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Dyno experts needed to help identify or advise on used dyno purchase

Practical Dyno Tuning

Discussion and questions related to the course Practical Dyno Tuning


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Hi guys, I'm new here and super excited to get tuning. I run an automotive workshop in Australia and decided to get a workshop project car going and learn how to tune from scratch. I've just got my HP tuner kit plus my Innovate LM-2. I'd love to have a dyno but at this stage of tuning, the cost is way too much to make it viable for us, considering it would be seldom used in our shop. Although, I have found a very very VERY cheap used old dyno but it has no computer software, no tie down points, and potentially no output sockets to go to a computer(that he can see). I'm wondering if any of you guru's might know what this old girl is and give me some pointers as to whether this would be a waste of money even though its cheap. All I would want it for is a power read out - not interested in MBT or anything like that at this stage as I will only be re-flashing. If possible, I would look for open source dyno software for this but once again, not sure if that is possible. Any help would be greatly appreciated!!

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I don't think i have ever seen a friction braked commercial dyno but if you can mount a load cell (or it already has one) in the right place and a roller speed pixkup you will be able to generate a tractive effort/power figure. Mainline were offering control/software packages for older stuff in the past. If you are happy with manual load setting you should be able to get a rough effective radius for load cell and work out something close for roller inertia and friction to generate reasonably repeatable tractive effort/power figures for adjusting mapping. You do want to be chasing MBT even for reflash tunes, the way you go aboutbit may be post processing logged data rather than the more convenient speed hold on modern load hold dynos/live tune ecus however.

If mainlone is a no go most industrial plc/programming people should be able to give you an interface package. The time/money is in presentation/automated comms/build in log overlay type stuff but if you are happy just to complie CSV output from ecu and a dyno calculated tractive effort and roller speed channels and do the map table stuff in megalog or whatever your tuning package is it should be cheap enough, preferably logging into one piece of software to avoid having to manually align ecu/dyno data.

Thanks for the response Michael.

I ended up going to see it this afternoon and looks really basic and old, which is completely fine so long as I can make it work the way I want. He says it is non braked, that the braking system on the right is pneumatically controlled with a tap in an airline and it locks the front roller so you can drive on and then unlocks to drive off. To be honest, I'm not even sure the guy knows what he was talking about. I took a few more up close pics if you can see anything on there to make you believe any different?

I'd be definitely trying to do everything on the cheap as it will be my own hobby money I would be throwing at it. I just have no idea what I would need to be able to get it to show a power figure. So I would need a load cell attached somehow and some sort of RPM pick up for a roller? Happy to have the most basic look on a screen to see the power figure so not too worried about upspec software packages as most of the logging for air fuel ratios etc, I can pick up with my VCM scanner and the LM-2 Wideband set up.

What do you think?

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It is likely just inertia if it is only air pressure supply to the brake calipers. In that case it is just an inertia estimate and friction estimate and a bit of maths in a spreadsheet for logs. Not knowing what options you have for displaying ecu log data makes it a bit harder to suggest a specifuc technique but if it is mostly NA stuff I guess trying to maintain a fixed throttle and do sweeps from off idle to redline in top gear. I have an LM2 myself, I will be using my Plex datalogger/software to actually process my own stuff but I think you can take in a speed input on the lm2 so worst case you log via your lm2 and ecu software at the same time and correlate engine speed/roller speed andveven if you don't have maths channels you can do a basic numerical differentiation for roller acceleration. Bit busy this week but if you get yourself underway I'm happy to make a demo spreadsheet with instructions if you can't take it all into one powerful logging package. It will allow you to tune MBT well enough for all the high load areas and you may find with high temp pads and a good cooling fan as well as an extra air pressure reg of the right type you may be able to fit a load cell in the brake caliper mount and do light steady state/slower ramps later on.

I will have a chat to him tomorrow and see what we come up with. I'm thinking it might even be worth getting even if I can't get a power output from it like you said. If you did have time for the demo spreadsheet, that would be greatly appreciated! Also very thankful for your help so far.

I can't think of any good reason for it to have that wound resistor/wiper in there and the shock (and i assume a spring or strained element) unless it is to act as a crude load cell. I think you are pretty close to having a loaded dyno with reasonable tractive effort/power output. You will probably have to "calibrate" it by running a car on another dyno and tweaking the inertia and load cell scaling if you want to get numbers that are similar to other dynos but that isn't necessary at all for it to be a pretty repeatable tuning tool.

Edit; this painful forum software doesnt like the "less-than" symbol and deleted half my post...

The "load cell" looks like an old Vane dyno, I have never seen one with friction brakes however. If its a vane it will likely have a little belt driven generator connected to one of the rollers somewhere for speed signal. To interface with most modern electronic systems it would be better to change to a strain gauge type load cell and a toothed wheel for speed

Unfortunately even with a more modern control system I dont think it would be very useful in todays world, those brake rotors will only be capable of about 50HP for a few minutes and possibly a quick load to about 100HP before overheating. It would have been fine in 1980 when most road cars where less than 100HP but today even basic motorcycles put out more than that.

A couple of lowcost software/hardware options that I know of:

Dtec Dynertia: http://www.dtec.net.au/Dynertia%20-%20Inertia%20Dynamometer%20System.htm

Yourdyno: https://yourdyno.com/

Performance Trends: http://www.performancetrends.com/dtm-dyno.htm

Thanks Adam, I was thinking that even if for some reason I can't get it to make power readings, at least I can whip out some runs on it instead of having to illegally do high speed on roads with the risk of getting caught. It's so cheap that I am going to get it anyway. I pick it up on Friday, so fingers crossed it is of some use! Some of the software links look pretty cool so happy to try them out. Let's see how I go when I pick this old girl up.

So I just picked it up and got it back to the shop. Got a better shot of the other side of the braking system and it does look like it is some very old school load measuring system, do you guys agree? I'm thinking I can re-do the setup with a new age load sensor setup as I have no idea what any of that old school stuff does and no way to access any wiring diagrams as there is no markings on it. Possibly upgrade to some high performance discs and pads on the braking system and hopefully I can get some basic and simple runs done on it. Better than nothing in the meantime I suppose!

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and it does look like it is some very old school load measuring system, do you guys agree?

Yes it is, all Vanes from that era used the same potentiometer load scale. Most of them had multiple coil springs as the reaction force however, that is the first one I have seen with a gas charged spring (shock looking thing).

You can throw away the arm with the potentiometer wiper on it and replace the gas spring with a modern S beam load cell. The S-beam will replace the role of both the spring and the potentiometer.

I wish I could find a manual or something that explains how this thing actually works. The S beam load cell sounds good but not really sure how I would mount it and from which direction to get the best readings. One other thing I'm wondering is if the braking system clamping while running is variable or only is a set amount of pressure. If it's variable, I'd have no idea of what degree of pressure it should be. This project might turn into a bit of a headache! I think the bearings at the end of the rollers are going to be easy to source considering they are numbered and stamped by Asahi so should be able to cross reference if I can't get the exact same ones. I think my only issues should be, figuring out how the braking system is originally supposed to work and how to set up the S beam load cell.

Michael, did you end up having a chance to create that spreadsheet?

I just found this in a local scrap yard. Time for a retrofit? Although second hand/used and they still want $3,300 AUD for it. Not sure if that's what they should be going for as it is the only one I can find.

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Probably more consistent and absorb higher power than the disc setup. In sayinging that a variable reg on the booster setup would allow you control. The eddy setup would probably mean you can get an off the shelf control system however. I need to update a post explaining fuel/air calculation to estimate bsfc for Leroy, if i get time on the weekend i will try to outline the process i would go through to try to estimate inertia and frictional resistance on a setup like that. Having something you can spin it up with and then decouple would be ideal. You could probably do it with a jack and a car but uou would want it strapped or locked in a frame to avoid tears.

The 'yourdyno.com' software offers complete control over the braking so I know I can control the master cylinder with a linear servo motor. I'm not sure if I should persist with this set up if I can get the bigger better heat dissipating discs, bigger calipers and high temp pads(which is still going to cost me a bit) or get rid of it and throw an eddy current retarder in it. Yourdyno can control either of them so it just depends what I want to do and especially since I want to keep this as a low cost build BUT I also want something reliable that I can actually tune others cars also. Do you think I should spend more and try and convert it, or work with that I have?

Lets be honest if you have paid VIP membership here you are probably going to want more out of it. I guess you just need to work out what different control option total costs are so you don't get any big surprises.

You're right, I want to get into the tuning game in my workshop and pass the knowledge onto my team. I might power on with the current brake set up until it's viable to upgrade.