handymanny01 wrote:Hey Isuzu Rob! Thanks,, looks good, but not performing as I'd like just yet,,, 100kw at wheels, 360nm, both at 2700rpm, so heaps to come if we can get it to inject properly,,, There is def a compatibility issue , either with the 4jh1 injectors and 4jg1 pistons,, or possibly in the custom pump,,, What sorta pump and turbo Combo are you running?
I hope that you guys are still modding these engines, it's all very interesting!
I played around with the camshaft timing a few years ago on a 2.4 toyota IDI to see what effect it would have on the powerband. I got 2 keyways ground into the camshaft drive sprocket (belt drive), one at around 4 degrees and one around 7 degrees. The effect was pretty huge, The IDI engine had a small combustion chamber in the head which lowered the compression ratio down from the N.A. engines 22-1 to a more turbo friendly 18-1, but I went a bit further and unshrouded the valves to lower the compression a bit more. The valve to piston clearance was really good so I could actually skip a tooth on the drive belt and play around with various amounts of camshaft advance and retard without any piston to valve clearance probs. The first major change was to advance the camshaft around 7 degrees relative to it's usual position, this turned the engine into a tractor with oodles of low end torque, it was strange driving around town without having to shift out of 4th gear most of the time, where as previously I had to row the gearshift to keep up with traffic. The downside was the lack of power above 3000 revs, which was so bad that out on the hyway I couldn't pass cars anymore because there was no power left.
I then retarded the camshaft around 7 degrees from standard and lost some low end (below 3000) but gained a fair bit of top end power, which made hyway driving much better. It only cost around $100 to get the slots ground into the camshaft sprocket so it wont break the bank and should enable you to experiment to see what works for your engine (valve to piston clearance allowing). I eventually went back to around 4 degrees retard to pick up the bottom end a bit because this was my daily driver. If valve to piston clearance is a problem then maybe you could sink the valves into the head a bit. Apparently if you fly cut the piston tops for valve clearance it kills the chamber swirl resulting in more smoke according to the online diesel engine builders. Do the different engines use the same camshaft specs? I also did some mods to the standard exhaust manifold which worked well, let me know if you are interested and I'll explain what I did.