Building a 10,000 rpm NA engine. - Page 11

Dessertrunner · #**151** 07-09-2012, 07:25 PM

thats bloody interesting Harvey,

I think you could do this with a standard car and ECU, just con the thing.

oab_au · #**152** 07-09-2012, 07:29 PM

Quote:

Originally Posted by Dessertrunner

thats bloody interesting Harvey,

I think you could do this with a standard car and ECU, just con the thing.

Yeh it wouldn't be hard to do, but mainly for that sort of acceleration., Auto Cross would be the go.

Harvey.

Dessertrunner · #**153** 07-10-2012, 12:56 AM

Do we all agree that it would have to reduce the strain on the crankshaft and main bearings or has someone got a point why that is not correct? It would be good to confirm this point or accept.
Tony

Tapani · #**154** 07-10-2012, 02:15 AM

I would have thought that smooth is good, even distribution of work strokes.... both for power and the rotating assembly.

http://www.aera.org/ep/downloads/ep8/EPQ409_52-56.pdf

Thorough dynamic analysis of a rotating assembly (within a running engine) is not an easy exercise. Especially if you are trying to modify a well developed OEM system.

I would steer away.

Sorry if this takes the thread even deeper away from the original topic, but you have not touched the rod ratio or playing with the bore / stroke combination.....

http://victorylibrary.com/mopar/rod-tech-c.htm

BTW, browsing thru the thread I see no pattern in bearing failures - no analysis (of the few cases) backed up with solid facts found. Pardon me my ignorance, but why all this hassle? Is the bottom end really unreliable at the target rev range (7500 rpm)? The EZ30R runs constantly at least 1000 rpm higher than the EG33 and produces it peak hp @ 6600 rpm. Any comparison made in this respect? Maybe consider this engine as a basis if you want a screamer or utilize the shining features in the EG33 and force feed it?

Honest questions, not trying to flame or anything....

Tapani

Dessertrunner · #**155** 07-10-2012, 03:38 AM

Tapani all input is good it creates thought and this leads to correct direction.

You point is correct it was just my crazy brain taking me in a direction, I was going to bring up bearings and clearance next. As regards stroke to bore ratio a lot of race rules pretty will limit any major change on those. The important thing is to see if there are any numbers that say what I am trying to do is impossiable, so far I haven't seen that. By the way in the past there are suggestion from the drag guys that the EG33 crank is good up to 10k after that it breaks.

A question for all,
I know some beleive that tighter bearing clearances are better but I have read a lot and they say that opening the clearance and increased oil flow is best. Tapani you are right unless we have a few broken engines we can't learn and improve so I think we need to set up correct trials, eg oil at right pressure, oil at right temp then if we do a bearing we can work back words.

So what does every one think.

Tapani · #**156** 07-10-2012, 04:43 AM

A bit off topic

http://phantomotaku.com/SVX/011822-MSA5P0631C.pdf

, but good reading :-)

Tapani

TomsSVX · #**157** 07-10-2012, 10:19 AM

Larger bearing clearances are better for oil flow.... but with the std pumps it does run down pressure ... with a better pump you will be better off

Tom

SVXRide · #**158** 07-10-2012, 12:45 PM

What YT said

-Bill

bazza · #**159** 07-10-2012, 05:41 PM

Quote:

Originally Posted by TomsSVX

Larger bearing clearances are better for oil flow.... but with the std pumps it does run down pressure ... with a better pump you will be better off

Tom

The question that many engine builders disagree on is exactly this. Some want increased oil flow, others want increased pressure (shim pump etc) and others run the larger clearances to account for the higher temperatures and expansion found under race conditions.

The later is why I've gone with the ACL HX big end and main bearings. ACL HX bearings just give you 1 thou of extra oil clearance.

Also with stock bearings vs clearanced ACL HX bearings I've read it about it everywhere but never actually noticed any difference in the actual oil pressure.

You set up the big end bearing end clearances close to 2 thou when you build an engine which is VERY interesting. Because STOCK Subaru big end clearance on everything is 0.8 thou up to 1.8 thou stock with 2 thou the upper limit before new bearings are required.

oab_au · #**160** 07-10-2012, 06:29 PM

Quote:

Originally Posted by TomsSVX

Larger bearing clearances are better for oil flow.... but with the std pumps it does run down pressure ... with a better pump you will be better off

Tom

I agree with the first part. The larger oil clearance is better for cooling the shells, but we don't know if the larger clearance will be limited by the pump or the flow through the crank.
I believe that the clearance, flow and viscosity all have to be worked together, picking one, without the others to back it up leads to fail.

If we ensure that the pump can provide the flow, surge won't happen, and the path to the shells is adequate, I would rely on the bearing manufacture to state the clearance that the shell should have.

Harvey.

bazza · #**161** 07-10-2012, 06:55 PM

Quote:

Originally Posted by oab_au

If we ensure that the pump can provide the flow, surge won't happen, and the path to the shells is adequate, I would rely on the bearing manufacture to state the clearance that the shell should have.

Harvey.

It's a fine balance with this one. Providing enough flow could create surge due to the suction increase, similar to what Tony found with the water pump cavitation issues.

Something interesting which I don't think I've mentioned is the EJ20/25 mainly runs the 10 mm oil pump until the dual AVCS where it ran an 11 mm oil pump. The hole in the block and pipe-up tube at which it sucks through is the same and it's far smaller than the EG33 - which is rather funny IMO. Because Cosworth sell the 12mm upgrade (with EG33 rotors etc) but NOBODY increases the pickup tube diameter or the block hole for the pump to suck oil through. So you've basically got the potential to increase flow but also create massive surge which is EXACTLY what many people found and now many engines builders frown upon the 12 mm upgrade in the EJ. You'd really need to modify the pickup tube diameter and the block inlet diameter for it to work properly.

EJ left / EG right

oab_au · #**162** 07-10-2012, 07:31 PM

Yes I can see the problem there, but if Tony is going to use an external pump, it could be arranged to supply a lower feed pressure to the original pump to prevent it from cavitation.

Harvey.

Dessertrunner · #**163** 07-10-2012, 08:39 PM

I am pulling the orignal pump off completely due to flow restrictions etc. The point you make Bazza is a interesting one because you are also lifting the oil up the pipe which would make the proble worse.

Harveys point about oil flow throught the bearings is a good one amybe we need to run some tests. Set up a test bench motor with oil pump drive by electric motor etc. I will look into it.

Go with me for a second,
With a dry sump we have a engine crank case that is in vacum we all accept that as fact.
THen you would assume that oil pumped into the bearing is entering at the pump pressure plus vacum pressure.
Is that correct??????

If this is so then oil will be trying to get out of the bearing cages as quick as possiable. In other words we are being counter productive as we want the stuff to come out slowly as possiable.

Take it one step further larger clearance in bearing will mean the oil is sucked out sooner. Take Harveys point on board is the restriction on oil flow is before the bearing then its all going to turn BAD.

Remind me why we operate in a vacum??????

Can a suction pump get oil into it when its pumping in a vacum (I know gravity is a factor but)????
Tony

bazza · #**164** 07-10-2012, 09:23 PM

Quote:

Originally Posted by Dessertrunner

Harveys point about oil flow throught the bearings is a good one amybe we need to run some tests. Set up a test bench motor with oil pump drive by electric motor etc. I will look into it.

You need to generate the combustion force (3000-4000 psi+) and heat or any test is a waste of time. The bearings need to be pushed to the limit - engine dyno maybe?!

Quote:

Go with me for a second,
With a dry sump we have a engine crank case that is in vacum we all accept that as fact.

The crank case is theoretically neutral when at X rpm (vacuum from piston up and pressure from piston down balance) however the blowby pressurises the case. The greater the piston the bore clearance the more blowby. Watch a car on the dyno with the breathers open and you'll see what I mean.

Dessertrunner · #**165** 07-10-2012, 09:41 PM

Quote:

Originally Posted by bazza

You need to generate the combustion force (3000-4000 psi+) and heat or any test is a waste of time. The bearings need to be pushed to the limit - engine dyno maybe?!

The crank case is theoretically neutral when at X rpm (vacuum from piston up and pressure from piston down balance) however the blowby pressurises the case. The greater the piston the bore clearance the more blowby. Watch a car on the dyno with the breathers open and you'll see what I mean.

Don't need to generate any combustion to try find the area of restriction to oil flow, simple tests is all. Questions like at 90psi how much can get throught the drilling on the crank to the mains and big ends. How much can get throught the block and how much throught the gallery holes on the bearing. Like Harvey says were is the restriction in the show.

Now it makes sense about crankcase flow/vacum.

Tony