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??? 30 psi isn't normal
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Discussion Starter · #1 ·
I was wondering just what is involved in modding a stock ecm so it will be able to control low impedance injectors? Also could a person just install the properly rated resistor on each injector so that the ohm rating of the injector is raised to that of a high impedance injector?

David
 

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Fuhgeddaboudit
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It would be nice if just using a few resistors to do the conversion. But either you have to send it out to Bob Bailey, Reds or PTE or change the drivers yourself. Last price I seen was $129 plus S&H and a two week turn around. 50lb and 57lb high impedance injectors will get you into the 10's. What is your ET goal?
 

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??? 30 psi isn't normal
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Discussion Starter · #3 ·
not really looking for a certain et. Why I am wondering is that my current setup consists of te-44, 42.5#, 307 pump hot wired, esp front mount, atr dp w/ ext gate, atr single shot exhaust w/no cat, percision 3000 convertor. with this set up running 110 oct fuel at 21 psi direct scan showed that my injector duty cycle was over 100% .. I would just upgrade to 50# injectors but I have a set of champion cnc series head and a ported intake that I am planning to install on the car. I am just taking a guess at the injector size I will need, but I have a feeling its going to be somewhere around 75# and I will most likely have to upgrade the pump too. I just don't want to run into the condition I am in now. I hate the fact I have to keep the boost below 20 psi angrymou
 

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Fuhgeddaboudit
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As long as you keep the TE44 and 3000 stall the 50LB or 57lb injectors will handle anything you add to your combo. If you step up to a much bigger turbo and converter then 75lbs may be in order.
 

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??? 30 psi isn't normal
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Discussion Starter · #5 ·
Okay I can see what you are saying about the 57# injectors, but I am still curious about what exactly is done to a stock ecm so that it can run low impedance injectors .. you said something about changing the drivers ... I would think it was a physical change to the ecm not a software. if it is removing or changing an electronic part on the ecm's board then I am capable on doing that myself. The price you quoted of $129 is what I was told it would cost. I have just become very untrusting of vendors in this area. Just seen too many electronic items that make no performance gainor were way over priced for what parts they were made up of. I maybe wrong but I have a gut feeling that the modding of an ecm in reality cost no where near that .. guess I am just jaded .. have seen what I consider price gouging by alot of the companies that sell parts for our cars.
 

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Fuhgeddaboudit
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The drivers are on the mounted pc board in the ecm. I guess you can change them yourself. Open up your ecm ID them and order what you need. If you don't know what to order I guess you can ask one of the crooked vendors dunno
 

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??? 30 psi isn't normal
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Discussion Starter · #7 ·
well finally found out what the mod is .. as I kind of figured it was a change of the transistor in the ecm but as with many things with our cars .. cherry and motorla no longer make the transistor for the low impedance injectors. So I can see why the price of the mod is up there .. law of supply and demand. But the main thing is that I see how its done and I now understand the reason for the price. :)
 

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??? 30 psi isn't normal
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Discussion Starter · #9 ·
Steve, I have tried several different chips (Red, PTE, Jay C, and ATR) DS had shown all of these running the injectors @ or near 100%. The ATR strip chip actually pushed the injectors to 104%. I am currently using the Red Armstrong 93 chip and at 15 psi with a boost creap to 18 psi in third gear; DS is showing that the injectors reach 81.1%. so I am not sure that its the chip, but I am not very knowledgable about what exactly goes into the fuel curve design in the chip. I have the ds file if you care to look at it. any ideas you have as to just how much injector and any fuel system upgrades that I may need will be helpful. I would like to have a little over kill in the fuel system .. I have never liked to run the system at the very edge of its limits.

Thanks,
David
 

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42.5# are good to at least mid 11s and some have pushed a lot more.

Fuel requirement depends upon hp being made. Most aftermarket chips tend to set wot to 100% whether you need it or not. Anything over 80% dc is usually somewhat meaningless as the injectors become erratic as they approach 100%.

The only thing I see wrong with your fuel system is that the 307 pump begins to bypass at a fairly low pressure but you are not running enuf boost to worry about that, and, many run much quicker/faster.

I would prefer to use an egt to look at exhaust temps to know if I was nearing a lean condition, but, in lieu of that, I would continue bumping boost up a pound at a time until I found the limit where timing retard began to occur, and, then, back off one pound.

Looking at the dc does not really tell you anything other than how the chip was programmed.

Send me a DS file...I will be happy to have a look.



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Those darn LS1 guys/girls are taking their cars into the low low 11's with stinking SVO 30lb injectors. I still have a hard time fathoming why our cars need such big fuel injectors. dunno I guess it's related to an N/A car not having a need for more fuel due to the increase in cylinder pressure, right Steve-O ? powersix
 

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NOSjohnWE4:
Those darn LS1 guys/girls are taking their cars into the low low 11's with stinking SVO 30lb injectors. I still have a hard time fathoming why our cars need such big fuel injectors. dunno I guess it's related to an N/A car not having a need for more fuel due to the increase in cylinder pressure, right Steve-O ? powersix
I think it has to do with the fact that they have 2 extra injectors. 30#/hr * 8 cylinders = 240 #'s while 36#/hr *6 cylinders = 216 #'s of fuel. Just so you know I ran 11.38 on the bluetops that are now in my 13 second car.
 

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Paul's typing is a little faster than mine:D
Two extra cylinders doesn't hurt either!
30lb/hr injectors X 8 cylinders = 240lb/hr
240lb/hr / 6 injectors = 40 lb/hr
To make the same power we need 40's vs. their 30's.
The increased cylinder presures of our boosted engines needs a slightly richer fuel/air mixture to prevent detonation, so a little more injector adds that cushion too.
CaptRob

<small>[ November 11, 2003, 01:19 PM: Message edited by: captrob ]</small>
 

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??? 30 psi isn't normal
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Discussion Starter · #14 ·
Steve the file has been emailed to you. Along with a little more info

David
 

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Just got it...

typically, forced aspiration engines require .55-.65 lbs of fuel per hp per hour whereas normally aspirated engines use something more like .4-.5 lbs/hr.

As pointed out 6 x 40 is the same as 8 x 30 and when taking into account that we require a bit more being turbo'd, things make a little more sense.

If you are conservative and use an 80% DC, then one would pick larger injectors than currently used for no other reason than safety.

On the other hand, as pointed out above, it is very common to go faster with the equivalent injectors. It may be that .55 is a safe number for BSFC on milder cars. I always use .6 for a margin.

I will look at your file and respond via E mail as you have some valid points for the future, I think.



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Exactly what I thought, thanks Paul, Rob, and Steve-O. powersix
 
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