The “Redneck Blower”, fact or fiction?

[J.D..]

Since this is my first post here on RDC I’ll better start by introducing myself. Late forties male, European but not French(Belgian to be precise), and involved in amateur and semi-pro motorsport since my late teens, and this both in rally(wrc style tarmac and gravel) and track(touringcars and GT’s). Apart from this I also have a big intrest in the Dakar(most WRC fans don’t really care for Dakar, they consider it to be a not very competitive adventure sort of event), and i found this site years ago when Robby Gordon started campaigning his Hummer, it was about the only place where i could find some info on the driver and the car. Since then i’ve been a lurker here, and even became very interested in American off-road and bajaracing. I’ve followed the last couple of Baja1000 live on my pc, included the wheaterman audio feed. And no, I stil don’t like TT’s or any other sort of racetruck(they just look wrong, must be a cultural thing i guess:-) )but those class 1 and 10 buggy’s are extremely cool. Up till now i never posted a message here because i didn’t feel that i could contribute much, there’s more then enough knowledge available here, and posting some euro insight to counter some of the misconceptions here never seemed worth the while. Others sometimes try to put some things in perspective(e.g. Mark Miller) and although most seem to respect his views, I often have the feeling that they dont take them into account very much.

Now about the “Redneck Blower”

Well, what i’m gona write here I figured out about an hour after hearing the RG got Dqed for plugging his in/deflation system into his engine inletsystem bypassing the mandatory airrestrictor.
The reasson i’ve waited this long is that i thought someone else would also come to the same sort of reassoning and post it here so i wouldn’t have to(writting in english is a slow and very tiring activity for me :-) )

Before i proceed please understand that i’m not saying that Robby cheated, i only want to discuss the fact that there’s more to this than first meets the eye.The one’s who could know(Fly??) have been very scarce in their info about Robby’s CTISsystem and only throw us a “red haring”, being that the air stored in the spare tyres is no more than a “mouse fart”, a fact i easily agree with.

Now let’s look in detail what a CTIS system really is. In the middle there’s some sort of manifold with valves and pressure regulators(manualy or electronicaly controlled), and on the one side this is connected to the tyres(only rears and spares as per ASO/FIA regulations) and on the other side there’s a pressure source(compressed air bottle and/or compressor (12volt or enginebelt driven)).The rules allow for a 15liter(0.53 cuft) bottle, a 300bar(5000psi) bottle can thus contain 4500liter of air(159cuft). Checking some simple compressor specs i found that a 1hp compressor delivers 100liter per minute, a 2hp compressor 200liter per minute, you figure out the rule of thumb yourselvesJ. This means that a 1hp compressor can fill this bottle in 45 minutes, or 22.5 minutes in the case of a 2hp one, and so on. But how much can one do with 4500liter of air? The stoichiometric air-fuel ratio for petrol is 14.7, this means that for a given mass of petrol you need 14.7 times that mass to burn or combust the petrol. Now some simple math. 1 Liter of petrol weighs 711 grams, so you need 711grams times 14.7=10,452grams of air to combust this 1 liter. The weight of air is approx 1.2 grams per liter. 10,452/1.2=8,710 liters of air needed to combust 1 liter of petrol. Well, in the light of that, 4,500 liters doesn’t look that much, just enough to combust ½ liter, a little more than a “mouse fart’, a “horse fart” maybeJ.

Or is it?

Please note that what I’ve written up till now is just simple facts and fysics, it describes what the rules allow for and the math and fysics of combustion. What follows now is not “fact” it’s just a little mental freewheeling,

Ideally we would have the flow rate numbers of the restrictor, we could then calculate how much air is used and how much “boost” could be produced by adding some extra air. Another way of knowing how much air can pas through the restrictor is if we would know what the max fuel consumption is because this will be determinated by the amount of air that is available to combust it. Since I don’t have these exact numbers I searched for some info on the size of his fueltank and how much distance or time this would allow for. But in al fairness it is almost impossible to determinate this exact number. So I base my case on the high number of 50liter per 100km, and also that the average speed on the special is 120km/h. This results in a fuelconsumption of 1liter per minute. Please note that this is a very high number and that the real number is probably lower, and that the lower the number gets the bigger the described effect will be. In the case of 1liter per minute you would thus need 8710 liter of air per minute, the 4500 liter bottle would thus allow you for a 10% boost for a duration of a little over 5 minutes, or 20% boost for about 2.5 minutes, or… With a 1hp compressor you could refill in 45 minutes resulting in a 10% boost for about 10% of the time, a 2hp compressor for a 10% boost for about 20% of the time, and so on…. Imagine the availability of this sort of boost during the last couple of miles to a 12000ft summit, or climbing one of those gigantic dunes?


Now how do I quantify the “advantages’ that such a system could generate? Well, this is a sport where hundreds of thousands if not millions of dollars get spent to find an extra couple of seconds over a 500km stage, so you tell me?


To end. Like I said, I don’t know if RG did it or not, even more I would rather not discuss that in this thread. And what about ASO first allowing it and then dqing him for it, well, that to could be a very interesting topic for another thread. The only thing I wanted to say is that plumbing a ctis into the engine-inlet, bypassing the airrestictor could be used for more than simply using the vacuum there for faster deflating tyres. And btw, if I wanted vacuum for deflating I would rather use a simple vacuumpomp(as used in diesel-engined cars for the brake booster) anyway.


Regards,

J.D.

PS. Please excuse me for my bad spelling and grammar, I live in a country with 3 official languages so English is only my 4^th.

[SPONSOR]

Membership in the largest desert racing community has its advantages - Participate in Forum Discussions - Send and Receive Private Messages - Maintain Public Photo Albums - Access to Groups - User Profile in our Social Network - Increased Access to more Sub Forums - Reduced Online Advertisements Join our community today

[randy s]

i thank you for your input and i'm not smart enough to question your points you brought up. but i do know that the aso should never have approved the design in the first place after it was submitted to them and to come in only after rg won a stage with this is chicken chit. i also apologize for my misspelled words but if i spell chicken chit correctly i face being DQed on here. welcome to rdc...

[wessen]

amai, das nen helen boterham...

[J.D..]

amai, das nen helen boterham...

Goh, valt wel mee:-) het int engels uitleggen is het moeilijkste deel...

[randy68]

They talkin 'bout you randy...Hmmm??? Ha!

[J.D..]

They talkin 'bout you randy...Hmmm??? Ha!

Not really:-)

Just some local "patois" between Belgians.

[randy s]

let em' talk..i got some pretty thick skin on me. i've been a purple section member for quite awhile now. ja ja

[randy s]

and i apologize for any mistakes in spelling here by yanks in english because it's our third language now as well after spanish and vietnamese....fourth, if you count arabic.

[wheeli]

The waffle guy makes some good points. Its all sh!+ head nassers fault......grrrrrrrrrrrrr

[Ferrari333SP]

Hahaha, waffle guy. When I was in Brussels for a few days back in 2008, I had myself some waffles, and they were quite delicious.