hacker-pschorr

I don't doubt that for a second, and I'm sure Tim would agree.
If I had to guess why Tim has kept the stock manifolds on his car, it would be to give a reald world example of what his kits can do.

Fastest928

Trans is not HP limited, but torque limited

Power is all about the SYSTEM and DETAILS....this is why belts slip and head gaskets blow. Listen to Richard

Stock intakes are good for at least 500 rwhp or 600+ chp ... NA

Super flowing manifolds will add about another 20-30 rwhp

Want the most reliable 600 chp available...do a low compression stroker with big valves and a 8 psi boost via a turbo/SC.

Marc
DEVEK

Z

I don't know what 400rwhp bottleneck you guys are talking about for the exhaust system. As Hacker-Pshorr mentioned, Tim did 556rwhp with the stock exhaust manifolds and stock 928 exhaust pipes behind an "X" pipe, with two resonators in the back to quiet it down more than the RMB. Lag did 492rwhp with a stock 928 exhaust and an RMB, and had the cats on. Old&New has done just under 470rwhp with I believe the stock exhaust manifolds and stock pipes as well. Would more power be produced with a freeer flowing exhaust? Probably, but there's definitely no brick wall at 400rwhp with the stock stuff.

The 5-speeds that I've heard of breaking like that have all been in stroker motor cars. Sticky track tires make it much more likely. Torque is what will kill the transmission, and where in the RPM range that torque is made makes a difference. The Tilo car is a 5-speed. Has anyone ever heard of a transmission failure with it?

Warren928

Blau,

Its always a gamble at the higher horsepower levels. I've seen so many engines prepped for higher than OEM levels put together the "right way" grenade despite their best efforts, so I laugh at many people who have gone the extra mile and still had to tear down their engines anyhow (often quietly so nobody knows that it even happened).It was for them an embarrasment and a huge waste of money. I realise that this is a risk that I will take by gambling on the engineering of the stock block and heads with just bolt-ons. I have three other cars to drive so it wont be the end of the world if it grenades.
I have seen considerable success comparatively by using this method (and advantages too), with many other "lesser" cars than the 928. One positive thing is that its a simple R+R situation if I need to change a bad engine. No internal engine machining work or custom parts needed, but just another used engine and minimal down time. Thats why this is very appealing to me.

But, to each his own method of success in tuning their car.
I'm not a novice of engines by any means. I have worked on and have formal education in everything from automobile engines, 3000 hp reciprocating aircraft engines (radial) to 56,000 hp turbine engines. I understand there is a very technical side to this that includes tuning, tweaking, reworking, safeguarding, and then still-- many moments of aggravation before it all comes together properly.
But that being said, I dont see this 600 chp mark being that big a deal to accomplish. I see a few technical glitches worth a few half days, couple half days tuning, several g-tech runs and a couple of dyno runs. The usual...

Fastest928

Warren,
Wow, great attitude...but replace the word "if" to "when" the stocker granades. IF yoyu are really making 600chp all the time....run after run after run.

You hit the nail on the head...buying used engines is lower cost than replacing blown head gaskets, which is a whole lot less expensive than a stroker engine. Each has its values.

Marc

blau928

Hi Warren,

I'm in no way trying to discourage you, or imply that you are not competent to build such a project..

However, I subscribe to building to a specified design parameter, to assure success based on the parameter specifications and constraints. I am positive that the engineers at Porsche and for that matter, all car companies have a similar approach. I wish you well in your mods, and hope it works well. I am just trying to point out that there are many things involved that may not be apparent. Afterall, engines are just airpumps, no more, no less. However, the devil is surely in the details if you are going to build an efficient engine that will last... This can be seen on a daily basis in comparisons of any two cars..

So, the more 928's improved, the merrier....

I actually enjoy the designing, and the accomplishment of building my project, if albeit slowly... The science is there, and is relatively simple once the considerations have been taken into account.. As far as my experience with engines go, my family built power stations around the world using everything from 1000hp diesels to 50,000hp turbines as well... Crossley, Pielstick, Stork, Rolls Royce, and many others.... I am not a trained engineer, but with the ability to learn from the many I have associated with that worked for my family, some things stick with you..

Anyway, as you said, to each his own.... keep us informed of your progress..

Cheers,

bcdavis

I'm curious about Marc's statement...

Assuming you are able to get a proper air/fuel ratio, or you run an octane booster, or intercooler, so you do not have any detonation, what do you think is the weak link in the stock motor that will break, when you increase boost and power levels?

We have seen several examples of motors with lean conditions, breaking pistons, rings, etc...

But if you are able to greatly increase the flow of fuel, and air, into the stock motor, what do you think is the weak link?
Do we even know?
The big question, is if the stock internals can take 600, 700, 1000 hp...
Obviously they will wear out or break eventually.
But how long will the stock engine last at those power levels?
2 months? 2 years? 10 years?

If you take a motor with stock internals, and stock exhaust and intake, and bolt up a supercharger, or turbo, and increase the fuel flow vastly, and are able to control the detonation, how long will it last before you grenade it? If it will last 5 years or 10 years, I think people would consider it a valid option, since there are so many used engines available. But if the stock internals will simply not take the boost, and the rods will bend, or the crank will break, after only a few months, then it does not seem like a valid option. But I don't think we really know what the 928 engine's weakness is. Do we? Do we know if a stock engine can take those levels of power for a long time? We probably won't know until the MURPH cars have been on the streets for 5-10 years. Then we will know if they are wearing out or grenading due to the excess power. But as was mentioned, it sure seems a lot cheaper to keep your SC kit, drop in another used engine, rather than build a new motor from scratch, and then find out that it too grenades after a few years.

blau928

BC...

My point through all of this, and my design philosophy is to design first, then build once. If you do your homework, it is possible to build a 600hp 928 supercharged that will last a very long time..

I second what Marc mentioned in building a lower comp. stroker that is supercharged... It will last a long time... We already know that stroker motors can go for 100k miles without much fuss. If designed properly, and built properly, there is no reason that a properly supercharged stroker cannot be made to do the same or better...

FYI, When I spoke to Tim Murphy last year, he had also grenaded a few motors before getting his kit to the stage it is currently at. In addition, Warren's car is an 85-56, and as of current, it is believed that only Andy K makes a kit for this application...

Again, devil is in the details, and details are not always obvious.....

bcdavis

But were the engines that MURPH grenaded related to detonation, or to outright catastrophic mechanical failures?

My question is this:

Can you bolt a supercharger to a stock 928, with stock exhaust, stock valves, and stock cams, etc, and get 600+hp?
Can you turn up the boost, and the fuel, and get that kind of power? And if so, how long will it last?

My guess is that the head gasket is an issue if you turn up the boost that high.
But other than a head gasket built for boost, do you need to run different pistons, crank, and cams, etc?
Or will the stock internals work fine?

It seems like more and more people are bolting MURPH and Supermodel superchargers on their stock sharks.
So within the next 5 years, we will know if the stock engine and drivetrain can take 400-500rwhp over that timeframe.
And *when* they do have problems in the future, it will be good to know what failed, so that when people do
build engines, they can replace the weak links... But I have my suspicions, that the Porsche designers
built the 928 engine with strength to back up future plans for power increases. So my guess is that
the stock internals are quite strong. It is just that they never got to raise the power levels past those
of the 911. So what we ended up with, was a detuned, and very *reliable* engine. Which is fine,
if reliable is what you want. But I drive a sports car for speed. I would drive a Mercedes or Volvo
or Honda or Toyota if I wanted reliability...

Warren928

I like your way of thinking , bcdavis. How long before an engine grenades is a good question and a valid one at that. Where is the weakest link considering the goal of hp? From what I have seen on my 86 Auto, its the head gasket. Above 700 hp I would say its the pistons and cylenders needing those deck plates or sleeves.
But its all speculation as to how long 5L 32V engine will last at this level, because nobody has done exactly what I want to do, so the results arent in. Even then it wouldnt be a good measuring tool for one or two examples because there is room for operator error. One lean power run and it could seriously damage the engine, and that could be from a tuner's error.
I am going to run a computer controlled safety system that will stop detonation and lean situations for my S3.

blau928

But were the engines that MURPH grenaded related to detonation, or to outright catastrophic mechanical failures? <<You would have to ask Tim, I do not know why his engines went.>>

My question is this:

Can you bolt a supercharger to a stock 928, with stock exhaust, stock valves, and stock cams, etc, and get 600+hp?<<It depends on the model, and many other things, including condition of the engine....>>
Can you turn up the boost, and the fuel, and get that kind of power? <<It depends>>And if so, how long will it last?<<It depends>>

My guess is that the head gasket is an issue if you turn up the boost that high.<<One of many issues...Combustion chamber events are not only dependent on "boost">>
But other than a head gasket built for boost, do you need to run different pistons, crank, and cams, etc?<<It depends on the operating parameters>>
Or will the stock internals work fine?<<Crank..? Pistons..? Rod strength depend more on RPM than on power... Again, it depends>>

It seems like more and more people are bolting MURPH and Supermodel superchargers on their stock sharks.
So within the next 5 years, we will know if the stock engine and drivetrain can take 400-500rwhp over that timeframe.<<It depends on how the vehicles are used>>
And *when* they do have problems in the future, it will be good to know what failed, so that when people do
build engines, they can replace the weak links...<<It depends on if the forensics are done properly when the things grenade, and if the owners will want to continue>> But I have my suspicions, that the Porsche designers
built the 928 engine with strength to back up future plans for power increases. So my guess is that
the stock internals are quite strong. It is just that they never got to raise the power levels past those
of the 911. So what we ended up with, was a detuned, and very *reliable* engine. <<I agree>>

Which is fine, if reliable is what you want. But I drive a sports car for speed. I would drive a Mercedes or Volvo or Honda or Toyota if I wanted reliability...<<I drive my 928 because I like it. No other reason. I have owned many faster cars, and many more luxurious cars. Not everyone sees things your way... In addition, using your logic to drive a sports car for speed and a MB, Volvo, or Toyota for reliability, equates to sports cars are not reliable, and the "reliable" marques you mentioned cannot go fast..>>

I disagree with you on this point... I have owned several Mercedes and other "reliable" cars that were capable of 155mph without much fuss.. My 928 has 234,000 +miles on it, and I have only gotten stranded twice... Once for a fuel pump, and second time when the cam broke at 230,000 miles... I consider my 928 very reliable... I had a Ferrari that would sputter, buck, and have all sorts of Gremlins before even thinking of going fast... And I quite like Ferraris... I could go on....

However, Porsche designed the 928 as a GT car..... a car with the ability to go both fast, in comfort, and be reliable..... If your car is not reliable, chances are you will not be driving it much.....

Fastest928

Actually, modern porsche (1976 onwards) designs engines based material specs and BMEP. As material strength increases, so goes the safety factor for BMEP.

You will notice that folks very connected tot he factory, RUF does not go offering 700 chp engines like the "tuner" market, as they have to warranty their engiens for many miles and since Porsche also honors their warranty, they are probably in the zone for a "consumer" level of reliability/perfromance balance. In other words, 996TT rate at 450 stock from the factory, 550 from Ruf and 700+ from tuners. Whose engines do I want to go fast in for 100K miles or longer.....you guessed it..Ruf or factory.

I like to use BMEP as a high level guide in determining engine reliability....you can do the calcs on various engine configurations...........

A boosted 5l engine at 600 chp is not a reliable engine...reliable for hundreds of hours, maybe, reliable for 1000's of hours, unlikely, reliable for 200,000 miles....ya dreaming.

Marc

bcdavis

You're probably right...

It just seems like 928 engines are getting more and more available used, for cheap...
So if it ends up that the supercharged 928 engines end up lasting for 5-10 years,
just like John's Calloway did, then I think that bolting a SC on a stock engine,
then replacing it in 10 years, seems like a good value as opposed to building an
engine that will last for 20 years.

bcdavis

And regarding vehicles, if you look at my .sig, you will see that I tend to categorize, based on task.
A sportbike for drag races, a 928 for high speed fun, and a Toyota for day to day reliability.

Z

I have to wonder if you're either selling some very cheap used engines, or some very expensive head gaskets.

Time wouldn't really be a good way to determine it. If anything, milage might be a better indicator, but the way that those miles were driven would be a factor. So far the highest supercharged cars I've heard of had 30k+ miles on them after having the installation done. Compression tests on one of them showed all cylinders to be between 186psi-189psi.

Actually Tim had two head gasket failures on his car. There has never been a failure on with the kit and the level of boost it provides on any car that I've heard of.

The first failure was of the factory installed original head gasket. After removing the head, it was found that the gasket was pretty rotted, and that the head surface was also corroded. The other head gasket failure occurred when running around 13psi of boost on the stock engine.

I'm going to say yes if you're talking about 600 crank horsepower, which would be about 510rwhp. Lag got 492rwhp (about 578 crank hp) with a completely stock engine and exhaust, except for the RMB, and I'm sure that with further tuning and tweaking that a higher number could have been achieved. That 492rwhp was with just bolting on the supercharger stuff and putting it on the dyno, and the only tuning having been done was to set the fuel pressure at idle.

I wouldn't suggest it if all you're planning to do is increase boost and fuel.

I'd say that's a pretty broad statement to be making, since much of that would depend on how those 200,000 miles were driven. At this point it could just as easily be said about the stroker motors. I mean so far it appears that there may very well have been more miles put on 600 crank horsepower boosted 5L motors than on 600 crank horsepower stroker motors.