I ordered some tires and wheels. Front tires are some random Coopers meant for classic muscle cars it seems, 235/60r15 I want to say. Extremely limited tire selection for 15s, and I thought a 17 would just look dumb on the truck, so the Coopers seemed like the only tire within a range that look halfway decent and coincidentally was the size I wanted. The front tire size I currently have that's 26" tall is actually quite a bit larger than factory tires, but I didn't want to drop sizes since I want to lower the truck an inch or two (maybe...) and still have some amount of ground clearance, and lowering it with the tires would look weird. The new front tires will be over an inch wider than my current ones so hopefully look decent. For the rears I got 275/50r15 Nitto 555Rs, which are also 26" tall tires and drag radials. These will be like 3" wider than the current rear tires. I debated going to a taller tire, but after reading I didn't think it'd give much advantage and I don't want it to look like a drag car with massively tall rear tires, which is why I kept the front and rear the same diameter so from the side it'll look pretty discrete. For wheels I got some cheapo steelie 15x8s, again to keep it discrete, plus I'm sure I'll eventually change the wheels and lug pattern and these cost $50 a piece. All in with mounting and balancing I think will run $1300, and the tires should show up tomorrow and the wheels I got yesterday.
I got the Summit wastegate in and got to work integrating that into the turbo housing. I started with milling out a pocket on the exhaust housing.
Then fit up a 1.75" tube and welded it on.
If this doesn't bypass enough air I don't know what will! This is looking down into the exhaust manifold, so the air will want to flow out the wastegate more than it'll want to go anywhere else.
I also welded the wastegate port inside the turbo (that I spent all the time machining out before) and sealed up the wastegate hinge location.
With the hood closed the wastegate still clears by an inch or two also.
Next up was the wastegate dump. Initially I was going to have it dump into the fender well, but after watching some videos and hearing how loud it is I decided I didn't like that idea. It just seemed kind of hack and janky, and I'm already worried about how loud the truck is. Granted, the wastegate opening noise will only be at high throttle when it's already loud, but if I ever put a muffler on the truck or want to quiet it down more then the wastegate is just one more thing adding to the noise. I do love some good engine noise, but I don't want to draw attention and be obnoxious like a lot of exhausts are. So with that in mind I integrated the wastegate dump into the exhaust.
And it turned out pretty slick I must say!
It wasn't too bad, the biggest annoyance was now the downpipe has to come out through the front of the engine bay, so I had to spend more time beating the s*** out of the exhaust to get it to fit going forward. It wasn't too bad, but didn't go as smooth as I thought.
I already had a boost controller solenoid waiting for this, so I pulled the wiring harness apart and ran the wiring for that which was straight forward. This was my initial setup for the hose routing.
And after lots of driving and ****ing with things and talking to the tuner and more screwing around and trying tons of spring and no spring combinations on the wastegate, it was still making 20+ psi of boost and going insane!
And just to fast forward trying everything I could possibly think of, with the last thing being I had the boost line from the turbo running to the bottom of the wastegate to try and open it and nothing else connected, and with a single 6psi spring I was still making insane boost. I couldn't figure it out, and then it occurred to me maybe the turbo boost port wasn't actually doing anything and there's no real way to test that... So I moved the boost reference line from the turbo to the MAP sensor line and all of a sudden it only makes 6psi! I may have gone to all this work for no reason, the boost port on the turbo was never flowing any boost! I think the stock wastegate may have been totally fine even!
On a stock turbo there's some actuator thing that connects at the turbo boost port, and I had a plug I put in there since I wasn't (originally) actively controlling the wastegate. That plug had this nipple thing that stuck into the cavity with some O-rings, and I had removed the O-rings but it seemed like air could flow around that nipple. Well needless to say it couldn't, I think some air could flow since it wasn't seal, but not enough air to actually actuate the wastegate or at least not fast enough. This was easily solved by removing that nipple on the plug with the lathe.
And voila, after that I put in the 12psi spring setup into the wastegate and she makes 12psi! And the boost controller can ramp up boost now! I did a drive messing with the boost control in the ECU a bit, and it works great now. The boost controller is commanded open via PWM and that then directs boost to the top port on the wastegate which tries to close the valve, so if the boost controller isn't working no air is directed to the top and the springs open at 12psi with the boost going only to the bottom of the wastegate to try and lift the valve open. In the tune I now have it setup so at ~3psi the boost controller turns on and opens all the way, so the wastegate is fully closed to spool the turbo as fast as possible, and then the duty cycle decreases (ie lets the wastegate valve open) as rpm and/or boost increases to keep it tame. So at 6000rpm the wastegate is fully open, and at ~15psi the wastegate starts to open to prevent the boost from overshooting. My basic boost map so far has resulted in it staying shy of 20psi which is what we want for pump gas! After all this time, I finally have control of the boost the truck is making! And you might think with how much excess boost it seems capable of the turbo is probably slow, but it's in boost almost instantly, and even at mid throttle over 3000rpm it'll be making like 10psi and the truck usually cruises around at 2500-3000rpm to begin with, so it's actually really responsive. There's a second maybe of lag if the turbo isn't spooled up at all, but like in 1st or 2nd it hits really fast and really hard. So hard that today it was spinning tires in 4th gear!
And you might be thinking wow that's a lot of power for that little truck. And it was.
I let my neighbor drive it, bad idea in retrospect, or I should've been more firm about not pushing it very hard. At 80mph in 3rd gear, I think maybe the 3-4 shift, the yoke sheared off the diff.
And that was pretty terrifying since first it slammed all over, then got spit out, and we're hauling ass in a little truck with no ABS. But everything ended up fine. I think when he shifted it shock loaded it and sheared it off, since obviously the truck had been fine prior to that and I had given it lots of full throttle beforehand but it was always a pretty slow shift and at not on the power letting the clutch out. You can only go so far and so fast in this thing before slowing down, so I had never tried to really haul ass--it's not built for speed but for accelerating!
Luckily we weren't far from town, so my wife came and towed us back.
I've probably mentioned it before, but a larger axle has been a plan for a long time. I don't have any misconception about what a Toyota 8" can handle, I just didn't expect it to die so fast. I just wanted to drive it a bit with boost before going to the next stage of the build!
With that said, my plan is to just swap another carrier in or regear this one. I think even with the fatty tires it can handle the power as long as it's "gentle" (at least relative to today). Like get into gear, then give it power, don't try and slam through the gears at 7000rpm. I will eventually do a Ford 9" probably since there's lots of support and gear ratios, but that will involve finding or narrowing a housing, may as well link it then, it just snowballs fast and I haven't even completed the engine phase of the build so one thing at a time. This truck is meant to be fun, not eternally being worked on. And once I get another 8" diff, it's just fixing the driveshaft and a coolant leak, so probably end of the week she'll be back together.
The driveshaft beat up a lot of things, but the only real carnage from it was the coolant hardline got hit and that cracked a weld which is why all the coolant was on the ground. I think the engine was fine, it was turned off pretty soon after we pulled over.
The hardline should be connected to the bracket up at the top of the tube. Somehow the outside of the hardline got hit.
This section of exhaust will probably have to get spliced out. It looks fine from the wrapping, but there's probably an inch deep sharp dent under it. The tube got absolutely crunched, to the point of being bad enough to need replacing I think.
And then the driveshaft!
The ends and yokes all appear relatively fine. I'm hoping I can give the driveshaft shop the two halves and they can salvage everything and just retube it. Hell they could even cut it down and sleeve over it since only the centered is messed up.
And that wraps up the past couple days! Tomorrow should get the tires and wheels mounted, and hopefully drop off the driveshaft. Need to find an 8" diff but apparently my neighbor knows a guy selling one or two for $250, maybe they're even geared better than my diff. I think I should have it running again in a couple days, hell maybe I can meet with the tuner again before the end of the week! At a minimum the engine is running absolutely fantastic and stoked to get the boost under control finally. The rear end exploding is a shame, but should be a relatively cheap and easy fix all things considered, and time to keep an eye out for a 9"!