LeonV

Well there you go! Why is he parting it out?

(in unison) Hi Alex! Welcome to the addiction!

I heard it in person, not sure if he has a video up anywhere. Maybe some of the other Bay Area guys may have more info.

Definitely interesting, SU-style carburetors are a simple yet ingenious design. They take the opposite approach when compared with your typical fixed venturi carbs, using one "jet" and varying the choke size instead of utilizing different jets (circuits) with a constant choke size.

That's incorrect. FWIW, for those unfamiliar with CV carbs, if the piston stays up you lean out the mixture. With more cross-sectional area velocity decreases, therefore deltaP decreases and less fuel is drawn from the jet. A sticky piston will surely stall the car out, you just have to figure out why it sticks. Make sure the dome screws are equally tightened and not over-tight. EDIT: here is one link describing the operation of SU carbs.

To add some more to the history aspect of this post, the first mass-market EFI system was the Bosch D-Jetronic in the 1967 VW Type 3. Mercedes used direct fuel injection in 1954 (300SL)!

The manifold you use has no effect on what the rest of the system does. That's a moot point. By the way, the results I posted are from a stock 240Z with stock exhaust manifold. If you have a long exhaust pipe hooked up to your manifold after the collector, you will be losing torque unless the pipe is big enough. What the headers will do is increase power over the stock manifold as they generally scavenge a bit better. There are dyno results on this as well. Exactly! No difference going from 2.5 inch to 3 inch. That means there is no loss of low end when going with a bigger pipe. Why does it matter whether it's a 2L or a 2.4L? How else can you analyze those results? I don't understand why you can't accept the truth that dyno testing lays out, running the same car, same dyno, and only changing exhaust diameter. As shown in many dyno tests that once you choose the proper size, you don't gain (or lose!) anything from going bigger. Well you do lose something going bigger than necessary, and that is ground clearance. Two data points? There are two curves generated, one with 2.5 inch and the other with 3 inch pipe. Plus, other dyno results point to the same thing. This is a heck of a lot more than "two data points." Two data points would be, say, torque at 4000rpm and 6000rpm. Yes, I agree that if we only had two points to work with then more testing needs to be done. But we have two dyno curves (large collection of data points) from the same car and dyno. I don't see why you or anybody else should still be in denial about this. I understand it is hard to accept something that is contrary to your beliefs, but this is hard evidence. If you can point me to valid dyno results that prove your point, then I will say that it may have some truth to it. But I have never seen results that show that, with everything else held constant, a smaller pipe makes more torque anywhere in the torque curve. I've discussed many aspects of engine design with a former Formula 1 engineer and he would corroborate the points that I am making, if that makes any difference to anyone. Yes, it's not a Z engine, but it's a 4-cycle engine operating on the same exact principles. I hate to be cluttering up this thread, but I hope that this is informative to at least one person so that I'm not just listening to myself talk (type?).

Not only do you get power in the top end with a bigger pipe, you get it everywhere along the curve. ITS guys with essentially stock engines run 3 inch pipes, they don't lose anything. Look at Tony's dyno results. Properly sized exhaust pipes will not lose any power, but the proper exhaust diameter for an engine is a lot bigger than people think. From Tony's example, proper diameter for his 2L engine were twin 2.5 inch pipes. This is for a 2L engine! Collector tuning is a completely different subject and exactly what I am getting at. Yes the exhaust does need to be a certain length, I'm not debating that point. This tuning is dependent upon valve timing, exhaust temps, and tube length. It is done by calculating the time it takes for pressure waves to reflect at discontinuities in the piping and return before the valve closes, effectively scavenging more gases than otherwise possible. The pressure wave reflection bandwidth is increased with a megaphone placed at the right spot in the system, thus expanding the rpms in which an extra scavenging effect occurs. Now, with a properly done collector for your system, you need to size an exhaust to go all the way to the back of the car and release the gases. This size is bigger than 2.25 inches on a 240Z as shown by many people that have actually dyno tested and compared results. Here is a dyno sheet from zhome showing a comparison of a 2.5 inch and 3 inch exhaust on an essentially stock L24 revving to 6500rpm. Notice there is no difference between the two. This means that the pipe has been sized correctly. Especially put your attention to the fact that there are NO low end losses when going to a bigger pipe. The Ford GT40 is totally different subject altogether and apples to oranges if you're trying to compare to a Z. The GT40 has a dual plane crankshaft, where the firing order is uneven (2 from one bank, then 2 from the other. In order to aid scavenging, it utilizes "180 degree" headers which switch the collectors into which one cylinder from each bank route to. Thus the pulses in the exhaust system were even from left to right, and the next cylinder that releases it's burned gases is scavenged properly. The L6 does not need this as it has one bank of cylinders which also fires evenly from the front three to the rear three.

This is all anecdotal evidence from your "butt dyno." There is no concrete evidence here. I'm not sure if you read that link, but removing the exhaust pipe will gain power! Look at TonyD's dyno test results in that thread. There's no denying actual proof. FYI, exhaust and intake tuning is done by pressure pulses, you can call them sound waves, it's really all in the thread I linked. I don't want to clutter up this thread, I just want to point out the myth and that people should not limit their exhaust diameter because of internet anecdotes. The smaller the diameter and the higher the velocity, the more frictional losses you have which equals a loss in power. OP, post up a vid when you're done, it should sound nice!

Ztrain is a complete troll. Look him up by searching, he starts arguments about everything and stubbornly thrusts his wowing intellect at everyone. It's funny, I resisted to comment before his last post, but I was going to say that he's just going to come back and say how right he is. There's no stopping it! Doradox, this is pure comedy! Oh look, here he comes again...

Not true, this is not documented to have ever happened and is just internet myth. People love repeating "backpressure" and "lose low end" but no one actually reasons why that would be true or false. Here is one thread that discusses this: http://forums.hybridz.org/index.php/topic/81941-exhaust-tube-sizing-i-did-your-arithmetic-for-you/

That's the one! It definitely is sweet sounding, especially with the triples.

If he's the guy with a sort of dark red colored Z and Wats, I know who you're talking about. That car looks and sounds fantastic!

My 260Z needs springs/dampers/bushings badly among other things! The 240Z is now sitting on jack-stands, patiently waiting for attention...

Check and clean your TPS and electrical connections. This is SOP with an engine that got wet and then doesn't accelerate. EDIT: Must've glossed over the part about the 280Z!

Same here, although they did not require the amount of compression that the stock ones did. I have heard of the Tokico springs not needing a spring compressor, but I have no experience with those.

Same here, never had a problem.

They're on sale. http://www.thezstore.com/page/TZS/CTGY/PSDC01C

Search TPS (throttle position switch), that is 99% likely to be the problem.

Yup, I got my mag lugs from Kragen (O'Reilly). Just make sure they're the correct thread and length. You want them just a little shorter than the width of the mounting surface so that the lug doesn't bottom out before clamping down the wheel. I brought one wheel with me to see how they fit before purchase.

Right, I didn't say that I did this to preserve the weatherstripping, but to protect the window glass. I'll be using new rubber when reinstalling.

I consulted Mr. Humble and took my time with it. I just used a thin scraper to cut out the chrome trim and then went around the whole window, front and back, until all the weatherstripping was loose. Then the window simply drops out. I took it out with the weatherstripping intact so I can store it without damage, per Humble's advice.

Yep, pull the valve cover and inspect the valvetrain for loose parts. I'm not getting where "valve float" comes into play here.

You really are never wrong are you... :stupid:

By the way, made a quick and dirty plot of hp vs. cc from data found here: http://www.simetric.co.uk/si_cc2hp_data.htm I used only the passenger cars on the list, so Ford Fiesta through Honda Accord. Plotting the displacement vs. hp you get the plot in the first attachment. The correlation is ok, but there are a couple of outliers as you can see. Taking out the two outliers from the data, you get the second plot. The data correlates a lot better. Keep in mind, this is using a relatively small sample size. There is a lot of dependency on the way the engine is tuned. But generally, I think that you can surmise from the data that there is a pretty linear dependency of power on displacement. I can go on and on, but it's a bit of a pointless argument at this point that has completely veered off topic... correlation.doc correlation2.doc