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Old 09-07-2004, 03:42 PM
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Sequential fire vs. Batch fire Injection

I was curious as to the efficiency benefits of sequential firing injection vs. batch fire. Any more power to be had? Id assume there is some gas mileage to be had from it. Does anyone make an upgrade for the 80's era TPI's which were batch fire? If so what does it involve (I realize it would involve a computer change but how would it organize injector leads into a sequential pattern?). Would the upgrade (if it exists) be worth the trouble and money?

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Old 09-07-2004, 05:15 PM
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fire

there are benifits to be had by switching from batch fire. You will need to determine if they out weight the costs. You will need to use something like the Accel Gen 7 DFI and their Dual Sync distributor. The ECM will need a cam and crank reference to fire in seq. mode. The benifits of seq. are more accurate fuel metering, individual cylinder tuning, better throttle response and it eases the hydralics of the fuel rail. Every time a bank fires (Batch fire) It empties the rail, so the fuel pressure in the rail is less consistant and harder on the regulator.

hope this helps..........

is it worth it?
How much power are you wanting to make?
$3500+ for a complete system. ECM, harness, pump, intake, rails,ect........
OR $1900(est.) for New ECM harness & distibutor.
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Old 09-07-2004, 05:26 PM
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Siggy, sequential fire over batch fire is more efficient ie more bang for the buck. I am in the process of upgrading a 72 350 motor to TPI. I am using the hardware from an 88 5.7 Camaro and the computer from a 93 3.2. The stock number you need has the last 3 numbers of 730 and is in a herd of gm cars from 90 to 94. I am using the inlet air temp, throttle position, coolant, and oil pressure sensors from the 87. You must get a manifold absolute pressure sensor from one of the 90-94 GM cars. You also should get a knock sensor, even though the motor will run fine without it. I am using the Painless wiring harness without any of the pollution garbage incorporated. You also need to buy a new O2 sensor, only because it is almost impossible to successfully salvage an old one. The computers since 89 have the VATS (vehicle anti theft system) installed and the motor will not start unless you have the original steering column and ignition key. You can get around this by getting a kit from Painless, or have a new chip burned for your setup, which I am doing. The Painless harness has the wiring for controlling the lock/unlock for the earlier 700R4. I already have the Painless lock up kit in the tranny and it works super so I don't need the wiring but am storing it under the dash. One other thing, you can use about any GM HEI with internal or external coil. I happen to be using the small Camaro HEI with external coil because of more room and it came with the Junkyard TPI setup. Painless provides and adapter to let you use either distributor. You probably have the in tank fuel pump and return line already installed. If not, I would recommend the Carter P-5000 in line fuel pump, available from most any parts house, but would probably have to order. In the overall scheme of things, since you already have the old system, it should be quite simple. Just remove your old computer(2 plug ins), and put the new one(3 plug ins), and remove the old wiring harness and install the after market. You will need to separate out some of the basic vehicle wiring but should not be a real problem

The Painless wiring kit explains every thing you need to know and is easy to understand.

Trees.
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Old 09-07-2004, 08:29 PM
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As mentioned above there are some advantages. More power is not one of them. Individual cylinder tuning is also a moot point unless you are planning on spending alot of money on sensors and getting some serious computer power. The main advantage is a little bit of fuel effciency if you use a cam and crank sensor. If this is done the injector phasing can be controlled to gain some vaporization of fuel before entering the chamber.

I just finished changing my pro flo hardware over to a Genboard V3.1 with sequential injection. I am only using a distributor hall sensor since I could care less about fuel economy and injector phasing is not important for power since the injectors are open most of the time under full power. All you have to do to make this change is separate out the injector commons and run them all back to the ECU.

IMO, you would be miles ahead on milage gains by getting a controller capable of running and using WBO2 so you can maximize the AFR at cruise speeds. Genboard can control two WBO2 sensors as well as running in closed loop all the time and auto tuning of the VE table with the sensors. It is the only affordable sollution that will do this. I am very happy and confident with the V3.1 since I have gotten it up and running. Let me know if you want to know more.

Chris
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Old 09-08-2004, 01:50 AM
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Yeah I would like more info on how the Wideband O2 differs from what an 85 TPI uses. How it works and creates a more accurate reading. Also, the TPI kicks it into open loop during WOT. Does your system keep it in closed loop or what did you mean by it capable or always running closed?

Thanks for the info all. Its just been something I have been curious about. I am already running an 85 TPI setup on my 66 pickup and am always looking for ways to improve both gas mileage and power.
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Old 09-08-2004, 06:45 AM
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Narrow band O2 sensors, like you have, are designd to read 14.7:1 AFR(stoich).......and that is it. A narrow band sensor has a voltage range from 0-1VDC. The voltage output curve that is steap from 0-.49 volts, flat from .49-.51 or so, then steep to .9 volts. This curve changes as the temperature changes to some extent. With this funky voltage curve it is impossible to accurately tell what the AFR is at anything other than 14.7 AFR. I know that you see some cheese ball crap that says it can read AFR from NBO2, but trust me it is JUNK.

Your oem computer is designed to do what is sometimes called a bang-bang type of fuel control at cruise and idle. When it sees O2 voltage go below .495-.5 volts, it decreases the fuel to raise the voltage. It then does the opposite when the voltage rises above.

Okay, now that we have the junk out of the way..........
Wideband sensors on the other hand have an output voltag from 0-5VDC and a usable range from about 1.5VDC to 3VDC. The output voltage is almost linear and AFR(converted from lambda reading) can be determined within .1 or so. It is very dependant on the accuracy of the control of the sensor itself. The WB sensor has a controlled heater circuit to maintain temperature and a controlled pump circuit. If you are up for some confusion do a search and read all you can about the WB sensor control. I dont fully understand the controll methodology.......but I dont have to.

The Genboard V3.1, and probably a few others available on the aftermarket, have the ability to control the WBO2 sensors and to interpret the voltage output of the sensors so AFR can the displayed and controlled. The Genboard does run in closed loop all the time if you want it to. It uses a lambda correction table so that you can specify the AFR you want at every point in the RPM/kpa range of the engine. It can also use this feedback from the lambda correction to automatically tune the VE table based on the lambda table. If you understand what this means..........it is VERY exciting! I have just finished getting my VE table close enough to start running in closed loop and doing auto tune so I can let you know in a week or two how it works. The Genboard is probably 1/4 the cost of any other controller that does this if you buy it 100% assembled and 1/8 if you want to do the final assembly and testing.

Chris
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Old 09-08-2004, 08:42 AM
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WB02 is a very good tuning tool. Accels system will also run in closed loop and tune to the desired a/f ratio. you can use a digital temp gun to measure header temp and add small amounts of fuel to individual cylinders if they are slightly lean.
Is the Genboard capable of running a nos system? How can I find some info?
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Old 09-08-2004, 10:15 AM
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Quote:
Originally posted by ponykiller511
WB02 is a very good tuning tool. Accels system will also run in closed loop and tune to the desired a/f ratio. you can use a digital temp gun to measure header temp and add small amounts of fuel to individual cylinders if they are slightly lean.
Is the Genboard capable of running a nos system? How can I find some info?
Yes, it can run NO2. It has free outputs that can be programmed to open based on RPM, TPS, and a few other parameters. The hack was first implemented on a GRM car in the Hotrod 2004 dallar challenge. Now it is part of the configuration parameters and is easy to setup.

You can get info at www.vems-group.org. It is a wiki so it seems a little hard to navigate at first. Right now we are working on getting a manual in a new format so parts of it are missing and incomplete. There are alot of us in the group that can give you info if you cant find it. You can talk to the members and the developers from an irc chat channel. Go to the http://www.vems-group.org/index.php?page=ListsAndForums for a jumper page to irc.

Chris
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