| [GMCnet] FiTech is the real deal [message #295002] |
Wed, 03 February 2016 17:41  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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1000 mile report.
This EFI really transforms the way the coach runs and drives. As others have reported re other brands of self learning EFI, the coach starts instantly hot or cold, idles smoothly, seems impervious to altitude changes, is more responsive, seems immune to vapor lock, and in most all ways now drives like a new car. There seems to be little, if any, change in fuel consumption or power (the 455 S&J engine is quite powerful in its own right regardless of induction) which is what I expected.
So far on this trip we are averaging 8.3 mpg at the speeds encountered through California on the I5 and US 99 (fairly high just to flow with traffic) and in that average is climbing Siskiyou Pass (highest point on the I5) and Tahachipee Pass (alternate to the Grapevine) to get into the southern CA desert. Gearing is 3.67, spark is via an HEI Dick Patterson curved for this EfI and we do not tow but are loaded with everything for a two to three month trip.
Vacuum is more responsive to throttle given the four simultaneous opening butterfly valves in the throttle body vs the two primaries in the Qjet right up to the point that the secondaries would open on the Qjet. In the last couple of tanks it seems to me that vacuum is up a bit during cruise, which could be due either to the system still learning or simply to perhaps driving at a somewhat slower average speed.
From what I have learned from others, and have observed myself over the years of driving these two different GMCs, mileage will change about 0.5 mpg for every 5 mph change in average speed. Want to get 1 mpg more than you get now? Then slow down 10 mph.
Is this FiTech system worth the investment? Emphatically, yes. The cost is right at $1000 for the EFI plus another $400 for the fuel management system (surge tank, voltage controlled submerged high pressure pump, fill valve that mimics the float valve in the Qjet so you can use any mechanical or electric low pressure pump without a return line, and gauges to show high and low fuel pressures). I blocked off the mechanical fuel pump and use a Carter p4070 rotary vane fuel pump drawing only from the rear (main) tank for a safe fuel capacity of about 40 gallons. The magnetic pusher pump is still installed on the aux tank if I ever need it. When I get home I will likely add the two check valves, an oil pressure shut off switch and a second Carter pump to have a running spare and the ability to draw from both tanks but I don't think that is really necessary.
More as I learn more. All gain and no pain so far.
Jerry Work
The Dovetail Joint
Fine furniture designed & hand crafted
in the 1907 former Masonic Temple building
in historic Kerby, OR
http://jerrywork.com
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Jerry & Sharon Work
78 Royale
Kerby, OR
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