11sORbust

I just went on a trip, it was 220 miles one way.It's a very tired 305/tpi, my red car. The old bird cracked the 200,000 mile mark on the way home. I have been running a 165 ecm w/o a maf sensor for some time now, as you might remember. I have made a few changes to get it running fairly well. Closed loop and all. THe a/c was on and the car was loaded to capacity..

THe averages was,
24mpg
84mph
170 coolant temp(steady)
80-90* ambient temps

Not bad for an old motor,heh? Wonder what kind of mpg a strong 305 TPI would pull down(w/ working maf and ecm tuning)?

Low C1500

Well not sure about a 305, but my 2001 9000lb dodge 3/4 ton gets 22 mpg/

But seriously 24 is OK

11sORbust

I can answer that...kind of. Well, the body and rest of the drivetrain is good and close to 300,000 miles now. My old 305 gave up the ghost at 279,000 miles. I installed a stock 91 TBI 305 out of a 91 firebird vert. This engine ran 13.2 with headers and a 100shot of N2O. It worked fine for about 20,000 miles in my T/A wjile daily driving(I never ued N2O on it). Right when the car reached 299,00 miles, 4 top rings broke. I pulled it apart replaced one piston and rebuilt it myself. Still running alpha-n mode on my original 165ecm. 500 miles (of break in) later and the tune somewhat close. The average highway mpg is 26. Not too bad considering I will increase gains with more tuning. Everying has been done myself, from the head porting to tuning..

Mods to my 86 T/A:
91 firebird 305 TBI engine/w
Ported factory TBI heads
Comp Extreme Energy cam (212/218*_509"/530"_112*)
1.6:1 stamped crane rockers
stock LS1 injectors
1-5/8" long tube headers
SLP loud mouth cat back (w/o cat)
MAF delete pipe
My stock TPI intake (slightly ported)
LT1 valvesprings and retainers

Here is the key. I'm running w/o the MAF/MAP, O2, KS, MAT and all the emissions equipment. That really just leaves the CTS, TPS and RPM and the only ECM inputs. AFR is in the high 14's/very low 15's durring most of normal driving. I just need to remember the locations to to add the default airflow table to tunerpro(again). Once that is done, I will be able to increase MPG beyond 26. I have logged about 130,000 miles in alpha-n and don't see any reason to change.

RednGold86Z

iTrader: (1)

Until your weather changes, or you go up a mountain. Then you'll be hurtin for a MAP sensor.

dimented24x7

iTrader: (2)

The code for the TPS based redundant fueling in the TPI ECMs is extremely crude at best. Its literally like 20 lines of assembly and only uses the TPS and IAC flow to estimate the default airflow. Basically, its there to get you off the road, or to a shop.

If it where me, Id hook up the MAF, or go speed density.

dimented24x7

iTrader: (2)

Heres the alpha-n code from the $6E... Alpha-n can be made to work well, but it would require, at the very least, baro and IAT compensation.

RBob

iTrader: (1)

It is actually quite surprising how well they run in N-Alpha mode. The malfunction code creates an airflow value instead of the MAF, and everything else is the same.

RBob.

RednGold86Z

iTrader: (1)

On our ECU we run alpha-N for limp home, and just have a new table that converts TPS vs RPM to a MAP value, and the lookup is done on the VE table. IAC is very important (especially with AC on/off), but we haven't added it in yet (software guy says the customer should just take the car to get it fixed).

The alpha-N works great at one altitude. Works like poo on a real mountain. Wish there was some legitimate way to take the fuel adapt value to estimate BARO... Maybe there is... But, the Alpha-N needs the opposite effect to fueling - whereas if in SD, more VE is needed at high altitude, but alpha-N gets to be soooo rich.

dimented24x7

iTrader: (2)

Didnt honduh actually put a baro sensor right in their ECMs? That would be one way, but Id have to agree with the software guy. Go get it fixed already... Although this seems like a surprisingly hard concept for some people to wrap their minds around.

V8Astro Captain

iTrader: (1)

What benefits do you get running it this way?

11sORbust

If you didn't post that, I might of needed my flame suit. The above quote is DEAD ON. I have alpha-n running VERY well. Over 100,000 miles. 26 miles per gallon. I do not need to touch the accelerator pedal on cold starts. Idle is rock solid. DA can swing over 2000 feet in one day around here, easy. I think it was last week and 78*F, the next day 30*f.

The question is not why, but why not?

327_TPI_77_Maro

iTrader: (8)

If you have some bad feelings about MAFs, why not convert to MAP? Did a MAF sensor scare you when you were a kid and you have lasting hurt feelings over it? I mean, you can run a carb if you really want to, it just depends on how much fuel trimming you want.

RednGold86Z

iTrader: (1)

Hehe, 2000 ft??? That's nothing (just messing with ya).

Just a little about what a real mountain pass (with a road) that we test on is about 5000m (meters) (over 16000ft, and 52kPa Baro). That's high enough to make you literally feel high, and sometimes want to throw up. The car does too, when in alpha-N (that was calibrated at sea level).

As long as your standards of what's good enough are low enough, alpha-N works fine. I've done a few in the US as alpha-N, and no complaints (and no IAT, just TPS and CTS, like on a IR 502/502 but not with GM efi). Low throttle is the hardest part, though, and any throttle or TPS adjustment requires a retune or other adjustment.

But, big cam guys that race and don't drive a lot may find Alpha-N to be much much easier to deal with, and I wouldn't blame them. It's simple to understand, and simple to tune. And if they run a wideband, they can make a simple adjustment if the weather causes any problems.

dimented24x7

iTrader: (2)

If your car sees relatively constant operating conditions, then your ok. If you see lots of teperature or baro fluctuations, then you should switch to a system that has a more sophisticated alpha-N algo. Alpha-N can work as well as SD or MAF, but the stock $6E stuff is straight up bare bones. I think it would be worth persuing if you like that fueling stratagy.

One thing about a stock or near stock engine is that its surprisingly tolerant to AFR fluctuations. Itll run at 16:1 and at 12:1. Ive even run mine at 20:1 at WOT by mistake. Doesnt make much power, but it runs... The big advantage to accuracy is that the engine runs smoother and more uniformly if the AFRs are on target and dont vary over the short term. I found real gains by getting the fueling to within +/- 2% of my desired AFR over most of the engines operation. This and it performs the same each time I jab the gas down. Right now its just in the ballpark. Sort of like what youd get with a holley carb. If thats the way you like it, then hey, run with it. But, with a better algo, I think you could get much closer. JMO

dimented24x7

iTrader: (2)

Not flaming you, BTW. Just a bit opinionated like everyone else on this board.

Also, FWIW, I too use alpha-N, but during transitions. There is a phase lag in the MAFs response due to how a frequency based MAF system works. During the first 1/4 of a second during tip-in, the reported airflow is way behind the actual airflow. On tip-in, I use a delta TPS term along with the IAT and baro TPS compensation to construct momentary delta TPS based fueling to cover for the transitional airflow. Without it, the engine backfires on tip in and goes dead lean for a split second.

RednGold86Z

iTrader: (1)

(Dimented) Whether or not the airflow is lagging on the MAF, you still have to compensate for the wall wetting from the pressure drop at increasing throttle (and with TBI, whoa, dats a lot-o-wall).

Also (11's), I'm not flaming with what I mentioned in previous posts too , and hope any criticisms or other views are constructive!

11sORbust

"Over 100,000 miles. 26 miles per gallon. I do not need to touch the accelerator pedal on cold starts. Idle is rock solid."
..AFR is in the 14's everywhere but WOT. That is my standard...
I can manually change the calibration when I make that 16,000 feet journey, lol. Seriously, does your car run much better than described above?

It's not really about simplicity, more about resolution. Race cars idle at (aprox) 75kpa and run 100kpa even under "normal driving". Huge stall converters blow through the rpm range, reducing the need for load resolution. ... etc, etc....

11sORbust

You really have no clue about the MAF and I. Might want to do some research.he,he..
EFI is the only way to go. I'm here to say the MAF vs SD wars are old news. No load sensor is the new front.

327_TPI_77_Maro

iTrader: (8)

"The MAF and I" sounds kinda like "the King and I"

11sORbust

I was going to change to the 730 but everything is tuning out just fine. If my afr/sa/iac/throttle response and performance is dead on, then why switch?

dimented24x7

iTrader: (2)

I have that as well. There is long duration AE based on the delta MAP, RPMs, and manifold plenum wall temperature to cover for the ever changing AE requirements due to the fuel wetting the walls. The engine wont even run when cold without it. I disabled it just for yucks a long time ago and the engine shuts off as soon as I hit the gas. With all the compensation, the AE is pretty much transparent so long as the injectors can keep up with the fuel demand. Lol, you can definatly say that again. I have a cold air intake as well as an unheated manifold and even with 250 PPH of injector, the injectors are static and still cant quite keep up when the temps are below 35 degrees.

The short AE based on alpha-N lasts just a few hundred milliseconds to cover for the momentary lean spike. Without it, there is a loud snap out the intake on fast tip-in from being super lean for a split second and then the car goes normally.

dimented24x7

iTrader: (2)

A basic carb will also work well, but the fueling wont be accurate. One thing Ive discovered is that the accuracy of the fueling is proportional to the complexity of the software model controlling the fueling. You can have a simple model, but it will only approximate the fueling. You can have accurate fueling, but this requires a complex model that can accuratly estimate the fueling needs of the engine over a broad range of operating conditions. Regardless of whether its MAF, MAP, or alpha-N, the simpler model will be easier to tune, but more rough. The more complex model will provide accurate fueling, but be harder to tune. In the end, its sort of a balance between the two.

Grim Reaper

There is no need for that type of crack.

Post locked due to complaint.

Grim Reaper

On a technical note, I think its rather clever for a person to "tune around" an inoperative sensor (regardless of sensor) and actually maintain a good state of tune.

One never knows when a sensor may fail, one is not readily available and a person needs to keep the vehicle operating. Especially if it is their only car (as is the case for some members).