In the above calcs he's making 63psi drive pressure for 45psi inlet pressure
5L Pump or 2L Pump 60psi boost
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Yes I know, I don't take much notice of guess work/paper calculations. It only takes one tiny error or guessed the wrong input for something and it throws the whole outcome off. They very rarely correlate to actual real world results but handy to get in the ball park. No one I've ever dealt with or has done compounds before would go to the effort of compounding turbos to still have EMP higher than boost.
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- #24
Okay so should have EMP lower than intake pressure. I think I will definitely put a gauge on for testing. I thought a good setup would be 1-2psi higher
John in Utah
SILVER Star
The 2LTE and 2LT-II of that vintage had ceramic fiber reinforced ring lands (I found an old SAE paper on them). Maybe the 5L has something similar? Or Toyota may have gone to regular alfin style reinforcement. I can say that after years of 20psi and fuel to match, the piston ring clearances in my old 2LTE short block were well within spec still and looked great. Still have the pistons on a shelf actually. Rods and crank too for that matter.
Edit: Found a picture of an OEM 5L piston.
Are you sure the 3L pistons don’t have the cooling passage? I’ve found pictures that seem to indicate they have both reinforced ring lands and the cooling passage in the crown. Never held one in my hand though.
I’m looking at the hole only partly visible at the top of the underside of the 3L piston in this picture.
It's possible they've revised the newer part numbers, but I'm positive the originals didn't have a cooled crown. Here are pictures I've dug up in the past. Also, the factory repair manual has a cut away picture of both engines, and if you look closely at the piston crowns, you can see the 2LT-II ones are cooled and the 3L not.
In my pictures below, it does look like the 3L have an 'alfin' style insert to reinforce the top ring land. But if you look at the 2LTE piston pictures, you can see a very thick area that is a different color. That is the ceramic fiber re-inforced area. If you want detailed pictures of the 2LTE pistons I have at home, I can post some as well.
2LT-II from manual
3L from manual
2LT-II/2LTE pistons:
3L pistons:
3L pistons:
John in Utah
SILVER Star
Sure enough, the 54101 is a replacement for the 54100 which I assume is original. Not sure why your photos show a different 54101 though. I should just stop questioning the wise @GTSSportCoupe 
I wish this was on my mind a month ago when I pulled my BEBs, I could have looked for myself. Guess this is just one more thing to be paranoid about when I go turbo
Sorry, thread hijack over.
I wish this was on my mind a month ago when I pulled my BEBs, I could have looked for myself. Guess this is just one more thing to be paranoid about when I go turbo
Sorry, thread hijack over.
Sure enough, the 54101 is a replacement for the 54100 which I assume is original. Not sure why your photos show a different 54101 though. I should just stop questioning the wise @GTSSportCoupe
I wish this was on my mind a month ago when I pulled my BEBs, I could have looked for myself. Guess this is just one more thing to be paranoid about when I go turbo
Sorry, thread hijack over.
Haha, I don't know it all (surprise!
). In fact it's nice having someone else on these forums who cares about the finer details of these engines. You've made me double guess my assumptions on more than a few occasions now!I really wouln't worry too much about it either way. The only advantage to the crown cooled ones, is helping the pistons last a little longer if your EGT's are WAY too high (which they won't be if you have an intercooler and smart tune). Structurally, maybe the solid crown pistons are even stronger? 3L's have proven time and again to take to turbo just fine. The weak point for regular turbo setups (not 60psi!) on these motors is the cylinder head, not the short block. And actually, the cylinder head is not weak in that combustion pressures cause issues. It's weak in that thermal fatigue around the precups/valves eventually causes failure in the form of cracks. This is why I run a waterless coolant - to prevent localized boiling and superheating around the precups under high engine load and high coolant temps. I've got 100,000km of abuse on my cylinder head; and it's still good. I've hit red on the factory temp gauge a few times every summer for the past 8 years while towing.
For a single turbo setup that would be ok and quite normal for it to be higher than that but not for a compound setup.
The small turbo wastegate needs to get it's signal from total boost which is the same as it normally would as a single turbo. The big turbo from only it's own boost. But you need the little turbo wastegate to set total boost. Which is your 45psi. This will be difficult with off-the-shelf wastegates but may be possible to reach with additional external springing.
You can only control boost vs EMP by turbo selection. The turbos you have are running hot side too small to achieve that at max power. But at max torque you should be closer.
Going to a bigger turbine on the big turbo will help.
Lots of people have no idea how turbochargers work with pressure vs temperature but will still pretend they do.
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- #32
You can get an external waste gate to do any pressure you need, by applying pressure to the top of the diaphragm. I think having the small turbo set to 45psi will make it do all the work, the pressure ratios will be very uneven. I think get some pressure out of the manifold to the second turbo before max boost would make the turbos work as a team. The second turbo will be free floating which allows the fuel to control boost.
Yes an external gate will make it a lot easier.
The pressure ratios will sort themselves out with my setup. Big turbo gate set to 22psi, small turbo gate set to 45psi. You'll end up at max power with pressure ratios of 2.5 for the big and 1.6 for the little.
The little turbo never makes 45psi by itself. It simply can't.
During spoolup the small turbos job is to get engine air and exhaust flow high enough for the big turbo to start working. Once the big turbo starts working the pressure ratio on the small turbo drops to your target and the big turbo rises to it's wastegated target.
Your big turbo is too small to be free-floating. It's exhaust housing is currently too small and it'll choke the whole system to higher exhaust pressures and lower power. Made worse by pushing the compressors to really ugly parts of their maps. You also can't run even pressure ratios here as the big turbo compressor is almost undersized and needs that 2.5x pressure ratio to keep the air-flow points on the compressor map.
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- #34
So what engine turbo setups have you done can you link some build threads? Just as I don’t take financial advice from some with less money than me, I want to know the you have actually built some compound turbos diesels.
So what engine turbo setups have you done can you link some build threads? Just as I don’t take financial advice from some with less money than me, I want to know the you have actually built some compound turbos diesels.
I don't do the building, just the designing. If you want my CV I'll give you my paypal account so you can compensate me for my time. There's only a certain amount of time I have to help people for nothing.
Take a look here and on 4BTswaps.com over the last 15 years. There are hundreds of people worldwide running turbos I've sized for them. Toyota, Isuzu, Cummins, VW etc. Most are single but some notable compound builds.
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- #37
Had some problems with the alternator wiring Changing to internal reg, so the glow plugs would not work, found a diagram with the wire colours and sorted that. Give it a bleed tighten up the injector pipes and it fired up first pop. Posted a video on instagram @dakalberry
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Not sure how to post here