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 Post subject: Re: Our little cultus racer
PostPosted: Mon Jun 03, 2019 4:51 pm 
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Location: Cust NZ
Cams for solid lifters have a more aggressive profile so they open the valve quicker. It's unlikely that you could take a hydraulic profile cam and re-grind it for solids without building it up. You could probably go the other way but that's not much help.

I can't see any reason why you can't run solid lifters on a hydraulic cam, apart from the fact that you're not taking advantage of the solids and the potential for more power.

I know people convert hydraulic buckets to solids but would you want to? You'd either have to convert new mizmo lifters or used oem ones. You can buy Toyota solids for about $11 so not sure it's worth trying to convert hydraulic ones. You might need lash caps depending on the clearances.

I guess I'm struggling to see how a bucket will fail to the extent that you're loosing 10 psi. Maybe if the piston came out or broke completely but it would be noisy as. Likewise worn cam journals are unlikely to suddenly change, they'll just get worse over time. I suspect you'll find the issue will be one or more big end bearings but I hope I'm wrong.


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 Post subject: Re: Our little cultus racer
PostPosted: Mon Jun 03, 2019 6:24 pm 
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Location: Brisbane
You said your engine builder increased the bearing clearances.

On our race motor the bearing clearances were less than standard clearances

It might be worth trying a higher viscosity oil to see if the oil pressure drop disappears

I know you are concerned about your lifters getting oil flow to pump them up. Changing to solid lifters is going to be an expensive exercise given that billet cams will be above 1k .
I wouldn't use regrinds for solid lifters

This must be very frustrating for you

My race motor is now in a Mini sports sedan


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 Post subject: Re: Our little cultus racer
PostPosted: Mon Jun 03, 2019 7:25 pm 
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Location: NZ
This engine builder ran a g13b with 165 hp at the flywheel for 20 years in an off-roader.
That’s why I went to him. The book says mains at .0008 min and I can’t remember the big ends. That’s bloody small for racing.
Another guy I know Euan ran a g13B turbo engine with exactly my bearing clearances....1.5 on the mains and 2 on the big ends. Same rods. Ran it on 10/30. Solid lifters....cultus cams....put a washer in the pump relief valve...ended up taking it out as he had nearly 100 psi cold....that is bad....he went back to the standard relief valve setup and got 85 psi cold and 65 plus hot.
There is no knocking in the engine....also Sam....the oil has been dropped three times since the rebuild....there is no sign of any material like I have had before....no sparkles...nothing.
I don’t know why it’s reducing....I’m going to stick the mizuno lifters in it....put 15w50 in it and try it out.


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 Post subject: Re: Our little cultus racer
PostPosted: Mon Jun 03, 2019 7:31 pm 
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Location: Brisbane
It is such a lottery

I cannot believe the number of g13B race engines that have gone bang

Your race engine builder has the runs on the board with his own engine. It should be as simple as duplicating what he has & go racing

I hope you have some success with your planned changes

All we want to do is go racing reliable


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 Post subject: Re: Our little cultus racer
PostPosted: Mon Jun 03, 2019 7:39 pm 
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True Steve....that’s all we want.
The oil pressure was mint...why has it changed...
I wish I knew. Yes I’m frustrated as hell.

Also last time the oil pressure was around 50 psi when it nipped a ring....the mains and big ends were in pretty good condition. If he finds something wrong with a bearing Sam I’m done.
Three rebuilds for 5 track days....it would just tell me the engine cannot run reliably at this level....I cannot keep doing this....suspecting a big end bearing might be at fault makes me feel sick to the stomach. If that’s the case this engine will be stripped and the internals sold...the car broken down and parted out..sad but that’s where I’m at.


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 Post subject: Re: Our little cultus racer
PostPosted: Mon Jun 03, 2019 10:33 pm 
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Location: Australia WA
Hopefully its something simple like a stuffed filter? :oops:
A suggestion before you tear the motor down. Can be done in-situ in a GTI, messy and you'll get oil in you hair/eyes.
Better if motor is on engine stand and sideways.
Exact same principle as your oil accumulator. You can use old 9kg gas cylinder with 1/2" ball valve on top and 1/4"bsp air connector taped into bottom of tank.
Fill with oil, plump into main oil gallery and pressurize via regulated air set at 60psi from your compressor. Obviously you sump and rocker cover is removed and use a drip tray to catch and reuse oil to repeat.
You can visually check flow from each big end, mains and cam journals plus if any flow leakage from relief valve. You will see a difference in flow if there is a problem there.
You will need to check pick up side of the pump for cracks or lose bolts damaged O ring etc.
I used that system when I used to machine and assemble engines when Noah was building the Ark. Saved my bacon many times as its easy to forget internal oil gallery plug or crank plug etc before its on the dyno adding more expense and embarrassment of one of my engines failing.

Good luck, you'll get it sorted and wont be parting it out, to much fun. :D

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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jun 04, 2019 11:09 am 
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Location: NZ
Guys I had to put a Ryco on. It was their high efficiency one. It’s all I could find. Only other thing that was changed when I tried the 5w40. .?? It couldn’t be that could it?

Thanks for the info too.
I don’t want to part it out at all. Just venting right now.


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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jun 04, 2019 1:38 pm 
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I guess given the pressure is measured on the other side of the filter then any restriction in the filter or problem with supply to the pump would drop the pressure. All good things to check before going too far.

GTI CAPPO's flow test idea might be worth a shot. I guess finding a 10psi hot lose may not be that obvious but it might rule some things out.


Last edited by Sam7 on Tue Jun 04, 2019 3:47 pm, edited 1 time in total.

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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jun 04, 2019 3:28 pm 
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Location: Australia WA
Try filter first. If you have the space, fit larger filter which will probably have less press drop for same flow.
I've had a brand name filter collapse on Merc SLC450 engine costing 22K. They did come to the party after a years battle to shut me up, only cause of evidence.
Hyd Lifter shouldn't loose oil, only if bore or OD of lifter is worn/grooved. I don't think G13B is different to others in operation??
If you get to stage of using test rig, plumb it in before the filter and measure pressure before and after filter to measure press drop over filter. You can also heat the oil by placing test unit on a hot plate.

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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jun 04, 2019 3:45 pm 
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Location: Washington State
Is it possible the clearance in the new oil pump are off? My o.e.m pump was on the tight end of clearances after 27 years of being on there with absolutely no wear but the longest it probably ever sat was 6 months. I'm wondering how long the o.e.m. replacement you bought has been sitting on a shelf.
I also remember how many times it took me to get reliable numbers for the main and crank. It was a pain to make sure the tolerances were correct readings. Good luck.


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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jun 04, 2019 6:15 pm 
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Location: NZ
The mains have bmw studs and the caps line bored. The mains were put in all the same exactly.

The ryco filter was smaller than the Mobil 1 filters I was using.
I’m going to try a different filter and thicker oil first....then see.
Thanks for the ideas guys.


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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jun 04, 2019 6:55 pm 
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I'm guessing you're not running a Z125 size filter? I use a Fram that's about 1.5 times the size of a Z125.


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 Post subject: Re: Our little cultus racer
PostPosted: Tue Jun 04, 2019 10:32 pm 
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Joined: Sat Aug 22, 2015 4:01 pm
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Location: Australia WA
Suggestion #2 next time you reverse park one of those flying things you go to work in, steel/borrow one of their turbine oil pumps, they wont know as they have backups. :idea:
My golden rule of thumb during years of engine dyno testing is, never start and engine without oil pressure, better still don't turn it without oil pressure.
You want to keep the wife off your back and protect your 10k motor from rebuild after rebuild if you can?
My first unit was an air driven pump off a emergency gas turbine. I swapped the air motor for a 12vdc wiper motor and fitted it to my Lotus 7 sump plug and to oil gallery before the filter, all externally.
Wiring was through the ign switch controlled by engine oil pressure switch. Turn ign on and prime engine until oil light off, then start. Oil light on then pump on.
Ign off, key on, pump on and flushing cooling internal components.
Now days its even easier with quality, size and price of electric fuel pumps available, plus they have builtin check valves.
Get a hi flow/pressure pump and that should be ok for pumping oil in the short periods its needed. Ecu can control it as to what you want.
If car stands for long periods as most race cars do, Ign on and prime it once a week/month or as often as wife lets you her shed. :D
Sadly it will not turn a pigs ear into a silk purse if you have pigs ears under the hood already :cry:

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 Post subject: Re: Our little cultus racer
PostPosted: Wed Jun 05, 2019 9:21 am 
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Location: NZ
Thanks Guys. Yup the ryco filter is puny. I’m looking to double the size of the filter. More oil. I have the accumulator to preoil the engine


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jun 06, 2019 12:31 am 
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Location: quebec/canada
.002 is too loose, keep in mind this engine in stock form is designed to rev to 8600 rpm from factory with clearance limit described in shop manual ,
personnaly had issues with oil pressure at .002,
then i bough a new suzuki dohc pump suzuki bearings at .001 and problem was solved
if you want to run .002 with good oil pressure maybe you should try 20w60 oil?
or another pump setup...

the washer in the relief valve will only have effects in cold conditions because warm engines like us will only get 40-60 psi oil pressure hot and will not open the relief valve at all


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jun 06, 2019 6:13 am 
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Location: NZ
I need to check with the engine builder it might be 1.5....I’m not sure now. But yes I’m going to get rid of the hyd lifters and go thicker oil...if all else fails I’ll look at the bearings. But I’ll be royally pissed off if that’s the case.

I’ve done a lot of researching. Yes I’m aware of the book bearing clearances and the engine builder who has run a g 13b for 20 years assured me it’s too tight for racing....however understood the requirement for tight clearances for oil pressure on small shells like our engines have. Some might run the bearing clearances tight masking an issue in the head...others replace the head masking an issue in the bottom end. Im Sure oil pressure would be fantastic with .0008 on the mains and .001 on the big ends with .0015 on the cam journals and nice tight bucket clearances....everything else is down hill from there. Even then the standard oil pressure relief valve will open at 65psi according to the book.

Do I expect to improve hot oil pressure with a relief valve shim...nope....is it worth trying...yep....at least I can check what’s going on in there when the sump is off and install an oil temp sender.
I believe if I can get rid of the hyd lifters....and run thicker oil I can increase oil pressure hot to account for bearing clearances both top and bottom. Time will tell.
Thanks for the advice.


Last edited by swift12 on Thu Jun 06, 2019 7:28 am, edited 1 time in total.

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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jun 06, 2019 7:19 am 
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Location: Australia WA
Lesson to all, the importance of engine build sheet with all clearances, measurements and settings documented. A good safe guard for customer and builder, wont stop a failure but somewhere to start.

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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jun 06, 2019 10:08 am 
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Location: NZ
Also if clearances were an issue why would the motor produce 60 psi wot for the last race meeting in summer.....then after sitting for a month and a half lose 10psi and have a lifter that won’t pump up until warm.....so the idea that the bearings have suddenly worn to produce these symptoms (like Sam said about the cam clearances) just seems odd. If that were the case how does the engine produce 30psi of hot oil pressure at idle after a race when all other instances of low hot idle oil pressure seem to yield results of Lower than 10 psi? This sort of issue is all over the place. Worn bearings to the point of high leakage would be unlikely to see 30psi hot at idle don’t you think? Also seems odd. [-X


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jun 06, 2019 11:29 am 
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Big end bearings getting burnt from lack of supply ( ie not wear ) is quite likely and probably the most common failure with these engines. I agree though that the idle pressure doesn't stack up. If a bearing has failed to the extent that you're loosing 10 psi at revs then you'd expect that to also be an issue at idle.

It's worth remembering that the cross drilled main crank design is inherently dodgy as the revs go up. Few will live past 8k and the failure will be big ends. Consider how the oil gets to the big ends. You've got an oil feed to the top of the main. The top main shell will have an oil supply groove. The lower main shell ( ie the one in the cap ) will be plain. The oil hole in the main crank journal will get oil forced in from the bearing groove, a small amount will go through the cross drilled hole and help lube the plain shell on the other side, the remainder will be forced into the intersecting oil hole feeding the big end. The big end feed will intersect the cross drilled main hole at the center line of the crank. As the crank spins faster a number of factors will limit flow to the big ends. Surface tension around the oil hole in the mains will limit the amount of oil entering the cross drilled hole. The centrifugal force of the spinning crank will force the oil away from the center line towards the outside of the cross drilled hole. Oil pressure in the main will have to be greater than the centrifugal force in order for any oil to reach the big end.

Big end failure is a really common problem with pretty much any NA engine using a cross drilled crank that's modified for revs. 4AGE, 2.5 Subaru just to name a couple.

So why don't all G13B's failure as soon as they're revved? I suspect the answer is a lot of contributing factors. The more oil lost from the mains the higher the risk. The longer it's revved for the greater the risk ( ie corner to corner in a hill climb = low risk, the length of a straight on a circuit = higher risk ). The greater the reserve capacity in the oil supply the lower the risk. Other oil supply problems ( too hot, starvation ) will add to the risk.

I wouldn't take too much notice of general guidance figures for bearing clearances. Alloy blocks will need to run tighter mains clearances than iron blocks. A G13B should be fine at the tighter end of the book figures and that will help big end supply.

Thinking about why your idle pressure is still ok, that might well suggest that the issue is in the head. The feed to the head isn't that big so it'll take a certain amount of pressure just to get the oil up there regardless of the state of the head itself. I guess it's designed that way so that a problem in the head doesn't wreck the crank. Can you identify the rattly bucket with a engine stethoscope?


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 Post subject: Re: Our little cultus racer
PostPosted: Thu Jun 06, 2019 2:06 pm 
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Location: NZ
Thanks Sam I know which bucket it is.
I believe it’s in the head because of the idle pressure. I hit the accusump with the rocker cover off and oil bubbles all around the place in the head....out of the bucket bores and around the cam shaft....expected....yes....but to what degree?
I will talk to my builder as he has the specs on the engine....I’ll suss out the main and big end clearances.

I don’t think it’s as simple as....”this fixed my issue” so it’s the solution. It’s certainly something to look at. One engine may have a great bottom end with a s**t top and vice versa. I certainly take notice of those that have been down the path of all fixes and found a solution like boss. There are others that have done the bearings and not solved the issue until replacing the head however....so I think i need to find what it is inside my engine that is “bleeding”

I guess if I got my builder to do the solids and at the same time pull the sump he could at least check one big end....so far however no signs of wear showing in the oil.....


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