A little backstory, my challenge car is not street legal (at the moment) and while I am currently working on some things that have it in a non running state at the moment, I know that once it's running again I'm going to have to do some tuning. So I've had it on my mind to figure out how I'm going to do that without it being street legal.
So my late night theory/idea is pretty simple:
Have the car on jack stands, start it up, then brake boost it so you can test your boost limit settings, make sure it's getting the appropriate fuel, etc.
The only real potential issue I could see that causing is wear on the brakes from the extra heat and effort, but I figure if you do it in small enough doses it should be fine.
Am I missing some very good reason not to do this?
Two pretty easy to pick off risks- 1) making sure the car does not fall off whatever you have it hanging on, and 2) extracting the exhaust well enough.
Can't say that I've never used the brake road dyno in my life. For a challenge car, I would plan on replacing pretty much everything- and since they are consumable, they don't count. For sure the pads will wear, the more you run the rotors will go, too.
For base tuning, you should get a decent baseline so that you can fill data in. Plan on some conservative extrapolation.
One thing I will note- controlling your brake foot enough to get a consistent load- a load light enough to not slow the car down, I mean- is hard.
But it does bring up another idea- can this group find a way to build a DIY wheel dyno? The kind you bolt onto the drive wheels, not a chassis dyno.
wae
SuperDork
4/21/18 7:22 a.m.
alfadriver said:
One thing I will note- controlling your brake foot enough to get a consistent load- a load light enough to not slow the car down, I mean- is hard.
Without commenting on the danger level there, I can neither confirm nor deny (by which I mean I can totally confirm) that disconnecting and capping the vacuum line to the brake booster makes it much easier to modulate brake pressure.
wae said:
alfadriver said:
One thing I will note- controlling your brake foot enough to get a consistent load- a load light enough to not slow the car down, I mean- is hard.
Without commenting on the danger level there, I can neither confirm nor deny (by which I mean I can totally confirm) that disconnecting and capping the vacuum line to the brake booster makes it much easier to modulate brake pressure.
Very good (admitting, non committal) idea.
Robbie
PowerDork
4/21/18 8:49 a.m.
How about using an abs pump and an Arduino and maybe some water baths for the bottom half of the calipers? Have the arduino track wheel speed and apply more brake to slow them down or less to speed them up? Basically you just want to set and hold speed right?
Just take the wheels off, hook up the tester and bleed the brakes, place the water baths, and go!
My local podunk 1/8th mile dragway has $14 run-whatcha-brung / hot import nights on Thursdays. Line up and run all you want.
That's a great place to tune. Look at data, adjust, run, look at data, etc. Other than a way to log (tunable ECU, WB, laptop,) you can get a lot of data from your 1/8th mile results.
If you REALLY want to poor man tune for just WOT, you at least get a timeslip after each run.
alfadriver said:
But it does bring up another idea- can this group find a way to build a DIY wheel dyno? The kind you bolt onto the drive wheels, not a chassis dyno.
Fujioko built an engine dyno, the same concept could work on a wheel dyno:
https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/fujioko-builds-a-low-buck-engine-dyno/87005/page1/
