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Discussion Starter · #1 ·
Hi. I recently purchased a new ST. It's got about 4500 miles on it. About a month ago I noticed an uneven acceleration at half throttle. I first noticed it on the interstate passing slow traffic.

So I started to explore the issue so I could explain to the dealer exactly what I was experiencing. Light throttle and full throttle there seems no problem. Nice and smooth acceleration. About half throttle or so, it just kind of surges off and on. It's just not delivering power smoothly. It still accelerates and the surging is extremely subtle, but it is there.

I'd say roughly the 2500-4000 rpm range. Not really sure beyond that. I have hit half throttle and slowly pressed the pedal to full throttle. As long as the boost is in the 13-ish psi range, it surges. At some point on the throttle, the boost jumps up to 17-ish psi and the surging stops, you can feel the extra power and the acceleration is smooth as glass. Light or no boost is smooth as well.

Now, I'm new to a turbo. I was a little surprised at the sudden extra boost at whatever point on the throttle it does it. I thought it'd just build boost linearly throughout the rpm range, but this seems to be controlled depending on throttle position. Is this right?

I did disconnect the wire to the sound symposer (a useless feature for me). I reconnected it and didn't change anything. No codes. Premium fuel.

So armed with a good understanding of how to recreate the problem, I took it to the dealer. The tech said I was experiencing turbo lag. I'm pretty confident this is not turbo lag. The turbo is well spooled up when it's surging. I was a little worried they'd not be able to verify the complaint, because it is subtle and I'm used to the car and know exactly when it does it. So they said I can schedule a test drive with the tech so I can show him what's going on.

Until then, I figured I'd pick the brains of other ST owners and see if anyone has experienced this, if it's normal, or if there might be some ideas to have the tech check.

I'm fairly handy with fixing cars, but I'm sure there's a lot of new fangled stuff under the hood I'm not accustomed to. So if there's anything I could try, I'm happy to do it myself, so long as it doesn't mess with the warranty.

Ideas?

Thanks in advance.
 

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Can you recreate the issue in sport mode also?
Go to a local meet and have someone else with a lot of miles on the ST drive the car and see if they notice it.

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Discussion Starter · #3 ·
Can you recreate the issue in sport mode also?
Go to a local meet and have someone else with a lot of miles on the ST drive the car and see if they notice it.

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Well, I hate to be a newb, but what is the sport mode? Consider my interest piqued.

I don't know if there's a local meet here. I'll look into it.

Thanks.
 

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Well, I hate to be a newb, but what is the sport mode? Consider my interest piqued.

I don't know if there's a local meet here. I'll look into it.

Thanks.
Press the ESC button in front of the shifter.
Is this a Focus or Fiesta?

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Discussion Starter · #6 ·
Press the ESC button in front of the shifter.
Is this a Focus or Fiesta?

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Thanks

Okay, sport mode made no difference. It's a Focus.

I experimented a little more this morning. Instead of just jabbing it to half throttle, I slowly pressed the pedal and watched the boost gauge. Boost builds with the pedal slowly up until about 1/3 of pedal travel, then the boost plateaus at about 13-ish psi (could be closer to 11-12) until about 3/4 pedal travel when it sudden boosts up to about 17-ish psi. It's during that period where the boost has plateaued that the power delivery isn't smooth.

Is this the way the boost works on these cars or is something amiss with mine?
 

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I've noticed a similar issue with my totally stock '16 as well. You can hear the BPV/BOV opening and closing at about half throttle, and ~13psi boost. Once you go closer to WOT, the BPV completely shuts, boost jumps, and power comes on hard...If you're in 1st or 2nd, it will usually break the tires loose. This is one of my only complaints about the car. The issue is made worse with a tune also. I'm wondering if you run the BPV off of the manifold vacuum/pressure directly, and skip the electronic control portion, if this issue would go away. I never mentioned the issue to my dealer, as I know it wouldn't go anywhere, and it would just result in them taking the car out for a joy ride. IMO, this is operating as designed, even though I don't like it. The GM 2.0DI Turbo doesn't operate like this, and I don't notice this in the Escape or Edge 2.0 setups, but the Escape/Edge are autos, so it may be masking it?

If the tech thinks it is turbo lag, he doesn't know what he's talking about or looking at. It most certainly is NOT turbo lag, as like you said, the turbo is already spooled up. This engine hardly has any turbo lag anyway.
 

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Discussion Starter · #10 ·
Speed, RPM, what gear you're in and whether you're on level ground or a hill might help here.
Any gear, but it is easiest to notice in 5th or 6th on the interstate. I have noticed it in 3rd and 4th, but it's not as easy to feel as the car accelerates faster, not to mention any road in which trying it 3rd or 4th means you're likely going to offend a nice police man watching the roads.

Speed, obviously depends on what gear you're in. RPM, I'd say it's most noticeable in the 2.5-4k range, or at least that's the conditions that is most conducive to noticing.

It does it on level ground as well, but is more noticeable on an incline. I can't speak if that's because the engine is loaded more or if it's just a matter that the car accelerates at a slower rate giving you more time to notice.

I'm limited in just how much testing I can do because I'm in traffic and that limits the distance you have to actually try it, because even though it's not right, the car is still accelerating at a decent clip. The interstate gives me the best testing environment.

The feel of what is happening is hard to describe. It is like bursts of different power levels, maybe 1/4 to 1/2 second intervals. Or like the computer is reacting to inconsistent sensor data, but it has not thrown a code. Most interesting to me at this point is why it seems to only do it when the boost has plateaued in the 13-ish psi range.
 

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Discussion Starter · #11 ·
I've noticed a similar issue with my totally stock '16 as well. You can hear the BPV/BOV opening and closing at about half throttle, and ~13psi boost. Once you go closer to WOT, the BPV completely shuts, boost jumps, and power comes on hard...If you're in 1st or 2nd, it will usually break the tires loose. This is one of my only complaints about the car. The issue is made worse with a tune also. I'm wondering if you run the BPV off of the manifold vacuum/pressure directly, and skip the electronic control portion, if this issue would go away. I never mentioned the issue to my dealer, as I know it wouldn't go anywhere, and it would just result in them taking the car out for a joy ride. IMO, this is operating as designed, even though I don't like it. The GM 2.0DI Turbo doesn't operate like this, and I don't notice this in the Escape or Edge 2.0 setups, but the Escape/Edge are autos, so it may be masking it?

If the tech thinks it is turbo lag, he doesn't know what he's talking about or looking at. It most certainly is NOT turbo lag, as like you said, the turbo is already spooled up. This engine hardly has any turbo lag anyway.
So are you feeling a slightly uneven acceleration during the half throttle ~13 psi boost? I'm assuming you are having this same plateau in which the boost is stuck there until that place on the throttle it jumps up?

I don't hear the any BPV/BOV at all, but this is my first turbo car so I'm not sure what to listen for. But I don't hear anything at all like a mechanical sound. No difference in sound really, just a feel. I'm not sure how the BPV/BOV is supposed to work either. Do they try to regulate the pressure, or just a safety net for over boost conditions?

To be fair to the tech, it's not an easy thing to notice and he might have assumed I was feeling something different.
 

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I feel like my 14st does what your describing. Ive only driven it about 400 miles since i bought it so i wasn't sure if it was normal or not. honestly i thought it was just how the car runs. To me it almost feels like an on/off switch at part throttle. Im going to try to see if i can easily duplicate the situation.

I can say that i don't think its turbo lag.I had a brand new SRT-4 in 2005 and it did not do this. I felt like that car didn't have much turbo lag at all and the ST feels like its already ready to go just off idle. My dad hard a 944 turbo, talk about turbo lag. that car didn't build boost until around 4k rpm.
 

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Might be a wastegate adjustment problem. My Fiesta ST had this problem until I replaced it with a Tune+ ewg.

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Discussion Starter · #14 ·
I feel like my 14st does what your describing. Ive only driven it about 400 miles since i bought it so i wasn't sure if it was normal or not. honestly i thought it was just how the car runs. To me it almost feels like an on/off switch at part throttle. Im going to try to see if i can easily duplicate the situation.

I can say that i don't think its turbo lag.I had a brand new SRT-4 in 2005 and it did not do this. I felt like that car didn't have much turbo lag at all and the ST feels like its already ready to go just off idle. My dad hard a 944 turbo, talk about turbo lag. that car didn't build boost until around 4k rpm.
Were you able to duplicate the issue?
 

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Discussion Starter · #15 ·

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Do a pull with an acessport. Then look at boost level vs RPM. Or get a Bluetooth dongle to monitor your ecu during a pull. There are android and Apple apps to monitor boost and rpm. This and ewg monitoring should pinpoint the problem. Then use the instructions on the turbosmart install guide to adjust your reg. Hth.

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Discussion Starter · #17 ·
Do a pull with an acessport. Then look at boost level vs RPM. Or get a Bluetooth dongle to monitor your ecu during a pull. There are android and Apple apps to monitor boost and rpm. This and ewg monitoring should pinpoint the problem. Then use the instructions on the turbosmart install guide to adjust your reg. Hth.

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I wasn't planning on getting the Turbosmart, just pointing out the "more consistent boost delivery" and wondering if it's a normal operation...which would suck.

I don't have an accessport, but could probably get a dongle. What is "ewg monitoring"?
 

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This happens to my 17 ST1 as well. I am pretty confident is is directly related to the electronically controlled BPV. For me its under partial throttle usually towards the end of any gear. Your BPV activates and expels the unused/excess compressed air from the turbo back into the intake. So no matter how fast your going or what your RPM's are at the time...this is going to effect any torque/power your FEELING. I positive the BPV keeps cutting/recirculating your boost back, multple times about 1-2 seconds apart.......I didnt understand this until i installed my intake and could actually hear the BPV and when it was activating. Under partial throttle at higher RPM's (maybe between 3-5k) i would hear short activations (psht, psht) kind of like the BPV didn't know when to activate....almost like it was anticipating my letting my foot off the throttle.

If it's bothering you that much, I would get an aftermarket BPV/BOV and also a symposer delete kit (with the port) and run the BPV/BOV off of the symposer for a true vacuum operated valve instead of the glitchy electronic solenoid we seem to have.
 

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Discussion Starter · #19 ·
This happens to my 17 ST1 as well. I am pretty confident is is directly related to the electronically controlled BPV. For me its under partial throttle usually towards the end of any gear. Your BPV activates and expels the unused/excess compressed air from the turbo back into the intake. So no matter how fast your going or what your RPM's are at the time...this is going to effect any torque/power your FEELING. I positive the BPV keeps cutting/recirculating your boost back, multple times about 1-2 seconds apart.......I didnt understand this until i installed my intake and could actually hear the BPV and when it was activating. Under partial throttle at higher RPM's (maybe between 3-5k) i would hear short activations (psht, psht) kind of like the BPV didn't know when to activate....almost like it was anticipating my letting my foot off the throttle.

If it's bothering you that much, I would get an aftermarket BPV/BOV and also a symposer delete kit (with the port) and run the BPV/BOV off of the symposer for a true vacuum operated valve instead of the glitchy electronic solenoid we seem to have.
Thanks Loxias. It appears this might be normal operation, which is a bummer. I would've thought it would have been a common complaint if normal though. Sucks because during this period it feels like the engine is being held back.

I'm still going to take to the dealer and drive with the tech to show him what it's doing, if for nothing else to make sure its documented.
 
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