another stupid thread about MAFs
02-25-2011, 04:29 AM
#31
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Rogue Tuning!
02-25-2011, 08:26 AM
#33
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I have the SFR MAF and it functions. Under the hood looks really nice. The install is fairly straight forward. Tuning it is a bit challenging and I am still not happy with where my tune is.
SFR does a lot of GREAT things and I certainly don't intend this as a bash, but if I could go back and do it again I'd go Vitesse.
SFR does a lot of GREAT things and I certainly don't intend this as a bash, but if I could go back and do it again I'd go Vitesse.
02-25-2011, 08:43 AM
#34
Race Car
Might as well throw in my 2 cents. I did a lot of tuning on my old car, which was a 2.3L turbocharged Ford. In addition, I also changed the strategy/rewrote the code to install a MAF. I was fortunate in that I had a friend who writes strategy for Ford, and had access to the old data from those processors. ALl I really did was document it, and made changes in the available tuning software so that one could do this without getting into the hex code. The Ford community is a bit different in that it is all open, and anyone with a tuning device can do a MAF conversion the right way.
Note a big point - there is a HUGE difference between "tuning" or "calibration" and "strategy." Strategy is the base code, how things are written, and what the computer does with the inputs. Calibtration is dialing in numbers for those inputs. You absolutely can NOT "tune" your car to a MAF conversion without changing the strategy.
From what I have seen, there are two folks out there who can provide a MAF that was done the same way - Vitesse and Rogue. After having seen folks in the Ford community take off their Pro-M junk because the tune would change any time the weather did, and in some cases, when the engine bay got warm, I would never consider another type of MAF.
The old Ford setup was similar to the 944 stuff in that it used the same air meter. Ford calls it a vane air meter, or VAM, rather than an AFM, but the effect is the same. It more or less measures volume airflow, which the strategy then adds barometric pressure and ambient temperature to to calculate a mass air reading. A MAF system directly measures the MAF. As Sid pointed out, mass is mass is mass. It does not matter what the source of it is, and it does not matter where it is going. That is one of teh beautiful things about a MAF, you can change stuff on your car without having to remap the whole thing every time you do it. Now, having said that, there is a caveat, which is probably what John was alluding to. The efficiency of a turbo will have an impact on the aircharge temperature. That will affect your MBT (Minimum timing for Best Torque). So yes, ideally, you would want to go tweak on it if you make big changes. But you can usually safely change cams, exhaust systems, even intake manifolds, and not miss a beat. Can't do that with other types of systems.
I have "heard," but can't confirm, that Porsche uses a MAP sensor to determine the load tables. Ford inferred MAP from a MAF meter, therefore a change in displacement could wreak havoc on those. It could be tuned out, but it would be a headache.
So, what was my experience? Well, before I did the MAF, I made a lot of changes. 3" mandrel bent exhaust, gigantic intercooler (core was 24X16X4 - it was HUGE), short runner intake, and WAY too much cam for a street driven turbocharged car. I got rid of my BCS (boost control solenoid), and put in a manual controller, set to around 18 PSI. Spool time was horrible, but it was a solid, fast car. Stock injector size was 35#/hr, turbo was a .60 trim T3 (NOT a T4 if a vendor who sent me a PM "correcting" me on the airflow of a .60 trim turbo
). At 12.0:1 AFR, the injectors would support 28#/min of airflow. No problems with that, and I would turn 7,000 RPM, and never have any issues.
So when I did the MAF, before doing any other tuning changes, I took the car out for a spin. It immediately spooled about 1,000 RPM sooner (remember, I had WAY too much cam), about 2500 RPM instead of 3500. Then at a little under 5000 RPM, the car just fell on its ***. I had no idea what happened initially. Then I thought I'd try again, watching my AFR gauge (note they are crude and unreliable for tuning, but not so bad for diagnostics). Got on the gas, and had the same immediate rush - then started watching green bars fall off. The next day, I put in some 46#/hr injectors (good for about 37#/min airflow). And it ran like a bat out of Hell. Over the next few weeks, I put on a wideband, and starting calibrating the transfer function and fuel maps. Note that I got teh transfer function directly from the source (Ford, as I worked on the Modular engines and that's what the MAF came from), but the package has a definate impact, meaning fine tuning must really be done on a case by case basis. I eventually managed to get 33#/min of airflow out of the system. Again, this was a bone stock Garrett T3 turbo that isn't too dissimilar to a K26. There is a pretty good rule of thumb that 1#/min of airflow is good for 10 crank horsepower. Oh yeah, idle stability also went from crap to OEM smooth.
So, given that background, I have to say that a MAF conversion is a HUGE thing. I think Rogue's 5% number is a a big underestimation - recall I went from a max of 28#/min to 33#/min with a MAF and fuel table changes only. The only issue I have with a MAF conversion for 944's is that it isn't open source, but I'm the kind of person who likes to tinker. And as you get a bigger turbo and bigger injectors, you'll need to make changes (injector size), meaning you'd need to find a way to get back into the calibration. Obviously if you were to do anything that would change the aircharge temperature (i.e. more efficient turbo, better intercooler) or octane rating, you'd want to adjust your ignition tables, as well.
Anyway, there may be some quirks between the two systems that may make a 944 behave differently than a 2.3L turbo Ford. But for the most part, those are my thoughts. If you can't tell, I'm a BIG proponent of a proper MAF system, and I've offlined with both John and Rogue enough to know that each of those guys absolutely knows their stuff. WOuldn't not hesitate to buy from either one of them, but I'd not really consider any of the other systems. Are they expensive? Yes. Are they worth it? Abso-freakin'-lutely.
Note a big point - there is a HUGE difference between "tuning" or "calibration" and "strategy." Strategy is the base code, how things are written, and what the computer does with the inputs. Calibtration is dialing in numbers for those inputs. You absolutely can NOT "tune" your car to a MAF conversion without changing the strategy.
From what I have seen, there are two folks out there who can provide a MAF that was done the same way - Vitesse and Rogue. After having seen folks in the Ford community take off their Pro-M junk because the tune would change any time the weather did, and in some cases, when the engine bay got warm, I would never consider another type of MAF.
The old Ford setup was similar to the 944 stuff in that it used the same air meter. Ford calls it a vane air meter, or VAM, rather than an AFM, but the effect is the same. It more or less measures volume airflow, which the strategy then adds barometric pressure and ambient temperature to to calculate a mass air reading. A MAF system directly measures the MAF. As Sid pointed out, mass is mass is mass. It does not matter what the source of it is, and it does not matter where it is going. That is one of teh beautiful things about a MAF, you can change stuff on your car without having to remap the whole thing every time you do it. Now, having said that, there is a caveat, which is probably what John was alluding to. The efficiency of a turbo will have an impact on the aircharge temperature. That will affect your MBT (Minimum timing for Best Torque). So yes, ideally, you would want to go tweak on it if you make big changes. But you can usually safely change cams, exhaust systems, even intake manifolds, and not miss a beat. Can't do that with other types of systems.
I have "heard," but can't confirm, that Porsche uses a MAP sensor to determine the load tables. Ford inferred MAP from a MAF meter, therefore a change in displacement could wreak havoc on those. It could be tuned out, but it would be a headache.
So, what was my experience? Well, before I did the MAF, I made a lot of changes. 3" mandrel bent exhaust, gigantic intercooler (core was 24X16X4 - it was HUGE), short runner intake, and WAY too much cam for a street driven turbocharged car. I got rid of my BCS (boost control solenoid), and put in a manual controller, set to around 18 PSI. Spool time was horrible, but it was a solid, fast car. Stock injector size was 35#/hr, turbo was a .60 trim T3 (NOT a T4 if a vendor who sent me a PM "correcting" me on the airflow of a .60 trim turbo
). At 12.0:1 AFR, the injectors would support 28#/min of airflow. No problems with that, and I would turn 7,000 RPM, and never have any issues.So when I did the MAF, before doing any other tuning changes, I took the car out for a spin. It immediately spooled about 1,000 RPM sooner (remember, I had WAY too much cam), about 2500 RPM instead of 3500. Then at a little under 5000 RPM, the car just fell on its ***. I had no idea what happened initially. Then I thought I'd try again, watching my AFR gauge (note they are crude and unreliable for tuning, but not so bad for diagnostics). Got on the gas, and had the same immediate rush - then started watching green bars fall off. The next day, I put in some 46#/hr injectors (good for about 37#/min airflow). And it ran like a bat out of Hell. Over the next few weeks, I put on a wideband, and starting calibrating the transfer function and fuel maps. Note that I got teh transfer function directly from the source (Ford, as I worked on the Modular engines and that's what the MAF came from), but the package has a definate impact, meaning fine tuning must really be done on a case by case basis. I eventually managed to get 33#/min of airflow out of the system. Again, this was a bone stock Garrett T3 turbo that isn't too dissimilar to a K26. There is a pretty good rule of thumb that 1#/min of airflow is good for 10 crank horsepower. Oh yeah, idle stability also went from crap to OEM smooth.
So, given that background, I have to say that a MAF conversion is a HUGE thing. I think Rogue's 5% number is a a big underestimation - recall I went from a max of 28#/min to 33#/min with a MAF and fuel table changes only. The only issue I have with a MAF conversion for 944's is that it isn't open source, but I'm the kind of person who likes to tinker. And as you get a bigger turbo and bigger injectors, you'll need to make changes (injector size), meaning you'd need to find a way to get back into the calibration. Obviously if you were to do anything that would change the aircharge temperature (i.e. more efficient turbo, better intercooler) or octane rating, you'd want to adjust your ignition tables, as well.
Anyway, there may be some quirks between the two systems that may make a 944 behave differently than a 2.3L turbo Ford. But for the most part, those are my thoughts. If you can't tell, I'm a BIG proponent of a proper MAF system, and I've offlined with both John and Rogue enough to know that each of those guys absolutely knows their stuff. WOuldn't not hesitate to buy from either one of them, but I'd not really consider any of the other systems. Are they expensive? Yes. Are they worth it? Abso-freakin'-lutely.
02-25-2011, 12:15 PM
#36
Race Car
The old Ford setup was similar to the 944 stuff in that it used the same air meter. Ford calls it a vane air meter, or VAM, rather than an AFM, but the effect is the same. It more or less measures volume airflow, which the strategy then adds barometric pressure and ambient temperature to to calculate a mass air reading. A MAF system directly measures the MAF. As Sid pointed out, mass is mass is mass. It does not matter what the source of it is, and it does not matter where it is going. That is one of teh beautiful things about a MAF, you can change stuff on your car without having to remap the whole thing every time you do it. Now, having said that, there is a caveat, which is probably what John was alluding to. The efficiency of a turbo will have an impact on the aircharge temperature. That will affect your MBT (Minimum timing for Best Torque). So yes, ideally, you would want to go tweak on it if you make big changes. But you can usually safely change cams, exhaust systems, even intake manifolds, and not miss a beat. Can't do that with other types of systems.
I have "heard," but can't confirm, that Porsche uses a MAP sensor to determine the load tables. Ford inferred MAP from a MAF meter, therefore a change in displacement could wreak havoc on those. It could be tuned out, but it would be a headache.
Excellent points throughout.
It is my understanding that the 951 uses the TPS to determine load tables in a stock form anything over 66%throttle goes to a WOT map (low timing values) hence the sluggish transition.
I know on my car that it is mapped out fully from idle- to rail the 3 bar sensor. This means it should target appropriate cells regardless of rpm,pressure,mass,tp.
This is why I posed the question earlier of why it would make any difference regarding what turbo is utilized and when it hits 1 bar. If the mapping is done correctly it shouldn't matter if it hits 1 bar at 3k or 4.5k rpm.
02-25-2011, 01:02 PM
#38
Race Car
So Porsche, if I understand their methods correctly, uses a much better system to determine load.
02-25-2011, 01:20 PM
#39
Race Car
My understanding is that the map sensor in the klr has very limited usage. So limited that it sends a signal to the gauge and stock overboost protection.. I am fairly sure it does nothing regarding tuning for load.
I know Rogue uses the map sensor for full range timing and fueling. I am not sure if any other systems do this.
I know Rogue uses the map sensor for full range timing and fueling. I am not sure if any other systems do this.
02-25-2011, 01:40 PM
#40
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Right, most do use TPS position to distinguish between part load and full load tables - but at any given point, spark is still determined on what the computer thinks. But I was really addressing what load is in the context of displacement. Won't be an issue to most people, but if anyone is considering a displacement change, this comes into play. Load is how much air is going into the engine compared to how much could be going in. Or basically it is manifold pressure. As the Ford has no MAP, it has to infer manifold pressure, which it does by measuring airflow and RPM. So if I have a 2.5L stroker (which I had built, though I never ran it - had kids, career change.....life happened), but my code infers MAP from airflow and RPM, it will always think I'm more highly loaded than I am, and I'd be running less spark than I should.
So Porsche, if I understand their methods correctly, uses a much better system to determine load.
So Porsche, if I understand their methods correctly, uses a much better system to determine load.
02-25-2011, 01:41 PM
#41
Rennlist Member
So are there any users of MAF systems that just alter voltages (eg lindsey MAF's or SFR MAF's with mafterburner or similar piggybacks) that are happy or not happy with the systems? If not happy then what are the specific problems they have encountered.
02-25-2011, 02:27 PM
#42
Race Car
On edit. Airflow is actually a more true indicator, because your manifold pressure assumes the same volumetric efficiency across the board. Of course, you tune for that, but if you change anything like an intake manifold or cam timing, or anything else that may change the shape of your torque curve, the MAF will accomodate it better than the MAP. But like I said, a displacement change will screw all of that up, making the MAP better for load calculations (but inferred load from the MAF is better for a given displacement with other changes).
Last edited by 67King; 02-25-2011 at 11:52 PM. Reason: Brain fart
02-25-2011, 09:10 PM
#45
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John or Josh or ??
I am a little puzzled by this particular paragraph? Why would there be a problem utilizing different spooling turbos and the tune to go along with them? As I understand it the maf is reading airflow which is targeting a particular cell for the IDC and the map is reading pressure which is targeting cells in the timing map. Along with the tps you should be able to target the proper fueling and timing regardless of the turbo? This is an honest question..
I am a little puzzled by this particular paragraph? Why would there be a problem utilizing different spooling turbos and the tune to go along with them? As I understand it the maf is reading airflow which is targeting a particular cell for the IDC and the map is reading pressure which is targeting cells in the timing map. Along with the tps you should be able to target the proper fueling and timing regardless of the turbo? This is an honest question..
Obviously, this is a limiting strategy. The solution is to do true 3-D tables for all throttle positions. By using pressure for the 3rd dimension, we can dynamically adjust fuel and timing for any RPM & Boost pressure - no more large transition between part-throttle and WOT!