Quote:
Originally Posted by oldman
I don't see how the DSX pump effects fueling, it turns on at say 5 PSI and supplies about 80 PSI of fuel, about the time when the stock pump is unable to maintain 80 PSI, I've looked at my fuel graph (low pressure side) hundreds of times, there is no big spike. The only caveat that I can make is I also installed a LT4 Low pump in tank. I also custom orders a 2 PSI turn op pressure.
The only way I can see the secondary pump effect tuning is if it were coming on late and you had a weak factory intake pump (early SS).
I've found DSX very supportive and a quality product.
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After you discover the flaws with the kit and ask Dave about it, the support disappears. He will ghost you, because he knows the kit has issues that he can't acknowledge.
The idea of how it works seems great. I bought into it too. The problem comes in when you validate that it maintains proper fuel pressure in all scenarios.
My car is a manual transmission. I could make my engine run lean just by shifting slowly between 4th and 5th. At the end of 4th the aux pump is running at its max and the intank pump is running at whatever speed needed to make up the difference between between the aux pump and the fuel demand. As you shift, the fuel demand suddenly drops and the pressure spikes very high 600 kPa+. The car then commands the intank pump to its minimum duty cycle to get the pressure down to commanded...so the pump slows to barely moving. As you complete the shift and go wide open again, the in tank pump doesn't start to increase its duty cycle until the pressure drops below the commanded pressure in spite of the fact that the fuel demand is high and the pressure is dropping fast. By the time the computer realizes the intank pump needs to speed back up, pressure is well below commanded...not to mention there is a mechanical latency for the pump to actually get up to speed. The engine will momentarily run lean every time.
That's just one example of something you have to tune for. It is possible to tune around that scenario, but you have to command much higher fuel pressures to avoid pressure drops below 500 kPa.
The issue with the DSX kit only pulling from one side of the tank is a real problem if you ever go wide open throttle after a hard right turn. On a clockwise roadcourse, this is common scenario. I kept seeing major fuel pressure drops with a 1/2 tank of gas, but on the dyno it worked fine. It wasn't until I logged the fuel level sensors independently until I realized how often the right side tank doesn't have any fuel in it at all. If there's no fuel in the right side tank, and you got WOT, that's a recipe for a new engine.
I couldn't disagree more about the quality kit comment. Maybe the parts seem nice, but the poor design that doesn't account for the fact we have a saddle tank could have cost me an engine.