Jump to content
SAU Community

Recommended Posts

Sorry for the stupid post but just confirming, i have just done a plastigauge on my new assembly using Acl race series bearings HX type with extra oil clearance.

I have dont some measuring with dry bearings, and got roughly 0.063mm across the board + or - a little on some bearings but all are falling slightly less then 0.063mm on mains.

I am going to be reving the engine hard to 8400rpm occasionally .

I wanted to know if this is a ok bearing clearance using a tomei pump and uprated baffled sump running 8 litres of oil.

I know most run 0.050mm for a hard reving motor, but just wanted to confirm is this is ok on a new build ?

If i go for acl series standard bearings the clearance will for 1" of a inch less so around 0.045mm

What do you recommend and what are your thoughts on this ?

Cheers for the help in advance, ps i will message any one that has asked about the 1280 usd block from states soon, just need to dig up details as i have changed computers.

My apologies.

That works out at 2.5 thou basically, thats exactly what i run in my 25 running a tomei pump, ill be pulling similar revs once tuned. Be sure to run a thick oil. I run redline 15w/50

BTW mine was blueprinted, id suggest that for big output

The number is fine but the clearance doesn't look right for what you would expect from a HX bearing. They are 0.001" extra clearance. I would have thought you'd see a clearance of 0.076mm (0.003") at least on a HX bearing from mid tolerance crank etc.

Why is it tight?

Thanks for the responses .

The crank grading was something like bbbbbb and 0000000 if im not mistaken the B's at the top and the 0's at the bottom .

But you have to remember this is a new crank .

Most build threads have listed a medium clearance of 0.050mm and this seems to be the norm even for the tomei genesis engine .

But on mine seems like its gone even bigger .

I plastigauged all of the mains and thats the clearance we got across the board .

thanks for the reassuring posts.

Now for something very different .

Got new rings and new pistons, tested ring gaps in the new block, and keep in mind rings are new from Nissan Jp.

Top clearance was 0.45 mm

second ring was 0.35 mm

Second ring falls in the larger end of the specs from the Gtr33 rebuild manual but the top ring is over the max allowed specs ?

Why would this be on a new set of Nur piston rings, do you think maybe nissan decided they would change the clearances because it was too small ?

Just seems weird?

It is weird.

As I said earlier, it's not the measurements we would normally see with that combination. New crankshaft with HX bearings I would expect to see 0.003" clearance, not 0.0024"

As for rings, you should definitely consider a larger gap for the second ring.

I understand the manual says certain things and yes, the clearance of 0.0024" on these engines is perfectly fine. What I am getting at is that it's not consistent with what I'm used to seeing (and yes I have used many new cranks and blocks before)

There are still certain general rules that should be adhered to when building your engine. One of them is second ring gap should be larger than top ring gap

ACL have a pretty wide tolerance. ive measurerd them to vary almost 1/2 a thou. 1.5-2.5 thou is aok. any loser it will be lazy to raise oil pressure/ any tigher it will have to much pressure/and/or ware out under high power.

inherently thats what i have 0.0024" or 0.063 mm

across all the mains and i would expect it is a loose fit but having a tomei oil pump will help as the stock rev limit is 8400rpm.

On a second note the ring gaps ....

Top ring Chrome ring has a clearance of 0.50mm

Second ring has a clearance of 0.45mm measured again .

8

sorry im new to the terms and measurements please forgive any errors as measuring and using .00's is never been what im used as i dont work with engine everyday or measuring tools lol.

thanks for the input

sorry this post above is going off memory for the clearances i need to check with the paper i wrote on and make sure i have the right readings please hold fire on ring gaps let me get the actual readings and will post them up as far as i know the second ring gap falls in the tolerances but the top one is too wide and doesnt even meet the max ring gap ....listed in the manual .

having the big pump wll compensate for the looser fit.

2nd ring should have more gap than the top.or it will breath heaps at high revs.

Can you explain why it will breathe heavier with a tighter second ring gap?

All the race engines I know of run a tighter second ring gap and our ring manufacturer strictly recommends a tighter second ring gap, about 0.002" per inch tighter then the top ring. These engines dont suffer from any breathing issues and all have less then 2% leakdown. These engines typically run between 8.5k - 9.5k rpm also.

I was taught running a looser second ring would encourage it to breathe heavier as you are letting the bypassing pressure get into the crankcase easier. The other reason why you dont need a looser second ring is it doesnt run as hot as the top and because of this it doesnt grow as much.

Thats what I was taught anyway and is my 2 cents.

ok as of yesterday i have confirmed weird results but this is how it goes.

Across the board all 6 cylinders are 0.45mm on the top ring <======= TOP RING

Across all 6 second ring is 0.45mm <===== SECOND RING

And these are new rings going into a new block ??? i dont understand how come they are so big ? has nissan decided to make the gaps bigger ?

So that you dont run the small gaps on a small bore ?

I dont get it ?

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • First up, I wouldn't use PID straight up for boost control. There's also other control techniques that can be implemented. And as I said, and you keep missing the point. It's not the ONE thing, it's the wrapping it up together with everything else in the one system that starts to unravel the problem. It's why there are people who can work in a certain field as a generalist, IE a IT person, and then there are specialists. IE, an SQL database specialist. Sure the IT person can build and run a database, and it'll work, however theyll likely never be as good as a specialist.   So, as said, it's not as simple as you're thinking. And yes, there's a limit to the number of everything's in MCUs, and they run out far to freaking fast when you're designing a complex system, which means you have to make compromises. Add to that, you'll have a limited team working on it, so fixing / tweaking some features means some features are a higher priority than others. Add to that, someone might fix a problem around a certain unrelated feature, and that change due to other complexities in the system design, can now cause a new, unforseen bug in something else.   The whole thing is, as said, sometimes split systems can work as good, and if not better. Plus when there's no need to spend $4k on an all in one solution, to meet the needs of a $200 system, maybe don't just spout off things others have said / you've read. There's a lot of misinformation on the internet, including in translated service manuals, and data sheets. Going and doing, so that you know, is better than stating something you read. Stating something that has been read, is about as useful as an engineering graduate, as all they know is what they've read. And trust me, nearly every engineering graduate is useless in the real world. And add to that, if you don't know this stuff, and just have an opinion, maybe accept what people with experience are telling you as information, and don't keep reciting the exact same thing over and over in response.
    • How complicated is PID boost control? To me it really doesn't seem that difficult. I'm not disputing the core assertion (specialization can be better than general purpose solutions), I'm just saying we're 30+ years removed from the days when transistor budgets were in the thousands and we had to hem and haw about whether there's enough ECC DRAM or enough clock cycles or the interrupt handler can respond fast enough to handle another task. I really struggle to see how a Greddy Profec or an HKS EVC7 or whatever else is somehow a far superior solution to what you get in a Haltech Nexus/Elite ECU. I don't see OEMs spending time on dedicated boost control modules in any car I've ever touched. Is there value to separating out a motor controller or engine controller vs an infotainment module? Of course, those are two completely different tasks with highly divergent requirements. The reason why I cite data sheets, service manuals, etc is because as you have clearly suggested I don't know what I'm doing, can't learn how to do anything correctly, and have never actually done anything myself. So when I do offer advice to people I like to use sources that are not just based off of taking my word for it and can be independently verified by others so it's not just my misinterpretation of a primary source.
    • That's awesome, well done! Love all these older Datsun / Nissans so rare now
    • As I said, there's trade offs to jamming EVERYTHING in. Timing, resources etc, being the huge ones. Calling out the factory ECU has nothing to do with it, as it doesn't do any form of fancy boost control. It's all open loop boost control. You mention the Haltech Nexus, that's effectively two separate devices jammed into one box. What you quote about it, is proof for that. So now you've lost flexibility as a product too...   A product designed to do one thing really well, will always beat other products doing multiple things. Also, I wouldn't knock COTS stuff, you'd be surprised how many things are using it, that you're probably totally in love with As for the SpaceX comment that we're working directly with them, it's about the type of stuff we're doing. We're doing design work, and breaking world firsts. If you can't understand that I have real world hands on experience, including in very modern tech, and actually understand this stuff, then to avoid useless debates where you just won't accept fact and experience, from here on, it seems you'd be be happy I (and possibly anyone with knowledge really) not reply to your questions, or input, no matter how much help you could be given to help you, or let you learn. It seems you're happy reading your data sheets, factory service manuals, and only want people to reinforce your thoughts and points of view. 
    • I don't really understand because clearly it's possible. The factory ECU is running on like a 4 MHz 16-bit processor. Modern GDI ECUs have like 200 MHz superscalar cores with floating point units too. The Haltech Nexus has two 240 MHz CPU cores. The Elite 2500 is a single 80 MHz core. Surely 20x the compute means adding some PID boost control logic isn't that complicated. I'm not saying clock speed is everything, but the requirements to add boost control to a port injection 6 cylinder ECU are really not that difficult. More I/O, more interrupt handlers, more working memory, etc isn't that crazy to figure out. SpaceX if anything shows just how far you can get arguably doing things the "wrong" way, ie x86 COTS running C++ on Linux. That is about as far away from the "correct" architecture as it gets for a real time system, but it works anyways. 
×
×
  • Create New...