I believe that they can get away with the higher compression due to their VVTi (Variable Valve Timing w/ intelligence)...aside from being able to increase valve lift, it also bleeds off pressure. Not to mention, the hemispherical combustion chambers are very efficient...yota's have been using em for years

 

So their static CR is higher, but they aren't getting as high of a dynamic CR due to bleed off? If I'm understanding you correctly, I am hearing that if you set up GM valving and Yota valving on the same engine (same static compression ratio) the dynamic on the Yota would be lower than the GM, allowing for lower octane, right? So with variable timing, the static ratio is a bit misleading for an apples to apples comparison?

 

That's pretty much the way it was explained to me if I was told correctly. I actually asked a trainer at Toyota Motor Sales how the Celica was getting away with 11.?:1 on 91 octane (this was a few years ago), and he contributed it to the VVTi system. At the time when Toyota started using VVTi, they also stopped using EGR, as the VVTi was able to compensate and control cylinder temps and pressures, rendering the EGR system no longer necessary. (by this point, Toyota wasn't really using EGR to recycle exhaust gasses for "cleaner" tailpipe emissions, as the engines were/are efficient enough on their own not to need it. Toyota was just using EGR to cool cylinder temps to reduce NOx emissions)

 

man gm get you head out of you aaa and just let us order rc trucks with what ever motor you have ls7 would befine.

 

and a ******* 6 speed trans !!

 

Yeah i think that eventually i am going to do a TRD swap in my truck, lol

 

right, used to be they were swappin chevy engines into toyotas

 

The Chevy truck needs a couple more gears in the transmission. I'm not sure why GM hasn't built a heavy duty 6-speed automatic!

 

Trust me, its true. I'm not a tuning guru, so I don't know all the terms and ins and outs, but when Wheatley tuned my 4.8, there was a definite 4 second lapse after flooring it, before the ECM would fuel the system and then it would hammer down.

We picked up a 6 tenths gain 0-60 just with an 87 octane tune and removing 50% torque management. I should be going back soon to have him update it to a 93 tune and about 25% more TQM out of it.

Other noticable thing I see, is look at the torque numbers--most noticably, the where it peaks out on the powerband, the silverado peaks out with less torque at 700 rpms higher than the tundra and 900 rpms higher than the titan.

 

I have a gut feeling the 5.3L is faster than the 6.0L in the 2007 chevy trucks I think my 2005 GMC 5.3L running on E85 ethinal 105 octain or possibly on gas will beat a new tundra. The 6.0s seem a lil more slugish off the line than a 5.3l. Im dying to race a tundra, titan even if I lose.