First time on dyno with new setup but....

[0-60B4U]

I went to get my 2004 Cobra dyno tuned on the new setup yesterday and need opinions. I just switched from factory pumps and BAP w/wiring upgrade to twin GT pumps and modified FPDM to give myself a little head room and according to the datalogs I'm maxxing out my fuel pump duty cycle. Peak boost was 18.5# and at 5200rpm my duty cycle was 0.4994. I thought I should be 75-80% duty cycle with that setup...am I crazy? We also noticed that my voltage dropped to 12.5-12.8 volts during the pull so would that have anything to do with it? If so, any help or suggestions would be greatly appreciated. Thanks!

 

[ctgreddy]

Are you still using the bap? if not that might be it. I was always under the impression that bap/stock pumps and gt pumps w/o bap would be very comparable.

 

[fbody83]

Sometimes hoses can get kinked when installing the hat/pumps back into the fuel tank. What fuel hat did you put those pumps in? I've also read about people having issues where the pumps where installed too low in the hat and the socks would touch the bottom of the fuel tank once installed, thus starving the pumps of fuel.

 

[DSGWhippedSnake]

My twin GT pumps and modified FPDM maxed out at 650whp with my 2.3 @20psi. At 18psi the duty cycle was like 81% but I also had 80lb injectors

 

[0-60B4U]

Sometimes hoses can get kinked when installing the hat/pumps back into the fuel tank. What fuel hat did you put those pumps in? I've also read about people having issues where the pumps where installed too low in the hat and the socks would touch the bottom of the fuel tank once installed, thus starving the pumps of fuel.

I'll check for kinks because I hadn't thought about that and the pumps are on my factory hat. I don't think they are installed to low but if all else fails I'll drop the tank again. :xpl:

 

[0-60B4U]

My twin GT pumps and modified FPDM maxed out at 650whp with my 2.3 @20psi. At 18psi the duty cycle was like 81% but I also had 80lb injectors

From everything I had read that's the conclusion I had come too. I'm going to double check everything because the duty cycle seems high to me even with only having 60# injectors. If all else fails I'm just going to buy a Fore hat with bigger pumps and call it a day!

 

[Brutal Metal]

Yes your charging system is down a volt and it will effect the duty cycle. Like mentioned twin GT pumps without bap will support north of 600..

 

[0-60B4U]

Yes your charging system is down a volt and it will effect the duty cycle. Like mentioned twin GT pumps without bap will support north of 600..

Thanks for the info. Since my voltage is low should I upgrade my alternator and if so, any suggestions on what I should do (amps?)?

 

[03' White Snake]

Did you run larger power wires to the pumps?? Stock wiring cannot handle the added current the pumps will draw.

I am doing this same swap, except I am switching to dual FPDM's and wiring upgrade with mine.

I am doing this.... building my own dual FPDM harness.

Modular Revolution Forums

 

[Mach828]

Do you still have the BAP and wiring upgrade?

That voltage is low. I see about 13.8v.

 

[0-60B4U]

Did you run larger power wires to the pumps?? Stock wiring cannot handle the added current the pumps will draw.

I am doing this same swap, except I am switching to dual FPDM's and wiring upgrade with mine.

I am doing this.... building my own dual FPDM harness.

Modular Revolution Forums

I didn't run larger wires because I thought the only concern was my FPDM going into thermal lock due to the voltage drawn. I had no idea the stock wiring to the FPDM wouldn't handle it. I just sold my BAP because I didn't think I would need it along with the Dual FDPM I had because I thought the single modified FDPM would work fine. Plus, it wouldn't require any wiring modifications on the fuel hat.

 

[0-60B4U]

Do you still have the BAP and wiring upgrade?

That voltage is low. I see about 13.8v.

I just sold the BAP and wiring upgrade thinking I wouldn't need them.:shrug:

 

[03' White Snake]

Since your voltage is low, I would start by running larger wires and upgrading the power. A dual FPDM harness with relay can be made for around $60 and an amp power wire for $20. Then its just your time to install it.

I would then check for a kinked hose in the tank.