PRV engine: what breaks at what speed question

[EarlHickey]

It would seem that pistons could live to 9500 rpm and even beyond with the really good stuff ...

What components die before then, when and why?

[WelmoedJ]

How about bearings, seals, cylinder wall damage?

[EarlHickey]

How about bearings, seals, cylinder wall damage?

I don't know because I haven't blown up any, much less several of these while winding them to the stratosphere.

I'd think as long as they've been out, their weak points should be well known.

Is there inadequate oil flow or pressure to any or all bearings to attain high rpm in these engines?

I found writing indicating that the cam can fail prematurely, and not on all PRV's, from oil starvation well under the maximum safe piston speed.

That's not the same as not being able to spin and actuate while it's turning 4750 rpm, without snapping into two pieces or knocking off a lobe.

If it cannot, my guess is upgrading it from one that is cast, to much stronger material, would give better results.

The long connecting rod looks dubious on the tiny small end, but, that's easy enough to cure.

[WelmoedJ]

The engine has been designed for durability (and reliability), not for excessively high RPM.

It is known that the oil channels in the cylinders heads are narrow can be subject to clogging if the oil change intervals are neglected.
On very high rounds the narrow channels could be a problem for sufficient oil supply to the various points.
A standard or "blown" D has no problems with the engine as it is, nor does the oil system.

If you want to make high rounds (to what purpose?) you should consider replacing the engine with one capable of handling those high rounds.
IMO Japanase engines are better capable of handling that (e.g. Honda).
More power does not come from high rounds only.
The engine need to be designed for that purpose.

[EarlHickey]

The engine has been designed for durability (and reliability), not for excessively high RPM.

It is known that the oil channels in the cylinders heads are narrow can be subject to clogging if the oil change intervals are neglected.
On very high rounds the narrow channels could be a problem for sufficient oil supply to the various points.
A standard or "blown" D has no problems with the engine as it is, nor does the oil system.

If you want to make high rounds (to what purpose?) you should consider replacing the engine with one capable of handling those high rounds.
IMO Japanase engines are better capable of handling that (e.g. Honda).
More power does not come from high rounds only.
The engine need to be designed for that purpose.

Do you know any specific rpm of which specific components break?

Like I can tell you that a big pontiac v-8 loves breaking connecting rods and trashing those huge main bearings at speeds over 6000 rpm.

I can tell you that a pre-pantah Ducati will make very expensive grumbling noises when the needles skate at speeds over 9000 rpm.

Scott two stokes destroy your bank account with metal horror at 5200 rpm.

Norton Atlas and Commandos tend to break cylinders at 7200 rpm and change.

I could go on and on, but, I'll explain instead that I'm only trying to learn what breaks beyond the 6500 rpm redline as it's short stroke will certainly have the piston safe all the way to 9500 rpm without forged or eutectic pistons.



Have there been any repeated failures of any components with force fed engines?

What failed, how much boost and at what engine speeds?

Now beyond all that, I'd love to have one of these singing it's song at 9500 rpm hooked up to a stick car, but, I have far more productive things to do.
I'm not a "starry eyed" kid or boy racer type at all.

Crazy enough to consider building one and taking it to the salt flats? Maybe and skilled enough to do it if I make my mind up that's the plan.

I did run across some highly tuned Renault Alpines claiming reliability at 8000 rpm. I've not found any F1 versions running 2-4 atmospheres.

I have yet to learn if they run the same crankshaft, rods (I doubt that) or even oil pump as the B28 stuffed in the back of the DMC.

I don't know if any oil galleys or passage were enlarged or modified... etc.

[WelmoedJ]

I do not have any figures on the RPM breaking point of a standard/Turbo PRV.
I know that, while testing for Turbo or blown (compressor) engines DMC has destroyed several.
If you need to know those values, your best bet is to contact DMCH.

Yes, Alpine made a name in fast and still reliable engines.
But they were prepared for the job, not just standard engines.

I'm not that deep into this matter that I have or can provide what you want.

[Nicholas R]

Most here can count the number of turbo charged DeLoreans they've been exposed to on one hand, MAYBE two. Unfortunately, people aren't really known for taking their engine to the limits because it's not a very high performance engine to begin with. In the last 6 years or so of being on DMCtalk, I'm not sure I've ever read a thread about someone experiencing a major failure, such as something in the lower block. Biggest problems I've ever heard of are probably those getting oil leaks in the valley from casting defects.

[EarlHickey]

Most here can count the number of turbo charged DeLoreans they've been exposed to on one hand, MAYBE two. Unfortunately, people aren't really known for taking their engine to the limits because it's not a very high performance engine to begin with. In the last 6 years or so of being on DMCtalk, I'm not sure I've ever read a thread about someone experiencing a major failure, such as something in the lower block. Biggest problems I've ever heard of are probably those getting oil leaks in the valley from casting defects.

I'll agree that the very tiny ports (although for certain reasons they are little giants) and factory tuned CIS runners along with EPA compliant fuel/ignition curves AND log exhaust with it's also EPA compliant quiet muffler, have it severely choked and neutered.

However, looking at the line drawings and numbers, I have to disagree that this engine is a boat anchor. It has many things, by basic design, going for it and appears to be very capable of far more than DMC accepted from it.

It appears to me to be far over-engineered for even a paltry 150 horses.

Nobody is disagreeing that they work fine at 8000 rpm although I do not know, yet, what has to be done to the DMC engine to make it not fly apart or weld itself together at those speeds.

DMCH..... who and where?


btw... I ran across a "wiki" on the PRV engine which states it has a "hemi" combustion chamber. It absolutely does not, it has a chamber far superior to that of an actual hemi.

[David T]

Typically at higher and higher RPM's the valve train can't keep up. The valves start floating (staying open). To compensate you go to higher spring pressures but that wears the valve train faster. Next to go typically are the pistons and rings.To compensate you go to looser pistons and rings. If everything is dynamically balanced and you damp out the harmonics the bottom end is usually the last to go. You do need to upgrade the hardware and probably increase the oiling. You really don't want to go too high, the curves for the HP and torque start dropping off anyway.
David Teitelbaum

[Farrar]

DMCH..... who and where?

DeLorean Motor Company Houston.