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Discussion Starter #1
Good afternoon,

I was talking with another member the other day and apparently there has been word of issues with the main bearings and F/I.

Has anyone heard of someone spinning a main bearing due to F/I? Has anyone done it themselves. From what I heard, it tends to happen at 9psi and above. So I would guess about 400-450 rwhp.

Also, I heard this issue would be more of a concern for those tracking and streeting their car and not necessarily those dragging. Considering there are no stronger aftermarket main bearings (that I know of), we would either have to stay stock or borrow a stronger main bearing from another engine and make it fit the VQ35DE.

Just curious if anyone knows more. Take care.
 

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Yep, Tere from ZChickz (owner and Z goddezz of ZChickz I should say) spun her main bearing...........here's the thread........VQ35DE engine rebuild thread on ZChickz

COURTESY OF ZCHICKZ
Page 4 of post
Posted - 12/13/2004 : 7:45:54 PM
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If anyone cares to see the result of a spun main bearing in the engine here they are. They should not have the grooves you see in them. I'm still surprised that I didn't hear any odd engine noises -- I would have expected to hear a rattle or grind with a spun main bearing.

Crankshaft



 

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Discussion Starter #3
Thanks Jinxxy!

I did a little more reading on bearings in general and learned a lot. If you don't know much about them, head over to http://images.google.com (yes, images) and search for rod bearing. You will get a bunch of images. Any image that looks like a rod will take you to a page about engine rebuilds. Man, there are a million things that can happen to a bearing.

Anyone know of an aftermarket bearing that can take the torque? Bearings are cheap so we simply need a good aftermarket on for F/I and we can put this issue to bed. If you are going to crack open the engine for forged rods and pistons, you might as well put in some good $40 bearings.
 

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Originally posted by jinxxycat@Jan 14 2005, 01:19 PM
I'm still surprised that I didn't hear any odd engine noises -- I would have expected to hear a rattle or grind with a spun main bearing.


Oh, just let it go on for a minute & you'll hear all kinds of racket....esp that nok-nok-nok (not Curly Joe!). The grooves are just the start, once the soft bearing material (nickel alloy) wears through to the bearing shell, the crank grabs...jetissoning rods through the crankcase, etc.

:soapbox: These F/I kits are set at certain pressures for a reason....& if all requirements for the kit: colder plugs, timing, fuel, etc. are not met, you might spin a bearing at 5 psi!

F/I mods can't be done halfway, or you're sure to lose your motor. Do your homework. Do the math. If you don't think you're up for it, you probably aren't. :thumbsup:
 

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Originally posted by peptidbond@Jan 14 2005, 12:28 PM
Good afternoon,

I was talking with another member the other day and apparently there has been word of issues with the main bearings and F/I.

Has anyone heard of someone spinning a main bearing due to F/I? Has anyone done it themselves. From what I heard, it tends to happen at 9psi and above. So I would guess about 400-450 rwhp.

Also, I heard this issue would be more of a concern for those tracking and streeting their car and not necessarily those dragging. Considering there are no stronger aftermarket main bearings (that I know of), we would either have to stay stock or borrow a stronger main bearing from another engine and make it fit the VQ35DE.

Just curious if anyone knows more. Take care.

For those concerned about spinning a bearing you could maybe think about going with a little more clearance on the crank (thinner bearing). That puts a little more oil between the bearing and the crank and decreases the chances of the oil barrier between the bearing and crank breaking down. The only real downside to this is lower oil pressure in the motor. This is easy to do with the huge number of bearings available from Nissan.
 

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Spinning a main or rod bearing and usually NOT the result of power or torq. They are usuallly the result of oil starvation, or excessive and sustained high RPM operation. That is what happened in the case of ZChicks...IIRC.

Excessive detonation can also beat the bearings to pieces, but with good tuning, and normal driving, and ocassional tracking, I doubt you'll see too many spun bearings.

To my knowledge, and I did some checking on this for my build-up, nobody is making bearings for the VQ yet....correct me if I am wrong. You can also try to have them ceramic coated...which might help a little bit.

Otherwise, use the stock bearings, make sure the grade of bearing is correct...and that they MEASURE.....some shops dont. :) Keep the revs under 7000rpm and just have fun! :)
 

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.

To my knowledge, and I did some checking on this for my build-up, nobody is making bearings for the VQ yet....correct me if I am wrong. You can also try to have them ceramic coated...which might help a little bit.


Nismo Japan have bearings & a upgraded oil pump for the VQ350 motor

Oil Pump part # 15010-RRZ30
Main Brg Pt # 12110-RRV50
Big End Pt # 12207_RRV50
 

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.

To my knowledge, and I did some checking on this for my build-up, nobody is making bearings for the VQ yet....correct me if I am wrong. You can also try to have them ceramic coated...which might help a little bit.


Nismo Japan have bearings & a upgraded oil pump for the VQ350 motor

Oil Pump part # 15010-RRZ30
Main Brg Pt # 12110-RRV50
Big End Pt # 12207_RRV50
<div align="right">[snapback]70541[/snapback]

Cool. but if the pricing on the Nismo bearings is anything like the Nismo oil pump....get ready for sticker shock. :) The Nismo oil pump is $1000.
 

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pump....get ready for sticker shock. :) The Nismo oil pump is $1000.
<div align="right">[snapback]70611[/snapback]
[/quote]


It would be interesting to check out the price of the oil pump on the new Track motor.
I believe it is a new pump as it now has to supply extra oil to the exhaust cam phaser solinoids & vtc sprockets
 

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Can I spin a bearing with Nitrous? I rarelu use it and never ever go above 6,500 RPM and that is a rarity. Is this a safe operation technique? Would that be ok to not hurt the motor? Also I never go above the 35 shoot. Yeah I know, thats lame. :shiftdrive:
 

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Discussion Starter #13
[/quote]
Your fine. With the power you are producing, you are not likely to detonate in such a way as to damage a bearing. Furthermore, I doubt you will see issue with oil starvation.

That being said, preventive medicine is best. If you are going to pull hard at the track, make sure you have a full dose of clean oil. This will help to reduce any starvation issues or loss of the oil film protecting the bearings.

As a side note to others, why aren't more people using oil sumps? They are cheap and much more effective than a deeper oil pan/oil pan spacer? After all, the Performance Nissan GrandAm racing team uses them.

If you don't know what a sump is, here are the basics:
1. Spend about $400 for a sump and the electronic valves need.
2. If gets installed in your oil lines and is filled with oil and then charged with presssure.
3. Just before you start the car, you trip the electronic valve and the high pressure oil rushes into the engine. It temporarily fill all the bearings, journals, etc.
4. Start the car.
5. The oil pressure generate by the car will refill the sump. As you drive, if oil pressure is lost due to an unsubmerged pickup, the sump will begin to bleed out pressure and save the engine. Once oil pressure is returned, the sump fills again for the next need.
6. Before you shut off the car, close the electronic valve and store some pressured oil in the sump. That way, it is always ready for next use.

You know how they say start up is the worst time for an engine? A sump totally fixes that. Also, under really hard acceleration (forward or lateral) it can save your ass if the pick-up comes unsubmerged.
 

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The main benifit of dry sumping is improved oil flow and reduced risk of oil starvation due to high g's load...such as continous racking on a track. I dont know exactly how a dry sump would be executed on a 350Z, which is probably why nobody has tried it just yet. In my opinion, unless you are almost exclusively racing the car on a track, a dry sump system has limited applications for normal street or strip usage, and is pretty expensive to purchase and install.

Anyone else have experience with dry sumps on the 350Z?
 

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Sustained high rpm - you will always be at the track or would have to drive like a lunatic on the road all the time for bearing damage, but that is not to say it can't happen, just need all the wrong things to happen at the right time!

Dry sump might be a good insurance but cost prohibitive for most.

Check your oil if tracking or driving like a luny all the time!
 

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Nissan from the factory, builds their engines with VERY tight tolerances. What I had my engine builder do was to chose crank bearings that have clearances at the larger end of the specification scale. That larger clearances will allow for more oil, and better reliability for a super high HP engine. Just something to think about. They are still within spec..but just at the larger end.
 

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Discussion Starter #17
[/quote]
I think you misunderstood what I was suggesting. I am not speaking of a dry sump (dry oil pan). I am speaking of a wet pan, but with the added insurance of an emergency sump (check out www.accusump.com for more detailed info and images). I know of basically two manufacturers: Canton Racing (Accusump) and Moroso. Basically, you add a bottle to the oil lines that has a piston in it. You fill the bottle with the correct amount of extra oil and then charge it to 80PSI the first time. Then start the car. The oil pressure in the engine comes up and you release the valve on the bottle. Now, the bottle pressure matches the engine pressure always and you still have the correct amount of oil in the engine and the pan. As you drive, if the oil pressure drops, emergency oil stored in the bottle comes rushing out to fill all the oil channels, bearings and galleries. When oil pressure is restored, it pushes pil back into the bottle.

Once charged an installed, you don't have to fool with the bottle. You don't need to charge it with air everytime. Also, you can get a valve for the bottle this has a solenoid. You just throw a switch and it opens. Close the switch and the valve closes. Open the bottle right before start up (to prelube the engine) and shut it off right before shutdown. This keeps the bottle constantly under pressure and filled with oil. It is a great way to defend against momentary oil pressure loss to to high G's and to reduce wear on startup.

The only down side: you have to use an extra 1.5 quarts everytime you change the oil. That is it. Oh, and a complete setup with the bottle, necessary connectors, a check valve for use with a oil cooler, and the electronic/solenoid valve is about $500 (much cheaper than a dry sump.

By the way, the Performance Nissan GrandAm team uses Accusumps. I talked to their engine builder at Mid-Ohio in August. He seemed to swear by them.
 

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I went to their web site and the concept seems good, but.......wouldn't such a device cause serious fluctuations in the oil level in the crankcase?
 

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Discussion Starter #19
Potentially, yes. Let me use an example:

You are on the track, lets say Mid-Ohio, and you enter the Carosel. It is a 270 degree turn and you pull a lot of G's. The oil may rush to one side of the pan and crank, away from the oil pickup. So, pressure drops to a dangerous level as the pickup becomes uncovered.

Now, as the pressure drops, the accusump releases oil pressure into a hose that connects to the "inlet" side of the filter. It is then pushed into the main galleries and other area, not directly into the crank case. Eventually, it will fall back to the pan.

However, I think that pressure would be restored before a truly excessive amount of oil builds up in the pan. As pressure is restored, the bottle refills and the crank may only see a momentary rise in oil volume, if any at all.

Plus, excess oil in the crank is not a huge issue. Certainly less so than running an engine on low oil pressure. A larger concern would be way overfilling the crank and leaving it there, instead of storing it in an accusump.

If one is truly concerned about the oil level in the crank case when using an accusump, you can always add a JWT oil pan spacer. This would drop the oil level in the crank lower, away from the crank itself. Even if the accusump released oil, it would not be an issue.
 

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I used a Moroso Accusump on a fully built '78 Camaro over 20 years ago and the thing saved my A**
I originally installed it due to an extended high rpm oil starvation issue. (oil flow control/management is a big deal on these engines)

By wiring a low pressure ignition kill into the pressure reservoir on the accusump and setting it at under 2 pounds it kills the engine when pressure is completely lost and is not coming back. In my case it was a busted oil pump drive rod from the distributor.

Momentary losses of oil pressure just cause the reservoir to dump oil but the pump wil then begin to pickup again and refill the reservoir before it drops low enought to trip the low pressure switch.
 
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