Is the 4th Gen Taco a hit or a miss?
- Thread starter Ragnar The Redneck
- Start date
Ragnar The Redneck
Well-Known Redneck
I had a 91 Supra Turbo with the 7M-GTE. Bought it with 125k miles, stock. Modded the bejeebus out of it, stock bottom end, about 375hp at the tire. Drove it another 100k miles with normal maintenance. I know many Mk4 Supra guys/gals with tuned 2JZ turbos putting out 550-600hp at the tire on stock bottom ends, drove them almost daily until their values blew past 100k, but now settled to around 80k.
Now, all of those engines had iron blocks, and these new engines are all aluminum. Aluminum castings can be very strong, but one thing that does concern me is if the decks are open or closed. A closed deck will hold tons of boost before blowing a head gasket or other similar failure, and are nearly bulletproof when kept stock. An open deck will not hold as much boost compared to a comparable closed deck engine, but are still fine for everyone except the most hardcore horsepower junkies. For example, a stock bottom end Toyota 2JZ, with a closed deck, can hold 800 to 1000hp, while the BMW N54 (their first turbo inline-6) with an open deck can handle 600hp on the stock bottom end.
Ragnar The Redneck
Well-Known Redneck
I would say to keep costs low. The 3.5L 2GR that served as Toyota's workhorse since 2006 produced on average 300hp, while the 3.0L 2JZ turbo in JDM trim produced about the same. The North American 2JZ turbos produced more power due to larger fuel injectors (550cc/min for N America, 440cc/min JDM), stainless steel turbos (JDM were ceramic) and different cams.
Normally aspirated engines also tend to have higher real world mpg ratings, but lower EPA ratings, while turbo engines are reverse.
Series6
Well-Known Member
The reason diesels seem better suited for turbos is because they are built stronger in the first place. Diesels are compression fired, no spark plugs. They run much higher compression ratios, consequently blocks, cranks etc must be capable. Then add the turbo.
For many years diesel trucks were normally aspirated which is why they needed very complicated transmissions. Two speed axles, 18 speeds, twin sticks etc. now we have 450-600 hp with flat torque curves at 1450-2250 lb/Ft.
Remember back in the late 80’s, early 90’s GM had major diesel failures in passenger cars? They basically took a gas engine block and added diesel heads and fuel handling, and were surprised when thinks blew up. Turbos or superchargers would have only made a bad idea, worse.
Yes the 2.5L Subaru engines were open deck, or semi-closed and many non-turbo engines had head gasket trouble. The earlier 2.2L engine did not, and I believe was closed deck. Ironically the 2.5L turbo engines tended not to have head gasket trouble, due to the better quality multi layer head gaskets. It would be interesting to know if the Toyota 2.7L is closed deck. It seems head gasket troubles are pretty rare.
Built stronger in the first place is key. Now it seems many modern diesel tractor trailer trucks are automatic. I heard one yesterday, sure sounded that way.
Yes back 30-35 years ago Oldsmobile had the 350 V8 diesel option, which was the gas block converted to diesel. I didn't do so well.
A buddy of mine had a 350 gm diesel olds. Believe it or not, it wasn't all that bad. He use to throw in a gallon of gas with every tankful during the cold winter months so the diesel oil wouldn't jell. We took his car a few times on 1k mile round snowmobile trips hauling a 2 place trailer.
That's interesting - putting gas in the tank to stop jelling. And that your buddy's seemed to be a pretty good one. Maybe the troubles were overblown.
Ragnar The Redneck
Well-Known Redneck
The 2.7L in the Gen 1 Taco, the 3RZ, was a closed deck design. The 2.7L in Gen 2 & 3 Tacos, the 2TR was an updated 3RZ basically, and is a closed deck design as well. Interestingly, the 1GR (and all other generations of GR engines) in the Tacos are an open deck design, so Toyota does have lots of experience with them.
I thought that may be the case given the 2.7L in all Gens seems to have a great reputation. Same with the 4.0L - but as you pointed out an open deck. Could that be why there tends to be more head gasket failures with that than the 2.7L?
Ragnar The Redneck
Well-Known Redneck
That could be possible about the 4.0L, I'm not as familiar with these engines. As a counter, though, the 7M in the Mk3 Supra had a reputation for blowing head gaskets, but that was from an improper torque sequence and not enough torque used on the bolts from the factory and early repairs from the dealership.
He bought the car used as his winter crasher, and would beat the piss out of it, yet it always ran good. He eventually sold it making back what he bought if for.
Series6
Well-Known Member
We’re running Automated Manuals. They have clutches and transmission modules and are programmed for economy. No clutch pedal. Push a buttons or twist a switch, truck does the rest. They’re programed to run between 62-68 mph and get 7-7.5 mpg. Empty or dead heading about 10+. 20 years ago, drivers hated them. Now it’s probably 90% of otr units. Some of them communicate with gps and “see” hills and they respond to maintain speed. We can even do over the air computer updates.
I've heard the term Automated Manuals, but wasn't sure what the difference was from a conventional automatic. Interesting how they're computer based now, and can see hills and shift accordingly. Amazing a transmission programming update can now be done over the air.
Series6
Well-Known Member
Engine, transmission, some settings. Saves the owner or operator from sitting around a dealership waiting to get in the shop.
Ragnar The Redneck
Well-Known Redneck
Hey, Series, is that a Sunbeam Tiger in your avatar? Looks like one.
I agree and only time will tell. Along those same lines, my concern is the MAX I-4 Hybrid that contains a NI-MH battery. If the article I read is accurate, this is not the ideal battery. Granted, Toyota's main focus is on producing 326hp/465 lb-ft with this setup, but this type of battery is known to deplete power when not use and it has a much shorter life span. my .02