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Old 06-11-2007, 10:39 PM   #1
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Default How much boost on 320cc injectors

Ok.. so im gonna be boosting soon now that the megasquirt is all running good.. The problem is.. all i have right now is 320cc injectors.. how much boost would it be safe to run on these injectors?

I know i could just keep upping until my DC gets too high, but i just kinda wanted a rough estimate

Also, the main question, when I DO get new injectors, what size should i get?

I'm lookin to run from 12-14 psi on my 16g turbo
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Old 06-11-2007, 10:53 PM   #2
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Try around 6-7 psi with the 320cc. Then get a set of 460s, or 550s if you think you'll want more than 14psi someday.
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Old 06-11-2007, 10:58 PM   #3
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Originally Posted by Atlanta93LE View Post
Try around 6-7 psi with the 320cc. Then get a set of 460s, or 550s if you think you'll want more than 14psi someday.
I'm not gonna want more than 14 for a long time, cuz i dont wanna build an engine for a while, are 460s good enough for 14?
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Old 06-11-2007, 11:05 PM   #4
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Old 06-11-2007, 11:09 PM   #5
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someone just offered me 4 550cc's for 105 shipped from a "low mileage jdm motor" i guess ill send them in to get cleaned still shouldnt I?
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Old 06-11-2007, 11:12 PM   #6
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RC Eng would say you're on the ragged edge of the injector at ~220rwhp, so do you think you'll make more than that at 14psi? Keep in mind, RC calcs tend to be conservative.

IIRC, Ben is making 255hp at 15psi with his GReddy 15g, and is reaching 80%DC on his 440s (correct me if I'm wrong Ben). So 460s would be alright at the same power level, which is probably about what you'd hit with a great tune at 14psi, as your turbo is bigger than the 15g.
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Old 06-11-2007, 11:15 PM   #7
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Quote:
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someone just offered me 4 550cc's for 105 shipped from a "low mileage jdm motor" i guess ill send them in to get cleaned still shouldnt I?
If they don't fit in the stock harness, make sure you get harness pigtails with them. Also, consider the fact that idle might be a bit more difficult to tune with the larger injectors.

I paid $50 shipped for my 460s. But then, they haven't arrived yet either.
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Old 06-11-2007, 11:16 PM   #8
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Yeah i figure 460s would be ok but i got a ok deal on those 550s so ill go with those
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Old 06-11-2007, 11:17 PM   #9
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do the stock rx-7 550cc's not have the same connectors?
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Old 06-11-2007, 11:23 PM   #10
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89-91 have the same connector
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Old 06-11-2007, 11:25 PM   #11
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ok thats what they are, i copied and pasted the rx-7 550cc ones from braineacks writeup onto my WTB thread
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Old 06-11-2007, 11:33 PM   #12
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Quote:
Originally Posted by Atlanta93LE View Post
IIRC, Ben is making 255hp at 15psi with his GReddy 15g, and is reaching 80%DC on his 440s (correct me if I'm wrong Ben).
RC Eng 440 running 74% duty cycle at HP peak, 255 wheel @ 13 psi
That was on a dynapack, so it would be a tad bit more on a dynojet. They are the RC nozzle type injector that supposedly atomize better and respond more quickly than pintle type injectors.

Assuming identical lag times (but theoretically your lag time could be shorter) and atomization properties, your injectors should be good for 206 wheel hp at 80% dc. I used this formula 255/74*80 * 330/440

You can use your datalogging to watch IJDC. If you have headroom, you can turn boost up. If you're running over 85%, turn boost down. I'm at 200 wheel around 10 psi with my smaller turbo. If you have a free flowing exhaust, you're probably limited to around 8 psi or so. Use your datalog to see if you have headroom or not for more. I also have a 190lph hp pump, so that may help keep pressure up with boost. A stock fuel pump may require more ijdc at the same power level to keep the motor fueled.
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Old 06-11-2007, 11:36 PM   #13
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Yeah thats what i figured i would do until I get the new ones bought and cleaned..

I'm not positive, but i think my wastegate on my turbo is a 12psi wastegate, that might be too much do you think?

Quote:
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RC Eng 440 running 74% duty cycle at HP peak, 255 wheel @ 13 psi
That was on a dynapack, so it would be a tad bit more on a dynojet. They are the RC nozzle type injector that supposedly atomize better and respond more quickly than pintle type injectors.

Assuming identical lag times (but theoretically your lag time could be shorter) and atomization properties, your injectors should be good for 206 wheel hp at 80% dc. I used this formula 255/74*80 * 330/440

You can use your datalogging to watch IJDC. If you have headroom, you can turn boost up. If you're running over 85%, turn boost down.
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Old 06-11-2007, 11:43 PM   #14
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Yeah be real careful. I wouldn't do any hard runs if it's a 12psi can.

WG cans can be replaced for cheap. You can always get a 6-8 psi can and then run MS EBC.
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Old 06-11-2007, 11:44 PM   #15
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Yeah i'd considered that, but i'd rather be sure of what i have before i buy another one for it

Quote:
Originally Posted by Ben View Post
Yeah be real careful. I wouldn't do any hard runs if it's a 12psi can.

WG cans can be replaced for cheap. You can always get a 6-8 psi can and then run MS EBC.
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Old 06-11-2007, 11:47 PM   #16
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maybe you can find somone with a compressor and a pressure regulator. blow metered air into the can and see where it opens.
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Old 06-11-2007, 11:51 PM   #17
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Yeah I'll try that, im debating wether i wanna sell the 320cc's i have now as they are because they havent been used since they have been cleaned and flow tested, they wouldnt be worth as much after i used them.. but oh well **** it ill use them

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maybe you can find somone with a compressor and a pressure regulator. blow metered air into the can and see where it opens.
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Old 06-12-2007, 08:07 AM   #18
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This guy has some T2 injectors from a 88 that are 550cc, will those work or does it have to be from a 89-91?
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Old 06-12-2007, 08:42 AM   #19
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They won't plug into the stock harness, but you can wire in pigtails to make them work.
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