ok so 8.1l rear mount turbo.. blower cam .060 over engine. marine injectors. custom tune. 76mm turbo .80 a/r turbo rear mount. 3" intercooler piping to 3"in 3"out intercooler.. 50mm blow off 50mm waste gate


5lbs 4x4 launch
boost dropps off after launch.. thinking the 4lb wastegate spring is the problem..


ideas or sugestions???

 

Probably an issue, unless your leaking boost from a loose pipe/coupler. I've installed those rear mounts before, lots of hose's/clamps to check. Does this in all gears, or just at launch?

 

check for leaks 1st. any boost controller? that's a lot of motor to be feeding w/ that turbo. it probably will fall off a lot on the top end. unless you have a large tire, 4.56's won't load turbo up very good.

 

One of the bigges things I hate from rear mount turbo setups. Exhaust leaks. Check for any. Thats quite alot of gear also, what size tire you running?

 

i guese i didnt mention 4.56 rears with 305-70-16's rounds out to around a 33" tire.. ran it today from a rolling start.. 1-2 0 boost 3rd ran up to 3lbs and didnt go past that.. im personaly thinking the engine is spinning up to fast and not loading the turbo enough although it sounds WONDERFULL

 

welds are ugly but they work

 

In my experience with rear mount turbos, is that the shorter the gear, the less they spool. 1st, gear, not much, 2nd, better, 3rd-4th-5th feel tremendous. Part of the reason I wanna pull gear OUT of my tahoe(3.73's and go 3.08's) just for that reason, to load them up, hoping to get it(them) to spool quicker.

It's the only thing I can think of, based on what your posting. I am no expert but, this is what I have ran into after doing several rearmount and several front mount setups.

Other thing that could be going on possibly, is too large diameter of piping. Be it, compressor side, or turbine side,...you may, MAY...have to large of pipe, equaling not enough velocity... that, coupled with the gear set....may make some more sense.

Anywho, just a thought or two.

 

Its loading that turbo just fine. The compressor is just too small. 496 cubic inches and a 76mm...what did you expect. lol

 

running almost the same exact set up as others have on the forum...

ill run the wg tube back to the intake manifold and see if it will hold 4psi in lower gears.. doubt it but i dont care because when i hook the camper it will load just fine

 

very much in agree at this point.. piping may play a part since its alot of distance to run