing enough fuel to make 1000hp in these engines is something that a good pump shop can do with relative ease. However, building an engine, induction system, turbos, etc that flow enough air to support not only burning 1000hp worth of fuel, but keeping combustion temperatures down to a safe level is pretty tough. When you get it all worked out and have an engine tuned to make MAX HP at the ragged edge of safe EGTs, and take it to a higher elevation, one of two things is going to happen. You're going to over-temp the engine and burn something up when you're unable to flow enough air MASS to control firing temperatures, or you'll wise up before you see the EGTs swing into the cubic $$$$$ zone on the pyrometer, and realize you JUST CAN'T MAKE THE SAME HP WITHOUT THE SAME AIR DENSITY.

Brian you hit the nail on the head ,yes all engines are depenandant on fuel,and lets talk this through slowly and civil. Diesels are fuel throttled and have a limit to fuel flow,How would you rate the amont of fuel it burns?,pounds per hour?- liters per hour ?-per minute ?,whatever ,you decide?

It's easiest if you measure the both fuel and air in lbs/hr. Mass does not change with altitude, density, or gravity, so you eliminate the confusion of a variable quality such as pressure, volume, etc.

This fuel is going to prouduce a certain amount of btu's of heat when mixed and burned with air?I hope I am correct so far?

Yes. The amount of BTUs that go into an engine divided by the work/power produced by the engine is called "heat rate. " This is a standard similar to BSFC, but is measured in BTUs/kW, etc.

If the fuel system is maxed out and not defueling in any way ,for any reason ,it is going to take a certain amount of air to burn all that fuel,or hit the stoichiometric of the fuel. Right?

Again, let's call fuel delivery what it is. . . . a virtually unlimited variable. It's much easier to bolt on a fuel system that'll run away from an engine's ability to flow enough air to safely burn it. This being the easy part of it all, and not a variable in this discussion (at least with a mechanical fuel system a-la P7100. )

Now this is my question to you -as you go up in elevation does fuel delivery slow down?If not, when you give it more air to make up for the loss due to elevation and burn all that fuel what happens to all those missing btu,s that you claim are not there anymore and have to add this huge correction factor?

That's just it. . . . it's WAY easier to turn up fuel than it is air. The ability of the fuel system to deliver the desired mass of fuel isn't hindered appreciably by a change in altitude, but the engine and turbo's ability to flow the same mass of air, IS! If that mass of air isn't there, putting more BTUs in doesn't make more power, it just makes the metal parts of the engine THAT MUCH HOTTER!. Power comes from the expansion of burning air and fuel during the combustion event. If less air is present in the combustion chamber at the point of combustion at any given engine RPM, cylinder pressure will be lower, thus TQ and HP will be lower. The same amount of heat (BTUs) applied to the engine at that temp will be expanding a markedly LOWER mass of air, converting less heat energy into mechanical energy and putting MORE heat into the metal parts of the engine, notably the turbine nozzle and wheel in the turbo, the first things to get messed up when you over-temp these engines.

Please keep it cool I am just trying to work through this with you. I would call you like you asked but I will wait untill you cool down a bit as well as I think there are probably a few guys that find this info interesting.

You try to keep YOUR cool, Mr. Comeback. I've explained this to high school students who had an easier time of understanding this than you seem to. It's extremely frustrating getting this through some people's heads. I'm not some ding-dong who read something in a magazine and decided to post about it on the internet. I've dealt with ALL the stuff I'm telling you about my entire adult working life. If you don't believe me now, you'll never believe me, so this is the last time I'm posting on this thread. You've worn me out, I give up, and I don't care if you believe me or not. I've been paid a hell of a lot of money over the years for knowing the stuff I'm taking my time to try to explain to you, my tax returns, diplomas, training certificates, and wall of books (not magazines, not catalogs) just behind me are my "proof of participation. " I can't stop you from questioning my reasoning or knowlege of the topic being discussed, but I can stop giving a damn about helping you understand.



Good luck.



BTW, I decided that since I had to pay for a copy of the SAE paper that discusses the effect of altitude on turbo diesel engines, I'm not going to share it for free with unappreciative onlookers. If you want to read it, go to the SAE website and buy it yourself. It's number 961826. Have fun.

 

[Sled Puller]

I'm not some ding-dong .....

.

THAT can be argued.



Nice speech, its cool to see you finally comprehend what we do with these engines, it took you longer than most, but considering your background, I understand you are not used to thinking on your own.

 

[KLockliear]

I don't get it. How can it have "the moment of inertia for our 1200hp dyno is 61. 6 ftlb^2. That figure includes both the mass of the rollers AND the mass of the eddy current power absorber" but "If you do not turn the load on, the engine will rev as freely as if the vehicle was up on jack stands. "? Does the inertia go away when the retarder isn't on?

 

[DavidTD]

David,



I talked to the dyno operator over at Gillett Diesel. He says they do not use correction factors at all.



"Gillett has never ran a correction factor and does not plan on running it. Sure you could throw in a 15-16% correction factor to have numbers closer to sea level but those wouldn't be accurate for what you are doing on the road in SLC. "



Maybe that explains alittle... Not sure though. I am not that familiar with dynos, other than one is a "load" and one is an "inertia. "





Justin

Justin, that might explain the lower number, but that still has me scratching my head as to how you can run that fast with only 350hp on the track. This one is gonna make me crazy... :-laf

 

[J.Davy]

I think the reason you don't want produce the paper is simple, it is going to state one simple fact and that is that altitude effects turbocharged diesels differently than naturaly aspirated gas engines. Therfore you can not apply S. A. E correction for naturally aspirarted gasoline engines to turbo charged diesel engines. Man This is getting old. Is any of this sinking in?Call Mark at T. S. T. he can tell you how much turbocharged engines are effected by atmospheric conditions.

 

[Sled Puller]

... . so this is the last time I'm posting on this thread. .

???????????

 

[J.Davy]

Its little ankle humping kids like you that make it hard for these guys to see the truth. Do a little more reading and a little less typing and we will all benefit. If anybody wants to know what type of correction factor the big boys use call Shied Diesel,I asked them yesterday and they said they have a mustang dyno and use the industry standard and turn the correction factor stuff right off . T. S. T. performance also has a mustang dyno and uses less then 1% correction factor year round . As for you Doc,stay off your daddy's computer,go to bed,it's night night time. Have a good sleep.

 

[Winspeed]

Does anyone have the Cliff's Notes to this POST?

I have recently seen many topics that discuss dyno testing included as part of the discussion. While everyone has opinions on where, who, what kind of dyno to use or is best, what bothers me is the misinformation being discussed. What I hope to do is clear up some of this misinformation with observations I have personally seen.



1st – The Peak HP and TQ numbers you receive are just that. Numbers. They don’t tell the whole story. Whether corrected or not, the numbers don’t represent how well the truck performs across the entire RPM band. Each of you should look at and compare to previous runs the curve. When we tune a truck, this becomes as important as the actual numbers. On the electronic motors, this is less of an issue but is critical on the mechanical motors.



2nd – Correction factors. We all agree, these were not designed for forced induction engines. While they do help in leveling the playing field, they cannot be regarded as the absolute truth for comparing one truck/machine to the next. They can be used to compare on the same day/same machine. They can also be used pretty decently to compare at the same location, runs from different conditions between summer and winter. Here is where everyone needs to understand the differences. If you compare SAE corrected numbers, understand correction factors will vary from location to location, and day to day, or even hour to hour. A truck that makes 495hp with a 10% correction factor will be 450 without the correction. So if you dyno at another location with a 1. 0 correction (meaning no correction change) and all else being equal, you will dyno around 45hp less than your previous runs at 1. 10 correction. And since this is a percentage, a 700hp uncorrected run could be 770 with a 1. 10 correction. See how some can be disappointed? But regardless of the correction, the lines should still be the same, meaning power delivery should be the same. Also understand that when we dyno at the track, you cannot use SAE correction to calculate your MPH on the strip. If we have a 1. 10 correction, then we need to use the uncorrected numbers for trap speed. Uncorrected means what the vehicle ACTUALLY made to the rollers. So that is what you will ACTUALLY make on the strip. More on this later.



3rd – Loading vs Inertia. This one will be disputed forever. Some prefer to load while others prefer not to. I prefer inertia for my needs and here is why, but it shouldn't take away for the loading dynos. It is just MY preference. When running on my dyno, I can tell how well the motor is tuned. I can tell how well the turbo(s) respond which means I can tell how well the truck works in real world driving. If the truck won’t light on my dyno, it tells me the truck is laggy on the road. If you are a sled puller, not an issue. If this is a drag racer or street truck, it is. There is a myth that you cannot get enough load with a dyno jet with big turbo’s. It is true I have found some trucks that don’t work well on my machine, but was it the dyno’s fault. If I can make a large set of twins make 100 psi on my machine, or have a HX40/3B combo make 80 psi on the dyno, wouldn’t you agree I am working the truck? But understand, they were tuned on the dyno. They were not built then magically went on the dyno and did it. Any factory turbo’s will not have a problem on an inertia dyno. I have never had a case where stock turbo’s were a problem. As a matter of fact, in most cases only big singles have been a problem, and again, most of those could have been improved with tuning. What I don’t want to see happen is someone being convinced an inertia dyno will not provide accurate results when it may be they have a poorly tuned truck. Loading can mask these issues. Loading will bring the turbo(s) up but again, this can mask a tuning issue.



Loading dyno’s also require the operators to include run parameters so the software can accurately calculate. If the operator provides “rough estimates” with these parameters, then your results will be “rough estimates”. There are operators that are very competent and this is a non-issue. But there are some that are not. A Dyno Jet operator cannot change the run numbers with the exception of correction. I can choose between SAE, STD, DIN, EEC, etc but even with those, I cannot select how much correction to add. The dyno does that based on the weather station readings. This is one reason why the dyno jet is regarded by most as the most accurate from dyno to dyno. But I also want to express, there are loading dyno’s that I believe are run very well, deliver comparable numbers to my dyno and others.



Dyno Testing and to the Street/Strip



When I run trucks on the dyno, and they then are tuned to perform on the Dyno Jet, they usually become some of the sweetest trucks on the street you will drive. I’ll use Matt Stuckey’s truck as an example. Jeff has it tuned to 720-740 uncorrected hp on my dyno through the factory intercooler and a 40/3b combo. This truck makes 80 psi on the street, and 80 psi on the dyno. This truck will spool the turbo’s very well and as a result, on the street it is one of my favorite trucks to drive. Power is there anytime, without this awful lag to overcome. This makes everyday driving an absolute riot.



I use www.smokemup.com as the calculator to predict what these trucks will trap at. So far, this is the best one I have found. You will hear from many these don’t work for our trucks and to be honest, they are not perfect. But they are not perfect for the gassers either. Here is why. The algorithms used for these calculators cannot see the HP/TQ curves of your motor. All they know is your mph and vehicle weight, from which it will calculate your estimated rwHP. So if you make peak hp at 2500 rpm, but run down the track between 2700 and 3400 do you think it will be accurate? Racers should use the curves from a dyno run to determine how to run their truck down the strip. Meaning where the fat or the power curve is and where you need to operate the engine to deliver the most power for 1320 feet. When this happens, you might be surprised to see how well the calculators are at validating your dyno runs. Last year, I predicted what Jeff’s drag truck, Matt truck, and Darren’s truck would run before they ever made a pass. I gave each a 3 mph window and I hit each dead in the middle. You cannot use these numbers and calculators to estimate ET. There are way too many variables. This calculator cannot over come what diesel torque and a 4wd launch will do to a 6000 lbs truck. An example using my truck. It made 440 uncorrected hp on my dyno. It ran a 13. 89 @ 98 mph in 4wd. Best 2wd run was 14. 7 @ 98 mph. Using the calculator I get 429. 3hp with ET on the 2wd run, I get 508 on the 4wd pass. Using MPH, I get 441hp on both. Again, these calculators should be another TOOL to assist you in getting the maximum potential out of your truck.



In conclusion, I just want folks that don’t know, what benefit you can get from these tools, and I want to clear up those that say if you don’t load, don’t bother, or call a dyno jet, dyno junk, or blame a dyno for results that don’t meet the owners expectations. My suggestion is to instead of doubting the findings, try to explain WHY you had the results you had. If you run on my machine, and I believe we have left HP on the table, I will tell you. I will even go so far as to point you in the direction with the dyno sheet to a person that can help if I know. If you are not willing to listen, then you will always be chasing those that do listen and learn whether it is from me or someone else. And finally, there has been discussion on direct drive vs OD runs. On a Dyno Jet with a turbo diesel, it is suggested you use top gear. When loading it is suggested you use direct drive (1to1 ratio). I have done both on the dyno jet and the HP may vary a couple of HP and the TQ will be slightly higher in top gear. Where a problem will arise is with trucks with speed limiters. The newer trucks are tuned to make peak power near 3000 rpm. If I cannot reach that rpm in 5th gear then I will not see max power. A Duramax will make roughly 240hp in 5th against the limiter at about 2700 rpm and the curve is still on the rise. Just removing the limiter to allow the spin to 3200 will result in another 10 to 20 hp on these trucks. Unless there is a tech II or equivalent to hold the truck in 4th, this will be the case. So, what I am saying is if someone baselines stock with a speed limiter, they will dyno lower than another person that has removed the limiter with a programmer but not added any power.



Hopefully this will explain to some the dyno experience a little better for some. This is supposed to be fun and a learning experience. Nothing I hate more than to have someone unhappy after a dyno run. If I could make everyone have 800hp I would, but then you’d be wondering why you are not making 10 second ¼ mile passes.

It would take three day for me to read this. LOL.

 

[Turbo Thom]

Then I would say if that's to long for you ship it and go to another thread.



. . Preston. .

 

[Sled Puller]

Its worth reading.

DavidTD is the only dyno owner on this site that makes any sense whatsoever, and has realistic numbers for our trucks. But he understands Diesel engines, also.