Why is the speed density considered to be faster than the MAF cars. I mean is it because the MAF is a restriction in the intake. I know it is easier to modify a MAF car without changin the chip because the Speed desity is a little more sensitive to change because of the system of measurement.
Thanks

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86 Trans Am 355 TPI Rebuilt 700R4 with Corvette servo, modified valve body, and a B&M Torque Converter (2000 rpm stall w/ lock up), 87 350 block bored .30 with new crank, bearings, rings, and magnafluxed rods. Reworked 305 heads with 3-angle valve job. Added in the rebuild was an SLP TPI cam, BBK 58mm Throttle Body,SVO 24# injectors,MSD 6A, Hypertech Power Coil, 1.5 Crane roller tipped rocker arms, SLP Intake Runners and Port matching in upper intake including fully ported plenum, TPIS adjustable fuel pressure regulator @ 46psi, Hooker shorty style headers w/ Thermotech heat wrapping, Custom 3” exhaust with Flowmaster muffler and chrome quad tips, Hypertech Thermomaster Computer chip, K&N open element cone filter on modified MAF per TPIS specs, MSD Wires, removal of A/C hardware and a 1LE firewall cover installed. Also there has been a PST front suspension kit with Hotchkis strut tower brace
http://geocities.com/SunsetStrip/Garage/9548/kyle.html

Kills:
95 Talon TSI, 96 Probe GT, 91 T/A L98, 89 RS, 86 Mustang GT, 88 Mustang LX 5.0, 92 Thunderbird V8. couple or ricers that I think were Civics or Preludes not sure what year, 95 Celica GT-S, 94 Chevy 1/4 ton 350, one of those NASCAR F150's ..... **** on Monkie

 

Probably the biggest reasons people switch to SD is that with the MAF system, you are limited to 255 gms/sec on the reading. If you add a blower, increase the cubes or have your engine pull higher rpm, you quickly hit this barrier and the MAF system becomes useless to do its intended purpose.

From what I've been reading in the PROM board, the SD system is easier to burn a PROM for and you don't have this barrier. Lastly, the 165 ecm (MAF) uses a 128 chip whereas the 730 (SD) uses a 256 chip...it holds more information and you can alter more things. The 730 is the preferred ecm for PROM burning on 3rd Gens.

 

Thanks, I will consider this before I get a custom ship. WOuld thi sbe limiting my performance now?

 

Not really, you probably haven't hit the max flow potential of the maf yet, especially if you've gutted it.



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87 IROC-Z, 5.7, auto, 3.27, leather, !cat, Holley fpr, K&N'S, SLP 1-3/4" Jet-Hot coated headers, SLP .218/.224 .495/.502 cam, Comp 1.5 roller tip rockers, $uperPITAram, Edelbrock lower intake, Holley 52mm tb, Dynomax\Flowmaster catback. Coming Soon(?)- Fasttrack/Accell DFI

1989 Pontiac 20th Anniversary Turbo Trans Am - 161,000 miles, !cat, 9" K&N

 

Not to start up the usual MAF vs SD war, but from what I've read, the SD requires the extra memory because it is a more complicated system to calibrate. Whereas MAF can measure and report airflow directly, SD must calculate the approximate airflow based on manifold pressure vs rpm(load). All other performance parameters are then referenced to load. But depending on conditions, load can vary by rpm, or it can even vary at a constant rpm.

IF John Baechtel is to be believed, the difference in calibrating an SD system vs MAF is weeks vs days. Then after hundreds of hours of testing, tuning and programming, the SD's accuracy can be thrown off by something as minor as a change in altitude. Which leads one to question why Chevrolet switched to SD in the first place. I believe the answer is simple economics. At the time TPI was switched from MAF to SD, sales of F-bodies were steadily increasing. If eliminating the MAF meter eliminated $100 from the unit production cost, the savings could easily be in the millions of dollars(over the remaining life of the third-generation f-body production). Yes the TPI MAF meter is a limit to performance and tuning. Which is why Chevy designed a new MAF meter for the '95 - on LT-1 motors.

 

88IROC, the newer MAF is much better (and has even MORE memory). The bottom line is the 165 MAF on the older cars was very limited. It's simpler to tune because you can't modify as much and thus less than optimal results can be obtained.

I've been looking at both with TunerCat and all I can say is, I am sure glad that I got SD. On Third Gens, the SD system is definitely the way to go. The only advantage is the MAF will compensate to a limited degree on mods, but to get optimum results, you really need to re-burn the PROM on MAF. And that's when the MAF shows its inferiority.

Check out PROM burning.

 

I cant add anything else to this thread that hasnt been said, except to correct you. GM went back to the MAF on LT1 engines in 1994.

 

Glenn,

1. I'd already conceded(in my previous post) that the stock early MAF is a limitation. Both because the MAF meter has limited flow capacity and because the ECM cannot respond to it's true flow capacity. And adding an aftermarket MAF meter would increase the disparity between the flow capacity of the meter and the capacity accepted by the ECM. In this regard, the SD system is superior in it's alllowance for increased flow capacity(at the risk of increasing load causing a decrease in resolution).

2. I fail to see how simply increasing memory constitutes a better system. In 1992, my personal computer had 20 Mb of memory and ran Windows 3.1 quite well. Today, my personal computer has 192 Mb of memory and runs Win98 quite well. But today's computer requires the extra RAM to deal with the added complexity of the more modern(?) OS(not sure Win98 would even run with less than 32 Mb of RAM), the increased instruction length and higher memory bandwidth. The point is: as the OS, CPU and the system in general increases in complexity, more memory is needed to carry out similiar functions. A simple spreadsheet designed in Excel 2K would yield no difference in result to an identical spreadsheet in Excel 3. But while Excel 3 could operate quite well with 20 Mb of system RAM(Win 3.1), Excel 2K is designed for an operating system(Win 95/98) which very has poor performance with 20 Mb of RAM. Adding more than 20 Mb of memory to my 1992 system would yield no benefit in performance, thus the system is no better. However, adding more than 20 Mb of memory to my 1999 system releases the added potential of what is a better system. But the fact remains that the 1999 system requires more memory to carry out the same function and to realize it's performance potential. There are several orders of magnitude in difference between a 1985 cpu(early MAF) and one designed in the early '90's(later MAF). Finally, as memory prices continue to drop, it makes more sense to use more memory as a means to carry-out more instructions(newer CPU's have increased memory bandwidth to allow more complex instructions)(in 1992 20 Mb of memory cost me $800., and in 1999 192 Mb of memory cost me $210.). So, of course the newer MAF is much better. The engineers have more powerful CPU's and less expensive RAM to utilize.

3. I have also compared the list of changeable parameters for the two ECM's($32B and $8D) as offered by C.A.T.S. Tuner. After filtering out those parameters that are identical in both ECM files, and the additional transmission parameters offered by the $8D(which after all is designed to control the more complex 4L60E transmission), there is a relatively short list of differences.

Yes, the SD system has more changeable parameters, but almost all are directly related to calculating airflow vs measuring it directly. The Power Enrichment(PE) strategy is a good example of this. Because there is a delay between the time that the ECM detects a change in the TPS and a change in MAP, a temporary correction is needed to prevent an overly lean condition. The MAF system detects the change in airflow much more quickly and can therefore respond without compensating for the delay. In this case, I do not see how the added complexity(i.e. extra parameters) and decrease in accuracy(the SD system is only "guessing" at the increase in airflow) gives SD an advantage. Idle Air Control is another area where SD appears to gain complexity, without adding tunability or efficiency.

Further, although the C.A.T.S. Tuner offers more parameters in the $8D file, I have noticed(after studying a $32 hack) that there are quite a few parameters that have been left out of the $32B file(though I imagine a similiar situation exists for the $8D). Without knowing which parameters were left out, and why they were left out, a comparison list of the differences in ECM files becomes less than meaningfull.

4. I am not about to change to a SD system, to gain dubious benefit for my modest normally aspirated motors(I have three motors utilizing $32B MAF, the most powerful of which still makes less than 275 rwhp). And I wouldn't expect owners of SD systems to switch to MAF if it would add little or no gain in performance. I am investigating PROM burning as a means of increasing the efficiency of all three of these motors, as I believe that: even a completely stock MAF motor could benefit from some "PROM tuning". For me, the best strategy is improving what I already have vs what I could or might have.

 

88IROC, I am not suggesting that someone SHOULD convert from MAF to SD - but explaining why some people do switch from MAF to SD. Not because of the MAF is perceived as a restriction, as the author of this post asked.

Personally, unless I had a serious stroker or an unnaturally aspirated engine, and wanted to have greater ability to tune, I would just work with the MAF system if it was so equipped. And if my engine was "power assisted" I would consider other alternatives along with the switching to the 730 SD.

But if I was chosing between a MAF or an SD Thirdgen car with the intent of modifying, I would chose the SD car just because of its tuneability.

[This message has been edited by Glenn91L98GTA (edited December 28, 2000).]

 

Modern Musclecar makes an adapter box to let you run a lt1 maf on a gn. Is there any reason why it wouldn't work on a thirdgen? I think the parameters are comparable aren't they?



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87 IROC-Z, 5.7, auto, 3.27, leather, !cat, Holley fpr, K&N'S, SLP 1-3/4" Jet-Hot coated headers, SLP .218/.224 .495/.502 cam, Comp 1.5 roller tip rockers, $uperPITAram, Edelbrock lower intake, Holley 52mm tb, Dynomax\Flowmaster catback. Coming Soon(?)- Fasttrack/Accell DFI

1989 Pontiac 20th Anniversary Turbo Trans Am - 161,000 miles, !cat, 9" K&N

 

Glenn,

I know this will sound like beating a dead horse, but you haven't explained(to my satisfaction anyways) why you consider a SD system more tuneable(though it certainly is more complex to tune). Is it based on the changeable parameters in the available ECM files? If so are you accounting for the parameters that can be changed, but are not available in the C.A.T.S. Tuner?

For instance, the $32 PROM has an assigned address(LC01C) for initial advance, but it is not included in the list of changeable parameter for the C.A.T.S. $32B file. Because the default FCB is 17(Val/2.844), it is setup to use the factory initial advance(6 degrees). As one of my motors is setup with 10 degrees initial, changing the FCB to 28 would give me a more accurate advance curve.

I have had the $32 hack for less than two weeks, and have had little opportunity to familiarize myself with all 272 pages of it's contents. Yet I have already noted several parameters I would like to change, which are not included in the C.A.T.S. $32B file. I am not dissing CATS for not including those parameters(without knowing why they aren't included), only noting that I would like to change some of those parameters. I think CATS has done a tremendous job of making available: tuning options, that were previously unavailable to the average owner of an EFI vehicle(and their prices are most reasonable to boot).

The fact that the Buick Turbo MAF crowd is coming up with a list of cars in the 500 - 1000 hp range, says to me that there is abundant opportunity for tuning with a MAF system. The fact that GM is now producing their most powerful engines ever(on a hp/cubic inch scale) while meeting ever more stringent economy and emissions requirements says to me MAF, and not SD, is the more tuneable system(though not necessarily the TPI MAF, which is constrained with mid-eighties technology). Hopefully at some point someone(like Modern Muslecars) will facilitate using fourth-gen parts to improve thirdgen performance.

[This message has been edited by 88IROCs (edited December 28, 2000).]

 

The MAPs system is faster in transistions then the MAFs. The MAFs use a heated wire or foil, and there is certain lagging in how it responds to differences in air flow. The later MAF sensors are a night and day difference from the early ones (I've run both on my GN). The CPU speed is almost mute, they operate so much faster then the engine does. A Senna was alledgedly able to detect some clocking differences in a F1 car some years ago (BTW, a real talented driver)
The weeks to days is nonsense. If you made really serious changes, and need to change the MAF cals, well good luck. The MAP is ALOT MORE intuitive.
I sent the guy who designed the translator a FBod MAF, just there is a list of projects ahead of it. It's not a short list either.

 

Originally posted by Grumpy:
The MAPs system is faster in transistions then the MAFs. The MAFs use a heated wire or foil, and there is certain lagging in how it responds to differences in air flow.

I've read several informed opinions that differ. Again, the PE calculations are suppposedly there to mask the lag between the time when the ECM sees a change from the TPS and when it senses a change in load. Not a concern at WOT when a change in TPS output is not sensed, but definitely a factor at part-throttle.

The later MAF sensors are a night and day difference from the early ones (I've run both on my GN). The CPU speed is almost mute, they operate so much faster then the engine does.

As would be expected, as there is nearly ten years difference in technology advancement between the early MAF's and the later ones.

A Senna was alledgedly able to detect some clocking differences in a F1 car some years ago (BTW, a real talented driver)

I was under the impression that F1 engines used N Alpha(a variant of Speed-Density that supposedly performs poorly at part-throttle). At any rate, I fail to see the relevance. F1 engines during Senna's day were meant to run at between 10 000 and 14 000 rpm. How would those clocking differences affect the average TPI engine that is intended for operation at or below 5 500 rpm?(BTW, a really talented dead driver, who didn't live long enough to learn the difference between how far you could push the limits and when you should push them.)

The weeks to days is nonsense.

I quoted my source - John Baechtel - , perhaps you could enlighten me as to the source of your opinion?

If you made really serious changes, and need to change the MAF cals, well good luck.

After studying the MAF tables, I kind of came to the same conclusion

The MAP is ALOT MORE intuitive.

Putting an engine on a dyno, using manifold vaccuum, manifold air temperaure(air density IS important) and rpm to calculate load, referencing that load to engine displacement to calculate Volumetric Efficieny and then relying on all those calculations to approximate airflow and changes to airflow is intuitive?!?! And then repeat the process any time you make changes that affect the accuracy of your approximations! Why not just make a direct measurement of actual airflow and changes to it, and be done with it?

I sent the guy who designed the translator a FBod MAF, just there is a list of projects ahead of it. It's not a short list either.

That is disappointing to hear. I had planned on sending them an inquiry. Didn't have time today(in the process of moving). May yet contact them for a status update

[This message has been edited by 88IROCs (edited December 30, 2000).]

 

88IROC, I have to call "BS" that it takes "weeks" to learn how to modify the SD chip vs "days" for the MAF. The total time I spent may be "a couple weeks" to learn all about EPROM programming, but that was spending a few hours per day in those couple weeks and it was "generic" about EPROM programming in general. I would have spent the same time regardless or either system.

When I finally got my TunerCat with the 8d.tdf and a 730 bin, I spent less than a couple of hours printing off ALL of the available tables, analyzing them and making modifications to the .BIN. Everything was very easy to understand and it is indeed intuitive. If you understand what Volumetric Efficiency is...that table is very easy to understand.

However, when I loaded the 32B.tdf and a 165 32B.bin, I cannot say the same for those 6 MAF tables. Oh yes, those are REALLY intuitive. Care to explain to me what they all mean?

You and I seem to really disagree on what the difference of ease of use is. You seem to think that if something has a lot of tables (and features) like the SD system, that it is complex. Whereas, if it has only a few tables (and only a few features) that it is easy to use.

I've worked with computers (over 25 years) far too long to accept that. Lack of features means "lack of functionality" to accomplish what I want. I find the inability to make something do what I WANT, harder to use, not easier to use.

Using your own Windows 3.1 vs later version of Windows example in one of your earlier replies, Windows 3.1 MAY appear simpler to use because it has less features. But when I want to accomplish something and the software does not directly support that feature, then it becomes FAR HARDER to do. I much prefer it when the software has additional functionality to allow me to do further manipulation and customization. I can always chose to not bother to read about or use a feature if I do not think I need it. But if I DO need it, then that is a bigger problem.

Maybe your source, John Baechtel required WEEKS to learn how to use TunerCat and manipulate the SD 8d.tdf. But it sure didn't take me.

 

Addressed in above

 

I back up both Glenn and Grumpy in a heartbeat. SD is definitely the way to go for radical NA combinations. It is common belief that the MAF systems adjust to mods better. Well, this is true to only a point. Once you swap out the cam you start running into trouble with the MAF systems (depending on cam size). I very much prefer to adjust the VE tables of the 8D calibration as opposed to working with the MAF tables in the 32, 32B, and 6E calibrations. Much easier. Plus, you never have to worry about an item such as the MAF in the intake stream that can impact airflow.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's after installing Hooker LT Headers and reducing weight.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Im sorry guys I didn't want to start a squabble in here, just wanted to know what all the differences were. I had always heard from Hot Rodders the MAF system was because it was easier to use and it was kinda "Plug and PLay". THough I guess that is true the max performance can come from a MAP system because you can tune it more precisely to your combination. So I think its cleared up for me now.

 

"SD is definitely the way to go for radical NA combinations." Ok, I have no intention to fuel this post, but I am planning a 383stroker that will be blown. Are you saying that MAF would work better for this? The only problem I see with this is that MAF only reads to 255 gms/sec. So, is there some way a MAF system can be modified to read over 255 gms/sec?