Jan 14th, 2015 Dakar Rally Stage 10 Race Info & Discussion

Join in and discuss all the action from stage 10 of the 2015 Dakar Rally. The special section of stage 10 is 359km long. Robby Gordon start time: 10:45am/et, and he will be the 9th car off the line. After a 9th place finish in stage 9, Gordon sits 20th in the overall standings. Raceday chat will be available throughout the entire 2015 Dakar Rally.


2015 Stage 9 Photos


STAGE 10 TRACKING


STAGE 10: CALAMA > SALTA

Connection 501km | Special Stage 359km | Total 860km

COURSE OVERVIEW

The motorcyclists and quad bikers will set off for their second marathon stage! After the Chile-Argentina border, this time the day’s special stage will start on the Salinas Grandes, more than 3,600m above sea level. The altitude should curb the competitors’ enthusiasm and cool down their engines. The more technical final phase will separate the toughest of them from the rest. For the liaison section, the route will then follow the Paso de l’Acay, at an altitude of 4,970m.



The GREEN section of the route is the connection , the RED is the Special Section of the stage.

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Ya, I know....but he mentioned support truck.

Not necessarily. Look at the profile map of the stage. The finish was at over 11,000 feet. It's a NA engine, and suffers a disadvantage at that altitude vs. the turbo engines.

Sort of true--but not to the extent that many here seem to think. This, in part, is why the ASO has already increased the restrictor size permitted in naturally aspirated engines. It is not true that only naturally aspirated engines loose power at altitude. The turbo diesels also will be down on power, just not to the same degree. Although the turbo is still compressing air, it also has lower density air to compress.The math works out like this: For every 2,000 feet of altitude there is a 1 psi drop in ambient air pressure. So at 10,000 feet ambient pressure is 9.7 psi. Sea level is 14.7 psi. A naturally aspirated engine will make power at the rate of the pressure at altitude divided by that at sea level. So at 10,000 ft, Gordini power will be 9.7 psi/14.7 psi or 66%. A turbocharged engine will also loose power, but at a lesser rate. It is a function of turbo boost pressure. Let's assume they are running a 20 psi turbo boost. The math for 10,000 feet then becomes (9.7 psi+20 psi boost)/(14.7psi+20psi boost), or 85%. So the Gordini at 10,000 feet is at 66% of full rated power, the turbo engined Mini at 85% power. Temperature and humidity will also affect these calculations, but the comparative power losses will be essentially the same. The only thing that could change this is a varriable rate turbocharger (adjustable pop-off valve), but the rules do not permit this.

Could they adjust the boost to run higher pressures to minimize the effect of altitude without damaging the engine?

the sub 5.0 L engine got a 1mm restrictor,aka the Toyota's. I don't see anyone saying they should go Diesel.
The LS7's did not get a larger restrictor. That would be something to lobby for.

No reason for Toyota to go to diesel. Nasser has a problem they're sitting 1-2.

exacto, GORDINI no funciona en la altura. asi de simple

Nice illustration Mark. I guess what concerns me is the Toyotas (understanding they got a break from ASO ) were not that far off the Minis... I'm assuming the Gordini is a good platform, just depressed over the struggles this year!

I don't think outright speed has been lacking. Reliability is the issue. And the Gordini may or may not still be above the minimum weight. If so, that of course will be improved with evolution as it's every bit as important as power---perhaps even more as it also affects handling and braking. The platform is good---refinement is even better.

As to Bricoop's question about running higher boost pressure without damaging the engine: I don't know the ASO rule on allowable turbo boost. They probably are at that boost level now. But assuming they were not, the answer is "maybe". Increasing boost takes a toll on all internal engine components. Turbo engines commonly employ more main bearings on the crank, heavier rods and bearings, heavier pistons etc. There is a practical limit to boost before the engine will not tolerate it. On many heavy diesels, like marine diesels from my background, going to higher turbo boost, or otherwise increasing the boosted air charge by inter-cooling or after-cooling is only possible within certain limits and requires different pistons and bearings. Years ago, some Indy engines (60 years ago!) ran variable rate turbocharged engines which were controlled by a variable pressure relief valve (pop-off). Some engines, like the later high horse power to weight ratio Volvo marine diesels, and some older Detroit Diesel 2 cycle marine engines employ both a turbocharger (exhaust driven turbo) AND a supercharger (mechanically driven compressor) in which the air charge is compressed twice. But the engine will certainly only tolerate so much boost before reliability is lost. During the Viet Nam war, the Navy had some river patrol boats that used turbo/supercharged Detroit Diesels----they simply threw tham away after a few hundred service hours!!!

Mark you are correct. The old detroit diesel marines were actually known or badged as gray marine.My father was a fuel injection/ rack specialist in the navy. But newer engines as for production don't use variable pop-off valves. they use VNT control which actually changes blade angle on the turbo for controlling boost. The company I work for does dyno testing of exhaust / catalyst systems and we run the shit out of our engines that you would not normally see even at race type conditions and our stock engines can run upward of 300,000 simulated road miles with no problem.

A diiference of only 16% at 10,000 ft and less difference every where else equates to 1 MPH at best.

Oil pressure issues?

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