F/2F vs 3F torque differences (1 Viewer)

[brider]

This is just for my own education, but I was flipping thru the SOR catalogue looking for pics of my heater control, when I stopped and looked at the listed specs for the F, 2F, and 3F-EFI engines. The 3F apparently develops it's max torque at 3k rpm, and it ain't much more than the F at 2k rpm. Or the 2F, for that matter, at 1800 rpm!

So what is the attraction of the 3F (besides being modern, and FI)? I would imagine the higher horsepower is great for the highway, but is a torque peak at 3K still OK for off-road?

 

[matt.mcinnes]

Your thoughts are correct low down torque is better off road.

 

[Godwin]

I have two FJ60's, both set up very similar with 4.11's, 33's, and manual tranny. Major difference between the two is that one retains the 2F the other has a 3FE. The low end torque difference is noticeable; with a load the 3FE tends to bog down but the 2F just chugs along. On the highway at higher speeds the 3FE gets the nod.

 

[handcannon]

Your thoughts are correct low down torque is better off road.

This is good info. Anybody know where I can find this same type info on the "F" motor? Should be same stroke, different bore. I would also like to be able to compare the "F/2F" to a Chevy 292 I-6 motor. I really like the low end torque of my "F" motor but I wish it had a few more ponies. The 292 has torque written all over it with a bore of 3.875 and stroke of 4.120 and maybe 160 to 165 HP in stock configuration. It apparently is a direct bolt up to SBC bellhousings.

 

[RockDoc]

What would be really nice is if someone has dyno curves for each engine stock. I know Matt has one for his tweaked 2f in his 3F-ETI thread.

I would suspect that each of the engines has a fairly flat torque curve, so the higher max torque rpm of the 3fe is influenced as much by better breathing at a higher speed as it is by reduced stroke. After all, isn't the max torque point an expression of the point the "air pump" works most efficiently?

 

[RockDoc]

I actually, I think I'll take that back... My 3fe really comes alive at 2400 rpm, so I suppose the curve can't be too flat below that.

 

[tlc4x]

I have the curve you are looking for somewhere. It is in the FSM for the '92 or something. I'll try and find it and upload it. Unfortunately I have '90 - '97 FSM, wiring diagrams and everything else on my computer so it might take a bit.

What would be really nice is if someone has dyno curves for each engine stock. I know Matt has one for his tweaked 2f in his 3F-ETI thread.

I would suspect that each of the engines has a fairly flat torque curve, so the higher max torque rpm of the 3fe is influenced as much by better breathing at a higher speed as it is by reduced stroke. After all, isn't the max torque point an expression of the point the "air pump" works most efficiently?

 

[matt.mcinnes]

Torque curves are on here I think for 3FE page 16

http://www.yankeetoys.org/KLF/EPCDiags/1988_FJ62_New_Features.pdf

 

[tlc4x]

Bingo! I found mine... but I have the 3FE to 1FZ-FE comparisson. 1993 NCF.

Great site Matt. I can finally get the parts catalog!

 

[RockDoc]

Torque curves are on here I think for 3FE page 16

http://www.yankeetoys.org/KLF/EPCDiags/1988_FJ62_New_Features.pdf

Sweet, thanks Matt.

 

[RockDoc]

From Matt's link, for the 3Fe.

 

[tlc4x]

So at 1800 RPM the 3FE has around 210 ft-lbs of torque. That is better than the 2F. Looks to me like it is all around better. Good thing I finally decided to put mine in... But I've heard so many on here complaining that the low end torque of the 3FE is worse than the 2F. According to this the 3FE makes 200 ft-lbs at 1200 RPM.

 

[FJ40Jim]

We don't have the torque & HP curve for the 2.5F w/ the 8.3CR and improved manifolds and 3F head (10/84-later). The 2F info that has been translated to English is all from the original 1975 dyno testing.

 

[tlc4x]

Well, if we are talking 2F engines that came in an FJ40 then the 3FE is better. Maybe the FJ60 2Fs are better...

FJ40 Specs

We don't have the torque & HP curve for the 2.5F w/ the 8.3CR and improved manifolds and 3F head (10/84-later). The 2F info that has been translated to English is all from the original 1975 dyno testing.

 

[brider]

Looking at the torque curve for the 3F, it looks pretty flat; the SOR numbers I saw puts the peak torque at 3k rpm, while the 2F peaks at only 1800 rpm. At 1800 rpm, though, the 3F is still almost as torquey as the 2F. The venerable F is right in there at peak torque (absolute magnitude higher than the 2F) at 2k rpm. But that poor thing suffers from lack of HP.

And since GM engines were mentioned, does anyone know of anybody that has installed the old GM 305 V6 engine in a 'cruiser? I just read that that rascal put out it's massive peak torque (waaaay over 200 ft-lb) at only 1600 rpm!! Talk about a rock-crawler!

 

[tlc4x]

I figure my 3FE mated to an H55F should be plenty good. Granny gear first and overdrive fifth, all with a higher revving engine... best of all worlds.

 

[matt.mcinnes]

I figure my 3FE mated to an H55F should be plenty good. Granny gear first and overdrive fifth, all with a higher revving engine... best of all worlds.

The best solution is a 2FE bolted to a H55F

 

[tlc4x]

The best solution is a 2FE bolted to a H55F

Yes, yes, I know. But I will save that for when I need to rebuild the engine. It only has 79k on it so that may be a while.