ok... here we go... everyone strap on your seat belts I am guessing this post will generate some creative "dialog"...
To elminate or keep the OEM Eaton Boost Bypass.... THAT my fellow brothers & Sisters in Harley Davidson Truck land, IS the question.... along with the bigger question why do we build street trucks with Race only mods on them?
Let's take a quick look at the premis of the by-pass on a Roots style S/C like our little Eaton (or Heaton as some call it). What does it do exactly? Well, according to the various sources I have found the priniciple is quite simple. Upon letting off the throttle, there-by slamming the throttle body blade(s) closed, the S/C is still spinning & making boost. While making such boost, it is further heating the air & still trying to pump boost into the cylinders. Further raising temps, grossly leaning the engine out, because the EEC-V is pulling out Fuel & slightly increasing timing to burn off hydrocarbons & other emmisions no-no's all at the same time. The Boost Bypass is simply a vacuum operated dump, that vents the extra boost back through bypassing the engine itself or "reciculating" is another way to look at it.
99.999% of the turbo & S/C kits on the market have a bypass provided in the kit. Turbos, Powerdyne, Procharger Vortech/Paxton, Magnuson, Whipple, Kennep-Bell Weind, B&M, etc doesn't matter the type, the construction, or boost level. THEY ALL have them included with the engineered kits sold.
A quote from the current Race Pages, a large format monthly publication geared toward the NMRA (National Mustang Racers Association). Page 36, June 2004 VOlume06 Issue6:
"Imagine what happens when you're hard on the gass, & the supercharger is making 10psi of boost, cramming copious amounts of presserized air into the intake manifold. All of the sudden you jump off the gas pedal & the throttle closes, but the blower is still moving the air. Creating surge & tremendous amounts of heat. IN EXTREME CASES, IT WILL BREAK THE BLOWER. That's why most supercharger kits include a by-pass valve. When the throttle is closed, the bypass valve vents the pressurized air into the discharge side fo the supercharger and recirculates it into the inlet tube, between the mass air meeter and the supercharger inlet. You can't just vent it to the atmosphere, since the mass air {meter} {sic} already told the engine what to expect in terms of airflow, & you'll run into a tuning nightmare. The higher the boost level, the bigger you have to go on the bypass valve. For example Vortech's standard S-trim kit has a little plastic bypass valve that works great under 10psi, but mire aggressive applications require a bigger bypass, even their new racing bypass, as shown"
In a couple months there is going to be a full issue devoted to Lightning (& thus HD's by default) performance.
So what's the point. As I refered to in the following link:
http://www.nhtoc.com/vbforum/showthr...threadid=10708
its about time we all got together & started really looking at the mods we are doing, really looking at WHY, & WHAT the consequences are. A full on drag-race machine is one thing. But Since we don't have any supporting vendors over here talking with us, just wanting our cash, we have to be more educated than the Lightning guys.
Mods I truly question their effectiveness & have been vocal about:
Bypassing the boost-bypass
Throttle body on a non-built engine
Long tubes on a street truck
Oil Seperator (snake oil creator??)
Any air system that pulls air from under the hood
Tuning a chip/programmer via mail order
just to name a few of the most popular mods.
Yeah, yeah, yeah, I know Part xxx made me 15 rwhp or item yyz did so much etc... at what expense or at what cost to driveability or long term durablity? How many times did it have to be redone before it was right?
We have a bunch of new members looking for answers that are being shunned by the Lightning boards or ignored. I would venture a gentleman's wager that over 90% of our HD's are street trucks that MIGHT see a drag strip 3-4 times in its career. So why are we building them like a JLP, JDM, PSP, or other tuner's drag race only truck??
I am currently trying to compile a chart of the known trucks that puked guts & what the common threads among their mods are, if any. There are some interesting consistencies.
Just stirring up some thoughts & conversation....
Rob W.