1985 with a speed density tune.
Thread Starter
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
1985 with a speed density tune.
We're working on a 85 with a 434 that dyno'd 700 hp with a carb. With a modified Stealthram, 48 lb Accels, and a 1227730 ecm the car would run good until it got warm, and then it would start sputtering. The AC Delco rep has said we're burning up injector drivers. We've burned up 2 ecm's.
Got pissed off, put a carb on it and ran 9.97 at Bremerton, WA on street tires. Okay, in the meantime, injectors went to Dr. Injector and it seems one is short to ground when opened. Would this bad injector be the cause of driver failure, or is 700 hp overwhelming the OEM speed density system overheating the injector driver?
Any common sense input will be appreciated.
Got pissed off, put a carb on it and ran 9.97 at Bremerton, WA on street tires. Okay, in the meantime, injectors went to Dr. Injector and it seems one is short to ground when opened. Would this bad injector be the cause of driver failure, or is 700 hp overwhelming the OEM speed density system overheating the injector driver?
Any common sense input will be appreciated.
Melting Slicks
Joined: Apr 2001
Posts: 2,117
Likes: 222
From: Ca.
We're working on a 85 with a 434 that dyno'd 700 hp with a carb. With a modified Stealthram, 48 lb Accels, and a 1227730 ecm the car would run good until it got warm, and then it would start sputtering. The AC Delco rep has said we're burning up injector drivers. We've burned up 2 ecm's.
Got pissed off, put a carb on it and ran 9.97 at Bremerton, WA on street tires. Okay, in the meantime, injectors went to Dr. Injector and it seems one is short to ground when opened. Would this bad injector be the cause of driver failure, or is 700 hp overwhelming the OEM speed density system overheating the injector driver?
Any common sense input will be appreciated.
Got pissed off, put a carb on it and ran 9.97 at Bremerton, WA on street tires. Okay, in the meantime, injectors went to Dr. Injector and it seems one is short to ground when opened. Would this bad injector be the cause of driver failure, or is 700 hp overwhelming the OEM speed density system overheating the injector driver?
Any common sense input will be appreciated.
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 397
From: Lakeville MI
(8) 48 lb./hr injectors at 100% duty cycle should flow `384 lb/hr. of fuel. Assuming 0.5 bsfc this could support ~ 76h8 hp which is in the ball park.
It would seem that bigger injectors are in order to avoid 100% injector duty cycle and burning out the drivers. (8) 63 lb. injectors at ~76% duty should live at this hp level. Needs more injector assuming fuel pump can keep up.
It would seem that bigger injectors are in order to avoid 100% injector duty cycle and burning out the drivers. (8) 63 lb. injectors at ~76% duty should live at this hp level. Needs more injector assuming fuel pump can keep up.
Last edited by tequilaboy; Jun 25, 2013 at 11:57 PM.
Thread Starter
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
AXCN was the base file used. No need for S_AUJP, because the motor has 15" of vacuum at idle. Can you say REALLY BIG HEADS and a reasonable solid roller.
Thread Starter
Drifting
Joined: May 2013
Posts: 1,736
Likes: 31
From: Reno Nevada
(8) 48 lb./hr injectors at 100% duty cycle should flow `384 lb/hr. of fuel. Assuming 0.5 bsfc this could support ~ 76h8 hp which is in the ball park.
It would seem that bigger injectors are in order to avoid 100% injector duty cycle and burning out the drivers. (8) 63 lb. injectors at ~76% duty should live at this hp level. Needs more injector assuming fuel pump can keep up.
It would seem that bigger injectors are in order to avoid 100% injector duty cycle and burning out the drivers. (8) 63 lb. injectors at ~76% duty should live at this hp level. Needs more injector assuming fuel pump can keep up.
Racer
Joined: Aug 2009
Posts: 337
Likes: 6
From: Kanata ON
Even 100% duty cycle, especially since it should be for a very short duration, shouldn't fry a computer. Shorted injector definitely could, so first get that fixed. After that you should be good to go.
BTW: was the same bank always failing? Presumably it was the bank that also had the bad injector.
BTW: was the same bank always failing? Presumably it was the bank that also had the bad injector.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Referencing injector drivers...
I am an electronic engineer and about 5 years ago I saw an ad in one of the electronic design magazines for new injector drivers. Unfortunately I somehow lost the info and don't even remember which manufacturer it was. I think it was IR (International Rectifier).
More dumbness on my part: I took my ECM apart and wrote down the part number for the injector driver. I lost THAT too (actually all this info was lost in a computer crash but I didn't have this particular bit of info backed up). I do remember that it was made by IR, who makes a LOT of MOSFETs, which is what the injector driver is.
Anyhow, the point of this post is that later versions of these transistors are much more robust than the antiques in the original ECMs.
I am an electronic engineer and about 5 years ago I saw an ad in one of the electronic design magazines for new injector drivers. Unfortunately I somehow lost the info and don't even remember which manufacturer it was. I think it was IR (International Rectifier).
More dumbness on my part: I took my ECM apart and wrote down the part number for the injector driver. I lost THAT too (actually all this info was lost in a computer crash but I didn't have this particular bit of info backed up). I do remember that it was made by IR, who makes a LOT of MOSFETs, which is what the injector driver is.
Anyhow, the point of this post is that later versions of these transistors are much more robust than the antiques in the original ECMs.
Last edited by Cliff Harris; Jun 29, 2013 at 09:46 PM. Reason: Clarification.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I found the link I didn't even know I had on my own web site. Here ya go:
http://www.irf.com/whats-new/nr100331.html
My recollection is that Digi-Key carries these parts. Our ECMs use the TO-220 package and need a low RDS(on). RDS means Resistance from Drain to Source and basically tells you how hot the transistor will get when it's turned on. The lower the better. You're only going to pull about 10 amps, so any one of those will work fine. It is important to get a good thermal connection to the ECM heat sink to help the transistor stay cool (that's relative because it will get pretty hot to your touch, but not hot enough to hurt itself). I have seen transistors that got so hot they melted the solder that held them into the PC board but they were still working. That's why GM was able to put the ECMs under the hood of the later C4s.
http://www.irf.com/whats-new/nr100331.html
My recollection is that Digi-Key carries these parts. Our ECMs use the TO-220 package and need a low RDS(on). RDS means Resistance from Drain to Source and basically tells you how hot the transistor will get when it's turned on. The lower the better. You're only going to pull about 10 amps, so any one of those will work fine. It is important to get a good thermal connection to the ECM heat sink to help the transistor stay cool (that's relative because it will get pretty hot to your touch, but not hot enough to hurt itself). I have seen transistors that got so hot they melted the solder that held them into the PC board but they were still working. That's why GM was able to put the ECMs under the hood of the later C4s.
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