Build-up: Jeep YJ w/ Isuzu diesel

[iroc86]

Hi guys, I used to lurk on PghOffRoad back when it was a Yahoo! group and never really got involved with the new message board until now. Krod came across my build-up thread on Pirate4x4 and suggested I post it here. Hope you all enjoy it.

I started with a '95 Jeep Wrangler that was relatively cookie-cutter: 2.5L, five speed, and 33s. It worked great off-road, but it wasn't as sturdy as I thought it should be. So, I decided on a few upgrades... turbodiesel engine, SM465 transmission, NP205 transfer case, Dana 44 front, Ford 8.8 rear, and SOA conversion. I'll be running 35s on a 100" wheelbase.

Here are a few pictures of my progress so far, but the thread over at Pirate4x4 is much, much more detailed. I plan on having the Jeep roadworthy by the end of summer.

[meatloaf]

i've been following this build on pirate. didn't know u were so close! nice work.

-Kyle

[OverkillZJ]

That is awesome! Welcome to the group, I can't wait to see that thing on the trails some time.

[highlandercj-7]

Nice job! What I-snooz-u is that there engine out of? Any idea on the output? My friend dumped a 5 cyl Mercades in his CJ-7. We are always looking for more oil burners to transplant lol...

[MF Steve!]

Welcome. I remember that thread from PBB. Very impressive. This is the kind of shit we need more of on Pgh Off Topic!

[Alley]

I am a huge diesel fan, this should be amazing. I can't wait to see it all done!

[iroc86]

Thanks for checking it out, guys! I'm getting anxious myself to finish up and hit the trails again. It'll be really interesting to see how the diesel performs off-road.

highlandercj-7, the engine came out of a '95 GMC W4 tilt-cab. It's a 4BD2-TC, turbocharged and intercooled. Displacement is 3.9L and it puts out 137 hp @ 2800 rpm. The torque rating is 265 lb-ft @ 2000 rpm, but the torque curve is nearly flat from 2000 rpm all the way to 2800 rpm. It's incredible. The Cummins 4BT, another popular diesel swap, can't touch the Isuzu past 2000 rpm. I've posted official dyno charts in the Pirate thread, if anyone's interested.

I bought the GMC truck in Philadelphia and drove it home across the state. That was a fun trip. Here we are at Bob Evans in Breezewood...

[gonecheenin]

Nice

All mechanical diesel I assume?

What did you use to mate the engine to the tranny?

[MF Steve!]

Nice

All mechanical diesel I assume?

What did you use to mate the engine to the tranny?

I believe you can use the typical Chevy bellhousings with an NPR diesel, as they share many common driveline parts.

[notmYJ]

Awesome!!! I have really considering this swap for my YJ. Looking forward to see how this goes.

Now the big question.... What is the race car in the background on the Weld ProStars?

[90LiftedYJ]

looking really good man keep up the good work. keep us posted with updates.

[gonecheenin]

I believe you can use the typical Chevy bellhousings with an NPR diesel, as they share many common driveline parts.

I was thinking that too, but in his pics it looks like theres a thinner adaptor in there (course, that could be a factory offering too)


Wonder what fuel mileage he's going to get out of that model engine? Even with diesel @ 4.50 it might still be a worth while swap for me @ 35+ a gal with finding a cheap enough swap canidate (2500 for a 4BT is just silly & not worth it IMHO)

[iroc86]

Let me address those questions...

The Isuzu 4BD2-TC is very similar to the older 4BD1-T, which was a completely mechanical engine. The updated engine does have a kind of "computer," but from what I gather, it's more of a logic system that controls the glow plug timer and the engine warming system, plus a couple other things. The injection pump is all mechanical.

This engine has a proprietary bellhousing and is not compatible with anything but Isuzu transmissions. I've heard reports that older versions of the 4BD1-T from the mid-80s could be had with a Chevy adapter, but only for industrial applications (e.g. generators). Those parts aren't available anymore.

I had my mind set on using the SM465 because of its gearing and size, so I designed an adapter plate. The plate is 13" in diameter and made from 1" thick 6061 aluminum alloy. It converts the metric Isuzu bolt pattern to the Saginaw truck pattern used by the SM465. The aluminum bellhousing in the other pictures came from the automatic transmission in the box truck.



Due to the fitment of the diesel's flywheel, I need to make another adapter to use a Chevrolet clutch. The Isuzu flywheel will still be used for the starter motor. Even with two flywheels, the engine will not be overloaded from rotating mass -- the factory torque converter for the NPR's automatic transmission weighs about as much as my configuration.

Starting with post #51 in the Pirate thread, I go into a lot more detail about the adapter. Another fellow, dieseltim, posted his results there, too. His adapter mates the NV4500 to the Isuzu diesel, but it doesn't use two flywheels. The NV4500 has a slightly longer input shaft that is able to reach the factory diesel flywheel. That wasn't an option for my SM465.

As far as mileage goes, I'd be happy with 20 mpg, but I'm hearing about guys who are getting upwards of 30-35 mpg in their vehicles. (The Isuzu diesel swap is pretty popular for the Land Rover guys, especially in Australia.) The box truck averaged about 12 mpg on the turnpike, but the engine is due for a rebuild with 225,000 miles on the clock. Cruising speed was around 65-70 mph, and I don't think these trucks are geared for economy at those speeds. Minimum BSFC occurs near 2000 rpm, and I'm sure it was operating well above that.

[DMG]

Let me address those questions...

The Isuzu 4BD2-TC is very similar to the older 4BD1-T, which was a completely mechanical engine. The updated engine does have a kind of "computer," but from what I gather, it's more of a logic system that controls the glow plug timer and the engine warming system, plus a couple other things. The injection pump is all mechanical.

This engine has a proprietary bellhousing and is not compatible with anything but Isuzu transmissions. I've heard reports that older versions of the 4BD1-T from the mid-80s could be had with a Chevy adapter, but only for industrial applications (e.g. generators). Those parts aren't available anymore.

I had my mind set on using the SM465 because of its gearing and size, so I designed an adapter plate. The plate is 13" in diameter and made from 1" thick 6061 aluminum alloy. It converts the metric Isuzu bolt pattern to the Saginaw truck pattern used by the SM465. The aluminum bellhousing in the other pictures came from the automatic transmission in the box truck.



Due to the fitment of the diesel's flywheel, I need to make another adapter to use a Chevrolet clutch. The Isuzu flywheel will still be used for the starter motor. Even with two flywheels, the engine will not be overloaded from rotating mass -- the factory torque converter for the NPR's automatic transmission weighs about as much as my configuration.

Starting with post #51 in the Pirate thread, I go into a lot more detail about the adapter. Another fellow, dieseltim, posted his results there, too. His adapter mates the NV4500 to the Isuzu diesel, but it doesn't use two flywheels. The NV4500 has a slightly longer input shaft that is able to reach the factory diesel flywheel. That wasn't an option for my SM465.

As far as mileage goes, I'd be happy with 20 mpg, but I'm hearing about guys who are getting upwards of 30-35 mpg in their vehicles. (The Isuzu diesel swap is pretty popular for the Land Rover guys, especially in Australia.) The box truck averaged about 12 mpg on the turnpike, but the engine is due for a rebuild with 225,000 miles on the clock. Cruising speed was around 65-70 mph, and I don't think these trucks are geared for economy at those speeds. Minimum BSFC occurs near 2000 rpm, and I'm sure it was operating well above that.

I have seen the Isuzu/GM box trucks with an SAE round bellhousing which GM transmissions should bolt to... Is that only newer trucks?

[iroc86]

I have seen the Isuzu/GM box trucks with an SAE round bellhousing which GM transmissions should bolt to... Is that only newer trucks?

Are you sure it was SAE? The closest way to describe the bolt pattern on the 4BD engines is that of a "metric" SAE. It's round like SAE, but the dimensions are different.

[DMG]

Are you sure it was SAE? The closest way to describe the bolt pattern on the 4BD engines is that of a "metric" SAE. It's round like SAE, but the dimensions are different.

I am not 100% sure about that but I know I have seen GM automatics in NPR diesels.

I just searched a bit. It sounds like a variety of different stuff went behing Isuzu diesels in various applications. At work, I see small Isuzu dsls adapted to Ford C6s every day.

[iroc86]

Maybe the newer trucks are using GM transmissions? I think the automatic in my NPR truck was made by Aisin. Then again, GM has been a significant shareholder of Isuzu since 1971, so I wouldn't be surprised if they were one and the same.

[DMG]

Maybe the newer trucks are using GM transmissions? I think the automatic in my NPR truck was made by Aisin. Then again, GM has been a significant shareholder of Isuzu since 1971, so I wouldn't be surprised if they were one and the same.

I am trying to remember what year I was looking at...

[highlandercj-7]

sweet! I'll be following this close. I want to 4bt my CJ-8 in the worst way.

[DMG]

Maybe the newer trucks are using GM transmissions? I think the automatic in my NPR truck was made by Aisin. Then again, GM has been a significant shareholder of Isuzu since 1971, so I wouldn't be surprised if they were one and the same.

Either way, this is a sweet build. I would like to put an Isuzu diesel in my T100 if I keep it. Anyone know where I can find a 4BT or the NPR motor cheap?

[iroc86]

Anyone know where I can find a 4BT or the NPR motor cheap?

Before I found my NPR truck, I called every truck junkyard, commercial auction, and diesel outfitter place in the tri-state area looking for an engine, Cummins or Isuzu. Nothing. And the places that had parts wanted an arm and a leg for them... I think one shop quoted me $4000 for a used 4BT block, sans turbo and accessories.

I think the best way to do a swap like this is to find a complete donor truck. You never know what you might need. I'd suggest looking on eBay or Craigslist. It's surprising what's out there.

[UPJ Wheeler]

This is a kick ass build!!! I cant wait to see the final product! Ill buy you a case of your favorite beer to let me drive it down the street and back once its all done!!!