nevsrevs

ian h said it was down to harmonics more than any thing else.

MO' BENT RIMS

lee is a top bloke. helped me alot in past

SiZT

I know of 1.8l engines (not zetecs) revving to 8,000rpm with a rod ratio lower than 1.5

Hard to tell once the oil pumps gone, however if it was a crank flex issue then you would probably see through the wear in the shells. If it's balanced correctly with a proper crank damper (alledgedly this engine had one) then harmonics shouldn't be an issue

XRT_si

iTrader: (2)

This engine was fully balanced and had the original pulleys/flywheel.

No marks or signs of wear on the crank/shells.

Dennis_Wiseman

iTrader: (1)

This is why i don't understand about the flex theory. For it to flex enough to throw the pump gears out of sync or load them up there would need to be substantial movement.
A crank physically can't move enough if the bearings have been specked right to do this and if it did there would be clear wear marks. As mentioned the mains caps are stronger in the silver top so if anything it should be black tops failing in abundance if crank movement was the issue.

Another way to look at it, if we are saying the problem is crank flex and given the Black tops rarely fail does this mean they don't suffer from any kind of flex even though there are many people running the same levels of rpm and boost as a silver tops?

Dennis_Wiseman

iTrader: (1)

Might be worth contacting the people who sell the gears. They might be willing to donate a set as a test as it would be good publicity

Luca

iTrader: (2)

It has to be down to cavitation higher up the rev range.

Fiesta_Jed

The rod ratio dosent have a massive effect what revs you can run.

Its the stroke that will alter piston speeds. Longer rods take some load off the piston skirts so you may be able to rev higher and faster with them.

I can only assume that the engines you mention have a very short stroke and/or are rebuilt regulary?

Sp3no

iTrader: (1)

This thread is starting to make me think that the whole "issue" with lightweight pulleys and oil pumps failing may not be related?

TimC

iTrader: (1)

Longer conrods definetly DO adjust the piston speeds, more so at the top and bottom of the stroke then at any other point.

AustenW

Incorrect

Stroke alters overall piston speed (velocity), the longer the stroke the faster the piston

Rod length however alters the piston acceleration and deceleration at TDC and BDC

AustenW

http://forum.efilive.com/showthread....-Piston-motion

TimC

iTrader: (1)

Isn't acceleration or deceleration a measure of speed?

I get that the change in conrod length will not change the amount of time it takes the piston to get from the top to the bottom, but with a longer conrod the amount of time the piston stays near the very top or the bottom of stroke whilst the crank is traveling through a certain amount of stroke will increase.

xr2wishy

iTrader: (2)

acceleration and deceleration is a measure of rate of change of velocity.
m/s^2

nevsrevs

just been thinking, why dont high powered cvh,s do oil pump,s? or do they and i dont hear about them..

Fiesta_Jed

Also why does nobody complain about zvh oil pumps breaking?

Canada1

High powered cvh's certainly don't rev to 8000 rpm. The 2 valve cylinder head really limits rpm capability - just doesn't move enough air at high revs. Even highly modified heads run out of flow around 7000 rpm. The relatively poor (for a race engine) flow also limits power output at a specific boost. 25 psi boost through a cvh inlet manifold and head allows much less air/fuel mixture to get into the cylinders - much less specific power output - less crankshaft flex etc.

Some of the issues with oil pumps failing on high rev/boost zetecs may be related to the lightweight flywheels/clutches and lightweight pulleys. Not much engine harmonic damping with these lightweight parts. Any 4 cylinder without balance shafts will have higher order harmonic issues. Insufficient damping - danger.

Cheers

nevsrevs

but if we are saying that its not down to revs, then we still have high powered 1.9 cvh,s reving and boosting to the same levels as zetec, if you look at a cvh pump its not a million miles away from a zetec

zetaboostboy522bhp

i cant think of any 2.1 zvh revving to the same level as a zetec as said above the cvh head struggles to make the power for it to be worth revving to 7500 rpm , i know sids engine that is one of the most powerful i seen (dyno provern ) makes peak power at 6500rpm and thats on a t38 turbo
i personally think its down to the poor materials used and harmonics in the engine , just looking on the net about ford oil pumps and theres a massive problem with the ford boss engine using sintered oil pump gears , there now using billet gears but made from en40b , the same as top end cranks are made from and they class them as indestructable.

cheers paul

nevsrevs

when did they start using en40b then paul? on modern engines or in all there pumps?

sas

Has anyone measured the backlash between the oil pump gears and crank drive flange? I see some with huge gaps (wear).

S.

Canada1

A cvh with the same boost levels does not come close to the power per cylinder a zetec is capable of. Its all about head flow. Cvh's are very flow restricted over 7000 rpm.(really over 6500 rpm)
150 hp per cylinder loads a crankshaft much more than 100 hp per cylinder.

Cheers

zetecbeast

So do we have any more info on the cause of the oil pump failures? If its harmonics , and people are using a stock flywheel and damper, then whats the answer? fully balanced internals and...? a YB engine? lol

I'm going to see how my engine fares and am aiming for a minimum of 400hp, ideally 450hp. Am going to get all the bottom end balanced and see how it goes...
If she blows it will be new engine time

nevsrevs

The answer at that power is a external oil pump, the reason is still undersided, harmonics, torque, crank flex, cavitation, all of the above

zetecbeast

I know a dry sump would be a safe bet but I can't really afford it in this build. An external pump solution doesn't exist for the silver top yet , plus it's a grand in itself...! I think I will just have to get it all balanced and a good oil pressure warning alarm, and see how it goes

lacey

It does exist, and it is a grand, but that is complete with nothing else needed other than time to fit it

stuart collins

iTrader: (7)

they do ,mines just done another 1 and my mates s1 did 1 at the start of the year both done very low miles ,was makin 347 @wheels 32psi and pressure just went so got to come bits again and go dry sump

lacey

Who's doing your cvh dry sump