Thread: Yet more turbo questions!

Nice. Plenty of room for improvement if you're only hitting 420deg now.
How responsive is the gauge? Mine jumps up by 200deg in a couple of seconds if I give it a bootfull, and drops instantly as soon as I lift my foot.

Is it intercooled, and what's the wastegate set at?

Steve

Originally Posted by steveG

Nice. Plenty of room for improvement if you're only hitting 420deg now.
How responsive is the gauge? Mine jumps up by 200deg in a couple of seconds if I give it a bootfull, and drops instantly as soon as I lift my foot.

Is it intercooled, and what's the wastegate set at?

Steve

The gauge seems to be reponding instantly, so I have no reason to doubt it's accuracy.
No intercooler, YET, SWMBO is still on the warpath over what I've spent already. The wastegate has a 1.5Bar spring and the rod is adjusted till the spring just starts to compress, so plenty of scope to load it up a bit more.

With no intercooler if you tune for 750C sustained at 20psi you'll get about 480Nm and 120kw.

Unfortunately from there increases in boost give very little increase in power without an intercoooler. You end up using most of the density increase to offset the temp increase.

Unless you just ignore the EGT gauge. You'll get to ~550Nm and 140kw before smoke becomes a problem, but I wouldn't go there without piston squirters.

Thanks, Dougal, I reckon I'd be pretty happy with 120kw! Do you know if the piston squirters are something that can be retro-fitted? As my block had the turbo oil return hole already in the block, I'm hopeful that the tappings for the squirters may be similarly there, but plugged. Not so much as I want to push the limits on output, but as just as a little extra "Insurance".

Originally Posted by jackz

Thanks, Dougal, I reckon I'd be pretty happy with 120kw! Do you know if the piston squirters are something that can be retro-fitted? As my block had the turbo oil return hole already in the block, I'm hopeful that the tappings for the squirters may be similarly there, but plugged. Not so much as I want to push the limits on output, but as just as a little extra "Insurance".

From memory there was a change to a (higher volume) different oil pump at some stage, so that might be necessary as well as just the squirters.
Was talking to a guy who got a price on genuine squirters from Isuzu a couple of years ago - around $500 for the set of 4.

Steve

Originally Posted by steveG

From memory there was a change to a (higher volume) different oil pump at some stage, so that might be necessary as well as just the squirters.
Was talking to a guy who got a price on genuine squirters from Isuzu a couple of years ago - around $500 for the set of 4.

Steve

If they are like this:Capture jet.jpgItem #56, around $19.00 each from the U.S.
Would be interesting to have the part #s for the required parts includind the higher volume oil pump to see if it's worth doing...

The change to the high volume pump occurred in late 1988. Together with the pump change, they used a smaller jet tube in the squirters for better piston cooling.

Edit:
The part number for the higher volume oil pump used on the 4BD1T from late 1988 is 8943662410

The oil jet for piston cooling for the 4BD1T from late 1988 is 8943196990 (item 56 on the diagram above)

The valve for the oil jet for the 4BD1T from late 1988 is 1131610120 (item 132 on the diagram above)

This is the mob in the states I got the turbo manifold from, US$156 +$55 shipping. Aust Isuzu dealers were quoing me around $360

Isuzu NPR Parts - Save on OEM Isuzu truck parts from Nalley Isuzu | Nalley Isuzu Commercial Truck Parts
1131610120 VALVE. CHECK,OIL; $ 7.96 each
8943196990 JET. OIL,PISTON COOLING; $ 24.44 each
8943662410 OIL PUMP AND OIL STRAINER; $ 258.71