That'll buff right out.

[HeroHog]

Aha!  Suddenly it all fits together, and thank you!  Wiki should have said it like that.  Maybe somebody ought to edit that passage I quoted.

Bear of very little brain happy now, Christopher Robin!

Terry

Too bad the ratio is 1:7 for nitromethane, not 1:1...

[230RN]

^ Even at 1:7, Brimic's "IIRC" still makes more sense, but thanks for the "update" on the number.

Besides, I think the 14 to 1 for gasoline is for a "normal" automotive mixture, but you can run richer.  Same is probably true for nitromethane.

But at this point, the concept I couldn't grasp is now clear to me.  (Thanks again!)

Terry

[dogmush]

Too bad the ratio is 1:7 for nitromethane, not 1:1...

1 POINT 7:1.

That decimal is important.

[griz]

I am searching for and can't find this great demo video of a top fuel blower and injector setup that shows you just how much fuel is being dumped into a top fuel car. AMAZING volume!

I think I've seen that.  Even without the vid, it's enough to know that top fuel cars don't do miles per gallon, they do gallons per second.

[HeroHog]

1 POINT 7:1.
That decimal is important.

Drat these old eyes!

[HeroHog]

I think I've seen that.  Even without the vid, it's enough to know that top fuel cars don't do miles per gallon, they do gallons per second.

They have 2 sets of 8 injector nozzles, 4 above the blower and 4 at the intake ports just before the cylinder heads. There is a vid showing the flow for one cylinder and it is pretty impressive:
https://www.youtube.com/watch?v=xGTbQuhhluY

[230RN]

Wow.  Just wow.

One of the followup youtubes to Herohog's link provides a more detailed view of the whole game.  Jeeze, 800 HP of "parasitic" power just to run the blower... =  !

https://www.youtube.com/watch?feature=player_detailpage&v=-VF0JwxQqcA

Pretty jaw-dropping.

I didn't catch on to the business of changing the ignition timing to enhance the grip of the tires on the track...?  (Narrator's remarks following ~2:09.)

Terry

[French G.]

Not a drag racer, but been around it a bunch. Consider that the fuel charge of the cylinder is about 70% liquid at compressed volume. Much more and they would hydraulic. Look at the pumping going on out of the header if a cylinder drops. And typically it does not light off. The top fuel cars used to blow motors and they didn't know why, turns out the G-load from the launch was working on the fuel in the lines and causing massive changes in the fuel delivery curve. One of those won't see it on the dyno things.

Doug Kalitta did a typically excellent job on that one, look first where his butterflies close, then where his chute starts to deploy. Then go watch the video to see how fast it really was.

[HeroHog]

They also had to put an "S" bend in the main fuel feed line to prevent fuel starvation after the burnout and reversing to start the run.

[zahc]

I thought that electronics were banned from top fuel, but in the video they were using electronic ignition and clutch management. Has it always been that way?

[dogmush]

  No, electronics are pretty  common in Drag Racing. It's all pretty much fuel injected with electronicly controlled ignition.

[HeroHog]

Electronics were eliminated from traction control systems a while back but allowed in data acquisition. They changed to using pneumatics and mechanical means for clutch and fuel management IIRC.

[230RN]

^ "They changed to using pneumatics and mechanical means for clutch and fuel management IIRC."

Yeah, I noticed in that vid they used a centrifugal system for engaging successive clutch plates.

I'm still not clear as to why they were changing the ignition timing to enhance the tire grip....?  (Reply #31 above.)

I'm sure I'll give myself a   when someone explains it.
Is it a workaround for this restriction: "Electronics were eliminated from traction control systems a while back but allowed in data acquisition...?"  So they're doing it by ignition timing instead?



Terry

CORRECTION:  Too late to modify the actual post.  I quoted  800 HP of parasitic power to run the blower.  It should be 600 HP.

[dogmush]

Changing ignition timing can lower HP and TQ at a given RPM, allowing the tires to grip, and then can be advanced again very quickly once the car is rolling.

[brimic]

Changing ignition timing can lower HP and TQ at a given RPM, allowing the tires to grip, and then can be advanced again very quickly once the car is rolling.

Yep. Make a new rule, the engineery types will figure a way around it really quick.
Some newer cars/motorcycles have the same feature- they have rev limiters (when the brake is pressed) or retard the timing to get the fasted hole shot possible.

[230RN]

^,^^
Aha, thanks.  All clear now.

[Fly320s]

Changing ignition timing can lower HP and TQ at a given RPM, allowing the tires to grip, and then can be advanced again very quickly once the car is rolling.

Those changes are programmed before the race?  Is that the "mapping" talked about in the video?

[French G.]

Ignition is the standard way to do traction control in most motorsports. Data acquisition would mean record only devices that did not change parameters on the car. If you have an electronic ignition you have traction control, or at least you should because there is really no way to prove it. FIA has spent millions just to pay people to analyze telemetry and they cannot find evidence of traction control in Formula One, so us mere mortals stand no chance. FIA has a solution, common ECUs that are supplied to all the teams.

How do you do it? For a given vehicle application you can predict what range of rates of RPM gain indicate full traction. Any quicker rise in RPM is wheel spin so the ignition pulls off timing.

[230RN]

 
Rules are made to be broken circumvented loopholed.

"They say you can't bolt Part A to Part B. So let's rivet them together."
 

This thread has been very educational for me.  I guess the real "competition" is in proving your engineering ideas.

Dumb Terry-like thought:  Is the rocket-reaction of the exhaust gases applied as downward* AND/OR forward thrust, or is that "just the way things are" and the thrust (there must be some, with those flames) is just not significant?  I mean, if you're throwing the combustion products of gallons per second out, there must be some use to which its thrust can be put.

TerrroooooOOAAARRRy, 230RN

*"Downward," as with the reverse airfoil on the back.

[HeroHog]

the Zoomie headers are directed for downforce in both rails and funny cars. The pressure from them will pretty much knock you off your feet. Even alcohol dirt track car exhaust is amazingly powerful, trust me on this. I know from close, personal experience on both counts!

The fuel system curves and ignition curves are set/mapped before the run based on telemetry data, track and atmospheric conditions.