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Undersize fuel pump is a bad thing. Don't treat it like a governor or the lean condition it creates will treat your pistons like solder. Lean conditions run MUCH hotter than rich ones...hence why we run the engines richer with boost. If you sustain more than a second or so at lean boost levels, there is the REAL possibility of melting piston tops. The scarier part is that the engine will continue to produce power while lean. So there's the tendency to keep pushing it particularly if you don't have a fuel pressure gauge to monitor. By the time the AFR gets so lean the engine is bogging, you've already run it way too long while lean. The engine is evidently grossly overbuilt for the fuel system.

Ok, here's where I tangent off-subject a bit, but I like the sound of my own keyboard, so I just kept typing...

Also keep in mind what I mean by "lean". Lean and rich are relative terms. They are relative to what target AFR you are trying to attain. At cruise, the general assumption is that you want to run at or near stoic (14.64 AFR or 1.0 lambda). So lean would be running above 1.0 lambda. Rich is running below 1.0 lambda. However at WOT on an N/A engine, target might be .85 lambda (~12.5 AFR). So running lean would be say .9-.95 lambda. In boosted engines, the target AFR drops from .85 the more boost you run. A mild boost of 5-6 PSI generally doesn't require much more than .8 lambda. When you get up into the 10 PSI range, you want to be in the high .7s. And 15-20PSI is almost always .75 or sometimes lower depending on the fuel.

For those not familiar with lambda, it's the more consistent and less confusing way to talk about AFRs. It's frustrating to talk in terms of actual AFRs today because we have so many fuels and the "standard" fuel most people burn today isn't the same as it used to be (i.e. E10 instead of 100% gasoline). So if I said 14.4 AFR, is that rich or lean of stoic? Depends. If you are talking about 100% gasoline, it's rich. If you are talking E10 (10% ethanol), then it's lean. So to avoid the confusion, speak in therms of lambda. .95 lambda is ALWAYS rich relative to stoic regardless of what fuel you are burning (100% gas, E10, E15, E85, methanol, CNG, Propane, C16 race, whatever).

It gets even more confusing since Widebands, even today, still display in terms of 100% gasoline AFR. So when you burn something other than 100% gasoline, the gauge still displays the AFRs as if it were gasoline. Thus a 14.64 reading on the gauge is stoic regardless of what fuel is actually being burned. That's right, Widebands DO NOT measure AFR. They measure lambda. That's why they are called lambda-sensors.

So what is lambda when used to discuss engine AFRs? Lambda is an indication of the percentage of excess air or fuel is in an exhaust mix. A 1.10 lambda measurement indicates there was 10% excess air in the burn. A 0.9 lambda reading indicates there was a 10% excess of fuel. To give you a display value other than lambda, the gauge/meter ASSUMES a fuel being burned and multiplies that fuel's stoic AFR by the measured lambda value to give you what you see. In the case of 100% gasoline, the assumed stoic AFR is 14.64. So if even if what you are running in the engine is E85 (stoic of 9.76 AFR) if the sensor measures say .95 lambda but is assuming you are running 100% gasoline, then what you'll see is 13.9 AFR, not 9.3 AFR which is the actual AFR mix.

Here's an article I wrote up that explains this further:
EECTuning.org>Widebands measure lambda (λ), not AFR

It's much harder to screw this up with E85. It should be quite obvious that the reading you are getting isn't right. However E10 and 100% gasoline are close enough that this one really trips people up on the EECTuning forum. They hook up their WB and want cruising to target 14.1 (E10's stoic value). But they don't know this detail about lambda and widebands. So in their efforts to hit what they think is E10's stoic, they wind up actually running the engine rich. Because 14.1 using the default setup on a WB meter is ALWAYS a rich condition relative to stoic. So even though they are running E10, they should view the meter with the same assumption that the meter is making...that they are burning 100% gasoline and accept that 14.64 is stoic even though it's not the actual AFR.

Did I just confuse everybody?

The only time it cuts out is above 4500 rpm's which I dont do hardly at all.. Its not a daily driver. I dont think I put 1000 miles a year on it.. I do plan on changing the pump, but right now having to put money into my boat has put my truck on the back burner. if it was a daily driver then I would have to put that up front.

v8ranger wrote:Went to a 3 1/2 inch pulley. So far so good.. Boost comes in much sooner now.

Yup that's how it goes. Every time you swap to a smaller pulley it's the low end and mid range you really notice and feel seat of the pants. Vehicle gets so much more responsive. Obviously top end has more power too.

cgrey8 wrote:Undersize fuel pump is a bad thing. Don't treat it like a governor or the lean condition it creates will treat your pistons like solder. Lean conditions run MUCH hotter than rich ones...hence why we run the engines richer with boost. If you sustain more than a second or so at lean boost levels, there is the REAL possibility of melting piston tops. The scarier part is that the engine will continue to produce power while lean. So there's the tendency to keep pushing it particularly if you don't have a fuel pressure gauge to monitor. By the time the AFR gets so lean the engine is bogging, you've already run it way too long while lean. The engine is evidently grossly overbuilt for the fuel system.

Yup lean sucks. I ran into all kinds of problems back in the day when building and tuning my turbo Honda. Even just a little lean and it'd detonate, stretch the head bolts and lift the head. Of course I was pushing that car hard and to the limits. I mean why else turbo it right?

Eventually the motor was fully built, forged rods, pistons, head studs etc. and while tuning and experimenting, playing with water methanol injection, switching to E85, back to pump gas and so forth I knew I needed a better solution for lean protection and so was born the Lean Protection Module. Designed and built it myself and when locals got wind of it and saw it in action I had instant demand and started producing them commercially and selling them.

http://www.mdracingkc.com/Modules.html

Basically it's watching your AF under WOT conditions like a hawk and the instant you're getting into trouble it shuts you down, you have to let off the gas pedal (getting you out of that lean condition) and then lightly depress back on it and the car comes back to life. So much nicer than blowing motors. Gives you a second chance to go fix what failed. I can't tell you how many times that's saved my butt on my various toy cars while playing around and changing things up.