Hmmm...you're real bright, aren't you? Cause the LS1's 6000 RPM redline is SO much higher than the 8000 RPM redline in the stock rotary engine.

--Alex

 

T'was a joke, simple.

 

8000rpm is only on the S5 NA with the manual transmission, ALL other FC's have a 7000rpm redline. An S5 would be the logical place to start a high rpm build, not an S4, it would seem that you're making it harder for yourself with the chosen engine. For a budget build, just use S5 internals and live with "only" 8000rpm, 500 shy of the stated goal. The S5 fuel cut is at 9000rpm or so, so you could rev it to 8500 or beyond. I've had mine to 8500 indicated (the tach will be optimistic) a few times, but I'm not brave enough to find the limiter.

Light rotors, better e-shaft, etc will likely all cause the budget to be exceeded. Examples:
RB light rotors = $2250
2 piece e-shaft w/center bearing = $2500 AUD + $$ for machining of center iron

 

Yea I think when you get into $2200 for a set of rotors that takes the practicality out of 99.5% of engine builds, lol

I don't think rotor weight would have that much of an affect on safe redline as long as the rotational assembly is properly ballanced.

So if someone wanted to build a low budget engine with a slightly higher redline an S5 would be the place to start then?

 

If you only want to go slightly higher and do it low budget, then use a set of aftermarket hardened stationary gears w/3 window bearings, deep groove competition rotor bearings and higher oil pressure (100 PSI). Port accordingly (early opening, late closing).

But you will still need an EMS system that can handle the higher RPM.

 

Well that is the route I went with this build. I highly doubt 100 psi of oil pressure would be of any benefit. I'm not allowed to give exact numbers but our cup engines revving past 8k with 800 hp and bearings that are smaller than I've seen in any 4 cylinder 60 psi is more than enough to get the job done. Judging from the bearings that came out of my rotary with 160,000 miles on them it looks there is no stress on the bearings at all compared to a piston engine so the bearing and oil must be supporting the loads very well. Above 60 psi you start blasting the bearings with so much oil you can actually erode the surface off, just like taking a garden hose and blasting it into the dirt. That and you create additional pumping losses the higher in psi you go.

Has anybody on here tried to do research on how little apex side clearance you can run before you have problems with sticking? Are there any issues with the stock CAS when trying to rev higher than 8k?

 

The thing is, the rotary is not a 4 cylinder. Oil in the rotary is responsible for cooling the rotors as well as lubricating the engine. Some 30-40% of engine cooling is done by the oil sprayers that coat the inside of the rotors. More oil pressure means more flow to the cooling jets and a stronger oil film on the bearings. There's a reason Mazda went to 100 PSI oil regulators on the 93+ engines...

I've never heard of any CAS issues at high RPM. In fact that CAS is a pretty solid piece of engineering...

The only way to adjust apex seal clearance is to machine new apex seals.

 

Oil is very important for cooling a piston in the exact same way as a rotor, especially in anything high performance. Heck putting an oil squirter hitting the back of the piston on a high boost application could probably increase it's longevity by double or more. There is a large difference between needing oil pressure and needing oil volume though. Of course if 100 psi is what is needed and it proves to cause bearing damage then you could always route more oil to other parts of the engine. This raises a factor I havn't considered yet. I'll be running an RX-8 eshaft in a S4 motor with S4 oil pump. Should I try to use a different oil pump or modify the regulator since the oil jetting is different??

For the apex seal clearance you could buy 3 mm apex seals and lap them down to the desired tollerance for your 2mm application with a surface grinder. Seal sets from Atkins rotary are the same price for 2mm and 3mm apex seals so if you didn't have access to the machinery needed you would have to pay a shop to do it and make sure they lap half the material from each side.

 

You can use the TII oil pump if the engine is NA. It's a higher flow pump.

Shimming the oil pressure regulator for higher pressure is easy:
http://www.aaroncake.net/rx-7/shimoil.htm

 

lol, I feel stupid now. I'm pretty sure the reason why most piston engines have the eroding problem while the rotaries don't is because piston engines usually have one oil hole per journal while the rotary has two so the bearing itself would only get blasted with 50 psi on each side (sorry, I tend to think outloud more than most, lol).

When shimming the oil pressure regulator according to your write up, would it be easier to use an endmill since you wouldn't have the angle on the end of the drill bit?

I can hardness check the apex seals before and after to see how tightening the clearance affects heat transfer but don't have a clue how I would determine if the seals where chattering or not. Have any ideas on how I could do that without new rotor housings or trying to construct a home made spintron? 0.0

 

Apex seal chatter shows up as a series of horizontal lines in the rotor housing. Very easy to spot.

You can use whatever you want to remove the split pin. I used hand tools since that's all most people have.

 

Anybody reading my last post ignore the part below, I didn't know wtf I was talking about, lol.

I will be using used rotor housings which already have chatter marks in them so I won't be able to see if new ones arise later when I take it appart, unless of course they are chewed all to hell lol.

 

We had the oil requirement thoughts floating around our shop. Guys that have come from stock car efforts, 500+cu in drag guys, and I think I knew the most about rotaries and I had forgotten most of that. Well conversations went like, "A V8 only needs about 10psi per main bearing at xxxx rpm and you only got 4 bearings..." So the owner of the car set the drysump pump up for 80 psi give or take. I said, "Well, I guess we'll find out"

So when we tore the engine down after it spun a bearing after a few races... It was not a volume issue the car now runs 125psi and gets run up to 9500rpm a lot.

 

I did. And its functional, and Im hoping I haven't already responded in this thread.

I have an S5 N/A with a moderate street port on the primary and secondaries, and a bridge on the aux. The car idles like stock (a stock 25, meaning it hunts. bad tps signal), but pulls much, much harder from 5500-7k. I havent gone all the way to 8k yet because the car is still in break in. Im running no cat, stock exhaust, stock intake, stock everything. The stock intake is definitely a restriction because when the VDI kicks in there is a very very noticable kick in the pants. After I get the exhaust sorted out, and Zeal comes out with a PnP MS then Im going to tackle the intake.


BC

 

we have some rotary engines in PR that makes more that 15,000 RPM with out balancing. A normaly one would be 10,500 with some ports. That's apply to NA and Turbocharges engine.

We never change anything about the engine oil system or rising the pressure. Only we check the engine timing and the engine end play to avoid damage to the bearings. Also we use stock rotors, stock engine bearing, stock flywheel and Racing Beat underdrive pulley

 

I assume you're talking about drag cars... 15K for 7 seconds is not the same thing as 15K for 2 minutes :p

 

When I worked at Victory One Performance we would make stuff there that would run all day in 8,000 hp engines but wouldn't make it half way through one qualifying lap in a Nextel Cup engine.

I don't see why you would need 125 psi in any piston engine unless there where rules that wouldn't allow you to make changes that would fix the reasons why you would need that much pressure to begin with. If you can get the job done with less oil volume and pressure you will make more power.

I was talking to some of the engineers at work and reading through some books and really you cannot compare the oiling system of any engine to another that isn't the exact same design. How much pressure each bearing needs is dependant on a lot of things including bearing diameter and length, sustained and peak load, oil hole size, numbers, and locations; if the bearing is used on the crank, the rods, camshaft, eccentric shaft, rotors etc, where the bearing is located in the oiling system etc....

For example the experience I mentioned before about erroding away the bearings at 60+ psi I found out there where several solutions to that. They first tried making the oil hole larger which focused the pressure over a larger area, the bearing did look better after testing but the gains where not that great. Later they tested and found out they still had plenty of volume at the end of the oil circuit so they decided to keep their original design and instead decrease they're pressure 10-20 psi, not only did the bearings look even better than the other test they also picked up some power and had less mechanical problems with parts wearing out in general.

How exactly does the VDI mechanism work? Is it a vacuum actuated piston and cylinder inside the intake? I've been trying to find an S5 manifold to go on my S4 but havn't had much luck.

 

No one has ever had a problem with eroding a bearing on a rotary due to oil pressure. It's never happened to me, and I've never done it. The factory engines from '93+ all run 100 PSI of oil pressure...

The Factory Service Manual contains a good description of the VDI in operation. Yes, its just a vacuum actuator with a cylindrical valve.