VQ 304 - Cheap Street Fasts

[[tuffvq]]

OK so I had a bit more of a play tonight. Still don't have my wideband hooked into the ECU, however I do have the gauge readout on the innovate so at least I have some information available.
(Any tips on an easy place to grab an extra loom connector pin for this purpose?). My aim was to better understand the idle sequence, so these posts are only about the car's idle.

It seems as though I have an 'underdamped' feedback loop on cold idle. When some (unknown to me) parameter falls low enough, the engine falls into a decaying RPM cycle which eventualy causes a stall. It's predictable and I can save it with a very small blip of the throttle, but something I'd like to fix.

Once up near operating temp, I'm comfortable that the 20-100kPa VE table is having some impact, as when I updated this table at idle from ~45% VE down to 37% in the traced idle region when the coolant temp was around 75-80*C, I was able to drop AFRs from 11.8-12.4 to mid 13's. However, when I made changes to the EST table (quite large ones) there appeared to be no changes to the logged spark advance, or the 'attitude' of the engine that I could feel or hear.

I have some logs that I'll post shortly.

Any thoughts?

[[tuffvq]]

Forgot to add, running the following:
OSE $12P V112 BLCF V8.bin
OSE12P V112 - 1,2 and 3 bar.xdf
OSE_$12PV112_1BAR - Petrol with calcVE.adx

One thing I'm really happy with is that with some (blind) tweaks, I've managed to get the hot idle (untouched TPS) down to 750rpm target. It sounds much better than the 1000rpm it used to do on the old mail order tune, however I think most of this is due to playing with the throttles rather than my tuning prowess...

[Dylan]

Good to see you ripping into ome changes it's good fun. After a determined idle period it goes to the idle spark table. So adjusting the main spark tabe will not see any commanded changes when in closed loop idle. Watch in real time on the dash screen the indicator will go green for closed loop idle.

Aim for 13.8 afr, 10 iac steps and 26 degree advance once coolant is at least 70 degrees plus.
Before setting the VE figures make sure you have the target afr where you want it.

[immortality]

I'm with Dylan, get the idle speed right with only a few IAC steps, that way it limits how much the IAC stepper motor can drop the idle.

You need to get the main VE table and idle table settings the same so as the ECU moves between the tables there aren't large changes in commanded values leading to unstable conditions.

[[tuffvq]]

Thanks for the tips guys - I'll have a crack tonight and see how I go!

[[tuffvq]]

OK so I took the advice above and played around a bit more, managed to reduce the timing variability at idle so it now sits on more or less 26 deg. AFR is down to about mid 13's when warm. IAC, however, sits on 0 steps. I think this is to do with the twin throttle arrangement.
In any case it seems quite stable while stationary now. It had one anomaly where it picked up the idle to 1200rpm and then stalled. I couldn't see any reason why this happened. Log attached.

Next step was to try and smooth out the timing map. I've made up something similar to the below, however only started the car to see it would at least work initially. Haven't taken it for a drive yet as it was too late in the night and I haven't worked on the VE table either.

Thoughts on the timing map? I don't usually spin this past 6,200rpm.

20 30 40 50 60 70 80 85 90 95 100
400 20.04 20.04 23.91 23.91 23.91 23.91 23.91 22.15 22.15 20.04 20.04
800 28.83 29.18 26.02 26.02 26.02 23.91 23.91 22.15 22.15 21.09 20.04
1200 31.99 31.99 28.13 27.07 28.13 27.07 26.02 23.91 22.85 20.04 20.04
1600 28.13 30.94 28.13 31.64 28.83 28.13 27.07 26.02 24.96 22.15 20.04
2000 20.04 31.64 30.94 35.16 29.88 30.94 29.88 28.13 26.02 24.96 22.15
2400 20.04 29.88 35.16 35.16 31.99 31.99 27.07 28.13 27.07 28.13 28.13
2800 20.04 27.07 35.16 35.16 31.99 31.99 27.07 28.13 28.83 28.83 28.83
3200 20.04 28.13 35.16 35.16 30.94 29.88 28.13 28.13 29.88 29.88 29.88
3600 20.04 26.02 35.16 35.16 27.07 27.07 28.83 29.88 30.94 30.94 30.94
4000 20.04 28.13 35.16 34.1 29.88 28.83 29.88 31.99 31.99 31.99 31.99
4400 20.04 29.88 31.99 35.86 29.88 29.88 30.94 31.99 32.34 32.34 32.34
4800 20.04 31.99 29.88 36.91 30.94 30.59 31.99 32.34 33.05 33.05 33.05
5200 20.04 31.99 28.13 36.91 30.94 30.94 31.99 33.05 33.4 33.4 33.4
5600 20.04 31.99 28.13 36.91 30.94 30.94 31.99 33.05 34.1 34.1 34.1
6000 20.04 31.99 28.13 36.91 30.94 30.94 31.99 33.05 34.1 34.1 34.1
6400 20.04 31.99 28.13 36.91 30.94 30.94 31.99 31.99 34.1 34.1 34.1
6800 20.04 31.99 28.13 36.91 30.94 26.02 24.96 24.96 27.07 24.96 24.96

Also, any other tips for the VE table?

[[tuffvq]]

OK so that's clearly unreadable

Try a PDF instead...

[immortality]

I might be easier to just post a screen shot of the timing map

I'd suggest that timing map has to much timing for a VN headed engine, the early style heads liked more timing like this map. I'd suggest 90, 95 and 100 map about 28 degrees max from 3000rpm up and then maybe sneak in another 1 degree for every 1000rpm from 4500 rpm up.

Either way, start with a little timing and then add a little in and see how it goes. Do you have a working knock sensor?

As a guide, look at what the likes of TK and HPE Pete (AV8 forum) are using on there built engines with just a simple dizzy, carb setup. On good engines you'll initial timing in the teens and see a max of 26-28° total timing, you want something similar in the 90 - 100 map areas. Been that you have less comp it will probably take a little more timing because it's a lower comp engine with only a small cam but you need to work up to it rather than throw a whole lot of timing into it and pop a head gasket (or worse). Best bet also is to get the AFR's where they need to be, a lean AFR will burn faster than a rich AFR with the same timing.

[Dylan]

Post up a matching bin for that log

[[tuffvq]]

Cool thanks for the heads up. I'd been reading elsewhere that 33-34 was the way to go.
I'm a little 'gung ho' with this engine as I've got 11-ty spare rods, pistons and cranks in the shed, and I'm only trying to learn to tune on this engine so I can swap the cam, bump up compression etc.
I'll offset the map by a couple of degrees down and try that.