infamous 5MT low idle stall - Page 5

longassname · #61 01-21-2006, 11:38 AM

Not really Bill,

I wouldn't wait for it. A lot of it will be done as part of the stage 3 tuning which will be completed within two weeks. After that I will be asking everyone what they want to make sure I incorporate as many people's wishes and desires into it. So depending on what people want we will see. I also want to make sure we solve the 5mt stall problem with it if it turns out to be something better handled by the ECU than a dashpot. That's why I'm asking about the dashpot now.

SVXRide · #62 01-21-2006, 11:46 AM

Quote:

Originally Posted by longassname

Not really Bill,

I wouldn't wait for it. A lot of it will be done as part of the stage 3 tuning which will be completed within two weeks. After that I will be asking everyone what they want to make sure I incorporate as many people's wishes and desires into it. So depending on what people want we will see. I also want to make sure we solve the 5mt stall problem with it if it turns out to be something better handled by the ECU than a dashpot. That's why I'm asking about the dashpot now.

Michael,
Thanks for the quick response! I'm inclined to agree with Tom on the stalling issue - the engine control system is set up to work with an automatic trans and its inherent hydraulic "lag". Once you swap in the manual trans you lose that aspect of the overall control loop. I like your idea of reducing the pulse width as a way of addressing this.
It is curious that Tom's 6 spd doesn't stall. I don't know exactly how the 5spd varies from the 6 spd, but I'm guessing the 5spd transmissions don't have as much rotational mass...
-Bill (walking out to the garage to install a 2v5 chip....)

longassname · #63 01-21-2006, 11:47 AM

Tom, if it is air then the dashpot is the solution. When you talk about changing the way the IAC operates you are talking about major code changes. The direct hardware solution of the dashpot is much simpler and effective. The changes I can make to IAC operation through data are limited.

Now if it's a fuel problem that's a different story. I can address that directly by changing the minium pulsewidth to prevent engine stall.

Quote:

Originally Posted by TomsSVX

I feel the ECU is to blame. It is not setup for a Manual trans so when the engine is on decel, there is next to no rotational mass attached so it drops too fast for the IAC to compensate for. If you could fix it to speed up the IAC's reaction I feel the problem would be solved

Tom

TomsSVX · #64 01-21-2006, 11:53 AM

I think the air is to blame as well. Since I know so little of the coding in the ECU I had no idea it would be a huge task. Like I have said, it is due to the engine not the transmission so the thoughts of my 6 speed not stalling for any reason outside of my engine running properly s false. The trans makes no difference, I have a feeling that engine that may be using oil or have busted vaccum lines may be more prone to stalling. Also lightweight flywheels and pulley will not help. The dash pot seems like our only way out, I will go ahead and order one and see if I can get around to installing it

Tom

longassname · #65 01-21-2006, 11:55 AM

Bill,

I would most likely not reduce the minimum pulse width. If it's rich during the stall it's because there isn't enough air not because there is too much fuel. In this case the dashpot is needed. There is a minimum amount of air and fuel needed to keep the engine running. You can't just cut fuel to match not enough air and expect it to run. If it is lean during stall I will increase the minum pulse width and the problem will be fixed. This could also easily be the problem. In other cars it often is. If my car had a manual transmission I would answer this question on day 1 but it doesn't so one of those who does will have to try the dashpot.

Quote:

Originally Posted by SVXRide

Michael,
Thanks for the quick response! I'm inclined to agree with Tom on the stalling issue - the engine control system is set up to work with an automatic trans and its inherent hydraulic "lag". Once you swap in the manual trans you lose that aspect of the overall control loop. I like your idea of reducing the pulse width as a way of addressing this.
It is curious that Tom's 6 spd doesn't stall. I don't know exactly how the 5spd varies from the 6 spd, but I'm guessing the 5spd transmissions don't have as much rotational mass...
-Bill (walking out to the garage to install a 2v5 chip....)

TomsSVX · #66 01-21-2006, 11:57 AM

thinking about it more, I am not sure I will be a good test subject as my car doesn't stall. It does accasionally take a quick dive but the ECU recovers quickly

Tom

Earthworm · #67 01-21-2006, 11:57 AM

Mine (2002WRX) has stalled previously (after a thorough TB cleaning and the Stage I chip it stopped).

My dad's (not exactly sure which tranny but probably Impreza 4.11 cable clutch) never stalls.

My bet is still on a slow reacting IAC.

longassname · #68 01-21-2006, 12:00 PM

Ya it would be better if it was done on a car that has a worse problem. Perhaps someone would like to hire you to install a dashpot on their mt svx.

Quote:

Originally Posted by TomsSVX

thinking about it more, I am not sure I will be a good test subject as my car doesn't stall. It does accasionally take a quick dive but the ECU recovers quickly

Tom

TomsSVX · #69 01-21-2006, 12:03 PM

Well Shotgunslade just drove his car away a few hours ago. He said on his test drive it did not stall. It is only on occaision unless you are running a fuel pressure too high. My stage2v4 did it all the time because it was running too rich. This also helped me come to the conclusion of not having enough air. I just cranked out the idle screw a little until I got the stage2v5 as a temp fix

Tom

mbtoloczko · #70 01-21-2006, 12:25 PM

It did occur to me yesterday that there is one instance where the dashpot may not prevent the stall. I have found that sometimes during a long decel with the tranny in gear and coming up to a stop sign (say taking a freeway offramp), as I come up to the stop sign and put the car in neutral, the engine will stall. A dashpot will have allowed the throttle body to have closed long before I reach the stop sign, so it seems to me that the dashpot may not help here.

With my car, I don't think the stall has to do with the tranny having a pull clutch. There is no change in idle speed with the clutch engaged or disengaged. Turning the steering wheel when coming up to a stop will exacerbate the stall though. The extra load placed on the engine by the PS makes it more difficult for the engine to recover from a very low idle. I've cleaned the throttle body and IAC very thoroughly and all the vacuum lines are brand new, so I think the lightweight flywheels definitely contribute to the stalling.

TomsSVX · #71 01-21-2006, 01:30 PM

Yes but the Dash pot will allow the throttle to ease shut so they engine should be more stable at idle. I think it would even help the case of an extended stop like you mention.

Tom

Earthworm · #72 01-21-2006, 01:40 PM

Are they adjustable? It would have to hold the throttle for at least 10 seconds.

shotgunslade · #73 01-21-2006, 02:48 PM

Having driven the car some now, trip home from Beach Haven and around Princeton, I have experienced the stall a couple of times. A couple of observations, though. I think the clutch pedal has to be pushed completely to the floor in order to disengage fully the clutch, because there is difficulty downshifting into first gear, unless I stand on the clutch pedal, so I think at least one of the stalls may have been related to coming to a stop in first with the clutch pedal only almost to the floor. Also, I think giving the accelerator a very slight blip just up to 1500-1800 rpm right after disengagement as you are coming to a stop, allows it to settle more slowly into a stable idle. I think the dashpot might completely eliminate the problem, but I think some learned behavior will probably eliminate most occurrences.

Love the car. Will start a thread on my first impressions. Thanks very much Tom.

SVXRide · #74 01-21-2006, 03:25 PM

Quote:

Originally Posted by longassname

Bill,

I would most likely not reduce the minimum pulse width. If it's rich during the stall it's because there isn't enough air not because there is too much fuel. In this case the dashpot is needed. There is a minimum amount of air and fuel needed to keep the engine running. You can't just cut fuel to match not enough air and expect it to run. If it is lean during stall I will increase the minum pulse width and the problem will be fixed. This could also easily be the problem. In other cars it often is. If my car had a manual transmission I would answer this question on day 1 but it doesn't so one of those who does will have to try the dashpot.

Michael,
Agreed.
-Bill (2v5 install shifted to Sunday....Saturday spent on "BillStock" stock muffler mod v2...yes, stainless steel wool will cut your fingers if you're not careful

)

mohrds · #75 01-22-2006, 08:51 AM

Quote:

Originally Posted by shotgunslade

I think the clutch pedal has to be pushed completely to the floor in order to disengage fully the clutch, because there is difficulty downshifting into first gear, unless I stand on the clutch pedal, so I think at least one of the stalls may have been related to coming to a stop in first with the clutch pedal only almost to the floor.

Does your car use the donor car's pedal assembly or did you modify the SVX assembly to accept the clutch and brake pedals? One of the things I noticed when working on my swap is that the legacy pedal setup sits a good 3/4 - 1 inch closer to the firewall than the SVX brake pedal does. For that reason I mounted the individual pedals to the SVX assembly to keep the pedals at the same location as the SVX.

However, the swap isn't finished

so I can't say if this affects the idle issue or not. I can't even say if my car will suffer from the issue.

Doug