DIY_EFI Digest Monday, 16 December 1996 Volume 01 : Number 385 In this issue: Tapered intakes, port velocities etc. Part II Re[2]: oil pumps (not efi) Re: oil pumps (not efi) Re: DIYEFI FAQ SMTP import error #-12 re: Fwd: eddy current brake Fuel pump questions pulse and hold Re: ALDL converter Re: ENGINE TIMING Re: pulse and hold RS-232 Inverter RE: ENGINE TIMING See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: Todd Knighton Date: Sun, 15 Dec 1996 15:56:24 -0800 Subject: Tapered intakes, port velocities etc. Part II Todd Knighton wrote: Continued:> > Ford's 1960's four-cam V-8 also had huge intake ports, and > while it turned more revs than the Offy four-banger engines then > dominant at Indianapolis, it was no better than a match for > them. When given an early peek at the Indy Ford's cylinder-head > castings, I expressed the thought that its ports might be too > big. Ford's engineers were too polite to tell me how absurd > they considered my remark to be, but their expressions made it > plain. I was too polite to send them an "I told you so" note > after Dan Gurney sent one of the engines to Weslake Engineering > in England, where it's intake ports were made smaller and its > output got bigger. > > Ford's engineers were then vastly ignorant of the world beyond > Michigan's borders. They had no idea Harry Weslake and Wally > Hassan (who created the very successful Coventry-Climax racing > engines) had learned years before not to take too literally what > the flow bench said. They were narrowing intake ports to > provide nominal gas speeds in the range of 350 to 400 > feet-second, making good use of the fact that kinetic energy > packing air into the cylinders increases with the square of it's > velocity. > > Harley-Davidson's experience with the highly successful XR750 > should have kept it from making the big-port error in the > CR1000. Yet, that's exactly what it did: the VR's intake ports > were made so big, nominal intake velocity was down at 200 > feet/second, which may explain why it's proved sadly inferior to > engines that do not test nearly as impressively on the flow > bench. > > Grand prix car engines represent the pinnacle of four-stroke > development. Formula One's designers are spinning 3.0 liter > V-10 engines up to 15,000 rpm's and getting close to 800 > horsepower. Ford's GP Zetec V-8 is doing the same with 375cc > cylinders, which implies that it's possible to build a 750cc > V-twin that will make nearly 200 horsepower. > > Cosworth Engineering's Keith Duckworth was the creator of the > modern high-output four-stroke. Casting aside tradition, > Duckworth combined large-bore short-stroke cylinders with > narrow-angle valves and a compact combustion chamber. He didn't > originate the use of high-intake port velocities to ram-charge > cylinders, but he and those he's influenced now design for > nominal intake speeds approaching 450 feet/second. > > Of course, there's a lot more to cylinder gas exchange than > port velocity. But unless you've spent eons dragging air > through ports, manifolds, etc.,, at a flow bench, you probably > have no real understanding of what aids flow and what slows it. > If there is any rule for the inexperienced to keep in mind. it > is that everything a reasonable intelligent person should > intuitively believe to be right will probably be totally wrong. > > Take valve shape for example, these days typically an > unstreamlined disc on the end of a stick Your eye will tell you > the shape is horrible, an example of how we've fallen into > decadence since the days of those British power plants with > beautiful, deeply tuliped intake valve. Then you hit the flow > bench and find that the one with all the loveliness of an > overgrown nail better at all lifts. And then you repeat the > experiment with another port and find it responds better to a > tuliped valve. Some ports are like that, by virtue of slightly > different interior contours or different valve angles. > > Or you can try valve seating surfaces-maybe someday you can > tell me why sharp edges are better here than rounded ones. The > worst valve I ever tested was one I made the mistaken belief my > eye could judge how air would behave between the valve and seat. > I ground a valve head with a radius instead of a flat where it > seated, along with a similar-shaped grinding stone for the seat. > Testing this idea required tons of work, yet my streamlined > valve and seat combination was worse at all lifts than the > typical series of abrupt, sharp-edged flats. > > You'd think that getting the valve completely out of the way > while flow-testing ports would let the air really whistle on > through. But peak flow almost always occurs with the valve in > place, at a lift equal to about 30 percent of valve diameter. > And this is with a manifold and carburetor in place, and a > cylinder between head and flow bench receiver ( the cylinder's > adjacent walls can significantly influence flow around intake > valve heads). > > Multiple valves ( more than two per cylinder) actually offer > little or no real valve-area advantage. You can prove this to > yourself by drawing circles representing valves inside a larger > circle signifying the cylinder bore, Unless you fudge the whole > thing with unrealistic provisions for valve seats, clearance > around the valves, etc., the total for valve head areas is about > the same for two, three or even five valve layouts. The benefit > lies in the fact that total head area counts only at or near > full lift: at lesser lifts, flow is largely limited by the valve > seat ring area, really more a function of the total of valve > circumferences than area. Viewed this way, multiple valve > layouts are better, though only Yamaha has found any gain with > more than four valves. > > Air flow in ports takes paths totally unlike those you would > normally envision, unless you happen to have an abundant > knowledge of compressible fluid dynamics. In your imagination, > air may move in orderly lines of travel, with particles marching > along the roof of the port staying high, those on the floor > staying low, and all traveling in neat, linear streams. The > reality is a very different matter. > > When flow in a duct ( an intake port, for example) arrives at a > bend, it loses any semblance of orderly behavior. Particles on > the inside of the bend travel the shortest distance (offering > the least resistance to flow), so they tend to maintain speed in > the downward turn to the valve seat. But flow in the top of the > port slows relative to the floor, creating a large velocity > gradient. Pressure in a moving fluid varies inversely with it's > speed, so the velocity gradient creates a lower pressure at the > port floor than at it's roof. this differential causes air at > the sides to move upward and the midstream air to move down, > with the resulting flow stream made to divide into to > contrarotating vortices where the port bends. Add to this the > invisible "smoke ring" vortex forming beneath the opening intake > valve and you have enough disorder to confound even the best of > minds (or computers). > > Port and valve configuration (both shapes and angles) can > profoundly influence combustion efficiency as well. Jack > Williams AJS 7R made it's best power with an intake port shape > that compromised flow in favor of creating more combustion > chamber swirl and redirecting incoming fuel droplets away from > the cylinder walls. I am reliably informed that Keith Duckworth > has settled on the intake valves leaned 15 degrees from the > cylinder axis, and ports at 30 degrees from the valves in a > similar trade-off between flow and combustion. > > Intake flow influences combustion because both carburetors, and > fuel-injection nozzles deliver fuel in liquid form. The best > you can hope for is a fog of droplets small enough to stay > suspended in the air while evaporating; big drops are > centrifuged out of the air stream, splatting against the intake > port and cylinder walls, which is bad for power, fuel efficiency > and emissions. Fuel can't burn until it evaporates; if you have > raw fuel still trying to burn when the exhaust valve opens, it > goes out the pipe, wasting your money and polluting the air. > > My experience (not the final word on anything even for me) is > that the biggest improvement in flow from a change in port > shape- with the least port enlargement and resulting velocity > loss- is obtained by widening the port floor upstream from the > valve seat. Air likes to take the most direct route, and the > more you ease that route the better flow becomes. Shaving metal > out of the lower sides of the ports bend (making a D-shaped > cross-section, with the port floor on the flat side has in my > tests shown big flow improvements in sharply bent ports. > > Smoothing intake flow (thereby minimizing the turbulence of the > main flow stream) is best accomplished by making sure the port's > section area decreases all the way from the carb inlet to the > bend above the valve seat. The small diameter, high-velocity > section of the port needs only a slight convergence of 1.5 > degrees included angle, which doesn't sound like much. But a 12 > inch section of aluminum pipe taper-bored for a 1.5 inch inlet > and a 1.498 inch outlet flows better than a parallel-wall pipe, > and a lot better than air going from the cones' small end to > it's beg end. Sound waves love a divergent duct, air flow does > not. > > I'm not convinced that polishing a port's interior surfaces to > a mirror finish does anything but look good. The problem here > is that while we know there's a degree of roughness beyond which > flow suffers, we can't agree on the limit to which polishing > helps. One those rare occasions when I do porting myself, I > settle for a smooth but not polished finish. If I were in the > head porting business like my long-tie friend Jerry Branch, I'd > put a spit shine inside the ports and combustion chamber, just > as he does. The way Jerry does it, his customers never have to > wonder if the ports are smooth enough. > > Jerry has discovered that some ports flow better if he cuts > tiny slots across the floor of the bend upstream from the valve. > The slots apparently act as turbulence generators that energize > the air and make it stick to the port floor, following the bend > more closely. That's the theory anyway, though like so much we > believe about port air flow, it's arguable because air hides is > secrets behind a cloak if invisibility. > > In time, we will know a lot more about the details of flow in > and out of cylinder heads. For decades, researchers have used > smoke, pinwheels, dye droplets, etc. in their attempts to see > what air is doing. The water-anaolgy method, where water > substitutes for air and flow is made visible with fine bubbles > or aluminum particles, is still used in many labs. But the > growth of mystery-dispelling technologies has recently brought > doppler-laser metering and computer imaging to the field. Maybe > one day soon we'll learn why the things a century of experience > has taught us actually do work, and why others do not. > > ------------------------------ From: dzorde@xxx.au Date: Mon, 16 Dec 96 08:26:11 Subject: Re[2]: oil pumps (not efi) From my experience of high volume oil pumps, they are mainly used for racing applications. ie. when the crank is cross drilled, oil channels smoothed and enlarged, cam lube holes pressure controlled, etc all constantly running at high rpm's. In this case the extra volume of oil is needed to keep the top end from running dry. This is also one of the reasons for having a puke tank connecting to the rocker covers, it may just overflow. In most normal cases, the stock pump is fine, however placing a small washer behind the relief spring to boost the pressure a little bit is a good idea if the engine will redline now and then. Dan dzorde@xxx.au ______________________________ Reply Separator _________________________________ Subject: RE: oil pumps (not efi) Author: diy_efi@xxx.edu at INTERNET Date: 12/14/96 2:15 AM >I have been reading this thread over the last few days and feel >compelled to interject the following; > >It is my understanding that on a Chevy small block, it is not >recommended to utilize a high volume oil pump. This can cause the oil >to be pumped in a manner that will fill up the lifter valley while >choking off oil supply to the bottom end. The recommendation appears >to use a high pressure pump, instead. This would imply that there is, >in fact, a difference. > >John Oh, there is -- look in your Summit or Jegs or ASAP catalog. You can buy 'stock', 'high vol.', or 'hi-pressure' pumps. And I 'spect the onliest difference in a hi-pressure pump is the size of the relief spring (just like in electric fuel pumps). Tom Cloud ------------------------------ From: Ken Mayer Date: Sun, 15 Dec 1996 19:32:25 -0500 (EST) Subject: Re: oil pumps (not efi) On Sun, 15 Dec 1996, Stephen Dubovsky wrote: > >It takes a finite amount of time for heat to transfer from on thing > >to another. The greater the temp difference, the faster the transfer, but > >it is still a finite about of time. True. > Im not so sure thermodynamics and heat transfer agree w/ you here. I > imagine it might happen at SOME speed, but you would be pumping oil so fast > that it would be heating your bearings instead of cooling them... Also true. There seems to be a misunderstanding about how heat is generated in bearings. In a "plain" bearing, there is no metal-to-metal contact between the rotating shaft and the bearing. They are separated (ideally) by a film of lubricating oil. The motion of the rotating shaft generates a shear force in the oil film. The "friction" within the fluid is what generates heat. The amount of "friction" is measured by viscosity. Lower "friction" >> lower viscosity >> oil "flows" more easily. The reverse tends to hold for film strength. Higher viscosity tends to keep the moving parts separated under higher loads. That's why heavy grease, and not 5W15 oil, is used in wheel bearings. The result is an engineering tradeoff to select a viscosity that flows reasonably well but which can also maintain a reasonable film strength. Also, nobody mentioned that the circulating oil is splashed against the bottom of *very* hot pistons in order to cool them. Most of the heat in motor oil comes from contact with the hot pistons. As for pumping oil so fast that it would heat the bearings instead of cooling them, it would occur, but not at the rates the oil circulates in an engine. This effect is true high-speed friction. As an example, when air flows past the Concorde in supersonic flight, the skin of the airplane heats up so much that the length of the airplane increases about 3 inches. The skin temperature rises several hundred degrees above the ambient air temperature. During low-speed flight operations (takeoff and landing), the skin temperature is the same as the ambient air. Ken :-) (yes, I admit to being an engineer ) ------------------------------ From: "Robert J. Korn" Date: Sun, 15 Dec 1996 20:26:45 -0500 Subject: Re: DIYEFI FAQ This is a multi-part message in MIME format. - --------------411739A67B5 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit George M. Dailey wrote: > I'v been thinking about writing a FAQ > on the GM ALDL thing, but it will be a while before I do. I've been > collecting the posts on ALDL for about a year. I'll simply put them all I posted this message last month but never saw it come back. This is a rs232 to ttl level converter that should work for the 8192 baud ecm's. I used it a few times on non auto related projects. I haven't tried it yet on a car. You can delete the inverter if if you want a one way interface. The serial data would seem to be two way. The data line also goes to the ABS brake controller. I saw a thread about the possible interaction between the brakes and the ecm. According to the wiring in my car its possible........ - --------------411739A67B5 Content-Type: text/plain; charset=us-ascii; name="Xx" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="Xx" +-------------+ + +-----------|1 16|---+---o +5V (VCC) +| +| | === === +5V o-||-|2 MAX232 15|---+---o GND (card & RS-232) | | | +-----------|3 14| + | | o +5V +---||---|4 13| | | | | \ +--------|5 12| / 10K + | | \ GND o-||-|6 11| / | | | RxD o----|7 ---<--- 10|--------+----------+----o ALDL I/O | | |\ | TxD o----|8 --->--- 9|--------------| |--+ +-------------+ 1|/ 2 74LS07 (also connect to 74LS07, pin 7=GND, pin 14=VCC) - --------------411739A67B5-- ------------------------------ From: (No Alias Created)@xxx.au Date: 16 Dec 1996 12:32:38 EDT Subject: SMTP import error #-12 George M. Dailey wrote: > I'v been thinking about writing a FAQ > on the GM ALDL thing, but it will be a while before I do. I've been > collecting the posts on ALDL for about a year. I'll simply put them all I posted this message last month but never saw it come back. This is a rs232 to ttl level converter that should work for the 8192 baud ecm's. I used it a few times on non auto related projects. I haven't tried it yet on a car. You can delete the inverter if if you want a one way interface. The serial data would seem to be two way. The data line also goes to the ABS brake controller. I saw a thread about the possible interaction between the brakes and the ecm. According to the wiring in my car its possible........ ------------------------------ From: RABBITT_Andrew@xxx.au Date: Mon, 16 Dec 1996 10:53:06 est Subject: re: Fwd: eddy current brake a 1.8 litre 4-cylinder engine we're working on cranks at about 200 rpm average, but cycles between 150 and 250 rpm every 180_. at 1000 rpm WOT, the crankshaft speed is cycling between 950 and 1060 rpm, again every 180_. At 4500 rpm WOT, this drops to about 40 rpm peak-to-peak. so you can see why everyone is moving towards many-tooth encoders. Andrew Rabbitt From: (Jim Davies) jimd@xxx.ca:smtp Date: ## 12/13/96 08:04 ## On Fri, 13 Dec 1996, Matt Sale wrote: > 600 RPM is a typical V8 idle speed, but cranking speed may be more > in the 200-400 RPM range, FWIW, most engines have a cranking speed in the 100 to 200 rpm range, based on my observations on 'scope readouts during tuneups, etc. JD ------------------------------ From: "George M. Dailey" Date: Sun, 15 Dec 1996 21:38:42 -0600 (CST) Subject: Fuel pump questions Lets talk about fuel pumps. In specifc, the early model Datsun 280Z pump. This is a Bosch unit used on the L-Jetronic (and other) EFI systems. The standard DC motor with a roller vane pump type, mounted outside of tank. I had a leaking O-ring on the pump, so I took the four screws out and replaced the ring. Now the pump will run, but it will not develop any pressure (not enough to open the pressure regulator on the FI system). It's also a monster to prime now. Yes, I did mark the pump housing and assembled it back as original. Yes, I did reinstall the roller vanes. None of the check valves were stuck. I would just say that the pump is bad But, in the past, when ever I opened one of these pumps and reassembled it, it never worked properly again. What's the trick to servicing these pumps?? Last price check was ~$200.00 each. What other popular cars (American sold) used this external fuel pump? GMD ------------------------------ From: Charles Napier Date: Sun, 15 Dec 1996 20:52:31 -0800 Subject: pulse and hold Hi, I was wondering if anyone out there knows how to build a pulse and hold circuit for a chevrolet syle fuel injector? Thanks in advance Charlie ------------------------------ From: "Robert J. Korn" Date: Mon, 16 Dec 1996 01:41:58 -0500 Subject: Re: ALDL converter I cant seem to et this through. Last time got an SMTP error > > Here is a simple interface to convert logic level to rs232. It assumes > the > I/O pin is bidirectional. If you dont want that just remove the > inverter. > > This is used in some of my projects and seems to be the simplest > interface > to the aldl. You need Regulated +5v or you'll fry the ecm. Tweak the com > port > for 8228 buad and it should allow logging the data...... > > Look feasible ? As Always, proceed at your own risk......... > > --------------------------------------------------------------- > +-------------+ + > +-----------|1 16|---+---o +5V (VCC) > +| +| | === > === +5V o-||-|2 MAX232 15|---+---o GND (card & RS-232) > | | | > +-----------|3 14| > + | | o +5V > +---||---|4 13| | > | | | \ > +--------|5 12| / 10K > + | | \ > GND o-||-|6 11| / > | | | > RxD o----|7 ---<--- 10|--------+----------+----o ALDL I/O > | | |\ | > TxD o----|8 --->--- 9|--------------| |--+ > +-------------+ 1|/ 2 > 74LS07 > ------------------------------ From: Tuck Date: Mon, 16 Dec 1996 01:39:24 -0500 Subject: Re: ENGINE TIMING At 22:18 12/15/96 +0000, you wrote: >HI there > >Having read the articles I can tell you that the most common method used >now in europe for engine timing is the flywheel sensor with a missing >tooth in conjunction with a cam sensor. The flywheel sensor has in the >case of Fords 36 teeth with one missing. The sensor is in line with FWIW, the Mazda rotaries use a gear driven crank angle sensor that inserts in the same place as the dsitributor did on the older rotary cars (in the front housing on the endinge that also contains the gear/chain-driven oil pump). I'll bet that it wouldn't be too hard to adaptthe Mazda crank angle sensor to the distributor mounting on another car with some careful fabvrication. I think the output signl is pretty straightforward from the unit. They are also readily available from any 84+ fuel injected rotary car and practically bulletproff in terms of reliability. Justin "Tuck" Cordesman SOLID BRASS-> She was getting robbed and I was getting blown away... It's funny... these days the only sympathy I get is from a woman I tend to annoy and a would-be assassin. ------------------------------ From: Sandy Date: Sun, 15 Dec 1996 23:21:04 -0800 Subject: Re: pulse and hold Charles Do you mean 'peak and hold' style of injector? Sandy ------------------------------ From: Kalle Pihlajasaari Date: Mon, 16 Dec 1996 09:25:27 +0200 (sat) Subject: RS-232 Inverter Hi, > I posted this message last month but never saw it come back. > This is a rs232 to ttl level converter that should work for the 8192 > baud ecm's. Seen it 3 times now. > I used it a few times on non auto related projects. I haven't tried it > yet > on a car. You can delete the inverter if if you want a one way > interface. To keep the polarities of the signals the same you would have to have the same number of inversions in each path. The MAX 232 chip will invert both signals once. The 74LS07 device is NOT an INVERTER so you can use it any number of times in this circuit. It is just an open collector output BUFFER. As has been mentioned there may be 0 .. 12V on the signal from the ECU so one should add a bit of protection to the logic side input pin of the MAX232 which is intended for 0 .. 5V working. A series resistor of about 10kOhm should prevent random latchup and stuff in this application. It is likely that the output of the ECU is current limited in some way so you should not cause serious damage. Another alternative that MAY work is to use a level converter designed for use in connecting a CASIO BOSS or Digital camera to a PC. These cables are to be had for about US$25 or so. One guy in the US is selling them that you can see at the following adress http://www.ip.co.za/people/kalle/sirplus.htm#larry I have added the protection resistor to the diagram below at pin 10 of the MAX232. > +-------------+ + > +-----------|1 16|---+---o +5V (VCC) > +| +| | === > === +5V o-||-|2 MAX232 15|---+---o GND (card & RS-232) > | | | > +-----------|3 14| > + | | o +5V > +---||---|4 13| | > | | | \ > +--------|5 12| / 10K > + | | \ > GND o-||-|6 11| / > | | | > RxD o----|7 ---<--- 10|--/\/\/-+----------+----o ALDL I/O > | | 10K |\ | > TxD o----|8 --->--- 9|--------------| |--+ > +-------------+ 1|/ 2 > 74LS07 > > (also connect to 74LS07, pin 7=GND, pin 14=VCC) Cheers *<<<-| - -- Kalle Pihlajasaari kalle@xxx.za/ip Interface Products P O Box 15775, DOORNFONTEIN, 2028, South Africa + 27 (11) 402-7750 Fax: 402-7751 http://www.ip.co.za/people/kalle ------------------------------ From: "Bob R. McElroy" Date: Mon, 16 Dec 1996 02:13:19 -0600 Subject: RE: ENGINE TIMING - ---------- Justin "Tuck" Cordesman SOLID BRASS-> She was getting robbed and I was getting blown away... It's funny... these days the only sympathy I get is from a woman I tend = to annoy and a would-be assassin. - -------------------------------- Just curious about your sig-line. Do you think that nobody will = recognize those last two lines, or that everybody will recognize them? = I would guess that anyone who is a Clint Eastwood fan would recognize = that quote from the movie "In the Line of Fire" where Clint is a Secret = Service agent trying to protect the president. My personal favorite = line from that movie is when Clint tells says he doesn't like to get to = know the people he protects because he is worried that he would decide = they were not worth saving (not an exact quote. I'll have to watch the = movie again to get the exact syntax.) Strange though, I came in to work on Sunday night to find that I had 284 = email messages in my inbox since noon Friday. This is the only one that = I was interested in enough to respond to. Gotta go do some actual work = now after a couple of hours of nothing but reading email. Bob McElroy ------------------------------ End of DIY_EFI Digest V1 #385 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".