(Engine experts needed) Chirp, Vibe, Pop (What is Wrong?)

[k-huevo]

Would it manifest while not using the SC?

Possibly a misfire code and somewhat rough idle.
A borescope would allow you to have a look at the combustion chambers.
I recommend compression and leak-down tests.
After viewing the video, I think the belt should be 5mm shorter (or larger SC pulley), and I suggest replacing the crankshaft vibration damper/harmonic balancer.

 

[mrblaine]

After viewing the video, I think the belt should be 5mm shorter (or larger SC pulley), and I suggest replacing the crankshaft vibration damper.

I don't disagree but I've played that game and it is almost impossible to get that belt on. It is all you can do with all the slack out and the tensioner cranked back to just get the one on he is using. If one of the other idlers is in a slot and there is room to move it to the slack side, that may do it, other than that, not easy at all.

 

[k-huevo]

Have you tried pushing the belt over two idler pulleys at the same time?

 

[toximus]

I have some time while the thing ships. I might just pull the head. I have everything for it and it's already half way apart. And then I can know for sure and don't have to bother with removing the SC again.

I think the belt should be 5mm shorter (or larger SC pulley)

A larger SC pulley would create less boost than I'd like.

If you can find me a belt 5mm shorter I'll see about getting it on. Currently using a Gates 1177.

While it's out I'm going to drill a few more holes in the brace to have more idler options. Also if I replace the head gasket I can run a smaller SC pulley and have better clearance against the water pump and get it down a belt size to the 1159.

 

[toximus]

Here's what I have:

 

[Apparition]

I have some time while the thing ships. I might just pull the head. I have everything for it and it's already half way apart. And then I can know for sure and don't have to bother with removing the SC again.



A larger SC pulley would create less boost than I'd like.

If you can find me a belt 5mm shorter I'll see about getting it on. Currently using a Gates 1177.

While it's out I'm going to drill a few more holes in the brace to have more idler options. Also if I replace the head gasket I can run a smaller SC pulley and have better clearance against the water pump and get it down a belt size to the 1159.

Do you have these? Might be the time if you pull the head.

https://www.boostedtech.com/superchargers/accessories/engine/jeep-4-0-arp-head-bolt-kit-1987-2006/
@Chris why does my link say stackpath?

 

[toximus]

Do you have these? Might be the time if you pull the head.

https://www.boostedtech.com/superchargers/accessories/engine/jeep-4-0-arp-head-bolt-kit-1987-2006/
@Chris why does my link say stackpath?

I have the MLS head gasket and Felpro head bolts which allow the stock wiring cover to be retained (supposedly good to at least 14psi). And roller rockers I can put in which will increase volume and lower psi. Beyond that, because I already have it, I'm done spending money on upgrading the incline 6.

 

[toximus]

I've seemingly gone full circle again and it hasn't gotten any smarter.

—-

I got a call back from BoostedTech and they don't see anything wrong with the supercharger. After I specifically told him to rotate the rotors and look at the damage (pictured in previous posts) he said that he did see one little divot that isn't a problem and can be filed off.

He said that he can't feel any issues rotating it by hand and in fact it feels like one of the best units they've had.

He isn't going to open it, and is not able to test it on an engine under the conditions the issue happens under, he is not sure that the rotors are or are not deflecting under load because he can not test it, he has no further diagnoses to do. In his conclusion there is nothing wrong with the supercharger and is ready to send it back.

He said that the issue is probably a vacuum leak in the engine intake (around the TB) or exhaust. There are no leaks that can be found in a shop on my engine. He did not know how to test these with the engine running under the conditions that the issue occurs.

—-

It seems that my options are still a bad supercharger, bad engine, or bad transmission and the only way to feasibly test them is to either 1) throw parts at the problem and fully rebuild each, or 2) swap around different supercharger, engine, transmission combos until I narrow down which is the problem. Both of these are incredibly expensive and time consuming ways to deal with the problem.

Any ideas?

 

[BuildBreakRepeat]

I've seemingly gone full circle again and it hasn't gotten any smarter.

—-

I got a call back from BoostedTech and they don't see anything wrong with the supercharger. After I specifically told him to rotate the rotors and look at the damage (pictured in previous posts) he said that he did see one little divot that isn't a problem and can be filed off.

He said that he can't feel any issues rotating it by hand and in fact it feels like one of the best units they've had.

He isn't going to open it, and is not able to test it on an engine under the conditions the issue happens under, he is not sure that the rotors are or are not deflecting under load because he can not test it, he has no further diagnoses to do. In his conclusion there is nothing wrong with the supercharger and is ready to send it back.

He said that the issue is probably a vacuum leak in the engine intake (around the TB) or exhaust. There are no leaks that can be found in a shop on my engine. He did not know how to test these with the engine running under the conditions that the issue occurs.

—-

It seems that my options are still a bad supercharger, bad engine, or bad transmission and the only way to feasibly test them is to either 1) throw parts at the problem and fully rebuild each, or 2) swap around different supercharger, engine, transmission combos until I narrow down which is the problem. Both of these are incredibly expensive and time consuming ways to deal with the problem.

Any ideas?

I assume you’ve already smoke tested your engine for any leaks?

 

[toximus]

I assume you’ve already smoke tested your engine for any leaks?

Yes. But not while driving up a hill at 50mph, under 6psi of boost, while in OD.

 

[toximus]

I looked back through this thread. I forgot to mention that the belt squirter I had rigged up seemed to quiet the chip (there's not enough fluid to squirt until the vibes would start).

So it's possible that the chirp sound is coming from the belt as a result of something else making the belt slip (almost like something in the SC is causing the oscillation we're seeing which makes the belt chirp as it catches and slips.).

 

[Daryl]

I've seemingly gone full circle again and it hasn't gotten any smarter.

—-

I got a call back from BoostedTech and they don't see anything wrong with the supercharger. After I specifically told him to rotate the rotors and look at the damage (pictured in previous posts) he said that he did see one little divot that isn't a problem and can be filed off.

He said that he can't feel any issues rotating it by hand and in fact it feels like one of the best units they've had.

He isn't going to open it, and is not able to test it on an engine under the conditions the issue happens under, he is not sure that the rotors are or are not deflecting under load because he can not test it, he has no further diagnoses to do. In his conclusion there is nothing wrong with the supercharger and is ready to send it back.

He said that the issue is probably a vacuum leak in the engine intake (around the TB) or exhaust. There are no leaks that can be found in a shop on my engine. He did not know how to test these with the engine running under the conditions that the issue occurs.

—-

It seems that my options are still a bad supercharger, bad engine, or bad transmission and the only way to feasibly test them is to either 1) throw parts at the problem and fully rebuild each, or 2) swap around different supercharger, engine, transmission combos until I narrow down which is the problem. Both of these are incredibly expensive and time consuming ways to deal with the problem.

Any ideas?

I’ve rebuilt a few Detroit Diesel blowers and I can tell you that your blower needs disassembled and inspected and clearances checked. At a minimum you need to remove the rotors from the housing and use a wet stone to remove the nicks and burrs. The inner housing surface needs inspected for the same. And the drive needs disassembled and inspected. BoostedTech is being lazy IMHO. You can do it yourself. They’re simple to work on. Buy the Eaton service manual if you decide to take this route.

 

[toximus]

I’ve rebuilt a few Detroit Diesel blowers and I can tell you that your blower needs disassembled and inspected and clearances checked. At a minimum you need to remove the rotors from the housing and use a wet stone to remove the nicks and burrs. The inner housing surface needs inspected for the same. And the drive needs disassembled and inspected. BoostedTech is being lazy IMHO. You can do it yourself. They’re simple to work on. Buy the Eaton service manual if you decide to take this route.

I don't think you're wrong.

 

[AndrewLJR]

Im not experienced in the rebuild/required care for the blower itself but Im sticking to my original suggestion and get a proper retune done to get your AFRs in check. Now, someone more knowledgable Im sure will chime in on whether the blower could be making those chirps but Id get step 1 fixed before replacing the blower. Or if a rebuild is in your realm, do that and retune.

 

[Daryl]

Im not experienced in the rebuild/required care for the blower itself but Im sticking to my original suggestion and get a proper retune done to get your AFRs in check. Now, someone more knowledgable Im sure will chime in on whether the blower could be making those chirps but Id get step 1 fixed before replacing the blower. Or if a rebuild is in your realm, do that and retune.

Until the blower is confirmed to be within tolerance, I’m one to believe the chirp is the belt slipping because the blower is too resistant to spin at the rpm that it’s set up for.

 

[toximus]

I have a phone call scheduled for 7pm tonight with someone who's very familiar with mounting these Eatons on the Jeep engines. I'm hoping his experience will cast some light on what's happening and give me a better idea of how to proceed.

 

[scottgraham]

Any ideas?

Sell the whole thing back to @Chris ?
He needs something to keep him busy.

 

[toximus]

I have a phone call scheduled for 7pm tonight with someone who's very familiar with mounting these Eatons on the Jeep engines. I'm hoping his experience will cast some light on what's happening and give me a better idea of how to proceed.

I had the phone call and he thought it was strange and showed the videos to his son. Neither knew for certain what the issue is. He said that 99% of "supercharger problems" are not the supercharger but something else that would also show up when the supercharger is bypassed.

After going through everything we've already discussed and tried in this thread, he said that there's nothing else he could think of trying and felt that putting the engine and accessories under load with or without boost should cause the issue to present itself since the bypassed SC only takes a few HP to spin.

He recommended replacing in the SC the front bearing, front seal, and front coupler. Although he wasn't sure how if they were bad how those things would still allow the SC to turn easily by hand.

He said it could be a bad rod bearing in the engine.

 

[toximus]

Talking to Mark at BT about that again, he said that the SC is not the problem whatsoever because he can turn the SC by hand and not feel anything and he does not need to open it up to know that there's not a problem inside. According to BT there is no possible way that the SC is the problem.

He told me to pressurize the intake on the 4.0L to 14psi and listen for leaks. Then run the engine and put my hand over the tailpipe to listen for leaks before the AFR sensor. He does not know why the leak can happen at 1psi but not at 8psi.

 

[k-huevo]

...run the engine and put my hand over the tailpipe to listen for leaks...

That is a bad suggestion.
Have you replaced the crankshaft harmonic balancer?