Car Bogging During Autocross
Happy Saturday all! 
I just got back and I was experiencing some issues with the engine bogging down on corner exit. Usually around 3.8k RPM, but there was a few times higher around 6k. Only 1 SMG related error code to boot as well. I think I figured out what my issue is, but I wanted to come here and see what everyone else thought of my conclusion or thoughts as well.
My initial thought for this was potentially a tune issue. My engine has been rebuilt, I am running a velocity stack setup on a MAP sensor, a modified exhaust, and a Walbro 255lph pump. Nothing too crazy. I initially thought the feeling was more similar to when the stacks were untuned and the car was bucking. On the drive home I was unable to replicate the issue which made me start looking elsewhere. To note, I started the day with a half a tank of gas. Maybe slightly under half. Also I was running with TC Full off.
Unfortunately I didn't take any good pictures of the course to show the amount of elevation change throughout, but we are in WV and its a very hilly place. Pretty much uphill or downhill the whole time. Today's layout featured quite a few relatively "high speed" right hand turns. These would either be combined with or followed by an uphill slope. These turns are where I noticed my issue most prominently. Along with the start, which was a slight uphill climb and I did get some bogging around the end of the day. So here were the few ideas I came up with on the drive home.
Potential Cause #1:
SMG Error Code 59. I was having some issues with my clutch slave and using launch control. This has been a recurring issue for me but I decided to replace it after today just to be safe. This was only an issue at standstill, car shifted fine otherwise. I thought maybe it could be playing some games with the ECU and just causing the car to bog down because the slave was oscillating or something. This one was a stretch but I figured I would share it with you guys anyways.
Potential Cause #2:
Rough Tune. Like I said earlier, this initially felt like when the stacks were untuned. I recently replaced both precat O2's and the tune was done with the lesser performing ones that came before. Presumably stock and the car has 172k on the chassis. I know nothing of how this would work, but I thought maybe this could have had my tune done based on poor information given or interpreted by these. I do have an independent wideband that we used for the tune. This was a little shaky, but I was willing to go with it for the time being. I believe that option 3 is the winner here though.
Potential Cause #3:
Fuel Starvation. I've read about our cars having issues in sweeping right handers due to pump location. Although I didn't really think that this course setup would be fast enough to cause this issue. Although I started reading more into it and it seems like this really could be the culprit for my issue. I believe Buildjournal noted having this issue even more when switching to their Walbro pump. It made sense as I started seeing this issue more and more as the day went on. Starting around run 3, then getting unbearable and ruining times for the whole second session. Along with the locations I was seeing this issue made total sense to me and was kind of my eureka moment on the way home.
As for a solution, assuming I am right and that you guys agree. Obviously the simple and quick solution is do not run an event on half a tank of gas. I really wish I thought about this while I was there so I could test and avoid half of this post. The more thorough solution would be to setup a second pump on the driver side, like with bimmerworlds fuel starvation kit. My car is officially done with daily duty and she is on her way to becoming a pure autocross/track day car. So this will be something I will eventually take care of. This requires you to drill into the blocked off post on your OEM pump side unit. Mine has this piece broken off and had to be sealed up.
Does anyone have any ideas on what I could do to create a new attachment point here? I would like to avoid spending more money on a whole unit if possible. My only guess is buying a separate plastic nipple and securing it to the housing. Although I would worry about having a tight seal and material durability coming in contact with fuel. (Heres a pic of the OEM housing with an attached nipple after being drilled open)
Any feedback is appreciated! Thanks guys :P
I just got back and I was experiencing some issues with the engine bogging down on corner exit. Usually around 3.8k RPM, but there was a few times higher around 6k. Only 1 SMG related error code to boot as well. I think I figured out what my issue is, but I wanted to come here and see what everyone else thought of my conclusion or thoughts as well.
My initial thought for this was potentially a tune issue. My engine has been rebuilt, I am running a velocity stack setup on a MAP sensor, a modified exhaust, and a Walbro 255lph pump. Nothing too crazy. I initially thought the feeling was more similar to when the stacks were untuned and the car was bucking. On the drive home I was unable to replicate the issue which made me start looking elsewhere. To note, I started the day with a half a tank of gas. Maybe slightly under half. Also I was running with TC Full off.
Unfortunately I didn't take any good pictures of the course to show the amount of elevation change throughout, but we are in WV and its a very hilly place. Pretty much uphill or downhill the whole time. Today's layout featured quite a few relatively "high speed" right hand turns. These would either be combined with or followed by an uphill slope. These turns are where I noticed my issue most prominently. Along with the start, which was a slight uphill climb and I did get some bogging around the end of the day. So here were the few ideas I came up with on the drive home.
Potential Cause #1:
SMG Error Code 59. I was having some issues with my clutch slave and using launch control. This has been a recurring issue for me but I decided to replace it after today just to be safe. This was only an issue at standstill, car shifted fine otherwise. I thought maybe it could be playing some games with the ECU and just causing the car to bog down because the slave was oscillating or something. This one was a stretch but I figured I would share it with you guys anyways.
Potential Cause #2:
Rough Tune. Like I said earlier, this initially felt like when the stacks were untuned. I recently replaced both precat O2's and the tune was done with the lesser performing ones that came before. Presumably stock and the car has 172k on the chassis. I know nothing of how this would work, but I thought maybe this could have had my tune done based on poor information given or interpreted by these. I do have an independent wideband that we used for the tune. This was a little shaky, but I was willing to go with it for the time being. I believe that option 3 is the winner here though.
Potential Cause #3:
Fuel Starvation. I've read about our cars having issues in sweeping right handers due to pump location. Although I didn't really think that this course setup would be fast enough to cause this issue. Although I started reading more into it and it seems like this really could be the culprit for my issue. I believe Buildjournal noted having this issue even more when switching to their Walbro pump. It made sense as I started seeing this issue more and more as the day went on. Starting around run 3, then getting unbearable and ruining times for the whole second session. Along with the locations I was seeing this issue made total sense to me and was kind of my eureka moment on the way home.
As for a solution, assuming I am right and that you guys agree. Obviously the simple and quick solution is do not run an event on half a tank of gas. I really wish I thought about this while I was there so I could test and avoid half of this post. The more thorough solution would be to setup a second pump on the driver side, like with bimmerworlds fuel starvation kit. My car is officially done with daily duty and she is on her way to becoming a pure autocross/track day car. So this will be something I will eventually take care of. This requires you to drill into the blocked off post on your OEM pump side unit. Mine has this piece broken off and had to be sealed up.
Does anyone have any ideas on what I could do to create a new attachment point here? I would like to avoid spending more money on a whole unit if possible. My only guess is buying a separate plastic nipple and securing it to the housing. Although I would worry about having a tight seal and material durability coming in contact with fuel. (Heres a pic of the OEM housing with an attached nipple after being drilled open)
Any feedback is appreciated! Thanks guys :P
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