Jim in Tucson

iTrader: (3)

I find that with the EVO AFR's are always expressed like so:

By Recompile
I've got lean spool off, and I shoot for:
12.5 @ 3000RPM
12.0 @ 3250RPM
11.5 @ 3500RPM

By John Bradley
12.1-12.2 at spool
11.5 all the way to redline

By Nj1266
12.5 AFR during spool up
11.7 AFR @ peak
11.1 AFR by redline


My question is, why are AFR's never expressed in terms of load, or even boost?

I come from a car with a MAP based system where the AFR's were expressed by pressure:

20 kPa = 14.8 afr
60 kPa = 14.7 afr
100 kPa = 14.0 afr
140 kPa = 12.5 afr
180 kPa = 11.5 afr
220 kPa = 10.5 afr

So, regardless of RPM or TPS the AFR targets were specific to the amount of "load".

Since the EVO ECU is a load based system, to me it would seem less vague if AFR's were expressed in load.

I can understand tuning the WOT pass using this:
12.5 AFR during spool up
11.7 AFR @ peak
11.1 AFR by redline

But, how is the rest of the fuel map tuned using just the above targets? Or are most of you simply tuning only the WOT pass?

JohnBradley

iTrader: (30)

Mainly because a properly set up map, assuming no fuel pressure drop or injector problem, will use the same value at 140 load as it does at 300 and only vary as the RPM increase normally. In the AEM its referred to as Boost Comp, which is what the stock computer does (even in SD) more or less.

There are a few minor variables but for the most part if the turbo doesnt hit its limit, the injectors and pump arent limited, we can say XX AFR (target or real) at XXXX rpm and be accurate.

03whitegsr

iTrader: (8)

You can run A LOT leaner at lower loads. At 160 load, you can run damn near 12.5:1 with good timing advance on 91 octane. 200 load you can still run 12:1.

I think most tuners just set anything above about 140 load to the same value and only tune based on RPM. They don't intend boost to change, so they tune to the boost level they are at and flatten it out over to the low load areas.

It's a waste IMO as you can make the car quite a bit more peppy down low with proper tuning. It's very typical of what I have seen posted here though.

JohnBradley

iTrader: (30)

I maybe should have said 160, because I agree with you Michael.

However my point is it boost comps so you can do it how you want. I actually havent seen cars lean knock until about 13.0 on gas at 10-12psi but thats not what I am aiming for. Evos seem to be very knock resistant vs AFR.

03whitegsr

iTrader: (8)

Yeah, I wasn't targeting you, I read it though and it looks like it. Sorry if it came across that way.

I've just noticed that not much time is spent on a lot of maps at the low end and to a large extent, I agree with the original poster that it seems to be more relevant to map AFR based on kPa and not RPM.

Most seem to hold AFR constant once the car hits peak load anyway so they really aren't tuning by RPM either.

LGshow19

iTrader: (51)

What do you consider to be "low end"? ( ex. 80 load=low end)

Jim in Tucson

iTrader: (3)

I ran across this some time ago on Evom and saved it. I did not make this; don't recall who did, so I can't give them credit.



I think 03whitegsr is saying that most EVO owners and even professional tuners focus their tuning efforts almost exclusively on the spool-up and WOT trace.

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I'm used to a tuning style called "steady-state tuning" where using either accelerator foot or EBC, the entire fuel and timing map is tuned at increasing levels of boost, or load. When completed all areas of the map(s) should be considered maximized, not just the WOT trace.

Jim in Tucson

iTrader: (3)

I actually consider 90/100 the breaking point; =>100 are the load cells and <100 are no-load cells. The low load area would be 100-160; or something like that.

This is exactly what is so frustrating to me. The ONLY part of the map discussed ad nauseam on this board is the WOT trace. Beyond that, we don't even have words and definitions, let alone numbers, to describe the rest of the entire map. EVO owners typically take a very singular approach to tuning, IMO.

03whitegsr

iTrader: (8)

I use the brake and gas all the time when tuning a car. It's showed some very interesting results on the SD patch and is the main reason I think we need more MAP resolution. The VE changes substantially from about 80kPa to 140 kPa but you are pretty much out of adjustment points once you take care of the <80kPa range and you have to lock the top end, more or less.

I would say VE is dominated by throttle position below about 80kPa and then from 80 to 140 or so, the turbo seems to be in cross over and VE goes way up, then drops back down as the boost goes higher. This is on a stock IX turbo anyway.

Of course, you can correct the issues using the main fuel map and plugging in appropriate values, but I've been trying to get the calculated AFR to match real world AFR using the VE stuff.

Boosted Tuning

iTrader: (12)

Thats not "steady state tuning"

To do steady state tuning, you need a dyno with load control.

Jim in Tucson

iTrader: (3)

I did not say it was. Please re-read my post.

Not 100% true. Steady-state tuning can be done on the road. However, any road tuning lacks the more controlled environment of a dyno lab, that's for certain.

03whitegsr

iTrader: (8)

Steady state, in this regards just means you hold load and RPM constant enough for everything to stabilize and additional corrections (accel enrichment mostly) to drop out.

Only takes maybe 5 seconds at a given load and RPM point to get 30-40 samples of the AFR which is good enough to tune off the statistics of the data.

To do "steady state" tuning, I do two things.
1) Hold RPM constant with brakes while increasing the throttle position in steps. I usually do this from about 50kPa to 140kPa.
2) Hold MAP constant while dragging the brakes to make the car accelerate slowly through the RPM range. This one should be done on the dyno though and is asking for a car wreck. I usually do 4-5 MAP values and 1500 RPM to 5500 RPM in third gear.

Finding a long hill helps too.

I usually just do it in one big *** log. I use IPW, Accel, and decel enrichment channels to filter out the data where they are active since they will skew the data. I compare actual AFR to AFRMAP to calculate "AFR Error" and plot it vs MAP and RPM. I use log works to analyze the data because it gives # of samples and STD to help filter out good and bad data. It produces excellent data above 40kPa and 2000 RPM. Below those points though, it produces a ton of error.

Boosted Tuning

iTrader: (12)

IMHO, "Steady state" tuning as I know it should always done on a dyno, not on the road.

03whitegsr

iTrader: (8)

I can hold RPM more constant with the brake than some of the dynos out there that do steady state tuning.

It is definitely easier on a dyno though, and probably a lot safer.

Jim in Tucson

iTrader: (3)

Agreed. Most road tuners who do this style of tuning will search for a long steep incline. Much easier to hold a load with gravity working against you.