Recently upgraded my HX40 to a BD Super B single. I have really tall gearing in my truck after installing 37's with a 3.54 diff and .69 transmission OD. The improvement in spool up put a smile on my face, and made my truck more driveable and enjoyable. It took 2 whole seconds off spool time, and put a smile on my face. Funny, after a few days it only would spool to about 35 psi, even with the wastegate disconnected. Otherwise, it still ran really well. Shortly thereafter, put in a water-meth system, then manually tested it during idle, which almost snubbed the engine and blew the head gasket. Sent the head to Scheid, who refurbished the head, and fire-ringed it. Got ARP studs, and had the local shop put it all together. Now, once I get it spooled up, it only gets to low 30's psi like before, but the bigger problem is that IT JUST DOES NOT WANT TO SPOOL AT ALL unless I really get on it for a LONG time. I notice a lot more "stumbling" at low RPM's, but seems OK once the power finally comes up. Problem is, to get the thing to spool, it resists enough to go to EGT redline almost every time. In fact, I can't drive it in OD, as it goes to redline on EGT, and the reason it does is that it just won't spin the turbo and build any boost. Maybe 3-5 psi in that condition, whereas before it would be 10-15 psi cruising in OD at maybe 70 mph. I have to disable OD just to drive my truck.
I'm mostly convinced it's not the turbo itself, but relates to the low-end stumble that's especially noticeable before truck is warmed up. Very different than before.
Sorry for the long post, but hoping there is a "killer tech" out there that might have a suggestion for me. I've made some calls, but nobody even has a suggestion. Yes, I realize there are a lot of possible variables. Scheid did a pop-off test on the injectors when they did their job.
I want to put in a compound turbo system, but not before the truck runs like it did before! Though it's geared really tall at the moment, it WAS working quite nicely with the new turbo.
Seems to me it likely relates to fueling, but I don't know how. Black smoke still pours out, but spooling just won't happen.
Very grateful!
John
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