James Bailey

I think Carl already has a nice alloy PS reservoir.....obviously the advantage of adjustable pressure, ability to move weight toward the rear, and eliminating the belt drive power losses make it all pretty attractive.
It also means the power steering works even after you blow a motor.....

mark kibort

its easy to use the spec classes in SCCA racing as comparisons for times, because they are a good barometers at a track near you that they have records at... and the best in any particular popluar track are all with in 1/10s of each other as proven at the nations. sorry.... back to on topic

that is expensive.... and would that be worth it, so that you move a 3lb pump to the rear-ward of the car? if it worked more efficiently, possibly.. if it created more pressure all the time, possibly as well. but $1000 is a lot even if its a full kit, but im sure it is worth the price to have it near turn key.

Jim,
where do you think the energy will come from to drive the powersteering pump? if its electrical, its coming from more load acting on the battery and "belt driven" alternator. adjustable pressure is good for slow turns at lower RPM levels, but i dont think the weight moving rear ward is even a rounding error in balance at best. the pump weighs 3lbs. by the way, its going to be much more efficient than driving it by an electric motor which is only 80% efficient at best, and that electricity has to come from the alternator, which again , is belt driven.
but, the best point is that you get power steering when you blow your engine. Now, thats a notible advantage?

Carl Fausett

Jim, there's only so much $$ in a year. The new rad, intercooler, and instrument cluster have it all for this year. I am not opposed to an electric power steering pump at all. Kinda like the idea, actually. Just out of money.

To hear you speak, you must have an electric in your racer. How do you like it?

Carl Fausett

I'll keep my eyes open for a deal. I can fab up all the other bits, and my alternator is more than big enough. No issue there.

I do wonder what the parasitic loss is of the belt-driven system off-idle. They are designed to make sure power assist is available at engine idle speed and at rest. Once the car is rolling, steering effort is naturally reduced anyway. Shortly after idle the hydraulic system is producing too much pressure. and the by-pass valve opens. Basically, at high-way/race speeds, that bypass valve is open and the parasitic loss should be very very low. Perhaps even lower than the electric motor on the alternator. (Kibort's point).

Carl Fausett

Here's the first mock-up. Intercooler on the driver's right and radiator on the driver's left. NOTE: visual is deceiving as the boxes include the end tanks for each. The actual core sizes between the end tanks are smaller.

Both the intercooler and the radiator are larger than they were last year, but I will give the numbers to the manufacturers and let them tell ME if they are big enough for my application. Then I can adjust some dimensions up or down to get a package that works.

mark kibort

Carl, what is the main purpose of converting your radiator to a tilt version? Usualy the corvette guys will do this for room and plumbing ease, as well as being able to use a large radiator that wouldnt normally not fit if standing up with the aero packages they run.
are you going to employ a hood vent?

atb

Carl,

Toss in a couple of side drawers, and you're home free...

Carl Fausett

Those are exactly the reasons we are doing it. Fit a bigger rad, and get the rad away from the engine. I think it will also smooth the air stream under-hood somewhat... the airflow around the motor is a tortuous path and this way we can "aim" it up and at those exit louvers so it does not have to smack the front of the motor as much.

We have been running vents in the hood for years. These pics show them well.

mark kibort

I havent noticed it with the white color. i saw them on the fenders, but didnt see or remember them on the hood. yes, since you have hood vents, that flow will go directly out them and then over the car and make your rear wing more effective too. However, you saw the 928 aero graphs, right? since you are making a new hood, you might want to move the vents forward about 12". i think you might be in "no man's land" for the lower pressure zones. (getting very close to ambient or actually the high pressure zone as it approaches the windshield). I know you didnt have a tone of time in the tunnel , but it would have been interesting to see or verify the pressure zones from porsche on the 928. the lowest pressure zone was just in front of the stock placed engine in the engine bay.. (just around the front 25% of the tire and wheel position across the car) (almost exactly where your 928motorsports banner is located).

looks good.

mark kibort

This shows the pressure zones around the hood front area. i verified this with pressure sensors at up to 130mph.
It basically shows that if you have the radiator leaning forward, you can have a nice opening to the lowest pressure area which will end up right in front of the engine, to where the op of where the radiator was previous located.

Carl Fausett

Excellent points.

Our focus in the wind tunnel was reduction of drag, and we spent no time on trying to optimize draw from under the hood. At $600 an hour, you get very choosy about what you want to effort! So although I have some good drag and leading edge/trailing edge data, I do not have any data on the location of the low pressure zone on the hood that's any better than Porsche's old chart which you have already posted.

Looking at the last photo posted below... they slowed the wind tunnel down to where you can stand in the tunnel with the car and photo the smoke stream at various points. I was confirming that my guess on where to place the hood louvers to evacuate the engine bay was good or not - they look to be in an area of smooth laminar flow, which should be a nice low pressure area.

Carl Fausett

BTW: we were able to lower our Cd (Coefficient of Drag) to 0.25. This is a gain equivalent to adding 95 HP to the engine. My best information is that the original 1978 928 had a Cd of 0.38, which was lowered to 0.33 in 1986.5/87 with the changes to the front and rear bumpers, smoothing in the lights, adding the belly pan, among some other things.

Mongo

Those pictures of the car remind me of NHRA Pro-stock. Thinking of inter-series racing?

mark kibort

That isnt surprising considering the mods you have made .. it looks like a bullet now!

notice the wind tunnel indicator stream... it breaks up (starts to stagnate) after the area where your main hood sticker is. (where the stream is tight)... put the vents there and you might greatly improve the downforce and flow pattern out of the hood.

i verified this on the track with pressure sensors. (and tufts that would point up out of the vents )

Carl Fausett

True, lower pressure further forward, but the headers would be behind the louvers then. We have no cowl. Note hood meets the glass.

So louvers placed where they are (over the headers) so the air from the radiator could wash past the headers and carry some of that heat out.

Still a low pressure area, although perhaps not as low. A compromise.

Would like to not spiral off into a wind-tunnel discussion. OK?