# Dyno to track inconsistencies



## Boosted-Z71 (Nov 26, 2007)

I am sure all of you have seen or had a car that is a real performer on the dyno and just a regular performer on the track and vice versa, and I do agree dyno runs are just numbers. But the numbers should have some kind of track relation once you establish a base line comparison. 

I am seeing this in a car that has great electrical contact, the brush pattern is right, the pick up shoe contact patch is right, tires are round, the list of things that are checking out correct, goes on etc. 

It screams on the dyno, great output in RPM, voltage and amp draw. But is just an average car on the track in terms of straight away speed. Dyno voltage and amperage on the dyno setup are exactly the same (as close as my Fluke will measure) to existing conditions as the track, I cannot accurately check the rpm on the track to compare to the dyno results. 

Conversely I have cars with marginal output on the dyno that really run great on the track. I know the dyno is only a tool, but with the data I take during a dyno run I think similar results in 2 cars on the dyno should produce similar results from said cars on the track, with equal test conditions in both locations. The dyno is very consistent as I have data from cars that I ran on it over 1 year ago, that still produce the same numbers when tested. 

I am not talking about total lap times, but more concerned with acceleration & top end speed, both are very easy to compare car to car on the track, and number to number on the dyno. 

I build t-jets from a fairly proven assembly recipe, it seems that 95% of the time I get an above average car (compared to well known runners in my stable), the other 5% are the oddities.

Anyone have any information or theory they want to throw at this as a possible answer or some other variables that I am missing?

Boosted


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## Hornet (Dec 1, 2005)

I forget,but does your dyno have the capability to load the motor.
Rick


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## ajd350 (Sep 18, 2005)

A dyno can be a very useful tool as long as you take into account it's limitations. When you test a car on a dyno it is in a fairly static state. It will not show if you have inconsistent contact in the hook area of the shoe as the car moves around the track. It will also not show up any drag in the front wheels or axle. Torque is hard to measure without a proper load, so magnets that have skewed field patterns may get you RPM, but less torque. That can look OK on a dyno, but feel soft on the track. You get the picture. It is a good tool, but the track is the ultimate dyno.


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## Boosted-Z71 (Nov 26, 2007)

Hornet, my dyno has some drag due to the gear/roller setup that the Tamayia unit used to measure speed, but not a variable load ability like you and I talked about once, that may soon change. For me an easy fix to increase the load on the rollers would be to add a small friction brake with a return / apply spring that I could easily adjust, the question is how much load on the rollers do you need? I really dont know where to begin, and does the load need to increase with the increase in power applied to the car?. I have a regular hand controller on my dyno that I can apply various loads/speeds to the car while on the dyno, not sure if this is a good thing but I gives me the capability to get data at various points with speeds and loads / output to look at. 

AJD, As for the static aspect of the dyno I fully agree, but these cars get the coast / gravity test to determine their free-wheeling-ness of the chassis & gear plate assembly. I dont think I am loosing any more from car 1 to car 2 as far as friction losses as long as they freewheel a similar distance. 

In terms of the hook contact area, if I did have a problem am I correct in thinking that I would see my amperage draw bounce around while the car was moving, correct? Had not thought about the magnet field aspect, need a little time to ponder the correct method to test & compare the 2 cars, I can tell you that the magnets produce very similar values installed in a test chassis on the BRP matcher and the mag to stack clearance is within .001 difference between the cars. Arm stacks are within .002 diameter of each other.

Thanks guys for your input, just something to ponder that I have been kicking around for quite a while.

Boosted


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## Bill Hall (Jan 6, 2007)

I was kinda leaning towards the hook area too.


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## Hornet (Dec 1, 2005)

I don't run T-jets on mine,but the extra slave motor when it's in full short mode puts a fair strain on things,i have the extra slave shorted out through a big old army surplus 25 ohm pot (the things like 4" in diameter),and it gives quite a bit of load adjustability 
I've ran into arms that will RPM high on just the dyno slave,but as soon as i put them under load with the extra slave they'll fall off,and quite often run hotter.

I like your idea for an adjustable load,i think anything that you can control the load with will work,and the simpler the better,so i like your idea.

I use a good old cheap household dimmer switch to vary the input to the battery charger i use to run mine,but normally i run it at full voltage,and use the loadable slave to see how the car does under load,but in reality the track and your ears are still the best dyno.
Rick


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## ajd350 (Sep 18, 2005)

Boosted, You have good point on the coast-down. I was referring to possible drag in the front axle/wheel assembly. It's amazing how much a nearly imperceptible drag can make a car feel like it's dragging a boat anchor. Tha dyno cannot evaluate that. As far as the hook, they can be tricky to diag sometimes. On the dyno the shoes may vibrate aroud a bit, but on the track they constantly bounce and twist. A problem there will eventually show up as micro-arc burn marks in the hook. The underside of the plate where the hook rides is easily overlooked because we can't see it. Dragging a strip of sanding film through there can clean the surface and help increase the contact area to the hook. Been there, fought that.
The shape of the magnetic field is different than the overall strength. When it is not even across the face, it affects the timing of the motor. A matcher will not read that. Amazing how complex these little toys are, no? I hope this is helpful.


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## Boosted-Z71 (Nov 26, 2007)

AJD, you are totally correct, these are little animals, and the more we attempt to tweak and finesse for speed the more contrary they get, I will do some checking on the pickups but I have not noticed nor seen any arcing or burn on the hook or shoe area. I have a jig to rotate the magnet equally around the BRP matcher, but I doubt it is really telling the truth as you very seldom find a set of magnets with an equal reading around the face area. I may play with some steel powder and some magnets, (kinda like the toys you used to draw the beard on the guy with) that may be the easiest way to get a visual of the magnetic field strength around the face?

Thanks, although we may not have a solution, all your comments are very helpful

Boosted


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## ajd350 (Sep 18, 2005)

You got it. I know a couple of guys who use those beard toys to get a read on the mags and say it works pretty well. Got to get me one of those. It may save some time swapping mags around blindly. BTW, I use a magnifier to look at the hooks. The burn marks can be very small if they are there. Aint this fun?


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## Boosted-Z71 (Nov 26, 2007)

ajd350 said:


> BTW, I use a magnifier to look at the hooks. The burn marks can be very small if they are there. Aint this fun?


Ha Ha, my eyes are getting so bad up close I almost need a magnifier to see the car, I am kicking and screaming trying to avoid glasses. Maybe that is the problem.

Thanks again

Boosted


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## Bill Hall (Jan 6, 2007)

*Magic Eight Ball sez...*

I LOVE these types of threads where we all shake the Eightball and try and diagnose someone's car sight unseen. 

Ordinarily I scratch the scuzz from under the hanger plate using either the pokey brush from the automotive light socket cleaner brush set, cram the dremel wire brush under it by hand, or drag some sandpaper under it. 

Toss the chassis in the tarnex for a sec and be sure to wiggle the plates if they're loose at all, rinse with hot water and blow it dry with compressed air. Then I bop the rivets and mumble some sort of prayer to the slot gods. 

The only reason I'm hung up on the hanger plate hook thing is that anytime you consistently build and sort something out successfully, you often return to the fundamentals. It's no secret that whatever type mechanical joint is used to transfer current like the hanger plate shoe hook set up on a t-jet, or the brush tube shoe hook on a modern inline the oppurtunity for gremlins presents itself. It's wiggling jiggling silly affair without backup. 

If yer still plagued, why not go redundant put on a set of shunts for giggles. Then see if you improve to your normally expected build standard?

Additionally: Not all shoe hooks are created equally. I have had certain after market t-jet shoes like BSRT slop around in the hanger plate and work fine...than again I've also had them create some erratic or intermittent driveablility issues as well. Certainly the hanger slot itself can be out of tolerance as well....and like always....maybe there is more than one problem?

Guide pin subtly bent or cockeyed?....maybe pivoted off center? Mounting screw dragging? Front axle properly lubricated? I've had them weird out at certain rpms when the nose gets light under acceleration or the chassis settles entering or exiting in turns. Inspite of passing the coast test. 

What about coil bind on the pick up springs? The closer you get to the ragged edge the easier it is for the slightest variation in rail height to scrub off speed?

Did ya miss a bent wheel/rim or lumpy tire?

Just firing off randomly here...


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## ajd350 (Sep 18, 2005)

LOL....What a can of worms the hanger plate and hook can be. All the way back when I was just a squirt, shunt wires were a quick and easy way to eliminate all the maybes. Now someone decided in most of the TJet based rules to ban them. I guess it was in the name of purity or simplicity or maybe just to induce hair pulling (something I can't afford to do these days). It sounds like we've been down many of the same roads, Bill.


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## Dyno (Jan 26, 2009)

Hey Boosted, 
I havent been messin with the slots so much when its warm out, but now the weathers changed and Im slowly getting back to my old ways. Last fall, I finally got around to building a dyno. I added a flywheel to it for some drag and actually was able to hook it up to a PC utilizing dyno software so I can actually see exactly how fast the motor is accelerating as opposed to only its top end RPM. I can graph the results and even predict its quarter mile ET. I dont have a drag strip so I cant tell you if that feature is working acurately. I tested two cars, a fast stock 16 ohm tjet vs a mild 6 ohm Wild Ones. The stocker kicked the Wild Ones ass for topend by quite a bit, BUT when you looked at the rate of change, the Wild Ones was much quicker to its top rpm. I then track tested the cars and sure enough the Wild Ones was the victor. My point is, that the car in question is probably making no torque. The Dyno numbers look good but it is in fact accelerating slowly.


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## Boosted-Z71 (Nov 26, 2007)

Very interesting Dyno, I am in the middle of adding a slave motor, load pot and a dedicated amp/volt meter to my setup, I always thought that torque might be the issue here as the car was just a dog on the track but a real performer in numbers on the dyno rig. 

Post some pics of your dyno/computer, really like the idea of being able to collect and graph the data.

Boosted


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## Hornet (Dec 1, 2005)

Hey Dyno,do you have any pics of your dyno,i think Boosted and i both would be interested in how you did your dyno,and it's computor tie-in.
Rick


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## Dyno (Jan 26, 2009)

I will post a picture when I get a minute, probably later tonight.


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## Hornet (Dec 1, 2005)

Thanks Dyno,i think it'll be muchly appreciated.
Jeff,i just remembered what you'd said about your load-able slave,is it a 3 ohm green wire can motor.

Rick


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## Dyno (Jan 26, 2009)

Here are some quick pictures. Not too fancy, but effective. The Mickey Mouse sticker is there because its a Mickey Mouse machine...lol


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## Hornet (Dec 1, 2005)

Now there's some thinking,it looks good:thumbsup:.

Hey Dyno,any chance you'd do a write up on how you fabbed it together and tied it to a putor,sensors/parts used etc.

I'm interested in how you did it,and i bet there's a few more guys who are too:wave:

My homebuilt dyno,is well over 10 yrs old,and is definitely old school rude and crude compared to what you've done,and doesn't tie into a graphing program,so you'res is really intriguing me:thumbsup:
Rick


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## smalltime (Jun 3, 2006)

Bill Hall said:


> I LOVE these types of threads where we all shake the Eightball and try and diagnose someone's car sight unseen.
> 
> Ordinarily I scratch the scuzz from under the hanger plate using either the pokey brush from the automotive light socket cleaner brush set, cram the dremel wire brush under it by hand, or drag some sandpaper under it.
> 
> ...


I think Bill is on to sumpin here. I'd look at the shoes, and the hangers. I will tell you, I don't think I have a single chassis anymore that has the same brand of shoe on both sides. I've become Mr. mix and match. 

My favorite is the phsycho settup. A Wizzard on one side and a Slottech on the other.

Shoes are such a black art. I would say if your dyno thingy says it's a good chassis, then play with shoe settups on the track.


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## Hornet (Dec 1, 2005)

LMAO hsycho set-up gotta remember that one Tim.

Here's a link to my old dual motor'd dyno,that uses 3 meters.
One to measure amp draw,another one measures input power to dyno,and the third meter reads output voltage from the wheel driven slave.
The extra slave motor is on a 25 ohm pot,it provides the adjustable load.
As you can see mine is real old school,it's over 10 yrs old,and is pretty simple compared to the state of the art stuff you guys are building now-a-days.
I'd sure be interested in reading any write-ups you guys would consider doing on how you built your dyno's,both your dyno and Boosted's dyno,are quite intriguing to me.:thumbsup:
Thanks guys
Rick

http://routedtracks.yuku.com/topic/29/Re-Homemade-Dyno?page=-1

I use an old disected 6V/12V 6amp battery charger as a bench top supply to run it.
I cleaned the charger up a bit with some filtering caps,and use a cheap old 120V household dimmer switch to give it some adjustability


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## dennis07 (Dec 7, 2011)

Keep it coming guys. This is a great read for all of us novices (at least for me anyway). These types of threads help us all get a little better performance out of our T-Jets.


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## Boosted-Z71 (Nov 26, 2007)

Hornet said:


> Thanks Dyno,i think it'll be muchly appreciated.
> Jeff,i just remembered what you'd said about your load-able slave,is it a 3 ohm green wire can motor.
> 
> Rick


I will measure it today and let you know, is that a problem?

Boosted


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## Hornet (Dec 1, 2005)

I don't think it'll apply as much load as a stock can will,that's more in the 6 to 7 ohm range,i'm not totally positive on that one,but that's my thinking.
It might s'plain some things


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## tossedman (Mar 19, 2006)

This is all pretty interesting guys. I have Rick's Dino Dyno. The old one before to one you see over at the link he posted above. It's about 43 times bigger that yours Dyno. I sometimes wonder if I'd have to rewire the basement for three phase wiring before I fire it up. Lol, just kidding Rick. Here's a shot. It works just fine.










I'd love to see how you guys put yours together as I'd like to learn more about 'em. I wouldn't mind putting one together myself and I like the look of yours Dyno. Nice and small. Boosted your's sounds interesting as well. 

I don't suppose either of you'd like to share a "how to" and some more pics about how you put those things together would ya?

Cheers eh,

Todd


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## slotking (May 27, 2008)

I use the dyno only to check a car vs itself!

Did I make my car faster or slower???

the problem with comparing car 1 vs car 2 is that the arm may be different
the motor mags? the gearing?

I have had cars(t-jets) that read 1.4 on my VRP dyno that will beat faster dyno cars because it has better torque.

I have had cars that hit 1.7 and have both torque and top end.

sticking with t-jets, the nostalgia car often read much higher on the dyno than the fray cars. why? the weaker magnets make for higher top end.

So take a slow car, put on the dyno, keep the reading, now tweak the car!
is faster or slower on the dyno
if faster, track test it


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## smalltime (Jun 3, 2006)

tossedman said:


> This is all pretty interesting guys. I have Rick's Dino Dyno. The old one before to one you see over at the link he posted above. It's about 43 times bigger that yours Dyno. I sometimes wonder if I'd have to rewire the basement for three phase wiring before I fire it up. Lol, just kidding Rick. Here's a shot. It works just fine.
> 
> 
> 
> ...


Wow,
Rube Goldberg would be proud.


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## Dyno Dom (May 26, 2007)

Dyno said:


> Hey Boosted,
> I havent been messin with the slots so much when its warm out, but now the weathers changed and Im slowly getting back to my old ways.
> Uh-Oh, Seasons have changed, hide all the track records, Dyno is back in the groove. :wave:
> D, I met Dave @ the last show & asked for you. :thumbsup:


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## Hornet (Dec 1, 2005)

Tim that's the portable one,lol..
Todd didn't show it,but it's also set-up to turn a cheap rotary tool into an infinitely variable speed rotary tool.
I even threw in the rotary tool for him,lol:wave:.
That's what a couple of the extra electrical boxes house.
Hey i built it with what i had on hand one Sunday,lol
Rick


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## tossedman (Mar 19, 2006)

smalltime said:


> Wow,
> Rube Goldberg would be proud.


Yeah but it works and it's better than the one I didn't have before!


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## Dyno (Jan 26, 2009)

Dyno Dom said:


> Dyno said:
> 
> 
> > Uh-Oh, Seasons have changed, hide all the track records, Dyno is back in the groove. :wave:
> ...


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## Dyno Dom (May 26, 2007)

Hi Dyno, yes I would like to host another Fracas run. Be warned, with
your race win and lap record, the target is on your back. I'm sure the guys,
(Dave, Nick, Big E, Bob 528, GearHead & Joe Mig) will be gunning for you.
Hopefully we can round up some HP dudes from NJ, I know Joe GS wants 
to take a shot.


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## Dyno (Jan 26, 2009)

Yeah, I have the big bullseye on my back. The chances of me pulling that off again are pretty slim . Don't get ne wrong I will try like hell though.:thumbsup:


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## Hornet (Dec 1, 2005)

Boosted just passed a great tip on:thumbsup:.
His Mcgivering ability blows me away,he's always amazing me,lol.:wave:

Any you guys with a homebuilt dyno that uses can motors as a slave,try adding an extra set of Neo mags to the outside of the can.

My dyno wouldn't really load my Neo cars all that well,and i tried Jeff's tip about adding extra Neo mags,man what a differance,i can only stick a Neo mag on one side of my can motor,but it'll pull my Neo cars down very well now.

Thanks Jeff,great tip:thumbsup:
Rick.

Hey Dyno,what are you using as sensors and tie-ins on your dyno,i'm still really intrigued by your set-up.


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## Hornet (Dec 1, 2005)

Hey Boosted,you should post pictures of your latest Frankenstein creation.
Jeff's got his dyno figured out and working better then any of the aftermarket dyno's out there these days.
It impressives me immensely,and i think it'd impress most guys:thumbsup:.
He's mumbling about building them and selling them,if he does,i'm gonna be on the list,as i want one:thumbsup:
Rick


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## Boosted-Z71 (Nov 26, 2007)

Thanks Rick, I am working on making a small video of the setup and it functioning, unfortunately I know way less about video & cameras, than some guys know about computers, Rick I am sure you know what I mean. So that tells you where I am at with the video. 

I setup a simple test this morning with a grouping of 3 cars per sample, taking readings from my dyno, then duplicated the runs on another dyno setup that I have access to. I am not looking for one dyno to confirm the output number readings on the other unit, but was using this as a comparison to see which unit would identify the track dog or slow car, just from the dyno runs. I got some good results but I want to refine the test procedure just a little, as I need to build another fully adjustable power supply to even the field on input voltage between the units. 

But with the data I got, I was able to pick the track dog on my setup consistently, not always so on the 2nd unit, I saw several cars on dyno #2 that again gave good numbers on the dyno but were not the top in the group on the track test. I went through 21 cars, cars that I dug out of my collection that I don't run every day, so I did not know what to expect from them, my only info on their performance was from readings on the dyno's. I was able to estimate the fastest car of the group with my dyno, then made confirmation on the track. Cars with similar dyno numbers from different test groups also ran similar speeds on the track, (like fender to fender close), amazing huh. At least to me that makes sense, and sounds logical in theory, especially If I am getting matching information from my testing source and able to prove those results on the track. 

I am only considering the simplest handling characteristics, and mainly focused on car HP & torque numbers that it takes to propel the car down the straight, so a car that makes good numbers on the dyno should go down a smooth routed track 15 foot straightaway at a given pace, provided the pickups and track rails are clean and the tires are in good shape and not loosing traction, if car A proves better on the dyno than car B, then A should be ahead down the straightaway at the end, and this difference should be measurable on the dyno, and that is what I am getting now on my setup. 

More to come later, Like I said earlier I am working on a video but, I am really weak with cameras, so be patient.

Boosted


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## Hornet (Dec 1, 2005)

LOL,putors,aarrgghh,

Hey at least you got the regulators down pat ,i bet you could build them in your sleep now:thumbsup:.

I'm sure waiting for your video,let me see if my camera guy will help,hey TODD,he he he:wave:.

If i yell help loud enough,and he usually hears,and comes to my rescue,lol 

Jeff if you decide to go into production,put my name on the top of the list,i've been drooling over your pictures since last night,now i want one,lol:wave:
Rick


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## Boosted-Z71 (Nov 26, 2007)

Hornet said:


> Hey at least you got the regulators down pat ,i bet you could build them in your sleep now:thumbsup:./QUOTE]
> 
> I see them in my sleep alrgiht, I still have nightmares over those stinking adjustable regulators, but yes I think I have them figured out now, finally.
> Who would have ever thought it was the mounting point that was screwing everything up, I built & cut back out that one for the power supply twice, so that is the 3rd setup in there, Hey I guess the 3rd time is the charm!.
> ...


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## Hornet (Dec 1, 2005)

Took me awhile to sort mine out,the first time i built them.
They just about drove me nuts,figuring out what was wrong
But it's something we'll never forget now,lol


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