Turbo: nobody home?

shadonoz

SkyActiv Member
Contributor
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State of Jefferson
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2017 CX-5 GT AWD+
[Cross-posted from CX-5]

Watched the SavageGeese CX-5T review last night, and one comment struck me as very worrisome. It was at the very end. He mentioned that once in awhile he'd punch it and not get the performance he was expecting, in other words reduced or no boost. He stated that's why he's not crazy about turbos in general, cause that often happens. I know exactly what he's talking about, because my old turbo would do that very rarely, but most memorably when passing on a 2 lane with a semi coming at me-- not good. I almost jammed my foot thru the floor.

My question is: have any of you CX-9 turbo owners experienced this at all?
 
I've never had it happen to me, but I only have 17k kms on mine. I haven't watched the review yet - going to do it on my lunch break - but I'm guessing he doesn't go into any more detail about the issue.
 
Like every other manufacturer, Mazda does a lot of research into how to minimize turbo lag. Mazda's preferred solution is to use as short an exhaust manifold as possible (join the club...) and to use a dual feed to the turbo. Up to 1,600 rpm only a small passage is open between the exhaust manifold and the turbo, meaning that even with a low volume of exhaust gases the turbo will spin up quickly. At 1,600 rpm a valve opens, opening up a larger passage that allows more gases to flow to the turbo, thus spinning it up even more. I have found this works quite well as I don't recall ever noticing anything other than the most minor turbo lag.
 
To be clear, this isn't about lag at all. SG was singing the praises of the 2.5T in that respect. I thought he was talking about lack of boost when it's expected.
 
I have the engine both in the CX-9 and 6 and haven't noticed such a thing. I too watched that review last night.

SG has a tendency to exaggerate things so who knows if it was really a glaring issue or just slight lag.
 
The Sport Mode switch is a big help to get more scoot when needed.

Mazda designed the 2.5T to provide more boost at lower rpms than most turbochargers. That gives up some boost at top end, but that early boost is where most drivers need it. The exhaust gas valving noted above is part of that. The low rpm exhaust gas will have extra velocity into the turbine to get things off to a quicker start.

A gas turbine is a heat engine. The hot gases expand in the nozzles and create the jet action that spins the turbine shaft. Gases cool as they expand. If the low volume (low rpm) exhaust gas is allowed to expand before it gets to the nozzles, it is cooler, and less power is developed in the turbine. This valve design limits that expansion & cooling when running at low levels.
http://www.turbos.bwauto.com/products/turbochargerTurbine.aspx
 
Savagegeese is way too hung up on the infotainment systems in these cars a it is really his main criticism of the CX-5 and all current Mazda's. He hates the HUD so
much and that's one of the reasons I bought the CX-9. Major safety feature in my opinion. With the addition of Apple Car Play and Android Auto the infotainment in this car is fine and as useful to me as any of the others I've had/tried. The WAZE app works great and it's an easy to use system with the joystick and volume knob set up the way they are. There's a reason Audi and BMW have been using similar set ups for years now. It works. I wouldn't want to have to reach my short arms over to the touch screen to make changes especially on the fly. Not safe. My friend has an MDX and does not like that he has to activate the touch screen and use finger prompts for the HVAC system and just about everything else. No thanks.



As far as the OP's question about turbo lag goes I do feel some lag at times coming from a dead stop but it's hard to tell if it's the turbo or just the way the accelerator is programmed. The feeling and amount of acceleration does vary a bit with this car relative to pedal input. Sometimes it feels like it has to think for a second before it responds and then there is slight power followed by considerably more power, if that makes sense. I have yet to have to CX-9 on a two lane highway where I want to pass a semi-or camper at 65 mph. I do a lot of those types of miles and that's where I hope there is enough power. That is much more important to me than how it pulls away from a stop sign. I understand how/why Mazda set up the turbo powertrain this way. Useable power where 80% of most people who drive this type of car are going to need it. I give them credit for being innovative and doing something different with a turbo motor to make it well... less like a turbo. Would this car be even better if you dropped an old school N/A V6 in it like the one in the Highlander? Maybe it would, but you might lose a few MPG's and it would add some weight. So far I like it the way it is. Time will tell if this is a great long term motor. I'd like to hear some reports from CX-9 owners that have 70-80k on the clock.nd
 
I have the same suspicions as PTguy that high rpm is where the dude is "not feeling the boost" when in fact its just how the engine works.

300 foot pounds, 20mpg, high rpm punch. Pick two.
 
Any update from Mr Goose? It was below 20 again this morning and I could definitely notice the reduced power.

It was in the 40s earlier in the week and it was amazing to have the all the power the car should have.
 
I have a 2017 CX-9 and I notice the lack of boost in a very specific scenario. Example, if you are coming up on a red light and slowing down, and the light changes, the switch from deceleration to acceleration has a very noticeable lag, almost like there is no acceleration for a very short amount of time. Eventually it rights itself and you get slammed back into the seat as the the acceleration matches the boost. I've noticed this on a couple of turbo engines, but not so much on NA or Supercharged vehicles. Not sure if it is physical (turbo winding down and then has to suddenly increate) or electronic, but I do feel it.

Overall not a deal breaker, and I just need to be careful in those situations.
 
I have 15k miles on my cx9 and never experienced this at all.
It is true though that turbo are more efficient in cold weather, when in an extreme summer temperatures , turbo engines will loose a little performance but barely noticeable. I don't see any downsides on modern turbo engines. Specially when u go to high altitude mountain roads where turbo engines rule.
 
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