Build 15B-FT Shoehorned into a Canadian Spec 1986 BJ70

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Hello,

Yes, the FZJ70 pulls air from the upper right fender. There are two variants.

One setup has a pre-filter bolted to a plate that goes after the RH indicator. The pre-filter fits inside the fender. If I remember correctly, Toyota refers to it as "cyclone filter". In the lower half of the duct between pre-filter and air filter box there is a rubber cap that catches dust and expels it. Some people delete this cap and plug the hole for river crossings.

The other setup passes through the fender to the snorkel. This variant requires a different air box for the filter.

There is a plastic splash guard in the lip between upper and lower fender.

I do not have the part numbers at hand now. You need both the pre-filter (complete with the mounting plate, hardware and duct) and the splash guard for the air intake.






Juan
 
Thanks for the great write up. Your conversion was much more troublesome than mine, mostly because of the left handed vehicle.

I also started with a 3BII which means no flywheel, engine mount or power steering issues, and a rotary injection pump with factory fuel return pipe. I decided to keep the original power steering pump so never looked at using the huge Mega Cruiser pump, but on a 60 there looks to be plenty of room.

Mine is a BJ60 install, I too lacked the space for the intercooler and will just run without it.

1000028053.webp


I made a bracket to mount the original accelerator crank to the intake manifold. Now I only need to modify my Mega Cruiser crossover pipe, the air filter box lid, exhaust, heater pipes, turbo coolant hoses and crankcase vent pipes. My engine is the 8 valve 15B-T with high mount CT26, basically a bored out 14B-T.
 
AlbertoSD said:
This, very much so. You did all the work. We might have provided small technical assistance if any. Well done, Larry!
Click to expand...
Phone data (# of minutes, # of texts, data storage) indicates much more than small technical assistance. Your humble modesty is another positive attribute in your personal character.
Thank you
 
Owyhee Jackass said:
Wow, great write-up. Thanks for taking the time to explain the challenges. And, your writing ability/capability is just fine, no need for the disclaimer.

I did a 14B-T into my 3BII powered BJ75 a while back and had similar challenges, nice job working through them. I think the bell housing on the 3BII accepts the 14B (and maybe the 15B?) better than the 3B bell housing i.e. you can run the bigger flywheel and clutch and the support mounts work without customization. Sourcing one is probably tough though.

Did you have to source a different air cleaner assembly?
Click to expand...

JuanJ said:
Hello,

Yes, the FZJ70 pulls air from the upper right fender. There are two variants.

One setup has a pre-filter bolted to a plate that goes after the RH indicator. The pre-filter fits inside the fender. If I remember correctly, Toyota refers to it as "cyclone filter". In the lower half of the duct between pre-filter and air filter box there is a rubber cap that catches dust and expels it. Some people delete this cap and plug the hole for river crossings.

The other setup passes through the fender to the snorkel. This variant requires a different air box for the filter.

There is a plastic splash guard in the lip between upper and lower fender.

I do not have the part numbers at hand now. You need both the pre-filter (complete with the mounting plate, hardware and duct) and the splash guard for the air intake.






Juan
Click to expand...
As I alluded to changing the air-cleaner assembly and duct to the fender, I got the parts in and completed the swap. The mideast air-cleaner assembly was needed to pull air from within the right front fender, plus the duct to the fender and windshield washer fluid reservoir. The original windshield washer reservoir blocked the hole in the fender that duct was fed through.

Installation before the change
20250702_210437.webp

Installation after the change
20260206_145723.webp
 
Not actually part of the 15B-FT installation, but I replaced the horn contact pin in the steering column. The horn had started to only work when the steering wheel was turned right, which isn't actually functional for me.

Here is a picture of the new pin along side the old pin. The amount that the old pin has worn away and only recently stopped being functional struck me as impressive.
20260205_132525.webp
 
LDowney said:
As I alluded to changing the air-cleaner assembly and duct to the fender, I got the parts in and completed the swap. The mideast air-cleaner assembly was needed to pull air from within the right front fender, plus the duct to the fender and windshield washer fluid reservoir. The original windshield washer reservoir blocked the hole in the fender that duct was fed through.

Installation before the change
View attachment 4081595
Installation after the change
View attachment 4081596
Click to expand...
Hello,

I forgot about the washer bottle. My mistake.

That is a neat setup.





Juan
 
Owyhee Jackass said:
Pretty slick that you got all that 'stock' and bolted up w/ no fabrication necessary. Good work.

What's your impression of performance compared to the 3B so far?
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Several bolt holes did not line up which required fabrication of several adapters to enable bolt up.

The 15B-FT is a true game changer from the 3B in performance relative to expectations for a truck. The 15B-FT did not transform the BJ70 into a sports sedan or similar.

With the 15B-FT,
  • I have power to keep up traffic briskly accelerating from a red light
  • I can readily accelerate to interstate traffic speeds via the on-ramp
  • On the steep trails, engine braking is enough provide a slow controlled decent without brakes
  • Cruises on the interstate at 2200rpm which provides speeds over 70mph, i.e., keeping pace with the majority of cars/pickups while passing most semis
  • The boost is controlled where it is never an active effort to monitor/manage.
  • EGTs still require monitoring on long steep grades; the engine has plenty of power to run up all the hills that I have encountered, but I need to be mindful of keeping EGTs below 1200F (i.e., On some grades, I let off on the throttle and let her slow to 65mph or so to keep the EGTs absolutely below level for concern)
  • The intercooler that I opted for was an air-to-water; since he EGTs can rise on me, I might not have the electric water pump and/or water heat exchanger under sized. This might be an area for refinement (down the road item at this time)
Are there considerations that you are interested in that I did not hit?
 
LDowney said:
  • The intercooler that I opted for was an air-to-water; since he EGTs can rise on me, I might not have the electric water pump and/or water heat exchanger under sized. This might be an area for refinement (down the road item at this time)
Click to expand...
Barrel style air to water cores are not the most efficient, a block style core with collector ends is much better as you get more air across the exchanger
1770437317030.webp

and up sizing the coolant line and pump is the next bottleneck
 
bj70bc said:
Barrel style air to water cores are not the most efficient, a block style core with collector ends is much better as you get more air across the exchanger
View attachment 4081831
and up sizing the coolant line and pump is the next bottleneck
Click to expand...
I reviewed that configuration and opted for the barrel because it had ample performance capacity for the 15B-FT and was smallest option available (i.e., it had a better chance of fitting with the space I had). But I fully agree that the pressure drop of the air across the block style configuration should be much lower due to the larger airstream frontal (block style) heat-exchanger area versus wetted length that the air travels through the (barrel) heat-exchanger.

Additionally, I rechecked the info on these units from the supplier I purchased from
  • The smallest barrel configuration available (from the suppliers I found, which all seemed to have the same or nearly identical products) was rated to handle 390CFM/270Hp engines.
    • This appeared to be more than enough capacity to handle the needs of the 15B-FT. [and as a result, why I suspect that my water pump and/or water heat exchanger selections more that the barrel intercooler. The water pump & water heat exchanger had no analysis backing their selection; just what I could find in 24V and fit in front of the radiator]
  • Where the smallest block style (from the same supplier) is rated up to 450CFM/350Hp.
This is a step up in capacity (+65% over the ample capacity of the barrel configuration) which meant larger size with increased challenge for integration. i.e., 270hp with the Barrel style is oversized relative to the output of the 15B-FT, but 350Hp with the Block style is a bigger increment yet above the 15B-FT needs.

I probably made poor choices, but I totally love what I have and will actively try to learn how (if) I can improve on the integration.

Thanks for the feedback. Details/discussion that I probably should have included before.
 
Owyhee Jackass said:
Fuel economy?
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  • Good economy* (data points: +21mpg at +70mph, ~24mpg at 55mph)
This is how I summarized fuel economy in my first post.

All I can add was on a trip back from North Carolina last year, I tested cruising 79-84mph to see if I could cruise there and the mpg appeared to be just over 19mpg. In this test, I had to be very attentive to EGTs and the road manners of my BJ70 running over 80mph were stressful. As a result, I concluded that ~71mph was a cruise speed that I am happy with so I have not collected more mpg data points at this speed
 
It would be interesting to monitor intercooler coolant temperature to see if the cooling system is performing as it should. Elevated coolant temperature at the intercooler core inlet would indicate a need to upgrade the pump or heat exchanger.
 
AirheadNut said:
It would be interesting to monitor intercooler coolant temperature to see if the cooling system is performing as it should. Elevated coolant temperature at the intercooler core inlet would indicate a need to upgrade the pump or heat exchanger.
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just pull over and touch the intercooler core with your hand... youll know
this will tell you alot about how hot its input and output are, if you are getting rad heatsoak from placement or if its just cool (and egt still too high) in which case the air is going over it too fast to pull the heat out with sufficient contact time with the core (what i suspect)
also touch the reservoir and heat exchanger rad to diagnose

I have an air to water on my turboed 3b on 20psi boost.... from 15 psi to 20psi my egt went down ( without more fuel added after 12-15psi).... no more power really just less heat (more air, less fuel, leaner cooler burn) i still push 1200f tho
 
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I feel like you might be up against cfm on
That intercooler. Here’s the math I was doing when I swapped turbos, I think it’s mostly accurate 😂

13BT, 3400cc = ~208 cubic inches.
208ci x 3400rpm divided by 3,456 = 205
205 x .80 efficiency = 164cfm (is my efficiency too low?)

2:1 that would be 327cfm at 14.7psi
3:1 would be 492cfm at 29.2psi

So the15bft is 4.1
4100cc = 250 cubic inches
250 x 3200 divided by 3,456 = 231
231 x .80 =185

2:1 would be 370cfm at 14.7psi
3.1 would be 555cfm at 29.2 psi


So you aren’t running 30psi I assume, but if you are running 14ish then by my math you are pretty close to that 390cfm “stated” by the intercooler mfg. that is at a redline of 3200 and 14.7 psi.

Sounds like it’s running pretty good, but I’d bet going to a different intercooler would help form sure.
 
FJBen said:
I feel like you might be up against cfm on
That intercooler. Here’s the math I was doing when I swapped turbos, I think it’s mostly accurate 😂

13BT, 3400cc = ~208 cubic inches.
208ci x 3400rpm divided by 3,456 = 205
205 x .80 efficiency = 164cfm (is my efficiency too low?)

2:1 that would be 327cfm at 14.7psi
3:1 would be 492cfm at 29.2psi

So the15bft is 4.1
4100cc = 250 cubic inches
250 x 3200 divided by 3,456 = 231
231 x .80 =185

2:1 would be 370cfm at 14.7psi
3.1 would be 555cfm at 29.2 psi


So you aren’t running 30psi I assume, but if you are running 14ish then by my math you are pretty close to that 390cfm “stated” by the intercooler mfg. that is at a redline of 3200 and 14.7 psi.

Sounds like it’s running pretty good, but I’d bet going to a different intercooler would help form sure.
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It is my understanding that the displacement of the 15B-FT is 4.05 liters and the max boost is nominally 11 psi (with 4-6psi while operating at 2200rpm). With the Toyota boost controls, it is rarely at (or even near) max boost. Also, I don't recall ever throttling the 15B-FT up to 3200rpm so I don't have insight to what the EGTs and boost might look like there. I will see if there might be opportunities to get some data points.

So there is more margin on the intercooler than your figures reflect, but a quantatative perspective lends valuable insight. Thanks
 
LDowney said:
It is my understanding that the displacement of the 15B-FT is 4.05 liters and the max boost is nominally 11 psi (with 4-6psi while operating at 2200rpm). With the Toyota boost controls, it is rarely at (or even near) max boost. Also, I don't recall ever throttling the 15B-FT up to 3200rpm so I don't have insight to what the EGTs and boost might look like there. I will see if there might be opportunities to get some data points.

So there is more margin on the intercooler than your figures reflect, but a quantatative perspective lends valuable insight. Thanks
Click to expand...
rule of thumb is you are supposed to size your intercooler core at double the hp rating (cfm whatever) so you have the best chance of cooling properly, these cores stats are kind of BS
 
Thanks for the info. I was not aware of that. Could you point me at resources to learn more? Thanks
 
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