Turbo on 72mph, long distance, problems??

[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]

But the REAL question a lot of us have is...

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.