Ok, there is a lot of discussion going on right now with the groundzero LIM for the FDs. Groundzero claims that the difference in the length of the front and rear secondary runners acounts for leaner mixtures and higher EGTs (by 250 degrees if I remember correctly). They claim that their manifold equalizes the EGTs between the front and rear rotors. I'm not doubting the quality or merit of their manifold, just the claims. My reason is because the rear rotor breaking apex seals isn't just an FD thing. Every turbo rotary I know of seems to break the rear apex seals more often than the front. I don't think the TII LIMs have the same length difference as the FDs, so what is causing this? I always assumed it was that the coolant flowed from the front to the back, and that the rear chamber was a little hotter, but I'm no engineer either.

I dont remember exactley what they said when i was talking with them at ss7, but they said they had EGT gauges coming from each rotor. And if i remember right they also mentioned the path of the runners, that the front was a more direct path (cant remember exactley, was a long time ago)

On the FD the rear secondary is a straight shot, whereas the front is a good bit longer and has a bend in it. But that still has nothing to do with why 13BTs blow the rear rotor.

I would have to say it is due to higher oil temps the rear rotor sees because the oil is routed to the front then teh rear first.

P'cola FD,Dec 21 2004, 09:56 PM



Ok, there is a lot of discussion going on right now with the groundzero LIM for the FDs. Groundzero claims that the difference in the length of the front and rear secondary runners acounts for leaner mixtures and higher EGTs (by 250 degrees if I remember correctly). They claim that their manifold equalizes the EGTs between the front and rear rotors. I'm not doubting the quality or merit of their manifold, just the claims. My reason is because the rear rotor breaking apex seals isn't just an FD thing. Every turbo rotary I know of seems to break the rear apex seals more often than the front. I don't think the TII LIMs have the same length difference as the FDs, so what is causing this? I always assumed it was that the coolant flowed from the front to the back, and that the rear chamber was a little hotter, but I'm no engineer either.







The first thing that comes to mind is the hotter coolant affecting charge temperature and always detonating the rear housing before the front.



Second would be the rear housing deforming more than the front as torque tries to warp the rear housing and iron, and break out the dowels. So all of the causes add up to a bad deal for the rear housing.



Coolant on the Lemans engine goes in the cool side and out the hot side on each housing. So I suspect the NA engine suffers more from the coolant temps than the torque problem.



If you had two injectors that flow a bit more than the others, I would put them in the rear runners. Just a thought.





Lynn E. Hanover

Wow, Lynn E. Hanover knows a lot about engines, but he can't quote for ****! https://www.nopistons.com/forums/pub...DIR#>/wink.png Just giving you a hard time Mr. Hanover.



Speaking of EGTs, what temperature would let you know that the rotor is gonna die? Hah. I'm using my EGT to monitor the rear rotor (as suggested by a few people) and I was just wondering how I would know of a dangerous condition...

In my exeprience with two-stroke twin and triple racing engines there was a somewhat common problem of crankshaft flex. If you're going to hole a piston in one of those motors is almost always the rear cylinder. When the crank flexes the rear piston ends up coming slightly out of time with the front leading to more spark advance and ultimately detonation.



Now I'm not saying this is THE reason for any rotary failure but we have all heard of e-shaft flexing and that would lead to the same condition.

what is everyone opinion on intake runner length in a turbo app? in a na set-up the shorter runner will breath (make torque at a higher rpm) than the longer one which will make similar power but at a lower rpm. yes these are simplified ideas.

Yeah,



My 20B also had a dead rear and front rotor, only the middel one had 8 bar compression..



The cause was that the intake gaskket between the engine and the LIM was broken at the side of the secondary inlet so that rotor had been running lean... the middle rotor didn't had this, when I opened up the egine, the sideseals and corner tips popped out like it was just rebuilded... In comparision with the rear rotor: I couldn't get one sideseal out in one piece and with the front one broke after trying half an hour per seal...



This was with stock turbo's and ecu so I think it was running only 0.5-0.6 bar boost... So how the hell is a stuped paper intake gasket going to hold the boost pressure when using a big single?

My 20B's middle rotor was in better condition than the front or rear as well. Interesting.

Since when was quoting abilities on a forum needed to be able to help people with serious technical questions? Lynn is one of the main reasons I and many others visit this forum. Keep the cheap jibes to the other forums please.



Bill

There are 2 ways to approach a turbo setup. One is to look at it as a normally aspirated engine with boost. In this view you try and place the torque curve of the engine to get more torque around either the spooling point, or a suitable peak torque point that gives a nice wide power curve. The stock inlet on turbo RX's is designed around this and is tuned for a normally aspirated peak around 4500 RPM.



The other way is to look at the flow into the engine and try to maximise that, on the principle that, once you have the turbine spinning the more air you can get in, the more power you can get out. In this view then the actual length is not a huge issue. Getting a good straight shot into the ports with minimal turbulence is the key focus.



To a degree which one you subscribe to depends upon your budget and how much boost you want to run. Under 1 bar and you are firmly in the former camp. Above 1 bar and you are in the latter.



I have to admit to not seeing much I like from the stock inlet manifolds on turbo engines, but I come from a background where the sort of cars I play with have individual runner setups.



One other thing to think about. Looking at the V8 world, anyone serious about squeezing the max from their engines uses individual cylinder fuel and spark trim to get around thermal differences and VE differences due to manifold designs. If you are doing the same with a rotary and not looking at an ECU that can handle this you have to realise that the edge of the envelope will be not be as far away as those who have. Getting the inlet and zorst so that both rotors see the same VE and playing around with coolant paths so both housings are at the same temperature will get you close, but at some point you will need to move up to the big boys league to get the last few %

Actually the rotors get fed reasonably evenly with cooling oil,the main feed being in the rear plate just under the oil filter housing that feeds the eccentric shaft rear main bearing and then also passes oil into the shaft itself,and thus to the rotors and their bearings.The oil also passes along the top dowells from the rear housing and feeds the front main bearing in the front plate too and into the eccentric shaft and the rotor etc...

On the top of the front plate(Side housing) there is an oil feed for the turbo/s too that also takes the oil from where it comes throught the top dowells.So the oil from here feeds both the eccentric shaft and rotrs and bearings and turbo.

Hope this makes sense.

Regards

Carl

with that in mind...



trying to keep in some type of a budget, do you think it would be more valuable to try to "cc" the intake runners, to match volume after the tb, or would port matching render you similiar results?



My thinking is... if you can match the volume and runner length is similair, then a very similair volume of air should enter each rotor, and (providing back pressure from the turbo manifold is similiar) rendering the air/fuel ratios more similiar and making your motor a little more effecient by making both rotors produce 50%. Or at least that's the idea.



Or would it just be more effective, to get a divided turbo manifold, and put an 02 in each runner and trim the injector of the richer running rotor.

The part about "giving you a hard time Mr. Hanover..." That was so you would know I was kidding. Wow, lighten up some. I wouldn't have posted if I didn't respect the fact he was here educating us.

'giving you a hard time' Means exactly that where I come from. In your particular idiom the meaning may have been inverted to mean 'just kidding', but please do not assume that, on an international forum we will all read it that way.

The quote thing is my fault. I remove the command because it seems more natural to see the question and answer as though it were a conversation rather than a contest of some kind. So in that reguard, it is outside the structure of the site and I should not do it.



There seems to still be a problem with the site.



I did not include a picture with that post. Where a picture of a wheel came from I cannot say. I do not own a copy of it, so I am sure it did not come from here.



It seems to me that a 250 degree disparity in EGTs indicates quite a bit more wrong than a slight difference in runner shape.



A closer look at the question is in order. What kind of failure of the rear rotor are we talking about. I would expect the housing distortion induced failure only in a turbo engine. Also a detonation type failure from hotter intake charge, only in a turbo.



lubrication failure of the rotor bearing is more likely in the front rotor. Thus the universal use of an additional oil line to the front main bearing, and a long standing trend to very high oil pressures.



Lynn E. Hanover

I didn't send that one either.



Lynn E. Hanover

(no picture posted with this reply)

since the forum crashed the attachments have been coming back to the designated posts. (to the post number that they came from)

I thought that was a pretty universal term, I guess I'll try to be more clear next time. I wasn't trying to disrespect anyone, as indicated.



PM sent.





PM sent.

i didn't read all of this BUT



you do know the knock sensor is on the front rotor housing.......

what Lynn has said here is what i've read so far, and i'm inclined to believe it over the intake manifold thing. i'm not trying to discredit it, because on the Mark II MR2 Turbos manifold runner length is an issue, but i'd tend to believe the difference in temperatures and torque deformation have more to do with it.



i never thought about that ... using bigger injectors for the rear. that's an interesting take.

Bigger, yeah...



If you're running for exemple 440cc on the first and 550cc on the rear, this difference will be way to much I think...



But what I understand on rotor failure with my 20B is: the rotor was full of carbon, apexes didn'tcome out after a night in parts cleaner, non of the side apexes survived it...



The front rotor had this also but not as hard, while the middle was as new!



But because there was alot of carbon on it, it could also be that there was something wrong with the ignition or apex lubrication system...



The was no wear on the apexes, the were like new... Not broken or so thus detanation wasn't the cause eightes..



Rub

No two injectors flow the same amount of fuel at any one pressure. So you have a collection of them flow tested and run the ones that are close together. When you get them back they will be marked (tagged) with their flow rate. So some will be richer (flow more) than others. It is the higher flowing set that could be run to the rear rotor. Not a bigger injector. More like the 339cc actual vice the 441cc actual.



Balancing the injectors is a big deal in spec Miata racing. They are digging for one extra HP.



Carbon build up has been a problem from day one in the rotary. Pure oil burns pretty well when heated. Motor oil has a long list of additives that have nothing to do with good clean burning characteristics. Just the opposite. They contain chemicals that keep them stable at high temps. The long chain polymers that make 10W40 work are among these. So we inject this oil into the combustion chamber and wonder why there is all kinds of crap all over the rotors. A good synthetic is even worse. It can withstand even higher temps before it starts to break down.



Premixing top oil is preferred over injecting crank case oil. Plus, if you premix, you can run a straight weight synthetic in the sump, and a clean burning 2 cycle oil in the chambers. Premixing is a giant pain in the ass, if the car is a daily driver.

For a weekend racer it isn't bad. I use 8 ounces of Redline racing 2 cycle oil in each 5 gallon can of fuel. I use straight 40 wt. Redline racing synthetic in the bearings. That 8 ounces is more than required for the street, but we try to stay above 9,000 RPM, and we have almost no wear to deal with year in and year out.



Richard Sohn makes adapter kits that fit between the stock oil metering pump and the front case that allows for using 2 cycle oil from a container on the fender or fire wall. That way you check the oil level once a week and you can run a full synthetic in the sump, without fouling the rotors with carbon.



Here is a gag that works for me. This is not for street cars that have converters, because it will plug the converter with carbon and sludge.



My first rotary race car had just a very tired junk yard engine with 9MM apex seals. It was so tired that in cold weather I would pour hot coffee and motor oil into the carb to get it to start. One outcome was that on disassembly the engine was clean like brand new inside. At least the rotors were clean. The sump was full of sludge as usual for an engine that had never had an oil change.



Then a friend that builds small block Chevys told me close to the same thing. If he has to R&R an engine for overhaul, he warms it up, and very slowly pours a pop bottle (soda in some areas) full of water through the carb. On tear down there is not one speck of carbon or even staining in the combustion chambers.



Saves a day of cleaning rotors or pistons. Only if you are tearing the engine down that day. Otherwise rust will be a big problem. It may also damage all kinds of things on a stock engine and may hose some of the sensors. But for off the road engines, and piston engines it is amazing to take apart a 100,000 mile V-8 and see a new looking combustion chamber. If you have ever blown a head gasket on a piston engine, remember the cylinder that failed a gasket into the water was clean?



Just something to think about.



Lynn E. Hanover

thanks for the clarification Lynn, i , too, was under the same misunderstanding of what you said about the injectors.



this should get pinned.

Wow, I'm glad you brought this up. Although this is probably off topic, I'm wondering how this premix thing is going to work for my car. I have a 13b Cosmo that I'm currently finishing up the wiring on. It's in my FB.



At any rate, I don't really "get" the premix thing. I've removed the OMP and oil injectors because I know it's not very reliable and because I was advised to do so. So the idea is to run a different oil in the pan (sump I guess) than what you mix in the tank? Is there a method to identify which oil to run?



TIA.



I should add that this car is not a DD, more of a fun weekend, gonna smoke some Z06s, car.

You would be down to personal favorites in the oil world. The highest film strength goes to synthetics hands down. So if you care enough to use the very best, it will be a synthetic. The better 2 cycle oils are vegetable based, and the synthetics have all of the molecules the same size, so they have a higher film strength.



So for the sump, in colder areas, a multigrade synthetic. In warmer areas a straight weight synthetic. For the top oil any brans name 2 cycle oil is fine. And since you burn it in less than one rotation anyway, a synthetic is a bit pricy. We do use the synthetic Redline, but we are trying to stay above 9,000 RPM.



I have yet to have a lubrication related failure, so I don't know what that looks like in a race engine.





Lynn E. Hanover

Hah, you're getting all the attachments!



Thanks for the advice.

Lynn E. Hanover,



I know that the engine oil isn't a good combuster, but my point was actually that only the middel rotor was "clean"



So if the oil would have been the cause, the middle one should also ave been bad..

But maybe not if only the middle il nozzle was failing..? damn, but I'll just remove the omp crap and run premix https://www.nopistons.com/forums/pub...#>/biggrin.png

Me too.

That does have something to do with it. A 13BT has similar issues. That bend in the secondary runner will cause just enough turbulance to slow down the air flow into that rotor. With the rear secondary runner creating less turbulance to the rear chamber, the air will fill the rotor chamber more efficiantly than the front. Thats why the rear runs leaner. Turbo, lean, and rotary don't mix. Rob Golden said at sevenstock that the LIM's design was an issue. With two EGT probes installed before the turbos, the rear had higher EGT's. He compensated by consentrating most of his porting in the front chamber and increasing the injector duty cycle in the rear to add more fuel. This is the way he attempted to balance things out.

All that being said , is the Groundzero LIM functional in it's defense of rear rotor temps , and is it worth the $$$ ?? https://www.nopistons.com/forums/pub...1047683561.gif

Anyone ??? https://www.nopistons.com/forums/pub...1047683664.gif

Someone please answer me so I don't get stuck with an expensive boat anchor if it doesn't work properly https://www.nopistons.com/forums/pub...1047683358.gif

According to groundzero and Pineapple it is worth it. I'd like to see some more testing, but if nothing else, it has to do some good, as the runners are equal length. After some more testing and folks have had it on their cars, I may buy it. Fred, if you're worried about not spending money just yet, you can tune your car safely, to the power output that you're wanting with the stock manifold.



I'd be willing to bet that the manifold helps with the rear rotor running lean, I was just curious if that is THE reason for it running lean/blowing up, or if there were other factors.