2015 vs 2016 Compression ratio

Hey Everyone,

I was just looking at the specs on our engines and saw that the compression ratio is higher on the 2016 2tr-fe vs our

$90 2005-2015 Toyota Tacoma With 4L Right Petrol intake air snorkel kit high performance system compatible kit Replacement black Rotational Molding (2005-2015)

2005-2015 2tr.

Was wondering if anyone here knows what they changed? I thought our engine and most everything associated with it was just a takeover?

 

I think it's because the 3rd gens are an Atkinson cycle, though this is done with the tuning and not so much with the actual motor. Keep the intake valves open longer to achieve higher compression ratio, but ultimately less air/fuel. From the quick and dirty run down I got of an Atkinson cycle engine.

 

I thought the new 3.5 was the atkinson cycle, not the 2.7 I4?

 

It is, jtweezy just misunderstood which one you're talking about.

BTW it is interesting to see the rise of .6 for the compression yet same horsepower and torque figures.

 

Think that 9.6:1 is another one of Toyota infamous manual typos.... just as I'm sure the 4.0L was higher than 10:1.

 

I stand corrected. In 2015 they redesigned a few things...

• The introduction of variable intake and exhaust valve timing (previously intake only);
• A new ‘tumble port’ intake profile to improve swirl in the combustion chamber;
• A 10.2:1 compression ratio (previously 10.0:1);
• A new surface treatment for the cylinder walls;
• Teflon coating on the connecting rod bearings;
• Fitment of a lower-friction cam timing chain;
• Lighter valve gear, including roller rocker arms, retainers and valve springs; and,
• To reduce noise, insulators were fitted to the intake and exhaust manifolds.

 

Wow sr5vic, they changed quite a few things. Whats your source for the changes? Just curious. Weird the hp numbers were still the same to though.

 

They charged you more for the same thing and mileage suffered too

 

here's my source.... http://australiancar.reviews/2TR-FE-engine.php
its Australian, but motor comes from the same market obviously.

 

I believe the ratings did rise slightly in other markets to 164hp/181tq. Toyota probably didn't want to spend the cash to recertify the 2.7 in America. I imagine it's replacement is coming soon.

 

164 was the original horsepower claim in north america for MY2005.
http://www.edmunds.com/toyota/tacoma/2005/features-specs/

After that, it was reduced based on some changes with respect to the calculation, not due to any *actual* difference in the engine.

 

Oops! Thanks, I didn't read closely enough.

From what I've read, the new motor is tuned to behave like an Atkinson cycle motor, so I wouldn't be surprised if they carried over some of those tuning lessons to the 2.7L even if it's not a full blown Atkinson cycle, per-se.

 

So with an 11.8 to 1 compression ration on the 3.5, does it require premium gas? If not, any idea what kind of tricks they are playing to keep it from knocking on regular? With that high of a CR it would have needed Premium in the old days.

 

I'm not going to say that they actually *do* this consistently enough to make that possible, but we can easily come up with a theoretical mechanism by which they *could* based on their not-really-atkinson-cycle engine design that allows the intake valves to be held open through part of the compression stroke.

Basically, 11.8:1 compression ratio is based on the *full* volume of the cylinder, but if you hold the intake valves open through, lets say HALF of the compression stroke, then the volume you are compressing into the combustion chamber is really only HALF of the volume of the cylinder, so compression ratio drops to 5.9:1. Note that the "HALF" figure I'm presenting is purely made up to illustrate the point and does NOT actually come from the engine specifications.