1FZ - Power above 2500 RPM (2 Viewers)

[RyRoRyan]

So I dont know if this is just normal or if something is actually not right. I have only had this for a few months and I feel it is REALLY, like REALLY weak. First off, let me give you what I am working with so you can get an idea of where it SHOULD be. Rig is lift by 850J and 863's with 30mm spacers as well. Running 37" tires, but with Nitro 5.29 gears so I am about 10% OVER geared from stock. I know I have alot of weight in tire to turn, but still, I dont think it will kill me as much as it is. I can craw all day and feel I have some good torque in the low RPM range, but it feels like after 2500 RPM or so, the thing is not generating any more power...almost like just a constant flat HP curve at 2500 to 4500, which I know is not right. The torque curve on this is almost flat up to near 4500 so I should see the HP gain as the RPM is gained. On flat land, I can get the thing to cruise at 70-75 MPH (80ish MPH on the speedo due to gears) and the RPM's are about 3000 or so, but I have the pedal almost buried to do that. Getting home and climbing some hills to do it, it will slow down to about 60 and stay there...the trans will try going from 4th to 3rd, getting the RPM's up past 4000, but it really doesnt change acceleration or even holding the speed doing that. It is breathing well, it has the EMS stainless exhaust on it and I have changed the air cleaner out last month. I have not double checked this yet, but it has been told to me that the timing was moved to 7 BTDC (from the stock 3). I have ran it on 91 octane instead of 88 to see if maybe it was knocking that was causing it, but no difference. I am not sure if the 97's ECM will show me knock count on my obd II but I will check that when I get home. Does anyone have any thoughts of what else it could be?

 

[ZackR]

Doesn't sound too out of the ordinary for big tires, warm weather and high elevation (even with the regear). I think there's a gap between what people expect these old beasts to do in relation to a new vehicle at highway speed and what they can actually do.

If you can find another cruiser guy/girl who is local they could take it for a drive and let you know. My old cruiser is happiest at 65/70mph with the cruise control set on the interstate or 55/60 on the secondary highways. When I push it beyond that I can tell its working quite a bit harder.

 

[quasi]

fuel filter plugging up?
TPS faulty?

 

[RyRoRyan]

So I used my obd tool and watched the advancement as I drove. Realize I am seeing ECU advancement, you have to add the static to it. I THINK static is at 7 BTDC but I have to go get a timing gun to confirm this. Anyway, at idle, I am seeing it sit anywhere from 4 to 10 degrees. If I get on the pedal at about 10 percent or less, then the advancement goes up to 20 or so and will sit around 25 to 30 if I am just cruising at around 2400 RPM. If I get on the throttle any more than 10 percent, I see it what appears to retard back to around 13 to 15 degree and it will stay like that the entire RPM range as long as the pedal is down more than 10 percent. The TPS is fine as I can read that on the obd as well and I cant watch it see the entire range of the pedal. I am at 7000 feet but running 91 octane, could I really be having knock and retarding happen? I recall somewhere seeing where I thought someone knew the expected spark advance, but I cant find that anywhere. Can anyone tell me if what I am seeing is normal, or am I actually running a retarded engine due to knock or some other event?

 

[Kaninja]

Seems normal to me. These are big, low compression engines that are designed to run for hundreds of thousands of miles with little maintenance. The cranks are big, the rods are big and heavy, the piston wrist pins are ridiculously massive. It really feels like mine has the same power from 1,200 through 4,500 RPM.....it is very flat. The cams are very very mild as well.

I like my tractor motor.

 

[SmokingRocks]

sounds about normal but here are the things I did which yeilded the most "butt dyno" smiles.

1) Sent my injectors off for a full service, rebuild and flow match
2) replaced my fuel filter
3) bypassed my vsv

I'd say that 1&2 were hallmark moments and I really felt a gain. 3 was a result of a clogged charcoal canister that I got tired of dicking with, and since the fuel tank was under less pressure (vented to atmosphere) I convinced myself that the fuel pump didn't have to work as hard.

 

[Rifleman]

You've got a 6000 pound truck, powered by a N/A fuel injected 275 cubic inch in line 6 cylinder, it's never going to be quick, or fast, that's why it's called a LAND CRUISER.

 

[RyRoRyan]

I guess the question I am trying to find out is if anyone knows what the real timing map is? While it could just be normal as everyone says, I really want to try to eliminate the possibility of it retarding back. I only am thinking this is possible because of the numbers I am seeing on my obd. I mean, at little load and 2200 RPM I see 30 or so degrees of timing. I add ANY extra load to it and that number drops to 15 degrees...I mean I know that it is supposed to back it off a little bit the more load you put on it, but come on...15 degrees?!?!? Thats just a few degrees from idle. At that timing, you can almost assume that in high RPM, the fuel is still burning after expansion. This would give CRAPPY gas mileage and NO power at high RPM. Pretty much exactly what I am seeing. I mean I know this is a conservative tuned engine, but what I am experiencing is almost not usable in high RPM.

 

[RyRoRyan]

You've got a 6000 pound truck, powered by a N/A fuel injected 275 cubic inch in line 6 cylinder, it's never going to be quick, or fast, that's why it's called a LAND CRUISER.

I am not expecting quick or fast. All I expect is for it to have power and gaining power as RPMs increase. I dont see this at all. I have low end torque just fine, it all seems to disappear between 2500 and 3000 RPM. We are talking like trying to come up a hill right near my house. Its MAYBE a 3%-4% grade, starting from a stop near the bottom, I can get out of 1st but it will not gain speed in 2nd gear going up it. We are talking like 30-40 MPH tops. If I already have the speed, I can kinda keep it as I was saying earlier...like I can hold between 60 and 65 or so going up a different hill which is also about 3% or so but I would not be able to get up to that speed if I did not have that velocity already going into it.

I see some of yall have expedition trailers that you haul behind your rigs...I know right now that I would not even attempt this. I would be at 45 MPH max on flat land.

 

[Twinair]

At 7000' elevation your truck is suffocating. FI is the way to go and is the way I am going as soon as someone develops a turbo kit (in the works according to this forum). I don't notice a huge increase in power at higher RPM and I'm close to sea level. I would say my power is adequate and nothing more for 32" tires 1-1/2" lift on stock gears. Add any weight from passengers, gear, or a trailer and its underpowered. Turbo that pig!

 

[downshift13]

I'm not a master at this, but if you look at the torque curve of the 1FZ motor. The torque peaks at around 3000 rpm, maybe that is why you've not feeling that "uumph" on higher rpms. It just the way the motor is designed maybe? Plus, the cruisers are really heavy.

 

[RyRoRyan]

View attachment 1488036

I'm not a master at this, but if you look at the torque curve of the 1FZ motor. The torque peaks at around 3000 rpm, maybe that is why you've not feeling that "uumph" on higher rpms. It just the way the motor is designed maybe? Plus, the cruisers are really heavy.

I would fight this argument and say that the torque curve is pretty flat from 2000 to 4000 RPM. Note that HP keeps gaining all the way up to just past 4000 as well. This is because torque and HP ARE related (HP = torque x RPM / 5252). As long as the engine is creating constant torque, it should be creating more and more power (HP) as its RPM increase. I am not seeing this...I am feeling almost a flat HP response after 2500-3000 RPM, which tells me the torque curve for me is falling there and the power output is not increasing with the RPMs.

 

[Rivman1243]

Do you have a brake dragging?

 

[JeepinPete]

I'm running 37's, stock gearing, much closer to sea level. The rate the engine rpm's climb as the truck accelerates is very linear. 4k rpm seems like the fall off point, and going beyond is only useful to keep the rpms above a certain level when you shift into the next higher gear.

 

[DylanICON]

I feel the same way and I am at close to sea level, 35's/4.88. over revving it doesn't really pull any harder, just get you to the next gear. I was going to see if my cats were clogged as I have had that issue on other vehicles where it falls over at higher RPM. other than maybe cats(and I don't think it high likelihood, just want to check) I believe mine is running correctly and I have also added a couple degrees of timing. when I have had mine at higher elevation it is pretty pathetic. did Black Bear pass in CO at 13,000 and 1st low range would barely get it over some obstacles.

 

[scottryana]

Yep, it was Black Bear and Imogene passes for me that actually made me think even in low range I might stall with lack of power.

I feel the same way and I am at close to sea level, 35's/4.88. over revving it doesn't really pull any harder, just get you to the next gear. I was going to see if my cats were clogged as I have had that issue on other vehicles where it falls over at higher RPM. other than maybe cats(and I don't think it high likelihood, just want to check) I believe mine is running correctly and I have also added a couple degrees of timing. when I have had mine at higher elevation it is pretty pathetic. did Black Bear pass in CO at 13,000 and 1st low range would barely get it over some obstacles.

 

[JeepinPete]

My cats have less than 10k on them. Didn't make any difference when they were swapped, I just couldn't salvage the originals when the cat pipe broke.

 

[Mandrake]

How many miles are on it, and have the cats been replaced? You may have a plugged cat. I've experienced this once on a '93 Accord, and it was like you describe- it ran fine up to a certain rpm... maybe 2500-3000 rpm or so... then it just hit a wall and would not Rev any higher regardless of speed or gear. If I recall, it wouldn't even rev past 5k in neutral.

Anyway, something to consider.

 

[Kaninja]

Plugged cats the engine would run like garbage. Only time I ever had a plugged cat was when Toyota burned my cat to death on a 3VZE. It was like someone put a cork on it. Sounds like OP has a properly running engine.

 

[RyRoRyan]

How many miles are on it, and have the cats been replaced? You may have a plugged cat. I've experienced this once on a '93 Accord, and it was like you describe- it ran fine up to a certain rpm... maybe 2500-3000 rpm or so... then it just hit a wall and would not Rev any higher regardless of speed or gear. If I recall, it wouldn't even rev past 5k in neutral.

Anyway, something to consider.

Cats are good. Entire exhaust was upgraded to EMS stainless replacing everything and that was done in 2011 ish if I followed the previous owners build thread correctly.