JasonC SBB

Mechanical boost climbs with RPMs.

As if this is not enough to make dyno tuning a bit more involved, the amount it climbs changes with timing. Even with closed loop boost there will be a bit of change as you change timing. Which changes where on the map the engine is walking through. And changes the torque output too....

With coarser MAP breakpoint jumps it will make things a bit easier for the tuner.

And again, this is why one should probably start with coarser RPM breakpoint jumps. If you're just interpolating between points where you dyno tune to begin with, what's the point of having the fine breakpoints at all?


When tuning a fixed MAP row, getting the dyno to do the RPM sweep allows the software to be your scratch pad. Faster.

And, an issue with part-throttle tuning where you try and adjust your foot to hit the MAP target, then reading the torque readout, is that a 3% error in hitting your MAP target, means a 3% change in torque readout. You thus cannot read torque to better than 2% accuracy and tune spark timing to within 2% of the torque value of MBT. This is why a simple TORQUE DIVIDED BY MAP calculation by the dyno software would be so damn useful. Even when you are tuning WOT, slight variations in BOOST will cause slight variations in torque. If torque divided by MAP were displayed instead of just plain torque, the small changes in boost would be mostly canceled out. Instead, you have to watch the MAP trace on the dyno screen, to make sure your boost hasn't changed more than the change in torque that you see.

JayL

iTrader: (12)

Tuning a lower horsepower car is one thing, it's more preference and can easily be done going cell by cell. What's the consensus on getting a higher horsepower car dialed in. The ability to fine tune each cell is diminished even further when your map goes out to 30# or so and you have to rely more on interpolating the cells.

Faeflora

iTrader: (2)

??? Really? That leaves you with minimal safety margin- to rely on your ait and **** tables to pull timing just enough. Also I don't think its safe to be cruising around at mbt. If you have no closed loop knock trim you can be fucked pretty quick.

JasonC SBB

JayL:

With a 300 kPa car you probably only need to tune 50 kPa jumps from 200 to 300 kPa.
If you had say these breakopints
25
50
75
100
150
200
250
300

That's only 8 MAP rows.


Fae, I suggested tuning for different CLT and AIT conditions to ensure adequate margin from ping.

And I never suggested running with no knock sensor once done tuning. Besides, it is better to never have ping, than to have it then rely on "closed loop knock" to retard it. It takes more retard to stop ping once it's started, than to prevent it to begin with. It's counter-productive. And not very reliable with the current knock sensing algorithms in aftermakret ECUs.

Asx

iTrader: (1)

what are the fan setups like on the dynos y'all go to? When tuning racecars that aren't street legal, I have to spend maybe an hour of running time dialing in the fuel map, longer if it's a dual purpose car who's owner doesn't know enough about MS to street tune his AFRs before showing up. I spend probably 4 hours of "real life" time waiting on the engine to cool down. The dynos I go to usually have a big gym fan blowing over the front of the car with a smaller squirrel cage fan blowing directly into the mouth.

Oscar

iTrader: (2)

Single, huge 5' fan that needed to be strapped down at the dyno I went to. Coolant temps were never an issue on even a stock radiator.

Faeflora

iTrader: (2)

What's wrong with interpolating?

I have been messing with my fuel map a bunch this year. The way I've done it is to do a pull at 0psi, adjust the fuel in that row to stoich (or whatever target). Multiply the stoich fuel value by 1.27 (or whatever ratio you want) and you end up with 11.5:1. Enter that at 10 psi and interpolate. For 14 psi, multiply your 0psi value by 1.27, then double your fuel value in the 14psi row. Then interpolate between those two. For 28psi, do the same as you did in the 14 psi row. Add a little to your multiplication factors and you have safety margin.

This has typically gotten me pretty damn close.

shlammed

iTrader: (8)

I like these threads when i have to start thinking about retuning my car again.

JayL

iTrader: (12)

Nothing as long as the intervals are small, it's when they start to grow that I'm concerned. You lose the precision necessary to maximize your setup while still staying safe. At what point is the interval too big?

Another aspect of tuning is how any correction factors are being setup and utilized. Everyone always talks about tuning their fuel and spark map, but how many people actually change the corrections to be ideal for their particular setup?

richyvrlimited

iTrader: (1)

Jason I'm confused, you've posted a LOT about tuning to a very fine MAP level and getting the MAP level extremely consistent when tuning, but then you've advocated a 50kpa spread between breakpoints. With that spread your relying on interpolation, which from your previous postings you implied you weren't keen of?!

Or have I not grasped your concepts?

JasonC SBB

With 25 or 50 kPa, or 800 RPM breakpoint jumps and an optimized timing, your timing may be 1* away from absolute optimal, which you might get with more breakpoints.

Off boost, you don't know if you're 5* away. Does anyone here know their 50 or 75 kPa rows' timing is correct within 5*?

And if you don't heatsoak the pistons a la Hustler or Dave Coleman, you may not know that on the main straight your 3* margin to ping may erode to -1*.

IOW having 25 kPa breakpoint jumps, introduces less error, than say, not heatsoaking your pistons.
The stuff I discussed has to do with identifying MBT. You can easily err by 2* or more if you're not consistent.

Faeflora

iTrader: (2)

By corrections do you mean AIT, CLT etc?

How would one change those to be ideal for a setup? Run a higher level of corrections if you are running more boost??

richyvrlimited

iTrader: (1)

Correction factors **** me off... MS's air density correction is based upon the ideal gas law, but it just doesn't work, you have to fudge it to get it to work, and even then I struggle to get any consitency, particularly at idle when PW's are so small.

C. Ludwig

That's why some systems include 3D, MAP based correction.

JasonC SBB

Your injector dead times are probably off.

Do a search for my thread on the datalogging method of determining dead time.

There's another issue, with saturated injectors, that the dead time changes with temperature. I'm working on a circuit solution for this now.......

JKav

iTrader: (1)

Yeah, we can get away with the drag-her-down-with-the-dyno-brake approach on the lemons car since we're relatively low output. The dyno can handle it, the fan is adequate, the engine isn't on the absolute ragged edge where it's going to instantly scatter if things aren't perfect.

Our tuning options are severely limited on the lemons car (Vortech FMU + Bipes). The dyno technique lets us fully saturate the engine with heat to allow EGTs to stabilize. This way we have some confidence that we're not going to burn an exhaust valve or crumble the stock exh manifold etc. It's an endurance race after all.

In the context of real-deal high-output Miatas (not lemons cars), reading through this thread makes it clear to me how much these engines are in need of a modern knock detection/correction system. It would go a loooong way toward saving engines, simplifying full-load tuning, improving performance, reducing EGTs...

Faeflora

iTrader: (2)

During your drag down, where did your EGTs stabilize at?

Also what are the qualities of a modern knock detection/correction system?

JasonC SBB

Fae, modern knock detection uses time-windowed "listening" (knock usually happens within a certain crank angle range after ignition) and using (sound) pattern recognition. Listen to how knock sounds, slowed down 20x - it has a very characteristic "descending bell note" sound. Simple knock detection merely listens for the presence of a certain frequency range, regardless of time windowing and the characteristic descending bell.

richyvrlimited

iTrader: (1)

There's a way of working out deadtime with the MS, flicking from sequential injection to Batch and then setting the MS to squirt 4 times per cycle, then twice every other cycle, you move the dead time until AFR's are (near) identical.

Saturated, is that High impedance or Low? There's far too many terms for 2 types of injector..

Savington

iTrader: (31)

I'm not sure what you're trying to get at here - you've mentioned the MAP vs. wtq/MAP chart before, but you just said that trying to hold a stable manifold pressure while the motor runs through the RPM range is nigh impossible. You're going to have WAY more MAP error (vs. target) than you would if you had the RPM stable and were just focused on hitting the MAP target.

Have you ever measured the torque decay of the motor on the dyno during fixed-RPM load cell tuning? Presumably it levels out at some point, or the decay drops to a point where it's fairly easily repeated. Maybe this is the ticket to consistent output measurements when you're trying to optimize a spark map?

I don't like interpolation. I use 15kpa/350rpm breakpoints. Excessive, maybe. I'll skip every other RPM column above ~5000rpm if I'm in a hurry and then fill in the blanks later.

Jay, the new AEM PnP-4 boxes are very close to true modern knock control. UA frequency filter, 2D RPM vs. noise threshold graph, windowing, etc. The only thing it won't do is the sound wave identification.