djamps

iTrader: (1)

My fuel table is almost completely zero'd out +/- 5%. Did all the fueling by MAF table. Never really messed with K except for the very first startup to get it to stay running.

tcode

iTrader: (7)

Here's an idea. Since most of the SC intake piping is 2.5", I could replace 3" MAF sensor pipe with 2.5" one (a bit of welding, not a big deal). That way idle MAF voltage should move above 1V I believe. Of course, will lose PMAS HPX 1k HP measuring ability, but I don't plan to go over 500HP. What do you think?

djamps

iTrader: (1)

I don't think it'll help. The whole MAF transfer function is different its not just a linear change from the stock MAF. Changing the pipe size would be like changing K and nothing else.

tcode

iTrader: (7)

You might be right, but going to the larger diameter (such as 4") and your idle will suffer 101%.
"The PMAS Maf works great in a 3" tube for up to around 650-700 rwhp. A 3.5" tube will support 800+hp.� Larger tubes will support even more hp, but you will loose some resolution at the idle range of the maf and it can potentially cause issues."

Now, going to the opposite direction, with smaller diameter tube, should help with idle. Again, I might be wrong but can't resist to try.

tcode

iTrader: (7)

Okay, everything went well and quite easy with PMAS. It works charming. I'm hitting 3.96V @6300 rpm, so there's enough headroom for colder days. However, my fuel system is now maxed. DW600 Injectors are almost on WOT hahaha . Having them with Walbro 255lph pump in fuel tank basket (CJM mod).

For SC people, has anyone tried advancing intake cams in earlier stage? There's a plenty of torque to pick up on lower rpms and load according to my butt dyno .

tcode

iTrader: (7)

Having a question for UpRev gurus .

Situation No1, partial throttle:

If it isn't readable from the pic, those are relevant variables:
RPM: 3488
MAF Voltage: 2.68V
BFSC: 13.44
Target AFR: 13.44
AFR B1: 12.82
AFR B2: 12.99
Inj duty: 18.7%

And that's absolutely fine, bc aimed AFR 13 at partial throttle&light load.

Situation No2, wide open throttle:

Again relevant parameters in this case:
RPM: 3575
MAF Voltage: 2.69V
BFSC: 13.55
Target AFR: 11.76
AFR B1: 11.8
AFR B2: 11.71
Inj duty: 21%


In 2nd case (WOT) it seems that ECU wants AFR 11.76 and adding fuel like mad to get there. Almost same RPM, MAF Voltage and BFSC in both cases, but way different AFR. Of course, I don't want it that rich, but can't figure out what to do. If I lean AFR on my MAF table to be perfect on WOT, it will be too lean on partial throttle.

Epstein

iTrader: (5)

Adjust it on the fuel map. That's what it's for.

tcode

iTrader: (7)

It won't work, because there are same rpm vs BFSC points in both cases.

Epstein

iTrader: (5)

If they are the same RPM and BFS points in both cases, why are there 2 different target AFR numbers? What does your target AFR map look like?

tcode

iTrader: (7)

That's a good question. It seems that ECU changes Afr target to 11.7 at WOT. However, there's no Afr correction so it's in open loop. But still adding fuel. Will post my Afr target table later, once get home.

T_K

iTrader: (5)

BFS doesn't seem to correspond perfectly with fuel targets at WOT, it feels like it might just target the last column exclusively under WOT.

I have HR with gen3 ECU so I don't know how similar or dissimilar they would be. In my logs, pretty much under WOT, it targets the last column regardless of BFS value.

tcode

iTrader: (7)

Thanks for the tip. I'll try adjust fueling with that last column.

Epstein

iTrader: (5)

The more things change, the more they stay the same. This is the same way Nissan's NA ECUs from 20 years ago work. As soon as the TPS exceeds a certain value it jumps to the last column. Of course, this value was known and could be adjusted. I had more control over KA and SR ROM tunes 5 years ago than I do over my Uprev right now.

T_K

iTrader: (5)

When we log "ignition timing" what's the actual units for the parameter?

The value doesn't seem to match up quite right with the ignition timing tables.

djamps

iTrader: (1)

That's why I adjust fueling almost exclusively with the MAF table. Eliminated many problems (most notably timing instability on hard upshifts) that way.

balaguru

iTrader: (2)

Something doesn't add up. Why are you seeing the same MAF voltage at part throttle and WOT at the same RPM? One would think you're flowing more air at WOT and should see a higher voltage. BTW, are target AFR even used at WOT? Like djamps I adjust fueling with the MAF table for both open and closed loop. I set the fuel targets so that I can calc corrections or use the ecu corrections when I adjust the maf table.

It's degrees BTDC. Time timing values in the timing table are burn times and represent the amount of time it takes for cylinders to reach peak pressure after ignition.

T_K

iTrader: (5)

Conditions change under WOT, and since we can't be sure of what the exact conditions are, the best way so far has been to use either TPS or Accel Pedal voltages.

A BFS value high enough should take you to the last fuel column, but WOT conditions automatically jumps there despite the current BFS value. This throws the fuel tracer off since it follows BFS and RPM.

Is the burn time represented in milliseconds or microseconds? Whatever the time unit is, if we make the assumption that peak pressures are reached around 15 degrees ATDC, it should be trivial to convert the burn time table to degree values.

djamps

iTrader: (1)

Don't think a conversion is that easy. More variables are involved such as amount of fuel delivered which is basically an unknown since it depends on so many conditions.

T_K

iTrader: (5)

I'm not sure I'm following. Engine RPM is the angular velocity and is independent of what's present in the chamber. Burn rate only matters on the amount of air and the fuel ratio and that can be taken to be more or less constant.

The burn time values in the table are too short for a given angular velocity. The engine doesn't cover enough degrees to match up with the burn time values when taking into consideration the actual ignition advance values. The timing values look to be in microseconds, if the constant multiplier is taken to be unitless.

Mostly I've been trying to see at what degree values ATDC that Nissan determined as a good set point for peak cylinder pressures. From 3000RPM onwards, the exhaust cam is set around 15-20 degrees. From 3600-4600 it hits 20 degrees, but stays at 15 throughout. The intake cam goes from 40 degrees advanced to 0 as it approaches redline. Since the exhaust cam only had small variation I chose to temporarily ignore its variance.

Anyway, when intake cam is at zero advance, the ATDC value collapses towards ~22 degrees, keeping in mind the exhaust cam is also dialed in at 15 degrees. The trend so far is more intake cam advance requires more timing advance.

djamps

iTrader: (1)

Air to fuel ratio has to be a known condition to calculate the degrees timing from burn time. This is unknown when you're plugging burn time values in open loop tables. Maybe if the ECU is making timing calcs in open loop based on the target A/F then uprev might be able to code in some conversions but I doubt it's that simple based on my years of fighting timing gremlins. Nothing is just 'simple' in these ECU's. There's so many temp and other compensation tables that we have no access to. But the fact of the matter is that nissan never intended for fixed timing and we're kind of screwed in that department.