Variety is the spice

[Henry Schmidt]

Originally Posted by PeteKz

Henry, thanks for the info on rods. I'm familiar with the theoretical discussions about rod shapes, but if getting the best length for your application requires the use of rods made by Carillo or Pauter, then I totally understand the choice. I would choose a longer rod too, and a tight ring stack, given the trade-offs.

Not only length but weight is also a viable concern at higher RPMs. We also play with wrist pin diameters. The weight savings by changing from a standard length 3.2 Carrera pin 23mm x 60 mm pin weighing 132 g] to a custom 21mm x 50mm pin is substantial.The difference is about 50grams. 50g at the right end.
Add to that an X-Brace or forged side relief piston with substantial under-crown milling and you can see the weight melting away.

It's hard for me to imagine that oil can collect on a rod shaking like a wet dog on amphetamines at 8000 RPM, but I'll take your word for it!

Remember there are piston squirters blasting oil all over the rods.
As I said, "theoretical". I'm not certain that theory is valid but controlling oil dynamics within the engine case is a black art. The science is way over my head.

[Henry Schmidt]

Originally Posted by gled49

Henry, does the filter eliminate the pressure drop across the filter. I’m currently stuck with OC229 on a 993 console because of space.

The filter uses a 30micron @ 85% element and pressure drop is minimal if at all.
Remember, this is a supplemental filter designed to keep out large chunks from contaminated oil and internal explosions.

[Henry Schmidt]

Originally Posted by Turbo_pro

That one piqued my interest as well. Maybe Henry will give us more detail.
3.0 short stoke with titanium rods.......wow!

Hi Jim
It is a pretty cool build.

Short stroke 3.0 66mm X 98MM
New Carrera case w/shuffle pins
66mm, 9 bolt SuperCrank
CT1 Dry film coated GT3 mains (red)
Pankl GT3 rods (21mm pins)
Clevite rod bearings (CT1 coating)
996 Twin turbo oil pump
993 steel intermediate shaft/gears
98mm CP X-Brace pistons 11.5:1 (under-crown milling)
Mahle cylinders cooled by Supertec 906 cooling tin
Big valve head (51mm intake w/8mm stems, 43mm ex)
Supertec head studs
DC 80-02 Dougherty Racing billet cams
Aasco springs and Ty retainers
40mm in ports, 38mm ex
Supertec rockers
Supertec idler arms
Supertec Power Pulley (105mm)

[WheelWell]

MFI

maybe on the 2.0L 914-6 Racer..........looks space age.....
doesn't look like any Bosch I've seen.........
Is this a new marketplace offering?

[Henry Schmidt]

Originally Posted by WheelWell

MFI

maybe on the 2.0L 914-6 Racer..........looks space age.....
doesn't look like any Bosch I've seen.........
Is this a new marketplace offering?

The 2.0 race has PMO carburetors.
There is a 3.2 SS 911 engine with high butterfly mechanical fuel injection. Is that what you are asking about?
The throttle bodies are a German high butterfly recreation offered by TRE.
The stacks are fabricated at Supertec to facilitate air filter installation.

[Walt Fricke]

Henry
I never understood why Porshe, when it went to MFI, used the same intake manifold configuration it used for the Webers which preceeded MFI. They had to bend the two end manifolds in to fit the carbs available. But didn't Porsche have the MFI stuff made for it?

An issue about fitting existing air filter stuff?

A friend with a flow bench told me he could measure the better flow for the center manifold versus the flow to the two end ones.

[WheelWell]

There is a 3.2 SS 911 engine with high butterfly mechanical fuel injection. Is that what you are asking about?

Bingo...that must be it.



It's the bright appearance that has me baffled. I was wondering if it new manufacture from the likes of Eisenbrandt or Koller & Schwemmer...afr studied opimization ?.... all to produce custom made space cam? .....
...I'm good for any story of the dark art magic of MFI.

Thanks in advance.

[Henry Schmidt]

Originally Posted by Walt Fricke

Henry
I never understood why Porshe, when it went to MFI, used the same intake manifold configuration it used for the Webers which preceeded MFI. They had to bend the two end manifolds in to fit the carbs available. But didn't Porsche have the MFI stuff made for it?

An issue about fitting existing air filter stuff?

A friend with a flow bench told me he could measure the better flow for the center manifold versus the flow to the two end ones.

Small company using components available at the time. Your thoughts about air cleaner seem reasonable.

[Henry Schmidt]

Originally Posted by WheelWell

There is a 3.2 SS 911 engine with high butterfly mechanical fuel injection. Is that what you are asking about?

Bingo...that must be it.



It's the bright appearance that has me baffled. I was wondering if it new manufacture from the likes of Eisenbrandt or Koller & Schwemmer...afr studied opimization ?.... all to produce custom made space cam? .....
...I'm good for any story of the dark art magic of MFI.

Thanks in advance.

The high butterfly is produced by Mittelmotor and sold by TRE. We have issues with function and appearance so we rebuild the product to fit our specifications.
The space cam/MFI pump magic is the product of Mark Jung @ MFI Werks. He is indeed a sorcerer when it comes to making this stone aged crap live again.

[Henry Schmidt]

Supertec will take credit for this fuel line innovation. The fittings and fuel line are fabricated in-house. We came up with this design while trying to fit an MFI engine in a 917 replica. Limited space made high arching fuel lines impossible and steel lines were just too ugly.

[mikedsilva]

Lovely

[Henry Schmidt]

A quick look at the 2.0 914/6 GT engine.

66 911 sand cast aluminum case [rehabilitated from 90mm cylinders]
Double shuffle pins
Pauter crank (Chevy rod journals)
Titanium Pauter rods
930 Turbo oil pump
Light weight timing gear
Racing IWIS chain and solid tensioners
11.2:1 CP pistons
JB Racing Biral cylinders
Supertec 906 cylinder tin
DC 80/98 camshafts
[Model Dur @ 1mm Valve lift Lobe center Lift @ overlap
DC 80/98 I/E 283/265 .505"/471" 98 6.2 mm
Supertec rocker process
69 "S" heads Bill @ Extreme did the head porting and valve work
Aasco valve springs and titanium retainers
Supertec head studs
Supertec idler arms
Series 900 amber shroud
906 fan ring
Supertec power pulley
993 engine oil filter console with 30 micron filter
PMO 46mm carburetors
Supertec twin plug distributor
Custom machined lower valve covers for 914 chassis clearance.

[Uwon]

^^^WOW.Outstanding!
Can you tell us a bit more such as expected output, size, intended use?
Johan

[porschedude996]

WOW! Please tell us about the chain tensioners.

[Henry Schmidt]

Originally Posted by Uwon

^^^WOW.Outstanding!
Can you tell us a bit more such as expected output, size, intended use?
Johan

Vintage legal 80+1 mm (66 x 81mm) 2 liter. Output is expected to be around 230hp (115hp/liter) It was built for a 914/6 GT with historic credentials.

[Henry Schmidt]

Originally Posted by porschedude996

WOW! Please tell us about the chain tensioners.

Old school mechanical tensioners from the late 70s. They have an Allen bolt adjuster. The design was originally intended to be externally adjustable.
With three drilled and tapped access holes [for each tensioner,] you simply remove the plug, reach in with an Allen wrench and adjust as needed. This feature was a pretty cool idea but deemed unnecessary given the frequency of race engine tear-downs. The extra holes offered a potential for leaks although they rarely did when plugs were properly sealed.
Like most other mechanical tensioners, [when properly adjusted] they eliminated tensioner failure 100%.

Caveat: The problem with mechanical tensioners is that builders forgot that these little engines grow and in doing so, the chain get tighter. That means adjusting the chains on the "loose" side is essential. How "loose" is case specific. Magnesium cases grow more than aluminum cases. A mag case will grow as much as 4mm from crank center to cam center.

[PeteKz]

"Caveat: The problem with mechanical tensioners is that builders forgot that these little engines grow and in doing so, the chain get tighter. That means adjusting the chains on the "loose" side is essential. How "loose" is case specific. Magnesium cases grow more than aluminum cases. A mag case will grow as much as 4mm from crank center to cam center."

Hmmm, that's odd. Other than the case, the cylinders, heads, and cam housings, are all the same basic material (aluminum). Therefore, the only difference in thermal expansion would be due to the case itself. And coefficient of thermal expansion (microns/meter X *C) for magnesium (26) is close to most aluminum alloys (23). The width of a case half is about .15m, and the delta between cold (20C) and hot (120C) is about 100C. Thus, the case growth in width for magnesium contributing to the crank to cam distance is about 26u/um x 0.15m x 100C = 390um, or .390mm. For aluminum it is slightly less, 0.345mm, and the difference between expansion of an aluminum case half versus a magnesium case half is 0.045mm. Negligible. Even the overall crank to cam distance would be about 3 times that, or about 1.2mm.

[Henry Schmidt]

Originally Posted by PeteKz

"Caveat: The problem with mechanical tensioners is that builders forgot that these little engines grow and in doing so, the chain get tighter. That means adjusting the chains on the "loose" side is essential. How "loose" is case specific. Magnesium cases grow more than aluminum cases. A mag case will grow as much as 4mm from crank center to cam center."

Hmmm, that's odd. Other than the case, the cylinders, heads, and cam housings, are all the same basic material (aluminum). Therefore, the only difference in thermal expansion would be due to the case itself. And coefficient of thermal expansion (microns/meter X *C) for magnesium (26) is close to most aluminum alloys (23). The width of a case half is about .15m, and the delta between cold (20C) and hot (120C) is about 100C. Thus, the case growth in width for magnesium contributing to the crank to cam distance is about 26u/um x 0.15m x 100C = 390um, or .390mm. For aluminum it is slightly less, 0.345mm, and the difference between expansion of an aluminum case half versus a magnesium case half is 0.045mm. Negligible. Even the overall crank to cam distance would be about 3 times that, or about 1.2mm.

So, what's odd? Are your doubting the amount of expansion or that the expansion has a substantive affect on chain tension? The 4mm number [perhaps cam to cam, memory being what it is] came from a service bulletin in the late 70s when extreme heat from thermal reactors caused the engine to over heat sometimes as high a 450 degrees and continue to overheat after the engine was shut down. I remember leaving my car with the valet and seeing the asphalt grow red.
All 3 case types expand differently...sand cast, magnesium and die cast. I can't wait to see the expansion rates on the new billet case. Even the cylinders differ in materials over the years. cast iron, Biral, Alusil, Silimal and Nikasil. My caveat suggests that you keep these conditions in mind while setting up solid tensioners.
If you believe that my caveat [meant it be informative not scientific] is something you would ignore, be my guest. Good luck.

[PeteKz]

Henry, not doubting that the growth the in overall width of the engine requires the chain tensioners to deal with that. I was doubting 4mm growth between the crank and cam. But if it's cam to cam for a really hot engine, that's in the ballpark.

Case types expand differently not because of how they are manufactured, but based on the properties of the alloy. The great majority of aluminum alloys have thermal expansion coefficients of 21 to 24 um. A few, such as hypereutectic alloys, have significantly lower coefficients. But you wouldn't want to carve a case out of that. So you can expect the billet cases to be cut from a wrought aluminum alloy slab with a coefficient in the same range as the cast aluminum cases.

Yes, the cylinders also expand at different rates. I used the rate for aluminum in the calculation above, which is close to worst-case expansion. Cast-iron and Biral are almost the same, because the sleeve of the Biral is also cast-iron. The Nikasil, Aluisil, Silamal, and Lokasil have different expansion rates, depending on their composition.

[Turbo_pro]

Interesting how a precautionary "caveat" became a point of contention.
I wonder who benefits from each interpretation?

It seems like there is a nuance to adjusting mechanical tensioners that can benefit from the advise of an experienced engine builder.

Thanks Henry