Twins with Twins, Anyone?

[SmokeShow]

What's the target life expectancy of these engines? Like how often will it be planned to need a rebuild (rehone, bearings, yada yada yada)? A set hour schedule or based on routine oil analyses or what?

Was any of the oil sent out for analysis post-dyno session(s)?

 

[kidturbo]

Looks like you might want to open up the ring gap a little. I never liked the coatings on a gas motor or otherwise. Isn't performance motors so fun. lol

Since I have two to work on, I'm gonna drop the second engine off to you on the way home next week. You've done a couple race engine rebuilds before I hear.. :rofl:

I actually wanted to see the gap lines on that one since it pushed the needle 200hp higher than this engine. And EGT was good bit hotter also. In all the logs we measured CCP, and this one was running about 0.4psi max. Other engine CCP reached 1.0psi on the big turbo tune.

Starting to recall why I retired the wrenches and got into IT back at age 30...

 

[kidturbo]

What's the target life expectancy of these engines? Like how often will it be planned to need a rebuild (rehone, bearings, yada yada yada)? A set hour schedule or based on routine oil analyses or what?

Was any of the oil sent out for analysis post-dyno session(s)?

Goal for this setup has always been make 900hp reliably with 1000hr rebuild schedule. To many of you that might sound like your average daily driver. But remember, you have a 12k lb sled hooked to ya all the time...

I have oil samples from this engine in some jars on the bench. Have a little centrifuge setup from my biodiesel days, and was gonna spin out some just to check the metal content. Being it's from a break in period, figured a complete oil analysis be kinda useless. But hey, guess now I can just check all the bearings while in here.. :whisle:

 

[Chevy1925]

Goal for this setup has always been make 900hp reliably with 1000hr rebuild schedule. To many of you that might sound like your average daily driver. But remember, you have a 12k lb sled hooked to ya all the time...

I have oil samples from this engine in some jars on the bench. Have a little centrifuge setup from my biodiesel days, and was gonna spin out some just to check the metal content. Being it's from a break in period, figured a complete oil analysis be kinda useless. But hey, guess now I can just check all the bearings while in here.. :whisle:

what kind of duty cycle at 900hp?

since mines been built, its only seen that or more load behind it but the duty cycle would be lower till i hit the hills. its go about 750hr on it at this point. realisitcally i was setting a goal of hitting 50k on the engine before something major would need addressing, at 40k the heads came off for the lly top end and things looked great. at 58k on it at this point (wow, didnt realize im up that high!) with id say about 85% towing 12k or more behind the truck, 5% with a flat bed behind it hauling something, and rest daily driving spiritedly with a few WOT runs a few times a week. id probably say my duty cycle is probably 25% at 600hp over the 58k miles. I would assume you are looking at a much higher duty cycle though which id really like to see if they last! that would be cool!

 

[kidturbo]

The 750hp Cummins version out there went through a 80% WOT duty cycle for 24hrs on dyno before release. But that is on a Monotherm piston engine under strict military specs. And I've heard mixed reviews on it's performance depending on who ya ask..

So we are just throwing darts blindfolded at the moment, as second engine started spitting coolant out over 900hp.. This first engine looked great in the 600-700hp range, and at part throttle seemed happy enough to run there forever. Why we felt everything was good enough to move into stage 2, real world testing with a little bigger injectors.

I seriously don't see these running WOT for long periods of time due to boat speed that comes with it. More likely they will run between 2100r and 3000r or 40-60% throttle most of the time. That's from my own experience. Then they may be pushed WOT for short 2-3 minute 100mph blasts. So they have to be able to take that abuse either way.

 

[Chevy1925]

ah 10-4

 

[Fingers]

I have little to no experience with the TCB coating. All Gold coat. I have never seen Gold after it left my shop and have not seen any failure personally. I'll drop a call to Swain on Monday. IIRC Dirty Hooker coated a lot with Gold. Wonder what they have seen.

One issue with the cast is they are susceptible to water pitting, and this looks similar, but doesn't make sense to me. I think that the pistons should have some sort of coating in this application to, if nothing else, help with the water pitting issue. However, if it doesn't stick.....

 

[kidturbo]

Thanks for the help Jon. I really thought this TBC would give us the added protection needed for extended high temp operation.

Recall when I spoke with Swain about the two coating options, this was the best compound for long term heat dissipation. The gold is geared more towards absorbing a thermal shock of nitrous, and wasn't recommended coating for this build.

As for your water question, it's entirely possible some condensation from the charge cooler blows through the cylinders on the decel, when charge air is still hot but boost it off. Mark and I witnessed those exhaust manifolds make enough water at idle to fool us into thinking we had a leak. We even looked into the intake to be certain the charge cooler wasn't leaking. That side was dry. But this issue only showed up on second engine when the seawater temp was sub 40F, and cleared once we got some big heat in the systems. So yes the pistons are likely to see some moisture.

 

[kidturbo]

Popped the other head off, and more of the same. However a strange coincidence, cylinder #1 which had a pressure probe in it rather than a glow plug delete stick, and a EGT probe in the exhaust port, has the least amount of coating damage. Go figure..

The lifted coating patterns appear very random, and show no specific pattern across any two pistons. If water intrusion started the issue, one might expect to see a pattern around the valves or such. Doesn't appear to be so.

Next, pull the pistons and inspect the other surfaces..

 

[2004LB7]

I say hit it with some high temp BBQ paint. That should do it :nanawrench:

 

[Fingers]

I have not noticed any pattern to the water pitting on the pistons. And to be clear, I think it is water intrusion based on the pistons that I have seen.

That last set of pictures shows clearly that the coating is bubbling and peeling. An adhesion issue. Chance there is a contaminate in the metal that is coming out under load.

 

[kidturbo]

I have not noticed any pattern to the water pitting on the pistons. And to be clear, I think it is water intrusion based on the pistons that I have seen.

Looks something like the examples below?? Made me dig up pics from 2010. My first cracked Duramax pistons.. Ah the memories... :hug:

Back then I thought it was just due to 1800F EGT for extended periods. But if you look closely at the cylinder wall you can see the etching of a water line where it laid in there.

That's from my LLY in the OG PPE boat. I first wrote if off to being a junkyard motor, but we later learned this was from charge cooler condensation drain back after shutdown. We replaced those with a first off the press Mahle race cast set, polished bowl. Also relocated the charge cooler to stop it from happening.

This Banks intake uses an upflow design, so any condensation on shutdwon drains into the turbo feed rather than down the intake runners. However we also have to take into account reverb on the exhaust sucking condensation from the manifolds back into the cylinders at idle..

 

[kidturbo]

I say hit it with some high temp BBQ paint. That should do it :nanawrench:

I was thinking header paint, but.... :beer

 

[Fingers]

The failures of the pistons are because of an unrecognized stress. I don't think the pitting has any effect on the longevity of them. Though I have seen them eroded down significantly.

 

[kidturbo]

I concur. My failures were unrelated to the pitting. Sure looks nasty however.

So what's your thoughts on polishing the tops?

 

[Fingers]

Polished or rough, same result as far as pitting.

 

[2004LB7]

What about nickel plating it, or hard chrome?

 

[Fingers]

Adhesion is always the issue. Especially with high silica alloys.

In the case of the coating failure you have seen. There appears to be something bubbling up from underneath. Might have to vacuum bake them prior to coating to remove impurities.

 

[kidturbo]

Anyway to test these adhesion theories outside my customers two very expensive engines?

I'll have the second engine back home Tuesday. While it has less run time, we know it saw higher heat and cyl pressure than this one. Should be interesting to compare since all 16 pistons are from same bake.

 

[2004LB7]

The only one I'm familiar with that may work is ASTM D3359. But I dont think it would work for that coating, being fairly soft