momostallion

iTrader: (1)

I have a 2012 gsr with a grimmspeed 3 port, test pipe + cat back. I am working on building up my boost curve slowly after installing the 3 port. I've made it up to 23/24 psi peak at 4000 rpm then tapering to 17 psi by 7000 rpm. I'm almost happy with this flash but I wont move on until I understand one bad spot on this "tune".

After datalogging a couple of runs on this setup, my AFR (both commanded and measured via wideband) look to be a point higher than I have programmed in via the high octane fuel map in the 4000-5000 rpm range.
From reading a bunch of posts, I know the high octane fuel map doesn't translate 1:1 but it was very close on stock boost levels and it's still very close in the upper rpm range so I don't quite get the disparity in this 1000 rpm segment during peak boost.

I am just trying to figure out if there is some other correction that I might be missing out on. ie, do I need to tweak the calibration fuel map or the maf tables?


Here are the relevant columns from my evoscan datalog along with what i typed in from my high octane fuel map numbers in red and the variance. you can see the uego numbers come down into the mid 11s by 5000 rpm despite AFRMAP being low 12s.

RPM	Load	AFRMAP	UEGORearO2AFR	high octane fuel map	variance
3500	136	12.98	13.26	12.7	+0.28
3625	180	12.63	13.21
3785	218	12.63	13.30
3883	247	12.54	13.21
4035	250	12.54	12.83	11.30	+1.24
4191	240	12.46	12.51
4375	241	12.38	12.46
4496	241	12.38	12.46	11.30	+1.08
4668	237	12.38	12.14
4824	232	12.38	11.87
5023	232	12.38	11.69	11.30	+1.08
5125	231	12.22	11.60
5316	223	12.22	11.60
5449	220	12.22	11.69	11.20	+1.02

*this was a WOT run, TPS 86.67. STFT = 0. didnt log LTFT, let me know if need to or any other data.

any help or guidance would be greatly appreciated. thank you!

Golden

iTrader: (1)

When your cams are set for massive overlap, you will see leaner than normal AFR due to blow by. We usually advance the crap out of our intake cam and retard the heck out of our exhaust cam to get that turbo to spool. This will cause "false" afr readings.
You have 2 choices.
1. Add a ton of fuel to the spool / just post spool area and flood the crap out of the car (because cylinder AFR is actually really rich) and get that nice number on your wideband.
2. Leave it alone and trust that no knock and a slightly leaner wideband reading is actually netting you more power.

momostallion

iTrader: (1)

lean afr due to blowby makes sense. is this how the stock cam timings are set because i haven't touched the mivec maps.

option 2 does sound pretty good to me. my AFRs do hit 11.2 at 7000 rpm and the power according to virtual dyno is good. i just figured i could gain more torque if i added fuel during spool but what your are saying makes total sense.

momostallion

iTrader: (1)

it's still find it strange why the AFRMAP value shows 12.2 instead of the 11.2.

Golden

iTrader: (1)

Is that what is actually in your AFR table?

If so, the reason is that things aren't scaled "perfectly" like MAF scaling. Note that I said "perfectly" and not "correctly". The Fuel Map values don't have to equal the actual AFR.

Making them close does help a car feel "smoother".


Oddly, I "quoted" a bunch in this post. I don't "usually" type like this. lol

momostallion

iTrader: (1)

lol.

yea, best example is that 5449 rpm line. evoscan logged AFRMAP at 12.2. my high octane fuel map table in ecuflash at 5500 rpm and 220 load is 11.2. even if it extrapolated up 1 cell for 5000 rpm, it was 11.3

this was done on an ALT map (which should make no difference). i'm going to move it to my regular map and log it again when the rain stops (hopefully before i go out of town).

richardjh

Golden, my confetti-like quote usage is rubbing off on you.


Mo, I totally understand you pulling your hair out on this. I've banged my head against the wideband AFR brick wall for over 12 months now. There's so much in the real world of wideband readings that doesn't track the nice, simple sounding "how-to" literature (look: more quotes!).


I dunno about the tens, but the Ralliarts' fuel curves need to go leaner by at least a full point from 3500 to 5500 just to keep real-world mixtures flat. There's a big inbuilt ramp in enrichment going on behind the scenes. As a side note, it's not all "Calibration Fuel Map" either... there's another mechanism/table at work. Just do the old additive/subtractive thing, and don't sweat the values.


Golden's explanation of blow-by is the one I've heard from numerous sources. For the stock turbo and/or exhaust setup on Ralliart, it's particularly apparent. My Innovate LC-1 wideband graph is pretty typical, in that...

- Measured AFR goes richer during early spool-up, until around 10psi.

- From 10psi to peak boost, measured AFR flatlines. It may even creep "leaner". Real, false, whatever... that's what you get on the graph.

- At peak boost, once load has finished rising, measured AFR drops like a stone... getting to the expected mixture ratio in no time.


I can point you at more posts, threads, musings from me on this than on practically anything else I've messed with.


For a while, I did Golden's CHOICE #1, and blurted fuel into the cylinders. It got the graph looking "correct", but it was sluggish on spool-up. It also ran revoltingly rich part-throttle through those same areas.

I've tried Golden's CHOICE #2. Part-throttle was healthily lean, and spool-up was spritely. All great, until I spent 20 minutes idling in line pre-track, got to the start point heat-soaked, went WOT... and audibly pinged my way out of the gate.

I guess those two places were my reference points for fuelling extremes. I'll revisit them if I ever want to (a) drown or (b) explode my 4B11. Sigh. This is why I use the phrase "I'm no tuner" so frequently.


So... the point to all this...

Spool-up mixture readings are a bit more of an art than a science, IMHO. BUT... science is still king, and will happily serve up a fistful of physics if you go too far.


Rich

tscompusa

iTrader: (31)

how much richer approx in the cyl? would you say around 1.5 points? thanks for that information also.. good to know.. i was looking at afr curves on lots of graphs and noticed most are lean and i was thinking, wow thats pretty damn lean for peak boost

Golden

iTrader: (1)

Rich: It's all your "fault". LOL

tscompusa: I'm exactly sure. I like AFR to dip to the mid 12's when boost gets up there, say 20 psi. Then it should come down to the 11's fairly quickly. The graph looks like this \__. I don't like it too lean during spool or just post spool. But I do let some lean slide.

Which brings me back to what Rich was saying about heat soak. I've never seen this issue with the way I tune, so I'd blame it on Rich's tuning skills. HA!

momostallion

iTrader: (1)

thanks for the reply rich. i think i'm going to just add a touch of fuel there from what i have now and roll with it.

this part kinda confused me. if you are at idle and in closed loop your leaner spool area shouldn't have effected your motor unless you are saying the already heat soaked motor combined with the leaner spool area lead to pinging that may not have been apparant with a richer AFR.

momostallion

iTrader: (1)

that's about where im at now. 12.5 -> 11.5 just need to tidy up AFR some more so it's not bouncing around so much.

Golden

iTrader: (1)

The stuff below 4000 rpm is fine. The AFR from 4000-4500 should be richened. There is a 500 RPM flat spot that needs to be delete. If you can imagine that.

tscompusa

iTrader: (31)

Ya i start richening after about 12-15psi is reached, get it ready to go richer for when it hits peak boost.. thats how i was tuning the X's and noticed it was still staying a little leaner so i was like wtf? now i understand though.

richardjh

Or lack thereof.


Yep, this exactly. See above as to why.

School of hard knocks!

Rich

momostallion

iTrader: (1)

I logged all LTFTs this morning. my LTFT_InUse was reflecting LTFT_Cruise which read 6.64 even during WOT.

those arent playing a role in open loop is it?