The Tuning Talk Thread - Forced Induction EFI & JZ Tuning.

[OnAll-FOUR]

Okay that makes more sense. I think I was getting the pre ignition and self ignition mixed up.

Otherwise the by products left after a burn make sense.

[RyleyMA61]

how have people gone with cold starting?

mine takes aaaaaaaaaaaaages to turn over when stone cold.... ie 30 secs or cranking.

what have you done or fiddled with in order to get it nicer?

[oldcorollas]

MS has
1. cranking pulsewidth. that should be high enough to get it to kick over at all times.
2. afterstart enrichment for X number of cycles (like.. 20 or 30% enrichment for 200 cycles)
3. then there is cold temp enrichment....

1 is used onyl when cranking... sounds like you might need to up that?

[thechuckster]

suggestion (if you have a wideband sensor):
-take laptop to car and plug in
-turn ignition on to prime pump and get WB sensor heating (assuming you have it wired up to IGN not a running-only circuit)
-boot up laptop
-when WB is up to temp (~30 sec), start datalogging
-try to start car

Hopefully you'll get some vaguely useful AFR data once the motor starts and catches up. You'll also log some warm-up temps and PW data so you can edit the afterstart enrichment values.

Cranking pulsewidth was fairly easy for me: start eye-wateringly rich, take out fuel until starting was no longer easy then back off. Timing is always locked to 12 BTDC (during cranking) until >300rpm then follow the usual Ign map. While tuning this, you should get a few decent pops/bangs out the exhaust. Keeping the Ign timing locked reduces likelihood of a backfire and makes it easier for engine to catch.

Do the tuning on a cold night.

I did set the ECU to not fire for at least 3 revolutions to get the oil pump doing a bit of work priming itself and getting oil moving around. Anymore and you start to risk flooding or fuel pooling in the intake.

[JZA70 R]

I tuned cold start (cranking) using pulse width (cranking fuelling). Once I got it to start nice I then fine tuned enrichment VS temperature.

tuning cold start is tedious and annoying if you dont get it right quick. and needs to be fine tuned all year round (for at least a year) (only if you're anal like me i guess :S) to make sure the car starts, runs and drives well in all weather conditions.

Its one aspect of tuning that I never got 100% with my power fc, but it wasnt bad. Ive seen a certain supra start up in 15'c and once it started choofed black smoke out until it was near operating temp. Thats one way to waste fuel, kill your cylinder bores, kill spark plugs and make a BIG mess behind your car on the drive way. Not cool.

[JZA70 R]

For those that are interested in why it requires more fuel to start and run your car, here is my basic understanding of it. I hope I’m not too miss-informed.

Obviously when you start your car your engine is cool, which means your head and intake ports and valves are cool too. When fuel is injected into the intake port, the cool walls and valves absorb and condense the fuel particles, and instead of staying airborne or evaporating into fuel vapour, the fuel particles stick to the valve or wall and are not ignited.

So by increasing the amount of fuel you inject into the motor, you are increasing the odds of those fuel particles remaining airborne and hence being ignited.

In theory when logging AFR's during cold start you should still aim for your target AFR's as you would when the engine is at operating temperature because as i said before, you are injecting more fuel to increase the odds of a normal burn in the cylinder. Despite the fact a significant percentage of injected fuel is in fact wasted as unburnt fuel and hence not picked up by your oxygen sensor.

[JP]

with my vipec ecu I have pre-crank prime enabled to wet the cylinder walls before starting, helps a lot with a cold engine in my experience. I'm still working on my 2J cold start as it fires after 3 cranks, my forester wtih built 2.5L setup fires after 1 crank no matter what the temperature is.

I've found that increased dwell time during cranking helps along with making sure your injector timing at low RPM is set correctly. I also work with adjusting the fuel map cells in the cranking area of the map first, then adjusting the first crank enrichment, crank enrichment, post start enrichment and warm-up enrichment in that order.

[thechuckster]

just to add to the use of AFR data in tuning startup and post-startup - any misses are going to read as lean so if you start pouring in more fuel to rectify lean events, make sure you're not compounding an over-rich issue.

[Jabtronic]

Could you guys please check out my ignition timing table and tell me if there's anything I should change? (Engine is a single turbo 1JZ)
I'm about to start tuning my AFR's more seriously but am worried about the timing as it looks a bit messy (it's from a mates tune). The timing isn't something I want to be mucking around with so I'd rather be running conservative values that are reasonably safe. Obviously that 3x4 grid of 8 degree fields isn't right. Any suggestions?

[JP]

from that map I'm guessing the ISCV isn't being used, the throttle stopper has been opened up and the ignition timing is being used to control idle speed.

The timing looks to be fairly aggressive for a base map, I'm guessing it's from one of Matty Spry's JZ tunes? Make sure you use some det cans if you're trying to street tune the fuel on that.

[thechuckster]

could also do with some more MAP rows in the sub 100kpa range - appears to be tuned for mostly on-boost regions thus daily drivability might be a challenge.

[JZA70 R]

What am I missing here? ...The load scale is from 0kPa to 250kPa and I thought 0kPa was 0psi and 250kPa was 36psi???

[RA35GT]

Its likely in absolute figures.

i.e. 0 kPa is -14.7PSI (Full vacuum) and 250kPa would be 21ish PSI.

[thechuckster]

what they said: 100kpa = 0psi

edit: that's a bit misleading.

0kpa = absolute vacuum
100 kpa = atmo (at sea level referenced to a specific temp... if you want to get highly technical)

so a MAP sensor that say's it's 250kpa will max out at 21psi.

also, there's two ways of expressing psi - gauge psi (where 0psi is atmo) and an absolute measure (where atmo is 14.7psi). I prefer kpa as many older engine maps/specs talk about vacuum in mm/Hg or in/Hg which is even more confusing.

[JP]

yep, adaptronic's have the MAP load scale in kPa which is absolute. You also can't define your own load points with the E420C.