Mrmerlin

Thats a great ride report ,
I am glad that the car did the 170 avg.
Next the 200 MPH club!!!

dr bob

Glad you all survived the event and the ride home. That fuel pump and heating issue sounds like it needs a 'standard' pump for all but boosted operation. Another small pump and another check valve? The factory depends on having some spare AC capacity for fuel cooling. Many earlier cars (non-928, before AC cooling was adopted) suffered tremendously from vapor-locking. Bosch recommended increased pump pressure to solve the symptom in many CIS cars (BMW, Saab, etc), but that did nothing for the hot fuel returning to the tank. Eventually you had a tank of boiling fuel on real hot days, regardless. It may be that you need a cool-suit ice bucket in the car, with the fuel return line passing through a small exchanger in the cool-suit return line.

The fuel hose in the suspension sounds scary as hell, probably a lot scarier in real life than us reading it here.

Charley B

Holy Crap!!!! A relentless trail of gasoline pursuing you through the dessert night intent upon eliminating another 928 by fireball! Glad you guys made it home in one piece.

George it sounds like the safest place for you was on track at 200mph.

Great job.

Respect.

andy-gts

I love your write ups.....man you are the mcgyver of 928's.....way to go!!!!!!

200 mph next time, for sure, totally unreal !!!!

thanks for coming home in one piece!

jorj7

Andrew,

You know I only take photos of 928s right.



But in this case I did get a few shots to the competition. Here they are at the Car Show on Saturday:

Ford GT40 (1st place 169.9788 mph avg)


Monte Carlo (3rd place 169.2572 mph avg)


Both cars had navigators, so had an advantage hitting their targets.

And just a note, since I didn't seem to make it clear, I did hit 200.5 mph in the radar trap in the May race, I was just trying to go a little faster this time.

jorj7

Bob,

We've done a lot to try and keep the fuel cool, increase the fuel line size (less friction), insulate the fuel lines in the engine compartment (and not were they're exposed to unheated air), two fuel coolers, insulate the exhaust pipe everywhere it's near the fuel line or cell, have a 044 fuel pump in the fuel cell and have a second (switchable) fuel pump when I want to go faster. But when the temperature is already 102 degrees outside, the road is hotter, and the elevation starts at 6500 feet and goes up, it's not always enough (as it was yesterday). I had mentioned to Bill last night that I would probably replace the Bosch 044 pumps with something that flows less, but would still flow enough when run in parallel when needed. Or with ones that would both reside inside the fuel cell. We'll see, I have until May to get it all sorted out (just like last winter...).

And it's a good thing Porsche put the fuel pump location on the opposite side as the exhaust ( I kept that location), less chance of igniting the gas.

Bill Ball

George joined the club (at 200.5 MPH official speed) in May. He was hoping for a bit more this time, but the headwind held him back.

dr bob

Some thoughts--

-- Smaller lines in the engine compartment and anywhere they aren't insulated would cut the residence time and surface area in those warmer sections. 'Friction-heating' of fuel is, um, not a factor compared with absorbed heat.

-- I'm a big fan of securely-mounted hard piping for critical fluids. Hose is easy, almost too easy, and looks cool, but you really only need it where there will be flexing. Steel or stainless steel tubing is usually lighter than a comparable bit of reinforced hose.

-- Get the pumps out of the tank if you can. The pump motors are adding heat to the fuel in the tank. All externals means some of the pump heat will dissipate into surrounding air instead of into the fuel in the tank/cell. Maybe you need a small-TDH (less than 2 feet total discharge head) pump in the tank just so you don't boil in the line between the tank and the pump, but less heat in the tank is better.

Bill Ball

Until this event, it appeared we had solved the fuel heating, vapor lock issue. Internal versus external was a debatable trade-off. We had both, two 044s plumbed parallel and individually controlled, one in the tank, one not. We would run one pump except for the speed trap area of the race. In May we had no issues at all during the race or when travelling up and back. The fuel temperature stayed out of the "danger zone", fuel pressure was always good and the pumps never complained. This time it was warmer at times. We lost the fuel temp sensor unfortunately, so we can't comment on that. On the way up from the Bay Area to Ely this time, the external 044 George was running started to complain (got loud, pressure fell). Switched to the internal, then it started complaining. Dumped in some cool fuel and as the ambient temps dropped, the pumps seemed to be OK. During the race, with ambient temps in the high 70s and low 80s, everything went well. It was only later, with higher ambient temps that things deteriorated.

For cruising and everything below the very high speed trap section of the race, George should probably run a stock pump or nothing more than a 040 rather than an 044. Probably two stock pumps, flipping on the second during the trap, would be fine.

Initially there was excessive pressure drop in the delivery lines, so we doubled the crossection. The lines are insulated in the engine compartment. Perhaps the main issue was being over pumped - too much recirculating volume. George originally had one LARGE volume (supporting 1000 HP) Aeromotive pump. We quickly abandoned that for two lower volume 044s, run individually. This is a case where too much of a good thing is not good. I'd vote for a couple of stock pumps or 040s, in parallel. Whether one is internal or if a small-TDH feed pump would be better is a question.

I'm not sure why Tim and Cheryl, Marc and Susan, and others have not encountered this problem. The only difference is George is supercharged, so he has additional HP produced to overcome the drag of the supercharger. However, George originally developed terrible problems just cruising along the highway at 70 MPH at altitude. Marc & Susan, who drove their car to the race as well, never mentioned any such issues. Nor have Tim and Cheryl, who live and have driven The Beast at high altitude. This is under conditions where the HP being produced is rather low (cruising on the highway). The only thing I could attribute it too was the original Aeromotive pump, supporting 1000 HP, was way too large, even with a controller that cut its output when not on boost. The dual 044s and a few other changes seemed to have fixed this until our trip in warmer temperatures.

John Speake

Excellent result !! Congratulations to both of you !

Bill Ball

John:

Sharktuner was, of course, key to getting a tune that worked so well. Were I still agreeable to being a navigator, we would have had Sharktuner active during the race so I could tune on the fly if needed, something I think no one has ever done with any car in this race. But it appears that our tuning, done both on a dyno at sea level and on the road race course during some practice runs, unfortunately limited to 3rd gear at 150 MPH, hit the mark.

Richard S

Congrats George! Getting home safe is the most important thing. You and Bill deserve the "Most Dedicated" award, always dealing with every surprise!

Rich

John Speake

Thanks Bill, but the Sharktuner is only a tool. It's the operator that counts !

That's why my congratulations were to you both, knowing how much hard work went on preparing for the runs.

jorj7

For all the tech geeks, here is the LM-1/LMA-3 log from the high speed run.



Looks like Bill had it dialed in pretty good.

jorj7

Got my laptop running again and started working on the video. Found a bug strike at about 9 minutes into the run. It's amazing how well this new technology works. Who would have thought a 1080HD 3CCD OIS video camera could focus so well on something only 2" from the lens



Not all the video is unusable, at some places it was able to focus on other locations.

Here is a look from the inboard camera as I hit top speed:



And a view from the backup "nanny" cam as I passed the radar guys:



I guess I've got some video editing to do...