Ok, a while back I got my flux injectors. As soon as I did, I lost the ability to tow without causing turbo surge. It's fine until 4th gear and then it's almost impossible to drive without the turbo going crazy. So what I had decided was that I need twins - which I probably will still do. But here's where I'm confused.
Before the injectors I could run on any settings I chose without any problems. So for example, I could run with 180hp of programming and 50hp of pressure. Or I could run with 100hp of downloader, 100hp of programming, and 50hp of pressure. Basically as much fuel as I had, and it would still tow fine. Now with the injectors, I can turn everything off so that all I have is 100hp of fueling from the injectors and it tows terrible. What is different about 100hp form injectors VS 100hp or 200hp from electronics?

 

what does your rail pressure gauge read, possibly you are now injecting more fuel through the larger injector? just a thought

 

Have you tried it with the Edge off and the TS on, say set to around 50hp or so?
I would think with the 100hp injectors a bump in rail pressure is required.

MikeyB

 

I did try that.

 

I actually prefer 100 HP from injectors and then use the electronics on top of this to fine tune. When towing, I'll add TST 1x0 and a hair bit of pressure to get about 425 rwHP.

To me, electronics by itself is just too "peaky" and quirky.

The injectors just mirror the smooth factory ECM programming, but of course at a higher level.

The only time I've had towing issues was when running a SPS66 turbo. That was lag, EGT, smoke, and major surge city unless I kept the engine wound up. I wouldn't blame the injectors on this issue - just the turbo since it was just overkill for towing.

I then "downgraded" to a SPS62 and then finally to towing twins. With each "downgrade" step, all around driveability monumentally improved.

 

i try not to think, hurts too much!! LOL!!

 

Did I miss your point regarding my set up? Not sure where you were going!

 

Ditto but my professors keep trying to get me to do it.

 

As far as electronics (non-downloader type) versus injectors go, my take on it is that most electronic boxes fuel off of boost. As such the tendency is for low rpm performance to be mediocre whereas mid to top-end performance tends to be awesome since boost is actually being read. You can improve the bottom end performance with a pressure box that does good low end MAP or boost manipulation like an MP8 or VA C3.1. However, electronics (non downloaders) to me just seem to be a bit delayed in their response since it adds one more step in between the sensors and ECM.

In comparison, injectors just fuel according to the ECM programming - whatever the boost level - with perhaps no sensor data manipulation in between if your boxes are turned off. In comparison to stock injectors, you may be getting slightly more fuel injected early on with the upgraded injectors. This effect is probably progressively magnified the progressively larger the injector. Now you have to burn this fuel and it is probably being burned more efficiently (to a point) since it's like having your injection timing advanced with less duration (compared to stock injector that has to increase duration to get same amount of fuel in). So by burning this fuel more efficiently it is causing your upgraded turbo to generate more boost. Perhaps this extra boost cannot be consumed by the engine at whatever rpm this happens at so hence it puts your turbo into surge.

Anyhow, when you talked about turbo surge I related to that when I towed with too big of a turbo. I ran the calculations using data from a 66mm compressor graph and proved to myself that it was too big of a turbo for the elevation I tow at because it just generated too much air than the engine could handle at typical towing rpm. So in your case maybe when you hit 4th, the rpm drops and then the engine therefore cannot accept any more air so it backs up in the intake tube and throws your turbo into surge?

I'm not saying you have too big of a turbo. If I recall, the A3k is ~58 mm? If so, it shouldn't surge (in theory)! Maybe you have some other stuff going on. When your turbo "goes crazy" what is your boost reading doing? Is it sustained or only momentary in 4th? What rpm?

Hopefully the above now helps get my "point" across????

 

I guess it makes some sense now. If the injectors are producing more fuel at 10% throttle at 2000rpms than 200hp of programming at 10% throttle at 2000rpms, then it would be easier for that little turbo to overspeed. So a turbo with a larger compressor wheel would theoretically fix the problem because it wouldn't be as likely to overspeed even though it can potentially move more air - am I thinking right here? I guess there has to be a fine line between too small and too big, because if it was bigger and was able to spin fast enough at 2000rpms in 4th, the problem would just be worse. I guess I could try putting the stocker back on and see how it acts.

 

I think in theory you are right. But what I really think will happen is even though the larger compressor will spin slower, it would still generate more air than your engine could handle and would actually be worse than what's happening now.

Just looked up the A3k specs http://www.atsdiesel.com/atswebsite/...e/TurboA3K.asp

and on the compressor side it is the same size as my stock 03 turbo and smaller than the 04.5+ turbo. It shouldn't be surging at all under normal circumstances. Those 57 mm compressor wheels usually have a very wide compressor map with strong surge resistance unless running very high boost at very low engine rpm (low air demand) due to say high fueling from big injectors.

When it surges, what boost are you at? This would tell the story of if it "overspeeds".

Is it only at ~2000 rpm?

The other major difference between your truck and mine is auto versus manual as well as your 315 tires versus my 285. I don't know how built auto tranny's work in terms of how they can affect rpm when locked versus unlocked. But at a given interstate cruising speed you would be running slightly lower rpm than I. So you are very true in this statement:

 

Cruising along at very minimal boost (0-5psi) if I start an incline - even a small one - as the boost gets around 10-12psi it starts surging like crazy. It won't even go above about 15-18 unless I give it pretty good throttle at which point it down shifts to 3rd and then of course the rpms come up and the problem goes away. Before the injectors with the same situation it would simply build enough boost, as much as 30+, to pull the hill and never want to lug or downshift.

 

Anybody else with input?