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.

[Blackrose]

Wow you are wrong.

I will do a quick write up one on WG's and one on turbos.

A WG is a diaphram with a spring against it to create a certain level of resistance. This diaphram is conected to a valve that alows the exhaust gasses to bypass the turbine and regulate its speed. Thus regulating boost pressure. The vac line is hooked up to the WG so that it will pump pressure against the diafram. During idle the car is generating vacume and thus is increasing the springs pressure against the diaphram. As the car builds boost, the vac line also builds up pressure and it runs down this diaphram and pushes against it. As the pressure reaches a point where the spring will start to depress it will actuate the valve and alow exhause gasses to bypass the turbine. When the intake mani pressure drops (ie. Gear change) the car returns to vacume and then the spring returns back into place and clses the valve.

I personally know this cause I have a external WG that vents to atmosphere. When the car is sitting at idle I can hold my hand right up to that dump tube and there will be no air flow. And even if it was very slight I would at least feel heat and I dont. Wastegates are closed during engine vac. Period.

Turbos.

A turbo charger requires two things to work properly. Pressure and energy.

As you depress the gas in say my MSP, you sopen the throtle plate. As you do this the motor increases the gas into the intake to compensate for the increase in air. This generates more energy and exhaust pressure. So as the RPM's increase so does exhhuast pressue and energy. So lets say we run the car up to 5K RPM's and then we want to hold the motor at that speed. We release the gas and hold it a a point a dwell. when we do this the throtle plate closes and the ECU sends less gas into the intake. This causes the energy in the car to plunge. This also causes the turbine to decrease in speed rapidly. If you were to sudenly hit the gas again the casr would send more fuel and more energy would be created and the turbo would spol up again very rapidly. Just remember your car can be at 8k RPMs but not be generating much energy or exhaust for that matter.

Any questions?


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

[dmitrik4]

anyway...cruising at 75, or 80, or 90 will be fine in your CX-7 (or really any properly-maintained modern car). the faster you go, the more fuel you'll use, but nothing is going to break.

[9Hooker]

Blackrose,

I'm always the first to admit when I'm wrong about something. Thanks for giving me the opportunity to step on my proverbial junk. I'm not making excuses for being wrong, but... (there's always a but) It's been a LONG time since I've been a car wrench monkey myself. Much has been lost over the years (coming on 6 for cars, 4 on motorcycles!!!)

Yep, I just showed my slip. Sorry for the misinformation. I will limit myself to spewing garbage to once in a blue moon.

[Blackrose]

Hey its all good. Im glad your adult enough to come back and say "hey I was wrong". Hell I can remember a time when I swore a turbo recycled exhaust back into the intake and thats how the car got boost..lol. Besides I like a good debate, and hopefully someone learned something here. As for the original post. You can shoot doen the highway at a steady 120 and your turbo will not have any more stress than it can handle. Just remember your car is turbocharged so keep a close eye on your fluids, run good gas and let that baby cool down before you shut the car off if you have been driving it hard. If you follow these simple steps your turbo should have a nice long life.

Blackrose,

I'm always the first to admit when I'm wrong about something. Thanks for giving me the opportunity to step on my proverbial junk. I'm not making excuses for being wrong, but... (there's always a but) It's been a LONG time since I've been a car wrench monkey myself. Much has been lost over the years (coming on 6 for cars, 4 on motorcycles!!!)

Yep, I just showed my slip. Sorry for the misinformation. I will limit myself to spewing garbage to once in a blue moon.

[mikey1981]

Not to break up the fact party here, but i observe better gas mileage around 2-3mpg better at speeds close to 80 vs 60-70 in my 7.

i have no idea what the turbo is doing, but i really dont care. the car gets better mileage and perfroms better, going faster, for me

[CX7nCali]

Thanks everyone for the information. I went to howstuffworks.com and learned some more about turbos. I too was misinformed about how it works, now I know.

I guess I'll have to learn to live with 17-18 mpg, unlike the salesperson who swore 22 mpg from all his previous buyers. Yeah right.

Thanks,
Robert

[dj dlux]

How is everyone dealing with the highly noticable turbo lag present in the 7? I love everything else about the car, and was hesitant to buy a turbo-4 (after having all VW VR6's over the last number of years), but the total package convinced me. Just can't help but wonder why a car like the Acura RDX, with a very similar powertrain, can be designed with very little lag, and the 7's is SO noticable? Also, i'm wondering if this is a problem that can be mitigated by Mazda via the ECU or something similar. I'm assuming it's not an easy, aftermarket-hardware installation type fix, so...
Just wondering...











Thanks everyone for the information. I went to howstuffworks.com and learned some more about turbos. I too was misinformed about how it works, now I know.

I guess I'll have to learn to live with 17-18 mpg, unlike the salesperson who swore 22 mpg from all his previous buyers. Yeah right.

Thanks,
Robert

[CX7andMiata]

How is everyone dealing with the highly noticable turbo lag present in the 7? I love everything else about the car, and was hesitant to buy a turbo-4 (after having all VW VR6's over the last number of years), but the total package convinced me. Just can't help but wonder why a car like the Acura RDX, with a very similar powertrain, can be designed with very little lag, and the 7's is SO noticable? Also, i'm wondering if this is a problem that can be mitigated by Mazda via the ECU or something similar. I'm assuming it's not an easy, aftermarket-hardware installation type fix, so...
Just wondering...

dj_dlux,

I just had my 7 into today for the hesitation problem between 50 and 70. They applied the PCM for the hesitation problem and while they had it they also applied the PCM for the turbo lag issue when you are below 2000 RPM. I can't remember the number of the TSB but after they applied the PCM the "lack of power" up to 2000 RPM and then a very noticable surge (when the turbo kicks in) between 2000-2500 has been reduced significantly (actually its pretty much gone).

I think somewhere else in the forum The Man has posted this TSB but I can't seem to find it at the moment. If I do find it later I will let you know. To answer your question though I think there is a TSB that could address your issue...

BTW, my 7 is running much better at highway speeds now after getting the PCM for the hesitation...

Hope that helps!

:)

[mikey1981]

How is everyone dealing with the highly noticable turbo lag present in the 7? I love everything else about the car, and was hesitant to buy a turbo-4 (after having all VW VR6's over the last number of years), but the total package convinced me. Just can't help but wonder why a car like the Acura RDX, with a very similar powertrain, can be designed with very little lag, and the 7's is SO noticable? Also, i'm wondering if this is a problem that can be mitigated by Mazda via the ECU or something similar. I'm assuming it's not an easy, aftermarket-hardware installation type fix, so...
Just wondering...

if u know how to work the gas pedal, its actually quite fun

the one thing i must say tho is that if YOU(not yourself inparticular) dont notice these problems in the car when driving, then its prob not a good idea to just go out and request these changes.

If it aint broke dont fix it. i actually like the burst of power, and to be honest i havent experienced a lag where i need to get my gearing changed. I like the way the car is now and ill most likely leave it unless somehow it gets worse.

[CXRabbit]

Problem you have is the some PCM updates will be done regardless of whether you ask for them or not.

[CX7nCali]

mine had the lag and surge in the beginning, then smoothed out on its own prior to having the flash

i was concerned about how and why it smoothed out on its own, but they had no answer

i personally feel it is transmission related, and/or torq conv

[CX7andMiata]

Problem you have is the some PCM updates will be done regardless of whether you ask for them or not.
Yep, that's what happened to me. I didn't ask for the "lack of power below 2000 rpm" PCM they just applied it because I did not have it...

[dmitrik4]

i haven't noticed any lag in my CX-7, but i also am coming out of a turbo Saab. ;)

as far as the acura goes, i'll say that the mazda at least feels quicker; maybe that's a byproduct of the different computer tuning between the two cars. either way, a turbo four is not going to have the same feel as something like a VR6, regardless of the tuning.

[dj dlux]

i haven't noticed any lag in my CX-7, but i also am coming out of a turbo Saab. ;)

as far as the acura goes, i'll say that the mazda at least feels quicker; maybe that's a byproduct of the different computer tuning between the two cars. either way, a turbo four is not going to have the same feel as something like a VR6, regardless of the tuning.


honestly, i wasn't expecting the same feel as a normally aspirated motor, but every one that i know that's driven the car, and the newest results from Consumer Reports, all backup the fact that the car does have a decent amount of turbo lag at low RPM's. It's similar to the effect that turbos had on cars in the later 80's, when the technology had trickled down to consumer levels. I just never really thought it would be that noticable in a 2007 model. Either way, i'm gload to hear that there are peeps out there who've had some changes, positive at that), made at the dealer to address the issue. Again, to me, it's really the only negative issue i have with the car overall.

[dmitrik4]

there's always going to be some turbo lag; that's the nature of the technology. even cars that hit full boost at pretty low rpm will still exhibit it, esp with an automatic transmission. the RDX has it. every turbo subaru has it. every turbo VW has it. every Saab has it. etc, etc.

some people are more accepting of it than others. and to be honest, the lag in the CX-7 is not anywhere close to most turbo cars of the 90s, let alone the 80s.