7747 batch fire...
10-19-2005, 03:20 PM
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7747 batch fire...
I've been reading a lot of older posts about running TPI off a 7747 ecm and have found several different answers......
First off, if I build a tune port intake, can I run it off a 7747?
Second, how do the 7747 injector drivers get hooked up?
Which leads to...third, will it run batch fire or bank fire.
I've read answrs ranging from "the 2 drivers can't handle 8 injectors" to "It will run 8 high impedence injectors off the 2 drivers" to "there are 4 drivers and it may/maynot work" to Run everything off one driver.
Finally, what are "saturated" injectors? I seem to have missed exactly what this means.
There was a lot of reference to the MPFI setup sold in Summit, but I'm not buying one of those, so it's kind of irrelevant.
Somebody must have tried this by now.
Any clarification would help.
-Mike
First off, if I build a tune port intake, can I run it off a 7747?
Second, how do the 7747 injector drivers get hooked up?
Which leads to...third, will it run batch fire or bank fire.
I've read answrs ranging from "the 2 drivers can't handle 8 injectors" to "It will run 8 high impedence injectors off the 2 drivers" to "there are 4 drivers and it may/maynot work" to Run everything off one driver.
Finally, what are "saturated" injectors? I seem to have missed exactly what this means.
There was a lot of reference to the MPFI setup sold in Summit, but I'm not buying one of those, so it's kind of irrelevant.
Somebody must have tried this by now.
Any clarification would help.
-Mike
10-19-2005, 03:54 PM
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It ping-pongs back and fouth from injector to injector. Basically, each bank would fire twice per revolution in sync fire. Not quite sure how that would fly. With just one injector driver, it would be two fires per revolution for all. Each stratagy can cause pulsewidth issues as there are 2x as many firings. Additionally, youd want to completly block async fire, since that will fire alll the injectors at 80 Hz. Not what youd want with a port fuel system.
Saturated injectors are high resistance injectors. Even though the TBI ecm is peak and hold, it should run those ok. You may also be able to run low resistance injectors on each side provided the resistance that each driver sees is comprable to ~1.2 ohms. Dont know whats available injector wise for this.
Finally this has been done, but Id think youd be better off using a 90-92 TPI ECM. Its alot better, and much more suited to the task. Unlike the crap TBI ecm code, the stuff in the TPI ecm will be true SD and will work much better then the half-assed stock TBI stuff. I think youd be much happier in the end.
Saturated injectors are high resistance injectors. Even though the TBI ecm is peak and hold, it should run those ok. You may also be able to run low resistance injectors on each side provided the resistance that each driver sees is comprable to ~1.2 ohms. Dont know whats available injector wise for this.
Finally this has been done, but Id think youd be better off using a 90-92 TPI ECM. Its alot better, and much more suited to the task. Unlike the crap TBI ecm code, the stuff in the TPI ecm will be true SD and will work much better then the half-assed stock TBI stuff. I think youd be much happier in the end.
Last edited by dimented24x7; 10-19-2005 at 04:00 PM.
10-20-2005, 07:01 AM
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Re: 7747 batch fire...
Originally posted by SB406
I've been reading a lot of older posts about running TPI off a 7747 ecm and have found several different answers......
First off, if I build a tune port intake, can I run it off a 7747?
Second, how do the 7747 injector drivers get hooked up?
Which leads to...third, will it run batch fire or bank fire.
It will run in bank mode, alternating injector banks. Four (or three for a six banger) injectors will be wired to each injector driver.
I've read answrs ranging from "the 2 drivers can't handle 8 injectors" to "It will run 8 high impedence injectors off the 2 drivers" to "there are 4 drivers and it may/maynot work" to Run everything off one driver.
There are two drivers in the ECM. A bank of four injectors will be wired to each driver. The injectors need to be wired in parallel, which is how standard port setups are already wired.
Finally, what are "saturated" injectors? I seem to have missed exactly what this means.
Saturated injectors are greater then 12 ohms each. Typically run between 12 and 16 ohms dependent upon the actual injector make and model. Peak'nHolds run at 2.4 ohms for a port injector and 1.2 ohms for a TBI injector. The 'saturated' part is how the driver is run, it is in a saturated mode, full on.
There was a lot of reference to the MPFI setup sold in Summit, but I'm not buying one of those, so it's kind of irrelevant.
Somebody must have tried this by now.
Yep, Edelbrock sells a system that converts a TBI to MPFI and uses the stock TBI ECM. I'm sure others have done it just to get away from the re-wiring and finding another ECM.
RBob.
Any clarification would help.
-Mike
I've been reading a lot of older posts about running TPI off a 7747 ecm and have found several different answers......
First off, if I build a tune port intake, can I run it off a 7747?
Second, how do the 7747 injector drivers get hooked up?
Which leads to...third, will it run batch fire or bank fire.
It will run in bank mode, alternating injector banks. Four (or three for a six banger) injectors will be wired to each injector driver.
I've read answrs ranging from "the 2 drivers can't handle 8 injectors" to "It will run 8 high impedence injectors off the 2 drivers" to "there are 4 drivers and it may/maynot work" to Run everything off one driver.
There are two drivers in the ECM. A bank of four injectors will be wired to each driver. The injectors need to be wired in parallel, which is how standard port setups are already wired.
Finally, what are "saturated" injectors? I seem to have missed exactly what this means.
Saturated injectors are greater then 12 ohms each. Typically run between 12 and 16 ohms dependent upon the actual injector make and model. Peak'nHolds run at 2.4 ohms for a port injector and 1.2 ohms for a TBI injector. The 'saturated' part is how the driver is run, it is in a saturated mode, full on.
There was a lot of reference to the MPFI setup sold in Summit, but I'm not buying one of those, so it's kind of irrelevant.
Somebody must have tried this by now.
Yep, Edelbrock sells a system that converts a TBI to MPFI and uses the stock TBI ECM. I'm sure others have done it just to get away from the re-wiring and finding another ECM.
RBob.
Any clarification would help.
-Mike
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