MattCarp

Guys, I'm totally engrossed in the Greg Brown thread about the 6.5L engine and I'm wondering....is the 928 engine that great of a platform? Were the Porsche engineers geniuses?

Forgive the ignorance here (I'm a computer guy by trade). Perhaps it's because I don't know the details of the competing platforms - engines from the 911, Ferrari, the Corvette, etc. But how does the 928 engine stack up?

The aluminum block seems pretty revolutionary, especially at the time, but I read about the issues the engine had like the debate about the wet sump oil system, thrust bearing failures (arguably a driveline issue more than an engine issue), and the 2/6 rod bearing oiling issues and have trouble determining if these are serious limitations, or just quirks in the design given the finite budget/time Porsche had to develop the engine.

I'm really impressed with the work the modifiers and engine builders are putting into their engines, but am thinking, are they doing it because of the challenge of doing it, the love of the 928, to race the 928, OR, because the 928 engine is truly a great platform and deserves more effort/engineering to get a lot more out of it.

How do you qualify the "greatness" of the engine? Is it:
- HP or torque / lb?
- HP or torque / displacement?
- hours (or miles or revolutions) to rebuild?
- HP / fuel consumed?

I guess the fact that they were able to evolve basically the same engine from the mid 1970s through 1995 should say something.

Curious...

Randy V

Yes.

Next question.

MattCarp

Come on Randy, share some wisdom here.

You need to qualify that, or at least point me in the right direction...

What makes it so great?

WallyP

Well, yes, sorta...

The good:
They are powerful from the factory.
They will run forever, in most cases. A very long-lived engine for most owners.

The bad:
They require periodic maintenance, primarily in the timing belt area. A belt system refresh every five or six years takes care of that.
They are heavy - the 32-valve engine weighs about 640 pounds.
There is very little cheap, easy power gain available.

Others will add to the lists...

Randy V

The fact that it is an alusil alloy block, makes the cylinders nearly impervious to wear.

The cyclinders are etched to expose the silicon matrix.

That is one of the very unique aspects of the 928 engine. Others have since done it.

FBIII

I would think a great engine has either pioneered new technology and or had a successful racing pedigree. The 928 has neither. It improved on the aluminum silica technology but didn't pioneer it. I think the Chevy Vega did. Additionally it has the design flaw of pumping the top end with engine oil causing bearing failure. This however may be on the verge of being corrected by GB.

Cosmo Kramer

I think it is a great engine for the purpose that it was originally designed, which is a GT car. It was designed for sustained high speeds on relatively straight roads. In this scenario they are very reliable. The engine was never designed for high G corners and racetrack duties, this is where the 2-6 rod bearing failures and oiling issues come into play. However, many have effectively modified them to get around these problems.

James Bailey

Ah yes..."I guess the fact that they were able to evolve basically the same engine from the mid 1970s through 1995 should say something." sure does....says they could not jusify spending much on a modern engine for a car model they could not sell in any reasonable volume.... But the 928 engine when used as it was designed to be and correctly serviced will run for a very, very long time.

Zinland

I think Mark Anderson got 3 or 4 years of very intense racing with one of Greg Brown's stroker engines with out touching the internals. Watching some of the incar videos from the early 90s will give some idea of the service these motors endured.

txhokie4life

Who or what is GB -- can you give me a link --- new 928 owner
that might track it every now and then.

thx.

Mike

James Bailey

Greg Brown builds awesome engines, including 928s. Check the thread "early dyno results " it is front page news !

mickster

GB is Greg Brown of Precision Motorwerks of Anaheim, CA.

Are you thinking DE days at PCA or real hard racing?

That will help answer the question. For DE days these cars are great. For serious racing, like any car, they will require some mods or some risks.

Either way the positives for the 32V 5.0 liter & 5.4 liter, as many said are the liner-less cylinders and great pistons. The engine produces a great mix of torque and horsepower and the delivery bands are very good.

The downside is lack of variable valve timing (aka variocam), lack of electronic ignition (although there is mapping of the fuel with the LH), weight and maintenance (interference motor can destroy valves/pistons if the timing belt fails). Lack of oil delivery (see above).

Now you can, for $$ convert to vario-cam and stroke the motor (increasing the displacement and output) and add an electronic ignition. You can turbo charge (single or dual) or supercharge, or if you have the $$$, do both!

Like any race car the only limits are time/money/imagination/engineering.

If you are thinking of racing then you want to check out some of the site sponsors and also Simard Racing, 928 Motorsports, etc.

Check this too:

http://www.928intl.com/race/index.htm

txhokie4life

DE's only. Maybe just for my wife. Otherwise my daily driver. Euro 4.7L '82.

Considering this 928 a good entry to DEs for my wife (due to the Auto and NOT being
a loud and crude race car (less intimidating)).

I track and race a 924S for which we did new bearings and Lyndsey sump work.

I just want to know if I'm tracking the 928 at a DE -- do I need to consider
similar oil pick-up issues. It just might be that I don't want to haul the 924S
and have both my wife and I track the 928s.

I'll eventually have a Boxster S track car with an accusump system, not sure if that
will be a street driver or not.

Mike

James Bailey

The 944 engine was the first to exhibit #2 rod bearing failure when operated at high RPM. The 928 when it started being agressively tracked some 20 plus years ago then had #2/#6 bearing failure. For new drivers on street tires you can get away with running D E as long as you are NOT running over 6,000 RPM for extended periods of time (long high speed sweepers being the worst). My old very brown 1980 has held up far far longer than I ever expected but I do the shorter track events with more corners and short straights on DOT "race tires" and rarely pull 6,000 RPM. I will be running it in two weeks and if it were to blowup it owes me NOTHING !

auzivision

A 32 valve overhead cam aluminum engine with MAF based fuel management injected at the ports built in 1987 and still running strong today has to say something.

The first 32 valve Chevy was the Corvette ZR1 which came out a few years later.



The LT5 lasted about 5 years before GM dropped this design idea... except for derivatives like the Cadillac Northstar.

Ford came out with one in the mid 90’s… and later a supercharged version which was really hot.

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