Thread: For Don Shilady

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Just to keep in touch I note that in the last two weeks our family 2008 Impala has twice signaled low tires via the dash digital readout. Checking the pressure showed the first case had a pressure of about 14 psi and again today another tire registered 19 psi compared to the recommended 30 psi. I say this in view of the discussion above about tire pressure. It occurred to me that the temperature dropped from mid 70s last week to 40 F when I checked the latest low pressure. Let's convert those temperatures so we can use the Charles-Gay Lussac pressure equation to estimate the pressure change due to seasons.

75 F = 23.89 C = 297.03 Kelvin, approximately 297 K
40 F = 4.44 C = 277.59 Kelvin, approximately 278 K
Temperature difference Difference = 19 K

The Ideal Gas Law is generally good up to about 10 atmospheres (147 psi) so we can use

(P1)(V1)/T1 = (P2)(V2)/T2

and if we assume that the volume of the interior of the tire remains essentially the same we can cancel V1 = V2 and use (P1/T1)=(P2/T2). Thus if the pressure was 28 psi at 75 F we can calculate the pressure at 40 F as P2 = P1(T2/T1) so we find

Pressure at 40 F = (28 psi)(278 K/297 K) = 26.2 F for a difference of about 1.8 psi

The same sort of reasoning applies for the case of tires heating up upon use. Of course in a race situation small corrections are made for air temperature as well as altitude above sea level so in that case a car would be set up right at the time of the race. Now add to that the common experience of slow leakage of tubeless tires on older rims and it is my claim that unless I set the pressure of my tires exactly every day for the ambient conditions I can easily see a variation of +/- 1 psi at least and in particular the tendency without inner tubes will be to go to lower pressure when starting out cold and then an increase in pressure during the run of the trip. Thus I think I will still start out at 28 psi and allow for tubeless tire leakage and compensation for increasing psi during travel. Perhaps a future investment of inner tubes could reduce this variation but for now if I am within a degree F or two the exact psi value will mush out due to temperature variations. In the case of our 2008 Impala I think the larger effect is probably due to old rims because the tires are less than a year old while for my roadster the rims are circa 2005 so the same slow leakage is probably occurring. Even if I get inner tubes for both cars we see that the temperature variation will make an accurate pressure setting no better than to about 2 psi.

Now to another important topic, I have not received any suggestions as to how to reduce the size of the temporary file with pictures I have previous put on this forum. The posting procedure says they will be deleted after a short time but maybe the problem is that I am running out of memory on my laptop? If so I should delete some of the 25 that are on there now but how to do it??

Don Shillady
Retired Scientist/teen rodder

Aaaah, english translation, colder temperatures = lower pressures...............

.

You've got leaks. You can expect 1 to 2psig drop for each 10F drop in temperature, or between 3 a 6 psig for your 32F delta - Goodyear Corporate | Newsroom | News Releases | As Temperature Drops, So Does Tire Inflation

Originally Posted by Don Shillady

Now to another important topic, I have not received any suggestions as to how to reduce the size of the temporary file with pictures I have previous put on this forum.

Go to your settings at the top of the this page, scroll down to attachments, check the box at the right side of the attachment(s) you want to delete, scroll down to the bottom of the page and on the right side hit delete selected.

The posting procedure says they will be deleted after a short time

I believe you have confused this, I believe it says if the attachment is NOT used it will be deleted after 30 minutes.

Don Shillady
Retired Scientist/teen rodder

However, I believe you maybe right, it may be your laptop giving you trouble.

.

As far as re-sizing pictures.. a lot of computers come with the software already loaded that'll re-size most any picture.

I use the one that comes with Microsoft Office.. but you can do it with the "Paint" program also, even the program that I have for the printer can change picture size and shape.

But there are free programs available also, just google / Bing "picture resize software"...

30cabrioletbrake.JPG30Landaubar.JPG30cabriolet.JPG30cabrioletengine.JPGWell Let me try to post some pictures. Hey, it worked! There were TWO problems. Thanks to 36 sedan I was able to delete about 50 old photos from the apparent limit of 298 on my copy. Then there was also a 700 limit on my laptop so I deleted some pictures from that area. Now you can see a rare 1930 Ford Cabriolet being brought back to running condition by my neighbor Dick Ivey. The car is owned by a woman in Fredericksburg Va who wants to tour with the Model A Club. Dick had to replace a cracked head, plane down a warped exhaust manifold and replace the rear wheel cylinders on the 1948 Ford hydraulic brakes. Then he added a dash push button starter relay for her and will get the paint touched up. I saw the car a few weeks ago and it was a dingy mottled blue but Dick buffed the paint to a bright blue. Although this car needed some repair to be ready for touring it is a really neat older update of a Model A with 1948 juice brakes and what is now a refurbished engine with a new fan and a brand new radiator. Dick is rightfully sought out for Model A repairs from miles around and it is my good fortune to be able to see the cars he works on. Note that the Landau bar on the top is a real folding-hinged bar and this is a rare car! I have more pictures of this car but I have a momentary interruption while I am glad to be able to post pictures again. Now in edit mode I see that I took the engine picture while he was working on the starter relay and you can see the dangling yellow wire is not yet connected. The replacement head is the so-called higher compression police head but it still is only about 6:1 compresshion ratio. This is a "standard" conversion to hydraulic brakes using 1948 Ford backing plates and the placement of the master cylinder requires moving the battery to a new position in the engine compartment. The special advantage of the Cabriolet is that the top can fold down but the doors have wind up windows while the windshield posts are straight. This car has been in the same family for a long time and if it were mine I would never sell it either! In edit mode I call your attention to the modern 6V alternator in the picture of the engine. Does anyone have a picture of an A engine with a CRAGAR head and insert bearings on a balanced crank to go with the antique racer pictures earlier in this thread?

Don Shillady
Retired Scientist/teen rodder

Some new data for what it is worth. I was able to weigh my '29 roadster on a local digital scale and it showed exactly 2800 pounds with me sitting in it. I had my semi-annual medical checkup last Wednesday and weighed 212 pounds without shoes and the wad of keys I carry so I figure the driver weight was 215 pounds. That puts the weight of the car (with tools, spare gas and spare Prestone in the rumble/trunk) at 2585 pounds, about what I expected. Here is a site with specifications for the 1977 Z28 Camaro which lists a weight

http://www.automobile-catalog.com/ma..._z28/1977.html

of 3615 pounds for the 350 V8 with a manual 4-speed and a drag coefficient of 0.43. I have never been able to find a drag coefficient for any Model A but since the above Z28 specs list the mpg in the 11-13 range I guess my 16-17 is not so bad after all. The amazing thing is that the new V6 Camaros get over 300 HP and around 30 mpg!

Don Shillady
Retired Scientist/teen rodder

Took a nice cruise today to a car show with about 10 cars from my club, about 130 miles round trip. Going we went as a pack averaging 55 - 60 mph. Coming back I was a lone wolf, ran her 70 - 75 all the way home. Round trip averaged 14 mpg, running a HP 327 with dual quads and a 350TH. Considering I got on her pretty good coming home, 14mpg overall is pretty good, and I'm happy with that!

Not really amazing specs on the new V-6's, it comes from way better electronics and engine controls and electronic fuel injection! Look at the hp and fuel mileage on the new Vettes, Mustangs, Chargers, and other performance type cars and you'll really be amazed!!!! 400+ hp and mid 20's mpg is becoming quite common.

Never have seen a drag number on an "A", but I would imagine it's about the same as a barn door! That A has a lot of things just hanging out in the breeze rather then hidden behind sheetmetal!

Dave, take a look at

Directory:Transonic Combusion -- TSCi Technology - PESWiki

I think these high mpg values are due to supercritical fluid fuel injection, although a friend who has a 2007 Corvette only gets 23 mpg. Does anyone know of a kit or Edelbrock accessory to raise the compression and add a high pressure pump with special nozzles on an intake bored for nozzles to put on a small block Chevy?

Don Shillady
Retired Scientist/teen rodder

Don------your best bet for converting your ride to a more modern(not the most modern) set up would be an Lt 1 or Lt4 from 92-96 ---------

Jerry Thanks for your comments on what is your thread as well as mine. I will have to keep an eye out for some Corvette wreck for an LT4 but usually that is above my pay grade. I have had fun buying some parts and accessories for my '76 Corvette block where I have met folks way above my economic strata. I know it gives away ideas but if you look at the new one-design SBC heads in the combustion chamber (slide 18)

Photos: C7 Corvette V-8 Engine - Road & Track

you can see the direct injection port. "All that is needed" is for one of the aftermarket SBC head folks to change their casting to allow that threaded nozzel hole in the head and then add GM parts for the fuel rail and pump. Of course it is not that simple but adding the nozzle hole to something like Dart Iron Eagle heads would be a start. Ten years ago I looked at making a conversion for Model A blocks to use a Mopar 360 head and in spite of some similarities there would have to be a LOT of machining/adapting to make that set up work. Thus an adaption of direct fuel injection from a high pressure nozzle would have to be developed by a shop like Edelbrock. However considering the need for higher mpg and the millions of earlier SBC blocks out there it might be as "simple" (????) as adding the threaded nozzle ports to the molds for E-Street heads. Hey I am just a shade tree mechanic with a beer pocketbook and champagne tastes but I can dream! I recall a dragster using a Model A block with a homemade fuel injector system based on a windshield washer pump but that was a continuous spray with lots of droplets whereas the new injectors use supercritical conditions to avoid fuel drops. I am dreaming of something between simple sprays and expensive GM parts with a change in some existing aftermarket molds. I am just dreaming out loud so maybe someone else will pay for the development!

Don Shillady
Retired Scientist/teen rodder

Don,
You say ...."All that is needed..." knowing well that it's a total system that has had many years of development and engineering refinement. Diesels have used direct cylinder (as opposed to direct port) injection for many, many years, but with the increased volatility of gasoline and the relatively small gain in efficiency the costs of the other parts of the system have not made it economically feasible for wide use on gasoline engines. You're looking at fuel pressures in the 2000-3000psig range! It's not a simple "standard fuel rail" approach when you're looking at that range of pressure. More important than the pump is the precise feed forward/feed back control system that's required to provide the accurate injection of fuel to keep the A/F ratio right to guarantee no detonation while maintaining efficiency. Your run of the mill "FAST" ECU is not going to cut it!!

Like Jerry says, if you want to have benefit of a feature in that engine the viable approach is to find a wreck and buy the power train. This not the kind of thing that you're going to do in your garage from scratch unless you're planning on getting some very sophisticated machine tools and your garage is bigger than your house.

Yes Don an LT $ vet wreck is going to be very expensive, but a core engine package from a 92-6 Lt1 vet or a 93-7 Lt1 Camaro, firebird or even the Impala,Buick,Caddie wagons will give you a package that you can use your present exhaust, motor mounts, accessories on -----I think the best bet is the 96-7 engines as the package was the most advanced as far as emissions , ecm etc was concerned----------OBD 2-------


I still have some core blocks, intakes, etc and there are various cylinder heads out there besides the oem alum ones that are quite nice----lots of people don't like the opti spark but the only problem I've had with one myself is that it was in the way of where and how I wanted to mount the alternator-so------I took a bunch of intakes and machined for a weld in boss to use a distributor-------


In my 92 vet that I had for a few years-------total time and 28k miles-fuel economy averaged 21.6-21.7 tank after tank, and it ran super on about anything I put in it(gas was changing a lot around some cities(Chitown) in those years------The direct readout showed 28mpg at a steady speed of 100mph and the computer would shut off the fuel at 172 mph I think because of tire speed rating---------
I have a 96 version from a Detroit Camaro test vehicle in Robin's 3 window and I'm hoping to finish it this winter----also have 4 cam Lincoln, 392 hemi and 256 flathead to do for some other 33s besides the aluminum LS7 for the Cobra----


If I can help you in anyway, please let me know----------

Rodger, you are correct and I know I won't be able to do it but I am trying to offer a suggestion so someone can do it. I note that Combustion got a grant for $32 million to develop their prototype but maybe Edelbrock could provide the heads with direct nozzel ports and someone could collect GM/Corvette/Cadillac parts to set up the rest. I note that the TSCi page describes very fast piezo-switch injectors and the new process requires only a short duration burn due to the natural combustion of the combination of the supercritical fluid fuel with air O2 but the Corvette process retains the usual HEI spark as a sort of compromise and the Corvette/Camaro/Cadillac parts use higher compression than usual but still less than diesel C.R. TSCi suggests 13:1 for gasoline engines. All I am really saying is that with CAFE restrictions skyrocketing and Federal money for "Green Technology" the auto industry will pay attention to huge increases in mpg in order to save the ICE technology and supercritical direct injection may be a big innovation or maybe just a passing fad. I see in the new Corvette heads a tentative compromise in retaining a spark plug but moving in that direction so maybe hot rodding can adapt to the new idea? Of course the new Corvette heads have enlarged the valves and switched their order along with optimization of the chamber shape but maybe hot rod development of aftermarket heads only needs to add the nozzel ports on the block valley side? Probably any such aftermarket kit would be at the mercy of the TSCi purchase price for those fast piezo nozzle switches. Just bench racing here and dreaming while all the while paying for 17 mpg but of course it would take a long time to recoup an investment even for the Edelbrock EFI unit and even more even if mpg for a Chevy 350 could be raised to say 27 mpg. Even so it is interesting to try to learn what these innovations are if the ICE survives CAFE strangulation.

P.S. Just for fun (while I am watching leaves fall) I looked up the critical temperature and pressure of n-octane and n-hexadecane (cetane) rounded to three places.

n-octane: Tc = 564 F Pc = 361 psi
n-cetane: Tc = 840 F Pc = 209 psi

Thus the key to the TSCi supercritical injection method would require as little as 400 psi or say a pump with 500 psi pressure. The critical temperature is a more difficult problem and for gasoline the temperature would likely need to be over 600 F inviting fire hazard. Perhaps the special piezo-pulsed nozzels TSCI has developed has an electrically heated wire in it to provide heat in the absence of air so pressurized fuel can be heated as it is injected. Another consideration is that fast injection approximates adiabatic expansion which might provide some expansion cooling when entering a combustion chamber but with 13:1 C.R. that won't be much. Probably the pressure required is not difficult to reach but the temperature of the fuel has to be higher than the critical temperature for the fuel to be fully vaporized. The Critical Temperature is that temperature above which the substance cannot be liquefied no matter how high the temperature is.

After all this pondering I will say that Jerry has a good point that maybe I can find an LT1 engine from an Impala but then have to retain the emission controls. Another interesting thing about the 2014 Aluminum block is that it looks like the trans bolt pattern is still the same!

Don Shillady
Retired Scientist/Teen rodder