Maverick
old-school
- Location
- Anywhere, thanks to my geeky droid
Ok, so that sounds like normal behavior, right? to dump the boost at higher pressure? Is that the "whoosh" sound you hear when turbo vehicles shift?
Are you sure it's "dumping the boost"? It shouldn't dump until it's above 30 or higher. (I've seen my stocker above 25)
If it feels like it's dumping at around 15psi or so, (or the boost guage is bouncing in that range) then it's actually surging, which is really bad for your turbo. Ask me how I know. I thought it was relieving pressure. Not so. $1100 or so later and I had a rebuilt turbo and a ported housing so it wouldn't surge anymore. And it doesn't, it's wonderful.
Joining in late, I towed with 315's for a while on my eXcursion and went back to 305's (33's), it just handles better on 33's. My wheelbase is shorter than a crewcab, so 315's on a crewcab are probably fine. I just got sick of the slosh from bigger tires. One good (the only?) argument for 18" or 20" rims.
I've had a drop in mileage every time I went to bigger tires, even adjusted for tire size/speed. So much for lower RPMs giving you better mileage.
Running 315's with 4.56's you'll be at about 2250rpm at 70mph, which is a little high. 37's will drop that to 2100rpm, very liveable. Until you have to pony up the cash to replace the tires.
I really liked mbryson's shortbed crewcab superduty with a leveling kit. The 285 toyo's looked bigger than the 315's on my excursion, and fit the 7.3 and stock gears perfectly. Good combo.