240Z Headers

[kthomas]

Hey Steve:

What the engine needs is a needle shaped like a dowell pin, and an SM is definitely out. I think the closest unmodified was an N54, I'd have to go back to my notes. Doubt Sunbelt would let out what we really used.

We were anal enough early on to actually mount a camera pointed into the carb during dyno runs to see what the piston was doing. In stock form the SU's are pretty much slammed to the top by 4-4500 rpm at WOT, so the needle isn't doing anything. Part throttle like most street driving is an entirely different kettle o' fish, and contrary to popular belief there is no part throttle (i.e. no squeezing on the throttle, that's for wimps) when racing a Z in ITS, unless you're driving to the grid (or you don't have the chassis nailed down). So, to make the needle effective, and thereby maintaining something like an optimum AFR, you have to slow down the piston. Very tricky balance between restricting airflow versus optimizing AFR. The AFR will vary somewhat just by the velocity over the bridge, so it's not like you want redline to equal piston at the top. You can let it get there sooner than that. Cool, huh?

[JeffYoung]

So once you get the needle profile squared away, the work is in then in the piston springs and damper fluid?

On my car, my carb pistons are at the top of their travel VERY early in the RPM band. I am assuming based on the above that this is not a good thing?

[Parrish57]

Katman.....

Very Cool!! Thanks for the tip. If I recall, some of the video you shot of the carbs ended up on the Z Therapy tuning video. I've recently caught on to the concept that having the piston slam to the top quickly was a bad thing. I just haven't nailed down the ratio. Of course there is a reason for that- it's called work.. Perhaps you can help me with this equation:

Work x $=No time vs. no $=no race

It seems that when I go WOT at work I have plenty of money but no time to race much less development. Do you happen to know Wednesdays Lotto numbers?

Steve... On the road until the 22nd- Amsterdam, Frankfurt, Dubai, Shanghai, Baku, Frankfurt, Dubai, Dhaka, Dubai, Amsterdam, Philidelphia, Home (Charlotte)

[seckerich]

Hey Steve:

What the engine needs is a needle shaped like a dowell pin, and an SM is definitely out. I think the closest unmodified was an N54, I'd have to go back to my notes. Doubt Sunbelt would let out what we really used.

We were anal enough early on to actually mount a camera pointed into the carb during dyno runs to see what the piston was doing. In stock form the SU's are pretty much slammed to the top by 4-4500 rpm at WOT, so the needle isn't doing anything. Part throttle like most street driving is an entirely different kettle o' fish, and contrary to popular belief there is no part throttle (i.e. no squeezing on the throttle, that's for wimps) when racing a Z in ITS, unless you're driving to the grid (or you don't have the chassis nailed down). So, to make the needle effective, and thereby maintaining something like an optimum AFR, you have to slow down the piston. Very tricky balance between restricting airflow versus optimizing AFR. The AFR will vary somewhat just by the velocity over the bridge, so it's not like you want redline to equal piston at the top. You can let it get there sooner than that. Cool, huh?
[/b]

Good information KT. Did you find that you had to tune the dash pots with the springs and just use the fluid for damping the fast throttle hits? On our old GP and FP triumphs we used the jet size for the base curve and turned blank needles from there to fix the flat spots. We used a modified set of dashpot caps with indicators to check travel. Never found we needed the pistons all the way up until you had some long pulls. Great information you have shared--thanks.

[Ron Earp]

On my car, my carb pistons are at the top of their travel VERY early in the RPM band. I am assuming based on the above that this is not a good thing?
[/b]

Could be good or bad I think. I think it'll depend on how much air the motor needs and the diameter of the venturis, as well as some other things like the cross sectional area of the slide blocking the venturi.

I'm thinking of it this way - if you had say a 1/2 inch hole feeding half your motor you'd need that carb wide open quickly to provide enough air for the motor at any reasonable "race" RPM. If you had a 3 inch hole, well, opening the slide all the way straight away is not going to be good for power production.

In both cases the size of the hole will affect air velocity through the venturi and how much fuel is pulled up too. Looks like we need some time on the dyno!

Good info in this thread, nice when folks share and don't throw red herrings out all over. Thanks!

R

[lateapex911]

....

Steve... On the road until the 22nd- Amsterdam, Frankfurt, Dubai, Shanghai, Baku, Frankfurt, Dubai, Dhaka, Dubai, Amsterdam, Philidelphia, Home (Charlotte)
[/b]

OK, none of my business and all that, but what the heck do you DO??? Dubai THREE times? In the next week?? With 12 other stops around the world???? I hope you at least started this trip a bit ago! hate to see the bill for those flights!

Unless..............you're a pilot!? yea, that's gotta be it...right?

[kthomas]

Perhaps you can help me with this equation:

Work x $=No time vs. no $=no race

It seems that when I go WOT at work I have plenty of money but no time to race much less development. Do you happen to know Wednesdays Lotto numbers?
[/b]

That's a tough one. But I have figured out an equation for why my managers make more than me:

Time = Money. Knowledge = Power. We all know the derivative of work with respect to time is also equal to power. Or, Work/Time = Power. Substitute Knowledge for Power, and Money for Time:

Work/Money = Knowledge. Then solve for Money: Money = Work/Knowledge. Therefore, the smarter you are, the harder you have to work, or the less you know the more money you make.

[Parrish57]

OK, none of my business and all that, but what the heck do you DO??? Dubai THREE times? In the next week?? With 12 other stops around the world???? I hope you at least started this trip a bit ago! hate to see the bill for those flights!

Unless..............you're a pilot!? yea, that's gotta be it...right?
[/b]

Ding ding ding.... We have a winner! I fly a 747-400F. If I got frequent flyer miles I'd have enough for a round trip to the International Space Station. We do a lot of contract stuff for Emirates Sky Cargo so Dubai is like my second home.

I knew I should've stayed awake in Algebra class.

[Ron Earp]

Here you go, written up in the commonly seen Dilbert way as it appeared in the cartoon:

DILBERT'S THEOREM ON SALARY:

Dilbert's Theorem on Salary states that engineers and
scientists can never earn as much salary as business
executives and sales people.

This theorem can now be supported by a mathematical
equation based on the following three postulates:
Postulate 1: Knowledge is Power (Knowledge=Power)
Postulate 2: Time is Money (Time=Money)
Postulate 3 (as every engineer knows): Power = Work / Time

By substitution, since Knowledge = Power, Postulate 3 becomes:
Knowledge = Work / Time

and since Time = Money, we have:
Knowledge = Work / Money

Solving for Money, we get: Money = Work / Knowledge

Thus, as Knowledge approaches zero, Money approaches infinity,
regardless of the amount of Work done.

Conclusion: The Less you Know, the More you Make.

[DoubleXL240Z]

OK, so the way I see it is:
If I don't understand any of this!! I should be a millionaire at least!!!!
So, all I have to do is find the genius to give me all his money!!!
Whew!!! Why did I study in school???... Did I study in school?????

[lateapex911]

Dilbert is brilliant! And has no money.