R

RV8R999

Well Known Member
N309MK received her airworthiness certificate this morning and flew early this afternoon! Woo Hoo!!!

Conducted fast taxi in accordance with my test plan at 15,20 and 30 mph and survived :)

First flight took off and immediately had high CHTs, especially on #2. Went as high as 465 on #2 for 30 second and 420-30 on others. This engine was broken in on my BD4 for 70 hours and all CHTs ran in the low 300's. Its an Xp-360 with one slick and a P-mag. I pulled power to idle asked the tower for an immediate landing and did my first wheelie in an -8. What a nice machine!!! :):):)

I had the pmag in program A which I believe is the most aggressive so I shut down and switched to program B. I removed the cowling and checked baffling. Its all very tight. Oil temps never got above 170 - I have the oil cooler located low on the left engine mount fed by a 3" SCAT and a glass duct on the outlet.

I put it all back together, let things cool a bit and tried it again. Temps were lower but #2 still went up to 450 in the climb. I leveled off at 2000 throttled back to 1700 and stabilized at 100mph. All other CHTs eventually dropped to 310-320s while #2 stayed at 410 for about 10 minutes and then finally dropped to about 350-360. OT was 164 and pressure at 70. All EGTs were within 50deg of each other from between 1150-1250. It really surprised me how long it took for #2 to cool compared to the others. Level at 2000 ft I advanced throttle to 24" and 2600 RPM and stablized at 189MPH all CHTs rose with 1,3 and 4 going to about 380 and #2 going to about 410.

Once on the ground and the engine off all CHTs drop and equalize quickly within 3-4 degrees of each other.

One thing I didnt do was glass then ends of the inlet ramps as I figured they are between the baffling so who cares..am I wrong here?

Any ideas on why #2 would be so much higher? The Oil cooler inlet is at the rear baffle at #4. I have the stock VANs baffle kit with the tall **** in front of #2. Have any of you guys cut this down and did it help? I can block off some of the oil cooler inlet to strike a balance between oil temp and CHT..

Anyway...despite the high CHTs I have the RV grin (photos and video soon)!!!

Thanks for all the advice, help and healthy debate along the way!!!

Ken
 
RV8R999 said:
One thing I didn't do was glass then ends of the inlet ramps as I figured they are between the baffling so who cares..am I wrong here?
Click to expand...

These have been open on my -6 for over 17 years. That shouldn't be a problem.
 
Ken thanks for detailed post. You will conquer those temps soon. Congratulations with first flight let the PH1 begin...
 
Great News.

Congratulations!
Its always great to hear of a first and successful flight.

I don't know the whole picture of your engine installation but my
IO 360 one Mag one LSE always had #2 cylinder higher than the rest
until I added a spacer between the #2 cylinder and front baffle.
My top cowl inlet ramps are glassed in.

Sounds like you are having fun while you are doing your very exhaustive
Testing. Good luck tweaking you temps.
 
N427EF said:
Congratulations!
Its always great to hear of a first and successful flight.

I don't know the whole picture of your engine installation but my
IO 360 one Mag one LSE always had #2 cylinder higher than the rest
until I added a spacer between the #2 cylinder and front baffle.
My top cowl inlet ramps are glassed in.

Sounds like you are having fun while you are doing your very exhaustive
Testing. Good luck tweaking you temps.
Click to expand...

I agree. Adding the spacer will lower it significantly. I had the same issue although not as high a temp as your seeing. Also check for any slag between the cylinder fins/heat sink.
 
Congratulations Ken - always great to hear of another successful first flight!

The temperatures are puzzling - you seem to be checking the right things in terms of baffling. FYI, I have never had any dams on my baffles, and CHT's are all fine - you might remove them and see if you get anywhere. I agree that glassing the ends of the upper cowl tunnels doesn't do anything if you have the baffle seals set up so that air doesn't get to the ends. Frankly, I can't see how you'd be getting that high of CHT's due to baffling problems if you have built it anywhere near stock.

I guess that leaves the "what's different" thought - and the PMag does throw a variable in there with regards to timing. I know that they have been improving their product over the years, but we have seen lots of reports as it has matured about high CHT's due to timing errors. Something to check anyway.

Good luck, and test safe!

Paul
 
RV8R999 said:
can you guys describe this spacer for me please? thanks!
Click to expand...
The baffle is attached to the back of the #3 cylinder by a screw. I believe it may be a pan head. Looking on the inside of the baffle at the cylinder attach point, there should be a spacer or washer between it to allow air to pass. If the baffle is flush to the cylinder, you need to add one or two washers. Sorry I don't have a picture handy. I couldn't believe adding a washer here would lower the temps, but it did. Seems like it dropped 15-20 degrees. Hope this helps.
Maybe someone else has a picture. It's a common issue with the RV baffling. I'm surprised the instructions haven't addressed it after all this time.
 
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Hey Dan, are you talking about the #3 Cylinder (right rear), or the #2 (left front)? I know about the spacer on the back of #3 - not sure I understand #2....

Paul
 
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Yeah my #2 cyl is fwd left side as viewed from the cockpit looking forward. Here is a shot of the #2 Cyl baffling with the ****. Honestly I'm not sure why it is there and questioned this when installing but just left it as is. So do most of you remove this?
2pyc789.jpg
 
the more I look at that Da*n the more I think this is the main culprit. Look how much it blocks the main cooling fins of the #2 cyl I think I'll just remove it entirely and see what happens. This if FUN :)
 
mags?

I agree with Paul, your mags may have more to do with this than your baffling.
However, notwithstanding the above, adding a washer between the #2 front baffle and the cylinder will lower its temp about 15 to 20 degrees.(It did for me).
If you look at the cylinders you will notice that on one side the fins are about an inch longer than on the other side. On the #2 and 4 the short side is on the front and on the #1 and 3 the short side is on the back. Adding a spacer between the #3 or the #2 cylinder and baffle, the latter of which is most often the offending hot cylinder, is an easy way to open up the passage way for air.
I am afraid removing the baffle above the ramp will have little effect.
While adding a washer might seem a quick and easy fix you must also enlarge the mounting hole where the front and rear baffle components connect. It is no big deal but you cannot just stretch the baffling forward without relieving the resulting stress.
 
The airdam is not the problem....many out there flying with it. My #2 is my coolest and the airdam is there like the plans show. Lots of people shield this area with either the airdam or aluminum tape.

From looking at your pic, it looks like you did not cut and install your baffle seals where they will block the inlet ramps. There are two ways to do this one way blocks em and one way does not. You mentioned that you did not cover the inlet ramp sides. You may be loosing a massive amount of air thru those ramps if your seals are not installed where they never allow the air to get to the ends of the ramps....
 
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Thanks for inputs! I'm at my hangar ( love my iPad) I used a popsicle stick to check ever cal cooling fin and did find a few pieces of junk here and there and a good size piece of foam under #2 spark plug boss. I also used a fine file and really cleaned out those fins just under the spark plugs. Was surprised how much slag was still in there. I also blocked off about 20% of my oil cooler inlet and 50% of the heat inlet. I'm not sure I buy this idea that cooling flow needs to be maintained through the heat muff. It is all SS and EGTs don't get even close to those margins especially that far down stream. Anyone block it off and have problems? Anyway im to limit the changes I make with each test to minimize the variables. I'll leave the **** alone for now. The baffling is tight and every gap hole corner edge has been fully rtv'd Goin flying to check it out.
 
On an RV-8 with standard cowl, the inlet ramp tunnels on the top cowling really do need to be closed off.

The velocity of air that blows sideways thru them is strong enough to blow past your rubber baffle seal on the outboard ends, and cause it to fold over and leak air into the lower cowl area even if the baffle seal was curved inwards before flight and looked like it ought to hold the upper air pressure in. The rubber baffle seal ends up losing that fight.

On my friend's new RV-8, we have not yet glassed the tunnels shut, and every time we remove the upper cowl, you can clearly see where air has blown the upper baffle rubber material outwards, and thus is pressurizing the lower cowling area with high velocity airflow leaking from the upper area. We're still getting good CHTs despite this, and have finally solved our high oil temp problem by biting the bullet and replacing the oil cooler with the expensive SW unit that should've been bought in the first place.

On the cabin heat muff around the exhaust pipes cooling airflow deal, we simply removed the muff for Texas summer flying, and will worry about re-installing it when winter temperatures get here. The first couple flights we had it installed, without any cooling airflow, and you could really see the thermal discoloration starting to show that it was getting cooked pretty good.
 
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Neal@F14 said:
The velocity of air that blows sideways thru them is strong enough to blow past your rubber baffle seal on the outboard ends, and cause it to fold over and leak air into the lower cowl area even if the baffle seal was curved inwards before flight and looked like it ought to hold the upper air pressure in. The rubber baffle seal ends up losing that fight.

On my friend's new RV-8, we have not yet glassed the tunnels shut, and every time we remove the upper cowl, you can clearly see where air has blown the upper baffle rubber material outwards, and thus is pressurizing the lower cowling area with high velocity airflow leaking from the upper area. We're still getting good CHTs despite this, and have finally solved our high oil temp problem by biting the bullet and replacing the oil cooler with the expensive SW unit that should've been bought in the first place.
Click to expand...

That's interesting Neal. I am not going to say you're wrong, by any means, on your friends airplane, because the nature of the baffles and baffle seals on these airplanes are such that no two are exactly alike. But on my plane, the outer ends of the tunnels have never been closed, and even down here on the gulf coast, I have never had high CHT's. The inside end of the tunnels are, in fact, closed, because they taper that way, and are glued down to the top cowl in the center, so there isn't any way for the air to go anyplace. I can tell (from the patterns on the inside of the top cowl) that no air appears to be leaking by the seals.

Again, not saying you're wrong on the specific airplane, just letting folks know that what you're observing (or what I am observing, for that matter) is not true on every plane. There's probably more variation between baffles on RV's than any other part of the plane!

Paul
 
Darned dam ...

I have an IO-360 with horizontal induction, therefore the intake and baffling are different from what you've shown. The air cleaner is positioned right at the left cowling intake. There's nothing blocking air to the #2 cylinder but an angle bracket that supports the baffling and the air cleaner.

I'm no engineer, but it sure seems pretty obvious to me that having a large piece of metal blocking air flow through that cylinder might have a noticeable effect on cylinder head temps.

While you may indeed have baffle seal issues, it sure seems like a reasonable idea to cut down that dam a little and see what happens. If your #2 CHT lowers, then cut it down some more until it's in line with the other cylinders. If not, you can always rivet a piece of aluminum back in there.

During my Phase I, I noted that my #1 cylinder was running too cool and had to add a dam to block some air flow through that cylinder. Now, all CHTs are pretty even.
 
The airdam does not block flow through the fins on the cylinder, it makes it go thru them where it does most good.

There are lots of planes flying around both with and without these airdams, this is not the smoking gun....
 
Brantel said:
The airdam does not block flow through the fins on the cylinder, it makes it go thru them where it does most good.

There are lots of planes flying around both with and without these airdams, this is not the smoking gun....
Click to expand...

OK. If you say so. Just offering what popped out as a possible solution from a clueless builder. The same principle worked for me on the opposite side, even though you say that it can't work. :rolleyes:
 
I never said it can't work....It is there to fine tune not drastically change...Most people need em on #1 because they get too much air on that side and that is the side with the long fins forward....It also helps push some of the air on that side up and over to #3 instead of straight down thru the fins of #1.

The proof is in the fact that there are tons of airplanes with em and tons of em without em all claiming to be successfull in cooling their cylinders. That tells me that they must not have that much of an effect on overall cooling performance.

N8RV said:
OK. If you say so. Just offering what popped out as a possible solution from a clueless builder. The same principle worked for me on the opposite side, even though you say that it can't work. :rolleyes:
Click to expand...
 
I re-timed the slick mag and checked all plugs, #2 exhaust flange for leaks, cleaned out all cooling fins and ensured I was timed correctly on the Pmag and set it to normal mag timing by removing the MAP input (this makes it more or less like a traditional mag).

With the cowling completely removed all CHTs hover around the 280-290 region with #2 being the lowest. When I run-up to higher power setting with cowl removed #1 and #2 are the coolest by 15 degrees or so. This alleviates any concern I might have had about something WRONG with the #2 cyl.

As soon as I put the cowl back on the #2 goes to low 400s even at even very low RPM so I'm convinced its a baffle issue.

I believe it is most likely the inboard right inlet behind the spinner. I'm going to add more baffle material in this area. Maybe even put baffle material on the ramps so it overlaps the baffle sides..dunno.

Does anyone have a picture with the cowl off so I can how you managed the front section. Thanks!

Ken
 
RV8R999 said:
. . .

As soon as I put the cowl back on the #2 goes to low 400s even at even very low RPM so I'm convinced its a baffle issue.
. . .
Click to expand...

Curious, Where the CGT sensor pigtails connect to the lead going to the instrument, is there a chance that the lower cowling is doing something to it? If anything happens to change the connection, it will affect the indication. Just a thought.
 
I checked this and have no issues with wiring. I'm pretty sure my problem was the fwd inlet baffling - especially inside section nearest the spinner. I've added an alum extension and more baffle material to really seal this area up. It makes putting the lower cowl on a bit harder but if this solve the problem it'll be worth it. I also removed the air damm in front of the #2 cyl. If weather gets better I'll try it out this morning.
 
Rubber baffle seals?

OK, maybe a dumb question here.

In your picture you posted there is no rubber baffle seal material attached to your baffles.

Is this just an earlier photo before you installed the rubber material?


Ted
 
Ted, yes I did installed all the baffle material but it was funny you thought I hadn't. This would have been a really big oooops.

Flew again today after adding some extra baffle material in the inlet section and removing the #2 air damm.

All CHTs were much lower but #2 still wants to go to 440 in the climb. I was climbing at 90 MPH to 2000ft. What airspeeds do you guys climb to keep your temps reasonable? Anybody use a cowl flap for climbs?

In level flight at 150MPH CHTs are 300,345,310,305 so I'm pretty comfortable with the baffles with these temps.

I have my oil cooler with 3" inlet blocked off about 1/3 and still Oil Temps never get above 186 (at full power level flight). I did build a cooler outlet scoop with about 12.5" of outlet area. The Oil cooler is a S/W 8406R mounted low on the engine mount with inlet coming off the baffle behind #4 CYL.

Next issue - I'm new to FP props so at 2000ft PA WOT MP is 27.5" with RPM wanting to go to 2800 and A/S accelerating through about 204MPH IAS. I have to throttle back to 24"MP to keep her at 2700RPM topping me out at 193MPH IAS. Does this mean I need to have the prop re-pitched?
 
I climb no slower than 100kts in my RV7 for extended periods. If I do, my #3 will go above 400?. If I keep the long climbs above 100kts, #3 just hangs around 400? till I level off.
 
Overspeed FP prop

I used to have an 86 inch pitch Sensenich prop with my IO 360, which would overspeed as well. I assume you have the stock 85 inch pitch. You'll may want to repitch it. Recommend you complete your flight testing and develop your mission requirements, before you decide on prop mods, etc.

Also, I usually climb of 110-120 mph in order to keep things cool and it gives better visibility over the nose.. Fly Safe.

Randy
PS I converted to c/s. Don't want to start that war again...
 
Ken,
My 8 is essentially the same.
Something still does not sound right. 440 F for a 2000 ft. climb?
While 90 MPH is my Vx I use 110 Mph, my Vy as a climb speed or faster for a cruise climb.
Even with 100 degrees OAT I would not ever see 440 F on any of my cylinders, certainly not for a 2000 ft. climb. There has to be something else.
On the other hand your cyl. temps for cruise seem kinda low, not too low but low.
Add that washer that has been mentioned in previous posts, its a no cost one hour baffle adjustment.

Prop RPM at altitude is one of the compromises of a fixed pitch prop.
Before you go and repitch that prop consider the diminished climb performance
of a prop that has been pitched for cruise.
I left mine alone after finding my engine runs extremely smooth anywhere between 2600 and 2700 RPms. This way I get just about 200 MPH out of it at
altitude and retain a superb climb performance.
 
I agree something does not seem right about a 440 temp on such a short climb out. But at the same time as you mention the level flight temps are just fine. If I didn't know 100's of -8s were flying with the same cowling I'd be concerned the lower inlet shape was not optimized well.

I'll add the washer and see. What can it hurt? Thanks!

Ken
 
For climb, I know you'll be doing your own flight testing Ken, but I have found that best rate of climb is between 100 - 120 knots, and the change is very flat across that range. 90 mph is VERY slow if you are looking for best rate, and might be contributing to the overheat. The RV-8 climbs so quickly (regardless of speed), that best angle is almost irrelivant....

Paul
 
Thanks for all the info.

The weather cleared for awhile so I took her up again. Confirming the boost pump does increase the indicated fuel flow however, there was no corresponding change to either RPM, EGT or CHT so this is a sensor issue - very odd.

This time I climbed at 120-130mph and #2 stayed at about 400deg F. It is still about 30-40 degrees hotter than the others so I'm not done tweaking but at least I've got it controlled. Honestly, I'm amazed that at 140mph and WOT I was still climbing at 1100FPM.

I can honestly say today I really enjoyed flying my plane as I was not focussed on a perceived CHT problem but just enjoying the thrill of flying. My plan is to flying a few more familiarization hours before beginning the formal test process.

I did a few stalls - clean 65mph slight buffet with the break at 63MPH. Full flaps resulted in a slight buffet at 54 and break at 52mph. Very docile without tendency to roll in either configuration. Stall recovery was immediate upon relaxation of back-stick with as little as 1/2" fwd displacement.


Today was the first time I've tried T-n-Goes. First 10 were wheelies with various flap configurations. In calm winds full flap wheelies require so little effort I hardly felt I needed to be in the plane. 1/2 flaps required a little more positive fwd stick at touchdown but were equally simple. Tried a couple of 3 Pt landings and ended up bouncing 4 times (I'm counting that as 1 approach with 4 touch-n-goes). I believe this is mostly a sight picture issue and the willingness to transition from a forward scan of the runway to the side. I'll keep working on both.

I'm still trying to decode operation with a wood FP prop. As I mentioned earlier, at high speed the prop will tend to overspeed to 2800 rpm but in a WOT climb at 125 I only get about 2300 RPM. So I suppose if I wanted to achieve a full power (2700RPM) climb this would require a reduction in pitch which would then result in an overspeed at even lower A/S at WOT. This is the compromise correct? I'm happy with it, just not used to having to think about an overspeed at WOT. I'm going to set up some audible alarms and warnings to keep me honest.

Of all the airplanes I've flown, my RV8 fits me the best and suits my desires for an airplane perfectly. I swear it has nothing to do with all the time and money I spent building it :)
 
It sounds like your 8 is very much the same as all others.
It is an exceptional aircraft.
You are correct in your assumption regarding the prop.
Many will tell you not to worry about over speeding the engine at altitude and I am sure you will test that out.
The compromise is not only in performance but also in the price of the installation, about $5000 to $6000 dollars less than a CS prop.
keep us informed about solving the #2Cyl temps.
 
Ken,
Several guys have mentioned inserting a spacer (often a washer or two) between the cylinder head and the baffle wrap on the front side of #2 (note, the rear side of #3 is identical).

Here's some explanation of the problem and another approach to a cure. The key is to understand how a good tight fit against the front side of the head blocks airflow to the fins on the lower side of the head. And BTW, the CHT probe is down there.

http://www.vansairforce.com/community/showpost.php?p=284884&postcount=1

Spacing the whole baffle section away from the head allows air to the lower fins. It also creates a big leak in the area without fins. However, it is known to work and easy to do.

And congratulations on flying it! I'm about a month behind you.
 
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baffle spacing

Dan,

As always your description and methods are first rate! The baffling in your linked thread is a bit different from mine (must be engine specific) but you've given me an idea which will accomplish the same result without adding a washer or creating a leak. I'll take photos of my solution ASAP.

If I can get #2 CHT to match the others I will be able to climb at any speed within the planes flight envelope rather than self impossing a restriction necesitating a climb in the 120-130 mph.

Good luck with the airworthiness inspection...not as if you need the luck.

Regards,

Ken
 
congrats ken!!

Airplane looks sharp!!

Sounds like you are well on your way to solving the CHT problem.

Have watched your progress via the forum and was awaiting your reaction. It is always a thrill and taking a few hours to enjoy the grin before the "rigors" of phase one is a most expected timeout.

I find in my 6 that getting smooth 3 points is tough (becuse of the often described tendency of the tail to touch first). One way is almost similar to a helo approach to a run-on where you hold the nose up to slow down and arrest the decent, then at the last minute smoothly lower the nose to get a simultaneous three point run on. It is very tricky though, because there is no collective to catch it with. Inevitably, smooth ones are rare and somewhat a matter of luck (for me anyway). Grass helps (softens the tail and main touchdown). Carrying a bit of power helps. Easiest is to stick with the wheelies on the hard surfaces.

Continued good luck and fun with one of America's great freedoms. You've earned it!

Next up - Dan H!!
 
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Thanks Gary - I still feel a 70kt run-on in an H-60 is much trickier than these rigid wing things but you are right having a collective to bail me out is nice!

My problem is when I find something I can't do well (such as 3-pt in a RV8) it becomes something I cannot let go of until I can either do it well enough or it gets stupid...I'm not there yet.

When is the next Florida RV fly-in?
 
Ya, I know what you mean

and I predict you will see it get stupid fast. The stall attitude is just too nose high, and the performance difference between a non-stall 3 point and a tailwheel low wheelie is just too little to worry about.

Fly on !!!
 
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