Oh, oh, oh! Don't forget about me!

"Staggering the intake valve timing within the same cylinder with a
multi-valve head would allow at least one of the valves to remain
in the head's "sweet spot" a fraction longer."

Is that correct? See my last post for more details.

 

If you mean the point of maximum flow, you could dwell the valve(s) there for a bit as long as your valvetrain could handle the forces due to the high accelerations of the valve stopping and starting. We are approaching "square wave" valve motion here with it's nearly infinite forces. We won't even see square wave motion with solenoid actuated valves. Maybe we don't actually want it.

Instead, how about having each of the two inlet valves (DOHC)with different timing: One with low overlap and moderate lift which might be good for low to mid rpm range, and the other with more lift and duration for mid to high rpm range.

By having a port for each, you could close off the high rpm port until the engine reached a certain rpm and throttle opening (you wouldn't want both valves at high rpm cruising at part throttle), and then open the second port. Shoot, you could even switch that system off when you let someone else drive your car! Have an extra key required to get the high power. Call it a "Valet Key".

That's how the LT5 DOHC Vette engine worked about 14 years ago. It was a 350 that got about 405 hp in top form with all valves working. Of course the LS6 doesn't need all of that stuff to get about the same power. Perhaps ports and intake that flow well throughout the valve lift combined with valve motion (cam lobe) that takes advantage of the flow pattern is a simpler, and perhaps more elegant way to go.

You're not forgotten, Zero. Don't worry.
(Hey, you chose the screen name. )

 

I thought the valet key was used to block off the intake runners... although the valves were still pumping. Same effect though.

The cool thing I'm waiting for is this new "displacement on demand" GM's looking at. next year the GTO and vette get a tricked out dry-sump 6.0L they're calling LS2... but the real magic will be the Vortech's displacement on demand V8. Apparently this will be a hydralic control over the lifters in one bank and should be interesting for those that want street/strip motors... although I belive you'd have to stay with hydralic lifters/cam ... but get 30mph when limping around

Hopefully the 2007 Camaro will sport a dry-sump V8 like the LS2 but also incorporate displacement on demand. Hell that might even ditch the whole V6 option we're used to having available! Imagine having a single V8 for economy AND power.

 

Yeah, the system just kept air out of the secondary plenum/runners when engaged. Sure the valves kept moving, but it was like closed throttle operation.

DOD is for fuel economy at cruise and part throttle conditions. Half the cylinders are shut down (not all on one bank!) by not letting the valves open so no air flows, and of course no fuel is injected. The gain is mostly from fewer pumping losses, as the brake hp required (and fuel to produce it) for a given condition remains about the same. GM says 8% better on EPA testing and up to 25% in some specific conditiions.

Here's a pretty good explanation from PopRod.

DOD explained

DC is doing their version with the Hemi.

I can't really see much of a performance advantage, just lower fuel consumption. 8% better economy with $2.20/gallon gas brings it back to about $2.00/gallon effective cost. The time is ripe for DOD!

 

Here I thought the valet key was a rev limiter. Road and Track (I think)
did a review on the ZR-1 and I could have sworn the journalist
mentioned it was a rev. limiter?

Damn those uneducated wanna be techs!

Back to valve timing, my interpretation was WAY off. Here I'm thinking
one of the valves had an IVO of 38' and the second intake lobe
was ground in for 40' IVO.

Further to that, the second intake valve would have a more radical
closing profile to shut the valve within good time before the
compression stroke.

Figuring the centerline would be offset as well so that the average
of both valves would hang open slightly longer around the 0.400"
lift range to increase duration.

I guess having double the runner volume would kill torque and that's
why they chose to swap lobes and intake runners above a certain RPM.

Another kicker to my mad method, was the though that the LT5
was just a plain and simple DOHC without any sort of "V V T".

Once again I remember reading one cam controlled exhaust valves,
and one cam controlled intake valves per head.

We need to assemble a techincal team that weeds though all the
BS magazine articles and pulls pubic hair "one by one" from the
***** of the writers.

 

you go right ahead...

 

I don't mind the wading but we'll have to leave the pulling to those San Francisco boys.

-Mindgame

 

And with that response we will end the technical aspect of this
thread!

How about more cool tips about TF dragsters?

There is some sort of air scoop on the nose of the dragster just
about where the front wheels axle to the chassis.

This 'air scoop' is covered by a screen during the burnout, but taken off before the race.

What is this scoop for? I'm thinking it's a vent for the fuel cell?

 

Yep. You are right. It's open to the top of the fuel cell. Funny cars have one also, it's part of the front body latch. The latch is hollow, and it gets inserted into a hole (tube) in the front of the fuel tank. This is what keeps the front of the body down.

 

You failed to mention that VASCAR requires human input, and while it does have a margain of error for operator error, it can commonly still be wrong. I'll dig up an court case that describes this much further in depth and start a thread for it. However, when used properly without error, I agree, it is very effective, and very bad for the speeders out there.

 

Yes, you're right, it can involve human error, that is why our department used extensive field training/testing and actual use time to be able to be certified as a VASCAR user. This was brought up when this device was first introduced but that theory was quickly shot down. They did a study at the Indianapolis Motor Speedway involving the reaction time of flipping the switch and even people that had never used the device were able to accurately start and stop the VASCAR with great precision because you are tracking the vehicle to the "start" point and it is a lot easier than it looks. Also, the VASCAR unit gives the violators AVERAGE speed over a given distance. So, like many times, if you have VASCAR clock on a car for 2.3 miles and they averaged 98.3 miles per hour, even if you were off a little bit, the average will take care of the error, this has all been debated before and there is no affect on the speed. Actually, most Judges that I have seen, would take a VASCAR Clock over a radar any day becuase of the average speed being used not the peak speed, and they know that it works.

 

If you are going 98.3 mph for 2.3 miles the clock was on you for nearly 1-1/2 minutes (84.232 secs, right?) and you didn't see the cop pacing/clocking you, you desreve the ticket. If it's a "Bear in the air", you need to check the sky also if you are going that fast for that long! Cloudy days are nice for speeding on interstates.

We have officers sitting on an on-ramp shooting up your tail with a laser as you go by. That's tough to beat. Of course sometimes they park in the middle of an overpass so they can shoot easier, but you can see the parked car about a mile away, so that's usually not much trouble.

IMO, laser is a lot more work for the officer than radar. Instant-on Ka is tough to beat unless the car(s) in front of you are being shot, and you get a little stray signal. Any Ka brap gets my immediate attention. So does any Camaro in State Trooper livery! I had one blow by me (when we were doing 75+) with about 50 mph overtake. No lights, no noise. He was out of sight within a minute. Yeah, he got the out-of-state guy he was chasing, and had timed head-on a few miles back. Generally the Camaros are looking for the really over-the-limit folks.

Top Fuel thread has taken quite a detour, huh?

 

"Top Fuel thread has taken quite a detour, huh?"

Yeah, but it's all good an related material. Power = Speed, and Speed = Police

I wonder what would happen if the RADAR picked up a 330 MPH
signal? I'm thinking the cop would just laugh and put his feet up
on the dash...

Let's see, what else may I ask about these cars?

There's no cooling system from what I know. Alcohol and Nitro
like heat to help combust the mixture.

I have also noticed that there are EGT's on all the exhaust runners.

Is that all data collection, or are they allowed to adjust mixture
as they run down the track?

 

There's not much cooling that can be done in 4.5 seconds or about 600 total revs of the engine under load.

They record LOTS of data every run. It's interesting that they can use digital recording but must use mechanical timers for clutch control. No electronic controls, ASAIK. IF mixture/timing is adjusted, it's not a feedback system. I don't think engine parameters are adjusted during a run. Anyone know for sure?

Zero: question for you? Ever notice that the crew chief does something with a little (Allen?) wrench after the burn out and before the run? What's he adjusting? (no help from the Peanut Gallery). Second part of the question: What is/was the Peanut Gallery?

 

Something to do with enabling the second magneto. I believe
they only use half the ignition during the burn out.

As for the data collection, I wasn't sure if TF was allowed to adjust.

I know Pro-Mod isn't. They collect, download, view and then tweak
for the next run.

Interesting story. My friends and I have started up an automotive
electronic business. We talked to some techs from G-Force
Race Cars (Jim and Jon Salemi). THey let us into the trailer to view
the car data. We didn't know much about the graph, other than it
was measuring engine RPM vs. tire rotation.

They used this information to set their clutch pressure. A simple
little serial data bus which we could build for hundreds of dollars
cost them 10's of thousands. I hope that included the software!