Grumpy

While this is a little on the tangent side of things, I thought it might be at least interesting. Tangent in so far as none of the oem code as implimented will allow it, but with some cleverness others might be able to attempt something like this.

Of course this is for off highway use cars, that are not equipped with converters.

Usual YMMV, and if you don't know what your doing be sure to get some adult supervision, LOL.

Anyway, In the past I've been able to get really good highway mileage, but the idling around the pits, and staging lanes was never to good.

So I began watching the WB really close and playing with the R_T stuff. R_T meaning the real time tuning package from Xtronics and Tunercat.

On a low stall stockish converter setup the idle AFR has to be rather rich to suport the work load of the converter and tranny so about 15:1 has been the lean limit for my car. Then at the higher speeds, 14.2 seemed sweet. But, I never really played with the low speed stuff. In JUST doing some low speed work, I was able to run 16.5-17 at low rpm light loads, ie 30-40 MPH, and the car was fine.

The trouble is that it takes a high resolution VE table to get it just right.

Drat, I tried to get this to wrap right, but it looks like it wont.
Anyway, this is in raw hex so to see the number in actual VE just multiply them by .3 for a rough idea of what it look like in ture VE. But the 40/90 area is where all MPG gains from over run and light throttle conditions are.

BTW, I with about 20% of the last tank of gas done in stop and go traffic, I've gotten about the same mileage as I would have as if it was straight highway mileage.

Map: 20 25 30 35 40 45 50 55 60 65 70 80 90 100 ; RPM:
08, 108, 113, 113, 113, 113, 113, 113, 118, 123, 131, 136, 141, 145 ; 400
108, 108, 113, 113, 113, 113, 113, 113, 118, 123, 131, 136, 141, 145 ; 600
59, 102, 115, 113, 113, 113, 113, 113, 123, 128, 128, 133, 138, 138 ; 800
25, 25, 51, 115, 118, 118, 118, 125, 133, 133, 133, 133, 133, 133 ; 1000
25, 25, 40, 40, 110, 120, 125, 133, 138, 141, 143, 143, 143, 143 ; 1200
0, 0, 40, 40, 40, 120, 133, 138, 141, 143, 151, 159, 159, 159 ; 1400
0, 0, 40, 40, 40, 90, 138, 141, 143, 148, 156, 164, 164, 164 ; 1600
0, 0, 40, 40, 40, 90, 138, 143, 146, 161, 166, 174, 174, 174 ; 1800
0, 0, 40, 40, 40, 40, 146, 146, 148, 164, 169, 179, 179, 179 ; 2000
0, 0, 40, 40, 40, 40, 146, 146, 148, 164, 169, 179, 179, 179 ; 2200
0, 0, 40, 40, 40, 40, 146, 146, 151, 164, 169, 179, 179, 179 ; 2400
0, 0, 40, 40, 40, 40, 146, 148, 151, 166, 169, 179, 179, 179 ; 2800
0, 0, 40, 40, 40, 40, 148, 148, 154, 166, 169, 179, 179, 179 ; 3200
40, 40, 40, 40, 40, 40, 151, 151, 154, 169, 169, 179, 179, 179 ; 3600
40, 40, 40, 40, 40, 40, 151, 154, 156, 169, 169, 179, 179, 179 ; 4000
40, 40, 40, 40, 40, 151, 154, 154, 156, 169, 169, 179, 179, 179 ; 4400
40, 40, 40, 40, 40, 151, 154, 159, 159, 169, 179, 179, 179, 179 ; 4800

I also have a spark table that is reference to VSS
While I generated this for an aero loading compensation, it also helps with low speed MPG by allowing more timing down low.

VssSa:
;--------------------------------------
; SA ; mph
;--------------------------------------
FCB 0 ; 0.0
FCB 0 ; 10.7
FCB 0 ; 21.3
FCB 0 ; 32.0
FCB 0 ; 42.7
FCB 0 ; 53.3
FCB 0 ; 64.0
FCB 11 ; 74.7
FCB 11 ; 85.3
FCB 11 ; 96.0
FCB 11 ; 106.7
FCB 11 ; 117.3
FCB 17 ; 128.0
FCB 23 ; 138.7
FCB 23 ; 149.3
FCB 23 ; 160.0
FCB 23 ; 170.7

Again hex values, and the exact math is multiply by 90 and divide by 255. And they are degrees of retard. While not big corrections, they are signifigant, performance wise. I'll admit the last couple entries are just guesses at the moment, LOL..

Just sparkin some thought...

RBob

iTrader: (1)

Using the 'code' keyword should work:

Grumpy, when you said in hex, I think you meant in decimal. The values are actually decimal numbers.

RBob.

Grumpy

Did it again didn't I?.
Ugh, wait a min Doc was supposed to be have edited that. That's it, it's Doc's fault.

Grumpy

Just as an update.

While guaging around town driving from day to day as being the same is at least difficult, it would seem that the MPG number is up about 3 MPG.

I think I'll raise the 40's just ever so slightly, and drop the next colums down a little, there was a little glitchiness just off of real light throttle to light throttle.

CheezX

This is all done in open loop I assume? Did it make a difference in driveability?

Grumpy

Yes, Open loop.

Yes, MUCH better drivibility.
By having a slightly rich cruise the combustion chamber temps are just a tad lower. So not as much accleration enrichment is needed, so all the tip-in conditions at cruise are much crisper.

The throttle response is very linear. Just lean on it a little and it responses. Also, with an intial TPS of .42, cruise at 70 is about .85. The engine is happy.

JPrevost

Took me 3 years to figure that out . Most of that time was wondering why I didn't have the cash to change the fuel pump .
I always wondered why tip it was so much better with BLMs in the low 120's.
Every car is different though. I tuned a guys L03 camaro and it was crisp with stock pump shots and BLMs at 128-130. I need a bigger book for reasons NOT to buy an eprom from some "tuner" through the mail or over the counter.
BTW, my milage has gotten better now that I'm running 87 all the time and less timing while in open loop. The trick is highway mode, tcc activation at low speeds and NOT unlocking with the lift of the throttle!

bnoon

That little tidbit right there can drop you 1-2 MPG if it's not done. I just found that in mine and am back up to within stock MPG readings on a 280 degree cammed 305!

RedIrocZ-28

Interesting, how would you program that out? I'm at work and have none of my software to look at but I take it that it has to do with the TCC lock and unlock stuff.

Also, To tell you guys that I have made big progress in low speed drivability with 3.73 gears, and a 2800 Vig. lockup. It was interesting to note that since the speedo driven gears read wrong (37mph=50 speedo mph), the TCC would lock up under part throttle at about 20mph. This made for some frustrating "jerky" low speed driving. All that was needed was to caibrate the chip to lockup at roughly 37 ACTUAL mph rather than 37 "speedo" mph. (all figures are rough numbers) Anyway, The car is a dream to drive now again.

Anyway, how does one do this trick with the TCC and better mileage?

Kingtal0n

I am playing with my spark and fuel maps on the commander 950, and ive noticed that my motor doesnt like to idle closed loop at all.

ive also noted that if you give it a bunch of timing right off idle it wants more fuel but has much better throttle response.

i have it set to hit 45* of timing during all cruise situations, (on 87 octane, 9:1 compression Aluminum heads) i can go a max of 48 before i see 1-2* of spark retard here and there.

my PW on the highway @ 65MPH is between 2.5-2.8MS, and thats at about 1500 RPMS (2.73, 700R4).

I JUST started to tune this thing, going crazy with the intermitted vacuum leaks its having... <b>Im curious what are people running as far as timing and Pulsewidth / MS(DC%) on the highway and around town?</b> I went 55 miles highway driving on less than 2 gallons of fuel yesterday, so its doing way better than i expected it would.

the converter is stock and the cam starts picking up around 2,000 rpms though, so off idle torque (even with TPI) is really bad, and forget cruising below 1300 RPMS... it jerks and kicks.. im wondering if its my tune or the cam?