DIY_EFI Digest Saturday, 13 September 1997 Volume 02 : Number 317 In this issue: Re: carb vs. efi I understand Q-jets Re: carb vs. efi RE: carb vs. efi Re: OBD II - fuel trims (adaptives) L-jet over rich O2 meter schematics O2 sensor output Re: carb vs. efi Re: TPI Questions See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: bwmsbldr@xxx.com (Bill Williams) Date: Fri, 12 Sep 1997 15:56:41 -0600 Subject: Re: carb vs. efi Someone else out there has read Ricardo! - --- Bill in Boulder "Engineering as an Art Form" --- ------------------------------ From: Paul Tholey Date: Fri, 12 Sep 1997 19:33:52 -0400 Subject: I understand Q-jets >> There is a school of thought that the racers used to replace the >> Rochester QuadraJets with Holleys because they couldn't understand the >> QuadraJets! To be more correct the reason the Holley carb is used over a Q-jet is because the Q-jet has a single fuel bowl in the center to feed both the primaries and secondaries. Mechanical fuel pumps cannot keep this bowl filled, and electric fuel pumps that can keep an average carb filled run at a pressure that will blow past the Q-jet needle and seat, wich are only good to 7 lbs. The Holley has two fuel bowls, one on each end, which can be extended to hold even more fuel. Their needle and seats also hold 9 lbs. and can be replaced with ones that hold up to 12 lbs. I am not trying to start an argument, but there are people who subscribe to this list that run Holleys, and it is not because we can't figure out a Q-jet. Paul Tholey pft101@xxx.edu ------------------------------ From: TMatthe@xxx.com Date: Fri, 12 Sep 1997 21:01:20 -0400 (EDT) Subject: Re: carb vs. efi In a message dated 97-09-12 15:20:29 EDT, you write: > I've thought about this summore ... I guess my question, really, > is "why don't more top racers use efi (or do they ??)" ?? > Rules. Plain and simple. In the World's quickest street car competion (NMCA), one of the top guys runs EFI, (6.96 in 1/4 mile) but this year they added a 100 lb. weight penality for EFI cars. NASCAR- nothing them good ol' boys can't mill or drill. NHRA- only in cars that originally had it. Plus, the LT1's have been factored up HP wise, which places them at a disadvantage. Anybody remember about 15 years ago when ECM's started appearing on cars? Everyone predicted the end of hot rodding, but the smart got smarter, and the dumb got blown into the weeds. EFI has shown that you can have your hot rod motor, and live with it on the daily commute also (albeit a heckuva lot more money- this stuff should be 1/2 the price it is now...) ------------------------------ From: James Boughton Date: Fri, 12 Sep 1997 22:36:06 -0400 Subject: RE: carb vs. efi I can't help but reply to this. There is no way a carb is going to get close! Just to dispute the fact on his own grounds (I am not a drag racer) I recently read about a Pro Stock Firebird that decided to go EFI and was breaking records. As I mentioned I am not a drag racer, so I don't remember the guys name, but it was in one of those hot rod mags. The F1, IRL, CART, F3, F3000, and every other series where you actually have to drive the car uses fuel injection. I imagine that a carburetor will work at WOT at one rpm very well, but due to the intrinsic nature of the fuel/air vs. demand ratio (air flow vs. max. airflow) curve of a carburetor you will not get it right everywhere. I have no data on atomization of the fuel, but anyone who doesn't believe fuel control is important in a performance application is missing out on horsepower. The other advantage of fuel injection is that while all the carburetor guys are trying to get all of their cylinders to run the same fuel/air the EFI guys are figuring out better ways to make more power. I could dispute this all day long, so if the above items are not enough to be convincing let me know and I'll tell you more. Jim Boughton boughton@xxx.net engineer (with race engine development experience) like it really matters! - ---------- From: Tom Cloud[SMTP:cloud@xxx.edu] Sent: Friday, September 12, 1997 2:33 PM To: EEC-EFI List; diy_efi@xxx.edu Subject: carb vs. efi he'p me out here .... have a friend that's a died-in-the-wool Holley carb fan and thinks I've made a big mistake going to efi (I'm not racing) He's an engineer, has worked as a mechanic, owned a speed shop and raced for a number of years, so I regard his opinion. He argues that no top racer (NHRA is his game) runs efi. I admit that's probably right, but the reason isn't because it's not better, but rather that it's too danged difficult to change at the track .... what do the Formula 1 guys (and others) do ?? Like I say, he'p me here .... - he says he feels the carb gives better atomization -- and I can see that a constant fuel flow rather than pulsations might (though the pulsations are at high pressure) - the efi gives better fuel control, I'd think, though that may not be important for racing - clearly port injection gives better fuel distribution -- but, at 8 to 12 k does it matter ?? ???? anyone ?? Tom Cloud Just because you're paranoid doesn't mean they're NOT out to get you !! ------------------------------ From: "Joe Chiasson" Date: Fri, 12 Sep 1997 21:34:49 -0500 Subject: Re: OBD II - fuel trims (adaptives) James Boughton wrote: > I would be interested in what tool you are using to obtain the data you > see. It sounds pretty handy. Does it update quickly enough for you > to see the oscillations of the short term adaptive? This should be in > the 1-2 hz range, maybe a little slower at idle. The diagnostics tool is called the "New Generation Star Tester" manufactured by Rotunda for Ford. Basically any Ford dealer's garage will (or should have one), and possibly other up-to-date garages would. The tool updates pretty much as fast as the computer process its input and outputs. Using the previous example of closed loop acceleration from 55 mph to 65 mph you will see all the long term oscillations that would take you from -7% to -11%. The tool can sense short term fuel trims rapidly enough that you would probably miss seeing half the data. The tool is on the expensive side (I believe around $1500), fortunately I have one availble through my employer, thus using one of these for free makes it a whole lot better > What the long term or short term adaptives do at WOT is strictly up to the > software writer, and whether they are used at WOT is usually the result > of some big meeting where the guy with the most political clout decides > what he is going to tell everyone else to live with. Now, with OBDII I just > remember something. If you do repeated WOTs and lifts you will drive > a lot of hydrocarbons through the catalyst. If you begin updating your > adaptives before the catalyst has had a chance to clean up again the down- > stream O2 sensor will try to lean out the mixture. This may be causing some > of the problem you are seeing. If you try an extended cruise I would expect > the long terms to stabilize at some value and the short terms to oscillate around > 0. This vehicles eventually does settle down and the short terms do eventually oscillate around zero (from about -2% to +2%) under normal loads (i.e. 30-60%). The long term eventually settles around -7% under the above conditions. Will take your advice into account and do some more driving and see if I can not get to the bottom of this. > More and more this is sounding like piss poor calibrating and the parts are > all fine. Is there a particular drive problem that instigated this inquisition or > are you just curious? Believe me cars from the factory aren't necessarily > calibrated perfectly, my truck actually dies out if you go WOT rapidly while > it is still warming up. Remember, the auto makers can sell cars that drive > bad, but they can't sell cars that blow high emission numbers. Basically what instigated this whole situation was I had never driven a truck with the 4.6L in it before. Most people I had talked to concerning the engine told me that it was built to be in the same class as the Chrysler 5.2L. So in comparison I though the engine was very weak and seemed to lag on acceleration. We ran some compression and leakdown tests and found some outrageously (atleast I though being that it's a newer engine design) inconsistent numbers from cylinder to cylinder. This prompted me to put the truck on the diagnostics tool and voila fuel trims did not behave as I thought they should. Thus the question I posted to dyi. SO I GUESS I'M JUST CURIOUS. Thankyou, J ------------------------------ From: sjacobs914@xxx.com Date: Fri, 12 Sep 1997 23:08:07 EDT Subject: L-jet over rich Hello all, I am trying to get a 74 914 with L-jet thru emissions. And we are running rich, really rich. I have checked out every component of the system, they are all fine. But I have playied with the air flow meter. I notice if I hold back the plate physically I am running in the right ball park. Is there a way of adjusting the flapper so more resitacance from the spring is provided? I have not hooked up the CO2 meter yet, don't need to as much black smoke that pours out the tail pipe. It is a visual thing. Please help me with this one. Once past the test, this car wil be exempt then I will be build a new intake system and using a PEFI of homebrew. Also I am looking for information on someone building a direct ignition system. I have seen the stuff on the DTI-EFI web site, but I am looking more for a premade kit. Take care, Stephen Jacobs SJacobs914@xxx.com ------------------------------ From: "alex nicu" Date: Fri, 12 Sep 1997 20:20:33 PDT Subject: O2 meter schematics I'll try to add on my web page the schematics from my EGO ( air/fuel mixture ) meter(!!!) . My web page provider it's not working today (@xxx. Alex http://home.onestop.net/nalex ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com ------------------------------ From: "alex nicu" Date: Fri, 12 Sep 1997 20:24:19 PDT Subject: O2 sensor output Anyone thinking on using a microcontroller to make that O2 sensor output to be readable ? If you have any detailed info of the output , I can spend some time to implement an correction map , if this is posible . Alex ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com ------------------------------ From: "Robert Harris" Date: Sat, 13 Sep 1997 00:04:12 -0700 Subject: Re: carb vs. efi Seems to me, everyone is complicating shitting and trying to act mighty proud of it. What works best is a 100% vaporized, homogenous mixture as it enters the combustion chamber. What gets it there depends on too many depends to generalize. Take the lowly propane/CNG mixer for example. Does this off the shelf - specially with an oxygen feed back loop -- but the fact that the fuel is a vapor at any temp above -44 does help a lot. Timed Port Injection gives a mixture almost as good as a well tuned independent runner Weber or Delorto Carb, but offers the advantage of pret near self tuning and optimizing whereas with the carbs you need the patience of a saint and the luck of the Irish to even come close to being right. Continuos Injection Systems properly set up are very simple to work on and work very good but aren't "KooL" Given high enuff air flow velocity and the right fuel, pissing in the manifold works - witness AA fuel. What makes any of these methods work BETTER is a small computer that either closes the loop or makes tuning and tweaking the open loop doable or both. Try looking at the strengths of everything and adapting it. Example. TPI EFI is fine at low air flows and RPM, but gets complicated fast as RPM rises. The air flow sensor is biased toward more accurate low mid and biggerizing the injector takes away from low end controllability. Port injection gives fine control and throttle body gives much denser charges because the fuel cools the charge at the throttle mouth and more air flow. MAF tends to work better at low flows and MAP sux low but works fine High (according to posts on this list) Why not optimize a TPI for low mid throttle and load - use its advantages to the limit - using SMALL nozzles to be really right on. Then when the RPM and air flow is high enuff, CIS some fuel right at the end of the runners. Since the flow is fast and furious and highly turbulent, it all gets well mixed and you pick up the bennie of evaporative cooling with a simple system. Don't need complication when you have the RPM. With synergy like this, you steal the best of both ideas. Just my usual obnoxious 2 bucks worth of bull. "When some one gets something for nothing - some one else gets nothing for something " If the first ingredient ain't Habanero, then the rest don't matter. Robert Harris ------------------------------ From: "Robert Harris" Date: Sat, 13 Sep 1997 00:27:04 -0700 Subject: Re: TPI Questions Once upon a time Popular Mechanics or Popular Science or do it your self whatever had plans for a You too can build it steam engine based on an air conditioning compressor. Had this strange vision of picking up heat from intercooling, water, oil, whatever and converting it to work powering this engine - either coupled to the crank or driving accessories. Freon seemed like a nice working fluid back then. Never got around to building one and now have no clue where to get the plans. If the working fluid could "boil" might still be worth investigating and a "steam engine" would make a damn decent cooling system. And BTW I'm jealous. When I was pushing H2O a year ago I got my ass fried. I now wear asbestos pampers whenever I post. But now for the real number 2 in the fan, look at a GM 350 diesel - the one based on a gasoline block. Pick whole car up for peanuts. Insane thought. Drill head for snapover valve. Time pump so that injection snaps over at about 20 degrees after TDC on power stroke. Combustion's over - but massive heat. Make bo koo steam rat now. Peak gasoline pressure about 600 PSI at about 2000 degrees. Steam at 444 makes same 600 psi. Use all that heat about to be lost out the exhaust to drive the piston down as an open cycle steam engine. Use the diesel throttle regulator to control the amount of water injected. Mix machinist water soluble cutting oil with water and should have enuff lubrication and anticorrosion to have reasonable pump life. This would make Terry proud. Direct Cylinder Injection - only we use water to make the extra power. Of course I could just be puffing donuts from my - but then I have been know to do that too. "When some one gets something for nothing - some one else gets nothing for something " If the first ingredient ain't Habanero, then the rest don't matter. Robert Harris - ---------- > From: Bill Bradley > To: diy_efi@xxx.edu > Subject: Re: TPI Questions > Date: Friday, August 22, 1997 1:01 PM > > > > Bear in mind that water or water/methanol injection will exert a powerful > > > cooling effect on the mixture rather than merely diluting the mixture > > > with hot, inert, gasses. > > > Bill in Boulder "Engineering as an Art Form" > > > > Hey, that's my idea. :-) Unfortunately you have to alter the air intake > > to compensate for the fuel displacement if water is injected, and > > methanol has a lower available btu, not to mention air/fuel ratio > > compared to gas. > > Nope. The water or methanol replaces AIR, not fuel. The mixture > goes rich running water or water-alcohol injection. Unless you're still > running closed loop with the Oxygen sensor which will try to bring it > back to stoic. > > > it to drive a cooling unit, (like a propane fridge principle), to cool > > the air, and then jam as much air directly into the injector stream as > > possible. The rest of the air charge requirement is sucked up normally > > on the intake. > > I've considered the idea of a heat powered heat pump as a killer > intercooler design. The drawbacks are that there are two common designs, > one uses Hydrogen gas and Ammonia (not that namby-pamby 2.5% stuff that you > use to clean things, REAL concentrated toxic, corrosive ammonia). The other > system uses water and lithium bromide salt, much nicer, but has the annoying > habit of freezing when it gets cold... Both systems also dump more heat OUT > than you put in, so you have to have a decent cooling system for it as well. > > Bill > ------------------------------ End of DIY_EFI Digest V2 #317 ***************************** 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".