Quote:
Originally Posted by 88tlc
dougal and company, thanks for the comments. you are right, that the 3.9 should not perform like a 5.9! the trucks are about the same weight empty, i do expect to have that same torquie power though.
egt to preturbo - that means removing the turbo? I guess i should just rebuild it then while I have it off, seems like the only thing not rebuilt on the motor. Preturbo is more accurate temp reading?
fuel pump - I have a inline low pressure mallory I added back near the tank, and the lift pump on the IP.
boost compensator? - is that the aneroid, altitude compensator? besides this on the back of the IP, there is nothing else.
Timing - is there a more accurate way to get the 13 deg BTDC on the IP? I take #1 line off, and turn the engine over, see the fuel rise in the delivery valve. i would guess this is accurate to within a few degrees only.
egt temps - wow - that is like 1700 deg F. It does feel like the engine is just getting into its game, getting power, getting boost, when I am having to back off of a 1050 to 1100 egt. would be great to let er bark to like 1300 or 1400 F, but I am obviously concerned about melting something down!
rpms - I have yet to truly calibrate this tach, I can only estimate from a idle and governed rpm. with the over drive on the rpm is running approx 1500 to 1700. I do think this will work great on the open flats, great gas mileage. but it does feel geared high, especially with the 33 tires on there.
a quick movie of the engine running after rebuilding the IP.
YouTube - 1988 fj62 landcruiser with isuzu diesel engine |
Yes the EGT probe before the turbo gives a more accurate reading, the turbo causes a temperature drop which depends on the temperature it's running at, it's efficiency and the boost it's currently putting out.
Some people use a fudge factor of 100-300 deg to compensate for the probe being after the turbo, but it's not a good idea.
I have no external lift pump, the mechanical lift pump (with the hand primer pump attached) gives all the pumping your engine needs.
Some engines have an altitude compensator (FSM calls this an aneroid) which is a round device with no lines attached. The boost compensator fitted to some engines is cast aluminium and screwed together with a pressure line to the inlet piping.
Some engines have both, some have none. My engine has the boost compensator only.
Listening to your video, your engine sounds more advanced than mine currently is. I've been experimenting with the timing a little over the last few months by incremental adjustments.
Too far advanced can make the engine fall off boost, it would lead to situations where EGT's would keep rising but not produce boost and cause me to back off to save the engine. Knocking the timing back a little (rotate top of the pump away from the block) brings on boost sooner.
The interesting part, I've found no noticeable difference in fuel economy going from far advanced and right back to what I think is slightly retarded from the factory setting. I haven't confirmed my timing by any method like the one above.
You'll notice the difference in idle sound that a relatively small change in timing makes.
1500-1700 is not a speed you'll be climbing hills at 65mph with. In stock form this engine will only be putting out around 52kw (70hp) at 1500 rpm.
The stock turbo may also not be producing enough boost there.
Regarding turbos.
I have a turbo like yours in my parts bin, but I haven't installed it as I'd need to redo all my plumbing (exh, intake, oil lines etc). The exhaust A/R on it is significantly bigger than the wastegated T25 turbo I'm currently running, but the compressor is identical. With increased fuel I get 20psi boost by 1500rpm.
Carcrafter on 4btswaps.com has fitted a holset to his 4BD1T, I don't think he's got any driving reports yet.