3B compound turbo, 25psi boost!?!

[gerg]

My pistons are by diesel power parts. It was a kit from RooDogs. The kit is superb. The pistons did have metal inserts around the ring lands. I took that to be a good thing, but I dont know what alloy they are to try and figure out what they can take pressure and heat wise. Sucks.
g

 

[Dougal]

Sounds like you're good to go then. I mean honestly it sounds like they've been well tested already.
IDI pistons can take a lot more heat than DI pistons because their flat top gives the minimum surface area to conduct heat in.

I don't think the pistons are your weak point. But maybe machining a slight dish into the top would lower the compression and make life easier for the head.

Your next problem will be running out of fuel. I suspect you're already at the limits of your pump. Maybe get an Isuzu 4BD1/2 injection pump and see if those pump elements will fit. They'll give at least 60% more fuel.

 

[70sguy]

I've seen guys running single turbos on 3Bs with around 25 lbs of boost... I don't see why the pre-cups would just jump out of their sockets with more boost. It would have to do with more heat, or cracked cups.

Some people seem to think that the air charge comes into the head through the pre-cups, and I don't know where they got that idea from 'cause it's just not true.

Boost, in and of itself is not the demon, it's heat. Heat comes from too much fuel and perhaps the heating of the air charge entering the engine which adds to the overall heat... Generally speaking, increased boost without increased fuel actually cools the engine down. Ie: we set up a 3B turbo the other day - 8 or 9 PSI and it ran at 1000F, go up to 12 PSI and that temp came down to 900F with the same fuel setting.

Keep the EGTs in line, and with good cooling and proper timing, the engine will probably stay together for a surprisingly long time.

~John

Obviously the air charge isn't coming in through the precup, but when the non turbo (higher compression) piston is at TDC a very large chunk of the combustion chamber volume is the space up in the head above the precup, which has a hole the size of my little finger nail. So a pretty good chunk of the intake stroke air volume is getting shoved through that hole one way or another.
I figure it has less to do with heat, cuz a 3B makes ungodly EGTs without turbo, I think it's more to do with the increased pumping stress in and out of the precup that can cause them to drop... but hey, I am no engineer.. well, not that kind anyway.
I have heard of precups dropping on the odd naturally aspirated 3B, but I get calls from a whole bunch more people (looking for engines) who's turbo 3B dropped a precup after boosting over 10 psi.

I don't want all this backyard 3B Thermodynamic theory to take anything away from gerg's twin turbo build, as I mentioned I think it's absolutely brilliant and would love a ride in it but I maintain that 25psi in a 3B IMO is a grenade with the pin pulled

 

[blis]

Obviously the air charge isn't coming in through the precup, but when the non turbo (higher compression) piston is at TDC a very large chunk of the combustion chamber volume is the space up in the head above the precup, which has a hole the size of my little finger nail. So a pretty good chunk of the intake stroke air volume is getting shoved through that hole one way or another.
I figure it has less to do with heat, cuz a 3B makes ungodly EGTs without turbo, I think it's more to do with the increased pumping stress in and out of the precup that can cause them to drop... but hey, I am no engineer.. well, not that kind anyway.
I have heard of precups dropping on the odd naturally aspirated 3B, but I get calls from a whole bunch more people (looking for engines) who's turbo 3B dropped a precup after boosting over 10 psi.

I don't want all this backyard 3B Thermodynamic theory to take anything away from gerg's twin turbo build, as I mentioned I think it's absolutely brilliant and would love a ride in it but I maintain that 25psi in a 3B IMO is a grenade with the pin pulled

I believe the precup droppages and cracks are mostly caused by improper warming/cooling of the engine both naturally aspirated and turboed, the reason for this is that high etg's mean high head temperatures which causes compression on precups until whole head reaches operating temperature...

 

[Radd Cruisers]

My pistons are by diesel power parts. It was a kit from RooDogs. The kit is superb. The pistons did have metal inserts around the ring lands. I took that to be a good thing, but I dont know what alloy they are to try and figure out what they can take pressure and heat wise. Sucks.
g

The pistons you have are Alfin pistons, although the box says they are not for turbocharged applications, it's exactly what they are designed for. The label on the box is about warranty issues - if you're going to run a turbo engine, then they don't want to be replacing your pistons all the time because you're the guy who's pushing 1450F EGTs and a 25 pounds of boost.

Regaring pre-cups - yeah, they fail, but how many engines with 350,000+ kms are getting turbos added to them, and home-tuned to run even more un-godly EGTs than they can run stock?

One of my friends ran his 3B well into the 1400s for extended periods of time (hours, days, weeks) because he didn't know any better and that's just the way things were (HAC unit had come loose and threaded itself all the way back). He runs the bag off his NA 3B and doesn't really worry about much, but his cooling system is in great shape and all and all the peripherals are newer (hoses, W. pump, coolant, rad etc.).

Run it, enjoy it, keep us up to date.

~John

 

[gerg]

Thanks John that is good to know. I got an email reply back from Roodogs and they said they were of the same strength and quality as OE pistons. I havent read of a 3B piston failure.
Thanks
g

 

[gerg]

I just dig up some pics of the pre cups I rounded the edges on and polished and ceramic coated. I wanted to reduce the pumping losses some while not screwing with the swirl.

Edit. You should not ceramic coat precups as it interferes with heat transfer into your air fuel mix. It's a step backward performance and economy wise.
g

 

[gerg]

These are what the old cups looked like yummy...
g

 

[Toyfj45]

Sounds like you're good to go then. I mean honestly it sounds like they've been well tested already.
IDI pistons can take a lot more heat than DI pistons because their flat top gives the minimum surface area to conduct heat in.

I don't think the pistons are your weak point. But maybe machining a slight dish into the top would lower the compression and make life easier for the head.

Your next problem will be running out of fuel. I suspect you're already at the limits of your pump. Maybe get an Isuzu 4BD1/2 injection pump and see if those pump elements will fit. They'll give at least 60% more fuel.

Thats what i am planing for my 2h when it gets a turbo

 

[gerg]

How does that work Dougal? Do you fit the pump or exchange the guts from one pump to the other?
g

 

[Dougal]

How does that work Dougal? Do you fit the pump or exchange the guts from one pump to the other?
g

You could possibly fit the whole pump, but I was thinking just change the barrells and plungers.
I don't know how interchangable they will be, but externally they're all A type bosch/zexel/kiki pumps.

 

[Tapage]

Keep the EGTs in line, and with good cooling and proper timing, the engine will probably stay together for a surprisingly long time.

John I'm complete agree with you .. just don't have any sense push 25PSI of boost without the proper amount of mathing fuel .. and what I found in IDI engines it's you you haven't enough fuel, you probably aren't going to make those 25 PSI of boost ..

. I think that keeping the EGts lower with good inter-cooling and better flowing heads will help alot with the piston strength.

of just plain water alcohol injection would help too ..

 

[gerg]

I did do a fair bit of mathing before building it. In hindsight the smaller turbo has a larger turbine than I would like. The TEo4h has the largest turbine in the TDO4 family and after talking to Mainlander with his TDo4L 13t I think i am going to try a slightly different combo for a few hundred RPM sooner boost. I will do that this fall when I redo my head. It was sort of tuff to guage cus there isnt alot of Mitsu turbos put on 3Bs to get an idea of where they kick in.

Tapage. Boost is the easiest thing to achieve. Boost with acceptable back pressure is not easy to achieve. That being said I have not yet measured my backpressure ... doh!

I found a pick of the piston and I does indeed have the metal insert and can handle some boost... some... heh
g

 

[gerg]

Ohh and I have no idea where 25psi boost came from cus I have Maggie T dialed in for 20 at the moment. Just an fyi for the benevolent force that corrects thread names.
g

 

[Granite Grinder]

Can't you edit your own thread? I thought if you go to the first post, go to thread tools? hit edit you should be able to change the thread name... maybe. I'm pretty sure none of the mod's altered the thread name, but I could be wrong. What name did you give the thread in the beginning?

 

[gerg]

I cant seem to edit the thread name.
The origional name was much more dignified, "Margaret Thatcher naked on a cold day"
g

 

[Granite Grinder]

Aaaah I see, I'm guessing the mods Brownbear or cruiser_guy modified it. Not sure why exactly, maybe something to do with the search function.

 

[Volcano cruiser]

Aaaah I see, I'm guessing the mods Brownbear or cruiser_guy modified it. Not sure why exactly, maybe something to do with the search function.

I'm going to throw in for an image based reason for the title edit. I thought that the original name was catchy and the thread topic was interesting so I signed up. As bad an image as it is , for some, of the Iron Lady naked , the image of her naked, cold and wrinkly, well... I think that just threw them over the top.

I did do a fair bit of mathing before building it. In hindsight the smaller turbo has a larger turbine than I would like. The TEo4h has the largest turbine in the TDO4 family and after talking to Mainlander with his TDo4L 13t I think i am going to try a slightly different combo for a few hundred RPM sooner boost. I will do that this fall when I redo my head. It was sort of tuff to guage cus there isnt alot of Mitsu turbos put on 3Bs to get an idea of where they kick in.

Tapage. Boost is the easiest thing to achieve. Boost with acceptable back pressure is not easy to achieve. That being said I have not yet measured my backpressure ... doh!

I found a pick of the piston and I does indeed have the metal insert and can handle some boost... some... heh
g

G,
What pistons are those? What engine are they designed for? Got a part number for my future reference file.
Thanks,
John

 

[gerg]

They are Alfin pistons for the 3B. I am sorry but I dont know the serial numbers. I dont think they are anything special, just OEM replacement. Im just lucky 3Bs are pretty tuff to begin with.
g

 

[mudstorm]

any updates on the project
how does it sound how does it go
that turbo setup is ..sex
im impressed