My Half Baked "Studder" Theorey

I think I have encountered the dreaded "studder" on a few occasions. It seems to happen when I drop the clutch fairly agressively at medium full throttle. Because I don't like the sensation or performance when this phenomenom occurs (who does?), I have learned to almost completely avoid it. If a hard acceleration is required, I will refrain from dropping into a lower gear until rpms are over 4k and then only moving up gear a while substantial boost is being developed paying subtle attention to how I use the clutch to apply the next ratio.

 

I believe it has to do with the entire turbo AWD drive train. There is alot of torque going to 4 wheels with all attandant gear (transfer case, drive shafts, tranny, 4 power applying wheels/tires) and this can cause a studder under load. This is because although the turbo boxer feels like a strong 6 or even 8 cylinder car, it's only a 4 banger and there isn't the flywheel mass to bring complete and direct control over the rest of the drive train. The drive train itself is full of little connections that are flexible to one gegree or another. It has to be that way or it would break. These things don't all act in concert unless you can figure out how to get them all in tune and playing together.

 

The only reason we can see such sweet power from the turbo 2.5 boxer engine is the ECU angine management system. It does amzing things but it can't overcome the laws of physics.

 

Like I said, the theory is half baked.

My 2.0 liter 4 cyl Eagle Talon TSi AWD has much more power than my Legacy and I've never had the stutter problem on that car in either stock form or in any of it's various modded incarnations. I've also owned 4 other turbo'd DSM's, and never noticed a stutter.

 

 

Also, I notice the stutter even if I'm easy with the clutch. If I'm in gear, and then press the throttle anything more than 50%, if it's in between 2k-4k, it'll stutter.

Well, so much for my theorey. I guess I don't suffer from the studder.

the word is spelled theory.

 

Thanks. You have a wonderful future as a spell checker. Your parents must be so proud of you. I know I am.

Glad to help!

 

You're trying your hardest and that is just wonderful. Keeep it up.

The word is spelled "stutter".

 

 

But seriously, even at stage 2 and not much of the old stutter left except for maybe a minute when the engine is still cold, I have to say that I agree about driveline squishiness, even with a hardened transmission mount - "ping" the driveline with an agressive shift into 2nd and I get a nice oscillation for a second or so that feels like someone's trying to shake my head off.

The word is spelled "stutter".

 

 

But seriously, even at stage 2 and not much of the old stutter left except for maybe a minute when the engine is still cold, I have to say that I agree about driveline squishiness, even with a hardened transmission mount - "ping" the driveline with an agressive shift into 2nd and I get a nice oscillation for a second or so that feels like someone's trying to shake my head off.

 

The forum seems to have combined "shudder" with "stutter" to get "studder". At least that's how I use the term.

 

The shift "oscillation" you describe is what I was thinking was the aformentioned studder which, I guess, I don't have.

My 2.0 liter 4 cyl Eagle Talon TSi AWD has much more power than my Legacy and I've never had the stutter problem on that car in either stock form or in any of it's various modded incarnations. I've also owned 4 other turbo'd DSM's, and never noticed a stutter.

 

 

Also, I notice the stutter even if I'm easy with the clutch. If I'm in gear, and then press the throttle anything more than 50%, if it's in between 2k-4k, it'll stutter.

 

^Same thing happens to me when i'm light on the throttle. It feels really weird but hey i guess every car has its quirks.

So the studder is different from bucking? Or does studdering cause bucking? Does bucking cause studdering?

 

All I know is that if I'm careless/thoughtless with the clutch and throttle I'll get a sensation that I don't care for so I "naturally" avoid it. Maybe it has to do with my vocation wherein one of the techniques I use to maximize performance is the avoidance of habits that lead to excess recovery efforts which while necessary and important skills do not advance execution.

Drive By Wire Programming. Learn it. Love it.

Drive By Wire Programming. Learn it. Love it.

 

+1

Sti tranny mount helped a bit with a similar low-speed issue on our '98. N/A, of course.

The studder/stutter has nothing to do with the engine, it's all a result of the dual-mass flywheel in the car...swap that out....no more studder (or stutter either!).

The studder/stutter has nothing to do with the engine, it's all a result of the dual-mass flywheel in the car...swap that out....no more studder (or stutter either!).

What aftermarket flywheel would you suggest? I'd really love to get rid of the stuttering problem I h-h-h-h-have.

What aftermarket flywheel would you suggest? I'd really love to get rid of the stuttering problem I h-h-h-h-have.

 

Anything that is not dual-mass...they are offered from several different vendors, Exeedy, Spec, etc.

What about the 07 spec B? I doubt that it would have a dual mass flywheel but yet I still have the "issue".

 

The stutter is not caused by a duel mass flywheel but most definitely has something to do with the ecu or throttle by wire.

I have a slight studder some times when at partial throttle, I've never noticed it at full throttle. I have heard that some tunes get rid of it, which obviously suggests the OEM tune is the culprit, and others have pointed at the dual mass flywheel.

:mystery:

The studder/stutter has nothing to do with the engine, it's all a result of the dual-mass flywheel in the car...swap that out....no more studder (or stutter either!).

 

If it's the flywheel, how come it goes away temporarily after an ECU reset, and completely with a TDC map ?

^ +1 to that

I'm inclined to believe that it's a tuning issue with being too rich. I can reproduce something similar with my Talon when the car has too much gas, there's hesitation until the rpms get higher where I had leaned it out somewhat. I fixed it by leaning out everything

Hmmm... I'm inclined to believe it's the "tune" as opposed to the flywheel myself. Maybe the "too rich" theory posed by rochNY91tsi. I've never suffered from the dreaded "studder", "stutter" or even a stammer.

The studder/stutter has nothing to do with the engine, it's all a result of the dual-mass flywheel in the car...swap that out....no more studder (or stutter either!).

 

People on this forum have reported that the stutter is slightly more noticable after switching to a single mass flywheel. I also think the problem lies somewhere in the ECU. Either it is the tune/map or what the ECU "learns."

I think there is a differnence, between the stutter and the clutch issue. I have a 5eat, i have no stutter but i do have the werid engagment feeling when i am light on the throttle. The stutter has to do with the tune, the weird hesitations have to do with the flywheel.

I recently went back to full recirculation on my bypass valve and could've sworn the slight stutter I was sometimes getting subsided.

I cleaned my MAF sensor yesterday and so far the engine is the smoothest I've ever noticed (used CRC MAF sensor cleaner in case you're going to ask).

The bypass valve thing could be a psychological thing but the cleaning of the MAF sensor was definitely not. I haven't tried to recreate the stutter but I'll be trying to in the next few days. Although there was only a short period of time when I did have that stutter anyway, most of the time is was barely there.

Joon25, did you reset the ECU (e.g., disconnect the battery) during this MAF cleaning?