DEAD DIFF!
wonder what caused that to happen if it wasn't seeing wheel hop...

 

Damn have you ever experienced wheel hop? Any diff braces or worn diff mounts? I've never seen that kind of carnage from NOT launching. Makes me wonder what damage the previous owner did with the car.

 

I kinda have a theory. The engine is bolted directly to the frame, the tranny is too. Then the diff had solid delrin bushings. Add this up with a dogbox that shifts ultra fast... maybe it stressed the diff housing from repeated shock? Like a impact effect. On the diff I just installed, I kept the rubber bushings. Hope it helps!

It is using our tubular diff brace, and mounts were delrin. I am with you on never seeing that from not launching. I actually had this diff totally apart and it looked flawless when I was putting the car together.

 

makes sense. It kept flexing enough that over time it weakened to the point that it snapped.

 

I really like what you guys did with this car. Your skill and knowledge really show in the finished product. Really impressive, I'd love to see it in the flesh.

 

Time for an 8.8.
Great build man.

 

Thanks! If you come out to Deals Gap it will be there

Yeah maybe sometime in the future a 8.8 will go in. The ratios available alone might make it worth it.

 

Yea I saw that, I am very surprised. Having greater port area in the lower RPM band should have resulted in lower velocity and in turn power/torque using the logic I (and most I think) have always been accustomed to! Do you find a big difference in idling or throttle response with the PP's capped off? Or any significant difference to justify controlling the PP's separately from the sideports?

Some food for thought: If drastically increasing overlap, port area and in turn air velocity didn't impact engine output below 7500 RPM, what will?

P.S. nice work on the diff! Some decent carnage there for sure

 

Careful with the position of that hose clamp. It looks like it is resting right against the fuel hose. Vibrations eventually may cause that to rub through. Will probably take a long time but murphy's law and all that...

 

This is strange! Your engine and tranny are mounted solid. The delrin bushings virtually eliminate any twist in the diff. The only thing left is your tubular PPF. I know for a fact that under heavy acceleration the front of the diff pinion tries to move UP and not down (as I have a bent diff brace with poor welds to show for it). Since my engine is moved back, I originally had to make a diff support brace for the rear as I didn't want to shorten the stock PPF at the time. I designed it to hold the diff up. Well apparently after one hard run, I heard a knock in the rear and limped back to the shop. After peaking underneath, I could see the diff pinion was tucked hi in the tunnel with my bent brace holding it up. It was so high that the drive shaft nearly severed my emergency brake cables. I mistakenly engineered my brace to support the weight / acceleration load in the WRONG direction. I've since re-designed the brace and it will probably hold the weight of a car. So with that said, are you sure your tubular PPF isn't what's flexing too much?

 

Did the rear end have any slop in it? A little slop could create some shock maybe.

 

Thanks for the lookout, but that is a aluminum fuel line that I put a 1/4" thick heavy duty cover all around it. She is safe for sure



No slop at all. Before I put it in, it measured out completely within factory specs. I actually had two diffs to choose from and this was pretty much perfect in all ways.



No, I can jack up my car from the diff brace as well. I cant even see it flex at all. But its not a issue with the diff case. The problem was the torsen assembly broke, which dropped a gear out of it, and then got sucked up into the ring and pinion. Of course a 1" diameter gear can go through, so it forced the diff case apart. And now we have all the broken bits

 

You know I never even thought about the internals just taking a ****. Mine had too much play (it wasn't back lash) so I recently replaced it with an S4 turbo II unit. I don't anticipate this kind of explosion anytime soon.

 

The S4 clutch type has a MUCH stronger case vs the torsen. I may have to go that route, but first putting in a Rx8 4.44 and its factory torsen. After using a Kaaz vs. torsen, the factory is so much smoother in power delivery mid-corner. Hopefully it doesnt crack mid corner on me........ that would be a BAD day! lol

 

New to this forum, but would like to day that this thread was the most knowledgeable I have read for a while.

I have a question though. Is your side port semi pp setup producing more power than what a full pp set up can produce?

 

Awesome build. Id be interested in a 13brew semi pp intake setup. Have you made any as of yet? Have any pictures? Would you need a lower intake manifold as a core? Do you know if the 2" shorter lower intake manifold runners would also benefit the 13brew lim? What kind of engine management are you using to control the peripheral port throttle bodies operation? I look forward to seeing your car at Seven Stock this year.

-Dave

 

Thank you! The answer to that is yes and no. It is producing higher numbers than the majority of full race 20b p-port engines. I know of at least one race 20b full p-port that is making about 30hp over mine. Its a $55k mazda backed lemans project though. But I am not finished getting more power yet

I am working on one sometime soon, so dont have pics yet. Correct we would need your lower manifold as a core. Going 2" lower would benefit the REW as well, but with the semi p-port its not as needed. I am using the electromotive TEC3R, which controls the 3 additional injectors in a separate fuel map. The p-ports themselves are attached mechanically, once past half throttle they start to get pulled open. Very simple design that works great.

 

So P ports aren't the be all and end all to na motors then? Very interesting. What have you done to you side ports? I take it they're not standard size?

 

Hmm I didn't know that about the housing differences. It's scary that the torsens can just give out like that. I mean no amount of external bracing could prevent the internals from failing like that. This makes me glad that I have the clutch style now. I only swapped the internal torsen with the S4 clutch style. I've seen some pics that some one built a diff reinforcement brace for the drag strip. I'll try to find the thread. It ties into the bottom of the diff and wraps around to the back cover. I was going to make one for myself if I ever turboed mine in the future. I don't think it's necessary for my NA application at this point.

 

Right now with Logan's set-up, your getting the best of both worlds for a NA rotary. You get the drivability of the side ports and peak power of the PP. Even thought these PP are smaller, a regular full size PP would never have the bottom end like Logan's. Stay tuned! The NA rotary is headed for new and uncharted territory.

 

My sideports are our "circuit" port. A medium- medium/large port by most peoples standards.

Yeah, it scared me too! Once I get the Rx8 rear end, going to take apart the torsen and fully stress relieve it and maybe have it shot peened. That or just get a Series 4 turbo II clutch type. Used to have a Kaaz which is unbreakable, but for road racing I wasn't a big fan of how it would react.

Uncharted is so much more fun huh?

 

Yes it is!

 

Have you achieved any more power yet?

I have just been looking at the cost in the 20b section on here and it seems that getting an engine built over in the states and sent over here to the uk will actually be cheaper than getting one built and installed by a rotary builder.

20-30,000 dollars is a lot cheaper than the 20-30,000 English pounds!!

How much would your final engine setup cost?

 

Have not had a chance to get back to the dyno for quite some time now. Too much going on in the shop. I did build a new exhaust system that maybe gained power and leaned out the tune.

I also am almost done with the new slide throttle setup. So hopefully more power numbers will be soon!

Total cost for a engine identical to mine which would have the following parts-

Circuit Port on intake and n/a race exhaust port
Fully balanced rotating assembly
9.7:1 n/a rotors
Clearancing the rotors
Ceramic apex seals
3 new rotor housings
Semi p-port machine work to 3 housings
Race rotor bearings
All new staionary gear bearings
Mazdaspeed drysump front cover
all suction tubes modified for 20b
Oil modifications
Coolant modifications
Labor to tear down, clean, prep, blueprint and assemble the short block

$15,500 total (doesnt include the stock 20b longblock due to constant price changes on JDM engines)

We are working on a E-tech series that is much cheaper-

Parts that differ-

Carbon apex seals
Keep OEM housings
Uses a external 3 stage drysump system

$8,800 total (without 20b longblock)

Both capable of same power. Just the carbon apex seal engine will need refreshed after a couple seasons of racing. (replace carbon seals)

 

Even with the price of an ecu it is quite a lot cheaper having an engine built over in the states.

Obviously there's fabrication to fit an engine but anyone that has got mechanical ability would be competent at doing said task.

Keep us posted if you manage to dyno the car again, like I said before this is a very informative thread.