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LS376/480 RPM limit

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Old 06-26-2012, 07:03 PM   #1
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Default LS376/480 RPM limit

I'm from Russia and my english not very well..

I have new ls376/480 for drifting, and in drifting a lot time engine working in RPM limit.
This is my project
Click the image to open in full size.

The problem is the RPM limit is very slow.. when I get limit my drift die, it works not like "tutututututu" like "tuuuuutuuuuuutuuuuuu"

I connect computer to OBD2 and read stock ECU, the RPM limiter intervals are 80 RPM, so it should work great.. fuel pressure 62 psi... ignition stock...

Sorry for this not understandable text
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Old 06-27-2012, 03:26 PM   #2
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Maybe electrical problems. Check all grounds, run the harness ground directly to negative battery terminal. The other possibility is bad valve spring. I am assuming the fuel delivery is good to the injectors.
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Old 06-27-2012, 07:54 PM   #3
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Quote:
Originally Posted by 427 zeo6 View Post
Maybe electrical problems. Check all grounds, run the harness ground directly to negative battery terminal. The other possibility is bad valve spring. I am assuming the fuel delivery is good to the injectors.
Thx tomorrow will check all harness. Engine is new so i think valve springs ok
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Old 06-27-2012, 08:10 PM   #4
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Is your speedometer hooked up and the ECM programmed correctly for your gears? Perhaps you're hitting a false KPH/MPH limit?
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Old 06-28-2012, 05:34 AM   #5
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Originally Posted by 85MikeTPI View Post
Is your speedometer hooked up and the ECM programmed correctly for your gears? Perhaps you're hitting a false KPH/MPH limit?
ECM is stock, engine is stock, so there is could not be any problem
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Old 06-28-2012, 03:19 PM   #6
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I think GM programs LS376/480 controller for 6500rpm rev limit. I guess you know that, if it won't get to that RPM limit, then electrical, fuel, or valvetrain problems are going to be the cause.
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Old 06-28-2012, 03:26 PM   #7
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In your description, best I understand, you are saying it is not bouncing off the rev limiter "tutututu" but, dying off entirely "tuuuuuuu". I would think it is first a fuel delivery problem, not enough volume of fuel, either poor fuel pump, blockage in fuel line or injectors. Could also be voltage problems at fuel pump, do you have a large electrical wire to fuel pump? The BMW fuel pump should give enough delivery but, maybe there is a electrical problem in system.
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Old 06-29-2012, 03:44 PM   #8
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Quote:
Originally Posted by 427 zeo6 View Post
In your description, best I understand, you are saying it is not bouncing off the rev limiter "tutututu" but, dying off entirely "tuuuuuuu". I would think it is first a fuel delivery problem, not enough volume of fuel, either poor fuel pump, blockage in fuel line or injectors. Could also be voltage problems at fuel pump, do you have a large electrical wire to fuel pump? The BMW fuel pump should give enough delivery but, maybe there is a electrical problem in system.
My car is Nissan Silvia S15, the fuel pump is Tomei (275 litres/hour), fuel pressure with ingnition "ON" 60++psi or 4,5 kg/cm2, injectors stock wich was on new engine. Maybe tomorrow I will check electical problems but my friend he is electrical master, said that if it electrical problem, I see it not only in RPM limit, but in engine work in general..
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Old 06-29-2012, 05:12 PM   #9
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You cannot rule out electrical. We built a gen1 motor with EFI onetime and it ran flawlessly on the dyno, then when in the car, it wouldn't RPM, after many hours it was found that fuel pump connector was begining to fail and voltage was dropping below 11 volts. This motor ran fine until about 5500rpm.
The other thing I would check is for plugged injectors or fuel line problems, did you make sure system is 100% clean before starting up new installation. Good luck.
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Old 06-29-2012, 06:06 PM   #10
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Quote:
Originally Posted by Goshan View Post
ECM is stock, engine is stock, so there is could not be any problem
What transmission are you using and where are you getting a VSS signal to feed the ECM the vehicle speed?
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Old 06-29-2012, 06:46 PM   #11
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Could possibly be fuel slosh. Perhaps fuel tank is low for weight purposes? Are you running car with say, only a couple of gallons of fuel in the tank?
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Old 06-29-2012, 07:50 PM   #12
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Quote:
Originally Posted by 427 zeo6 View Post
You cannot rule out electrical. We built a gen1 motor with EFI onetime and it ran flawlessly on the dyno, then when in the car, it wouldn't RPM, after many hours it was found that fuel pump connector was begining to fail and voltage was dropping below 11 volts. This motor ran fine until about 5500rpm.
The other thing I would check is for plugged injectors or fuel line problems, did you make sure system is 100% clean before starting up new installation. Good luck.
Tomorrow will check all electrical and connectors You check this problem in the run or in static with ignition "ON"?
Yes everythink was fine with fuel lines, but know I think maybe fuel regulator broken?
This how fuel works, in the right down corner is a half image of regulator:
Click the image to open in full size.
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Old 06-29-2012, 07:59 PM   #13
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Quote:
Originally Posted by 85MikeTPI View Post
What transmission are you using and where are you getting a VSS signal to feed the ECM the vehicle speed?
I use T56 6 speed from Camaro 98-02, the speed sensor are not connect because I didn't find this sensor on the transmission So I don't have speedometr
This how it arrived to me, maybe this broken one was a speed sensor?
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Old 06-29-2012, 08:01 PM   #14
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Quote:
Originally Posted by Che70velle View Post
Could possibly be fuel slosh. Perhaps fuel tank is low for weight purposes? Are you running car with say, only a couple of gallons of fuel in the tank?
Fuel tank is nissan stock for 60 litres, always full with 98 octane
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Old 06-29-2012, 09:24 PM   #15
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wow 98? is that cool to run on stock tune? i thought some cases 93 had to be tuned to run best.
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Old 06-29-2012, 09:31 PM   #16
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You should check the fuel pressure at wide open throttle under load. The fuel pressure can be ok with key on and engine off and even at idle but volume and pressure can drop at wide open throttle.
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Old 06-29-2012, 09:59 PM   #17
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You NEED to connect the VSS to the ECU. Your post #13 is the VSS. It will not run well without it connected. Grab a new sensor. Plug it into the ECU. The ECU puts out a 4000 pulse per mile signal.

The speedometer in the car does not need to be connected but the VSS to the ECU does.
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Old 06-30-2012, 01:32 AM   #18
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If your using GM performance ECM you don't need VSS. I say redo fuel system with late model Corvette fuel filter with built in pressure regulator and get rid of present setup. You can mount filter at back of car and run single fuel line to intake fuel rail no return line just like C5/6 Corvette. This is what instructions for LS480 from GM recommend.
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Old 06-30-2012, 01:32 AM
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