somewhat sluggish at times

[LB72004]

doing some logging to see if i can find out why at times it seems that when i am pushing my truck hard it seems to accelerate to a point then hangs and won't accelerate any more. almost like it is loosing fuel pressure but the log shows good pressure.

it seems like it is as if it is related to boost or grams/sec air but maybe it is vain position???

here is a screen shot
17446

anyone able to see anything obvious?

[LB72004]

Opps, put this in the wrong area. Any administrators able to move this over to the LMM section for me.

Thanks Jason

[Mitco39]

Where are you having the issues? Just a quick look at the image shows a fairly linear acceleration...

[LB72004]

if you look at the MPH from about 2770 all the way to 2800 it only increases about 5 MPH. from 2800 to the end it is about a 25 MPH difference. also right at the line you can see the mm3 shoot up. prior to the line you can see that the throttle is held at roughly 90% and the mm3 is slowly dropping. something changes, this is what i am trying to find out, and the fuel increases and the truck starts to accelerate much quicker. about 20 MPH quicker in the same amount of time as before the line on the graph.

the only thing that i see is that i pull out a little on the throttle just before the fuel jump up, which i would only think it should make it less not more, and of course the bottom of the graph with the grams/sec, vane position & boost.

i believe my problem lies in what is happening at the bottom of the graph. some sort of limiter or bad vane to boost correlation. you can see that shortly before the line boost starts to rise and gains about 10 PSI. the vanes are slowly opening up then suddenly the grams/sec air starts to climb and bam, the ECM sees the right amount of air and adds more fuel.

the problem with this is that it is a little smoky before the line on the graph then right at the line when the fuel jumps up the smoke clears up. so there does seem to be a air to fuel ratio problem here but why is the turbo holding back? i am starting to think that i should try and open the vanes up a little in that area of the map and see if it helps. i am wondering if the closed vanes trying to create boost is just choking off the exhaust and hurting air flow

[Mitco39]

So your smokey before the turbo spools? I need to see a actual injection time (in Us) to be able to see what sort of fuel your throwing at it.

Just looking at it quickly it looks like your MAF may be dirty, thats whats causing you the issues. Or thats where I would start looking anyways. You could have a leak between your MAF and turbo I guess. If its all been modified I would just look around there and see if anything looks out of place. As long as you havent scaled your MAF with some funny adjusters I would believe looking at this log that its a mechanical issue.

[LB72004]

ok, i will see if i can get my MAF cleaned and run another log for my way home today.

i thought i had selected the Us pid when i logged it, but maybe not. i will add it to this run

the intake is all stock. stock filter, stock intake and i haven't changed the MAF scaling.

one thing i noticed last night when going over the information and looking at the tune is that the tune calls for something like 35% vane position in the area of the log between 2770 to 2800 yet the log shows something like 95+%. and looking over the multipliers, etc I could find nothing that would explain the high vane % in the log. maybe it is jacked up PID control. time to verify that. may also try and zero out some of the multipliers too

[Mitco39]

The turbo is going to do everything in its power to make the request boost that you have set in the boost tables (as long as B2231 and B2232 allow). So if your telling the turbo to build more boost than possible (or if you have a leak bleeding off boost) the turbo is going to ride the Turbo Vane Target Position Maximum to do its best to reach your intended boost.

Look over your Desired boost level tables and make sure you are not asking to much of the turbo you have.

[LB72004]

just realized, in order to get an effective turbo brake one would have to modify the B2231 & B2232 tables right?

back on track, so the boost tables override the vane tables. vane tables are supposed to be a starting point and then the ECM adjusts them based on if the turbo is making the required boost or not. and is is the PID tables that dictate how quickly the ECM makes the adjustments. is this correct?

so if the ECM is running the low altitude boost table then the boost is pretty close to commanded. if it is running the transient table then i can is 8 or so PSI short and the ecm would want to crank it up some.

i didn't want to but maybe i need to make my transient and altitude tables the same. then i will have a better understanding on what tables to look at when combing through the logs.

it seems that most of the time it is running in the transient tables, even during acceleration. is this what others do?

[LB72004]

ok, cleaned the MAF sensor.

here is another log:
17455
same thing happened here. oddly enough it happened at the exact same time as the last log. right when i start to lift off the throttle. hmm new lead???

here is another screenshot from later in the log where it did what it should. ran strong right from the get go and did not get stuck with declining mm3s and short on boost
17456

and attached is the full log

[LB72004]

i added my input on these attachments
17458

17459

what do you think?

[Mitco39]

Is your EGR blocked? Your maf is still reading low in that first screen which is limiting your fuel (and thus your power) if your EGR is intact but turned off chances are the valve is sticking open slightly and its sucking in exhaust gasses instead of fresh air.

[LB72004]

it is turned off but i doubt it is blocked. i looked and didn't see anything that looked like a blocker plate.

i take it this will be my next step. get a blocker plate in there and run another log?

[Mitco39]

I would put money on it that that will solve your issue. Its typical to see it stick open sometimes and closed others.

[LB72004]

ok, ill put $10 down. you?

[Mitco39]

You would put money against the fact that its your EGR? lol

[LB72004]

i was thinking there was a small chance i could win something here :pokey:

if not then you win $10 for helping me out

[Mitco39]

It was more a figure of speech. I am not interested. Use the money you might have to send to me to pay for your plate and call it a day.

[LB72004]

i know, i was just joking with you to see how interested you actually were.

thanks for your help so far. i will work on get it blocked off and post a new log

[LB72004]

so i think you have convinced me that it is a leaking EGR. i was able to take it out on a run earlier today and hold the throttle steady with a long enough road and not let off. it did the same thing acting sluggish and smoking for about 5 seconds and then all of a sudden the exhaust cleaned up and started accelerating quickly.

with your explanation above and this, i am thinking that the vanes being closed trying to make boost is creating high drive pressure. this forces the EGR open and exhaust replaces air and causes the smoking. after a bit the boost raises to a point that the vanes open up enough that the drive pressure no longer holds the EGR open. with only air and no exhaust going into the intake the fuel burns better and the engine makes more HP. also when the EGR closes and the exhaust stops replacing the air then the grams/sec go up and this is when the ECM can now add more fuel

does this sound right?

i have order a blocker plate and will put it on when it gets here and will run the test again and see if it is all good

[Mitco39]

Yes that sounds correct. Have you increased your maximum vane position tables over stock by much? IIRC it shouldnt allow them to sit that closed because of that very reason, you want to keep your drive pressure under control.

[LB72004]

if i remember right, it is only about 5% more then stock

[LB72004]

Ok, so i got the blocker plate in. still does it. it seems like it doesn't do it for as long though so it helped but it still has the problem.

now i am thinking it is just not spooling as fast as it should. any tricks i should try to improve spooling? obviously increasing vane position won't help as the ECM is already doing that. maybe lower timing some?

[Mitco39]

Boost leak? Do another log so I can take a look if you want.

[LB72004]

ok, i'll do that. any location typical for the LMM that leaks tend to form?

what's weird is that it only does it about 30~50% of the time. when it doesn't do it it takes off real strong smoke free. when it does do it i can usually lift off of the accelerator and reapply it, the 2nd time it will start to accelerate much quicker with much less smoke and much more boost. this is why i keep coming back to vane position, but i am currently running stock vane table and it still does it so???????

[LB72004]

Sorry keeping you waiting. Did a boost leak test and didn't come up with anything. Was pushing it to about 20 psi and could not find any leaks.

Anything else?

[LB72004]

i think i got it figured out.

i lowered the max vane position at the higher rpm and mm3 range and bam, problem seems to be gone. revs much quicker now without any smoke. i think having the vane closed too much can actually hurt spool. looks like having it closed too much will restrict flow so much that the exhaust velocity falls to the point of not being able to turn the turbine faster. open them up a little until you hit max exhaust speed and that will build boost the fastest.

i ran around chasing all sorts of things but it was a good learning process

thanks guys