quick question on a SD tune vs. a MAF tune.
quick question on a SD tune vs. a MAF tune. 99 Trans am. Just a full bolt on car with a 3600 stall. Ported fast 92, PTM 95mm tb and will be installing a FTP 98 mm lid. I know a MAF tune is more precise so I'm leaning towards a gm 85mm maf and tune it that way. I'm pretty sure the stock maf is going to restrict the air flow. Is it worth it to go SD and delete the maf? Or just stick with a maf for now? Any input would br much appreciated.
99 Trans am. Just a full bolt on car with a 3600 stall. Ported fast 92, PTM 95mm tb and will be installing a FTP 98 mm lid. I know a MAF tune is more precise so I'm leaning towards a gm 85mm maf and tune it that way. I'm pretty sure the stock maf is going to restrict the air flow. Is it worth it to go SD and delete the maf? Or just stick with a maf for now? Any input would br much appreciated.
Maf isn't more precise whatsoever...
however in your case, both sensors are not better than the other.
Your setup has nothing that would require a speed density tune. Stick with the truck MAF.
SD could be an option in the future depending on how often you drive your car. I'd say if you ever went Heads/cam you MIGHT prefer Speed density. (and I'm not saying all H/C cars need SD either) but as of right now, you don't really need it.
Man, I could sure debate a couple of points in the above opinion! LOL
With an internally stock engine you wasted money on that intake and TB.
An 85mm MAF is more than enough. Leave the "screen" in it.
With an internally stock engine you wasted money on that intake and TB.
An 85mm MAF is more than enough. Leave the "screen" in it.
I agree with Ed. There is inherently more error or more room for error based on how the Speed Density equations are derived compared with the MAF transfer function.... so saying that the MAF isn't more precise is highly debatable.
Launching!
Joined: Oct 2012
Posts: 258
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From: Canada
MAF actually reacts much faster than the MAP. It also allows for huge swings in elevation, while maintaining a consistent delivered AFR, when both are in play. I am a firm believer in using both, the MAF and the MAP. Greg Basnish, GM EFI Calibrator, has written an excellent book entitled "Advanced Tuning Techniques". Read what he has to say about how GM Modules handle the MAF and MAP functions, you may be very surprised how it actually works!
This I disagree with this.
If you look at the GM code for SD vs MAF and when both are referenced under what conditions, the SD is looked at first during transient events because its calculated which is a faster reference than getting a frequency input from the MAF sensor to determine g/sec.
If you look at the GM code for SD vs MAF and when both are referenced under what conditions, the SD is looked at first during transient events because its calculated which is a faster reference than getting a frequency input from the MAF sensor to determine g/sec.
I agree that you have a lot of money wrapped up in on the top end that could have been achieved by an LS6 intake, but maybe you're planning ahead for the future....
Both MAF and SD have their advantages and disadvantages. I usually tune every "stockish" car in SD, then I tune pure MAF even though it really doesn't need much help in the VE table. When I'm all done, I just return the car to the factory VE cutoff of 4000 RPM and end up with fuel trims of -2 to 0 and WOT AFR of 12.8ish.
When you get into cars with a really big cam, I have had good luck going with either one or the other. With the reduced amount of vacuum, I have found that the VE table and the MAF will fight each other causing bucking/surging in some cases. I usually lean toward using SD in these situations, but MAF or SD alone are not as good as both together IMO. GM used both for a reason. In boosted applications, it's clear that SD is by far a better option because many will go near or above the accurate region of the MAF sensor.
Both MAF and SD have their advantages and disadvantages. I usually tune every "stockish" car in SD, then I tune pure MAF even though it really doesn't need much help in the VE table. When I'm all done, I just return the car to the factory VE cutoff of 4000 RPM and end up with fuel trims of -2 to 0 and WOT AFR of 12.8ish.
When you get into cars with a really big cam, I have had good luck going with either one or the other. With the reduced amount of vacuum, I have found that the VE table and the MAF will fight each other causing bucking/surging in some cases. I usually lean toward using SD in these situations, but MAF or SD alone are not as good as both together IMO. GM used both for a reason. In boosted applications, it's clear that SD is by far a better option because many will go near or above the accurate region of the MAF sensor.
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Guys at SLP told me the 85mm truck MAF flows right at 1000 cfm ("screen" still in it) on their bench. So, if you think you have something so bad-assed that would need more than a Holley Dominator carb, you need something else. Won't be an NA 5.7L or 6.0L engine.
FormerVendor
Joined: Nov 2012
Posts: 390
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From: Dyno Tuning in KY
Ed you are completely right. I did this test on my 403 with a 85mm MAF meter. Now granted I was running out of frequency on the table it was still not a flow hinderance. I still made as much power and went just as fast at the track with or without the MAF meter.
As far as one being more accurate than the other, a SD tune isn't anywhere as accurate or consistent as compared to a MAF tune... what most people don't understand is a properly setup MAF tune REQUIRES the underlying SD tune to be setup as well. So when you get a MAF tune at my place you get a SD tune as well as a MAF tune because they are both calibrated. You could unplug the MAF meter to fail it and it would run in SD just like any other shops that would perform a SD only tune. So if the VE (main SD airflow table) isn't adjusted and you are running MAF only then you just basically got a half assed tune.
As far as one being more accurate than the other, a SD tune isn't anywhere as accurate or consistent as compared to a MAF tune... what most people don't understand is a properly setup MAF tune REQUIRES the underlying SD tune to be setup as well. So when you get a MAF tune at my place you get a SD tune as well as a MAF tune because they are both calibrated. You could unplug the MAF meter to fail it and it would run in SD just like any other shops that would perform a SD only tune. So if the VE (main SD airflow table) isn't adjusted and you are running MAF only then you just basically got a half assed tune.
a SD tune isn't anywhere as accurate or consistent as compared to a MAF tune... what most people don't understand is a properly setup MAF tune REQUIRES the underlying SD tune to be setup as well.
The more sensors there are, the more consistent it is over huge variances in weather and altitude. However, in a relatively constant world (as in you don't travel to the top of the Rockies then back down to sealevel or don't travel from the Sahara desert to Alaska) either one or the other (including SD) is more than fine at adapting to weather changes.
FormerVendor
Joined: Nov 2012
Posts: 390
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From: Dyno Tuning in KY
There are alot of filters and coefficients in the operating system that allow you to make the stock blended MAF/SD tune work every way as good as a pure SD tune. However thats not to say a SD tune wont work but I always ask my customers this question... if you were chopping wood do you wanna chop it with an arm tied behind your back or use both?
Just because it REQUIRES twice as much work (tuning the ve AND maf tables) doesn't mean it's that much better.
The more sensors there are, the more consistent it is over huge variances in weather and altitude. However, in a relatively constant world (as in you don't travel to the top of the Rockies then back down to sealevel or don't travel from the Sahara desert to Alaska) either one or the other (including SD) is more than fine at adapting to weather changes.
The more sensors there are, the more consistent it is over huge variances in weather and altitude. However, in a relatively constant world (as in you don't travel to the top of the Rockies then back down to sealevel or don't travel from the Sahara desert to Alaska) either one or the other (including SD) is more than fine at adapting to weather changes.
You can get a SD tune close to handle all the situations. Perfect? no.
My personal cars are OLSD with no knock sensors. Been daily driver/race cars for a long time and I do not tune or even log them. So it can be made to work just fine. Of course I only suggest OLSD on huge cams or high boosted cars.
My personal cars are OLSD with no knock sensors. Been daily driver/race cars for a long time and I do not tune or even log them. So it can be made to work just fine. Of course I only suggest OLSD on huge cams or high boosted cars.
if you were chopping wood do you wanna chop it with an arm tied behind your back or use both?
The only way to get those correction tables right is to have the vehicle in all those different weather conditions to dial in the corrections. Can you do that in one day in a shop, or driving on the street that day? I hardly think so. Can you do it with a spread sheet? I hardly think so.
And at the same time, I would imagine that even a blended tune will also need some variation for the different conditions just like the SD. Really doubt you can estimate and do a blended tune at sea level in the summer and accurately account for what it's going to be like at 6000 feet in the winter.
If the blended tune is so adaptable that it can be a one and done type of tune without any sort of touchup later on for different conditions and variables then there would be no need for different tuners and settings. There would be 1 tune slapped on all cars and from then on the tune would just "fix itself".
FormerVendor
Joined: Nov 2012
Posts: 390
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From: Dyno Tuning in KY
That's a good analogy, but it's a little extreme. That's because an act like chopping wood would be exponentially harder with 1 hand vs. 2. But in reality, a tune using just 1 of the available choices (sd or maf only) is only marginally worse than using both. It would be like saying "if you were jerking off, do you wanna do it with 1 hand tied behind your back or use both?". Yeah 2 hands may be slightly better, but doing it with 1 hand is beyond plenty for most people.
From my personal experience, I've found that MAP is better for low airflow situations like cruising around and idle in addition to boost as most MAF sensors run out of Hz. At WOT, no matter how much I try there are always little variations to the AFR running SD that I cannot tune out. Once I plug the MAF back in the AFR is DEAD solid at high flow rates.
This is why I like the hybrid approach GM used. You get the low flow accuracy of the MAP and the high flow accuracy of the MAF. It's not perfect but as long as you aren't running a big cam or boost there is no reason to not run both.
I will tell you that my 102mm housing with LS3 MAF only peaks about 8.3kHz with a 12kHz (I think) ceiling. There is a bit of resolution lost due to the 102mm size. A LS3 MAF with a 95mm housing screened like mine would be perfect for my power. Maybe even the 90mm. That loss of resolution also hurts low speed accuracy. I will also say that a MAP reacts faster than a MAF. The heated wires resistance just cannot swing as fast as a pressure sensor.
90mm would be the biggest I'd go on yours.
This is why I like the hybrid approach GM used. You get the low flow accuracy of the MAP and the high flow accuracy of the MAF. It's not perfect but as long as you aren't running a big cam or boost there is no reason to not run both.
I will tell you that my 102mm housing with LS3 MAF only peaks about 8.3kHz with a 12kHz (I think) ceiling. There is a bit of resolution lost due to the 102mm size. A LS3 MAF with a 95mm housing screened like mine would be perfect for my power. Maybe even the 90mm. That loss of resolution also hurts low speed accuracy. I will also say that a MAP reacts faster than a MAF. The heated wires resistance just cannot swing as fast as a pressure sensor.
90mm would be the biggest I'd go on yours.
Whats the story on this truck MAF? Flow more than a C5 Vette MAF? 2001 on were 85mm.
MAF vs SD vs Blended......what works best for an auto trans car at the strip? Say for instance when nailing the throttle at 1700 rpm with a 3600 stall?
I am running MAF only, and am thinking blended will help that full throttle transition.
Thoughts?
Ron
MAF vs SD vs Blended......what works best for an auto trans car at the strip? Say for instance when nailing the throttle at 1700 rpm with a 3600 stall?
I am running MAF only, and am thinking blended will help that full throttle transition.
Thoughts?
Ron
