I believe without any doubt that the single biggest cause of lost MPG in these tanks is fouled/clogged injectors.
I have now run 2 sets of these injectors on the flow bench . first off they are very crappy old style injectors. the spray patern is one that was used by BMW in the 80's. the concept was to have a heavy center stream with a misting halo around that. the problem comes from the halo orrifices are very small and tend to clog very easily.
also the center heavy stream when it gets clogged it tends to shoot sideways . this causes the majority of fuel to to run to one side of the inlet chamber and not atomize. this causes uneven fuel burn and a loss of MPG and power. because of the nature of closed loop systems this will not throw a code in most cases.
With Al babayan's injectors he had dropped to I believe about 8MPG before we did them. after we backflushed the set and replaced the 2 worst injectors his truck jumped up to I believe around 14MPG or so.
the injectors on my D1 were just as bad as AL's and I was getting about 9MPG after doing them I am getting about 14.5 MPG with MT's and a roof rack
I am right now working on finding a true replacement injector with a buddy of mine. the ones we have tested that some people are putting in ...such as the ones 5-0 motorsports sells are about 20% rich at WOT. because most fuel systems only work in closed loop at partial throttle this becomes a problem. at heavy loads at slow speeds such as off-road this will be even more of a problem. once I find just the right injector I will report back .
the other reason for a new injector is the stock ones cost about $150 each where most others can be had for $25-$50 each.
MM
