I mostly agree with this, but once you get into street/strip, the reasons can start to add up in some combos. In many FI setups with older MAFs, the MAF just gets maxed out. Any use of leaded race fuel will **** up o2 sensors. That being said, think of this as less of an argument and more of a presentation of a differing opinion.

 

Yeah, gametech, I never meant to sound like I was arguing, just getting straight why OLSD is used. As you said, in a competition situation where leaded gas is used, then yeah, OLSD is pretty much what you have to do. I think my position was more about street use. I keep learning around here, and it's all good! Have a good one

 

So your saying since I don't drag my car and don't run leaded race fuel I should go back to a MAF tune? My car seems to run great except when its really cold it like fuel at startup.

 

All things being equal, a MAF will enable your engine to run more precisely than without, given the tune is spot on, which it should be anyway. The MAF tells the ECM how much air is being used. Otherwise the ECM refers to tables to guess how much air is coming in. It IS an educated guess, but a guess nonetheless

 

I just need to find a 90 mm MAF and a retune, funny this came up as I was thinking about going back to A MAF and then this thread popped up

 

Tuning a MAF with boost seemed to be more work than it was worth. After the MAF is maxed then the only option was to scale everything and I didn't want to do that. I knew long term I would have to go SD regardless so it seemed best to go ahead and do it now rather than scale everything then switch to SD later any way. I'm seeing 10 pounds of boost at 6500 rpm with a cam and long tubes so I'm pretty sure I would of been past the limits of the MAF already.

My car starts fine in 20 degree weather. I would never actually drive it in those temps, but I did want to see if it would start and idle ok in those temps. Initially it would pop right off and rpm's would jump right up to 1200 then die. I added time to the initial start up air flow and gave it the base running air flow it wanted in those colder temps that I hadn't been able to log previously then it was fine. I think it's normal to run rich for a little bit at start up in those cold temps then it drops down to 15.2 AFR and idles nice at 825 rpm.

This is my first ever attempt at doing my own tuning. It's a small miracle I haven't broke this motor yet LOL. I feel like I've learned a lot already and hopefully by the time I buy a forged motor I'll be a decent tuner.

 

Yeah, it sounds like learning to tune is a long, tough, but VERY worthwhile process, and I'm sure the result of a smooth-running, strong engine makes it all worthwhile!

 

Shop labor costs and the fact that it's a 5 hour drive in any direction to a reputable tuner convinced me to start doing my own work. If I had a mountain of money and lived closer to a good tuner then I'd let them have it

 

+1 I agree.

And, you are making several understatements in your sentence.

 

From what I have gleaned from these pages, of that I have no doubt! lol

 

Even a tune from the very best professional is only as good as what you pay them for. Most people pay for an hour or two of shop time, and if they are lucky, they get a pretty good tune. In order to get the level of tuning from a pro that you can learn to do for yourself would require days or weeks of tuning through multiple weather conditions, and the cost would greatly exceed the value of your car. This is why you can take a dead-stock OEM vehicle from a manufacturer who has spent untold millions on their tune, and you can usually improve it. None of us are satisfied with the plus or minus 25% corrections allowable from the factory, but that is what you get when the tune has not been developed for your EXACT engine.

 

You wrote: "porcelain is perfectly white with no specs at all so I'm really doubting that there is any real knock".

Despite your stated air to fuel ratio numbers, a "perfectly white" spark plug porcelain would indicate a quite lean condition. My guess would be that your cylinder head temperatures are somewhat hot and I'd be a lot more comfortable with some brown tan color on my spark plug internal porcelain . . . run it richer . . . and cooler.

Rick

 

From what I've learned already about tuning even though I'm probably still slower than most there is no way pro or not a tuner can cover everything in 4 hours. In fact I believe that the 4 hour tunes I've seen just show how great some of these pro tuners really are. The idle and wot stuff they nail, but there is always something that isn't 100%. We had some near 50 degree weather yesterday so I was able to get some more done. With disabling burst knock and raising the VE table in just a couple spots where I was getting tip in knock I seem to have eliminated the tip in knock. I was actually able to go ahead and add the timing I took out of those areas back in and test again still no knock. Car seems more responsive in those areas now. Those were areas that you just don't run in as common and almost have to hit on purpose.

 

You can't really judge AFR accurately on plugs with a lot of idle/part throttle street tuning on them so I rely on my wideband for that. The part of the plug that shows AFR at wot is actually hard to judge without cutting the plug. It's the part down inside behind the thread area. You can see it by looking closely with a light pointed down in there, but hard to judge that way. You can judge the heat range of the plug by marks on the threads. I do know a little about plug reading from my past using nitrous. My wideband readings in boost above 100 kpa vary between about 10.9 to 11.5 to 1. Initially I had a lean spike first getting into boost, but I lowered my boost enrichment enable point, raised the ramp in speed to 4 which I believe is max, and also raised the VE table just a bit in the 90 to 100 kpa area. Now when I get into boost the AFR drops right down to 10.9 which is a little rich, but it runs good and doesn't bog or stumble or anything. At 6400 rpm I'm seeing 9 to 10 pounds of boost and my injector duty cycle is about 85%. Running deatschwerks dw300c intank pump and 60 lbs injectors on 93 octane with a couple bottles of heat in the tank. Timing drops down to about 9 degrees advance near peak torque and ramps back up to 14 at 6000 and drops back down to 12 at the 6400 rpm shift point. My stock trans will no longer shift at wot. I have not changed anything with the trans or trans tuning since adding the procharger so I believe it's mechanical and just can't handle the power at wot. At any part throttle like 75% or less it shifts fine and doesn't seem to be slipping under acceleration it just will no longer shift at wot. I'm planning to have a built 4l60e put in it by the end of March any way before race season starts.

 

See if this Youtube channel helps.

https://www.youtube.com/c/AndyWhittle_HowEFIworks

Andy

 

try asking your trans to shift faster with less torque management and more line pressure. also you can unlock your converter fulltime which will help absorb a small amount of hurt you're giving your trans

however if its flared lots, good chance its toast

 

Just addressing the OP's question here, since it's really just up to the person on what kind of tune you want to run. Personally, I'm still in SD, but plan on getting back to MAF one of these days. Tried it off and on with a 98 pcm and it didn't work out well. Got a 411 now, might give it another try after I fab a new intake to get rid of some of that heatsoak that curses the f-body.

To go back to MAF:
1. re-enable LTFT's
2. re-enable MAF set fail freq back to stock
3. re-enable DFCO <helps with mileage too
4. re-enable COT.... if you still have those...

Going back to closed loop isn't a bad idea for the street. Helps the PCM in a lot of ways run the car more efficient.

If you have a big cam, you can still have MAF enabled and do a SD idle setup. Just go to your PE settings, set the TPS enable to 0 through about 1200 rpm, and set the map enable under your normal idle map, i.e. 50 or 60 ish for a big cam. Then set your PE eq ratio to 1.0. Then your car will idle in PE mode, at stoich or whatever you tell it to (SD mode, STFT's disabled). As soon as you go above 1200 or whatever you set it to it will go back to using MAF numbers and STFT's.

 

We had the rare 60 degree day yesterday so I was able to take her out for some logs. I've decided to stay SD open loop. The faster IAT relocated to right before the throttle body was a huge plus. The only issue I have now with heat soak is if the car is warm and you shut it off then within a short time start it up again. The idle AFR will go on the lean side, but not dangerous. It comes down immediately though when you start moving.

I'm not getting any KR any where now and really feel like I should put some more timing to it, but I'll leave it alone until I can get on the track or dyno.

I got on it as much as I could with no 4 to 2 down shifts and lifting from wot before the shift point. I tested several "tip in" points no KR. I also went out on the highway in both 55 and 70 mph zones for a while to check cruise AFR. It was pretty much stoich in those areas and I decided to leave it that way rather than tune for a lean cruise. My reason is some of those same cells are where I was getting KR previously on tip in and a tip in from those cells seems more responsive at 14.7 than it was at mid 15 AFR.

After I was done I pulled #7 plug and it looks great no detonation. My timing drops all the way down to 9 in boost then ramps back up to 14 at 6400. Fuel is 93 octane with a can of heet in every 5 gallon jug before I put it in the car. I already want to put a smaller pulley on the procharger and add meth, but I'm going to hold of for now.

I decided to go ahead and get a new converter when I do the transmission. Yank recommended the PAS3400 so I'll probably go with that. Track opens in April so I'll get the trans done in March and should be ready to test to see if it's really making the power I think it is.

 

When tuning VE, IAT can have a huge effect on your numbers. This is because there are no fueling tables that use IAT as a correction for fuel. I guess GM never intended on prolonged SD mode. The reason it happens is because the PCM uses the VE as the calculation for dynamic air, which is a hard number that does not change when you're driving around. This is also the number the PCM uses for calculating g/cyl. Whatever number is on the VE at a certain rpm is what it is. There is no adjustment for IAT.

When the MAF is enabled, though, then the PCM uses actual metered air to calculate g/cyl, and make fueling adjustments. On some PCMs the computer uses both to do this, like gen IVs where VE and MAF are biased based on RPM because VE is more accurate at lower RPM, whereas the opposite is true at higher RPM, so it biases MAF. The last gen IV I tuned I just disabled VE and tuned it for 100% MAF. This is a pretty common practice.

There is a silver lining though, while in SD you can still usually enable the STFT's so your O2's can help with making adjustments for fuel. The air calc still won't change though, and if it's off enough then the O2's will actually be more of a pain than a help.

So what it sounds like on your tune is VE was tuned at lower IAT temperatures. Fuel doesn't mix as well into hot air, and there is less air to mix with (hotter air is less dense, but has higher pressure because it's contained). Couple this with the increased chamber pressure due to heat equals more fuel is required to cool it down. GM accounts for this with ECT. The colder the engine, the more fuel. Also, the hotter the ECT, the more fuel. At operating temp, stoich is the target. Just have a look at a stock OL EQ table to see what I mean.

Moral of the story is heat has a huge effect on fuel, but GM assumes MAF will be used to calculate airmass. That is thier "correction" for heatsoak. What that means for us SD guys is try and tune the VE at temps that the car will most likely see, I.e. normal operating conditions. Either that, or account for it by tuning your idle cells when IAT is very high. This will cause the exact opposite of what you were seeing, as in a lean condition as soon as it starts cooling down, but creep back to stoich as it heats up.

I dealt with that for a while trying to find a happy medium. Without a WB it wouldn't be something you'd notice at all. But when you are a perfectionist, and you can see your afr all out of wack suddenly, even though the car runs great, you tend to look into more, and make unnecessary adjustments. A good friend of mine and I were discussing this recently because he has the exact same issue. We decided that perhaps a "winter tune" and "summer tune" might be the answer. I can say my summer VE table is definitely different than my current one.

 

Internal engine dynamics is a very complicated subject due to the physics involved. Just think as that hot air is coming in, it has more pressure, meaning it's possible that it could put the MAP into another cell, while being less dense at the same time.

Another interesting point is as the IAT goes higher, the PCM will pull timing. Might not seem like a big issue at first, but with aftermarket cams and mods, timing has a bigger effect the actual vacuum the engine is pulling. Less timing, less vacuum which means slower air. As air velocity decreases, pressure increases. So wouldn't it be possible to get into another cell on your injector flow rate? Keep in mind, on that table, more vacuum equates to less fuel. As the MAP kpa goes up, (closer to baro = less vacuum) the flow rate is increased. This would have the greatest effect at idle.

I try and learn something new everyday. This is a neat topic and there is a ton to learn about it. I haven't even got into the effects of heat and compression, and it's already pretty complicated.