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glory to the hypnotoad
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Discussion Starter · #1 ·
Confirmed -- I indeed have the well known issue with 550cc injectors at 9psi. As soon as I got it building 9+ psi after 8k, it started stumbling and making obviously angry sounds from the exhaust after 8k. In my datalog, you can see the rpms get jerky and the a/f start swinging wildly. I stopped tuning and will just have to stay under 8k until the 650s get here. I didn't get any missfire codes, but it was obviously not running right.

I'm pretty sure it was shooting fire when this happened too as it was really rich and then the a/f instability probably lit it up with lean spikes -- you could hear the exhaust note change
:flame:
 

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glory to the hypnotoad
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Discussion Starter · #4 ·
silver comet said:
On the brighter side 8k can still be pretty fun
Yeah .. I don't go to or over 8k on a daily basis ;)

This won't affect me at all on a daily basis. I just ordered the 650s so next weekend will probably have some fuel tuning in it.
 

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doing stuff
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Whoops... I missed this thread. Sorry to hear that Raz... especially since I encouraged you to give it a go. I'm not sure why I've had such good luck with my 550s. I don't go above 8k very often either, but I have datalogged pulls as high as 8500 without seeing the problem. :dontknow:
 

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SS Specialist to the 6th
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Ouch, that sucks man. I had the same issue with my 550's :(

Then I got a walbro fuel pump, hoping it would help... nope. Gotta go with the 650's. You'll be glad you did because 9psi pulley + 8700RPM = insane

Push: the issue is the way the 550's spray the fuel. Not everyone has the problem, but a lot of us did.
 

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hm wierd. i didn't have any issues with my 550's....but then i was only on the "8psi" 3.3 comptech pulley but it peaks at over 9. yea...seems like roll fo the dice
 

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RIP 2/4/2009
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krystar said:
hm wierd. i didn't have any issues with my 550's....but then i was only on the "8psi" 3.3 comptech pulley but it peaks at over 9. yea...seems like roll fo the dice
Don't forget though, the CT manifold is designed differently than the JR mani, those spacers we remove to install RCs really change how the injector is positioned in the manifold.
 

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glory to the hypnotoad
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Discussion Starter · #10 ·
Oside Jimc said:
Don't forget though, the CT manifold is designed differently than the JR mani, those spacers we remove to install RCs really change how the injector is positioned in the manifold.
Doug @ hondata posted up a thread a while back explaining that it was specifically a combination of the rc550 spray pattern paired with the JR intake manifold design and blower pulses from spinning the blower at the speed required to hit 9psi. He said that with the JR RSX manifold, the problem presented itself much higher in the rpm range as compared to the JR EP3 manifold. I'd say he was right on as from just before 8k - 8500 is where my issue shows up.

The 550s, unlike the 440 or 650s from rc, have a unique spray pattern that just doesn't work well in the jr manifolds when paired with the right blower pulses.

Comptech has buffeting, JR w/ 550 has problems at 9psi.... it seems that manifold design is not to be taken lightly.
 

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This is making me wonder if I shouldn't just go to the 650s as well. Although I haven't seen the issue, my duty cycle has exceded 90 percent at times. I'll definately need more injector if I want to do anything else and it would be nice to have some breathing room. Anyone have an opinion on 750s?
 

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Push said:
This is making me wonder if I shouldn't just go to the 650s as well. Although I haven't seen the issue, my duty cycle has exceded 90 percent at times. I'll definately need more injector if I want to do anything else and it would be nice to have some breathing room. Anyone have an opinion on 750s?
I think the RC 550cc injectors are hit and miss.
I had 9psi and I was taking it to 8800 rpm no problems. 94% duty

Then I switched them for RC750cc + 11psi pulley + cams

They work very nice with walbro pump, even without the pump there awesome. The only problem I have had with them is ruff idling.

With 11psi + 750cc ( no walbro ) + 50F IAT I was hitting 91% duty, the walbro lowered it to 64% even with the cams in.
 

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Well I just found a good deal on 650s from another member so I ordered them. Hell, I might as well do the 11psi pulley now too :laughing:
 
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