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Advantages/disadvantages of SD?

Old 05-26-2006, 12:08 PM
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Out of curioustly, are you using a wideband to dial in your tables?
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Old 05-26-2006, 12:33 PM
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Originally Posted by silverTA2002
Yeah yeah.....

Say what you will, but when you have the ability to go back and forth between having the MAF enabled and disabled back to back.

And you notice a significant difference in throttle response and low end torque each time........

Would it make everyone feel better if I log the exact time it takes in 3rd gear to go from 2000 rpm to 5000 rpm without the MAF, then do it WITH the maf??
The real challenge would be to find out how much of the time difference (as there certainly ought to be one) is due to the tuning, the road, surface, the ambient conditions, the driver, etc. And then, if it is purely tuning alone, to convert what kind of loss/gain in "power" in relation to the time disparity of acceleration there is.

For instance, let's say it took you .3 seconds slower to go from 2000 to 5000 rpms b/w the 2 modes, could you say that you lost 10, 20, 30 horses??? how about 2, 3, or 4? Now, if you were let's say 3 whole seconds slower in the rpm range, well then that might be something to raise a brow at (assuming both modes are tuned to a point of marginal error swing from "perfection"). If you do decide to do this, keep in mind that 1 or 2 runs won't prove anything, do it 10 times each, as to compare many different samples and also, keep everything outside of the tune itself as consistent as possible
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Old 05-26-2006, 12:33 PM
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Originally Posted by silverTA2002
Would it make everyone feel better if I log the exact time it takes in 3rd gear to go from 2000 rpm to 5000 rpm without the MAF, then do it WITH the maf??
Do it, go from a 2000 roll with each, log the rpm and speed and tps as well as AFR and timing and post the logs up on hp tuners and link it in here.

Make sure you do it on the same road, make sure the AFR is the same for each run as well as the atm. conditions
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Old 05-26-2006, 12:34 PM
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Originally Posted by Black02SS
Out of curioustly, are you using a wideband to dial in your tables?
No. I don't own one.

Here's my "scientific" MAF vs. MAFLESS wot results.

3 runs with MAF enabled 1800 to 5200 rpm in 3rd gear: 76 cells, 79 cells, 81 cells (slight KR on this run). 1800-4000 3rd gear: 50,52,54



2 runs with MAF disabled 1800 to 5200 rpm in 3rd gear: 78 cells, 81 cells
1800-4000 3rd gear: 51, 53

What's this tell me? at WOT throttle, there is little to no difference between MAF and MAFLESS.

Some differences between the logs:
Dynamic cylinder air at WOT:
Maf- .59 to .76 g/cyl
Mafless- .66 to .80 g/cyl

o2 readings:
MAF- 890-920
Mafless- 900 to 960

measured Timing:
Maf- 24.5
Mafless- 23.5

Inj pulse:
Maf- 14.9 to 17.8
Mafless- SAME


Part throttle SOTP differences. More delay at 2k when you hit gas 50% throttle or less with MAF. Also, acceleration isn't smooth, especially from 1k to 3k , it's jerky.


I dunno, maybe I'm crazy and should keep the MAF.

What does it mean that my dynamic cyl air is LOWER for the MAF run than the MAFless one?

I should note one thing. The biggest throttle response differences between MAF and MAFless occured when I had brand new o2 sensors put in. But, for some reason, my bank 2 sensor keeps going bad. Not completely bad. But, brand new, and bank 1, bounced between 70 and 700 mv at idle. Bank 2 (after being in for a couple weeks) bounces between 200 and 500 mv only at idle. No exhaust leaks that I can find. And each time I put a brand new sensor in, it bounces fine.

I'll drive for a little while longer with the MAF enabled and see if the SOTP difference is there now with my halfway ok o2 sensor.
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Old 05-26-2006, 12:36 PM
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Old 05-26-2006, 12:41 PM
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Originally Posted by silverTA2002
What does it mean that my dynamic cyl air is LOWER for the MAF run than the MAFless one?
Nothing, the DCA is derived from the main airflow calc, so this could just be the difference in what your VE airflow calc is vs your MAF calc, this is why if you have one known airflow model to be in very good standing, and you clone the 2nd one after it (as accurate as possible), you should have essentially the "same" airflow model.

And no you are not crazy, I think i've said this before, the mind is a very powerful thing, if you have the conception that SD mode is just hands down better, the minute that MAF comes off, you've already got it in your mind that is IS better. The more data we can come up with, the more we'll be able to paint a truer picture of what is going on here
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Old 05-26-2006, 12:47 PM
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Originally Posted by silverTA2002
don't stress it, if you like SD, then stay SD, won't hurt a fly. Tune it so that you feel (and see through results) your car is running the best it can, then be merry. Just don't go telling everyone that your car runs better than theirs b/c it's in SD, instead, tell people that you are running SD b/c you like the methods of tuning and that is just your preference. This is what this whole argument is about, trying to get people out of the conception that SD mode is something necessary to reach optimal operation.
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Old 05-26-2006, 01:04 PM
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That's the thing, my "preconceived notion" was that there's no difference between MAF and SD.

Only when the car felt faster with SD, did I leave it there for a while. I spent lots of time trying to get the MAF right. I WANT to keep my Maf.

I dunno, maybe I'll give the MAF another shot.
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Old 05-26-2006, 01:07 PM
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I honestly know what my REAL problem is. No wideband.

Without the wideband the VE table has proved easier to tune than the MAF.

Next weekend there's a dyno day, $40 for 2 pulls with wideband. I'm going to use that to see where I am for full throttle.

As far as this part throttle nonsense goes. I'm just going to use my next round of cash to buy the Posi and 4.11 gears for the Moser 9" I have sitting in the garage. That should "fix" my low end tq "problem."
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Old 05-26-2006, 01:36 PM
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in the "floor it, plugged and unplugged" test he proposed, if both the SD was tuned right, and the MAF was tuned right so they have identical AFRs, spark, ect...



...the results should be exactly the same. any diff would be, by definition, test error.

i believe where the "better" comes in is during transient conditions. part throttle. idle. areas where one would see a disadvantage from a system.
a static WOT blast tells us nothing.
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Old 05-26-2006, 02:44 PM
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Originally Posted by MrDude_1
in the "floor it, plugged and unplugged" test he proposed, if both the SD was tuned right, and the MAF was tuned right so they have identical AFRs, spark, ect...



...the results should be exactly the same. any diff would be, by definition, test error.

i believe where the "better" comes in is during transient conditions. part throttle. idle. areas where one would see a disadvantage from a system.
a static WOT blast tells us nothing.
Well all most are worried about is WOT, you dont run at the track 50% throttle lol. So why even care?

Get a wideband and then tune the car, then let us know how it feels.
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Old 05-26-2006, 02:46 PM
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Originally Posted by silverTA2002
No. I don't own one.
..........

Some differences between the logs:
Dynamic cylinder air at WOT:
Maf- .59 to .76 g/cyl
Mafless- .66 to .80 g/cyl

o2 readings:
MAF- 890-920
Mafless- 900 to 960

measured Timing:
Maf- 24.5
Mafless- 23.5
You just listed yoru problem, get a wideband and fix the tunes.
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Old 05-26-2006, 03:25 PM
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Originally Posted by WS6FirebirdTA00
Well all most are worried about is WOT, you dont run at the track 50% throttle lol. So why even care?

Get a wideband and then tune the car, then let us know how it feels.
well, if thats all you care about, then theres no debate. alpha-N, SD, MAF, mechanical, and even carb, all operate identically at WOT when tuned properly.



btw, i agree that its impossible for him to have anything remotely close to a accurate test, without a wideband.
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Old 05-26-2006, 04:12 PM
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Originally Posted by WS6FirebirdTA00
Well all most are worried about is WOT, you dont run at the track 50% throttle lol. So why even care?

Get a wideband and then tune the car, then let us know how it feels.
WOT isn't what I'm worried about. In the end, either way, I'm going to a dyno to get my A/F dialed in perfectly. That can be done SD or MAF. I go to the track about once or twice a year. I use 50% throttle or less all day. I LOVE the feeling of gobs of torque when I hit the gas in any gear.

$$ is limited right now. I need a clutch real soon (probably LS7 kit), and I'm going to put the money into the 9" rear in my garage. I may get a wideband eventually.

In case anyone still cares how my car "feels." This afternoon with MAF hooked back up, I couldn't tell a difference between that and the SD.

So, I guess now I'm keeping the MAF. And I'm going to get the WOT tuned at the dyno next weekend.
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Old 05-26-2006, 04:16 PM
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Originally Posted by MrDude_1
in the "floor it, plugged and unplugged" test he proposed, if both the SD was tuned right, and the MAF was tuned right so they have identical AFRs, spark, ect...



...the results should be exactly the same. any diff would be, by definition, test error.

i believe where the "better" comes in is during transient conditions. part throttle. idle. areas where one would see a disadvantage from a system.
a static WOT blast tells us nothing.
The results are basically the same in the test.

They should be at WOT (both tuned properly).

The transient conditions is definitely where I was "feeling" the difference before. But, for some reason or another, I don't "feel" that difference now.

Without a wideband, it's all just guesswork using fuel trims. At least I've got them close. I think I'm just getting "lucky" when the car feels faster.
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Old 05-26-2006, 04:23 PM
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Originally Posted by silverTA2002
The results are basically the same in the test.

They should be at WOT (both tuned properly).

The transient conditions is definitely where I was "feeling" the difference before. But, for some reason or another, I don't "feel" that difference now.

Without a wideband, it's all just guesswork using fuel trims. At least I've got them close. I think I'm just getting "lucky" when the car feels faster.

fuel trims dont work at WOT.
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Old 05-26-2006, 04:38 PM
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You cannot dial in your part throttle on the dyno, you can get it close if you spend all day on a load dyno but the way to do it is with a WB on the street...
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Old 05-26-2006, 05:16 PM
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I've really appreciated this thread. I was out of the scene for a bit (maybe 8-10 months, being too busy with work and such), and suddenly I'm reading all this stuff about SD tuning, going MAFless, etc...

I've always found tuning for WOT pretty darn easy using the MAF table in my primitive 5-6 year-old-never-updated LS1 Edit. Bang on with the dyno and a wideband. I started seeing all these threads on SD tuning, so I wanted to investigate more (in case I was missin something), but everytime I tried to search the issue, the search would not go far enough back for me to learn anything. So that left me with a WTF feeling about this new tuning process. I'm glad this thread has helped shed some light on the subject. It hasn't gone into a lot of tuning detail per se, but it has looked at the issue somewhat.

I'm certainly happy with my MAF (even my Granatelli), though I'm not hardcore by any means, imo.
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Old 05-26-2006, 06:12 PM
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Originally Posted by MrDude_1
fuel trims dont work at WOT.
I know. WOT will be fine tuned on the dyno.

I got my VE table close using STFTs above 4000 rpm.

I disabled OLFA (1.0), set PE enable to 80map and 80% TPS. You can get most of the table (80 and below) this way.

Then, I used hand smoothing and "trends" to determine as close as I can how the 80+ Map cells should look.

But, for WOT, VE, MAP, PE..... all means to an end right? As long as the A/F is 12.8 at WOT in the end, does it matter if your commanded and actual A/F are exactly the same?
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Old 05-26-2006, 06:23 PM
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yes, your commanded and actual need to be the same
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