My engine cuts out under load in 3rd 4th and 5th gear

[SR 510]

OK, Here's what going on. I have a Datsun 510 with an SR20DE. But, ever since I swapped it in my car I have been having a strange problem. The motor runs really nice and has plenty of power, but everything cuts out and bogs when I am at 6,000 RPMs in third gear, 5,000 RPMs in fourth and 110mph in fifth. When it cuts I cannot accelerate for about 5 seconds and then the motor runs again. The strange thing is that when I am going downhill I can go 125+ MPH and when I go up hill I can't even get it above 100 mph. I am guessing it has something to do with load but I am completely stumped. If somebody could help me I would really appreciate it. Thanks

note: I know that it is not a speed limiter because I have no wires running from my transmission to tell the computer what gear I am in, nor how fast I am going. I have a walbro 255 inline fuel pump. I also have huge custom fuel lines and bigger inlet/outlet from the tank and My fuel filter is fine.

-Keith

[Nismo_Freak]

Does it completely kill the engine or does it misfire?

Sounds like you could be getting alot of detonation in the higher gears as the load increases and the knock sensor is causing ignition to cut out.

Also, your ECU might be resorting to MAF voltage for limiting the engine, but that sounds off because it would happen around the same RPM.

The SR and KA both have overrev protection. I have hit this before and it shut the car pretty much off till I restarted it on my 240. It's possible you are tripping this as well.

[SR 510]

It kills the engine completely for about 5 seconds if I let off the gas pedal. If I stay on the gas the car wil continue to bog until i have come to a complete stop. I should not be detonating because I am running stock timing (15 degrees) What do you think? Thanks

[cheapspeed]

sounds like fuel to me check the position of your pickup in the fuel tank it could be running dry when you go uphill creates a situation similar to yours also check the voltage to the fuel pump the walboro may require more voltage than the stock wiring is capable of sending