LetsGetThisDone

iTrader: (1)

The point of having the trim's off when tuning is to be able to more quickly dial in the base map, without having the trims effect your adjustments. You just look at the wideband and make adjustments based on that. Last my car was tuned from a base map, it was completely in open loop the first 2-3 ROM revisions.

2winscroll

You my friend know absolutely nothing about tuning, and should refrain from commenting.

2winscroll

Fuel trims exist because of differences in the specific gravity of fuel more or less.

LetsGetThisDone

iTrader: (1)

And variances in engines in a mass production environment where each one isn't getting a "custom" tune, and they will all vary a bit.

silverflyer

The lean misfire scenario is an interesting one. The car was much richer months ago when we started with the base rom though (about 10.8 AFR). I fixed a leak in the throttle seals and we leaned the car out. It's now sitting at an average of 13.2 AFR. The car mostly runs smooth though. Maybe the occasional burble here or there, but it's on S2 cams.

The car is running open loop. No fuel trims.

silverflyer

Here are some videos:

Base tune (first start) startup from back in April 10.8 AFR

Here is one from June. 13.2 AFR

I didn't take a video since drilling out the siphon. I will post some more up to date videos when I can.

2winscroll

My bad a lean misfire will cause you afr readings to go leaner. Sorry I got that mixed up.

What happens if you try to lean it out more? Do AFR's start to get unstable?

RightSaid fred

You actually got that all back to front.

Increased fuel pressure makes the injectors slower to open.
That's because they open against fuel pressure.
Because increased pressure makes them slower to open (actual PW is less than commanded PW), you need to adjust the dead time so they open longer........but only at low load, which of course you can't do.
But not only that, the minimum usable PW is also greater, so your minimum idle speed is a bit more, otherwise it'll stall due to injectors not able to open with the required short PWs.


Obviously by giving out false info.........you're NOT a tuner. Just another wannabe.

mines5

Can you post a log of this actual or close enough scenario that you explained ?

2winscroll

Wholly crap batman! Your right about latency needing to be higher with increased fuel pressure. What I was trying to say is the bounce, non linear crazy reaction your injectors have at low pulse widths, can be more pronounced when fuel pressure drops. He is operating right at the edge of the minimum pulse width of the injectors, then a drop in pressure at the rail can put him right on the bounce of the injectors, then yes he could actually go rich from a drop in fuel pressure.

Not trying to give out false info sorry but you do the **** all the time.

Not a tuner? How many cars have you tuned over 800hp? Over 500hp? Over 350hp?
Let me help you out..none...none....none.

Biggiesacks

fuel pressure is love, fuel pressure is life.

mines5

What is the purpose of posting information which you can't back up or atleast present a sample with proper example.

If information is correct but has ambiguity , how one can understand that ?

2winscroll

Ok watch the second video.
The AFR's are pretty solid. Flyer has told me that if he tries to lean out the idle any further AFR's start to jump around. Crazy variation all over the place. This tells me that he's starting to run at the very minimum IPW the injectors can run at. 1650's on gas with the siphon drilled 14:1 is about as good as it gets unless you drop your idle timing way down to load the engine more. The only time I would bother doing that was if I was going to run in closed loop so I could get the car to idle at 14.7. Race vehicles run all the time with an idle richer than that. With no catalytic converter it's just fine, and will run cooler at idle. Pulling timing to get the AFR's leaner will not save you any fuel because the motor is just running less efficient and requires more fuel, that's why you are able to get it to idle at a higher A/F ratio.

IMO the idle tune is very close. But please if you are an experienced tuner chime in and tell the Flyer your opinions.

Cheers, 2win

LetsGetThisDone

iTrader: (1)

I'd have to see what my timing at idle is, but my car idles fine at stoich, in both open and closed loop, on pump gas. I don't have my lap top with me at work. IIRC its 8*. Too much temperature swing here in Vegas (can be as much as 40* in a 24hr period between night/day/night), and I take the car out of town a lot, so I didn't want to do deal with an open loop idle and inconsistent AFR. So, I'm not sure what you mean by "way" down. My car also hasn't run pump gas in over 2 years, so it makes it hard to remember little things like idle timing

RightSaid fred

Not sure what you mean by that?
If you're wondering about data from fuel pressure vs opening times, closing times vs flow vs minimum usable PW then you get your own data from doing an injector flow test on an injector test bench.


If you don't have one, they're very easy to make yourself.....like mine.

Then you've got more of an idea as to what's going on.
Unlike others here who have an opinion and nothing else.