2L+T conversion

[denis]

Today I almost finished converting the mighty 2L LJ70 with a turbo.
Everything from the factory 2L-T bolts on the 2L. Both were pre-1990 engines in LJ70s.
Here is the parts list in case anyone is interested :
-exhaust manifold,gasket and bolts
-manifold support bracket
-oil cooler/filter carrier/ assembly
-oil supply/dump pipe
-turbo
-crossover air pipe
-filter-> turbo hose
-primary exhaust pipe and support

I have not hooked up the watercooling yet, and I have not yet converted the fuel pump to boost-compensated style.

The only real fabrication needed is drilling the engine block where the dump pipe ends. The cast is the same between turbo and NA and the correct, purpose-shaped spot is therefore easy to find. Hole size is shy of 20mm for a good press fit.
I also needed to drill and tap four holes into the head for the different pattern. I drilled them 17mm deep, that's about how deep the stock holes are. I did not get through any oil of water passage.

Because it was in the way of the oil dump pipe, I relocated the oil pressure sender and its extension mount onto the next hole forward in the block, where the vac. pump oil feed came out. That one then came onto the highest spot onto the highest spot on the cooler/ filter carrier assembly. Lower spot is kept for the turbo oil feed. The 1/8 NPT plug from the top port went on the block where the pressure sender was. The stock 2L-Ts I have seen have the sender located close to the back side of the engine, but I didn't want to lengthen the wires so I did as described above. It's a bit tight in there now but it's OK.

I also drilled and tap the bottom of the exhaust manifold for the pyro probe, there's a perfect, flat location inbetween the cyl. #2 & 3 flange bolts levels, where you end up right into cyl. 3 & 4 pipe.

After a quick drive, stupid discovered where the bad whine and asmathic boost came from... dude had forgotten to bolt the turbo down tight

I will try to take a couple pics and do a bit of testing tomorrow if I manage to recover the cruiser from the muddy pothole it ended up tonight. I thought it was a good idea to try a mini snow run not too far from the shop, but those damn AT tires definately aren't worth @&@&@&@&.
The big bad BJ40 is coming out tomorrow

 

[denis]

I havent made any fuel adjustments yet, but the gain of power feels substancial above 2500rpm. NA setting used to smoke only slightly at full load, so the combustion ought to be more efficient with a bit of air excess, fuel quantity remaining constant.
Boost hits about 8psi, max EGT pre-turbo ~600C at 4500 rpm WOT. There seems to be some room for more diesel in there

 

[Tapage]

1/4 turn should be right ..

 

[crushers]

8 psi is the factory setting, you can easily go to 14 psi safely.
for the first couple adjustments i would go 1/2 turn, once you start either getting high EGTs or lots of black smoke then turn back out 1/4 turn till you are happy...
but 1/4 turns works just fine as well...
cheers and congrates...

 

[denis]

The LJ is now out of its hole. The bad thing is I need to replace the leaky turbo oil pipe gasket. I kept the old one which seemed OK. Oh well I guess I played and lost

I will play with the fuel setting just for the heck of it, 1/4 is what I was thinking about too, before things get nasty with the boost compensated pump.

 

[crushers]

do 0-100 with each crank to see the difference unless yuo have access to a dyno...just to get an idea of the changes...
cheers

 

[harveya]

The LJ is now out of its hole. The bad thing is I need to replace the leaky turbo oil pipe gasket. I kept the old one which seemed OK. Oh well I guess I played and lost

I will play with the fuel setting just for the heck of it, 1/4 is what I was thinking about too, before things get nasty with the boost compensated pump.

Use some of the high temp oil resistant instant gasket. the standard gaskets are rubbish as the oil pipe flange warps over time. If you have a metal gasket (some still have them), coat both sides with plenty of the instant gasket (not gasket sealant - the black silicon stuff that you use for the sump) on both sides of the metal gasket and then fit to the turbo. Use new metal locking nuts on the bolts and tighten up with a small spanner as tight as you can - there is so little space that it is impossible to get a torque wrench at it, so just do it up RFT (Really F***ing Tight).

Done this procedure quite a few times, one of the reasons that when I replace heads on 2LTs I leave the turbo attached to the manifold and unbolt the manifold from the head and just pull it out of the way.

 

[denis]

do 0-100 with each crank to see the difference unless yuo have access to a dyno...just to get an idea of the changes...
cheers

Actually I'll be simply looking for the best "very little smoke" adjstment, which will be my baseline for the next mods. I'm working on some kind of measurment device for some "road dyno" processing. The comparison between NA and turbo is somewhat pointless anyway since I don't have any data for the NA , but, according to the various trucks I've driven so far :
top fuel NA beats stock fuel turbo up till 2500rpm
top fuel NA beats top fuel turbo up till 1800rpm (compression ratio advantage)

I thought about trying to find how much you could extract from a modded NA, but the cost vs. benefit just woudn't be there. I decided to skip that and take the turbo route straight away, and see how far it could go, going one step at a time.
For now I'll set it up as a decent fueled stocker for a while until I have some kind of mesuring machine for quantifying the next mods

 

[denis]

OK I think I've tracked down and sorted all leaks
One thing you want to make sure when you swap the oil filter mount/ oil cooler assembly, is that the bottom plug on the oil gallery is closed tight, because it's a major PITA to get to when everything is in place

I did turn the fuel up 1/2 a turn, and it seems to work OK. There's a puff of black smoke at low revs/ WOT but half throttle is clean. The WOT smoke disappears when boost is reaching 6psi (21psi absolute), this would mean I could use 20% more fuel at maximum boost (10psi relative, 25psi absolute).

The boost and power response is pretty good. Here are some full-load numbers :
1600rpm 4.5psi ~400°C EGT (pre-turbo)
1800rpm 6psi 500C
2500rpm 7.5psi 600C
3000rpm 10.5psi 700°C

Strangely the power seems to cut right off at 3500 or 4000-ish (governor set at 5000), this might be a combination of compressor efficiency dropping as well as exhaust turbine and pipes restriction...

 

[denis]

I may have sorted out the power cut-off. The fuel filter, although it was only 2months old, was clogged with mud, some thin crap probably entered my fuel tank last time the cruiser bathed for a long time in liquid mud. The new fuel pickup is not leak-tight it seems
I will go racing and report back about the upper powerband
Still a long way till the 200hp mark

EDIT : the power cut-off disappeared, but the cure doesn't seem to climb much above 3500rpm.
Next steps : check the boost curve and work on the airflows