smokeshow re-dyno
08-26-2011, 10:43 AM
#11
TECH Regular
Speed density on a E38 - Way to break down barriers! Great numbers. In for details and pictures on this dual pump returnless fuel system. Is your stock pump the variable output unit?
08-26-2011, 08:08 PM
#20
I do have some ET streets, but I think they might be a bit too short to handle the torque. I'll use 'em for all their worth lol.
Ok, fuel system info! First off, the fuel system on these trucks is extremely versatile, and highly underestimated in my opinion. The IFR (Injector Flow Rate) table in the GMT900 tune is dynamic with fuel pressure because the FPCM (Fuel Pressure Control Module) from the factory has three different pressure settings based on fuel demand. Once the fuel pressure sensor detects the drop in pressure, it begins pulling flow data from the new part of the table with either lower or higher fuel pressure.
That's why I was able to put down over 600 with the stock pump (those numbers were made on a single pump, BTW). Fuel pumps flow more at lower pressure, so as the pump couldn't keep up with the flow at high pressure, it dropped and the duty cycle on the injectors went up to compensate. I knew I was pushing it with the single pump though because my injectors weren't big enough to handle the pressure drops. So I tied in a second stock pump from a sending unit I bought from a member here on the forum to run it in parallel. Normal driving the fuel system works like normal, zero change from stock save for different lines. I trigger the 2nd pump to turn on with a hobbs switch at 5psi. No more pressure drops now with the second pump, stays steady at 60psi. My goal was to keep it as stock as possible; you can't tell there are any changes to the fuel system except for the power wires coming out of the fuel hat.
Its basically a really cheap alternative to other fuel systems on the market, and easy to make. I might have like $300 in parts in it, including the new sending unit/pump and AN fittings and braided line. If the single pump flows over 600hp worth of fuel, I can only assume this setup should be good to at least 1000. There are a lot of 90s in the supply line so I'm not sure how much effect that will have on the flow of the dual pumps, but after turning the second one on on the dyno, it showed no problems at all.
It came out looking a bit weird but since I work so far from the parts shop in town I just put it in the tank and gave it a shot, and it worked great. If I end up doing another GMT900 for the next truck, I'm going to run the same setup but try to hack the bucket a little more to fit the filter down inside it. It could look a lot more tidy, but nobody would ever know the difference being in the tank.
Ok, fuel system info! First off, the fuel system on these trucks is extremely versatile, and highly underestimated in my opinion. The IFR (Injector Flow Rate) table in the GMT900 tune is dynamic with fuel pressure because the FPCM (Fuel Pressure Control Module) from the factory has three different pressure settings based on fuel demand. Once the fuel pressure sensor detects the drop in pressure, it begins pulling flow data from the new part of the table with either lower or higher fuel pressure.
That's why I was able to put down over 600 with the stock pump (those numbers were made on a single pump, BTW). Fuel pumps flow more at lower pressure, so as the pump couldn't keep up with the flow at high pressure, it dropped and the duty cycle on the injectors went up to compensate. I knew I was pushing it with the single pump though because my injectors weren't big enough to handle the pressure drops. So I tied in a second stock pump from a sending unit I bought from a member here on the forum to run it in parallel. Normal driving the fuel system works like normal, zero change from stock save for different lines. I trigger the 2nd pump to turn on with a hobbs switch at 5psi. No more pressure drops now with the second pump, stays steady at 60psi. My goal was to keep it as stock as possible; you can't tell there are any changes to the fuel system except for the power wires coming out of the fuel hat.
Its basically a really cheap alternative to other fuel systems on the market, and easy to make. I might have like $300 in parts in it, including the new sending unit/pump and AN fittings and braided line. If the single pump flows over 600hp worth of fuel, I can only assume this setup should be good to at least 1000. There are a lot of 90s in the supply line so I'm not sure how much effect that will have on the flow of the dual pumps, but after turning the second one on on the dyno, it showed no problems at all.
It came out looking a bit weird but since I work so far from the parts shop in town I just put it in the tank and gave it a shot, and it worked great. If I end up doing another GMT900 for the next truck, I'm going to run the same setup but try to hack the bucket a little more to fit the filter down inside it. It could look a lot more tidy, but nobody would ever know the difference being in the tank.