Curious, what size pistons and crank stroke combination was Todd entertaining? Crank, cast, forged or billet? What about rod length?

 

I'm just taking a guess as to what I know is available and possibly utilized to get to 4.1L ........ a 80.4 mm crank with 104 mm pistons would give you a 4.0958L motor.

 

I have been told that over in Germany they are having problems wiht the 4.0l... and my source is very reputable... seems like the 3.8L is a proven choice for now...

 

Proven by lil bluey but soon the 4.1 will be proven as well for next year supra nats :-)
Robert

 

I will start the tear down in November.....

 

"Problems" really don't mean much. There are so many uncharted issues with plus 4.0 displacements. Once you get into strokers it isn't simply a matter of adding a stroked crank. Clearance issues can develop. You need to address rod length or risk excessive rod speed which will damage the motor. Solving this requires looking at and changing a combination of other parts. There is nothing special about a plus 4.0 liter number wise. You can get to 4.0 liters with a 104.4 mm piston or a 80.4 mm crank and 102.4 mm pistons. There are different ways of approaching that particular number. Just pushing the bore while maintaining the 76.4 mm crank is the most economical way to go, but not the best way IMHO.

Math/physics wise there is a point that once you get to a certain stroke in combination with a certain bore ......... this type motor will accelerate slower than with a smaller stroke.

For informational purposes, I believe 9ff's monster motor is a 4.1 liter. Our motor is just under 4.4L. Trouble is there isn't a Porsche part with the exception of a very modified Spanish case in our build. Everything else was designed and produced. Get much above 106 mm bore and you need to produce longer heads and cases. In addition a longer timing chain is required. These are some of the obvious issues.

The 3.8 liter has been around for awhile and the bugs are definitely worked out by most. Many tuners/builders have built them. An issue that has kept people from throwing money at the larger motors is the race rule restrictions. There is no place to race them. I believe the lid was recently raised to 4.0 liters. Above that and experimentation is not for the weak of heart or those without a team with experience, extraordinary design person(s) and a few extra dollars.

The extremely low number of people experimenting with plus 4.0 liter motors is testimony to the above. For the most part, experience is scarce. Protomotive may have recently entered, 9ff has and so has Koro of Germany.

The long and the short of it is there are a number of mistakes that can be made and very few people to follow at this point in time.

 

9ff offers this 4.1 for both the 997 and the Cayman. I am sure that it can be gotten for a 996 as well.
Sport Engine “CARRERA” 4.1 litre

• 420 HP
• 4.1 litre trunk engine in exchange
• Machined cylinder heads
• Bigger valves
• Camshafts
• New bigger intake manifold
• Sport Clutch
• Exhaust Manifolds
• Stainless Steel Sport Muffler
• Sport Metal Catalytic converter
• Air Filter
• ECU Upgrade
• Engine Assembling

Part #: FM 97-4.0 C
$38,970.00

 

M96/97 wet sump engine block. Garbage.

 

Not on the same page. Motors don't even resemble each other.

 

There are many kits available, there is even a 5.0 kit. The more important question, which one of these kits actually work???
Robert

 

There are stroker kits up to 5.0L for normally aspirated boxer motors. I have never seen a turbo motor larger than 4.2 liters. They may be advertised but not in existence. I'd love to be proved wrong.

You don't have long to see if our 4.4 plus liter works.

 

Chad
I hope it works!!!!!!!!! Please make it work before November!!!! That is when I want to start my next project
Robert

 

Robert,

I believe the biggest unknown is the line where the stroke gets to the point you have a loss of acceleration versus a smaller stroke. Our designer was a little hesitant about being in the 4.6 liter range. We decided to be on the safe side and use the 4.4 liter range.

When you get into these numbers you have to adjust both bore size and stroke.

What items became issues.

1) Strength of the crank and bearings.
2) Machining the manifolds and case halves for new liners.
3) Rod, Case and oil pump clearances.
4) Length of the rods.
5) Strength and thickness of the liners. Certain areas of the liner require a lot more strength.
6) Strength of the case. Advise you start with Spanish case.
7) The degree of motor balance.
8) Matching and blueprinting each individual piston to each individual liner. Same goes for individual valves to individual springs/individual spring pressure. The motor must be balanced to the ninth degree.
9) Height of wrist pins on pistons.
10) How to increase deck height.

PS ......... This motor will be ready for competition on June 16th this year.

 

Wow Chad!

If you notice our join date's to 6speed are the same; that's not a coincidence. I've been following this build from funcarsonline to rennlist to 6speed. Wherever this thread went, I went. Real excited now to hear that it's really almost complete.

I can't wait to hear about the drive. Any magazine write ups planned? Considering all the changes since the last one, it's about time.

 

caneaddict,

Thanks for the very kind words. I hope KA doesn't disappoint. We are awaiting the arrival of the pistons, rods and liners. They are suppose to arrive by April 16th.

We will be doing another article. I really want Dave Coleman, who did the last article, to do the followup ......... however Dave is no longer an editor with Excellence.