Kevin L

I'm getting a P-chip in a couple of days, I know it might not be the absolute best chip on the market, but for the price how can you go wrong. Anthony at Greedspeed said that for an additional $20 they will modify my fuel pressure reguator to boost the fuel pressure to 5 bar (about 58 psi gage) Apperently they just recrimp it? What does this do for your fuel usage? How much performance is gained?

liquid flow rate=(flow coeffecient*(square root of change in pressure across injector))/(square root of the specific gravity of gasoline)

using the above formula and assuming that the flow coefficient of the injector and the specific gravity of gasoline remain constant, and that the pressure downstream of the injector is atmospheric (I know it is actually negative, but we'll keep this simple) and finally that the stock regulator pressure is 50 psig. This equates to a liquid flow that is increased by 7.7%. Does anyone know how the injectors work? Does the engine get this increased flow thought out the RPM range or only when it needs more? I really don't want to decrease my mileage by almost 8%. Plus it would mean extra work for the catalytic convertor at the conditions that don't need (and can't use) the extra fuel.

He also said that Audi offers a 5 bar regulator but its big bucks.

jamie

If the chip is properly programmed, you don't need to modify the fuel pressure regulator. Save your money.

-jamie

Darrel

In a similar vein, even w/ the Garrett anti-surge ECM I still experience a lot of what has been called surging or a non-linear throttle response that I do not have w/ the MTM chip. Todd at AWE suggested I try a 98-99 fuel pressure regulator stating the 97 produced 3.5 bar & the 98-99 4.0. Apparently the Garrett chip needs increased fuel flow that the 97 doesn't produce. My dealer stated that it did make some sense to them. However, from reading this board I would GUESS the P-chip doesn't need it. I have yet to buy one. The increased mileage is a good question. My MTM recently went bad. Dealer wanted $1,200 for a new OEM, stating only 7 exist in the USA. Might be good to get two ECMs if you can. Please Email me w/ any more info you find out. Thanks

Confused again

unless he is going to sell you a chip that expects the increased fuel flow. If the p-chip is properly engineered, and lets just assume that it is, then the timing, boost, and flow maps will be calibrated to the stock fuel pressure. If, however, the p-chip runs a little lean at higher manifold pressures and tends to ping, then this may be a quick and dirty fix.