Engine...theory
 

Hey guys,

I'm trying to make a bit more sense of the data I'm getting from my ecu. Can someone explain to me the difference between the following. How does this affect power being made. And how does one or the other affect detonation? Would 100% TPS create more detonation? Does the cylinder take in more volume and the cylinder pressure increases? Is cylinder pressure directly related to manifold pressure? I'm talking strictly about calculations based off of MAP and RPM in terms of fueling and ignition angles.

160kpa at 4500rpm @ 50% throttle
160kpa at 4500rpm @ 100% throttle


Thanks.

Theoretically there is no difference, it's the same load.

One would be made going up a grade, or with more weight in the car (50% throttle), while the other is on level ground, or at that rpm, the 50% could be transient boost response, eg: punching it from 4250, and boost building to target.

You tune your fuel map and advance tables the same way, since those are your axes. Let your accel enrichments use the TPS to determine when to richen it up.

In reality there will be some flow differences, but in the terms of a speed density calculation it doesn't come into play, and you can only build as much load as restrictions allow.

So there will be no rise in cylinder pressure if I go from 50% TPS to 100% TPS? Any idea how doing a full 100% TPS run is showing signs of knock, and 50% TPS run shows no knock? I take it to the same RPM. This is based of my logged data. I can't hear ping, but I don't know if I'm experienced enough to hear slight knock. I do have signs of it on my plugs...I think. They were clean before I started the 100% TPS runs (specs on porcelain). Thanks for the info.

http://img683.imageshack.us/img683/4210/22926387.jpg

It's the exact same load on the motor...same density air, flowing at the same speed. The load is just built in different situations. I imagine that at 100% throttle you would be in that cell for a very short time, whereas you can be there longer in a passing situation at 50% throttle.

Once opened enough to build that level of load, the position of the throttle body in relation to mass flow rate is no different than adjusting the size of your intercooler piping. This of course assumes steady state.

Thanks for clearing it up. Yeah, I'm also leaning on the possibility that I may not be reducing timing fast enough, but I still can't comprehend why it's giving me different results in the conditions above.

Since you have an '01, it's possible that intake valve timing may be different (I honestly don't know if that's TPS-related or not in the Adaptronic) which would change VE, and make cylinder fill not the same for a constant MAP.

It's also possible that your AFR may be different. Again, no idea how your ECU is set up here.

^ Damn good point.

VE plays into that speed density equation, well, hell, that's why it's called a VE table.

I forgot about VVT...damn, now this is where my brain temps start rising....

4000-4500rpm is where my VVT duty cylcle is at it's peak. I don't believe the Adaptronic uses TPS as a variable to get it's VVT angle. I only have it set to target based off RPM only.

Since it is based off RPM, wouldn't the VVT not affect the VE since I have the same MAP reading?

Do I start changing ignition timing in this case, or should I be looking at other things now?

I'm trying to keep up here, thanks.

Ok guys, don't hurt me for being a TINY bit off with my data, but these are my values.

100% TPS, 13* BTDC, 4500 RPM, 160kpa
50% TPS, 14.6* BTDC, 4320 RPM, 152kpa

Are these far off enough to be the difference between knock and no knock? I'm getting around 80-100 instances of knock after my noise filter? I'll do a lot more runs today so I can get a lot more data to make my head explode faster.

I have typically noticed that you can get knock building boost at partial throttle, more so than full throttle because the TPS can effect the ignition timing, sometimes dramatically so.
Partial throttle N/A = less load = more ignition advance.
But then you add boost and youre able to hit full boost at partial throttle, which the factory ECU isnt setup to deal with.

dgmorr,
Did you set your knock offset specifically to your miata or did you just use someone elses values? If you just used someone elses values, could it be that your not detonating?

Based on my logs, the stock ECU doesn't use TPS, just load and RPM.

The adaptronic uses RPM only unless you sacrifice a spare fuel or spark map.