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Reno Air Races Engine Set Up

Plumbmaster

Active Member
I'm thinking about racing in the Reno Air Race this year and I have a RV6 (722DK) with a Titan XIO 370. Turbocharge or nitrous oxide?
It may be too late for this year, but I would like to start the conversation!
 
Kind of late to have that question for this year. Major mods need to be completed, tested and documented soon.
 
I would do a turbo for two reasons. First, I believe it is easier to dial in for a safe level. Remember, you are going to really struggle with knock sensors that actually sense knocks on these engines. A turbo can be incremented .5 PSI at a time, so can make small changes and watch for signs of detonation via EGT/CHT. Second, if you design an electric PWM valve and controller in the waste gate circuit, you can use it to get 29" of MAP at altitude for higher cruise speeds. I.e. turbo normalizer.

You may need to increase ring gaps to accomodate the extra heat, especially if you have choke bore cylinders. Look at the lyc docs and see if the go with bigger gaps on their T engines that go higher than 29". I suspect they do. The engine in the saratoga runs above 29", so may be a reference. If the gap closes to 0 under boost, you're going to have a bad day. A reliable AFR sensor will also be required to ensure you stay at safe mixture levels under boost.

Larry
 
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I would do a turbo for two reasons. First, I believe it is easier to dial in for a safe level. Remember, you are going to really struggle with knock sensors that actually sense knocks on these engines. A turbo can be incremented .5 PSI at a time, so can make small changes and watch for signs of detonation via EGT/CHT. Second, if you design an electric PWM valve and controller in the waste gate circuit, you can use it to get 29" of MAP at altitude for higher cruise speeds. I.e. turbo normalizer.

You may need to increase ring gaps to accomodate the extra heat, especially if you have choke bore cylinders. Look at the lyc docs and see if the go with bigger gaps on their T engines that go higher than 29". I suspect they do. The engine in the saratoga runs above 29", so may be a reference. If the gap closes to 0 under boost, you're going to have a bad day. A reliable AFR sensor will also be required to ensure you stay at safe mixture levels under boost.

Larry
Would it be possible to run 10:1 compression in a turbo normalized engine?
 
Would it be possible to run 10:1 compression in a turbo normalized engine?

turbo normalized means it won't boost higher than 30", which is what you get at take off from a sea level airport. Therefore, if you trust your 10:1 engine to not detonate at TO, it should be fine. That said, I wouldn't do it. That is a lot of compression to be constantly running at 100% power. I would suspect you would need to constantly throw 12.5:1 AFR at it and that would get expensive. Don't forget that at altitude, your cooling efficiency drops and may struggle to keep the CHTs in line with the tighter RV cowls.

Lycoming says 100% power continuously, but that is NOT with 10:1 pistons. Not sure there is any testing out there to make you feel safe running that compression constantly at 100% power. Most production vehicles with turbo either reduce base compression or play tricks with variable valve timing to make the turbo manageable, but that is under positive boost, not sea level atmo.
 
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I would be quite happy to run turbo-normalized with 8.5:1 compression - but I don't think I would want to do it at 10:1.
 
Turbos also heat the intake air. That's bad for detonation. What might be okay down low with little/no turbo boost will create a lot of compressive heating of the intake air up high once the turbo needs to work harder.

Since this thread is about Reno race engines, fancy high octane "jungle juice" for fuel can reduce detonation concerns. Limit MP when running on 100 octane, and give-er on race fuel for the race.
 
Ron, et al:

Here's a few data points from a Sport Class knucklehead (ok, addict ;))...and Ron, your name is familiar, so we may have chatted before. This is a great way to spread the info tho.

Timing wise, give yourself a lot of lead time...and apologies, but the ship has left the pier this year, as the deadline for PRS (Pylon Racing Seminar) entries was 4/22. That's typical each year. You'll really want to give yourself plenty of time to prepare both plane and pilot. For 2023, I'd say start...hmmmm, well...now (PRS in June 2023 will be here before you can blink...AMHIK!)

WRT to pilot experience, please check out our requirements on our website, here: https://www.sportclass.com/prs/

Formation experience is one of the big keys to success. Safe for solo in a 4-ship, performing all the maneuvers in our Formation Guidelines, is a basic min experience level to start our class Formation Warmup and move right into PRS. That doc and our training reference material are on that same website tab.

WRT aircraft, there are many layers to that aspect of racing. Just a few thoughts, from a guy that races hard, but also wears a safety/leadership hat:

- I would strongly discourage just bolting on HP (turbo, supercharger, N2O, higher compression or more cubes) to an otherwise stock RV, with a Vne of 200 mph (4/6) or 230 (7/8). While you have no doubt read or heard about 260+ to 270+ mph qual speeds in a couple RVs and Rockets, those are not stock aircraft. Mine is a 6, but it was built like a Rocket, and has a 275 mph Vne. It's also been modified extensively since I began racing too. The other fast RVs have all committed extensive time, money and testing to making their aircraft fast.

Our Sport field has been getting faster each year, and the "closer-to-stock" RVs are at the back of the field, running in our very fun Medallion heat. But each year, we all wonder who will get bumped off the bottom as more Legacies and Glasair IIIs show up (we have 9 Rookies this year, including an SX-300, 3 Legacies, 3 Glasairs, a Rocket and an RV-4). So as the field speeds up, the push to go faster, and not get bumped, has led to more forced air induction and more chemistry (N20). We do collude a bit on best practices, and keep an eye on safety (our own and each others') throughout. Reach out to us if you go this route...its important, and we want you and everyone to be safe.

- If you push to fly faster, be methodical about the process, and take airframe strength into consideration. That is a many-faceted issue all its own. The airframe is a system of systems, and one's approach to strength and flutter mitigation must approach it as such. We don't want to simply move the failure points around.

So, say you did take that approach, and are ready for more HP. Good discussion points above about FAI, N2O and Hi Comp. All have their advantages, disadvantages, and challenges (logistics and cockpit management/pilot workload).

- We have 10:1 and 11:1 motors in some of our RVs. None are boosted (TC or SC). Those that opt for boost typically drop compression to 7:1 or less. I owned and raced a Glasair III with a TIO-580 that we ran at 6.5:1 and boosted to 67" MP. The big dogs I was chasing...and couldn't catch...are well over 80", probably approaching 100"+...but they won't tell...and they go through engines sometimes. So how fast do you want to go...and how fat is your wallet? ;)

- Another data point on compression. Mine is 10:1, and when I upgraded from an RSA-5 servo on an updraft sump, to one of Don Rivera's FM300B servos and forward facing cold air induction, the MP increase I saw has led me to no longer push the throttle all the way in on sea level takeoffs, to ensure detonation margin. I run rich on takeoffs too. I'd slightly modify the other poster's comment below about 12.5 to 1 AFR to say that is best case, with good, no great, cooling. I'm closer to 10:1 on takeoff (high heat, low cooling flow), and I'll lean a bit for climb...into the 11s to low 12s, and I climb at fast speeds to keep airflow up. To get to 12.5 to 1 and not get hot requires lots of speed to cool if you're running a buffed out engine. I cruise happily at 23 squared up high, and run LOP (15.5 to 1 AFR), but if I run it up to 27 squared to race, I carefully ease it towards that goal of 12.5 to 1, tho I couldn't quite get there on most race days (pre-nitrous, more on that below).

- We have a supercharged RV-8 and a turbocharged RV-7 racing now. Both have learned a lot along the way, both have replaced cylinders, but both have also had good success and are fast. Boost-versus-compression ratio has been a part of that learning equation. So have cowling mods and AFR monitoring. It can be a high workload, especially coming down the chute in line abreast as you come up to full power, then down at 50' AGL on the pylons as you keep the engine running at its limits while racing others. Great fun, if approached carefully and professionally.

- Nitrous is perhaps the least expensive performance enhancing drug, at least in terms of start-up cost. It is logistically burdensome to use, and has cautions, just like boost and hi compression. We have race teams using a really big HP shot to qualify fast, and then using a much smaller HP shot to race a full 6-8 lap race. Some are chasing RV/Rocket qualifying records, but can't carry enough to run a full race at that hi (really high) HP, nor could they cool the motor at that HP for a full race. Others, myself included, use the same amount of N2O for qualifying and racing. I want that record too, but at a HP/Drag mod combination that can be sustained for an entire race. What I have found is that cooling that higher HP for a full race is a big challenge. We've added water sprayers, and tweaked that all race week last year to try to balance cylinder temps and trying to lean towards best power with N2O (its not quite the same place as normally aspirated, non-nitrous). Its actually a fun science. We've also had some pretty spectacular failures with N2O mods too, so this, perhaps even more-so than FAI or hi compression, is a mod that needs to be studied, planned, and executed carefully.

All the mods can go wrong quickly, so we prepare, modify, test, re-test, and race, with the goal of never having to say, "It looked really, really good...right up the point where it looked really, really bad!" ;)

I hope that gives you some good motivation, and a good feel for the field of play you are considering stepping on to. Its incredible fun, and we take great measures to ensure, and have great pride (the good kind) in, a well prepared pilot and racing machine.

Bring the surgical tube though...the drug is very, very addicting! :D

Cheers,
Bob
 
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Thanks

Thanks to all who have responded thus far about RAR engine setup. Bob, I met you once in Sacramento in 2019 during my very first clinic which was with the Beech Boys. I was flying a RV6A with an O320 and a CS prop. great all around combination, great Vans RV performance, but I soon found out that there was more to be had (power and speed that is).
The current setup in my RV6 with a Titan XIO370 and a CS prop means the plane will fly at redline if one leaves the power all the way in which I don't for obvious reasons-fuel burn, the bumps and I'm not in that big of a hurry!
Getting back to the Reno Air Races-obviously I need to gather more information and it seems to me that the best way to do that is to attend the races, get into the pits and hang out with the racers and mechanics. The awards banquet is also quite appealing!
Getting back to that Sacramento meeting, you came into the room and everyone started whispering "That's Bob Mills...head of the Reno Air Races...etc!" You then gave us a brief talk about PRS and the Reno Air Races and encouraged us newbie formation pilots.
So, its very cool that you responded to my post and I look forward to meeting you again in the future!
 
I'm not trying to get more power. I want to decrease my EGT/TIT. I'm having to run about 3 extra GPH to keep the TIT in range. I used to have an IO-360 natural with 10:1 and lean of peak it reduced the CHT from 380 to 290 and EGT. I was thinking it might help my IO-540. I can control the boost pressure with an adjustable screw.
 
Remember, you are going to really struggle with knock sensors that actually sense knocks on these engines.
Larry

Can you point me to more info on this statement? Links to articles or other backgrounds? I want to do some UL94 testing on a 9:1 IO375 and need a reliable knock sensor in order to pull it off.
 
Getting back to the Reno Air Races-obviously I need to gather more information and it seems to me that the best way to do that is to attend the races, get into the pits and hang out with the racers and mechanics. The awards banquet is also quite appealing!
Getting back to that Sacramento meeting, you came into the room and everyone started whispering "That's Bob Mills...head of the Reno Air Races...etc!" You then gave us a brief talk about PRS and the Reno Air Races and encouraged us newbie formation pilots.
So, its very cool that you responded to my post and I look forward to meeting you again in the future!

Been heads-down a bit building wings and prepping for PRS (and getting a G200 type rating so I could fail airline retirement ;) ). Finally catching up.

Ron, I remember the meeting now. It would be great to have you up to the races, and you’d be most welcome to poke around the pits, meet the racers and take in the whole process. That’s true for other readers too…we love to share the experience. And Ron, I don’t run anything…I’m just the current chief cook and bottle washer for the sport class. ;)

I'm not trying to get more power. I want to decrease my EGT/TIT. I'm having to run about 3 extra GPH to keep the TIT in range. I used to have an IO-360 natural with 10:1 and lean of peak it reduced the CHT from 380 to 290 and EGT. I was thinking it might help my IO-540. I can control the boost pressure with an adjustable screw.

For racing, we accomplish this with ADI (anti-det injection into the engine intake system, using water meth) and with water sprayed on the cylinders. Both are very effective, but also logistic hassles for a daily driver. I did a lot of work on my baffles for the Super Glasair too. Standard stuff, plugging leaks and ensuring good flow past the forward left and aft right cylinders, and between cylinders. I also worked on exit shape, and even worked with exhaust augmenters. Not sure there is any one magic trick. Power management and speed management in the climb can also be critical. In the Super Six, I have to manage my throttle hand in a sea level climb, and a slow airspeed climb is a hot climb, so I try to stay fast and just climb at 500 fpm when I don’t have restrictions (terrain, airspace or ATC). Just some thoughts.


Can you point me to more info on this statement? Links to articles or other backgrounds? I want to do some UL94 testing on a 9:1 IO375 and need a reliable knock sensor in order to pull it off.

If you’re speaking of an AFR, I’ve had good luck with a Ballenger AFR500 and the NTK sensors. If you mean a sensor that actually indicates impending detonation, I’d like to learn more about that too.

Cheers,
Bob
 
Been heads-down a bit building wings and prepping for PRS

Cheers,
Bob

Missed you at the appreciation dinner tonight.

Will you be at PRS next week?? Laura and I are going to be working pylons, we need to get together.
 
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