DIY Dyno Tuning!

[RobertISaar]

EDIT by EagleMark for new thread.

i really need to move somewhere so that i can build a load cell and run engines at all times during night and day at various loads. basically, a dyno without any kind of torque measurement, but you'll be able to see the power changes through the change in speed of whatever load you have connected to the powertrain. then when done with that, go to an actual dyno for final numbers.

[EagleMark]

i really need to move somewhere so that i can build a load cell and run engines at all times during night and day at various loads. basically, a dyno without any kind of torque measurement, but you'll be able to see the power changes through the change in speed of whatever load you have connected to the powertrain. then when done with that, go to an actual dyno for final numbers.

I found one last year for $300! When I got there it was sold and being loaded. All it was, was a drivability rollers with ramps above floor, I have seen many in floor. It also had an old big box (forget what they were called?) with timing light, vacuum gauge, dwell, tach and a scope. All I wanted was the rollers! Had a big flywheel and five clutches with plates and pressure plate for load, was hand controlled by big lever so you would need someone to operate it while someone drove for load....

[RobertISaar]

was hand controlled by big lever so you would need someone to operate it while someone drove for load....

spouses make excellent lever pullers.

[gregs78cam]

i really need to move somewhere so that i can build a load cell and run engines at all times during night and day at various loads. basically, a dyno without any kind of torque measurement, but you'll be able to see the power changes through the change in speed of whatever load you have connected to the powertrain. then when done with that, go to an actual dyno for final numbers.

Not to hijack the thread, but......
I have an old 'bread van' chassis, with a rockwell rearend. I have thought about fabbing some rollers to bolt onto the hubs and using the brakes connected to master cylinder and lever.

[93V8S10]

Not to hijack the thread, but......
I have an old 'bread van' chassis, with a rockwell rearend. I have thought about fabbing some rollers to bolt onto the hubs and using the brakes connected to master cylinder and lever.

With garden hose over each hub for cooling... :)

[gregs78cam]

With garden hose over each hub for cooling... :)

I like the way you think!

[RobertISaar]

DIY dyno planning thread? or continue in here, since it would be quite relevant?

[EagleMark]

Already started new thread so we could get back to spark tuning in one and home made dyno in another...

[1project2many]

I've owned a dyno. I was given a driveability and IM testing dyno a few years back. The rollers were very small diameter and I'm sure any substantial power would have been searching for traction. Software was somehow locked to the state where the dyno came from but chances are that could have been fixed. And max HP according to manufacturer SPX was somewhere around 120. I donated it to a local and asked that if they ever get it running I be allowed from time to time to use it.

If you're in an area where old paper mills exist you might be able to find some big rollers cheap. Up and down the east coast old mills are closed down and being salvaged. A friend of mine got a couple of 24" diameter rollers for $600. He said the money didn't so much buy the rollers as pay the scrap metal guys to load 'em on a truck and deliver 'em to his place.

Upstate NY might have a few Mustang emissions dynos floating around. NY invested millions in an IM240 program that never materialized. Dynos were sold off cheap with hardly any time on them. I know of a Sunbird turbo guy that was trying to get one several years back.

Some realy smart guys on DIY once talked about building a strain gauge out of the driveshaft. Determine the modulus of elasticity for the shaft then measure how much twist can be introduced to work out torque. Calculate from there to obtain power. That conversation digressed into discussing how much twist can be introduced in a 426 Hemi block making 1000 hp (a lot, it's been measured) and nothing was ever built.

ECM can be used to measure time, rpm, delta rpm. Mass of car is known. EGT, coolant temp, oil temp can all be monitored from in cockpit or sent to laptop DAQ (heat = wasted energy). I have actually thought about writing code which can monitor performance based on a few of these values to help with tuning.

[EagleMark]

This isn't the first time I've seen a truck axle used...

[PJG1173]

thats just scarry...

[RobertISaar]

those crazy scandanavians...

anyways, while rolls would work for an interia dyno, what options are out there for a DIY static-state dyno? those would be considerably more useful for tuning spark when not at WOT.

i've seen water and oil pumps mentioned, seems reasonable, seen eddy-current mentioned as well(but need to be able to dissipate HUGE amounts of heat), not sure what else to google for.



my theory(and it could be(probably) wrong), would be that say you're "cruising" with some type of load at 1600RPM and ~50kPa, since those are beleivable numbers, and lets keep the ECM in closed loop for this, since spark changes can necessitate fuel changes as well. now to find the optimal amount of advance for a specific RPM/kPa combo (or RPM/airmass, for MAF applications), when you make a change that increases output, you'll see MAP drop due to the power required to keep the vehicle "rolling" staying the same but output has increased.

i'm sure there is something wrong with that method, but i can't put my finger on it.

i'll give an example of extreme mesaures, since it's generally easier to compare things when they are at their extremes. let's say with 20* of advance at 1600RPM and 50kPa, you're making 10HP(32.8lb-ft at that RPM). now let's add 2* of advance without changing the load. now let's say we're making 11HP at 1600/50 (36.1 lb-ft). now, since the engine is at the same speed and no gearshifts have happened and the load itself hasn't changed and throttle hasn't moved either(or IAC) (and anything else i haven't mentioned), all other things being equal, won't the change be forced to show up as a difference in manifold pressure? or will the increased power from the engine actually speed up whatever load is applied?

[EagleMark]

Couldn't you do that with say a fixed throttle so TPS % stays the same and increase spark while logging and see changes in MAP and Speed? Would require long flat straght road... could output data to spread sheet...

How else could it be done without rollers?

[RobertISaar]

those kinds of road conditions simply don't exist around here.

however, if you were to live in an area with no elevation change, little to no wind, unchanging road surface... then as long as the throttle stays perfectly still...

then you should pick up speed with more power... i think. i mean, you'll be making more power without the throttle being moved, which means you'll achieve a higher speed before wind/tire resistance prevent more acceleration(steady-state).

assuming a manual trans or a locked TCC with no slip in an automatic, RPM will also obviously rise if your vehicle speed rises. and to get back down to the speed you were at before the spark change, you would need to close the throttle slightly, which will increase vacuum (decreased MAP kPa).



maybe i'm just rambling though. but it seems like increased power will increase MPH, which will allow you to drive with less throttle, meaning more vacuum(at the same RPM), meaning less fuel required to sustain a given speed, meaning..... better MPGs.

of course, that's only looking at the MPG side of things, in the end, it's making more power using the same amount of fuel, meaning better power AND better fuel economy.


so i guess my above theory was most of the way there, but didn't properly explain WHY you would see certain changes.



in the end: if you don't move the throttle, and don't increase load, yet a change you make causes an increase in vehicle speed(or roller speed, or brake speed or whatever), that change caused more power to be generated.

[1project2many]

i'll give an example of extreme mesaures, since it's generally easier to compare things when they are at their extremes. let's say with 20* of advance at 1600RPM and 50kPa, you're making 10HP(32.8lb-ft at that RPM). now let's add 2* of advance without changing the load. now let's say we're making 11HP at 1600/50 (36.1 lb-ft). now, since the engine is at the same speed and no gearshifts have happened and the load itself hasn't changed and throttle hasn't moved either(or IAC) (and anything else i haven't mentioned), all other things being equal, won't the change be forced to show up as a difference in manifold pressure? or will the increased power from the engine actually speed up whatever load is applied?

Your cause and effect are getting tied up. Witha the preconditions above, if you make spark changes and begin to measure 11 HP, then the alter throttle angle to bring power back to 10, you'll see the expected change in MAP. But if the throttle angle doesn't change neither will MAP. You haven't altered anything on the input side of the engine, only made more power from the available fuel and air.

But you're on the right track, though. Lower MAP / throttle angles does indicate more efficient use of fuel. However there is a big consideration which goes unnoticed by most people. When MAP is low, pumping losses are greater as the piston works harder to draw air around the closed throttle. Pumping losses work against engine efficiency by requiring the engine's output to be put back into keeping the engine running. Diesels by nature are inherently more efficient as they regulate power through wide changes in fuel delivery, not by limiting airflow. A diesel intake has no throttle blade. And smaller engines for a given job are often able to be more efficient throughout a wider range as they will operate with the throttle angle open more thereby reducing pumping losses. The interpretation should be this: Don't assume the best way to maximum economy is through maximum spark advance. In some cases an engine will produce better overall efficiency with slightly less advance. This seems most common in cases where the control system is forced to run in closed loop with AFR based on O2 readings. Older systems or lean cruise / open loop cruise strategies still benefit from higher AFR and more advance.