JMortensen

I don't think you necessarily want the "ideal", because a NASCAR style spoiler with a Gurney on it will probably make the most downforce but I think it would screw up the airflow on the bottom side of the wing and make it less effective. I'd use the 911 as the example to follow, because it has the long sloping tail like the Z. If you look at the Porsche (and the Vette for that matter), they have a fairly narrow spoiler that sits in the middle of the body. I think the reasoning may be tied in with something you said on another thread. You said you had flow separation on the bottom of the wing in the middle but not on the sides. Assuming that I'm right about the function of the spoiler under the wing, that it turns the airflow to make it easier for the flow to stay attached to the bottom of the wing, then that seems perfectly logical. Put a spoiler in the middle but don't extend it to the sides because the center is where the flow is the dirtiest and it's needed to make the wing work. If you're using it to try and pump air out from the bottom of the car, a bigger one is probably better. You could put little drips of oil on the leading edge of the wings all the way across to see how the flow changes just like they do on real racecars. I know they have some flourescent dye they use, but maybe a little food coloring or something might substitute.

Got pissed off at theorizing on the splitter/airdam combo for years with no resolution. Emailed Simon McBeath. Will let you all know if he responds and what he has to say...

I think I'm with you on this part. The underside of a Z is pretty dirty, we all agree there. I think the easiest solution is to not let air under the car as you said. NASCARs make a lot of downforce and they don't have undertrays, they just have airdams and fenders designed to suck air out of the engine compartment and a big spoiler on the back to balance it out. I've found stats like 1500 lbs for the old style cars, and this site says up to 1750 lbs for the COT. http://www.livescience.com/technology/070215_nascar_aero.html We don't know if this is a short track high downforce config, or a high speed config that is getting these numbers, but they're still at least marginally useful for a very coarse comparison to a Z car. Katz says that "aerodynamic forces such as drag and downforce increase with the square of speed. So if a car develops 100 kg at 100 km/h, the downforce is expected to increase by 4 (to 400 kg) at 200 km/h and to 900 at 300 km/h." He shows a formula to figure this all out on p.51 of his book Race Car Aerodynamics. While I do truly suck at math, I think that this equation would hold true whether one is using metric or SAE measurements since the scales are linear. The windtunnel testing shows a max total downforce of 108 lbs at 100 mph, so I think we could expect 440ish at 200 mph. We can compare this to the NASCAR figuring on ~1750 lbs at 200 mph, as this gives the most generous estimate in comparison to the Z testing. This means that we're falling WAAAAAY short of NASCAR's numbers, and they do what they do without undertrays, diffusers, etc. That's not to say that they aren't complicated, but I think that we can take some of their basic concepts and apply them to the Z and improve the numbers a lot. Combine that with some of the CFD testing shown in McBeath's book where a splitter was added to a NASCAR profile to see the change and you get some ideas about where to spend the time and effort. McBeath just added a 100mm lip in front of the airdam with literally nothing at all behind the airdam and showed a 10% gain in downforce. He says that downforce maxed out at 150mm but didn't quote an increase in terms of either percentage or force. He then added a diffuser that went back to the front axle (still completely ignoring what was going on after the front axle) and gained another 3.9%. Side note--If you compare the diagrams 4.11 and 4.14 and look at the blue section of low pressure behind the air dam and created by the diffuser, they look pretty similar. Maybe I stared at those pictures too long, but that is exactly where the airdam on the splitter idea comes from. Regardless, I think it's pretty easy to see that there are still BIG gains to be made while only focusing mostly on the top of the car, without getting too caught up in the more difficult work on the underside. Problems with the underside are numerous. Need to control the height in order to prevent the car from having variable downforce based on ride height and pitch, need to route exhaust so that it doesn't intefere with the airflow, need to do something about the control arms to keep them out of the airflow, etc. To an extent those same issues apply to wings and spoilers on top, but they aren't as susceptible.

I saw that through some mutual friends' Facebook pages. I'm sorry to see you selling it Alan, and I hope you still cruise by from time to time to help me extricate my head from my anus when necessary. I was pretty surprised because I'd never seen interior pictures of your car. Our cages are quite similar. I was happily surprised that we had come to the same solutions in a couple of places. Made me feel like I did the right thing. I hate to say it, but yours is just a little better thought out. I am still working on this dash project, just as usual not devoting very much time to it, I did figure out that my dash needs to be about 4" in front of where the dash bar is (one of those things that Alan's cage does better than mine) and so I need some sort of bracketry to move the panel back. I've seen clamp on mounts that just bolt to the dash bar, but I was thinking that I have some 3/4" square tube, so I could just weld a nut in the end of the tube and the weld the tube to the dash bar, and then use a couple simple supports from the top of the plate to the area right under the windshield. I also figured out that by moving the dash back, I have room for the HRP part, so that is back on the table. I bought all of my gauges and switches and I'm talking to someone here about laser cutting an aluminum plate for me which would be very similar to the HRP part. That is sounding pretty promising, but if for some reason it doesn't work out I'll have to still consider whether to cut the holes myself or to spend the money for the HRP.

Lots of racecars use both. Daytona Prototypes, LeMans type cars, just about every Porsche that has a wing on it has a spoiler underneath it, etc. I think the idea is to help get the air up from underneath the car headed in the right direction to help get more flow under the wing. I expect you could run more angle without stalling the wing, in a way similar to a dual element wing. Here is a Z car that has both: http://www.youtube.com/watch?v=7TwOBR5Yep8&feature=player_embedded DP: http://www.raw-foota...DP/6/6-1253.jpg Porsche: http://www.theautoch...066281.1-lg.jpg Vette: http://www.z06-corve...ette-C5R-06.jpg Splitter is probably the easiest solution to front end downforce. It's in free airflow so a little change makes a relatively big difference. I do think my splitter/airdam will be ugly and will look like the car has a hellacious underbite, but I also think it will work and will be less pitch sensitive than a regular splitter, even if it produces less overall downforce than a splitter alone.

There is a little bit of discussion about hogging the 44's out in the How to Modify book. That must be what he's talking about, but if they were bored out then the opening at the manifold side would be 50mm or thereabouts. That's quite the cool pile of parts you picked up. How did that all come together? (separate thread?)

If you buy a rebuilt master it's already in there, you don't have to mess with it.

If you buy a rebuilt master it's already in there, you don't have to mess with it.

Not sure what that means. Most of the carb bodies taper from the air horn to the manifold side as Tony said. The stock 44's have an opening on the air horn side of 48 or so IIRC. The size that determines if it is a 40mm or a 44 or a 50 is the manifold side.

ttodhunter, I just sent you a PM about a tire well I have sitting in my garage...

Agreed. Just swap the CV's unless you want the ratio from the turbo. I know the LSD turbos are 3.70 I would guess yours is also. Pull the cover and it will have a ring:pinion tooth count. Would be 37:10 for 3.70s. Stock you should have 3.54's. You will need companion flange adapters to bolt up the CVs on the wheel end as stated. Two options: http://www.modern-motorsports.com/catalog/product_info.php?cPath=32_53&products_id=56 http://www.modern-motorsports.com/catalog/product_info.php?cPath=32_53&products_id=46

Sounds like the reaction disk to me. Maybe it isn't sealing in it's spot in the booster. Regardless, I think swapping the booster would solve the problem, but I think the problem is the disk.

Care for some other suggestions? How about a big lip in front of the front wheels? That would create a bigger low pressure area around the front tire and should suck whatever air is in there without the ducting. Could do that front and rear. How about a little spoiler in addition to the wing in back? Would help to pull air out from under the car, and lots of cars use a spoiler and wing together, Or my air dam splitter combo thingy. I'd love for someone else to guinea pig that idea...

Thanks for the feedback. I'm going to try a 1.75" hole saw in a corner that will need to come off anyway and see how it goes. If it doesn't go well, I'll probably buy that prefabbed unit and hack it up to fit. The spindle on my HF drill press deflects about 1/4" as soon as you start to put any pressure on it, so that was my main concern with using hole saws. I wish they made a 5" unibit...

My 80 year old next door neighbor at my last house told me that one of her friends got a 240Z when they first came out and she used to love taking it around town. Go to a Porsche Owner's Club event and about 1/3 of the people there will tell you that a Z was their first sports car.

Choke tubes = venturis. If you remove the venturis from 44s they become 44s, which is the diameter at the exit hole of the carb. No change you make to the venturi is going to change the size of the exit hole. The venturis neck down the opening to speed airflow through the carb at low engine speeds. I believe Mikuni shipped most street bound 44s with 34mm venturis.

I have a MATCO set of taps and dies, and I've used it quite a bit and it's great. I bought it because the driver said MATCO would warranty it for life, unlike Snap-On if I recall. No regrets on my tap/die set purchase at all. Now my piece of crap MATCO 1/4" drive air ratchet on the other hand. That was a very expensive paperweight.

Might also want to search "differential clunk" here and over at www.classiczcars.com if the U-joint doesn't solve the problem.

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Got all my gauges, shift and warning lights and all the rest together now. I also have a 1' x 2' sheet of T3 aluminum plate .125" thick. Any suggestions on cutting holes in the thing? I only spent about $20 on the aluminum. Considering buying one of these instead, even though I know it will need some modification to fit in my car: http://www.hrpworld.com/index.cfm?form_prod_id=764&action=product The thing right now that is bugging me about doing it myself is cutting the gauge holes. Right now I don't have a hole saw big enough for the 2 5/8 or 5" gauges, so I'd have to either drill a smaller hole and open it up with a die grinder or go buy the hole saw. My Harbor Freight drill press sucks pretty bad, so that's making me think that carving up a pre-built unit might be the way to go. Anyone done this before and want to offer advice?

Just guessing here, but leaner equals hotter. I would also guess that the flame from ethanol is cooler than a regular gas flame, so there would be some offset there. That would not be my main gripe against ethanol. [deleted]

You're a little late to this party.

I think you'll get A LOT more bang for the buck from something that is out in the airflow like a wing than you will from a fender liner so a bigger/better wing might still be the best bet for the moment. As to fender vents, I've got some thoughts on that one. Plenty of cars try to force air out from underneath through an open area behind the front wheel. Everything from Spec Racer Fords to Pikes Peak cars do it. Is it worth the hassle though? What air are you trying to exhaust? If your trying to get air out and you have a really low airdam, it might be wasted effort. If you're trying to exhaust the radiators out the sides you need to cut holes in the walls in the engine compartment walls and run ducts from the rad to the wheelwell, and then run ducts to your fender vents then it makes sense to look at the potential problems there. If a car drives up next to your exhaust hole on the side of the car, this can seriously affect the downforce on your car. An alternative if the purpose is for rad ducting is to go out the top, this makes the ducts simpler and makes the car less dependent on clean airflow to the sides. If you want to vent the fenders, putting vents right on top of the fenders or behind the wheels or both will still work to pull out any air that happens to get in and would have less reaction to a wheel to wheel situation. I'm not sure if the Speelab Vette that I think you referenced by the builder's username on a different forum (http://www.hemipante...rdic%20Supercar) uses those vents for the radiator also, or if they just use them to create downforce. Test #13 in which the skirts showed an increase in lift were done with a BRE chin spoiler. My guess is that with a chin spoiler what looks to be 5" off the ground too much air was getting under the car, and that the skirts were trapping that air, increasing lift. None of those cars tested had a radiator duct that kept air from going around the radiator and under the hood and car. It may be that with a lower front end or less air getting under the hood or a diffuser in the back to pump the air through, that result might be different. The side skirts should have serve the function of keeping the low air pressure under the car separate from the higher pressure air outside. If you don't have low pressure air underneath the car, then side skirts shouldn't be used. With regards to the rear, I think there are a couple options. 1. Diffuser. Whether or not it makes sense to have a fully formed diffuser on a Z would have to be tested to find out. I think as has been pointed out in other discussions here and elsewhere, having a higher rear end with an upward slope from the rear axle area to the back of the car does help. 2. Cut the rear valence off the car entirely, NASCAR style. I don't think there is any doubt that this would have an effect, the question is would it have an effect great enough to justify doing it. 3. Put a bunch of holes in the bottom valence. I have pics of a Lotus Europa race car that has the whole back end swiss cheesed and a spoiler on the rear deck. I think it looks great and the car certainly hauled ass, but I remember posting it here and the reaction was not universally supportive if you get my meaning. Those addressed the rear of the car, but your average diffuser doesn't address the area behind the tire that you mentioned. I think maybe the idea there should be something like ZR8ED's rear fender vents or a big ol hole in the back of the fender like the California Z rear flares, or a protruding lip in front of the rear tire in conjunction with a good fender liner to try and suck air from out of the wheel well area. Again, it would be an interesting thing to try out at the wind tunnel and see what kind of difference it makes and whether it was worth the hassle.

Any rough idea of the difference in unsprung weight for the TTT setup vs the stock with welded coilovers?

No. Note all the part numbers are different: http://www.gordon-glasgow.org/lsd5.asp