1001 replies to this topic

[davew]

On my own dyno jet:

 

When I first bought the unit new, I had a problem with the cooling fan in the little red computer box. Dyno Jet sent me an entire new box, rather than dealing with a warrentee issue. I replaced the box and lost 2 hp. Put the old box back in and got my 2 hp back. Put the new unit in and lost the 2 hp again. All this was done within 5 minutes.

 

A few months ago, my dyno computer crashed. I was able to save all the history, but the dyno software had to be reinstalled. I lost another 2 hp with the newest software.

 

I can absolutely state that every dyno is going to be different.

 

Currently with a fresh 2015 Ti-Speed motor I am getting 126-117. Before the software change, I got 129-119 with 2014 spec motors.

 

Dave

[Steve Scheifler]

Well, from just your experience no you can't, but they are anyway.

Your experience with hardware and software is interesting and a bit unfortunate, but still not my point. Answer me this: If the best 1.6 you ever tested was consistently at or below 110/102, wouldn't you want to know rougly what that translates to at a popular shop? The answer is obvious. So I've been gathering more data points, starting with how long a good SM engine of each type takes to pull between two RPM points such as 4k-7k so I can set mine accordingly. The "equalization" data from the Autobahn efforts will provide just one more data point, sanity check, not be used by itself.

[Erik Hardy]

We have never gotten within even 5hp of the typical Dynojet numbers and our engines are certainly not off by 15 or more, so at least at the low HP levels we use I don't buy the claims that Dynapack reads high.
 

 

Hmm. In a thread sometime earlier in the year (maybe scca ncm thread?) you said that my car (1996 1.8Na) was pulling on yours. After the Gingerman majors race I was kind of frustrated with the power levels, so off to the dyno I went. The Dynojet read a whopping 108hp. I fully understand dynos read differently and there is variance associated with each, but to say I was 15hp down isn't that crazy...and If I was faster than you down the straight...I hate to break the news to you...(I have since built my own motor and ran it at Mid-O and the power levels were much closer; no dyno time yet, sorry for thread diversion)

[Jim Drago]

On my own dyno jet:
 
When I first bought the unit new, I had a problem with the cooling fan in the little red computer box. Dyno Jet sent me an entire new box, rather than dealing with a warrentee issue. I replaced the box and lost 2 hp. Put the old box back in and got my 2 hp back. Put the new unit in and lost the 2 hp again. All this was done within 5 minutes.
 
A few months ago, my dyno computer crashed. I was able to save all the history, but the dyno software had to be reinstalled. I lost another 2 hp with the newest software.
 
I can absolutely state that every dyno is going to be different.
 
Currently with a fresh 2015 Ti-Speed motor I am getting 126-117. Before the software change, I got 129-119 with 2014 spec motors.
 
Dave

I have two stacks( one as a spare), every time we have one re calibrated they come back different. Currently they read the same, but have read as much as 2/2 different in the past

[Jim Drago]

Steve - Dont bother. Between Drago's Dynojet, Rossini's DynoJet and Fowler's Dynojet we have MASSIVE number differences
 
A really good 99 on each Dynojet reads as follows
 
Drago     130 - 121
Rossini   125 - 117
Fowler    126 - 117

I just had Buras car off my dyno and immediately on to Toms in order to get a real comparison. It was a 2 HP diff, not 4 No idea on Mikes. I am sure we can use Chinese math to get there with your car on Mikes and Toms. I feel 99.99% certain on difference between Toms and mine.

[Ron Alan]

Rich...your numbers mean nothing to me writen like you did. How about this(and maybe this is what is there, not sure)

 

Min speed at turn 5 for both cars.

Max speed before turn 6

Min speed at turn 6

Max speed before 8(braking top of hill)

 

And ideally these would be laps with no traffic in front for either...if not take a 3 lap average for both.

 

My guess is they may cover the distance in the same time but the 1.6 does it by better corner speed while the 99 does it with better acceleration. 

[RWP80000]

Steve, 

 

All good points.  We have been doing our testing on a Dynapac and the numbers are right in line with the numbers Jim Drago  is showing for his Dynojet.  I don't consider the Dynapac we currently are using to be high but I have seen much lower numbers at another Dynapac facility.  

 

Some of this could be weather station issues but I would be more inclined to be looking at load cell output (calibration).  I like the Dynapac because it eliminates the variables of the vehicle connection to the Dyno it'self.  Tire pressure/sidewall  factors and slip between the drum (tie down issues) are eliminated.  Remember, the only thing the Dyno is supposed to be measuring is the torque output for accelerating the vehicle.  Eliminating or avoiding any variation to the process of measuring and collecting torque output is the key to consistent and repeatable results.  

 

Dyno variation is a big issue to consider and can make the money spent on testing a total waste while also causing confusion and incorrect conclusions.. You need to be able to measure change with a high degree of confidence which means results need to be repeatable hence the need for correction factors but knowing and having your uncorrected torque values are insiteful.  

 

To help in doing this we try to limit the window of temperature, humidity and barometer conditions under which we test. Humidity is the one variable that is allowed to vary the most as we try to restrict the time of year/day for temperature ranges within a 20 deg (65-85F). range and Baro is mostly a function of site location but here again is easy to monitor for variation due to weather fronts.  What weather condition variation we see is handled with the an SAE correction, just be consistent in the one you use.  I like to work with the raw torque data and apply my own correction factors just to verify the numbers being generated.

 

Next is the variable in back to back pulls.  This is generally the car it's self.  Here you are dealing with engine and driveline temperatures which means properly stablizing the car as well as reasonable and possibly the Dyno itself.  For this you need to repeat pulls with out any changes to narrow down natural run to run variability.  This all takes time and adds to session costs unless you own the dyno.  The next thing if you are really serious in your confidence in your conclusions is to run a second car.  We have been running two cars back to back for every test session this year.  If we change an engine in one we run the other car as a "reality" check on numbers.  When doing this you can spot any outlier and can save on the hassle of having to change your car back to it's baseline configuration to verify your baseline.

 

So in summary what I am saying is use one dyno, limit the environmental conditions you test in, stabilize test conditions and run a check vehicle.  Even with that you are still at the mercy of the condition and quality of equipment you are on, its accuracy of calibration/quality of sensors being used.  Things like where the weather station picks up its readings no matter how good the station is it'self can introduce variation.  How accurate is the dyno (load cell) and its calibration, is it totally free of any preload or alignment/friction issuses.  If you use a shop that specializes in your particular vehicle (spec miata) chances are you can rely on their background data to help you have a high degree of confidence in the numbers you are getting but it is up to you to make sure you are aware of the obvious items that can cause variability are addressed to your satisfaction.

 

Rich 

[Johnny D]

I don't really follow why you need hard numbers.

 

Does it help to use %'s

01 HP       101%

99 HP       100%

1.8            97.6%

1.6            96%

 

You're taking a snap shot in time with all factors, (an apple) and in theory you can compare another apple and another snap shot time. correct?

Just saying.

J~

[Jim Drago]

Steve, 
 
All good points.  We have been doing our testing on a Dynapac and the numbers are right in line with the numbers Jim Drago  is showing for his Dynojet.  I don't consider the Dynapac we currently are using to be high but I have seen much lower numbers at another Dynapac facility.  
 
Some of this could be weather station issues but I would be more inclined to be looking at load cell output (calibration).  I like the Dynapac because it eliminates the variables of the vehicle connection to the Dyno it'self.  Tire pressure/sidewall  factors and slip between the drum (tie down issues) are eliminated.  Remember, the only thing the Dyno is supposed to be measuring is the torque output for accelerating the vehicle.  Eliminating or avoiding any variation to the process of measuring and collecting torque output is the key to consistent and repeatable results.  
 
Dyno variation is a big issue to consider and can make the money spent on testing a total waste while also causing confusion and incorrect conclusions.. You need to be able to measure change with a high degree of confidence which means results need to be repeatable hence the need for correction factors but knowing and having your uncorrected torque values are insiteful.  
 
To help in doing this we try to limit the window of temperature, humidity and barometer conditions under which we test. Humidity is the one variable that is allowed to vary the most as we try to restrict the time of year/day for temperature ranges within a 20 deg (65-85F). range and Baro is mostly a function of site location but here again is easy to monitor for variation due to weather fronts.  What weather condition variation we see is handled with the an SAE correction, just be consistent in the one you use.  I like to work with the raw torque data and apply my own correction factors just to verify the numbers being generated.
 
Next is the variable in back to back pulls.  This is generally the car it's self.  Here you are dealing with engine and driveline temperatures which means properly stablizing the car as well as reasonable and possibly the Dyno itself.  For this you need to repeat pulls with out any changes to narrow down natural run to run variability.  This all takes time and adds to session costs unless you own the dyno.  The next thing if you are really serious in your confidence in your conclusions is to run a second car.  We have been running two cars back to back for every test session this year.  If we change an engine in one we run the other car as a "reality" check on numbers.  When doing this you can spot any outlier and can save on the hassle of having to change your car back to it's baseline configuration to verify your baseline.
 
So in summary what I am saying is use one dyno, limit the environmental conditions you test in, stabilize test conditions and run a check vehicle.  Even with that you are still at the mercy of the condition and quality of equipment you are on, its accuracy of calibration/quality of sensors being used.  Things like where the weather station picks up its readings no matter how good the station is it'self can introduce variation.  How accurate is the dyno (load cell) and its calibration, is it totally free of any preload or alignment/friction issuses.  If you use a shop that specializes in your particular vehicle (spec miata) chances are you can rely on their background data to help you have a high degree of confidence in the numbers you are getting but it is up to you to make sure you are aware of the obvious items that can cause variability are addressed to your satisfaction.
 
Rich

All very good advice.
Thanks Rich

[ECOBRAP]

Rich...your numbers mean nothing to me writen like you did. How about this(and maybe this is what is there, not sure)

 

Min speed at turn 5 for both cars.

Max speed before turn 6

Min speed at turn 6

Max speed before 8(braking top of hill)

 

And ideally these would be laps with no traffic in front for either...if not take a 3 lap average for both.

 

My guess is they may cover the distance in the same time but the 1.6 does it by better corner speed while the 99 does it with better acceleration. 

 

 

Front straight at Laguna from the NASA Championships (slowest speed on track to fastest speed on track).

 

Top yellow is Steve's '99 (lower minimum speed, +57.9mph, higher max speed)

Bottom red is my 1.6 (higher minimum speed, +56.2mph, lower max speed)

 

Looked at multiple straights and multiple laps and the results are the same. 1.6 has higher minimum speeds, and '99 has better acceleration deltas. Exactly what you should expect from the lighter weight of the 1.6, and the better hp/tq/wt ratios of the '99. Yes it did equate to similar laptimes, but as has been said many times before, racing the car is very different to qualifying. I just got lucky that whenever Steve had a run he pushed me past another car instead of going 3 wide... thanks Steve!

 

So how about weights stay the same for qualifying, but all 1.8's have to add another 25lbs for the race 

 

Jokes aside, I am happy to send my data files to the SMAC, and Rich probably is too! Data overlay between the different chassis/engine types would be very useful IMO.

[Steve Scheifler]

Hmm. In a thread sometime earlier in the year (maybe scca ncm thread?) you said that my car (1996 1.8Na) was pulling on yours. After the Gingerman majors race I was kind of frustrated with the power levels, so off to the dyno I went. The Dynojet read a whopping 108hp. I fully understand dynos read differently and there is variance associated with each, but to say I was 15hp down isn't that crazy...and If I was faster than you down the straight...I hate to break the news to you...(I have since built my own motor and ran it at Mid-O and the power levels were much closer; no dyno time yet, sorry for thread diversion)

Must have been that 1.8 torque, or you were faster off the corners that I gave credit for. But I think I compared a stretch where we were at equal speed after the corner. Don't recall for certain, I was trying to get a sense of that with several cars and it's tougher at a new track. In any case, you were plenty fast with the power you had, don't be rushing into something you might not be able to handle. :-)

[Steve Scheifler]

All very good advice.
Thanks Rich

Yep, and that's just the easy stuff. (Do I sound like Danny? )

[Danny Steyn]

Rich, having a reference car or sled is an important aspect in DYNO's IMO. One of the largest and most successful SRF shops has a dedicated SRF that never races. It is the first car that is tied down to the dyno each day, it is warmed up and since it doesn't change from session to session it needs very little optimization. Once the numbers peak on the reference car, then they load and test the other cars. In their experience and ours there can be variances on the dyno from day to day for sure

[RWP80000]

Ron- When you lay Matt's speed trace over Steve's there is very little difference in the actual characteristic of the trace which is telling me the cars are dynamically very similar.  I have added info to show where the values you were looking for were in my data I corrected the data in the underlined portion from what I had the wrong values.  Hope this helps explain.

 

Lap Time           Track Dist            Matt MPH      Steve    Segment Event

(sec's from S/F)  (Feet from S/F)    MPH            MPH       (activity related to Segment) 

  48.234               5383.4 ft           66.3            68.9         Lowest speed at point just before climb up hill

  58.056               6492.6              85.4            85.3         Max Speed B4 lifting for at Turn 6

  1:00.027            6724                 82.1            78.9         Resumption of accel aft Turn 6 

  1:08.86              7866.7              89.4            89.3          Speed just prior to decel down hill

 

I am adding a link to tan AIM Race Studio 2 software screen shot which have the two laps "aligned" at the Start/Finish line.  This overlay has the GPS Longitudinal and Gyro data (there is only RPM data is for Steve car).  I think this picture best conveys better how similar the cars were and if you didn't have identifier tags on the data I would be hard press to know which was which. The variation between these two cars was in the same range of the lap to lap variation of the individual car.  Matt brought up a good point about getting a push from Steve but I don't think this shows up in the data as his Solo was acting up at this point in the Race.

 

Rich

 

Dropbox link to AIM Data Chart of 1.6L vs 99 1.8L at Laguna Seca NASA Western Championship race.

https://dl.dropboxus...NASA Champs.jpg

[Danny Steyn]

Rich

 

for the AIM data, now take ONLY the velocity/Distance trace and maximize it to take up the full screen . This will allow you to really see the acceleration traces accurately

[RWP80000]

Danny,

Thanks, that is a big  improvement.  Drop link attached.

Rich

 

https://dl.dropboxus...ce 16v99 18.jpg

[Todd Green]

I'm all for data, but watching Matt's vid that goes with the data pretty much sums up the life of a 1.6 in a nutshell watching this run down the front straight (Grrr the forum strips off the t=8m54s parameter, so if you click on the vid skip to that time stamp.)
 
https://www.youtube....BjqQ6c0#t=8m54s
 
He starts on the tail of Steve, then a gap is pulled down the straight, and then he makes it up under braking, and is back at square one.  This is what makes racing a 1.6 hard.
 
Edit: Weird, so I put in a second link using #t instead of &t and it decided to stop showing a preview for the video.  Even removing the link wouldn't revert to showing a preview.  So click on the link and it'll take you to the vid at the correct timestamp.  (At least in my testing.)  IPBoard is some weird software.

[Jamz14]

Delete

[Todd Green]

Or should he be equal or better on the straight and an advantage under braking too?

Does this really need to be spelled out for you?  Parity means the same braking, accelerating, and cornering.  Good luck getting that perfect on cars with different displacements, suspensions, weights, etc.

 

Why is it somehow harder for the advantage to be braking?

 

Because it is much harder to pass someone under braking and maintain the advantage though the corner and down the next straight when they have more acceleration than you.  It isn't terribly difficult to drive by someone on a straight (when you have more acceleration.)  Go race some out of class car that is two seconds a lap slower than you, but is significantly faster in the straights and significantly slower in the corners and see how easy it is to pass them.  Now go race a SM that is two seconds a lap slower and see how easy it is to pass them.  You'll find the SM is much easier to pass.  What you see between the 99+ and the 1.6 is this scenario (out of class), just that the differentials are much, much smaller.

[38bfast]

i am not clear as to what some are asking. Asking to add power to the 1.6. And then saying if its over to add weight and or a plate. So its ok to add the power (spend the time and money) and then loose a portion of it via weight and plate if needed? So to paraphrase give us power but its ok to take it away if you see fit.