After completing N/A mods - low boost OK?

[Nlghtmare]

So we've all been talking about it for years, turbo on a cvt 2.5. It's been done before on other cars, and some cars come stock boosted mated to a CVT transmission. Facts are facts. About one year ago, there was a guy on the forum who claimed he had a turbo equipped on his 2008-2009 Altima coupe. He provided pictures for us to show the NICO fam that everything was quite legitimate. As theorized though, his turbo and transmission did not hold up. Wait a second though, why did it fail? My theory, as well as many other who speculated on that thread was the n20 he added. If he did have about 7lbs? of boost plus the spray, he would probably be nearing 290-300 horsepower, respectively. It's very safe to assume that his own greed for speed on an economy car without taking the necessary precautions led to the ultimate let down of his vehicle.

Now then, jump to present time, 2011. Let's say an owner of an Altima Coupe with the QR25DE and CVT transmission did all the standard air inductive modifications and all other N/A modifications available for the car to date (intake, exhaust, pulley, spacer, tune/"chip") and now wants to experience low boost for the EXTRA gain in HP/TORQUE. Do you (the mature car enthusiast) think it would be possible without damaging the transmission as fast as the last CVT owner did? I'm not asking would you do it, and I'm not looking for a "well why would you do that," or "what a waste of money" remark, I'm simply asking through regular research and experience, if you think it's possible. Keep in mind, low boost usually means 3-5lbs, usually leaning towards 3.5 on stock vehicles, and if it were to be done on a 2.5, I would expect the owner to do something somewhat similar.

Before people get their panties in a bunch screaming their innards out exclaiming that the idea is a waste of time and money, keep in mind, it might not be. I can elaborate. I feel a car that sounds good, looks good, and that's has a good fuel economy isn't a bad thing. I don't feel the need or urge to trade in my car for anything else, as the miles on my car are still generally low. Low boost also means similar gas milage. "Oh but Nlghtmare, modifications to your car will decrease FE!" You can say that, but I can say from experience, it's quite the opposite. The mileage will stay the same and often times improve.

I'll give my opinion on the matter first then.
I don't think low boost will ultimately result in failure of the engine and/or transmission of a 2008 altima coupe 2.5 with a cvt transmission. I also think that gas mileage will not decrease or increase for that matter, but it will remain at a neutral number. It's possible that pounding on the car with boost and other mods may increase the odds of failure of the car all together, but assuming we're not those type of drivers, the car shouldn't cease to run.

Now for your mature thoughts.

(Note: I'm looking for some conversation before my class starts. I am slightly playing devils advocate here. I have no intention of boosting my car RIGHT NOW, but may regain interest in the distant future.)

[rcboy514]

sounds like you have already made up your mind lol

If my instinct is right in who you were referring to, then I'm pretty sure he had the 3.5 cvt, it's my understanding that the cvt in the 2.5 and 3.5 is not the same. I think the 2.5 cvt wouldn't stand up to the abuse the 3.5 cvt could, but then again you aren't dealing with the same amount of HP. What kind of gains would one expect from 3-5lbs of boost? You might want to talk to Scott (QR25DE), his 2.5 is boosted and I would guess the installation is identical, he could probably give you an idea of the gains to expect.

You mileage should stay the same under normal driving, but lets be honest, you will be "testing" out the turbo a lot lol

[RicerX]

Check this thread if you haven't already:
should-i-turbo-poll-t515160.html?hilit= ... t&start=40

It is your money and we love seeing guys rock out the mods here, but I'll break down my mature opinion for you.

Two answers (the first addresses your actual question) - yes it's possible to not have the transmission go out as quickly as the next man with lower boost. However, it all comes down to driving habits.

Answer two (addresses everything else you talked about which doesn't necessarily relate to your question) - It's not at all worth it. I'll even leave the obvious CVT argument out of my assessment (which, in itself, is enough to defeat the idea).

1) 3 psi of boost on a 2.5L motor will not give you enough of a return to justify the costs of putting in the proper wrench time and tune to make it run efficiently enough to be deemed a daily driver.

2) To further contribute to the FE stuff you bring up, most turbo kits swap out fuel injectors. To my knowledge, the turbo kits available for the 2.5 and 3.5 altimas do swap out injectors. This is going to impact your fuel economy regardless of driving habits, as injectors are upgraded in order to optimized the air fuel mixture that is required in a boost environment. Not saying you're going to have an enormous drop, but you'll see one. Yes, there are mods like opening up intakes and exhausts that can increase fuel economy, but when you start messing with the fuel system, things change.

3) Any other mods that you have on your car that are not suspension related are likely to be moot. Your intake and tune that you have listed as pre-existing mods will no longer work with the setup. With low boost (around 3 psi as you say), a bigger exhaust will not yield much, if any, gains whatsoever. I'd be willing to estimate that a turbo with that low boost would not yield much more added power than a 2.5 with catless header, pulley, intake, full exhaust(catless) and a full tune to adjust for the new airflow. If it does add more power, it likely will only be enough of difference discernible only on paper.

Taking number 3 into account alone will lead to upping the boost to not feel like you wasted $5K (at least that's what I would want to do if I were in this situation )

[DReed86]

1) 3 psi of boost on a 2.5L motor will not give you enough of a return to justify the costs of putting in the proper wrench time and tune to make it run efficiently enough to be deemed a daily driver.

First off I say do it but keep in mind you will not feel very much of a difference...

you will be spending about $8K no matter how you cut it.

and at some point you will blow your engine.

So that being said do it!!!! lol In all reality if you want a turbo get a manual or another car.

[Diesel187]

I’ve looked into this quite a bit over the years. But the limiting factor has always come down to the CVT transmission. There’s only so much torque that it can handle. If too much torque is applied, it will blow. But, in theory, if you can boost the engine, while staying within the specified torque band, it should be fine.

Just for fun, or food for thought…

Jatco is the CVT manufacturer for Nissan, Jeep, Suzuki, and Mitsubishi, to name a few.

http://www.jatco.co.jp/ENGLISH/PRODUCTS/index.html

From the Jatco website, the 2.5 transmission (JF011E) is rated at 250nM or 184 ft-lbs of torque. The 3.5 transmission (JF010E) is rated at 350nM or 258 ft-lbs of torque. Nissan’s site lists both cars as 180 ft-lbs and 258 ft-lbs respectively. That being said, it seems like the transmission is already at its limits. There isn’t much room for growth. Adding a turbo would certainly destroy it.

Would a low boost be safe to use? I would not bet on it. Maybe it will work for a short time. But it won’t be significant. Eventually it would break down for the simple reason that the CVT was never designed for that.

Like DReed says, “if you want a turbo get a manual or another car”.

[QR25DE]

Yep get manual or go home honestly.

I mean it would last for a bit, but the CVT will be the first to die. Maybe less on 3psi but then at 3psi what's the point? Even so it depends on what turbo you have. PSI ratings do not really mean much unless you know all the other factors.

You WILL have to swap injectors. More air = more fuel = more power. If not enough fuel, engine go KABOOM!

Your best bet if you want to do it *my* way (which I dont recommend unless you are very knowledgeable and mechanically inclined to fix a lot of s*** when it breaks) would be to go the eBay turbo route. Get a generic ebay turbo kit for a grand for a Sentra Spec V and cut/mod everything to fit.

But, CVT = fail.

[masterbeatty]

The other question is.... what is the difference between our CVT and the newer juke cvt with turbo? how did they make that happen? mechanically. if we could figure out that then theoretically we could have a reliable transmission with turbo. J S'n. But if it requieres a swap then swapping to a MT would be a better route. Or you could go the route of buying a car with a turbo already in it and call it good.

[beeristasty]

The other question is.... what is the difference between our CVT and the newer juke cvt with turbo? how did they make that happen? mechanically. if we could figure out that then theoretically we could have a reliable transmission with turbo. J S'n. But if it requieres a swap then swapping to a MT would be a better route. Or you could go the route of buying a car with a turbo already in it and call it good.

Look at the numbers. The juke's displacement plus turbo barely equals more hp than the 2.5 while essentially matching the torque. Even if there is a difference between it and the 2.5 cvts, it is likely minimal.

Altima
QR25DE – 2.5-liter DOHC 16-valve 4-cylinder
Horsepower – 175 hp @ 5,600 rpm [*]
Torque – 180 lb-ft @ 3,900 rpm [*]
Emissions – Tier 2, Bin 5 (LEV2-SULEV in CA)

VQ35DE – 3.5-liter DOHC 24-valve V6
Horsepower – 270 hp @ 6,000 rpm
Torque – 258 lb-ft @ 4,400 rpm
----------------------------------------------------------------------
Juke
MR16DDT – 1.6-liter Direct Injection Gasoline (DIG™) DOHC 16-valve turbocharged 4-cylinder engine
Horsepower – 188 hp @ 5,600 rpm
Torque – 177 lb-ft @ 2,000 – 5,200 rpm

[lavon_andy]

just get a z and boost that :P

personally, I love my car

It's slow, gets great mileage, it's super comfortable inside, it's pretty, it's slow, and it has enough of a backseat to umm...

I know it's not a race car however, but I don't need a race car (maybe want but thats a different story; GTR please?)

turbo = cvt pop unfortunately; just based on past examples

and even if it doesn't pop your cvt immediately, it will shorten the life of it

[coupecrazy1232]

just get a z and boost that :P

this guy knows whats up!!!

[big_rig]

FYI i have 2.5 n/a cvt and i think the transmission is already going. no boost, just a lead foot and some hills are enough to kill your cvt, i took the car in for transmission fluid swap and the dealership said that i didn't need a change. to sum it all up, my cvt screams like a supercharger every time i take it off flat ground.

[wade001]

FYI i have 2.5 n/a cvt and i think the transmission is already going. no boost, just a lead foot and some hills are enough to kill your cvt, i took the car in for transmission fluid swap and the dealership said that i didn't need a change. to sum it all up, my cvt screams like a supercharger every time i take it off flat ground.

If it's under warranty take it to them and tell them to fix it. the CVT is by far the weakest link for the AC

[Ranga14]

I'd advise against it. At 3psi, it's not really worth it.