Normy

That was precisely my point Jim. I said that a 2 valve, in "racing trim", can come withing a few percentage points of a 4 valve engine horsepower wise. The problem with this: an engine in this sort of "racing trim" is a snarling, nasty, polluting, ill-idling machine with all the personality of a bobcat with a nasty scratch on its' *****. You don't want to drive a car like this to the grocery store-

The four-valve that makes the same kind of power as this 2 valve is a different animal all toghether in that it probably runs pretty much stock..

Remember folks- street cars have 4 valve heads because of driveability and emissions issues, not for performance.

Now, to get back to it: You can acheive what via a good port and polish job on a 2 valve? I just rebuilt the intake on my S2, and I was SOOOO tempted to pull the heads and have them ported!

N

GaryJ

Thanks Jim:

I am starting to come around to your way of thinking. A 5L EuroS Hybrid is a known commodity and by all accounts is a fun strong engine. I just wanted to make sure I wasn’t skipping a good opportunity to do something more but it looks like that is about as far as is usually gone.

The only other option I am seeing is supercharging the 5L Hybrid but build in a lower compression ratio. I’m just not familiar enough with supercharging to know if it will make a stable and drivable car that will last.

Thanks,

Gary

GaryJ

BC:

Thanks for your input. After my conversation with Carl I am giving consideration to supercharging. It just wasn’t on my original plans for the build. Carl sounded like a great guy and very knowledgeable I agree he would be a great resource.

Thanks,

Gary

Jim bailey - 928 International

You quickly become aware of the Law of Diminishing Return as you start down the slippery slope of building horsepower. First in terms of the dollars spent for incremental increases then in the results in terms of track lap times. Bump your car from 230hp to 330hp and the results are very impressive but go from 330-430 HP and on a 2 1/2 mile track it is typically less than 2 seconds per lap. When you get right down to driving on the street it does it really make much difference if 0-100 is 14 seconds or 13 seconds ? Either way in California if they catch you it is jail time. Your car with a strong 5 liter hybrid should run about 170 mph ...in "open road" trim .

GaryJ

Thanks Jim:

I appreciate your level headed approach and it is hitting home with me. The more I look the more it seems that for the 16V motor the 5L hybrid is a strong and proven option and seems to be the extent of major development for the 16V. At the end of the day it is seeming that something close to 300rwhp out of a 16V is about the most proven to expect, pushing the envelope beyond that seems to be uncharted waters. I don’t think I am in the position to be involved on the development side of things.

I have been a 928 owner for over 20 years and have been putting the pieces away to do the 5L hybrid build for about 10 years. I just wanted to check that over those 10 years there hadn’t been some major developments and I would be shortchanging my build. I will continue to gather information to see if anything really makes sense beyond the 5L hybrid build, if for nothing else than to put my mind at rest that I have taken my car as far as can reasonably be expected. I want maintain the character of the car which is a nice driving car but can be very respectable on track days. At the end of the day I want to be able to push down on the accelerator get pushed into the seat and have a smile slide across my face.

Thanks,

Gary

Jim bailey - 928 International

Plus you really can add the supercharger in the future should you feel the need

GaryJ

Even with my new 10.5 CR?

Jim bailey - 928 International

Yes Carl has provided the parts for a Euro LH 310 hp high compression kit ....you would just be a bit boost limited compared to dropping the static compression so less than ideal but still an option should you "need" it

BC

Just shoot in more methanol.

GaryJ

Jim:

I do like that idea. I was also thinking about what Carl had said about using my original crank and having about 8.5 CR and that would make a very boost friendly engine. But if I found boosting to be a pain I would have a pretty weak engine if I took off the SC. At the end of the day I don’t NEED any of the options the car runs and is fun with tight cornering roads but is just too slow on the track.

Thanks again.

Gary

GaryJ

HI Brendan:

I am not sure I am willing to head in that direction.

Thanks,

Gary

BC

Just to be more specific, not as a fuel , but as a charge cooler. Its just a pump, so valves, maybe a MAP computer, and a tank. The 2V heads are not perfect for boost, at least not as good as the 4V heads, but any "ceiling" of boost vs detonation will be raised with water/meth or just meth.

GaryJ

Brendan thanks for clarifying.

I can see if I do decide to SC I am going to have to start the learning process over again.

Gary

bcdavis

I think the problem with the motor you are planning to build, is that it will not be enough power.
Yes, it will be more than you had before, and it will make you happy for a while.
But if this is your long-term car, that you intend to have for a long time,
then you should have power that you can grow into. It's always better
to have more power, and have to be gentle with it, than to not have
enough, and have to go back to the drawing board again. If you are
building this engine from scratch, then build an engine that is designed
to take the stress of supercharging. Build it with forged components,
low-compression pistons, block coating, etc... If you build it strong,
and build it to last, it should last. You don't want to get out on the track
with this new car, and be frustrated with your inability to catch the other
cars on the straights. If you are building an engine, either build a 6.4
liter monster stroker, or a supercharged car. Don't waste your time
with all the expense of building an engine, and not get something
awesome out of it at the end. I would hate to rebuild an engine,
and get the same power I had before. If I am going to spend
thousands of dollars, I want some serious power...

hacker-pschorr

Not necessary at 6psi - that amout of boost should give him about 100hp even without an IC.