DIY_EFI Digest Friday, March 26 1999 Volume 04 : Number 194 In this issue: RE: O2 Sensor Current? MAF GM systems Re: O2 Sensor Current? Re: Valve Overlap Re: O2 Sensor Current? Re: Valve Overlap Re: Valve Overlap Re: MAF GM systems Re: O2 Sensor Current? Re: Valve Overlap Re: MAF GM systems Re: MAF GM systems Re: List Topics... Re: MAF GM systems Re: MAF GM systems Re: Computer wanted to buy (cheap) Re: injector manifold design 454 TBI for 350 See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Thu, 25 Mar 1999 08:00:42 -0600 From: Thomas Martin Subject: RE: O2 Sensor Current? How would the ECM react or the O2 sensor react with a 1M from O2 sense to GND? I will look into the Op Amp circuit, probably best way. Has anyone on the list ever decoded the PROM on the 307 "Y" engine? Is there an older version of code with less part throttle spark advance? Can someone program a chip for me? I do not have a programmer that will burn the 27S181, I have contemplated adpating a different rom for it, I have one in mine, (don't remember it right off hand) but is is nearly pin to pin compatable, but has 2 more than the 27S181. I have a Data !/O 288A programmer. Anyone use one? It will not read my 27S181, anyone know how I can make it? My long term prject is to TBI this car, I think it would be a great running car with a TBI on it, or better yet, SFI. Thanks! Tom Martin 85 Cutlass Supreme Rocket 350 CCC > > > Date: Wed, 24 Mar 1999 22:45:19 -0800 (PST) > From: Orin Eman > Subject: Re: O2 Sensor current? > > > This is the standard way of telling if the O2 is at temperature yet... many > > systems will bias the sensor to .45 volts through a very high resistance (10 > > megaohms I believe). Once the sensor is at temperature, it does provide > > enough current to move the voltage away from the preset level. > > I seem to remember the bias resistors in my ecu were 768k. > The O2 sensor's impedance isn't _that_ high or you could never > get sensible results looking at it with a regular 1M impedance scope! > > I beleive it's in the 10 to 100k range when hot. > > Orin. > > ----------------- ------------------------------ Date: Thu, 25 Mar 1999 06:12:45 -0800 (PST) From: andy quaas Subject: MAF GM systems Is there anyone on this list that has adapted a mass-air GM injection system to a very different engine combo than the stock one? Frederic and myself want to use some type of MAF system on our large-cube engines. Anyone heard how its going on the gmecm programming list? Andy _________________________________________________________ Do You Yahoo!? Get your free @xxx.com ------------------------------ Date: Thu, 25 Mar 1999 09:25:41 -0500 From: "David A. Cooley" Subject: Re: O2 Sensor Current? Tom, A while back, Ludis posted a fix for reading your 27S181 on a standard prom burner and what was required to use a regular EPROM. It's on his web page: http://www.cruzers.com/~ludis/ - -----Original Message----- From: Thomas Martin To: diy_efi@xxx.edu> Date: Thursday, March 25, 1999 9:21 AM Subject: RE: O2 Sensor Current? >How would the ECM react or the O2 sensor react with a 1M from O2 sense to GND? > >I will look into the Op Amp circuit, probably best way. > >Has anyone on the list ever decoded the PROM on the 307 "Y" engine? Is there an older version of code with less part throttle spark advance? Can >someone program a chip for me? I do not have a programmer that will burn the 27S181, I have contemplated adpating a different rom for it, I have one in >mine, (don't remember it right off hand) but is is nearly pin to pin compatable, but has 2 more than the 27S181. I have a Data !/O 288A programmer. >Anyone use one? It will not read my 27S181, anyone know how I can make it? > >My long term prject is to TBI this car, I think it would be a great running car with a TBI on it, or better yet, SFI. ------------------------------ Date: Thu, 25 Mar 1999 15:25:51 GMT From: bob@xxx.com (Robert Harris) Subject: Re: Valve Overlap A little overlap on a turbo to blow some mixture into the exhaust where its burning will spin the turbo up faster. Might work - cept for the facts as reported by Dave Vizard, Corky Bell and countless others. The plain and simple fact is that the exhaust manifold back pressure is significantly higher than the intake pressure thru much of the region including almost all of the part throttle area. All overlap does is blow exhaust up the intake and give us EGR The better the design, the less this amount is - but for most of us it is a fact to deal with. Now if you want to spin the turbo up in a hurry, you might consider selective spark RETARD. Buick GN's do it all the time. By momentarily retarding the spark, say to 30 degrees after TDC, combustion starts way late and slow and the majority of the charge burns and expands in the exhaust manifold greatly increasing the volume of gas to spin the turbo which greatly increases the inlet charge ..... The result is very quick acceleration by exactly the effect that you want - blowing fire into the exhaust - without being defeated by the physics. And its on list topic. 1963 Ford C-600 Prison Bus Conversion "Home" 1971 Lincoln Continental 460 "Christine" 1972 "Whale" Mustang awaiting transplant 1978 Dodge Long Bed Peeek Up "Bundymobile" Habaneros - not just for breakfast anymore ------------------------------ Date: Thu, 25 Mar 1999 11:25:01 -0500 From: Ken Kelly Subject: Re: O2 Sensor Current? Tom, I have an 81 307 "Y". It is completely stock, but it isn't even EFI. It's got the Feedback Carb. I've never played with it, just been driving it since 85. I don't have a part throttle ping problem. Maybe you have too much static advance, carbon buildup, or are running lean. I need to look at mine, but I actually thought it still had mechanical advance in the distributor. I thought only the Vacuum advance was computer controlled. I could be wrong, I've only replaced the rotor and Cap once on that distributor. I agree the Feed back carb needs to be replaced, It needs rebuilt every 2 years, and I've about worn mine out, from rebuilding. Ken Thomas Martin wrote: > > How would the ECM react or the O2 sensor react with a 1M from O2 sense to GND? > > I will look into the Op Amp circuit, probably best way. > > Has anyone on the list ever decoded the PROM on the 307 "Y" engine? Is there an older version of code with less part throttle spark advance? Can > someone program a chip for me? I do not have a programmer that will burn the 27S181, I have contemplated adpating a different rom for it, I have one in > mine, (don't remember it right off hand) but is is nearly pin to pin compatable, but has 2 more than the 27S181. I have a Data !/O 288A programmer. > Anyone use one? It will not read my 27S181, anyone know how I can make it? > > My long term prject is to TBI this car, I think it would be a great running car with a TBI on it, or better yet, SFI. > > Thanks! > Tom Martin > 85 Cutlass Supreme Rocket 350 CCC > > > > > > > Date: Wed, 24 Mar 1999 22:45:19 -0800 (PST) > > From: Orin Eman > > Subject: Re: O2 Sensor current? > > > > > This is the standard way of telling if the O2 is at temperature yet... many > > > systems will bias the sensor to .45 volts through a very high resistance (10 > > > megaohms I believe). Once the sensor is at temperature, it does provide > > > enough current to move the voltage away from the preset level. > > > > I seem to remember the bias resistors in my ecu were 768k. > > The O2 sensor's impedance isn't _that_ high or you could never > > get sensible results looking at it with a regular 1M impedance scope! > > > > I beleive it's in the 10 to 100k range when hot. > > > > Orin. > > > > ----------------- ------------------------------ Date: Thu, 25 Mar 1999 09:30:13 -0800 From: Mark_Duewel@xxx.gov Subject: Re: Valve Overlap Bob- I remember watching the Zakspeed Capris blowing 3 feet of flame out the pipe right before they hit the apex. Same reason? - -Mark bob@xxx.com (Robert Harris) on 03/25/99 07:25:51 AM Please respond to diy_efi@xxx.edu To: diy_efi@xxx.edu cc: (bcc: Mark Duewel/Smog Check/DCANotes) Subject: Re: Valve Overlap A little overlap on a turbo to blow some mixture into the exhaust where its burning will spin the turbo up faster. Might work - cept for the facts as reported by Dave Vizard, Corky Bell and countless others. The plain and simple fact is that the exhaust manifold back pressure is significantly higher than the intake pressure thru much of the region including almost all of the part throttle area. All overlap does is blow exhaust up the intake and give us EGR The better the design, the less this amount is - but for most of us it is a fact to deal with. Now if you want to spin the turbo up in a hurry, you might consider selective spark RETARD. Buick GN's do it all the time. By momentarily retarding the spark, say to 30 degrees after TDC, combustion starts way late and slow and the majority of the charge burns and expands in the exhaust manifold greatly increasing the volume of gas to spin the turbo which greatly increases the inlet charge ..... The result is very quick acceleration by exactly the effect that you want - blowing fire into the exhaust - without being defeated by the physics. And its on list topic. 1963 Ford C-600 Prison Bus Conversion "Home" 1971 Lincoln Continental 460 "Christine" 1972 "Whale" Mustang awaiting transplant 1978 Dodge Long Bed Peeek Up "Bundymobile" Habaneros - not just for breakfast anymore ------------------------------ Date: Thu, 25 Mar 1999 13:25:36 -0500 From: "Bruce Plecan" Subject: Re: Valve Overlap - -----Original Message----- From: Robert Harris To: diy_efi@xxx.edu> Date: Thursday, March 25, 1999 11:03 AM Subject: Re: Valve Overlap >Now if you want to spin the turbo up in a hurry, you might consider selective >spark RETARD. Buick GN's do it all the time. Can I ask where in the program this is incorporated?. > >By momentarily retarding the spark, say to 30 degrees after TDC, combustion >starts way late and slow and the majority of the charge burns and expands in >the exhaust manifold greatly increasing the volume of gas to spin the turbo >which greatly increases the inlet charge ..... Wouldn't that be kinda hard on the exhaust valve?. Bruce >The result is very quick acceleration by exactly the effect that you want - >blowing fire into the exhaust - without being defeated by the physics. And >its on list topic. ------------------------------ Date: Thu, 25 Mar 1999 15:01:20 EST From: A70Duster@xxx.com Subject: Re: MAF GM systems Yes, I have. On a SBC TPI system. Using the HC11 as the controller. Had a problem with the MAF sensor. I've read in some GM manuals that the output of the MAF sensor is proportional to mass air flow. So I designed the system to handle a y=mx+b type equation, and had pots to vary m and b. And I had nothing but trouble. I could get a good idle, but poor mid and top end. Then I adjusted for top end and midrange and idle would be WAY rich. I finally flowed the MAF with an anemometer and behold Air mass varied as the square of output of the MAF sensor DOH!!!! So a little math fixed that. Mike ------------------------------ Date: Thu, 25 Mar 1999 15:04:15 -0500 From: "Gary Derian" Subject: Re: O2 Sensor Current? I think you will be in for a severe case of sticker shock if you try to buy a new carb for that. Gary Derian > Tom, > I have an 81 307 "Y". It is completely stock, but it isn't > even EFI. It's got the Feedback Carb. I've never played with > it, just been driving it since 85. I don't have a part > throttle ping problem. Maybe you have too much static > advance, carbon buildup, or are running lean. I need to look > at mine, but I actually thought it still had mechanical > advance in the distributor. I thought only the Vacuum > advance was computer controlled. I could be wrong, I've only > replaced the rotor and Cap once on that distributor. I agree > the Feed back carb needs to be replaced, It needs rebuilt > every 2 years, and I've about worn mine out, from > rebuilding. > > Ken > ------------------------------ Date: Thu, 25 Mar 1999 15:02:33 -0500 From: "Gary Derian" Subject: Re: Valve Overlap Porsche turbos did the same, I think it was from a very hot and rich fuel vapor finally finding some oxygen at the end of the pipe. Gary Derian > Bob- > > I remember watching the Zakspeed Capris blowing 3 feet of flame out the pipe > right before they hit the apex. Same reason? > > -Mark > ------------------------------ Date: Thu, 25 Mar 1999 13:13:04 -0800 (PST) From: andy quaas Subject: Re: MAF GM systems Please explain what ECM you used (home-grown?). What do you think of using a MAF system (OEM, lets say) on a 454 big-block or 431 mopar? Thanks Andy - --- A70Duster@xxx.com wrote: > Yes, I have. On a SBC TPI system. Using the HC11 as > the controller. Had a > problem with the MAF sensor. I've read in some GM > manuals that the output of > the MAF sensor is proportional to mass air flow. So > I designed the system to > handle a y=mx+b type equation, and had pots to vary m > and b. And I had > nothing but trouble. I could get a good idle, but > poor mid and top end. Then > I adjusted for top end and midrange and idle would be > WAY rich. I finally > flowed the MAF with an anemometer and behold > > Air mass varied as the square of output > of the MAF sensor > > > DOH!!!! > > So a little math fixed that. > > > Mike > _________________________________________________________ Do You Yahoo!? Get your free @xxx.com ------------------------------ Date: Thu, 25 Mar 1999 13:43:55 -0800 From: "Peter Fenske" Subject: Re: MAF GM systems Hi Mike GM uses tables to linearize the sensor.. IE take the MAF A/D or period and lookup the airflow in a table attributed to that reading. As long as you have the airflow figures this works good. Hard to do a polynomial in a HC11. Wondering if you had the airflow numbers and if you flowed the bosch analog MAf.. :peter CHOMP he MAF sensor is proportional to mass air flow. So I designed the system to handle a y=mx+b type equation, and had pots to vary m and b. And I had nothing but trouble. I could get a good idle, but poor mid and top end. Then I adjusted for top end and midrange and idle would be WAY rich. I finally flowed the MAF with an anemometer and behold Air mass varied as the square of output of the MAF sensor DOH!!!! So a little math fixed that. Mike ------------------------------ Date: Thu, 25 Mar 1999 14:57:45 -0700 (MST) From: d houlton x0710 Subject: Re: List Topics... Tom Sharpe wrote: > > > > eclark@xxx.com wrote: > > > I agree, this has bothered me since I started reading the list. I dont > > use a text based mail reader so html is useless. > > > > How do you look at web sites? please get an html viewer like netscape. > TomS > Netscape is a browser. It's made to view the html of web sites. If this were a web based bulletin board then Netscape would be appropriate. It isn't though, it's a mailing list. Use a mail reader and turn off html. - --Dan ------------------------------ Date: Thu, 25 Mar 1999 22:39:26 +0000 From: Frederic Breitwieser Subject: Re: MAF GM systems > Please explain what ECM you used (home-grown?). What do you think of > using a MAF system (OEM, lets say) on a 454 big-block or 431 mopar? I wish to second this polite request, specifically for 431 mopars - -- Frederic Breitwieser Bridgeport, CT 06606 http://www.xephic.dynip.com 1993 Superchaged Lincoln Continental 1989 500cid Turbocharged HWMMV 1975 Dodge D200 Club Cab (soon to be twin turbo 440) 2000 Buick GTP (twin turbo V6) ------------------------------ Date: Thu, 25 Mar 1999 19:08:29 EST From: ECMnut@xxx.com Subject: Re: MAF GM systems Frederic, if you have big cubes and twin turbos, could you put one MAF sensor on each turbo, have the turbos totally separate, say, each turbo pumping into the opposite bank from what's driving it, and make the ECM reference only one of the MAF sensors? Since the other side of the engine is the same displacement and (hopefully) running at the same speed, you could base your calcs on *half* the actual air flow, no? The other sensor is strictly for "decreational" pruposes.. Actually, it is to provide the identical restrition to the *real* unit on the other side of the engine. As I understand it, there aren't many *really big* MAF sensors that are easily adapted to the GM hardware, so splitting the flow duties out into a pair should work for high volume applications... What is on the Hummer? Thanks, MV > > Please explain what ECM you used (home-grown?). What do you think of > > using a MAF system (OEM, lets say) on a 454 big-block or 431 mopar? > > I wish to second this polite request, specifically for 431 > mopars ------------------------------ Date: Thu, 25 Mar 1999 19:44:35 EST From: EFISYSTEMS@xxx.com Subject: Re: Computer wanted to buy (cheap) Hi Dave, I've got one from I beleive a 94 lt1 T/A,,,,,,,yours for free if you want to share some info when you find out what you're looking for....... - -Carl Summers In a message dated 99-03-16 08:38:52 EST, you write: << Subj: Computer wanted to buy (cheap) Date: 99-03-16 08:38:52 EST From: dave_hempstead@xxx.com (Dave Hempstead) Sender: owner-diy_efi@xxx.edu Reply-to: diy_efi@xxx.edu To: gmecm@xxx.net, diy_efi@xxx.edu Hi, I'm working on my 95 ECM, and I need one that I can rip apart and do experiments on. There is a fair chance I'll break something in it, so I don't want to use the one I'm using to run my engine today. So.... I'm looking to buy a computer out of any of the following cars. 94-95 GM B-body (Impala SS, Caprice, Buick Roadmaster) with LT-1 engine 94-95 F body (Camaro, Firebird) with LT-1 engine If anyone has a line on one of these for a reasonable price, please let me know. It must work electrically, but not necessarily mechanically. Thanks for any help you can give me, Dave Hempstead >> ------------------------------ Date: Thu, 25 Mar 1999 20:02:44 EST From: AL8001@xxx.com Subject: Re: injector manifold design In a message dated 99-03-24 23:58:14 EST, StowT@xxx.com writes: >interesting, I like this idea. >I need to buy 2 injectors for this, are there any specific injectors that >have adjustable mounts or any that would lend themselves to this idea ? A injector with a hose on the fuel side would be easier to adapt. I've never heard of a factory adjustable injector. Harold ------------------------------ Date: Thu, 25 Mar 1999 21:53:38 -0700 From: cwagner@xxx.net Subject: 454 TBI for 350 I have recently acquired a throttle body for an 89 GMC pickup with a 454 in it. I plan on using it on a 76 Chevy 350 in a 1/2 ton 4x4. I don't know if I could use this throttle body using the bin for a 350 engine or not. Hopefully I will be receiving a programmer so I could reset some values but don't know what to reset to. I am certain that the injectors will flow more fuel than is needed during normal driving but will need that extra during WOT because the throttle body flows more air also. I could use some expertise on this project. I will be using the well known 7747 computer. ------------------------------ End of DIY_EFI Digest V4 #194 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. 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