EFR Wastegate Preload
 

I'm putting together a 6258 setup with a Kraken low mount manifold. I'm trying to keep the rods in the stock block until next season when I plan to put together a stronger bottom end. I've clocked the turbo so that the flapper doesn't bind at all. I'm using the low boost canister from BW.

Here's where the wastegate sits as of now.

https://cimg7.ibsrv.net/gimg/www.mia...b1f870e3cc.jpg

The wastegate rod is fairly short. At 0 preload with the flapper fully seated there's 1/2 of a thread peaking out.

The wastegate with 3 full turns (3mm) of preload which is on the low end of BWs specs is nowhere near full thread engagement.


https://cimg4.ibsrv.net/gimg/www.mia...0a0c11826e.jpg

It takes 5 full turns (5mm) of preload to get closeish to full thread engagement and ends up here.


https://cimg0.ibsrv.net/gimg/www.mia...72b33f9793.jpg

For guys that have experience with the low boost canister, is 5-7mm of preload going to be too much to keep the boost down below rod bending levels? BW claims that 3mm of preload will crack open at 6.1psi and won't be fully open until 14.1psi with 14mm of rod actuation. At 5mm that goes to 7.4psi/14.4psi but loses 2mm of rod actuation. The BW matchbot claims I'll only need 45% wastegating at 7000RPM at 12psi which given other 6258 dynos put me right around torque where the rods get sketchy.

I'm on a stock 95 NA8 block/intake but have a full 3" exhaust. I'm on a conservative tune thats pretty much Brains NA8 basemap. My old TD04 setup had no trouble getting to 15-16 psi and required porting the wastegate to keep the boost down with a 3" exhaust from the turbo outlet back.

Also, I'm a bit worried about the nut coming off the actuator rod even at 5-7mm of preload. We've all seen the threads of the nut backing off and the wastegate flapper destroying the turbine wheel. In all the EFR owners wisdom here will blue Loctite 242 do anything given the proximity of the exhaust housing or will I need something more stout to keep the nut on? I have a new bottle of Resbond that I can use but want to verify that the 5-7mm of preload is going to be ok before I chemically weld the nut on haha.

Any insight here would be much appreciated. I'm about at the point where I'm able to just send it and see but would ease my mind a bit knowing a sane starting point.

The numbers you're quoting for the low boost canister jibe with what I thought was for the medium canister, but I just looked up the BW site and what you're saying matches with their specifications.
https://www.borgwarner.com/docs/defa...tion-guide.pdf

On the low boost BW canister I didn't hit more than 8psi without EBC. I also had to add some decent pre-load to get the flapper on to the rod securely. I did use slightly thinner nuts, with a flange head, but it still took a bit of pre-load like you're experiencing. I'd suggest you run it so the rod is just sticking out the end of the nut (a little further than you've pictured) and set your boost cut to ~11psi and see how you go, but my experience suggests you should be good.

I've since swapped to the Turbosmart IWG75 dual port, it has an excellent ball joint shaft to compensate for any deflection as the gate opens to eliminate binding, and comes with a variety of different springs so you can alter how much pressure it'll take. Also various rod lengths, even the shortest is longer than the BW canister so you can better manage the pre-load. Even though it's dual port you can run it as a single port and just block off the bottom port, which is what I'm doing.
https://www.turbosmart.com/product/__trashed-52/

I just had a thought, could the "Full Stroke Pressure" listed mean the maximum PSI the canister control when using boost control? That would make more sense with what I was experiencing. Without any control you should only see up to 8psi or so depending on pre-load.

This is good to know. I'd be 100% ok with 8 without EBC. My old setup with properly functional EBC was really good. There's one or two dynos sheets floating around here of stock bottom end bois like me tapering the boost up to 12 or 13lbs at redline to maintain a super flat torque curve. I just don't want that happening too early without being able to feed it in to limit torque down low.

I just understood this as how much pressure the wastegate needs to FULLY open with the max stroke. I think in most situations with a properly sized wastegate you are never really using 100% opening unless it's creeping really badly. The BW matchbot thinks the 6258 will only need at most 44.98 opening to maintain 12psi. The maximum stroke length determining the total amount that the gate can open.

I'll start with 7mm(2 more full turns) and see where that puts me. It would be pretty ideal for my situation if that yielded 8ish psi.

I'll switch to a better wastegate solution when I upgrade internals and am ready to turn it up.

Send it. If you're happy with spool and wastegate pressure, move on. I've had this same issue, and with the rear nut flush with the end of the wastegate, I can crazy low boost, like 3-4psi. So you may be looking in to it a bit much.

Sounds good. It seems the over boosting problems people have had in the past come from binding/alignment issues. I'll update back when I get logs later this month.

Thanks for the input guys.

After installing the turbo and running it at Barbers I can confirm that the low boost canister with 6mm of preload makes 7-9psi (151-164kpa) on my setup in the Alabama heat at sea level. Thanks again for the input/reassurance.