Turbo on 72mph, long distance, problems??

[CX7nCali]

The turbo is engaged around 72mph. So what are the long-term problems when driving 75mph with the turbo engaged all the time for long periods.

For example, when driving to Vegas, the turbo is engaged the whole trip.

This can't be good.?.

 

[otnielarencibia]

Nothing wrong.....

 

[jersey_emt]

The turbo isn't going to be boosting while cruising at 75mph.

 

[JOMO]

The turbo isn't going to be boosting while cruising at 75mph.

x2. If you have a boost guage you can see what we are talking about. You should be in Vac and not boost if your just cruising holding a certain rpm. But, if you just hit the gas a tiny weenie little bit, Then boost wil come in.

 

[CX7nCali]

Actually you can see the rpm take a jump between 70 and 75 mph.

If I'm cruising at 75mph, the rpm is around 2700.

The turbo kicks in at 2500 rpm.

Hence the question for long-term effects.

 

[Knox Joe]

Even at 2700 RPM your turbo isn't really spoolin unless your in too high of a gear.

If your just cruising in 6th on the interstate doing 75 you should be in vacuum.

You can't hear the turbo spooling can you?

 

[B1GHAM]

x2. If you have a boost guage you can see what we are talking about. You should be in Vac and not boost if your just cruising holding a certain rpm. But, if you just hit the gas a tiny weenie little bit, Then boost wil come in.

yes, just because you are in the rpm range for turbo engagement does not mean you are actually boosting. The BPV will release any boost if you are not under any acceleration. So, cruising @ 75 mph, the turbo is not boosting.

 

[Blackrose]

Boost is controlled by throttle not RPM. You can be cruising at 6K rpms and not be in boost.

 

[CX7nCali]

Ok, thanks. I thought it was regulated by RPM.

There's a huge differene in mpg between driving 65-70 mph versus 75-80.

I thought it was because the turbo was engaged.

I average 70-75mph and every tank of gas has been 17-18 mpg with 80 percent freeway driving. (FWD)

 

[Mr. Win]

MPG is effected by RPM but has nothing to do with the turbo.

 

[osu1steve]

MPG is effected by RPM but has nothing to do with the turbo.

Be careful here ... the more air you pull, the more fuel you dump. You will burn more fuel boosted at low rpm than pulling vacuum at 6 grand. Fuel consumption is effected by engine loading more than engine speed.

 

[jersey_emt]

Ok, thanks. I thought it was regulated by RPM.

There's a huge differene in mpg between driving 65-70 mph versus 75-80.

I thought it was because the turbo was engaged.

I average 70-75mph and every tank of gas has been 17-18 mpg with 80 percent freeway driving. (FWD)

That's because of the exponential effect on drag that increasing speeds has.

 

[osu1steve]

That's because of the exponential effect on drag that increasing speeds has.

It's actually a power, not exponential. Drag is proportional to velocity-squared (among other things), but who's counting??

 

[9Hooker]

There seems to be a lot of misinformation being spread here. Let's just get specific shall we...

1) Your turbo is always spinning. Always. It's job is to take exhaust air and, by way of a spindle, create a pressure increase on the other end. It doesn't know how to stop. That's where the all important wastegate comes in. The wastegate's job is to regulate the boost. If you are cruising, your turbo is trying to do it's job, taking the pressure from the exhaust and trying to create pressure in the intake tract. The wastegate opens like a, hmmmmm, like a top to a 2 liter coke bottle... Yeah that's it, good analogy. When the wastegate opens, it releases some (or all) of the gases discharged from the motor BEFORE it gets to the turbo like opening the lid on your coke bottle. When you the driver demands more power from the motor, a little vacuum line tells the wastegate (or bottle lid) to CLOSE. Now more pressure can be created in the gases coming out of the motor in order to spin the turbo FASTER this creating boost. Remember, boost is directly controlled by the wastegate (which is controlled by engine loading), not the turbo directly, not your foot on the gas pedal (not directly anyway), not what gear you are in, nada. To get the turbo going from it's idle state (still spinning really fast and wanting to create boost) with the wastegate open to full speed, wastegate fully closed is called spool up time, or lag. The bigger the turbo, or the more boost created, the longer the lag till full boost. I'm getting ahead of myself for the purposes of this discussion.


In re: the rpm difference between x and y. This has everything to do with the automatic transmission and nothing to do with anything else. Automatic tranny's have torque converters. The long and short of that is that the torque converter slips, much like having your foot resting a little too much on the clutch pedal. Normally cruising on a flat stretch of road the torque converter will LOCK and not allow any slip. The locking in effect drops the rpm's a bit. How much depends on how much slipping. If you have to crest a hill or have need for a little more horsepower up to but not including a shift to a lower gear, the torque converter will unlock, raising the rpm and raising the available horsepower. If the car needs more than just a simple unlock can provide, the car will shift down a gear.


In re: gas mileage at higher speeds. That has to do with aerodynamic drag and parasitic drag. When you double the speed, you quadruple the power required.

Clear as mud?

 

[jersey_emt]

It's actually a power, not exponential. Drag is proportional to velocity-squared (among other things), but who's counting??

Semantics, shmemantics.

It's a subexponential increase

 

[offset_98]

Turbos are made to run...I have diesel trucks in my fleet w/ over 200k on them and the turbos are fine.

 

[CX7nCali]

In re: the rpm difference between x and y. This has everything to do with the automatic transmission and nothing to do with anything else. Automatic tranny's have torque converters. The long and short of that is that the torque converter slips, much like having your foot resting a little too much on the clutch pedal. Normally cruising on a flat stretch of road the torque converter will LOCK and not allow any slip. The locking in effect drops the rpm's a bit. How much depends on how much slipping. If you have to crest a hill or have need for a little more horsepower up to but not including a shift to a lower gear, the torque converter will unlock, raising the rpm and raising the available horsepower. If the car needs more than just a simple unlock can provide, the car will shift down a gear.

This is something I had been wondering as well, that could be a factor. Prior to my last visit to the dealer when they flashed the computer, 2500rpm was near 80mph. I'm wondering if something was affected with the torque convertor lockup at cruising speeds? If it isn't locking as it should, then it would explain the higher rpm at the same mph, and the loss of mpg.

As far as my other question regarding the turbo, I should rest comfortably and not worry about any long-term damage if I take a long trip at 80 mph?

It is interesting though, there is a visible "jump" from 2300 to 2600 or so in rpm at cruising speed when gradually accelerating. Jump versus gradual increase. This is why I thought the turbo (or wastegate, etc) was engaging, etc.

 

[Blackrose]

You are incorrect about the wastegate. The only time a wastegate is open is when the boost level to push the spring is reached. Otherwise that valve is closed at all times. Not saying yor wrong about anything else but you should post about other people spreading wrong info when yours is incorrect.

And no your turbo is not controled by your gas peadale but it was the easiest way to simplify it. If the thread starter wants more detailed info he can google the info, go to how things work.com, or pm me and all these things will get him the technical info he might want\need.

1) Your turbo is always spinning. Always. It's job is to take exhaust air and, by way of a spindle, create a pressure increase on the other end. It doesn't know how to stop. That's where the all important wastegate comes in. The wastegate's job is to regulate the boost. If you are cruising, your turbo is trying to do it's job, taking the pressure from the exhaust and trying to create pressure in the intake tract. The wastegate opens like a, hmmmmm, like a top to a 2 liter coke bottle... Yeah that's it, good analogy. When the wastegate opens, it releases some (or all) of the gases discharged from the motor BEFORE it gets to the turbo like opening the lid on your coke bottle. When you the driver demands more power from the motor, a little vacuum line tells the wastegate (or bottle lid) to CLOSE. Now more pressure can be created in the gases coming out of the motor in order to spin the turbo FASTER this creating boost. Remember, boost is directly controlled by the wastegate (which is controlled by engine loading), not the turbo directly, not your foot on the gas pedal (not directly anyway), not what gear you are in, nada. To get the turbo going from it's idle state (still spinning really fast and wanting to create boost) with the wastegate open to full speed, wastegate fully closed is called spool up time, or lag. The bigger the turbo, or the more boost created, the longer the lag till full boost. I'm getting ahead of myself for the purposes of this discussion.

 

[9Hooker]

You are incorrect about the wastegate. The only time a wastegate is open is when the boost level to push the spring is reached. Otherwise that valve is closed at all times. Not saying yor wrong about anything else but you should post about other people spreading wrong info when yours is incorrect.

facts gotted (sic)



The way you word it, we are running around at full boost at all times. Why then is there a vacuum line coming off the top of the wastegate? Explain to me then how I can be at 5000 rpm and not be in boost? That's PLENTY of air going through the motor every 2 revolutions to be at full boost, yet miraculously I'm not. It's because the waste gate is open. Nearly 30% of all exhaust gases can be diverted through the wastegate.

There is a vacuum line on the wastegate that goes to the intake manifold? Why is this? It's to assist the wastegate spring in staying open when no boost is required. Very similar to the power assisted brakes we all have.

The red hose on the right side of valve cover in this pic:
http://www.edelbrock.com/media/news/2005/automotive/images/1509.jpg

installation instructions: page 14, 3-13:

http://www.greddy.com/img/PHP/products/pdf/776.pdf

 

[Mr. Win]

true.

Be careful here ... the more air you pull, the more fuel you dump. You will burn more fuel boosted at low rpm than pulling vacuum at 6 grand. Fuel consumption is effected by engine loading more than engine speed.