Can someone show me their VE for idling (800-1500 rpm) (40 and 50 kpa) on a stock port t2???

 

Try this out:

rpm/map/ve

500/40/45
1000/40/45
1500/40/53

500/70/52
1000/70/54
1500/70/60

 

It's dangerous to look at VE numbers only. Fuel delivered depends on pulse width, injector size and rail pressure as well. The speed-density fueling equation is as follows:

Pulse width = req_fuel * VE * map * gammaE + injector opening time.

As you can see there are many variables besides VE that will affect fueling. I'd suggest to do a proper comparison, you should quote injector size, rail pressure (if not stock), and req_fuel setting at a minimum.

Below is a recent VE map I ran with a req_fuel value of 7.9ms, stock 4x550 injectors and stock rail pressure. The setup was on a stock 6-port 13b with TII intake, running n/a, tps-based injector staging. Note the map has dummy values above 100 kPa, as that was prior to turbo install. This map is a bit lumpy, as I was playing with auto-tune and a custom target AFR table, and ran out of nice weather. I was running around 15.5-16:1 range at low power (a little bit of surging noticed running that lean), 12:1 or so up at the high end. It ran quite nicely, certainly daily-drivable.

This VE table, or a simple scale of it, should get you driving around the block. Just stay out of the boost, as that area of the map is completely un-tuned! The zip file attachment is that same VE table in .vex format, which can be imported into MegaTune to save the typing.

I'd suggest reading this entire page prior to tuning. It'll go much smoother. http://www.megasquirt.info/v22manual/mtune.htm

Roger.

 

That's very true, but I saw no harm giving numbers at idle. That being said, we should start adding that information to our fuel maps just like you did in the attachment.

Here are the other numbers: req_fuel = 8.0, (2) 550cc primaries + (2) 720cc secondaries, stock fuel pressure, and rpm based staging at 3800 rpm. I also increased my injector opening time to 1.1 ms.

I would definitely like to see a fuel map from another turbo. I have no idea what to expect and which way the numbers are going to go. Basically I'm just expanding the envelope by driving the car and pushing it to the new parts of the map--all while keeping a close eye on the afr and egt.

Right now I'm gonna go wash my car while I still have daylight. Later I'll post with some more questions.

Scott

 

Scott,

True enough about idle. I figured you'd have read the theory on the fueling equation already. I was posting the background for the wider audience in an effort to avoid blindly quoting VE numbers only. Gotta make sure it's an apples-to-apples comparison!

Keep us up to date on the tuning!

Cheers,
Roger.

 

Oh and thanks for reminding me about the fuel rail pressure. Fortunately I have a FPR that I can easily adjust--stockers are out of luck. I just went out today and set it from 38 (stock) to 43.5 psig. Then I rescaled the ve map I have accordingly. This will give me a little more room on the duty cycle at the high end.

I thought about changing reqfuel but I'm pretty sure the reqfuel was calculated with the 43.5 psig as standard pressure for injectors--besides the ve map is still very early in tuning so no biggie.

So far I've seen little difference between TPS/rpm secondary staging. Every time I look at the TPS near staging it's usually over 90%. I moved the rpm staging point back to the normal 3800 rpm and it seemed to help--if I have enough primary injector available I may move it to 4000--we'll have to see.

Scott

 

Roger,

What is your strategy using the real low kpa part of the map. I can't believe your car idles that low unless you're at real high altitude. Mine idles about 56 kpa. On decel, the kpa goes down into the 20's--are you trying to impact decel fuel or something.

Also, why doesn't the the decel fuel cut stay on longer--mine just pops in there for a second. If I'm decelerating in gear, the kpa is way below idle, couldn't the fuel stay off till maybe 500 or so rpm above idle speed? Seems like we could save alot of fuel by doing this.

Scott

 

Just thought of another question.

Have any of you guys seen a difference between the MS rpm and the tach?

Mines reading low about 200 rpm at 4k and 300-400 rpm at 6k. I don't see any dropouts on the rpm so I think I have a good solid signal.

TIA,

Scott

 

Mine idles in the 30's at 900 rpm. It's a 6-port engine (higher compression) and a recent Mazda re-man. The lower map area I use to tune the over-run (coasting), to tune out the backfires and annoying surge when coming back onto the throttle. There are some new over-run setting in MSnSExtra, but I haven't experimented with them yet. If they work out OK, then I could toss that 20 kPa row.

The std decel fuel cut is for short duration only, as in the original coding it was based on TPS input only. With the new decel/over-run settings, I believe there are more elaborate settings than can be used.

Sounds like your dash tach is reading off a bit.

Roger.

 

yeah, on tofuball's car the dash tach is about 200 lower than the megasquirt shows.

 

got mine to idle,,,, *okay*
it like... idles 2k

 

tofuball's car idles at right around 40 KPa. It depends on what idle advance I'm using though. It's 40KPa with the idle advance set to -5, and that's idling so smooth that you can't even see the engine moving.

As we move the advance higher, the KPa number slowly drops... so at 0 deg, it's at about 39, and any higher than that it hits 38... but as I raise the advance the idle starts getting jumpy and starts misfiring. The highest I can raise the idle advance is about 3 deg BTDC before the engine starts vibrating.

renns: the fuel cut stuff works great. We have it set to come on around 25 KPa, with the TPS showing that the throttle is closed, above a CLT of 160 deg F. We have fuel set to come back on at 1200 rpms. We still have the map below 30 KPa there though because somehow tofuball is able to get below 30 KPa while still on the throttle (So fuel cut doesn't come on).