Bigger studs will let you clamp a bit harder to hold the housings in thier place but you are still relying on friction to keep the plates from shifting and stressing the dowels. This is what makes dowels sooo much better. I just did some quick calcs and even with a single tubular dowel pin (sleeve around the bolts) made of a good tool steel like 4140 you should be able to get about 8,000 lb of shear strength out of each one. That is not to say that the housings wouldn't just deform or crack like the one one near the oil filter stand, but each additional dowel distributes the force. Larger diameter studs may clamp a little harder and add a little torsional rigidity but if you have enough room to bore for a bigger stud why not use a hollow dowel? That's my plan anyway. Not necessarly every one but at least the 3 or 4 bolts near the oil filter stand will be getting this treatment. I don't know if it has been tried or not but it makes sense to me.

 

I thought the entire point of the over sized studs was that they would have a slight interference fit when the engine was at operating temp and would act like dowels.

Thats what someone at mazdatrix told me a while back.

 

Studs as dowels... It's possible but studs aren't usualy held to tight tollerences. A dowel pin is precision ground a stud is not. You would have to mic each stud and find a reamer to match accordingly. If the studs are infact made from precision ground rod then that's a different story. You mentioned that the interference fit was achieved at opereating temp. A hole will increase in size with temp (less interference), granted at 180F in holes that size expansion is almost negligable even in aluminum.
Any way you can accomplish additional mechanical engagement of the two mating surfaces will help. I'm not about to call BS on mazdatrix or you slo.
From the first hand accounts on here latley I think it has become pretty obvious that an S4 and some S5 housings are not sufficient for higher levels of boost and/or tollerance of poor tuning. Either get the good housings or plan on finding a way to beef up the weak rear housing. I have a lot of time and $ in my housings (due to not knowing the weakness of the S4 housings) and I have access to a machine shop so I will take the housing beefing route. I'll admit that I am probably one of the few cases where modifying the S4 housings is a better deal than just upgrading to the housings with a thicker casting in the dowel area.

 

Studs as dowels...uh no. IF you stack all the plates of the engine and peer down into the holes for the tension rods, they are nowhere near uniform throughout...they get bigger and smaller as the rod passes through each plate. Obviously there's no way a bigger stud can act as an interference fit when the holes are not all the same size and do not all line up perfectly.

 

Well that would be why you would have to machine them right? Its not totaly inconcievable that you could machine all of the tension rod holes lo line up perfectly, and fit with a very close non interference fit around the stud.

Hey RXBeetle you can call BS on me or mazdatrix if you want, I havn't had any original thought on this matter, I'm just trying to stimulate the conversation.

from the mazdatrix website:

"The High Strength Oversized stud kit eliminates the need for doweling the engine block. All studs act as dowels which massively increases torsionial strength 70%. Rotor housing deflection reduced - increases apex seal life. Less material machined from housings and plates than with doweling, reducing the possibility of cracking."

Studs as dowels, thats exactly what there claiming.

link: http://www.mazdatrix.com/studkit.htm

 

it is because the torque of the engine is more than stock and the s5 one is thicker

 

JUST wanted to bump this up and see what the pro's though, are the mazdatrix OS stud kits able to do what they claim?



Quote:
Studs as dowels...uh no. IF you stack all the plates of the engine and peer down into the holes for the tension rods, they are nowhere near uniform throughout...they get bigger and smaller as the rod passes through each plate. Obviously there's no way a bigger stud can act as an interference fit when the holes are not all the same size and do not all line up perfectly.


Well that would be why you would have to machine them right? Its not totaly inconcievable that you could machine all of the tension rod holes lo line up perfectly, and fit with a very close non interference fit around the stud.

Hey RXBeetle you can call BS on me or mazdatrix if you want, I havn't had any original thought on this matter, I'm just trying to stimulate the conversation.

from the mazdatrix website:

"The High Strength Oversized stud kit eliminates the need for doweling the engine block. All studs act as dowels which massively increases torsionial strength 70%. Rotor housing deflection reduced - increases apex seal life. Less material machined from housings and plates than with doweling, reducing the possibility of cracking."

Studs as dowels, thats exactly what there claiming.

link: http://www.mazdatrix.com/studkit.htm

 

to quote myself haha

after looking at the mazdatrix description it appears that they have actualy have a very good product. (couldn't load the page yesterday ??)
Like I said studs aren't usualy ground, it appears that these are (and hardened) which justifys the cost. This isn't all-thread from Home Depot. Shear strength is about 19,500 lb. EACH! The down side is that machining all the sections of the engine is not easy.

RotaryResurrection mentioned
Correct-a-mondo except you can bore/ream the holes to the proper fit @ 0.500" since the stock bolts are only 10mm (0.394")" daimeter

A machine shop should be able to bore and match and ream the holes to 0.500" but it is no where near as easy as just running a drill/reamer through each hole. To maintain a very straight path and an accurate hole diameter through different materials requires boring each housing seperately (A drill will flex and just follow the misallignment). That's what 17 studs through 4 housing, so 68 holes matched and all lined up to the threads in the rear housing and don't forget the two existing dowels. With a good jig and X-Y readout (and/or or a cnc table) this is not out of the question but there is very little room for error. Bring your check book and a case of good beer for your machinist.

 

Now that we've established that this isn't something that could be done on a drill press, is anyone offering this as service? As a one off job this would obviously be expensive.

 

I just payed $1300 to have a 13b & 20b machined for the oversize 'Guru' studs.

 

WOW! You should've shipped to me. I already have the program in the CNC And you better pay attention to the sealing issues you will have with the fancy 12point nuts, washer, o-ring things. I found a better sealing solution. If you need replacement studs give me a call. Have fun putting that 20B together done enough of that here, fun fun fun.

-S-

 

We've done the oversize studs for years, though we usually only do about four of them in the critical places. We found an ideal stud off-the-shelf from ARP that is actually a head stud for a Top Fuel Dragster. One of the important factors we found was that you have to be extra careful about rotor to housing clearance because some combos will cause a problem, as the housing does not deflect away and create clearance. In those cases where the clearance is too tight, you may need to machine the rotor or try a different combo of parts.

To be honest, we don't see much need to do this on anything under 700 RWHP for a 13B-REW. At that level, you start seeing excessive dowel pin wear. Below it, the dowels don't wear significantly and the FD casting is up to the task...unless you really screw the pooch on tuning and then you have bigger problems. We have done it on less powerful engines, but it was just excess for the sake of excess.

The FC stuff is a good application for the oversize studs. Most S5-T motors have better re-inforcing, but at this point there are so many combo-burrito motors out there that you can never tell what you will find. We have recently started modifying 13B-REWs to be a drop-in for an FC. It takes a bit of fabrication but it is a less expensive option than oversized studs when all is said and done. We charge $499 for the basic modification to the plates. Unless an oil pan is custom made, you run an FC front cover and stock FC oil pan.

 

FC stuff all the way for sure, I just do the sixteen centre bolt pattern on most. It is more than enough as you stated. We also have only done the typical "few". I get lazy though and want to use the same tool all the way around the back We just make our own studs. It became a much easier supply and demand issue with trying to get them from overseas.

 

HaHa!

+1 on the case of good beer!

Lets just say, possibly, that someone here could, because of the wonderful attributes of the CNC machining center, machine all plates with location and size precision that could easily accept a tighter stud to hole clearance.

How tight cuold you run it?

 

Just a guess, but as tight as you would run dowl pins.

 

Boingers allow for the different expansion rate between aluminium heads and cast iron blocks by useing extra clearance in bolt and dowel holes, and graphite impregnated gaskets.

I guess my question here is; Can the doweling/studding/pinning be too tight for the two different types of materials? And, does the close tolerance fit of the factory dowels contribute to the dowel pin failure in the rear plate?

 

The thermal expansion of aluminum is more than double that of cast iron. This sure doesn't help the problem of the dowels having to soak up that force. The holes also open up due to thermal expansion but it's insignificant. There is a pic from some mazda SAE papers somewhere but I haven't been able to find it again. It plots the forces exerted on the the rotor housing due to pressure with the inner surface of the housing as the -0- of the graph. Guess where the big spike is? right by the doomed dowel area. I wish rotaryrefs was still up I think that's where I saw it.

 

Hate to pull this thread out the gutter but would it be possible just to dowel pin the rear housing? I've got my motor pinned all the way through to the front section but since the rear is the one that cracks could you just pin the rear section. Dowel pinning an engine can be done with a drill press. I use a 39/64 drill bit and then ream it with a 16mm reamer.

 

Could you take some more pictures of the motor?

 

What shot are you looking for? Tell me and I'll post them up.

 

Slo:Gotta read my last post.\/\/\/\/\/

to quote myself haha

after looking at the mazdatrix description it appears that they have actualy have a very good product. (couldn't load the page yesterday ??)
Quote:
Like I said studs aren't usualy ground, it appears that these are (and hardened) which justifys the cost. This isn't all-thread from Home Depot. Shear strength is about 19,500 lb. EACH! The down side is that machining all the sections of the engine is not easy.

 

RXbeetle do you know the name of that SAE paper, i can pick em up pretty cheap and i would be interested in buying this one.

 

I have been using the studs even before mazdatrix had them.The studs from mazdatrix are made from GURU.

I have been drag racing for a while and in drag racing there is alot of load to the
outer engine plates.

I have tried every possible combination ,you name it , FD S6,FC S4/S5,6 port Gsl SE,
Non turbo blocks with turbo,and there is a flex problem.I have cracked all of them,
even the J-specs just trying to R&D.I even tried to use a custom oil pan with a 1"
plate made of solid aluminum and guess what it cracked too.

It has to do like everyone says fuel/ign tuning and it has to be right.I have noticed
when i tried to boost near 30psi without dowels or studs ,it cracked so easy when put under heavy load.

I got the biggest scare of my life a few years ago when i spun my car at the track doing well over 120mph at the 1/8 mile and guess what it was,it was the front iron that cracked completely off (93 FD engine)at the dowel pin exposing the dowel shooting 100Psi of oil to the front of car while in motion and spun on my own oil.I never even notice no hint of noises or pinging it just broke like butter.I am glad i
did not hit anything, just did a couple of 180's and some crap on my pants.

I keep that iron i broke as a reminder and pull it out once in a while to give some stories of that day..Ever since then i take the studs or dowels seriously when racing.I use the Guru oversize studs(mazdatrix) on my current motor and haven't
broke any in 5 years.My current boost as if now is 45-50psi(Y2k-88mm truck turbo) and i will take it even higher next couple of months and guess what motor it is,Its an 85 GSL-SE 6 por motor.I will eventually be switching cars in the next year or so but this is my test car for now.This was the last engine i had when i broke all them other ones and it has been in my car since then.

 

Rene,
I remeber that day you spun out I even have it on video. One hell of a save from smacking the wall.

 

Hey 61620B, about how much power and TQ are you making?

What fuel?

Are you reaching any other limiting factors, such as rotors denting, or rotor housings pushing away from the rotors?

Just curios