Pic of inside a 911-6 shroud

[Sandeep]

Found this while on www.pelicanparts.com/forums Its a pic of the inside of a 911 shroud with the alt removed.

http://forums.pelicanparts.com/showt...lternator+fins

Look at how the cylinder tins extend up into the airflow from the fan. There is also an air diverter on the back of the 911 alternator that does not seem to be present in a T4 911 shroud. Perhaps this is a clue as to why the T4 911 shrouds don't cool evenly.

911 Cylinder tins ...



I'm finishing my datalogger using a Motorola 68hc11 microcontroller and hope to get some readings from my Fat 911 cooled T4 engine before I store the car for the winter. Currently, I can only log 25 seconds of CHT readings from #1 and #4. I've got the rest of the items I need to connect #2 and #3, just need to find the time to finish it.

#4 seems to run at 315F normally, and 360F when I get on it, #1 seems to run at 300F normally, and 325F when I get on it. Hope to get some solid data and then I can fool around with the tins to see if I can even them up a bit.

I know the DTM is the "Cat's A$$" but I love to tinker

Sandeep

[Massive Type IV]

Nice observation Sandeep.. Its not just a clue, but one main thing i have been preaching about for two years.

Its too bad that NONE of the 911 systems for TI and TIV engines are deep enough to use the 911 factory air diverter! The -6 engine is deeper and allows the space for the cone on the back of the alternator!

also note how low the shroud sits to the cylinders compared to your shroud. This decreases volume above the cylinders and bosts pressures to the cylinders. You can also see that all cylinders on the -6 engine are behind the fan, instead of on the -4 where the #2 and #4 cylinders sit directly underneath the fan and the airflow must travel 90 degrees to get to them easily.

A 911 shroud could be made to really work on the TI or TIV but the development would take a tremendous amout of time, design and trial- error and testing on the dyno and in the car.... I simply lack the desire to do it since there are cheaper alternatives that already work with no further development. After my last cooling bout with the TI DTM my *** is whipped and I don't want to do any cooling R&D for a long time!

The temperature differences that you see are EXACTLY what I saw with ALL 911 shrouds as a trait. Very uneven temps, even on your stock engine....If you change drive ratios to a higher ratio you will cool better but lose approximately 4 more HP from a system thats already sucking off atleast 15 now. I found a 1.3:1 drive ratio to work best for cooler overall temps, but the uneven splits still existed.

NOW, Zen has Dual CHT gauges and 180 Dyno HP with almost 10:1 CR..... His heads run 275 and dead even from bank to bank ALL THE TIME.....

Now, if you could make me one of those data loggers for the bug so i can toss my miles of wiring and crap for testing we could do some swappin.....

[zen]

correction. with the DTM i run 275 if it is under load (load peaks head temps, revs peak oil temp) like going up a long hill. jumping on it around town i haven't peaked 250. with my FAT (and this is not a direct comparison to Sandeep's since we are talking a very different engine) on my same engine, i ran 275-300 under normal load.

[Massive Type IV]

I stand corrected!!

Happily corrected!

See, when I drove Zens car I was driving at wide open throttle....LOL

[Wally]

Originally Posted by Sandeep

Look at how the cylinder tins extend up into the airflow from the fan.

911 Cylinder tins ...

But what puzzles me most, is the 180 degree angled part of the under cylinder tins. The puzzling is that the original type 4 under cylinder tin has a similar design, but according to Jake, does not work well on a type 4. The type 1 straight undercylinder tin design seems to work best.

I certainly believe Jake that the type 1 style tin works best, but with my cylinders it doesn't fit at all, so I have removed the 180 degree ridges and cut off the under cylinderhead part, but it does still screw to the case and head in the original way. Hope it works...

I don't think that the upper part of the911 cylinder tins and how they extend into the airflow will work the same on a type 4 or that it matters a great deal, but I am curious as to why there is no extra guidance to the head part. The type 4 with 911 fan may need some help in that department (at least with nikasils).

Greetings,
Walter

[Massive Type IV]

wally, your cylinders and heads will change everything! In my testing I found that even the slightest change in the heads, cylinders and etc would change a vast amount of particulars..

Thats why I went ahead and released the Type I DTM. I could work for 20 years trying to make it perfect, but with TI engines there are so many variables that it would all be worthless as soon as someone built something any different than the way I duild my engines..

I could make the 911 fan work better, but I'm not up for it now...

[verbeekb]

My project includes 964 cylinders and the tins pictured, they fit "factory". The 964 and 993 have an additional fan on the front of the alternator, probably to aid alternator cooling, along with its own little shroud, but no directional vanes. The curved part makes sure that the undersides of the cylinders get airflow along them, otherwise they would practically be without cooling air, this is also the only part of the 964 cylinder that actually has cooling fins on it.

Brian

[Wally]

Originally Posted by Massive Type IV

wally, your cylinders and heads will change everything! In my testing I found that even the slightest change in the heads, cylinders and etc would change a vast amount of particulars..

Yeah, I was afraid you were going to say that

I could make the 911 fan work better, but I'm not up for it now...

I hear you! but you input on our measely attempts to make it work are very much appreciated!
Thanks,
Walter

[Wally]

Originally Posted by verbeekb

The 964 and 993 have an additional fan on the front of the alternator, probably to aid alternator cooling, ...
Brian

Hi Brian,
I don't believe the little (radial)additional fan is for cooling the alternator. The alterator is cooling by the fan itself on the front through holes around the pulley. No, I think the little radial fan is meant to distribute the air more evenly left and right! Thats why the C2 or 964 fan hasn't got a cone at the back like the old 11-blade fans had.
The special fan housing of the 964 assembly makes sure the air comes out straight ahead instead of curved more to the right (bank 1 & 2), like the old han housings did.
It took a pic of the 964 fan housing to illustrate this:

I also put up the pic at STF, but since no one else seems to use it, I'am sure you can maybe more relate to my above story

Best regards,
Walter

[verbeekb]

Hi Wally,

I am somewhat puzzled now as to its exact function/operation now. But there is a cover missing in this picture. The cover is similar to the earlier version (pre-964) except that it has no vanes attached to it. The plastic fan has a 928 603 *** ** (I forgot the rest) part number which places it in the generator/alternator parts category, whereas the rest of the cooling fan parts are all in the 106 (cooling) category. This fan was first used on the 959, which had watercooled heads/aircooled cylinders, and looking at it, it gets air from the front (!) .. are you using this one on a type4? These housings tend to be somewhat deeper, but it could just be the idea, I never really measured them up or anything. Thanks for the pic!

Brian

I came back and uploaded a file called 964.bmp but I can't figure out so fast what I'm doing wrong.

[Wally]

Originally Posted by verbeekb

Hi Wally,

.. are you using this one on a type4? These housings tend to be somewhat deeper, but it could just be the idea, ...

Yes, its on the engine that I am assembling right now with a BAS shroud in which it fits just nicely. This engine will also have the 100mm 964 Nikasils, 76,4mm stroke and full DTA programmable injection with Jenvey 48mm Throttle bodys. I hope to have some more pics of the set-up next week-end and will log head temps as the engine will run (if...).

Greetings,
Walter

[verbeekb]

hmmmm .. *perfect* geometry there .. 127mm rods too?

[Wally]

Nah, it seemed that the short 127mm rods were only used in the 964 by Porsche because they otherwise had a engine-width problem...
All serieus tuners of 964 engines try all sorts of desperate measures to lengthen the rods to get a better (read higher) rod ratio (sorry).
I tried to keep it cheap and used lightenend stock 2 liter rods, converted to 23mm piston pins. Its now about the same width as a stock 2 liter type 4 .

Greetings,
Walter