williemon

Bumpin Yota, Ive just been down your way to Ft. Meyers. Yall dont HAVE any hills.

I think the 3.0L is not powerful due to the head design and valve timing. You can get them to flow more air by modding the heads and exhaust and intake, so this helps HP, but I think to get the torque up there requires a different camshaft design. One of my cars (RIP) had a chevy 305 in it. About 140 to 150 HP at around 4500 RPM, but something like 220 to 240 lbs/ft of torque at 2400 RPM. Yes, it could make you feel pinned to the seat, but only up to 2400 rpm. Past that and it dogged out. It had a head and cam setup to max torque at the low rpms for a fuel effecient grocery getter. Now same engine, but designed for higher HP and a higher operating rpm was used in some Monte Carlos SS and some Camaros. Something like 190 HP but much less torque.
I say, give the 3.0L a better valvetrain and the performance can be there. Of course, a little more displacement wont hurt either.

oly884

Ok, thats good to know. I knew that the heads arn't the best part of these engines.

gwhayduke

My personal opinion is that the problem is mainly due to intake and exhaust problems. The intake takes air in from behind the headlight (obstruction #1), air enters the airbox where the opening of the air meter is pretty small (obstruction #2), the air flow then passes through a maze (obstruction #4) on it's way to the plenum. On the exhaust side, the drivers right bank exhausts and crosses over to the left bank and enters upstream against the flow of the exhaust trying to exit the manifold. It then enters a pipe that is smaller than is optimum and then the Toy muffler is restrictive as well.

The restriction that most modifiers haven't either noticed or figured out what to do with is the restrictive opening of the air flow meter.

I'm still trying to figure that one out.

oly884

BTW: Williemon, how much HP did you get from your head work?

oly884

SAME HERE!!! I've looked through many different toyotas and havn't found any that will flow more air. I'd have to be a new unit, but of course that'd be cheap.

williemon

Oly, the head port and polish is rated by DOA to provide about 33 HP and the addition of the reground cams will provide maybe 8 HP more. So, around 40 HP more. The torque gains were not rated as being very much more than stock. Maybe 20 lb/ft more, but coming in a little sooner. This way, you feel the power come on at around 2200 or so, but you get a big kick when you hit 3000, and it seems to pull on up to 5000. I had to have a full 2.5" free flow exhaust to make the end results be as DOA designed. I have not modded the intake yet. Problem though is that I do like the added HP, I also wanted more torque boost down at 1500 and 2000 rpm which could not be had. I think this is due to that you have to modify the existing cam, and cant replace it with a cam that is really optimized for more low end torque. I may be wrong, but I like to think im right.

Praufet

Could you not do the ISR modw/ a cone filter and just stick a later model air flow meter on to the new intake pipe between the conefilter and the pipe. Personally it seems to me that the ISR + CONEFILTER = K&N FIPK.

livelarg

My 88' 3.0 has 250,000 miles on it, and it still runs perfect. And I have seen many other posts of guys with high milage 3.0's that are still running well.
I think that there is a trade-off with engines. Power or longevity. The more you soup up with power, the more sensitive the engine becomes. And I think Toyota wanted an engine that would last forever without much problems. This is especially important for people wanting to go in the backwoods. So do you want power or dependability?
Of course, Toyota prolly could have put a bit more power without hurting the engine. But we are also talking about and engine that was designed almost 20 years ago.
I also agree with the SOHC vs. DOHC discussion. Torque does come on earlier with the SOHC engine. But since I am on the road more than off-road, and it is my daily driver. I am interested in the DOHC mod if it can work out. I wonder if DOA has some opinion on it?

gwhayduke

The restrictive opening I'm talking about is the entry into the air-flow meter. Take the top off your air filter. Now tilt it back as far as it allows and look at the opening into the air flow meter. Unless I'm looking at it wrong, it looks like it's a much smaller cross section than the pipe leading from the AFM to the plenum. It seems to me that most of the mods are focused around getting more air into the air box. But none have looked at gettng more through the AFM.

Lucky

From my memories of engine tuning, 4 Valves per Cylinder doesn't always make a great deal of difference (and actually can make a negative difference) unless you are running high RPM. Larger Valves on a 2 valve design at lower rpm can actually be better and can often have a greater impact on Torque than more valves.

Probably more at stake here is the combustion chamber design or shape not creating the correct burn characteristics.

A decent tuner could probably mod the shape of the cimbustion chambers, port the valves, maybe rough up or smooth out the combustion chamber itself to create a different burn.

Quite often increasing the air available by supercharging, turbocharging or intercooling the engine can help but often the cimbustion chamber design is a limiting factor that makes the engine incapable of using that extra air drawn in.

With the DOHC heads you will probably find a considerable difference in combustion chamber shape, you may even find that the piston crow shape is different on the newer engine so just doing a straight swap may not be so easy as compression ration, burn characteristic etc maybe badly compromised.

I guess all engine design is a list of compromises and if you build an engine that lasts for 300K then I guess there will be a few compromises on the power, efficiency etc.

Remember some seriously powerful drag engines have been built out of motors that are basically truck engines, SOHC or even In block cam types but by concentrating on what the engine does with what it has to play with rather than worrying about the technology on board, they can come up with huge power outputs. Mind you they only last for seconds and you wouldn't want to drive one on the road.

Now the guy at Toyota who designed the 2LTE (2.4 Turbo Diesel) ought to have been taken out and shot - there are so many issues of head cracks after 50 - 60K miles that the guy must have been an idiot.

Cheers

ohio

Don't know jack about my own truck, but thought I'd chime in on SOHC vs. DOHC. The high rpm and low rpm performance is dependent mainly on cam profile, NOT the number of camshafts/valves. It's just that to get the most out of a high RPM cam profile, you should run DOH cams.

Basically DOHC are always more optimal than SOHC... however at low RPMs for the same cam profile and cam timing, the advantage is so small (because you're really not pulling in THAT much air relative to cyclinder diamter) as to be a waste of money. At high RPMs it becomes much more significant.

High RPMs require different cam profile to optimize performance given the inertia and viscosity of air (basically longer lift to allow air to pull itself into the cyclinder and compress a bit before closing off). This is true for SOH or DOH cams, but DOH cams do it better as they allow even more air to get in. You optimize for high RPM combustion, you give up low end performance, because the longer lift allows some air to escape back out.

So the result is companies only shell out for DOHC engines when they go to high RPMS. As a result of designing for high RPMS they lose the low end. Not the fault of DOHC, just the design of that engine.

With variable valve lift (VTEC, VVTil) engines now have cam profiles for BOTH high and low end, but because trucks pretty much stay in the low end there's no reason to use 'em.

Without knowing why the 3.0 has such bad mileage it's hard to say if the head mod will help. Most likely you'll end up with a touch more horsepower and torque up in the revs, and the same crappy mileage you got before. I also don't know how higher lift cams are going to mix with the heavy (read: low RPM and torquey) flywheel in the 2nd gen.

KING

$500??

I don't hate it that much.

Praufet

Talked to DOA. The head bolt pattern is different from the -E to the -FE. Personally I was mainly seeking converting the E to the FE to increase gas mileage. The power was just a bonus I remember once there was this article in hot rod mag about a year or two ago about cars that pulled 12sec 1/4 and got 20 mpg, anyone have this article. Interested in seeing how that was pulled off. Anyways off to find another solution to the ever elusive mpg answer.

Lucky

Interesting point that about getting decent power and decent mileage.

I guess there is no real rule that says a high power lump should be inefficient. In fact really the better power you are getting the more efficient the engine.MPG is also determined by the shape of the car and the 4runner is about as aerodynamic as the White House therfore it doesn't do the MPG any favours, you are pushing a square box through air that doesn't like it.

Also reducing friction and losses in the ebgine can help, get the engine blueprinted, balanced, used a decent oil, make sure the bores and rings are spot on and also make sure that the bearbox, transfer case, diffs have decent clean oil. Tyres are at the right pressure, have a good tread pattern.

The problem with SUVs is they aren't aerodynamic, induce a lot of drag and have high friction losses due to extra diffs, bigger tyres etc etc.

I used to have a Camaro with a 283 cube engine from 1960's Corvette. Used to top out at 135mph (my fear limit not the car's), 0-60mph in 6.6 seconds and returned 23mpg so power doesn't neccessarily mean bad gas mileage.

And while everyone thinks that Diesels are more economical, in the UK we are lucky hitting mid 20s MPG with the 2.4TD engine. The 3.0TD engine actually returns better gas mileage and has considerably more power.

Cheers

lakings17

I agree that an automatic trans. is slow.I have an "88" 3vz 4X4 with a 5 speed and this truck flies on and off road and pulls trailers up hills with ease.I had the engine rebuilt at 295k miles and spent $2000 going through it.The truck looks and runs like new and for the money is an excellent deal.I think the big problem with 4 runners is they are almost all automatic transmissions.Anyone else agree?

Paul H.

I could deal with the low gas milage if the gas tank wasn't so small. Toyota did a lousy job in not putting a bigger gas tank on such a large vehicle.

amusement

The gas tank is too small.

I purchased and installed an aux gas tank to offset the stock one.
16+15=31 gallons at a cost of 425 USD. I can drive from 530 - 620 miles when the truck is filled.

coloradodragon

275,000 miles and running strong.(knock on wood)-- I get like 18 mph at over 6000 ft of altitude. Guess I got lucky with my beast.