devilfish

6 years I have owned my corvette, a 1991 6spd model.
Been tuning it for 5 years.
I built a strong 355 with converted lt1 intake and some other goodies.
Im not consider myself a expert, far from it. This is just info that I wish someone told me back when I started to learn this.
Im sorry if this is to elementary for everyone these days. Feel free to comment, and ad own experince..
I would like to apologize in advance for my bad English.

Regards

Anders


1: Don’t rely on the knock censor for tuning. I chased tip-in knock counts for 1 year, could not tune it out. Very frustrated back then for a newbie as myself.
If the tune dont change it. Look for other causes that could trigger the knock censor before you get crazy with the tune, read plugs, and watch A/F look for trends. This can drive you nuts


2: Closed loop and lambda 1 is for the CAT not for the engine. Many engines runs better at another A/F then lambda 1. Mine did. I could NOT make my car run smooth at closed loop and cursing speed. No matter how much I tweak my tables. This issue drove me nuts for years!! The car jerking and bucking at light throttle, not much, but enough to drive me crazy.
For me the solution was to play with the “prop gain 02” settings. Decrease its value made a huge different. But the best results were when I disabled closed loop, and tuned the car only with my WB in open loop. Unfortantly this is not an option for me, as we in Sweden has “sniffer” test every year. And Im to lazy to install and uninstall my CATS once a year..

3: Don’t go crazy with the BLM’s, ( if you don’t like to torture yourself ). When I started to tune it almost seemed a “must” to have a perfect 128 BLMs across the board. This is absurd. And took to much time tuning/worrying and less time driving/enjoying the car.
And a stock tune is not that close. Right now im between 122-130 and happy with that.

4: Don’t stare yourself blind on curves, what other people have done, and “this SHOULD work”. I have ditched many tunes that felt good for the car just because I read some topic somewhere that , ( just a example ) THIS is what a spark table for MY setup SHOULD look like etc etc.
And then you start too worrie and think why my car doesn’t seem to run OK with that? Is something wrong?
If it works, if your car seems to run fine, ( and you are of course within certain borders) , let it be. Enjoy your car..



Again, this just some reflections from me. And after understanding some of this I have enjoyed tuning my car far more. And now I can just drive the car WITHOUT my laptop hooked up to the car, worrying about things all the time, now that’s a great feeling

Happy tuning.

Jaysz28

iTrader: (30)

Well said

Just give the motor what it wants. Every application is different, just as every location is different.

Glad you are enjoying your car!

-jason

???

iTrader: (5)

being only a few months into this... I too look forward to being happy enough to leave the laptop at home and just drive the car. even thou with gass prices, I don't know how much that will be anyways. my 4 cyc beater looks better every day gas goes up. I happen to start out using a mask that doesn't use cl or the norrow band o2 at all. so I feel like I've saved myself half the battle by just starting out without worrying about blm. good write up. I also agree 100% with the knock sensor part. mine hates me and I know its not real knock. so its turned off. I listen for knock with my own homemade stuff. I think its much better.

vetteoz

iTrader: (13)

Very nicely put.
I think sometimes we caught up to much in the science of a "perfect" tune
and forget about real world situations.

Fast355

iTrader: (2)

I will run open loop forever even with cats, my engine ran a carb for years with cats so EFI is even more controlled. On the emissions dyno, the numbers are almost ZERO's in EVERY pollutant. CO, HC, and NOx are ALL very low. The engine delivers PHENOMINAL gas mileage for what it is pulling and makes GREAT power.

I only wish people had taught me about the timing table years ago. I tried forever and a day to run it like ANY other small block chevy with 36* total by 3,000 rpm, NEVER worked so well on the real road. In fact many of my engines don't like much more than 26-30* total timing. My 305 Vortec TPI is proof that just because the curve looks weak on paper, doesn't mean it won't pull like a freight train at all speeds.

Orr89RocZ

iTrader: (20)

I like to add that some cylinder head designs are very efficient and sometimes that translates into using LESS overall timing than what you would THINK it would want.

Vortec heads seem to do this.


Also on the knock sensor, you can kinda desensitize it by reducing the ATTACK RATE table values and increasing the RECOVERY RATE table values. Also the total amount of degrees being pulled when knock is detected, factory is set to something like 8-15 degrees.. you can change that to 0-5 to limit the degrees of timing pulled when the sensor is detecting knock

becareful with that and only do so if your sure its FALSE knock... when it doubt be conservative with it since it will protect the engine... its best to pull timing to keep the motor from detonating than to not pull that timing and blow something up thats for sure!

Many threads on here about BLM's not matching wideband A/F ratios. Some ppl have tuned for 128 BLMS and notice wideband o2 readings are way off what you would consider right. Some cars are very lean when reading 128, but the car runs fine. When they adjust to get a/f ratios of 14.7 or so at idle and part throttle, the car runs poorly and stinks of gas like its pig rich!!

So do give the car what it wants, and check your values to be sure of whats goin on. It may seem abit off the norm but if the car seems to be running well, then leave it be

When in doubt, also check spark plugs and exhaust gas temp readings with a infrared laser temperature detector. Thats 2 more good ways to verify how the motor is running and compare those figures to BLM's and o2 air fuel ratio readings provided by the wideband

That being said i cant wait to start tuning my 383

DENN_SHAH

iTrader: (1)

a couple of the things i've learned.

make sure everything is right. you can't properly tune it if something is wrong such as a bad plug wire or a weak ground.
a wideband O2 is way more useful than you think. tuning in open loop with a WB is easy compared to closed loop with a narrow band O2.
when you get a good tune that works really well, label it so you know what it is & save a copy of it to disk or a flash chip in case of a hard drive crash.

something i read about but forgot to do, when driving around doing real time emulation, make certain you have turned off power saver & screen saver on you pc. also have a good fully charged battery or have your pc hooked up to a inverter.
also have a good working chip in the car with you, just in case.

devilfish

Also, many of us dont use these cars as a daily driver. With that in mind you can tune for preformance, reability.
A exampel, the stock bin for my corvette has around 46 degrees timing at crusing speeds, I dont gain anything in drivability or preformancewise with that aggresive tune. Its just for milage. The first thing I did whas to lower that.
And that made my oiltemp cooler, and that is more important for ME and the way I use my car.
It all depends on the application..

Anders..

Rebuildman

I have a '90 vette, can I ask what you use to datalog on your '91? I tried TunerPro, actually got it to work several times, but finally it stopped. Apparently it's not suppose to work with the CCM. Also tried Datamaster and couldn't get it to connect, I probably didn't try hard enough. Used up my 20 free logs. Anyway, what do you use?
Thanks!

devilfish

Datamaster 8D and a homemade ALDL to serial cabel.

93V8S10

I wish I would have known, that it takes longer than 3 weeks to learn to tune a EFI engine. When I started with my engine, that's what I was planing on, after all I had tuned this same engine with a carb. So far I'm on my 10th month now, still learning to tune. The process has been difficult, but it's worth it. A great running engine awaits, but that's not necessarily what makes it "worth it". It's the new skills we learn along the way and the new friends we make, that make it "worth it".

malcom2073

I wish I would've known to get my car in perfect (stock) running order before trying to tune. Turns out one of my spark plugs was cracked and shorting to the block causing all sorts of weird issues I could never track down.

devilfish

Good point. If you got problemes, check all mechanical stuff first, before you go crazy with the tune. Hade the same probleme with a bad plugwire.

Grim Reaper

I don't know how many times I made that point (make sure your engine is in proper tune) when I've tried to help someone tune their engine.

conv90

Well said Devilfish!
Now what it's make me crazy is the knock sensor!
Sometimes I have the sensation it's real knock, sometimes the same spark table has no knock, sometimes it remove much more timing than the degrees I added ... sometimes only removing a fraction of degree I can cure a situation where up to 6 deg are normally pulled out.. ... and sometimes the same spark table has heavy knock (and timing removed) with similar oil and coolant temp...
...

Grim Reaper

I found it best to "disable" the KS when I go WOT and use "old school" methods to determine if detonation was actually occuring. I've made lots of post on the KS and I only use it in "part throttle" regular driving (just in case I get a bad tank of gas). But, for WOT, I just disable the KS.

conv90

The real strange thing in the timing I have, is that sometimes I have 0 knock counts at 32 total timing using the 2nd gear to 6000 rpm, and with the same timing curve I have up to 6 deg of timing removed if I use the 3rd gear.
No knocks on 2nd gear, and knocks in third gear (the only different thing is the speed.... rpm range is the same and load is the same -100Kpa- ).

antman89iroc

Yep, get everything mechanical in order. I've tuned to a leaking AFPR, vacuum hoses disconnected etc. Very frustrating!!!

In regard to false knocks, I've suspected valve train, manual tranny and loose accessory brackets as being possible sources.

BLM's... well they are what they are. Sometimes they can be helpful as a guide, sometimes it's just chasing an ideal.

Fast355

iTrader: (2)

The load on the engine is NOT the same. The lower gear has more torque multiplication and the engine blast through the rpm band quicker. In the taller gear, there is less torque multiplication, the rpms increase slower and the engine is more heavily loaded.

I can also think of times where it is possible to load the engine greater than 100%. Like my van pulling a loaded trailer uphill and me deciding to go WOT to pass a slower moving car in the climbing lane. In second gear all is fine, but hit third, and the torque multiplication/power output is not enough. The van will start to slow and when it did, all hell broke loose as far as detonation was concerned. Knock counts went through the roof.

conv90

I was sure about this... the problem is that I can't find a way to modify the timing and the fuel in the chip in this particular situation.
Load is measured in Kpa...and a WOT in 1st is the same than a WOT in 4th
-Beppe-

Fast355

iTrader: (2)

I know Robert Rauscher wrote his TBI code so that the PE spark could be varied as the NV ratio changed on a stick car.

Grim Reaper

Yes, but they do it at different MPH (and the speed/rpm reading on some calibrations too...if you are looking for a way of detecting which gear you are in). I've actually felt that you almost need a slightly different set of VE & Spark Tables for each gear because of the different loads that Fast355 mentions.

If you are into "programming" you could make an Spark Add/Subtract Offset table (similar to some of the Cold Start Spark tables in some calibrations) which would "fine tune" the spark advance (and possibly the Fuel) for each gear. Some calibrations (like $8D) have lots of "vacant real estate" inside.

conv90

I know, I know... the gear selected will be easily detected, but I'm not able to do a modification like this.
I'm able to change parameters/tables and modify some ECU.
The modification of the bin to achieve relationships between values that are NOT in a ECU, are not on my skill.

JP86SS

iTrader: (1)

I some cases a lean running decelleration will put extra heat into the cylinders that when you get back on it knock will occurr.
Happens more as your intake heats up and is heating the incoming air more. Usually takes agood 1/2 hour of driving before it starts so it was hard to track down why this was happening.
I'm experiencing this quite heavily right now with a pretty aggresive spark setup. As soon as I touch the throttle after coasting a bit, the converter locks up and the load sends the KS into a frenzy at 1300-1400 RPM. After a few seconds (and 4* out) it calms down and is fine again until I coast for more than 20 seconds anyway. Less than that has no effect.
Probably could raise my lockup points so there would be more RPM at the lock point but I like it where it is speedwise. If there was only a way to take out 2* at the lockup point for 2-3 seconds the problem would be solved.

RednGold86Z

iTrader: (1)

Some other good to know things:

Left and right banks won't read the same A/F with the stock fuel pressure regulator location.

Canister purge can add a lot of fuel.

EGR will mess with a SD tune more than a MAF system.

Transient (AE) enrichment is not easy to get right (can take months), and impossible to do without a wideband. It's impossible to get AE perfect.

Use a wideband, it'll open your eyes to a whole new world. But, it may also make you realize that either tuning is hard and tedious, or that tuning is fun and rewarding.

Know the algorithms and their intended purpose before changing the wrong things so much.

Sometimes bang/bang tuning will help you learn - ie if you want to get a better idea of what some software does, make a drastic change and see. Then go back 50%, then see. Home in on the target. Don't do this too much with excess spark or too little fuel.

Engine's aren't as fragile as they are rumored to be. But, don't go keeping your foot in it until it's all squared away and you're sure it's in a safe enough condition.

A good working ignition system is priority #1.
Actually, all the hardware needs to be working 100%.

Don't be afraid to check fuel pressure and cylinder compression (and spark plugs) too frequently.

Works out-of-the-box doesn't mean works right out of the box.

.
.
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bl85c

iTrader: (2)

Start with a known good tune. When I converted to a tpi ecm I copied most of my tune straight out of my old '870 ecm and filled in the rest from a '302 bin. Didn't run great, but it got me started.

pandin

100 KPA is not load. It is atmospheric (barometric pressure). If you have a free enough flowing intake, then there will be no vacuum between the air cleaner and the intake valve. This has little to do with engine load at WOT.

The engine could be fuel regulated as a diesel is or exhaust restricted (false load). Cylinder pressure/Torque are the true indicators of engine load.

To develop peak torque the load has to be greater than the engine can move. Most torque is measured corrected for slip/stall. An engine making peak load (torque) equals no rpm gain (think tractor pull).

How much load (torque) is made by revving an engine in neutral? No/low load equals quick rpms.

Tuning based on incorrect/false physics/logic will not work.

The ECM is blind and stupid, it only returns, what it is programmed to do. It is only math/numbers representing the real world. X value + Y value = Z value. It is only a calculator until the numbers in/out are attached to something real, like the Maf or injector.

Like the recipe for a cake, without the flour, eggs, and sugar, it is only words.

DM91RS

[QUOTE=RednGold86Z;3778864]Some other good to know things:
Transient (AE) enrichment is not easy to get right (can take months), and impossible to do without a wideband. It's impossible to get AE perfect.
[QUOTE]

I have thought about this allot lately and have to agree since there are so many different conditions were it will exist. However what has gotten me thinking about it is mpg. If you get the cruise tune to be decent and your AE is off every time your give it a bit of throttle and the fuel added is more than necessary you are fighting a loosing battle or at least staying even and not gaining in your effort if you know what I mean....

RednGold86Z

iTrader: (1)

A little misleading, not false, but thinking from the wrong side of the engine.

A full throttle spark ignition engine at 100kPa at Lambda .85 and RPM 3000 will make the same torque whether there's a light "Load attached" or heavy, or not at all. The engine sees almost the same thing at that instant it's at 3000. In extreme sweeping cases, the spark advance could be from "old" data (especially with electronic distributors with 8 reference pulses for 8 cylinders, but there is some delta RPM compensation in the software, usually), thus messing things up. With no load attached, the crank deflection is a little different, but it's not worth talking about, because it's not a condition with any consequence.

A vehicle mass attached, or dyno attached, will absorb the engine torque and translate it into heat or motion. With nothing attached, the torque goes into accelerating the rotating assembly.

With an extended time in WOT, the pistons, heads and oil get HOTTER! This will reduce the knock threshold. This is probably why most people think they need different spark advance per gear.

Also, if you're experiencing knock on shifts or lockup, it's probably from being a little bit leaner from fuel being robbed and going into the wall film from lower air speeds and higher pressures at lower RPM + high MAP. Wall film is THE key to engine fueling. A lot of the fuel goes into the wall film before it goes into the engine. The evaporation rate depends on temperature (wall, air and fuel temps), pressure, fuel flow and air flow rates. It IS the major reason we need transient enrichment (AE). Sensor lag and airflow overshoot are the other minor reasons. There are several "walls" to consider - port + valve (AE), cylinder walls + piston/combustion chamber (cranking and afterstart enrichment, AE, and some warmup/open loop stuff), and the fuel that backs up into the plenum (most difficult to compensate for, but attempts to be covered by AE). Keeping the wall film at its desired condition is where calibration engineers and software designers get their money. Direct injection should be a lot easier in this respect.

pandin

So when you "wet the walls" the fuel is "lost" and then, depending on the evaporation rate (temperature (wall, air and fuel temps), pressure, fuel flow and air flow rates, the fuel is "found".

Is this, extra fuel, then burned and/or sent down the exhaust pipe at a later time, to mess with the Afr?

RednGold86Z

iTrader: (1)

Yes, most fuel that is "lost" on accel, is "found" on decel. The port and plenum store the fuel. The wall films inside the cylinder are lost out the pipes as HC, or burned too late in the cycle. It really makes a steady state a rare thing.

RBob

iTrader: (1)

Another area where that lost fuel is found, is as the RPM increases. The higher air velocity through the system strips the fuel from the walls. This causes a lean spike when an auto upshifts during a WOT run.

As the RPM drops (from going to the next gear) the AFR dips lean. This is from the air velocity dropping off causing fuel to be placed back onto the walls.

Note that a stick car would do the same thing if shifted without lifting. Speaking of which, wanna' see the AFR all over the place? Data log a stick car along with a WB just driving around in stop & go type city driving.

RBob.

DM91RS

Yeah.......let's see it.......

Actually meant to comment that when I first got my ZT2 that was one the first things noticed.

RednGold86Z

iTrader: (1)

Exactly right.

For EURO4, with stick, I wrote a new wall film model. During normal transients, you cannot even see the AFR waver. During cold shifts, there's some rich deviations, even if the injectors are completely shut off, so that's impossible to cure. After an extended higher load (anything above about 50kPa, for more than about 3 seconds), there is also rich during shifts, due to the runners and plenum getting wet. After about 2 months of calibrating strictly for emissions, finally got it to about 40% of the limits (two engines - 1.5L and 1.8L dual fuel, but running only on gasoline with injectors about 2 inches farther away than the methanol injectors, which makes it about twice as difficult). When switching to methanol after 2.5 minutes and above 60C, the emissions are even better (20% of limit).

zapeee

I'm a little new to EFI tuning, but any more than 42 degrees with an HEI and a carburetor is supposed to spell melted pistons. seeing the stock max timing constant for the 454 i am tuning at 41.84 degrees rams this home. i dont know about your engine, but it seems like (someone correct me if i'm wrong, but i cant find where it goes- the dipstick covers the only likely location) my engine came without a knock sensor so there is nothing to bring it back to reality.

1995 k1500 yukon 5-speed 2-dr with MKIV 454 from 1988 K3500 4-speed.

anyone ever see an AFTA bin?