HI Don,
I think a turbo is not a bad idea and will definitely add available horse power. But first a reminder of a few of the downsides:
Added weight and complexity
Additional cooling requirements
Some loss of efficiency due to exhaust back pressure.
Ok, now forget about that stuff and lets pick out a turbo.
Mine is not a hybrid per-se. A hybrid would be one that combines one type of compressor with a different type of turbine. BNR does sell a hybrid based on the stock turbine and they swap out the compressor for a larger one. But I have a full 'large shaft" turbo. BNR takes the stock housing, but installs a full TO4 turbine wheel (of desired trim and clip) with an enlarged axle, 360 deg thrust bearing, and the T04 compressor of your choice. That re-build costs a little over $1k. I use the stock housing because it is the only off the shelf manifold that will fit inside my engine mount. It makes for a nice tight turbo installation but is less than optimal in the sense that the housing A/R is a little too small (higher back pressure) and the temperatures don't have time to drop before getting to the turbine - being, IMHO, the cause of my turbine failures.
1) So, If I were starting anew, I would do exactly what you plan. Have separate support for the turbo, as far down stream from the ports as you can make it. Get a TO4 family or similar turbo from any reliable supplier. Search the archives, some people who know a lot more than me have given some good input on what compressor to use. Mine current one is a 60-1 which seems to work fine, but if I want to push the PR up higher, I decided that I needed a compressor that is "higher pressure". Meaning, that for a given PR the airflow is a little lower (less likely to bump against the surge line). So my spare turbo is a TO4E 46-trim and the wastegate is still in place. But I have not tried it out yet. Here is one source for turbo maps:
Here is a good low-down on compressor map reading:
If you look through the archives you can find a couple of spreadsheets that help calculate airflow. Dont forget to include the effects of altitude. But I KNOW that the 60-1compressor seems to be adequate for mild amounts of boost. Lots of other options that will probably work. Ideal orientation would put the inlet up front getting ram-air and the exhaust facing rear-ward, but compromises always need to be made.
2) wastegate: mine is fixed full open only because I dont really need the power and I otherwise dont trust myself not to use all the power I can get all the time.. Optimal would be a large functional wastegate with either automatic or manual control.
3) Correct about the solenoid. I recommend some way to shut off oil to the turbo in the event of failure.
4) I went with 2.5 because that is what the stock turbo housing provided for. seems to be adequate. I recommend going with what ever comes with whatever your turbo leaves as an outlet.
5) I down sized to the smaller stock injectors on the primaries to help with idle (small improvement). I also was noticing that when running just the primaries at above 29in the tach would stop displaying RPM. Although there never seemed to be any issue with the running of the engine, I took it to mean that I was maxing out on the duty cycle and decided to change the transition to 27in MAP. But it is best to just keep the stage point around 17-20 like Tracy suggests. I only switched mine up that high because there is a small leak in my intake (and around the throttle body axle) and fuel mists out when I am running the secondaries. So, any of the stock injectors or others of similar size seem to work fine.. unless you plan on running more that 60MAP.
6)No one with a turbo renisis that I know of, I don't see why you couldn't. There may be some aftermarket stuff out there by now.
7) Detonation is always a balance. I ran the 9.7's for a while and also had some detonation that was probably due to high coolant temps (only got the detonation when the coolant temp was above 200, otherwise I was running up to 40MAP on the 9.7's while the engine was still cool). Switching to lower compression in not absolutely necessary. I wish I knew the exact combo of MAP, intake temp, block temp, timing, mixture, spark advance and fuel octane that will reliably avoid detonation; but I dont care to find out the hard way.
Forget about the Burns Muffler. I used one and the packing only lasted a few hours. Lately I have been using just a long straight pipe (runs to just aft of the main spar). It is really cheap, wont burn out, is light weight, and works as well as any of the mufflers I have used after the packing burns out. Dont forget that your new turbo is going to take the bite out of the noise as well.
Good luck, I hope to see some progress at Reno this year!
On Sat, Feb 6, 2010 at 6:21 PM, Don Wallker <drwalker@gbis.com> wrote:
Dear list, Turbo flyers and especially David Leonard,
I've 16 flying hours on my RV-8 with a Renesis and all of Tracy's stuff and a Catto 76/88. The airplane flys great, just like an RV, no gliding time, and about 36 hours on the ground. SPECS
Full throttle 8,000' 174 mph indicated, 2450 on the prop, water 185, oil 205,
Climb out 110 mph, rate of climb, 1250'/min. Field elevation 5046.
These are not bad numbers, but I would like better. I've been influenced by some of the the local jet jocks who say that there is no such thing as too much horsepower and they are right! N113BR seems to be performing about like a 160-170 HP RV. So I am investigating turboing it! The idea is to have a little better than sea level performance on take off (designed for 210HP N.A.) and turbo normalizing at cruise. Up to 12000' would be nice.
During the air races this year, Dave Leonard showed up and I was very impressed by his airplane. He was able to turbo and inter cool it and have it all inside an RV cowl, so I'll likely base my installation on his. Plus, he has been through the learning curve of 3 or so turbos so he knows what to do, what not to do and what would be better if he were to do it all over again.
I've spent the afternoon looking through the archives, reading as much as I can find about turbos, and downloading all the photos I can. Here is what I am tentatively planning on doing.
Get one of Techwelding's Renesis exhaust flanges made from 304 SS and have my local waterjet guy copy it and make one out of 321SS. I'll weld 321 SS and manifold it together and run it into the bottom of the turbo that will sit right in front of the exhaust. The turbo will have additional support. Run the turbo outlet air from it through a stock RX-7 inter cooler sitting in front of the left cheek opening and then out to the right side of the engine, probably routing it under the PSRU and then up to a throttle body and manifold. Then four al tubes over the top of the engine into a cut down and welded up stock RX-8 intake manifold. The exhaust out of the turbo will run down and out in the usual center of the back of the cowl opening. I am thinking of trying one of Burns Stainless all SS mufflers. It is basically a glass pack, but instead of glass, they are using stainless steel wool and they say it is holding up for the rotary racers. They make it any length you want and is about 4 lbs with their SS vs 9 lbs with the hushpower 2 I'm using now. The combustion air intake to the turbo will be on the aft left side of the cowl via an NACA duct opening as Dave's is.
The oil cooler will have to be moved to under the engine. I will build up a fiberglass scoop, probably based on Van's scoop and modify it to have a bigger opening and be farther forward, closer to the prop. I will probably have the oil cooler made a little larger (Techwelding) than the one I have now.
That's the basic idea at this point. I'll finalize my plan, prebuild as much as possible before tearing the airplane apart and try for as little down time as possible. I'm looking for the list's critique here, plus questions that I will have missed. The following are a list of questions that I have.
1. Which turbo should I use, which orientation and who should I use to do the work, plus what is the approximate price? TO4 hybrid? Dave and Steve Brooks mention BNR turbo as a modifier. Who manufactures the turbo?
2. What is the ideal situation with a waste gate? Full open or not, or, or?
3. I read about a N.O.oil line solenoid to the turbo bearings. I assume that if the Turbo fails, you turn it on to the N.C. position to prevent oil from being pumped down your exhaust? I assume the oil that is used is routed back to the sump.
4. What size exhaust is optimum? It seems Dave is running 2.5 inch.
5. What size throttle body should I use and what would be a good one? One throttle body or two? 4. What size injectors should I use, and where should the secondaries be placed? Dave is using 480cc and staging is at 32 inches. Are you using the same for the primaries and is there an idle problem with the larger injectors?
5. Anyone out there turboing a Renesis? Anyone flying one?
6. My compression is 9.7 to 1. Any problems with this higher compression ratio as long as I use an inter cooler and keep the boost no higher than 35"?
And lot more questions, but that's all I can think of now.
So If any of you can add any thought, let me know.
Don Walker
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
|