Cummins 4BT & Diesel Conversions Forums banner

1 - 12 of 12 Posts

·
Super Moderator
Joined
·
8,673 Posts
Discussion Starter #1
Hey guys.

I'm on the hunt for official Isuzu 4BD1T power/torque curves. So far the only thing on the net is a low resolution scan of a NPS 300 truck from Australia. I think we need to find some original NPR sales literature from the early 1990's.

If anyone can help, post up and let me know. Anything to big to be uploaded directly can be emailled to me and I'll see what I can do.
 

·
Registered
Joined
·
268 Posts
Would anyone care to postulate why the Cummins has a higher torque and power output than the Isuzu? We all know that either can be tuned up, but from the factory the Cummins seems to have a pretty solid advantage over the Isuzu.
 

·
Registered
Joined
·
191 Posts
I would guess it has something to do with the turbo, everything else about them is almost the same. The stock hx30 that the 4bt is fitted with outperforms the freefloat garrett. The curve on the 4bd is flatter though,a nd it seems like the 4bd is a higher rpm engine than the 4bt, but then again that could have something to do with the turbo.
 

·
Super Moderator
Joined
·
8,673 Posts
Discussion Starter #9
Would anyone care to postulate why the Cummins has a higher torque and power output than the Isuzu? We all know that either can be tuned up, but from the factory the Cummins seems to have a pretty solid advantage over the Isuzu.
Honestly I think the japanese were just happy with a lower state of factory tune. They got numbers which were adequate to shift a 4 ton truck against their competitors Mitsubishi and Toyota/Daihatsu and stopped there. They weren't selling these engines against the 4BT.
They had access to IHI turbos capable of 30psi, these were used on marine 4BG engines, but they stuck with the 12psi or so and went with the more efficient garrett.

This still seems to be a common theme with light truck engines, very few of them boost past low teens. One turbocharger book I was reading (can't remember which) suggested the biggest benefit in efficiency and economy comes with low boost (up to 10psi), beyond that you are getting more power from a smaller package, but the efficiency gains taper off fast.
 
1 - 12 of 12 Posts
Top