Okay....before you all get on my ***......I can't tell you who, or which manufacturer. Still, I will share what I learned.

It is no secret that the key to modern engine performance lies in the ECU programming. Why is then, that trying to tweak an ECU is so difficult?

Actually....it isn't. The programming that goes into an ECU is not very complex. However, the limitations of the ECU output is governed in large part by the sensor input. It is the sensors monitoring engine function that hold the key to unlocking engine performance in addition to the ECU reprogramming.

What good is that intake system, for example, if it maxes out your MAF signal, and the ECU won't, in turn, deliver any more fuel to match your actual higher air flow. These are the kinds of issues that come up. I used the MAF as an example, but this is kind of logic applies to all the sensors that feed into the ECU. FI systems get around this by using piggyback computers to fool the ECU, but to extract maximum performance from the ECU alone, one needs to alter the sensor input also.

Just wanted to share the info. Sorry if it is old news to some.

 

and theeeennnnn.......

 

This is definately one of the issues for major modifications like high boost. Fortunately a lot of creative people have figured out great combinations of fuel pumps, injectors, TS ECU maps and on and on to over come some of the stock system component limitations to get to 8, 9 and even 10psi of boost. To go much further it sounds like the newer stand alone systems with add on sensors will really take things to the next step and beyond. It is getting exciting to see some people hitting very high numbers recently. Now if only some of this stuff would drop in price by 50% so more of us could join in the fun. I will say this though about the ECU programming for our cars, the code that one has to read to understand everything is not easy to deal with like many automobile ECU systems which is why there are very limited locations that can do this kind of work. They are not all the same.

 

I'm surprised nobody has looked into a different MAF unit, where the maximum output voltage corresponds to a higher airflow than stock. For instance, the MAF output is calibrated such that the actual maximum output voltage to the ECU is the same as stock, but represents a higher actual airflow. The fuel injectors are then upsized by the same percentage to match the increased airflow sensing capabilities of the new MAF. One could now use the programming in the stock ECU to control a higher air and fuel flow while maintaining the same overall air:fuel ratio.

 

That would be ideal - I wonder if anyone has tried larger injectors on an N/A car here yet... that would be interesting...

 

that would be pointless =P

The stock injectors are more than adequate for all your N/A needs, you just need some sort of fuel computer or FPR to tune to your preference.

 

the stock injectors are good to what like 315-320 (at a guess) whp, also keep in mind that an na car can safely run in the 13 a/f range while most fi cars reside in the 11.5-12 range which requires much more fuel at the same numbers.

 

This is being done by someone already, but he had to use E-manage to control them properly. He is using N2O which is why he went with the larger injectors otherwise they are not needed for N/A.

For those going high boost, why even mess with the MAF when you will be able to soon go stand alone with better overall control and better sensors. Our ECU is not that easy to reprogram and would be very expensive to mess with (Unless you live close to TS). Sure it would be nice to maintain all of the stock features the ECU controls, but until a more practical/economical solution is available to program the stock ECU, this will continue to be a big road block as many do not live close enough to Technosquare to drive in and have them do it.

 

I am simply suggesting a way to increase fuel flow using the stock ECU programming. I never meant to imply that the capacity of the stock injectors were not adequate for NA upgrades. They most certainly are, but you then need to alter the signal going to them to change fuel flow. By using a slightly larger injector, say 10-15% larger, you can use the stock programming to deliver slightly more fuel. If, at the same time, your mass air intake is increased by a comparable amount, the A/F should stay the same and not trigger any error codes by way of the oxygen sensors.

 

but at the same time by going to a slightly larger injector without compensating with a reflash or piggy back to scale the injectors will cause serious issues with idle performance. the car will still think it has stock and not provide the right amounts of fuel.

 

Idle would definitely be affected, although I personally do not know how much of a problem that amount of enrichment would be at idle. I was really only thinking about the larger injector idea in conjunction with a rescaled MAF ouput, but a minimal airflow state, such as at idle, would still be a problem, even with a rescaled MAF sensor. Back when I owned an Audi S4, people would physically block the MAF sensor so that the airflow signal it got was less than the actual airflow. We would then run with bigger injectors and the idle issue really wasn't a problem, although I can't comment on emissions at idle with the super-rich mixture. Oh well.....back to the drawing board. I must admit, I don't yet know which direction I want to take my tuning of this car. Option #1- Maximal NA mods, including cams, then a progressive Nitrous System. Option #2- Wait and see what the HKS supercharging system is like. Option #3-APS twin turbo. As I have said many times previously, I will go with the option that allows me to have the most accurate and thorough engine management. None of the current offerings are optimal designs in my opinion, and although not the most powerful, the Crawford/TS combo seems to be one of the best thought out so far. It's not just about maximum power for me...it's also about the overall feel and reliability of the car. I live in the Northeast, and my car is a roadster, so I won't be driving it from December through March. That's when the transformation will take place!!!!!!

 

i personally experienced that exact problem on a friends 240sx he upped the size of his injectors in his sr motor and only had an afc to tune it. the thing would take three tries to start then it would just stall unless your flooring it. eventually they flooded the engine with fuel.

 

Staying N/A with the Crawford package, an intake, cams, an exhaust, the TS reflash, lighter flywheel or TQ converter and a different final drive will really make this a fun to drive car power and speed wise, while still maintaining a major reliability edge over FI. Really the only advantage FI would have over this setup is straight line performance. Add in some suspensions mods and your set. That is the route I am taking and so far am very happy. I would like to do cams sometime but haven't taken that road just yet.

 

hey zzzya did you get the ts ecu flashed for your mods or just have them up your rev limiter, top speed gov, and tb opening? I have a 5AT with nearly the same mods as you and was wondering what I should do for for a/f tuning. either an s-afcII or ts ecu. Can't I get them to work in conjunction with each other?

 

Good thread Speedracer...thanks for starting it.

Well, fortunately, with N/A mods, our MAF sensor isnt even close to being maxed out, so mods should be relatively effective at increasing N/A HP.

With F/I, most of our MAF sensors are maxing out at 4500-5000rpm depending on boost level. Once the MAF hits 5.0V, its done, but as mentioned, we've gotten very creative here. With the Greddy kit and the eManage (other solutions do similar things as well), the MAF voltage is clamped at 5.0V so the ECU never sees more than that...and doesnt freak out and go into limp mode. Then we add more fuel via eManage beyond that point. Obvisouly since we are only referencing RPM to base the fuel on, it takes some fine tuning to get this right...and its difficult to get it perfect. So most people err on the side of slightly rich....between 11-11.5:1 so compensation for any atmospheric or weather changes...bad tank of gas...etc...etc...

Bigger flowing MAF sensor is a good solution, but a better solution is a speed density system (MAP based). The Profec includes an excellent MAP sensor, and once you creat the new fuel table, you can enrich fuel by referenceing RPMvs.manifold pressure....which is a very accurate tuning method.

Oh, and for those that say our MAF sensor housing is restrictive...take a look at it someday. It's not a typical honeycomb style MAF sensor. It just has a slice of plastic going through the middle of it....virtually no restriction at all.

 

thats cause its a hotwire setup.......not a huge restriction, but on many cars, very prone to breakage (nissans thankfully are not known for them going bad too often )

 

Yeah...and I examined it closely. Unlikely a honeycomb style, I cant imagine this thing being damaged by reverse flowing F/I charges. If you look it, there is nothing but plastic on the "wrong" side of it....
Damn..ia pic would be worth a thousand words here, but it is too much hassle to take up the hoses couplers to snap a pic.

Oh wait..my car isnt even here...its probably in Phoenix AZ by now...on its way to Charlotte.

 

So does the Profec use MAP only when the MAF sensor is maxed at 5v, then go back to using the MAF signal to determine fuel flow below 5v? Also, do you know at what specific air flow rate the stock MAF sensors generates maximum voltage (5v) and what is the "headroom" you have with the stock engine. (basically, what is maximum stock airflow). I have read somewhere on our forum that, in fact, some of the aftermarket intakes cause the MAF sensor to max out. Without additional engine management, the stock ECU doesn't know to add any more fuel once the MAF is maxed out. Not certain exactly where I read it....maybe I am mistaken???

 

The stock MAF sensor maxes out at 5.0V which is 33lb/ft of air. I dont have my car in front of me...so I cant exactly confirm the units of measure...but it is 33 something/something...I think it got it right...but someone can correct me if I am wrong.


I am not certain how much cushion you have on a N/A motor...but believe me that a CAI or headers and exhaust arent going to max out your MAF sensor. The manifold on an N/A is never seeing positive pressure, and that is really where you see the massive increase in airflow. At 9psi, I am maxing out the MAF at 4500rpm, and producing roughly 350whp, so its safe to say there is no chance of maxing out your MAF with N/A mods.

Regarding the MAP sensor based tuning on the Greddy eManage. When the car is not under boost, then the ECU does it's thing without any issues. But as soon as boost is acheived, and fuel enrichment is called for, then the MAP/RPM fuel enrichment map kicks in. In this application, until positive manifold pressure is achieved, the ECU is still controlling everything. Once positive manifold pressure is acheived, then the eManage adds fuel. Again, this requires creating a brand new table from scratch, which nobody has had the time or inclination to do just yet.

Unlike a stand-alone ECU, you still need to leave the MAF sensor and housing in place, but the fuel enrichment portion of the tuning is handling totally by the eManage. Now keep in mind, although this is better tuning that MAF/RPM, it is not as perfect as a stand-alone. Once again, the eManage is still relying on the basic ECU inputs, and then adding to them. But with MAP tuning, at least you have two reference points to plan the enrichement...MAP and RPM....not just RPM, as is the case with normal MAF/RPM tuning beyond 4500rpm.

Hope I didnt confuse you.

Hth,

Sharif