I'm trying to find a performance Mass air flow sensor..My definned,descreened, 3" MAF is choking my 406.. anyone have any ideas???

 

Choking? Impossible. What are your MAF readings throughout....?

 

You could convert to speed density.

 

Its more likely your 3in catback is choking your 406.

 

Why? You only need resolution at part throttle, you can use the PE tables for tuning WOT....

 

I'm just wondering why my power is falling off after 5400RPMs??? The cam should make power 2300-6500RPMS..Mods in sig

 

TTT

 

look at this .http://www.superchevy.com/technical/...t_results.html

 

Mass Air Flow Sensors

* Stock TPI Bosch MAF sensor w/ screens -- 517.8 cfm
* Stock TPI Bosch MAF sensor w/o screens -- 658.4 cfm

Here is the link to the above information.
http://dtcc.cz28.com/flow/
If you think 658cfm is ideal for a 6000+ rpm 406 cubic inch engine, then I got nothing else to say.

TPI-Formula350,

I helped my nephew with the tuning of a custom MAF meter. He cut the sensor and electronics from the standard tube and mounted it into a 4" tube. It changed the flow per volt output characteristics by a factor of about x2.1

Tuning/rescaling of the ecm is pretty major. Simply rescaling the MAF tables does not work well because you now hit the 255 g/s limit at less than 2.5 volts output from the MAF meter. So basically is what I did was create a custom xdf file for tunerpro to rescale all the MAF reading and the injector size by the x2.1 factor. I also changed the LV8 conversion constant to shift it to get everything based on load back in line. The end result is the ecm limit is now 535 g/s. At that point you are ready for normal MAF type tuning.

Good Luck
Al

 

.... and apparently you don't have anything else to say. The stock 255 g/sec MAF sensor has propelled quite a few Grand Nationals running the stock '7148 ECM into the 8's in the 1/4 mile, and at 30-psi of boost, their cubic inch displacement is WELL OVER 406 cubic inches of displacement. It is all about tuning the PE tables at WOT, as resolution is only meant for part throttle. Get this in your head, it DOESN'T MATTER what the MAF tables are reading in PE, its how you tune for it, because in PE the ECM is in Alpha-N mode.

 

The only way to know for sure is to see the datalogs, otherwise it is all just speculation. You can have the biggest cam and the best flowing heads in the world, with or w/out MAF, but if the timing and fuel is getting pulled in your upper RPM's, it's going to fall on its face. Again, the MAF isn't your problem, it flows a great deal more than just 450-cfm, way past your 0" of vacuum, naturally aspirated. The MAF can flow upwards of 30-psi off boost, do you have any idea how much forced air that is? The 255 g/sec is an ECM limitiation, not a MAF limitation, as it is meant for part throttle. Again, you can flow as much air as you want through your MAF, it is the ECM that is limited to 255 g/sec, and after that, you tune the PE tables to compensate for fueling....

 

You are kidding right????

TPI-Formula350 asked about a MAF meter that could flow more air since as I posted the stock sensor has been measured to flow about 658 cfm with the screen removed. This has nothing to do with its measuring capabilities. It is strictly a flow characteristic of the meter which can be used to indicate when it will present a restriction based on the engine air requirements. Spouting number from GN at about 2 bars (30psi) is totally irrelevent because the equivalent flow characteristic of the MAF meter at 2 bars would be more like 930 cfm.

My comment about if your happy running the engine with a meter capable of 658 cfm was strictly meant that then there is no need to consider any changes I was suggesting. However, many would consider 658 cfm a pretty serious restriction in this case. So.... then it is either go to SD or if you prefer MAF then doing something such as I was suggesting to TPI-Formula350.

Have a nice day!!!

 

You simply do not comprehend the limitation found in the ECM, nor it's relevance. First of all, 2-Bar DOES NOT equate to "30-psi", it equates to 15-psi, as 30-psi is 3-Bar. So right there you have it flawed. Secondly, the '7148 found in the turbo regal's is CAPPED at 255 g/sec, it is a limitation in the ECM, not in the MAF, just like the TPI ECM's. The whole point was that the stock MAF is capable of more than enough airflow, period, end of discussion. If the OP doesn't change the PE tables in Alpha-N mode, then the look up tables will remain in the factory's calibration of the stock engine, and nothing will be gained, and THAT is why the engine is falling on its face. I have to literally laugh out loud when I read posts that imply the stock MAF runs out of resolution, especially after seeing a solid "fifteen" MAF reading at part throttle on the scanmaster. Lemme help you out, when 255 g/sec is reached at WOT, fueling is not stopped, it just seizes to rise, and that is because of three things, the factory look up tables, fuel pressure, and injector size. Up the fuel pressure, and this will help some. Alter the stock PE tables, and the fueling will begin to compensate up top. If the injectors go static, then get larger ones....

Again, the stock MAF is not the restriction, the factory calibrated ECM is. When a Grand National see's boost, the ECM limit of 255 g/sec is reached almost instantaneously, so how does the ECM compensate for fuel afterward when the MAF is allegedly maxed out, and after the stock 15-psi limit has been passed? The same exact way our's does. This is where the "RELEVANCE" falls into play, and your not understanding this. In PE mode (WOT), resolution means absolutely nothing, nada, zilch, whether boosted, or naturally aspirated. The ECM can calculate air up until that point, but once your ECM is pegged, you tune the PE tables, and the ECM WILL adhere to the new calibration, it has no choice....

 

255 g/sec = 450 cfm. Watch the MAF tables with a 406, and tell me where they are at WOT throughout the RPM scale, take that data and show me how the stock MAF's cfm rating is somehow not enough....

 

406 C.I. 11.8 Comp Ratio, Weisco Forged Pistons, Lunati Forged 5.700" Rods, Plasma Moly Rings, TPIS 242/242 .610 lift Solid Roller, Comp Cams Solid Roller Lifters, AFR 190's, Accell Base and Super Ram P&P, Pro Magnum 1.6 RRs, Hooker Super Comp Headers, Taylor 409 Race SP Wires, NGK V-Power FR5 SPs, Wide Band O2 sensor, Pro-Built 700-R4, Vigilante 3200 Converter, Dana 44 3.07 gears, M/T slicks, Full weight car 3450#, and through pipes and mufflers....

Best Times with 406:
60'-1.48
1/8 - 6.96@ 97.51 MPH
1/4 - 11.02 @ 123.57 MPH

.... and stock Ported MAF.

http://temp.corvetteforum.net/c4/ski.../vids/run2.wmv

 

Here is the formula:

CID X RPM X VE

CFM = ---------------

3456

Do the math. You will see he is running up against the flow capability of the MAF sensor.

 

stock MAF here with no screens on my 383 through stock TPI air lid box and gutted filter boxes with homemade ram air ran 11.4's at 118-119mph in the summer heat. HIT max limit of 255 at 4500 rpm on a motor that peaked closer to 6500 rpm...shift by 6600-6800.

Went to a custom 3.5" MAF setup and CAI setup... didnt gain a thing, only matched my best...granted i didnt dyno tune this setup only tracked tuned/street tuned it back to the same air fuel ratio.

Point is, I dont think his motor is being choked too much by stock gutted screen MAF and the amount of work to retune the ecm isnt worth it IMO.... just going by my results

 

Now that is irrelevant! I asked you for real time data showing where the MAF resolution is in terms of RPM scale, and you throw an equation at me to justify your position? I also provided a proven 406 w/stock ported MAF, and .600" plus lift, trapping in the 120's, running low elevens, and can also provide another one running the stock ported MAF who is in the tens if you'd like, do you honestly think that the equation you posted pertains to their particular setups? Nope, too many variables. For you to think that an individual intake valve can somehow outflow the air coming through the MAF sensor is laughable at best....

 

Exactly. The 255 g/sec is attained, ECM resolution threshold is reached, Alpha-N mode activates using stored look-up table in which bases pulse width on TPS/RPM. With larger engines you obviously want to command more of a VE in conjunction with SA, but if you don't change the values in the PE tables with over 50 additional cubic inches of displacement, your not getting enough fuel because Alpha-N does not measure air....

Larger MAF's will of course always have the potential to flow more air, but the key thing here though is when the engine is calling for it. There are so many examples of members swapping to SD from MAF, which resulted in not only running slower, but now have to deal with changing the values throughout, not just in PE....

We would have to see his datalogs to verify this....

 

Orr89RocZ, Thanks for jumping in here. I was aware of your results because you were working on this at much the same time as we were. It would have been nice if you had completed the tune, but I agree even then I think the benefit may have been marginal.

We did in fact take it one step further to rescale everything to get around the g/s limit but without changing the 8 bit resolution. However, we have NO dyno or track results either before or after to say if any of this actually provided any benefit.

As I said before, I really did not wish to get into this type of discussion as to whether the OP should do this or not. The numbers are there, you determine if you need to or want to try improving on the MAF sensor and eliminate it as a restriction. Orr89Rocz has provided his opinion as someone who has also tried this and I fully agree with the comments he made.

I do not know why people on this board can not have a rational discussion on how to improve on the MAF system for these cars/ecm. When I reseached this, mostly you find threads that deteriorated into this same issue as to whether or not it should be done, needs to be done, and why not go SD with an end result people getting banned. As a result, little advancement has been made in this area and those of us who have actually done work to try to improve on the MAF/ecm are reluctent to post and share how this can be accomplished.

I am done with this thread and apologize to TPI-Formula350 for assisting in the deterioration of this thread. If you decide to pursue this feel free to PM me and I will try to provide what assistance I can.

Have a nice day!!!

Al

 

You have provided absolutley nothing in terms of any performance gain. What have you done, other than "suggest" that he abandon his existing setup ($$$$), then you imply that others, who are ENCOURAGING him to stay with what he already has because the MAF has been proven over and over again, as actually deteriorating this thread? Then you have the audacity to end it with "PM me", as if you have some sort of secret that you only wish to share one on one. Please, get over yourself. The MAF is more than capable to get him where he wants to go, and if he wants more than what was already accomplished with it, like say, he's wants to go nine's, then he can simply upgrade to a larger MAF, and there are an abundance to choose from, simply redo the tables. Anything else....?

Edit: Here, if your unhappy with the stock MAF for some reason, then simply upgrade it....;

 

The reason I suggest he stay with the stock gutted MAF for now is because his motor hasnt performed anywhere near where it should and did suffer a engine failure. I cant recall if he has this motor running again but his setup is somewhat comparable to my old 383 with few differences... He has superram compared to my HSR which will pull higher rpms than superram so his fueling will be different. He has a 406 motor so he is gonna need different tune compared to my 383 and I feel my cam is a touch larger than what he is running.

He has tried my 383 bin file and it didnt run great on it... too rich i believe. In fact I have had many guys with 383 motors request my bin file and have yet to see one of them run right on my bin not sure why that is as alot of these motors are very similar in power/specs.
He should comment more on how his motor ran on my bin as well as others he has tried. Based on that, i suggested he work the tune and get that motor running at its best using the stock MAF and THEN pursue larger MAF if he feels its a restriction. That combo should be making much more power than it was making and i feel it was just a tune problem not necessarily a MAF problem.

My motor has made 400whp through an automatic with the MAF. Another superram 383 here just made 394whp/407wtq through stock diameter MAF. Lots of power can be made through the MAF, but its all PE mode enrichment thats doing the fueling... much like a electronic carb, your adding fuel manually through PE mode, computer is no longer calculating anything with the MAF. 255 gm/s can be reached very quickly... however PE mode and larger injectors can easily account for the extra fuel required.

So is there an advantage in going to a larger MAF and rescaling/reprogramming the code to get around the 255 g/s limit? I dont think there is. Its just a case of 2 ways to do the same thing, get around the 255 limit or just use PE mode to add fuel.

The best advancement I've seen in MAF systems is the addition to Wideband o2 sensor input to control closed loop. You can now log your runs and watch wideband reading and compare to LV8/RPM/MAF values to dial in your tune. I have wideband input on my code $59/730 3-bar map setup and its awesome! Makes tuning much easier when you have a log file with air fuel mapped on there.

 

If Bauer was aware that you were running a MAF sensor, which I'm sure he was, then that is more than likely the main reason why he took it easy on the cam specs, while tyring to maximize the area under the curve for the MAF sensor, and keep it drivable. Pulling the MAF for SD, using an analogy, is very much like swapping from a TPI setup to an HSR. You don't necessarily make more power, you just moved the power higher in the RPM band, and it still needs to be tuned for. The problem with most MAF users is they're constantly looking at peak horsepower numbers when they swap to a better breathing intake, while ignoring the average power the MAF was initially designed for. The 255 g/sec limitation was a design from the factory because the stock LB9/L98 didn't need any more back then for what it was, but they eventually doubled it to 510 g/sec later on, but despite that, the 255 g/sec was never an issue, and still isn't....

 

I dont think I told him what was controlling this motor, the basis of the cam design I dont think would be based on MAF or SD. I wanted X hp at Y RPM and gave him my head/intake/cubic inches combo and the cam came out doing exactly what I said in my email.

That being said, if MAF only flows X cfm and theoretically can support only Y hp, then cam design would have been critical to maximize the MAF's potential. But I've took my motor to 7K on the limiter and didnt see much performance drop. Dyno run was kinda screwy because it seemed to only record to near 6500 rpm but i had limiter set to 7K and he touched it. Power was flat from 6250 to 6500 and looked to keep that flat line. I think it was cam running out rather than MAF not feeding motor.

If larger flow was more important, then my 3.5" should have shown bigger gains at the track regardless of dyno tuned or not, because I took my base dyno tune and scaled MAF til i reached same air fuel ratios as before. car ran exact same in same weather conditions.

 

I'm surprised if he wasn't aware that you were running MAF, unless he just assumed you were w/the '89 ECM. I spoke to him for hours a couple of years back, and he wanted every single detail of the engine. In any event, this just goes to show that the MAF wasn't really a factor w/the displacement. Do you still have a copy of the dyno sheet by any chance, along with the cam specs....?

Actually, cam size is critical in maximizing the MAF's potential, but not because of its flow, but because of the stock ECM in PE mode and simply tuning for 128 blm's across the board. Weather conditions have a horrible effect under Alpha-N mode. Running a MAP based Megasquirt however, in conjunction w/the MAF, would be an entirely different story....

Bingo....

 

If i still have the emails i'll look to see what I sent him...but i do remember telling him i had fuel adjustment up to 6400 rpm and I wanted to be sure I had as much power as i could get by 6300 rpm to have abit of room to provide enough fuel at 6400 rpm to last through the rpm range. I had plenty...

I do have the dyno sheets if you want to see them, as well as cam card pic i believe but i know the specs. 230/245 at .050, 286/306 at .006 advertised. .603/.613 with 1.6 rocker, 109 lsa. Peaked on the chart at 6250 flatlined to 6500 where run stopped. Ran to 6800 at the track and didnt see much loss in ET/MPH if any at all. Strong top end

I'm not sure i follow you here. I ran open loop with my setup and didnt tune for 128, i just tuned for 14.7 air fuel or whatever made the car happy. In the cooler winter months i did notice my tune go rich on the air fuel. So maybe thats because it was in open loop and wasnt using any compensation tables for air mass/temps? But isnt that what a MAF is suppose to do? Is that what your saying, that cam design will influence how MAF reads airflow?

 

I'm sure you did, as that is what I have been saying these lasts couple of posts, that the MAF does not give up after 4500-RPM, the ECM does. Once PE is tuned, the MAF will keep flowing air, and the ECM will keep fueling that flow....

Yes, I just punched in those numbers with a chart that I have, and Bret hit all of the key areas. Curious, what did you run in the 1/8th, and how much speed did you pick up once you reached the 1/4....?

That's what I meant, tuning for 128 (14.7) BLM's across the board. The MAF is more forgiving than SD with cam swaps under transitional load, but only up to a point as far as cam specs are concerned. At PE, Alpha-N has no way to measure the air w/the MAF, so unless your tuning is spot on, you have to take into consideration both the varying weather conditions, and the amount of ethanol in the gasoline. Too radical of a cam will cause a whole load of problems for the average tuner, but if your running both a MAF/MAP based system, it makes it all the more easier to tune for....

Yes, that is what the MAF is supposed to do, but again, because of the ECM's 255 g/sec limitation factor, there is no way to account for the colder air when in Alpha-N (WOT). Alpha-N goes out of calibration when the atmospheric pressure is different from when it was mapped, not to mention, if the TPS setting is skewed, than the look up table's are completely off, especially w/no MAP offset. Not to mention, tuning bigger cams under transitional load w/MAF can be an absolute bear. For the experienced tuner, they could get it close to where it needs to be, and be happy with it, but that is why it is more critical....

 

.... by the way, in case nobody realized by now, the OP is no longer responding to this thread. I'm done. Justin, you have a killer twin turbo setup and I'm hoping to see it very soon. Alvanwie, I apologize for my conduct as work has been a pita lately. TPI-Formula350, good luck w/whatever route you decide to take.

 

I have a 3.5 maf for sale if your looking into that. It has no screens and the fins have been removed for maximum air flow. It works fine, but I had to much trouble tuning it, but it can be done. Here are some pics
https://www.thirdgen.org/forums/engi...1-3-5-maf.html