turbo: tunning for anti-lag by retarding timing?

[elaw]

Staged turbochargers...

[rickb794]

A little shot of goofy gas is looking better and better.
Push button on the shifter and a wot switch.
Push the button, mash the throttle, and let off the button when boost comes up.

A water(/methanol) spray system is a huge plus.

[elaw]

I've actually got to disagree on the w/m injection - I'm talking about a system that sprays into the intake, not one that sprays the outside of an intercooler or something like that.

I spent quite a bit of time fooling around with w/m injection and while it allowed much higher boost levels, I never found it reduced lag. The only direct effect on power I ever noticed is a slight reduction in power when the w/m kicked in if it was injecting too much. That's what happened with my initial setup which was just on/off via a pressure switch. I added a valve to meter the water depending on boost pressure and it fixed that problem.

[bradyzq]

Hi,

A few comments, first about the spinning of tires. Hadn't heard that one, but what do they do in winter? You can spin them on the spot, spin them while sliding backwards, all sorts of things. What a load of crap...... sigh. Just like the "broomstick" rule.

For your turbo, you're basically deciding where you would like your torque (acceleration at a given RPM) when you choose your hotside housing and wheel. You may be stuck with boost onset where it is with your setup, assuming it's dialed in. Is it? You mention in your sig that you're improving the tune one cell at a time.

Not that I want you to blow your engine, but if your engine is stock, it's about 7.4:1 compression IIRC. You can probably throw a lot of timing at it off boost. That will improve the feel of the car before boost onset.

[Supernova_6969]

hi!

the whole spinning tires is more if you spin your tires on dry, clean asphalt for more than a chirp cause you slipped the clutch.. it's meant to stop people from doing smoke shows and 11s on purpose..

what do you mean is it dialed in?

the engine was rebuilt with higher than stock, but not crazy high compression. problem is, the guy who built it didn't remember exactly what the compression ratio was, so i'm stuck playing it by ear.

I do plan on eventually getting it on a dyno once I fix a bunch of other little problems.. then, I'll probably be able to do as you suggest. in the meantime, without a ping detector of wired cans bolted to the engine, i'll stick with something safe.

[bradyzq]

By "dialed in" I mean correctly tuned. A T3/T4 will most likely never spool up at 2000RPM on a 2.8, but the car may still pull pretty well off boost if it's tuned right.

Does the car still have the stock knock sensor?

[Supernova_6969]

Bradyzq....

oh!
no, it's far from being properly tuned. the long story is I bought the guy from a guy who told me "all I needed to do was tune it and it would be perfect". His story is that he swaped engine from an old old 280zx to a newer 280zx, then from that car to the current one (body is near perfect). he changed the turbo, and tuned it on a dyno till it was factory-smooth. If that was it, great, but then he decided he wanted to go for big power, tore the engine apart and rebuilt everything (although, for some reason, nothing is forged, so I don't quite get it). The new pistons were less domes than stock, so that changed the compression ratio to get a bit more low end torque...

all that done, he slapped it back together, flashed his same pre-rebuild tune and found that it didn't work any more with the new specs; he then opened the tables, made it super rich in some places (to prevent knock) and leaned out where it was rich, then parked the car for about a year while he worked on other stuff and finally sold it to me. I've been slowly leaning out the super rich spots (O would hit 10:1, and sometimes even 9:1) on WOT/boost) and richened some spots that got as high as 16-17:1. I've got a car that's around 14:1 when cruising and I'm still working on mid 11:1 under load.

I haven't touched the timing yet cause that's something I don't understand as much as AFR AND because as far as I know, there isn't a knock sensor on the car. that's something that I wanted to work out at a speed shop on a dyno, with experts with me, although I have to figure out alternator problem and something that feels like misfires before I get that far.

so, lesson of the story, don't trust a guy who tells you the engine just needs to be tuned, unless you know everything there is to know about it, which is not my case. Or that you know people that know how to tune a car with a megasquirt. and it turns out i'm the expert in my circle or friends, which isn't all that much..

I see that you have (had?) a 240z yourself.. what's your set up?

[bradyzq]

Mine's still an L24, with triple Webers. It's a mystery L24 though. I bought it thinking it was an L28, because it came out of a 280Z (I was told), had the fuel injection on it, and an N47 head, but I noticed it was an L24???? But it doesn't seem to be out of a Maxima either... Anyways, price was very right and it ran well, so I didn't complain.

The car has been sitting for awhile at the shop, with an old Electromotive programmable ignition sitting on the passenger seat waiting for me to install and tune it (with a screwdriver!)

With the wideband integrated into the MS2, you should be able to autotune it safely off boost, then see if your VE makes sense at all in boost. Sounds like you have been doing something like this already though!

For timing, if you have a somewhat normal engine, you should be safe with 35 degrees at 100kpa (0 psi boost), pulling 2 degrees (2.5 if you're really conservative) for every 10kpa above that, low RPM and ramp up to 35 degrees notwithstanding. Does this sound at all like your timing map? Of course, this is assuming your MS2 is correctly sync'd to the engine (actual timing is equal to timing displayed in Tunerstudio).

[bradyzq]

Oh, and by the way, no stock Z pistons were domed. Either flat-topped or dished. From the sound of it, unless his story is all BS, he swapped out the dished pistons for flat-topped ones to bump the compression a bit, and get better torque. That's fine if the head is from a 280ZX (turbo or non). If it's off an earlier Z, you may be running too high a compression ratio.

[Supernova_6969]

Oh yeah i meant dished. He went from dished to either less dished or flat....

As for the map, i'll have to check the timming and maybe tweak it to your suggestions, which seem to match what i've been reading... I've got alternator/charging problems right now and so i' not using the car. I'm hopping to fix it and use it a few more time before winter.

As for the auto tune i was looking into it except that the previous owner had not hooked the wideband into the ms2, only to a gage so i had to adjust everything on the fly by keeping an eye on the gauge, another on the road and a third eye on the computer/tablet (i'm certain you see the problem there) I did hook it up to the ms2 but couldnt get the O2 values in the ms2 to match the ones from the gauge in the car. I have too look into that...

I' keep you posted. See if playing with the timming does something to belp out a little, maybe...

Thanks for the suggestions..

[Supernova_6969]

so I took a look at my msq and my spark table is far from as aggressive as you suggested.. I think.. here..

spark advance table.jpg

[bradyzq]

Yeah, it looks like it wants more timing. Try it only off boost (100kpa and lower) first, to see if it wakes up the car. Funny: my "guesstimate" for timing works out to the same numbers at 200kpa, but more elsewhere. How much boost are you running?

Do you know if the timing is correctly sync'd?

What's your crank trigger setup?

BTW, when you're ready to get it on a dyno, let me know.