This HAS to be a dumb question.
 

Okay so I'm putting a borgwarner s360 on my s4 13bt FC and I wanna run about 380hp ish.. These s4 blocks tend to crack irons at 400+

Anyways, my friend was trying to talk me into buying something like the turblown stud kit and said it can be installed without tearing down the block, (just rebuilt my motor 2k ago) and I call BS. He said you just have to drop the transmission. Still the flywheel would be in the way and everyone knows how fun removing that huge nut is...

This just doesn't seem right but then I started thinking, maybe if you only did one stud at a time? :scratch: I dunno, seems like bad juju.. I would consider it if my motor was already out. I'm not gonna try it, just wondering if it's possible.

I thought the point of studs was that they acted as large dowels, meaning you have to machine the block for the proper fit. If they fit loosely and don't require machining, then they're just fasteners that don't stretch as much as the factory bolts, so you'd be more likely to crush the rotor housings if things get hot.

The engine itself isn't "unreliable" it is just not as tolerant of poor tuning. Just like any other engine, really... it seems like the people who have problems (with ANY engine) are the ones who either do a shit tune, or who are trying to get the last 5% power by leaning the fuel out or running more timing...

^ :bigthumb:

You won't crush the rotor housings using our stud kit. Now I have heard stories of this happening when people torque the engine down extremely high( think 80 ft lbs). It was evident as the engine would leak coolant once the engine cooled down. Do you think you will crush the head of a piston engine using studs? It is common practice to eliminate OEM head bolts for far superior head studs that won't stretch, even on a cast iron block with an aluminum head.

The engine will expand a few thousands under high boost pressure, this isn't something you want. Most clearances inside the engine are less than .004".

There is more information here;

Turblown 13B Engine Stud Kit designed for high hp applications

Yes, on high expansion light-alloy engines that are held together with long studs. Think Porsche/VW aircooled engines that snap the studs or pull the threads out of the case. The fasteners have to be able to stretch enough that you can put enough tension on them with a cold engine, without crushing anything once the engine gets hot.

Remember back 30 years ago when it was extremely common for head gaskets to fail without being provoked? And how that simply doesn't happen anymore? The difference is the head bolts are designed a lot differently, the paradigm for head sealing is no longer "thick bolts torqued extremely tight" but rather "undercut thin bolts that can hold the required tension but do not overtension and crush the head/gasket area after everything heat cycles".

The same thing happens even with STOCK tension bolts in a rotary. Witness rotor housings failing for width after an engine has been overheated. The rotor housings got crushed because the aluminum tried to expand more than the steel, and when everything cooled off again, it relaxed to a new thickness, which meant that the tension bolts no longer had sufficient torque on them. (Hell, I have had this happen myself. I had one engine where the bolts were finger tight after running hot.) If you reduce the fasteners' ability to stretch, you're reducing the temperature at which rotor housing damage can occur.

Probably not an issue for drag racers who will only do maybe 50 passes between teardowns, running for a few seconds from cold and so never really getting anything hot, or the street guy who never gets his car hot or really even uses it aside from an occasional short burst of power that doesn't stress the cooling ability much.

Bump. So any opinions from people who actually have first hand experience with these stud kits?

i built an engine with the stud kit, and no complaints about the kit. the engine died from ingesting a rock, or other debris though, so the studs don't make it invincible

Do you think it would be possible to install studs on an already assembled engine? One at a time?

Do you think a kit could be installed on an already assembled engine? Removing and installing studs 1 at a time?

I just ordered my set, if I was not changing rotors to low compression that is how I would have done it. After all it only replaces the studs along the inner rings, not the legs. Let me see, save $165 on a no-ring kit, you bet I would. All you have to do is remove the flywheel and replace the studs in the same pattern as the engine is torqued. Done.

Can't comment on replacing the bolts for stock-size studs with the engine still assembled, but I see no problem with it done one at a time as mentioned above.

I will say that my S4 TII with a GT3574-size turbo @ 15 PSI on pump and meth injection had no problem with the factory block (using stock-size studs). Never dynoed it but I imagine it was around 400 WHP, it ran a 95 mph pass in the 1/8th with a clutch that wouldn't hold. I only cracked front and rear irons when I stepped the turbo up to a PT 6768 and the line to the wastegate came off during a street tune. :/

I'm not entirely convinced that stock-sized studs will prevent the irons from cracking under detonation though, so if I was you I would wait until it's rebuild time and either get reinforced irons or add dowels. What seals are you running, or is the block still factory?

I'm running brand new oem apex seals on a streetported motor and I have water/meth to suppress detonation

Well it's your call, but for your intentions I'd skip on the stud kit (after having bought one myself) and run it as is, keeping boost at or under 15 psi. If anything put the money towards a reinforced rear iron if it goes. You can even change it out without completely rebuilding the engine. And be gentle with those OEM apex seals, if they go they like to take a few parts with them.

Thank you trots! That's what I was looking for. Someone with a similar setup and first hand experience. I just want to hit 400hp on the dyno for a high boost map and keep it at about 10psi low boost map for daily driving. Now the question is if the bw s360 will push 400 at 15psi. Time to investigate some more :)

i don't see a problem with installing them one at a time, you might want to drain all the coolant from the block first though.

The turbo shouldn't have a problem doing that. At 1 Bar and 400whp the S360 is in the high 60's efficiency vs a 35R in low 70's. Higher than 1 Bar pressure, and the S360 outflows the 35R (in 13B applications anyways). The turbine on the BW is a bit larger than a P-Trim in both Exd and Inducer, so won't choke it up for your goals. All in all looks like a nicely sized turbo for what you want.