The ECM doesn't get the 7th pulse. The 7th pulse is purely for the benefit of the DIS module so that it knows which coil to fire. The ECM only cares about one reference pulse per ignition event, which is what it gets from the pickup coil in the dizzy.

The reference angle, however, is different between the two systems.

quote Originally posted by Will: The ECM doesn't get the 7th pulse. The 7th pulse is purely for the benefit of the DIS module so that it knows which coil to fire. The ECM only cares about one reference pulse per ignition event, which is what it gets from the pickup coil in the dizzy. The reference angle, however, is different between the two systems.

I was just going to add that; but Will beat me to it. The reference angle Will is talking about here is the angle in relation to TDC the sensor reads the pulses from the reluctor wheel. DIS is different than a Distributor; and the computer has to be programmed to know this.

As I also said earlier, the dwell (charge) time for the ignition coil(s) differs greatly between single-coil (distributor) and multi-coil (DIS) systems.

I don't think the Fiero ECM can be reprogrammed to work with DIS; but even if it could, why would you want to use it when the 7730 ECM is so much better? (ie: faster processing, more memory, more adjustable tables, greater diagnostic capability)

-ryan

yup, the Fiero referance twists with the distributer, while the crank trigger is fixed
and, yes - the 7730 swap way to easy to NOT use it.

quote Originally posted by Darth Fiero: As I also said earlier, the dwell (charge) time for the ignition coil(s) differs greatly between single-coil (distributor) and multi-coil (DIS) systems.

I thought that the DIS brick handled the dwell for the DIS coils, since dwell for them is greater than one spark interval, unlike the dizzy system. In the dizzy system, one signal from the ECM can control both dwell and spark timing (module charges coil when timing signal goes high, sparks when timing signal goes low). In the DIS, each coil is charging for multiple ignition events before required to deliver a spark, so one signal can't control both... hence I thought that the DIS module handled dwell. Is this not the case?

quote Originally posted by Will: I thought that the DIS brick handled the dwell for the DIS coils, since dwell for them is greater than one spark interval, unlike the dizzy system. In the dizzy system, one signal from the ECM can control both dwell and spark timing (module charges coil when timing signal goes high, sparks when timing signal goes low). In the DIS, each coil is charging for multiple ignition events before required to deliver a spark, so one signal can't control both... hence I thought that the DIS module handled dwell. Is this not the case?

I didn't think spark dwell would have been handled by the computer either until I got into some of the programming used in OBD1.5 and OBD2 systems. There are quite a few tables in there for spark dwell time in these newer systems. I haven't found any in the code masks that are used in the 7730 ECM but they are in there for OBD-2 operating systems that use the same ignition module/coil pack (3100 & 3400). But then again the dwell time could also just be a fixed value in DIS-compatible code masks; something written directly into the operating system and not the calibration.

quote Originally posted by Will: I thought that the DIS brick handled the dwell for the DIS coils, since dwell for them is greater than one spark interval, unlike the dizzy system. In the dizzy system, one signal from the ECM can control both dwell and spark timing (module charges coil when timing signal goes high, sparks when timing signal goes low). In the DIS, each coil is charging for multiple ignition events before required to deliver a spark, so one signal can't control both... hence I thought that the DIS module handled dwell. Is this not the case?

me too. but, the reason I thought that was because awhile, the Fiero store sold some "performance" ignition modules, and one of the changes they made in them was the dwell. and, being the DIS module & the Distributer igntion module do the same job, I expected the dwell to be controlled on the DIS module.

Someone from the 60*V6 forum just replied to a question I had about the external crank trigger working with our 2.8's and he/she responded that it might work not due to our Fiero pulleys being like a RWD and different than a FWD setup?

quote Originally posted by rjblaze: Someone from the 60*V6 forum just replied to a question I had about the external crank trigger working with our 2.8's and he/she responded that it might work not due to our Fiero pulleys being like a RWD and different than a FWD setup?

I guess that would depend on how they mount. The keyway on the crank is the same, and, I expect that is what is used for alignment. but, the actual pulleys are different, as is the timing cover.

quote Originally posted by Darth Fiero: Just use the twisted pair of wires as-is. Most of the time this is what I find on 3.1 DIS systems; no shield wire. -ryan

any special rules for the twisted pair? I have 2 connectors, with tails, and just made a cable, about 3 foot, and twisted it up. are the solder connections gonna be OK? they dont "twist" very nicely. and, since I am using abandoned Fiero wires, they are of a thicker gauge than the tail wires on the connectors....

quote Originally posted by Pyrthian: any special rules for the twisted pair? I have 2 connectors, with tails, and just made a cable, about 3 foot, and twisted it up. are the solder connections gonna be OK? they dont "twist" very nicely. and, since I am using abandoned Fiero wires, they are of a thicker gauge than the tail wires on the connectors....

What I usually do is stick one end of the pair of wires in a vice, and stick the other end into a cordless drill and tighten the chuck down. I then turn on the drill and allow the wires to twist nicely to the just before the point when they try curling up. After you remove the wiring from the drill/vise it may untwist some, but should still have a nice twist. If you don't twist your pair of wires well enough then they can be susceptible to EM interference from the secondary ignition system.

-ryan

Does TunerCat allow full access to all the tables in the 7730, or just selected ones? I've had bad luck using software that was crippled in this area before.

Also, what are some good links to info on tuning the 7730? I've got an EPROM burner from Needham Micro already so don't mind fiddling around with my own chips.

JazzMan

quote Originally posted by JazzMan: Does TunerCat allow full access to all the tables in the 7730, or just selected ones? I've had bad luck using software that was crippled in this area before. Also, what are some good links to info on tuning the 7730? I've got an EPROM burner from Needham Micro already so don't mind fiddling around with my own chips. JazzMan

ALL tuning software commercially available only gives you access to "selected" tables and constants. I haven't seen one tuning software program that gives you complete access to all tunable bits, constants, and tables used in any GM computer out of the box. Tunercat's software seems to give access to everything you need for tuning purposes; more so than other tuning software programs I have used. I think tunerpro does has some extra tables in their definition file that will allow you to change other things, but not all of it is "useful" for what you will need to do.

The thing I like about tunercat is you can buy their definition file editor program that allows you to add access to tables you want to tune (but you will need a commented disassembly of the code mask so you know memory addresses of the tables you want to add). Such disassemblies are freely available for download on the internet.

quote Originally posted by Darth Fiero: What I usually do is stick one end of the pair of wires in a vice, and stick the other end into a cordless drill and tighten the chuck down. I then turn on the drill and allow the wires to twist nicely to the just before the point when they try curling up. After you remove the wiring from the drill/vise it may untwist some, but should still have a nice twist. If you don't twist your pair of wires well enough then they can be susceptible to EM interference from the secondary ignition system. -ryan

ok, good - was just worried that the splices & the different guage wires may be a problem, or even the length. I could go shorter, but that would leave it outside the main harness, and close to a header. it is gonna be bundled with both the VSS & the alternator wires, then across with the injector wires - all of which I expect are pretty dang noisy. maybe I'll wrap it in tin foil after the twists.....

quote Originally posted by Pyrthian: ok, good - was just worried that the splices & the different guage wires may be a problem, or even the length. I could go shorter, but that would leave it outside the main harness, and close to a header. it is gonna be bundled with both the VSS & the alternator wires, then across with the injector wires - all of which I expect are pretty dang noisy. maybe I'll wrap it in tin foil after the twists.....

You shouldn't need to wrap it in foil or anything. Just make sure you get a good twist and keep it routed away from the spark plug wires.

bump to keep alive

cold weather making it slow going - but - done with most my wiring - just removing wires from the harness now - like the A/C stuff.

but, one thing I was wondering: Darth: the A/C request goes to the ECM - is it possible to have an "alternate" program fro A/C on & A/C off to have something like a "performance" code & "MPG" code?

Doesn't the A/C request function just allow the ECM to proactively bump the RPM for compressor load instead of having to see the RPMs drop and play catchup with the idle air controller?

JazzMan

quote Originally posted by JazzMan: Doesn't the A/C request function just allow the ECM to proactively bump the RPM for compressor load instead of having to see the RPMs drop and play catchup with the idle air controller? JazzMan

not sure what it does - but, I assume it does something, and am wondering how adjustable that something is.

If it is anything like the Caddy ECM (which it sounds very similar) The A/C on request does 3 things. Tells the Compressor to Engage, Bumps the base idle up, and turns the rad fan on. Even on the lowley stock Fiero ECM you can get the A/C on mode to increase the idle rpm. I had this function changed when I was in Vegas by a member of the Las Vegas Fiero club. So my 88GT 2.8 now idles at 1200rpms when the A/C is on. (blows colder and keeps the voltage higher)

I keep reading about this 7730 ECM swap and keep thinking to myself. A pushrod 3.4 is about the only engine mod I can do to my 88GT and keep it Looking stock, which in turn would let me use the factory Camaro sensors and such. Hmm. Well I will keep reading this thread and thinking.

Just out of curiosity, does the ECM pay attention to knock sensor input when in open-loop mode?

quote Originally posted by Blacktree: Just out of curiosity, does the ECM pay attention to knock sensor input when in open-loop mode?

Yes. But there is a constant in the programming that can be adjusted that tells the computer when to enable knock retard based on engine coolant temperature. (stock is typically 65 deg C)

Thanks for the info.

Any chance of having the drawing of the latest revision of the adaptor plate posted? I'd like to make a version of it for my Northstar which will run on the Ryan Hess version of the 7730. I'd like to not reinvent the wheel if I have a choice. You can see so much farther when you stand on the shoulders of giants!

------------------
Daviero - 88 N* GT

Daviero:

Here is the final revision we produced the plates to:



We do, of course, have extras on the shelf if you'd like to purchase one!

------------------
Marc in sunny Titusville, FL

• 84 SE son's car, loaded
  
• 85 Coup w/V6 transplant
  
• 85 GT newly on the road
  
• 86 SE/GT conversion just bought - big plans!

one thing I was wondering: Darth: the A/C request goes to the ECM - is it possible to have an "alternate" program fro A/C on & A/C off to have something like a "performance" code & "MPG" code?

quote Originally posted by Pyrthian: one thing I was wondering: Darth: the A/C request goes to the ECM - is it possible to have an "alternate" program fro A/C on & A/C off to have something like a "performance" code & "MPG" code?

With the tuning software I have available to me there is currently no way I can set up an ECM in the way you are asking about. Basically what needs to be done is the code mask you want to use needs to be hacked to the OS level and then changes need to be made to the OS so the ECM will do what you are asking. To be honest I'm a novice when it comes to writing code in this way so I don't think I can be of much help here. But there are people out there who have been able to do what you ask with other pre-OBD-2 computers so I'm sure it's possible. It's just a matter of finding someone who knows how to do it and who is willing.

-ryan

With a dual image ROM and a bit of wiring, you can change between tunes at the flip of a switch.

quote Originally posted by Will: With a dual image ROM and a bit of wiring, you can change between tunes at the flip of a switch.

Where's that easy button?

http://www.moates.net/produ...25_41&products_id=80

http://www.moates.net/produ...25_41&products_id=87

or

http://www.moates.net/produ...25_41&products_id=47

http://www.moates.net/produ...25_36&products_id=33

Also recommend this be used with the EX Remote for remote switching ability: http://www.moates.net/produ...25_41&products_id=47

I was just going to add that I can make a multi-program chip for you which can be used in conjunction with the above moates.net hardware that will give you the ability to switch between multiple programs on-the-fly. The 7730 ECM uses a 27C256 sized chip program for most of the code masks that would be used in a Fiero application which means I could set your "thumbwheel" chip up with as many as 16 different programs.

-ryan

Any ideas or comments welcome. Hope this is the right place to post. I am replacing the 2.8 w/ camaro 3.4 93-95 intend to use DIS and 7730 ECM. Thought I would use the 3.4 lower intake manifold to eliminate the cold start injector and fan sensor. Now my concern the 2.8 lower intake has a fitting that the manual refers to as "Cold start valve air tube" running between the intake and the Throttle body. How is this used and will there be an impact by plugging the port on the TB.

quote Originally posted by mswenson289: Any ideas or comments welcome. Hope this is the right place to post. I am replacing the 2.8 w/ camaro 3.4 93-95 intend to use DIS and 7730 ECM. Thought I would use the 3.4 lower intake manifold to eliminate the cold start injector and fan sensor. Now my concern the 2.8 lower intake has a fitting that the manual refers to as "Cold start valve air tube" running between the intake and the Throttle body. How is this used and will there be an impact by plugging the port on the TB.

The cold start injector isn't needed with the 7730 ECM. That air tube that runs from the stock Fiero 2.8 TB down to the stock lower intake as far as I know is meant to route air flow past the cold start injector (helps distribute cold start injector fuel to all cylinders). Well if you aren't going to be using the cold start injector then you shouldn't need to worry about this tube. Just plug it if you plan on using the 2.8 upper plenum and you should be fine. But since you are going to be using DIS have you considered just using the stock Camaro 3.4 upper plenum as well? You should be able to turn it around so the throttle body faces the transmission.

Thanks for the response. I wasn't sure on the tube I knew the injector is unused but was concerned that it still used the extra air. I have not seen a drawing (breakdown of the TB) to see how that routed air for cold start. No valve on it so you would have to assume it breaths all the time.
On the upper intake I missed a bolt on the fuel rail and damaged it(upper intake) , but also it interferes with the thermostat housing. I like the looks of the original intake and am running a 4T60 no high rev's here. The long runners allow for torque and that is what I was really desiring.

That air tube running from the throttle body to the lower intake is the idle air tube. It's essential to the operation of the Fiero V6.

If you use the Camaro lower intake, then you'll also need to use the Camaro throttle body. (You may need to use the Camaro upper intake, as well. But I'm not sure.) That's because the idle air setup is different on the Camaro engine.

Edit to add: if you use the Fiero lower intake, you can plug the cold start and fan switch holes with 3/8" NPT pipe plugs. Most hardware stores should have these.

(edited to correct the pipe thread size)

[This message has been edited by Blacktree (edited 02-18-2008).]

quote Originally posted by Blacktree: That air tube running from the throttle body to the lower intake is the idle air tube.

Hmm, after you said that I had to go look it up in my 85 Fiero Service Manual. On page 6E3-78, Figuire-25 it shows the tube in question labeled as the "cold start valve air tube". A couple of pages earlier I found a description of the cold start injector; GM calls it the "cold start valve" in this service manual.

That tube does supply idle air to the motor with the stock throttle body as the IAC port exits at the lower rear of the throttle body. It's the only one I've run across that works like that. All the other throttle bodies I've seen have the IAC port exit just on the backside of the throttle plate.
Here is a pic of the tube:

yes, the IAC path is easy enough to relocate - just a control vacuum leak. it doesnt need to be that big - you see on the throttle body side - it under 1/4". but - I would suggest to NOT use a rubber vacuum line - as it may collapse & stall the motor.

[This message has been edited by Pyrthian (edited 02-18-2008).]

The air tube IAC design was likely done that way in order to use the cold start injector, sort of merging the two functions. The IAC alone would work just fine metering the air back in just past the throttle body.

JazzMan

quote Originally posted by Will: With a dual image ROM and a bit of wiring, you can change between tunes at the flip of a switch.

yes, was just thinking since the A/C request is already there, and in fact does change parameters - I was just hoping this would be a simple approach.

quote Originally posted by JazzMan: The air tube IAC design was likely done that way in order to use the cold start injector, sort of merging the two functions. The IAC alone would work just fine metering the air back in just past the throttle body. JazzMan

I'm just going on what the service manual says about its function. You may very well be correct that this tube has to be present and hooked up in order for the OE Fiero 2.8 throttle body and IAC system to function; if so, I stand corrected on my previous statement. I haven't researched the inner workings of the stock 2.8 to the extent of knowing everything possible about this particular design. But assuming what you say is true, and someone wanted to use a later design lower intake manifold, they would also have to use the later style throttle body so the IAC would continue to function.

[This message has been edited by Darth Fiero (edited 02-18-2008).]