Stuttering/Hesitation completely removed! - car never smoother

[biz77]

Are you sure it is not a hiccup in the transition from CL to OL? Your delays are zeroed?

[LGTspecB1657615261]

Here are some logs... you tell me. I see CL/OL going from 8-10 in the logs.

romraiderlog_20090924_172545.csv

romraiderlog_20090924_172243.csv

romraiderlog_20090924_172109.csv

[LGTspecB1657615261]

Here are the tables, not sure if this is what you were looking for.

[Guest]

Have you tried revving the car up the problem rpm range while standing still? For me that's the easiest way to reproduce the problem. I.e. the lighter the load the more noticeable it is. It's also present while driving under light throttle for me, but revving is just enough to reproduce it.

[LGTspecB1657615261]

Have you tried revving the car up the problem rpm range while standing still? For me that's the easiest way to reproduce the problem. I.e. the lighter the load the more noticeable it is. It's also present while driving under light throttle for me, but revving is just enough to reproduce it.

 

I guess I have not tried that. I will do it. Could it be tip-in enrichment? My table is 0.66*stock tip-in across the board. My injectors are 825cc.

[Guest]

I have stock tip-in and stock injectors (and stock intake)... It's no way tune related.

[LGTspecB1657615261]

I have stock tip-in and stock injectors (and stock intake)... It's no way tune related.

 

Are you saying its now way your problem is tune related, or mine? That sucks you are running stock stuff and still getting the stutter. I hope you can figure it all out.

[Guest]

Neither. If the symptoms you have are like mine, I bet 99% it's not tune related.

 

My car is not exactly stock, I have bigger (twinscroll) turbo and sti intake manifold/tmic, tgv deletes and inlet. Temporarily stock tune, stock intake and injectors to minimize variables while tracking down the issues.

 

I described it in the detail in the other thread you posted to.

[LGTspecB1657615261]

Neither. If the symptoms you have are like mine, I bet 99% it's not tune related.

 

My car is not exactly stock, I have bigger (twinscroll) turbo and sti intake manifold/tmic, tgv deletes and inlet. Temporarily stock tune, stock intake and injectors to minimize variables while tracking down the issues.

 

I described it in the detail in the other thread you posted to.

 

I hear what you are saying, but it does seem to change with the tune. I am not sure what switching from 93 octane to E85 would cause. The gas seems good. It measures 84%. All that's left is the tune IMO. Nothing else changed.

[SubyShop.com]

MAF correction, timing map, and throttle map are the main factors for the stutter. Your open loop should be ok unless you were tuned lean on poorly calibrated MAF scaling

-Franz

[Guest]

I hear what you are saying, but it does seem to change with the tune. I am not sure what switching from 93 octane to E85 would cause. The gas seems good. It measures 84%. All that's left is the tune IMO. Nothing else changed.

 

Ok, your case may be different. Anyway try replicating the issue while just revving the engine. Just hold the throttle steady at 2500-3000 rpm wherever the problem range is and log. If you get it and your intake/injectors are scaled correctly then it is not the tune.

[NSFW]

Have any of you guys tried logging different parameters to see if any of them correlate with the stutter problem?

[NSFW]

MAF correction, timing map, and throttle map are the main factors for the stutter. Your open loop should be ok unless you were tuned lean on poorly calibrated MAF scaling

-Franz

 

What kinds of things in the timing map will cause stutter?

 

(My car doesn't stutter, I'm just really curious what the deal is.)

[LGTspecB1657615261]

stutter almost gone.

 

I will update later as I look into the ROM's more (I just got a new one). My guess is "rich stumble" I was running rich right around the CL/OL transition. my learning D was -2.4 and I think I was even richer in OL.

[Guest]

Ok, so you didn't have the hesitation while just revving the engine?

[LGTspecB1657615261]

Ok, so you didn't have the hesitation while just revving the engine?

 

crap, I still need to check that. I forgot, when I got the new map I was too excited and loaded it right away. I will do that, but from what it sounds like, we had the same sort of symptoms, but different reasons. Perhaps.

 

It looks like my Injector flow scaling was slightly off, so it was increased ~1% in the newer map. That to me, was the biggest change.

 

OL fueling was changed but out on the high end, so that probably did not have an effect on the stutter.

 

WGDC was changed for WOT - so that would not have an effect on the stutter.

 

Nothing else seems different between the maps. Just a little leaner across the board with the injector scaling. I am surprised it had the effect it did.

[LGTspecB1657615261]

I should emphasize that I STILL have stutter, its just much better. So, whatever is causing the stutter, its exaggerated when running rich. That is all I know at this point. Its definitely in closed loop only.

[LittleBlueGT]

Have you tried revving the car up the problem rpm range while standing still? For me that's the easiest way to reproduce the problem. I.e. the lighter the load the more noticeable it is. It's also present while driving under light throttle for me, but revving is just enough to reproduce it.

 

 

You mean you only get this at really light load? My car did that brand new, and has always done that (if I hold it at 2500 rpm in the driveway). When actually driving the car it is not a problem at all.

[LGTspecB1657615261]

Man, mine is still stumbling all over the place in CL. when the engine is cold its really bad. I thought things had gotten better, but I guess not.

 

I will have to figure this one out. OL it runs great! I wish I was in OL all the time. CL is stuttering, slight bucking, hesitation, whatever you want to call it. It "feels" either lean or rich, like the engine is not responding like it should to the given load... like I would expect at least. But the narrowband is rock solid when I log in CL. My MAF scaling is good as well. From what I can tell, no induction leaks, and my boost is acting normal in OL.

 

Steady low throttle, low load, slowly passing from 2k to 3k RPM. That is when it happens. All gears. Most noticeable in slow 3rd gear acceleration. Racking my brain here. I don't feel it when just revving the engine.

 

EDIT:

Could my 825cc Witchunter modded light blue injectors have a bad spray pattern? It runs smooth in OL, but the load is higher and the injectors are at a higher duty cycle... At low loads, low duty cycle, maybe the fuel is not smoothly being administered into the stream? Would lower fuel pressure cause issues at low loads, but not at higher loads?

Just thinking aloud. Maybe its a fuel delivery issue?

[Guest]

You mean you only get this at really light load? My car did that brand new, and has always done that (if I hold it at 2500 rpm in the driveway). When actually driving the car it is not a problem at all.

 

Yes, the higher the load the less noticeable it is, but even if I can't feel it, I still see the AFRs being too unstable. The car before never did it, my other LGT (stock) doesn't do it, and atc5's car who is running virtual the same twinscroll setup (my former) doesn't do it. It's something mechanical.

 

Man, mine is still stumbling all over the place in CL. when the engine is cold its really bad. I thought things had gotten better, but I guess not.

 

I will have to figure this one out. OL it runs great! I wish I was in OL all the time. CL is stuttering, slight bucking, hesitation, whatever you want to call it. It "feels" either lean or rich, like the engine is not responding like it should to the given load... like I would expect at least. But the narrowband is rock solid when I log in CL. My MAF scaling is good as well. From what I can tell, no induction leaks, and my boost is acting normal in OL.

 

Steady low throttle, low load, slowly passing from 2k to 3k RPM. That is when it happens. All gears. Most noticeable in slow 3rd gear acceleration. Racking my brain here. I don't feel it when just revving the engine.

 

EDIT:

Could my 825cc Witchunter modded light blue injectors have a bad spray pattern? It runs smooth in OL, but the load is higher and the injectors are at a higher duty cycle... At low loads, low duty cycle, maybe the fuel is not smoothly being administered into the stream? Would lower fuel pressure cause issues at low loads, but not at higher loads?

Just thinking aloud. Maybe its a fuel delivery issue?

 

Tried revving? Anything is possible. It's really one of the following possibilities (and tons of places to check):

 

- fuel delivery

- electric issue (not tune)

- post-MAF leak

- exhaust leak fooling O2 sensor

[LGTspecB1657615261]

Revving does not show anything.

 

The car is new and I know I did not have this issue before modding / tuning. So... its either something I installed, or its something in the new tune. I will work my way through all the things and try to figure it out.

 

I did not have this issue before the injectors, so my initial thought is that its fuel related.

[SubyShop.com]

My car started misfiring at idle and stumbling at low load several weeks ago. I cleaned the MAF sensor and swapped with a friend. Swapped plugs and coil packs. It turned out to be the injectors. When I pulled them I found a ring of gunk around the rim of the nozzle. I thoroughly sprayed them out with MAF sensor cleaner and re-installed. The misfire is gone and it idles and drives sooooooo much smoother.

 

I never thought stock injectors @ 75k could be a problem. I've always run 93 usually w/ no ethanol. I did change the fuel pump & filter/screen @ 60k or so. I was thinking maybe some gunk got through after the install. Also I installed a FP gauge around that time... I was thinking maybe some thread sealer tape or debris was introduced into the fuel line from that.

 

Anyways it sounds like your issue could be injector related. Have you checked the roughness monitor/misfire counts? You said it seems fine in OL so you could set the OL fuel map to 14.0 in the upper left region where it's normally in CL and see what happens.

 

Have you tried changing your DBW mapping to linear settings yet? I found that the stock mappings are all over the place. I'd be trying to hold the throttle steady and it would surge and hesitate. I thought it was bad MAF scaling for a while but eventually realized it was the DBW settings.

 

Clint

[LGTspecB1657615261]

I just put these injectors in... and it sucked balls. I hope to god its not the injectors! Would a FPR help at all? n00b at this stuff...

[SubyShop.com]

I just put these injectors in... and it sucked balls. I hope to god its not the injectors! Would a FPR help at all? n00b at this stuff...

 

how close are the flow ratings between the injectors?

 

Also, the stock timing profile doesn't have very smooth transitions between cells. Maybe Clint can post up the graph of his timing map. It's soooo smooth.

-Franz

[LGTspecB1657615261]

how close are the flow ratings between the injectors?

 

Also, the stock timing profile doesn't have very smooth transitions between cells. Maybe Clint can post up the graph of his timing map. It's soooo smooth.

-Franz

 

Static variance 0.4%. 825, 825, 825, 828

Here is my base timing A and max timing advance primary (attached). (not sure what the second one is for).

 

Both look weird in the low-end, but all of my ROM's have looked like that. Back when I was stg I and had no stutter the timing looked like this.