Has it actually been proven, that it's safe to run the GM without a resistor? How many miles have people put on this sort of setup without problems, and what type of problems would you expect to see? Also wouldn't these problems show up right off the bat?

What differences would be seen in real world driving between the wiring harness from spoolinup, with and without the resistor? Would the differences even be noticable?

 

The main concern is the increased current draw from the BCS circuit. We literally do not know the maximum draw the circuit can sustain without injury. By using the resistor, you're basically trying to stay closer to the same current draw as the stock BCS would have. Without the resistor you will see a faster response time but not nearly enough to have me singing praises about it. With that said, using the inline resistor is playing it safer.

 

I would highly doubt the boost drop would be from the GM 3-port getting hot. I had mine directly bolted to the frame rail (acting as one heck of a heatsink) and did pulls in 20 degree weather and it still would lose a little boost after 1 or 2 pulls. If someone logged the current draw during 3-4 pulls they would most likely see a drop in current draw if it was getting hot since the internal resistance (I would say 'impedence' is the more proper word) would go up. I would agree that it probably has something to do with heat generation in the exhaust components too.

There were always 2 things I learned to live with when tuning:

• 1st pull will most likely have knock during spoolup and then basically disappear for the rest of the pulls.
  
• GM 3-Port Boost drops off and settles in where it wants to be after a few pulls.

 

This is so helpful!

 

Good info

I'm still on the wire on Grimmspeed or GM

 

Does the GM get hot then?? does theGrimmspeed?

 

IMHO, you're overthinking this. Both will warm up with use. In my limited bench testing, both only got warm to the touch. Waste heat from the radiator will heat them up much more.

 

BUMP - Wish we could test the NEW PERRIN EBCS.. someone send theirs in for testing.

 

forgive me, why does the GM BCS need that harness? I just bought the GS BCS, but im curious what this is for

 

do you mean the electrical adapter harness?

 

yeah, the one spoolinup sells

 

The power receptacle on the GM BCS does not match the OEM Evo BCS power plug on the harness, so an adapter harness is needed unless you want to cut the factory harness and spice on a GM plug. The spoolin up adapter can be purchased with or without a resistor that people thought was necessary to keep the lower resistance GM BCS from blowing the BCS power circuit in the ECU. Turns out the resistor is not needed and degrades BCS performance, so if you want to buy the adapter harness, get it without the resistor.

 

Very succinct, thank you.

I went with a GS, but it's good to know.

 

The valve bouncing off the stop that mrfred experienced might be what caused the boost to oscillate on the Evo Xs that I have tuned with the Grimmspeed. The boost oscillates early on in the rpm range and then it flattens out. It could be that the valve bouncing off the stop is causing the boost to oscillate. It happened to more than one Evo X running the Grimmspeed. Based on that behavior, I would stick with the GM BCS.