One of my friends blew up his 2000 Dakota 4.7 this past weekend. No, he didn't blow up his motor, he blew up his truck. A nitrous explosion in the intake shattered the plastic intake (throttle body is only held on by the cable now), busted the wiring harness, bent the aluminum tubing up, broke the fender wells loose, and, GET THIS, bent the hood up about 16" in the center as well as broke the windshield.

My point is, if the fuel is burnt in the cylinder, the piston travels down on the power stroke and expands the 600 psi exhaust down to 50 psi. The exhaust valve opens and the 50 psi is let down to exhaust backpressure (~20 psi on a turbo).

If the fuel is burnt in the exhaust header (or intake manifold), the pressure could rise to 600 psi or more instantaneously and not be able to escape quickly enough. The exhaust header (or intake manifold) is not designed for that kind of pressure. What would result is a very violent explosion of the exhaust header (or intake manifold).

Mike

 

The analogy was crude, but the point was there. The turbo is not designed to have explosions take place in their housings. Neither was Mike's buddy's dakota intake

 

My thinking on this is if you burn X amount of fuel you will have the same amount of burnt gases to get rid of. Sure it will push the piston down and the pressure will decrease, because as the piston goes down there is more volume to fill by the pressure created. But that pressure is still there, just over a greater volume. As the exhaust valve opens and the piston comes up all the pressure still goes into the exhaust.

 

Sorry, that's not how it works. When the piston travels down on the power stroke the pressure decreases, thus the high pressure is no longer present. The pressure is not there anymore.

The total mass is still there. But the same amount of mass entered the cylinder, for that matter.

The energy is transferred to the piston -> rod -> crank . . . So the exhaust has only about 20% of it's energy left when it leaves the cylinder.

Mike

 

The added heat is good.
You could run a really big turbine and still get ungodly amounts of boost if your burning Nitro.
Might want to use ceramic impellars.

They are currently putting more power to the rear wheels than they car harness. That's why they have blower underdrive limits and Nitro mix limitations. It's to dangerous for the fans and drivers to let them race unlimited. Not to mention the waiting on oil downs.

 

im still not seeing it engineermike, I guess we will have to agree to disagree on this one. I know I would not want the responsiblity of making one of these things go down the track. I wouldn't know where to start running one on nitro. I doubt any moving part would last very long on the exhaust side of an engine running nitro.

 

Some things are FACT. Other things are OPINION. I have to be very clear in my profession about what is FACT and what is OPINION. FACTs can not be disagreed with or proven false.

What I posted earlier is a FACT.

If you combust air and fuel, then expand it, it loses pressure and energy. When exhaust leaves the cylinder, it has been de-pressured and its energy has largely been taken away. The residual energy is sometimes used to spin a turbocharger.

If this were not the case, then you wouldn't be able to stand behind a running car, because all that combustion pressure and energy would be blasting out of the tail pipes.

If you combust air and fuel in the header before the turbo, it has no where to expand to, so the header overpressures and possibly bursts.

What part of this are you not understanding?

Mike

 

Here is my thinking on this, im not saying you are wrong. But take the intake and exhaust valves out of the equation. You ignite air and fuel with the piston at the top. That creates so much pressure and it pushes the piston down and since the volume becomes greater the pressure drops. Now what happens if there is no blowby or anything like that and push the piston back to the top.

Kinda like a shock

 

What makes a supercharger whine?

10. When it gets beat by a NA car.
9. When it wishes it was a turbo.
8. When it realizes there is no replacement for displacement.
7. When it gets beat by a N2O car.
6. When it is a powerdine.
5. When it is put on 4 cylinders.
4. When it isn't on an F-body.
3. When it gets beat by STS.
2. When it isn't on a fuel car.
1. When it realizes it is on a Mustang.



BBB

 

It's more of a 'push' than a 'shock'.

 

Wow this thread got hijacked like a ****! So gears make it whine them? OK good enough....the top fuel stuff is cool too


LMAO at BBB

 

I think I remember being told by the crew cheif that the fuel pump is 70 or 80 gallons per minute could be wrong it was a long time ago...thats a lot of freakin fuel and they make 6000 plus horse power, this isnt any race engine that you could slap a turbo onto or much less have an exhaust system for, it would most likely be blown apart. One of the drivers said when they drop a cylinder on one side it kicks over towards that side since there is less THRUST coming out of that sides exhaust, now I dont know how true that is but if youve ever seen them at night its not hard to believe. I honestly think anyting trying to be an obstruction to the outflow of exhaust on that motor would not be an obstruction for very long and IF it stayed on by some miracle probably melt very quickly.

On another note I think some of the reason why you wouldnt WANT a turbo on there is because in 4 seconds you wouldnt get all you wanted out of a turbo. With a top fuel motor they launch from idle because of how thier "transmission" works, (this is just what I was told by another crew member while in the pits) its called a cannon and its a very powerful hydraulic clutch of some sort that allows it to slip certain amounts at certain points on the track so it doesnt blow off the tires the entire way, its direct drive with usually a 2.9:1 or 3:1 rear end ratio... there would be no way to spool a turbo up off the line with something like that and as far as I know there is no other alternative to the cannon with that kind of power. With a roots you have instant boost which is important when you only have 4 seconds to make it so in this case a roots would most likely be far faster anyways.

 

A top fuel engine would have to be completely overhauled to accept turbos. You wouldn't run the same kind of fuel (unless the fuel cooling replaces intercooling) and you would need either 8 turbos, or a header of some sort, none of this one pipe per cylinder bullcr@p. Its a strange argument, because it would have to be changed so much to accept turbos.

Fuel Injection would replace the carbs, and you would need intercoolers. I think it could make as much if not more power, but in a very different way.

 

top fuel and funny cars are EFI not carbs... and really if you read the post I made above I dont think turbos would be a wise descision anyhow, like you said WAY too much stuff to change if that much exhaust and heat could even be captured without problems and maybe some stuff couldnt be changed like the cannon so you couldnt build boost off the line with the turbo like you could with the roots without burning the clutch up.

Plus the r&d would be astronomically expensive or dangerous, think about all the tuning that would need to be done, these motors are WAY different than a street motor you could just dyno not to mention what goes on inside them is totally different. All for what 4 seconds, they barely stay together for 4 seconds as it is think about how well it would need to be tuned and how many engines would fly apart trying to get it right $$$$$$$$$ they are 100k dollar motors

 

No they are not. They are MFI-Mechanical Fuel Injection.