RESOLVED, nothing to see here

[tinyman392]

Really knowledgeable tech. Ran full diagnostics and did a visual/physical inspection from above and below.

Apparently there is no problem. He said these are designed to drop off pretty quickly, even when you're accelerating. Still didn't get an answer as to why it's hanging out in the negative and at 0 while driving.

Will someone reply, maybe with a video of your boost gauge from a stop, through the gears on local roads, and at speed on a highway?

Thanks!
John

Was this under hard acceleration or cruising? If you’re cruising then the exhaust pressure isn’t strong enough to spool the turbo and it’ll produce a vacuum. Even under a light load you might not produce any boost.

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[Deleted member]

Was this under hard acceleration or cruising? If you’re cruising then the exhaust pressure isn’t strong enough to spool the turbo and it’ll produce a vacuum. Even under a light load you might not produce any boost.

This is exactly the realization I came to from the time I last posted until I drove it home.

I put it down in gear and the turbo shot right up to 15psi. This accelerator pedal is so sensitive that the lightest touch gets the car moving swiftly, but to your point, not enough to spool up the turbo. I'll chalk it up to a learning curve and my general paranoia.

You really have to press down a bit more to see this spool up. I took it to a park with a long straightaway and flew through the gears, and boost was high and stable. I guess I was just driving this car too delicately before?

Going to close the book on this issue as everything seems normal. At 1500 miles and already feel an improved difference in performance, overall.

Thanks everyone for chiming in!

John

 

[Fatheadrr]

You need exhaust pressure to spool a turbo. Hence the phrase turbo lag. Cruising down the highway the turbo wont be spooling

 

[NoelPR]

Recommended reading
How a turbo engine works.

This was a very noob post. Im glad it was nothing bad.

 

[charleswrivers]

Yep... under light load, you should be seeing near 10 in vacuum. Under more load, but not accelerating, like maintaining speed on the interstate, you should be approaching 0... still probably a bit of vacuum. On the stock tune, you’ve really got to approach WOT to reach full boost. There’s quite a bit of partial throttle boost dampening that exists on our cars on the stock tune that’s different than older turbo cars.

Your original post talking about odd siren noises, not being able to rev past 4500 RPM (stock tune has no lower rev limit I’m aware of... clutch in on an aftermarket tune, launch control 2 step rev limit would exist) and some other things doesn’t sound right however. If you can’t build full boost (realize you will not reach the peak boost advertised by Honda for a variety of reasons... but should be within a few pounds if it) at WOT in 3rd gear at highway speeds when the engine is under decent load, you’d have a problem.

 

[Deleted member]

Yep... under light load, you should be seeing near 10 in vacuum. Under more load, but not accelerating, like maintaining speed on the interstate, you should be approaching 0... still probably a bit of vacuum. On the stock tune, you’ve really got to approach WOT to reach full boost. There’s quite a bit of partial throttle boost dampening that exists on our cars on the stock tune that’s different than older turbo cars.

Your original post talking about odd siren noises, not being able to rev past 4500 RPM (stock tune has no lower rev limit I’m aware of... clutch in on an aftermarket tune, launch control 2 step rev limit would exist) and some other things doesn’t sound right however. If you can’t build full boost (realize you will not reach the peak boost advertised by Honda for a variety of reasons... but should be within a few pounds if it) at WOT in 3rd gear at highway speeds when the engine is under decent load, you’d have a problem.

This was a very helpful, thorough explanation. Thank you! It's all making more sense to me. This is my first turbo car.

I don't want to try it again, but it definitely wouldn't rev past 4500 in neutral. Engine was fully warmed up with about 30 minutes of driving at the time.

 

[charleswrivers]

This was a very helpful, thorough explanation. Thank you! It's all making more sense to me. This is my first turbo car.

I don't want to try it again, but it definitely wouldn't rev past 4500 in neutral. Engine was fully warmed up with about 30 minutes of driving at the time.

You're welcome. The stock tune tends to make boost rise linearly with throttle input. This makes torque rise much more linearly with throttle input.

Aftermarket tunes will allow the turbo to be fully spooled as soon as there sufficient exhaust gas to do so... and is why you see huge torque spikes in the mid-range if you look at a dyno. As it is, Honda programmed their ECU to give a much more linear power delivery... and you’re going to have to really to pin the throttle to make the car to show full boost. It’s simply a characteristic of the car in how it was tuned from the factory. It does provide a nice and smooth power delivery when compared to how some turbo cars are very... ‘peaky’ in their power delivery.

Good luck. If you have more thought/concerns with what your car was doing in the original post, let us know.

 

[tinyman392]

This is exactly the realization I came to from the time I last posted until I drove it home.

I put it down in gear and the turbo shot right up to 15psi. This accelerator pedal is so sensitive that the lightest touch gets the car moving swiftly, but to your point, not enough to spool up the turbo. I'll chalk it up to a learning curve and my general paranoia.

You really have to press down a bit more to see this spool up. I took it to a park with a long straightaway and flew through the gears, and boost was high and stable. I guess I was just driving this car too delicately before?

Going to close the book on this issue as everything seems normal. At 1500 miles and already feel an improved difference in performance, overall.

Thanks everyone for chiming in!

John

Glad it was figured out. Yeah, turbos are designed to not pull boost unless under heavy load. This is what allows it to be fuel efficient when it needs to be an pull out power when it wants. Think about it this way, under no load, the engine takes in as much oxygen as an NA 1.5L motor. With boost, say 15PSI, the motor acts more like a 3.0L motor due to the amount of oxygen/air that it can take in.

 

[Deleted member]

Glad it was figured out. Yeah, turbos are designed to not pull boost unless under heavy load. This is what allows it to be fuel efficient when it needs to be an pull out power when it wants. Think about it this way, under no load, the engine takes in as much oxygen as an NA 1.5L motor. With boost, say 15PSI, the motor acts more like a 3.0L motor due to the amount of oxygen/air that it can take in.

Another super helpful post, thanks!!

 

[Deleted member]

Recommended reading
How a turbo engine works.

This was a very noob post. Im glad it was nothing bad.

Absolutely, this is my first turbo. So yeah, I'm a noob. But, I read a lot about how turbos work this afternoon. It all makes a lot more sense now.

Joined this forum to learn more about the car I recently purchased, and how to get the most out of it, including a better understanding of cars, in general.

Cheers,
John

 

[Deleted member]

As this is my first turbo car, I want to set a knowledge baseline (for myself) before I ask further questions. This way you guys know I'm following along, and you aren't wasting your time.

To my understanding a turbo works like this:
Exhaust exits the exhaust manifold and enters the turbo via the turbine inlet, which spins a turbine connected to a shaft that spins a smaller turbine on the opposing side of the housing, called the compressor inlet. That inlet sucks up ambient air and compresses it, which also causes a rise in air temperature. From there, the compressed air passes through the intercooler, which cools it to the suitable temperature before dumping it into the intake manifold at a fixed air/fuel ratio. The waste gate, connected to the turbo, regulates air quantity, feeding the correct amount into the the turbine inlet, but expelling the remainder into a down pipe, which leads to the exhaust that exits the vehicle.

If I have that correct, I have a question about waste gate operation.

Is it normal to be accelerating hard in 4th gear, pushing 75mph, and only see 12-13 psi, which soon falls while you're still hard on the accelerator pedal? Is that the waste gate regulating the proper amount of exhaust needed, and dumping the rest? That was my drive in to work this morning.

Thanks!
John

PS I don't want to just drive this car, I want to understand every inch of this car.

 

[PowerPerLiter]

As this is my first turbo car, I want to set a knowledge baseline (for myself) before I ask further questions. This way you guys know I'm following along, and you aren't wasting your time.

To my understanding a turbo works like this:
Exhaust exits the exhaust manifold and enters the turbo via the turbine inlet, which spins a turbine connected to a shaft that spins a smaller turbine on the opposing side of the housing, called the compressor inlet. That inlet sucks up ambient air and compresses it, which also causes a rise in air temperature. From there, the compressed air passes through the intercooler, which cools it to the suitable temperature before dumping it into the intake manifold at a fixed air/fuel ratio. The waste gate, connected to the turbo, regulates air quantity, feeding the correct amount into the the turbine inlet, but expelling the remainder into a down pipe, which leads to the exhaust that exits the vehicle.

If I have that correct, I have a question about waste gate operation.

Is it normal to be accelerating hard in 4th gear, pushing 75mph, and only see 12-13 psi, which soon falls while you're still hard on the accelerator pedal? Is that the waste gate regulating the proper amount of exhaust needed, and dumping the rest? That was my drive in to work this morning.

Thanks!
John

PS I don't want to just drive this car, I want to understand every inch of this car.

Your version of hard on the accelerator simply sounds like your not hard on the accelerator. I suspected this initially. Your car is fine. Observe the behavior and play with it to answer your own questions a bit, to put it simply.

 

[Deleted member]

Your version of hard on the accelerator simply sounds like your not hard on the accelerator. I suspected this initially. Your car is fine. Observe the behavior and play with it to answer your own questions a bit, to put it simply.

I had the pedal on the floor...

In 1st, the rpms shoot up, engine gets loud, but speed doesn't seem to match.

I do think there is an issue with the car, but I'm not technically savvy enough to diagnose, and Honda thinks all is fine.

So, I'm here for everyone's buy in.

 

[Fatheadrr]

Stop staring at the boost gauge and enjoy the car.

 

[Deleted member]

Stop staring at the boost gauge and enjoy the car.

You guys want to bash me, it's fine. It's the internetz, I can take it.

But, at least address my questions, too?

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