Well i just updated to v. 1.7. Ime assuming i will run open loop with my larger injectors. TXS told me to use 600-625 as the corrected size for my 780's. They said if i used 780, it might run lean. Well if there is a back up map running allready, like i read in the manual, Hell, i dont even know how to word this.......So my Map 1 will correct the back ground map which is allready correcting the ECU map right?? So will the corrections be about the same amount as the previous version or will they be less because of the built in map compensation?? (hell, ime confusing myself now) Lets try this, if i run a pre-injector install, map-0 data log, then do injectors and scaling, would that be a good starting point to tune, or will it be way off due to the built in map?? Thanks (ime going to bed)

 

Ok.. since open loop fueling features drive the injectors directly, the background map is the "starting point" for all of your maps.. if you set the the Map switch to 1.. and all of the fuel settings are set to 0.. it means your not altering the UTEC's background map at all from what turboXS provides to you..

In the timing map, if its set to ECU, then its allowing the ECU to control timing unless you put something in that cell (that hasn't changed from the earlier UTEC firmware)

Ok.. and to explain why injector scaling numbers aren't the same as your 780 injectors.. It has to do with how "Lazy" big injectors are at very low duty cycles.. In other words, if you scale the injectors to the actual size that they are, you reduce the injector duty significantly and it will either run very lean because the injector response is so slow, that the duty represents only the injectors "Actuation time" but not the injectors actual fuel delivery time.. so by using 600-625 as your scaling, your giving the injectors "Time" to actuate and deliver fuel.. This is the reason why big injectors can sometimes be troublesome to get to idle..

Yes, the background map is generally already lean on alot of cars, especially cars with aftermarket MAF pipes and intakes.. so you have to tune no matter what, and start very rich..

Now.. a practical example of the 625cc instead of the 750cc injector scalingsize..

if you scale at 750, and the injector is 750.. and you pick 10% duty cycle, figure 3% of that time is spent opening and closing, so your actually getting 7% and not 10% fueling.. By using scaling to 625 (approx) you increase the duty cycle slightly to lets say 15% or 13% instead of 10% that you want, but because of the slow response of the injector, that 3% is still opening and closing time, so you net 10% duty..

At higher RPM and higher duty cycles, its not quite as critical, but it does need to be kept in mind while tuning.. at very low duty cycles at idle, it makes getting the car to run a little more tricky, so the easiest solution is to just use less scaling and compensate with the maps accordingly.

The mistake that TurboXS made with their scaling parameters is how they are labeled and the numbering system they chose.. The two scaling parameters (stock injector scaling and modified injector scaling) aren't actually related to eachother, stock injector scaling represents the scaling of the MAF frequency, and the Modified Injector scaling only applies to the scaling of the background maps for larger injectors.. and then you have the number system they use.. you have to forget that 550 is the 550injectors, but 550 is just your "Zero point" where no scaling is occuring.. the larger the number, the leaner the car will run, the smaller the number (from 550) the richer it will run with the stock injectors.. replace those stock injectors with bigger ones, and you increase fueling overall and make it richer.. so you have to increase the scaling number to lean it out.. Understand?

I hope that doesn't confuse you more.. but basically the right answer is to install your injectors, run the car without altering the scaling and see how rich your car is actually running.. then increase the scaling to 600 or so and check again (with the fuel map 0 as all zeros for this) once your fairly close (but still a little too rich) then build your fuel map and tune from there to where you want.. 600-625 is where you'll likely end up.

Gestalt actually experienced this firsthand, he basically installed his injectors, and didn't have to alter his scaling initially, and ended up with a pretty acceptable base map as a starting point.

With new injectors, and a new pump, at higher RPM the fueling may be generally alot richer compared to new injectors and the stock pump.. Keep that in mind, but its loss of fuel volume, and you should upgrade your pump before the injectors.. But you probably already have done this, or knew this fact anyway.

 

I never ended up scaling the injectors at all. I left the setting stock installed my 680 injectors and globally fixed my lean condition.

 

o.k. thanks Jack. I got a car lift for Xmas and we are having a tech day at my house tommarrow. I will be installing the injectors then. After installation, i will do a log. then keep bumping up the modified injector size till ime a little rich then fine tune with map1. Now there is no need to mess with the stock injector size right?? O.k. ime running straight 100 octane. I figure i have a lot of timing and boost to add. In what ratio should i add them?? Run up the boost till knock?? half boost half timing??? or keep boost at 22 and keep adding timing???? RRR

 

Try lower boost, tune to get used to how this reacts... unless your car idles rich then you can adjust the stock injector setting a little..

Run conservative timing, find your happy AFR, then add timing for a low boost map.. then raise the boost and pull 2 degrees across the board, then sneak back up on your tune again.. That should give you a good rich safe setup.. Don't add timing until you get knock though, watch your EGT's if you can, and watch for the temps to start climbing a bit.. listen to the engine using the headphone on the Tuner (if you have that) and listen for noises that are spikes above the background engine noise.. thats knock, back off your timing by 1/10th degree if you hear it.. if you have a spot where you get knock, and can't get rid of it with timing, add a bit of fuel in that region until the knock goes away, and then start adding timing back until it comes back.. then back off 1/10th until it goes away..

Remember use small steps.. 1/10th of a degree at a time when you finally get close..

Typical timings for peak cylinder pressure is 5-9 degrees ( more peak boost, less timing.. more timing, more torque.. so its a compromise, I generally run 19psi of boost at peak torque so I can run more timing and build more torque) at higher RPM, 17-23 degrees is typical.. 19psi boost you'll typically be able to approach 23 degrees if your AFR's are around 11.5 or richer..

 

My brain just expanded slightly from reading MJ's posts. I havent grasped it all with confidence just yet, but I am getting there.....