930 EFI Conversion in process

[930turbo]

I searched the aircraft industry and was only able to source a gauge that maxed out at 58 inches. I see your goes to 75. One bar is nearly 60, the 58 inch gauge was not enough. Is there a manufacture's name on the gauge?

[Jim2]

Hi guys, the gauge belongs to a friend, though it's on long term loan and now resides in my clock opening. Same diameter as the clock!

I was told it's a WWII bomber gauge. This one is a twin indicator as Cliff noted, for a two engine plane.

Apparently the WWII bombers ran some pretty high boost numbers. Gauges went up to about 90".

Source? I have no idea, but I did find some on ebay which needed rebuilding. Also was told there are some aviation instrumentation shops which carry antique gauges. Perhaps a web search and some phone calls will put you onto a supplier.

I like the absolute format for accurate actual boost indication. In this case having twin indicators has allowed me to do some interesting testing regarding restriction of the throttle body, as well as the intercooler (yet to be done). You can do this with conventional gauges, but this gauge is more accurate. This one was calibrated several years ago so should it should remain accurate.

Jim

[CliffBrown]

Jim

You might find these gauges from old aircraft salvage yards. All the old radial engine airliners from the '50s used turbo-charged or supercharged motors with high manifold pressures (some were turbo-compound motors, high & low boost), DC-6, DC-7, Constellation, etc...

Jim, great job, always nice to see such quality craftsmanship.

[hobieboy]

Hi Jim,
Quick question - what kind of coolant sensor are you using? Do you mind shed some light on the model & where I could get one?

thanks.

[TurboBert]

Hi Jim,
Any updates?

[Jim2]

Hi all, Steve, since completing the efi conversion and relocating the one temp sensor I don't have anything new to report. As I mentioned in one of my last posts I took the machine to the track and did some top end data log runs to refine the programming She's running 100%. I'm really pleased with how this project turned out.

I also ordered some 72lb injectors which have been sitting here for a couple weeks now, but first I want to try and get some time over the Christmas break to build the intercooler. I'm running 10 psi and can't turn the boost up without an I.C. and the 42lb injector were maxed out anyway. I've been busy since completing the efi conversion back in September so the intercooler has been on hold.

Jim

[911boost]

Great write up Jim. Since my 92 has been twin plugged and the wires just run through a hole in the sheet metal, I am actually going to take some time and make a grommet like you did.

Bill

[TurboBert]

Hi Jim,
How'd you make out with the intercooler?

[Jim2]

Intercooler is coming together. You want the long or short version?

[TurboBert]

Long version, of course, with pictures.

[89turbocabmike]

Long please

[NathanUK]

Hehehe

[adomakin]

llllllooooonnnnnggggggg

[gtu935]

Great thread and a great job on the install of the SDS. I have some experience wih SDS and I am very happy with their product and ease of tuning.

You really did a nice job

[Jim2]

Thanks GTU935. From your posts it looks like you been around some big HP equipment. Must be fun, I'm envious.


Here is my intercooler project. It may not be what you think if your were looking forward to a conventional style I/C mated to Carrera manifolds.


Up to the time of my efi conversion I had an Andial/Garritson half bay intercooler which I decided to preserve instead of modifying to fit the Carrera intake. Also, I was looking at the various designs of intercoolers used on the factory race cars to see if there was something more effective.

With my old arrangement I did some temperature tests which displayed 350F turbo discharge at 1 bar, brought down to 170F post intercooler. This is after about six or eight hard laps on a 80 F day and the track here seems to require that you "have your foot into it" lots of the time. By comparison some friends turbo cars with front engine rear drive layouts routinely get post I/C temps nearing 10 F of ambient which is optimistic for my application, but I think I should be able to make an improvement. (BTW stock 930 I/C at 1 bar is 350F in, 250 F out under the same track conditions as above)

I looked into the intercooler design on the old RSR turbos which use an upright core and rely on speed of the vehicle for cooling. I liked the idea of the RSR design because it would stop the cooling fan from drawing preheated intercooler discharge air as well as eliminate any potential fan starvation issues. Note that I also considered water to air format so the heat exchangers could be mounted up front where it's easier to get pressure recovery, but the plumbing, weight, full time pump, front end duct work, and a host of other variables looked like there would be more chances of revisions required in order to get the system working to my satisfaction for the track.

Onwards... I bought some magnehelic pressure gauges (read 0-10” water column or 0.37 psi) which I previously used to measure air pressure around my oil cooler and air dam. Using these gauges I placed probes in several locations around the whale tail and tested at different speeds on the track. Initially higher pressures were displayed behind the tail than on top of the tail which seemed odd, since this would be pushing the car from behind. It could have been the result of an eddie current so I verified the oddity by relocating the probes. I then adding some temporary cardboard elements to change the air flow around the tail and I managed to reverse the pressure differential and come within about 50% of total pressure recovery for a given speed. A further forward facing scoop mounted on top of the tail resulted in nearly full pressure recovery for a given speed, but it would be difficult to retain a decent appearance even though the scoop was only 3.5" tall mounted at the leading edge of the tail near the base of the rear window. I may still incorporate this style of scoop, but not until later.

So based on my pressure tests and cardboard mods I decided to pursue a subdued RSR style intercooler. Keep in mind that my application and concerns here stem from time trial competition and lapping sessions which is mostly what this car gets used for. If the car were intended for the street I would not bother with this conversion and instead I would opt for a conventional design full width intercooler.

The RSR format intercooler will have little or no effectiveness at a standstill unless electric fans are added, but given the dominant track application I'll sacrifice the effectiveness when slow speed street driving.

Here is the original rear end with a perfect tail. Kind of a shame to remove it. I was quite surprised how much the tail weighed when I went to put up on a shelf over my head.


Here is the donor tail which I bought from another pelicanite. It's a fiberglass two piece bonded together. I specifically wanted this style which will most closely replicate the factory 930 tail.


There were a few specific things I wanted for the intercooler. Core tube and fin, charge flowing the short direction, and maximum of 2.5" thick. This gives me minimal weight since it's being added at the very rear of the car, lots of low restriction core tubes, and lesser restriction for ambient air. A little time and thought went into this.

I started by welding the two cores together (OEM auto cores), then mounted the new tail and started trimming the fiberglass so I could determine the best position for the core because there would be limited space to incorporate the tanks.

Itchy and scratchy...


After an amount of measuring and pondering I established the shape of the tanks and built up the inlet tank which conforms to the engine lid header panel.




I also doctored the inlet side of the core tubes creating 58 mini velocity stacks.


Compare here to the discharge end. Also flow tested at this point just for interest sake.


Cont'd

[Jim2]

More...

Here is the discharge tank. Perhaps there are compromises of what is deemed ideal, but most applications have fitment issues so I guess you work to make it fit. For me the result is a little odd looking tanks, but both are larger than the inlet and outlet tubing by about 20%.


Now that I have my core dimensions fixed I started some of the bodywork.

In my case the intercooler will be fixed to the chassis so there will be some flex hose incorporated to absorb engine movement. Also, the portion of engine lid which fits around the I/C will remain fixed to the chassis, but the wing still need to hinged in order to access the engine bay. I established a cut line based on where the latch mechanisms and seams best be located.


Here I replicated the cardboard devices which I developed at the track. Simply put they are just splades on either side of the wing. The splades widen toward the rear of the car effectively sitting on top of the rear quarters. Since I don't want or need to incorporate the tail assembly to the body, I built up the rear quarters with tape then weather stripping, then more tape. I laid up fiberglass on the rear quaters and bonded it to the engine lid.


I followed the engine lid extensions with copies of cardboard splades I developed at the race track. I cut these from some carbon fiber sheet I scavenged.


Side view


Here the splade skeletons are boxed in and done. They will get bodywork to smooth and straighten them. The whole lower section lifted off the tape and weather stripping. After I peeled the tape off I was left with a perfect 1/4" gap between the engine lid extensions and the rear quarters. This will sustain clearance to the paint on the car will be preserved.


Here the intercooler is sitting in place. There will be a splitter dividing airflow between the fan and the intercooler.






Next I'll build the mounts for the intercooler and then start on the inlet and outlet plumbing, followed by some sort of latch mechanism etc.

Jim

[sus911]

I love your "roll the sleeves up" approach Jim and wish you all the best.
Staying tuned to see how you scrub up against the Weissach gurus.

[JimCulp]

I have no idea what you just said, but looking at the design, it looks like it would be pretty damn effective.

Cheers for your innovative approach.

[GaryR]

Would inlets in the "splade skeletons" feed any additional air into the cooler?

[adomakin]

congrats on yet more 'one off' 'get stuck in' 'im doing it my way' fabrication work Jim, truely inspirational. your approach to things is a huge breath of fresh air