New Rotax 670 Install

75 posts in this topic

Posted

To that 100 pounds you can add 16 pounds for the  muffler and another 10-20 ponds to the water cooler(s) and water.

When  removed my 582 to install the Jabiru 2200 I weights everything and came up with 130 pounds. I did have two cooler in serieds for sufficient cooling and this took 1 gallon of water at 8 pounds. The Jabiru weighs 135 ponds full up so  didn't have a weight problem, but the CG was farther forward for the Jabiru.

Jon M

 

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Posted (edited)

 

nlappos

The heat from your muffler will go directly into the belly mount radiator. Been there..done that.

Best cure is to have a gap between the fuselage about the same distance as ypur current stand off. Your current solid stand off can cause the air flow at the belly mount to stagnate because the air flow at the top is blocked.

I had an aluminum sheet that took the heat from the muffler and directed it over the top of the cooler through the gap. This was on my model B when I was driving a 582. The model B had a side mount radiator that wasn't efficient. So I added the belly mount. with the gap to let the aluminum sheet guide the muffler heat over the top of the belly mount.

If you don't direct the muffle heat over the belly mount you will run hot.

That said, your cheek radiators should be plenty of cooling. You just have to be sure the air moves through them...not around them.

We fly in the heat of SoCal and we removed the belly radiator from the MK4 my friend bought. We could not get the temps down.  We bought and installed the cheek radiators. They worked well. So we removed the belly mount and saved the weight and drag.

Finally, your transponder antenna will partially blocked by the belly mount. Again...been there ...done that. So this info from experience.

John M

Edited by skypics

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Posted

skypics,

We are talking about a 670 installation, are you? What engine does your friend have in the Mk IV that works well without the belly radiator? The 582 has 41% less power thus 41% less heat, I think that's why you think it works, as you do. Have you run the 670 or are you speaking about your 582?

With a 670, in the new 1"  lower position (see photo below), the belly radiator works well, I can climb continuously at 60mph at full power on a 95 degree day at 7000 feet and engine water temp remains in the green.

I have blocked off the path around the nose radiators, too, so they get all the air, but with my 670 they are insufficient without the belly. I am thinking of removing the belly in the late fall and re-installing it in the spring.

Nick

 

IMG_0879.jpg

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Posted

Nlappos

I was referring to the 582.

I see your belly mound has been modified since the earlier photos . You have left a much larger gap and maybe that allows the heat from the muffler to avoid the cooler.

You do see how the heat from the muffler will flow back to the cooler?

Looks like a LOT of extra drag, but you are satisfied and that's what matters.

John M

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Posted

With a 670, in the new 1"  lower position (see photo below), the belly radiator works well, I can climb continuously at 60mph at full power on a 95 degree day at 7000 feet and engine water temp remains in the green.

 

 

Very cool

What kind of climb performance are you seeing with those numbers?

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Posted

TJay,

I am getting 550-600 fpm at 6000 feet and 95 degrees, with about 950 lbs GW. That is a bit more than I got at sea level with the 582, with the same aircraft. That checks out, since I am now at about 9000 DA, so the 670 is putting out the same horsepower at this altitude that the 582 did at sea level. See above, I posted fuel flows as well.

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Posted (edited)

niappos

What is the HP of the 670 and what did Rotax do to get the increase? Larger pistons? Different stroke? Higher RPM?

John M

Edited by skypics

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Posted (edited)

skypics, 

the 670 has 670 CC's, like the 582 has 582. That's the trick. The larger pistons and stroke of the 670 buy you the extra HP. The engine has been widely used in snowmobiles for decades. For aircraft use, the 670 gives 92 Horsepower at 6350 rpm, vice the 65 HP at 6500 for the 582 blue head.

The 670 weighs about 10 lb more (all inclusive) than the 582.

From the Rotax specs:

582 bore 76 mm, stroke 64 mm

670 bore 78 mm, stroke 70 mm

Here is Rotax Rick's specs page:  https://rotaxrick.wordpress.com/operate/

The 670 has "RAVE" valves that retune the exhaust with rpm, so the gas mileage stays low across a wider rpm range. These valves also add power, because they keep the exhaust properly tuned.

Edited by nlappos
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Posted

Just got offered a sweet deal on a Hirth 3202 fuel injected 55 hp engine that's hard to pass on. Since a lot of model 2's fly with a 503, it should work fine. It has less than 50 hours on it and I've seen or watched most of the 50 hours being put on it.  Air cooled so no plumbing or radiators involved. Weight is approx. 98 lbs flying weight.  In a lightly built model 2, it should have plenty of power and max RPM is 5500 instead of the usual 6000 +.  It sounds quiet and smooth thru all RPM ranges, a lot quieter than my 503 was. maybe I got lucky.

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Posted

I know this is an old thread but was wondering what you thought of your 670 a couple years later?  Still loving it? I just got an unassembled kit fox 4-1200 with a new in box although 20 year old 582.  Was thinking about the 670 since the motor should be gone through anyhow.  
 

thanks. 

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Posted

I know this is an old thread but was wondering what you thought of your 670 a couple years later?  Still loving it? I just got an unassembled kit fox 4-1200 with a new in box although 20 year old 582.  Was thinking about the 670 since the motor should be gone through anyhow.  
 

thanks. 

I love mine. It starts and runs great, and delivers the power it is supposed to. The rave valves cut fuel consumption so it doesn't burn much more than the 582 (at the same power). It also only weighs maybe 10 lbs more than the 582, for 91 HP. At my altitude (6000' pressure, 9000-10000 ft DA in the summer), it delivers about 65 HP, so I get decent performance.

The only negative side is the extra power needs more cooling, so the belly radiator is needed.

Rotax Rick did a great job, his workmanship was perfect, and he really helped me on the install, always returned my calls quickly. 

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Posted

A friend here is getting up graded to th 670 said Rotax Rick recommends running Gasohol rather than 91 Pure gas, are you running gasohol?

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Posted (edited)

A friend here is getting up graded to th 670 said Rotax Rick recommends running Gasohol rather than 91 Pure gas, are you running gasohol?

Yes, I run high octane ethanol mix, and Rotax recommends it over pure gasoline! The internet mythology about gasohol is simply amazing. If you read the Rotax ops manual, the higher octane of gasohol is strongly favored over pure gasoline, knock is an engine killer, and alcohol stays high octane. The normal octane enhances of gasoline wear off in a few weeks, especially if the gas is stored a while.

Note that the lead in high octane gasoline is not at all attractive to Rotax:

fuel - gasohol.jpg

Edited by nlappos
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Posted

We don’t have any ethanol gas at all available.  Is that a bad thing?  Will I have to run avgas?   

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Posted

While it is true that ethanol based fuel is recommended by Rotax over Avgas, don't forget that fuel system compatibility may be a more influencing concern for what fuel to use. There are many cases of folks with older fiberglass fuel tanks reporting that their tanks and/or the tank coatings were not compatible with the ethanol based fuels, leading to fuel system contamination. I have an older Kitfox IV (912 powered) that has the Kreem lined tanks and just sold an older Kitfox IV (582 powered) that also had the Kreem lined tanks.  I am leary of  using any fuel with ethanol for the reasons stated above. On my project airplane I am contemplating cutting the tanks open, removing the Kreem liner, and re-coating with a know ethanol safe liner so that I can use auto gas with ethanol. In my particular case, non-ethanol based auto gas is not readily available to me, so going that route would be very problematic. If I do reline the tanks then I would opt  for auto gas with or without ethanol, but it would probably be ethanol based due to availability. On the 582 powered airplane I ran Avgas with decalin lead scavenging additive. On that airplane the plugs stayed clean and I didn't notice any excessive buildup of deposits when borescoping, but I didn't own/run that airplane very long, so don't have a long track record with the Avgas/Decalin fuel. Just food for thought.

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Posted

Hows that muffler work out with the rubber straps?

when i got my kitfox used they had the muffler mounted solid to the engine mount ! 

they must not have known that the muffler should move with the motor (at least it lasts A lot longer)

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Posted

Hows that muffler work out with the rubber straps?

when i got my kitfox used they had the muffler mounted solid to the engine mount ! 

they must not have known that the muffler should move with the motor (at least it lasts A lot longer)

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Posted

A friend here is getting up graded to th 670 said Rotax Rick recommends running Gasohol rather than 91 Pure gas, are you running gasohol?

Yes, I run high octane ethanol mix, and Rotax recommends it over pure gasoline! The internet mythology about gasohol is simply amazing. If you read the Rotax ops manual, the higher octane of gasohol is strongly favored over pure gasoline, knock is an engine killer, and alcohol stays high octane. The normal octane enhances of gasoline wear off in a few weeks, especially if the gas is stored a while.

Note that the lead in high octane gasoline is not at all attractive to Rotax:

fuel - gasohol.jpg

Never thought I would ever hear anyone recommend Ethanol.

I don't know much bout the octane levels but the garbage we get around here if it sits in a carburetor bowl for more than 6 months it turns to a orange yellow sludge.   91oct premium does not.

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Posted (edited)

Ethanol earned a bad name when first introduced (1990's?) because it dissolved the carb seals and such and made a real mess. Now, all that is far behind but the Internet Gurus haven't learned anything in the 20 years since. 

Rotax PREFERS ethanol over avgas because it is much more anti-knock , Rotax's worst enemy, and the seals and such are all designed to easily handle it. Four week old avgas loses some of its octane, and is more risky for Rotax engines, and they tell you that. Ethanol doesn't lose its anti-knock properties so fast. WWII fighters uses alcohol injection to raise the octane of their engines and gain more power.

Also, ethanol gets its anti-knock without lead, unlike avgas, which leaves lead deposits like crazy.

The reason why I posted the pages from the engine manual is because the internet gurus never read it, and don't believe it even if they did. After all, what does the engine designer know about his engine?

Edited by nlappos

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Posted

nlappos, still flying the 670?  I just picked one up.  installing it in a Kolb.  Ron Davis special.  ...

We're gonna be neighbors!  Im moving over the hill, to Panguitch......  

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Posted

nlappos, still flying the 670?  I just picked one up.  installing it in a Kolb.  Ron Davis special.  ...

We're gonna be neighbors!  Im moving over the hill, to Panguitch......  

Great! I have been down for about 12 months, finishing our house ("You aren't going to the HANGAR while we have so much work to do on the house, right?") and needing to repair a fuel leak. But the engine was running great, and lots of power. My airplane is at Parowan, BTW so we are close!

My experience with Ron was excellent, he was always there to discuss things and send fixes. Good Luck!

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Posted

Nick my 670 has the custom exhaust ( I think by a guy in Colorado?)  What did you do for an exhaust mount? High or low mount?

68A91205-6CF6-475A-B02B-F14FEAB6AE02.jpeg

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Posted (edited)

ChuckM, I used Mike Hair's exhaust (I think he is in Utah) . The Y fitting on the motor I bought on Ebay, I can dig up the part number if you want. I drilled it for EGT, which works well.  The photo shows a 90 deg black elbow in the middle, Mike made me a 135 that I put in later which made the bend much better and centered the fittings at both ends. This photo shows only one white support band on the muffler, a second wasn't yet installed when I shot the photo.

 

 

IMG_0144.jpg

Edited by nlappos

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Posted

Soon, I will join the King Kong family :-) 

I am installing my 670 right now. Need to modify the firewall a little. The mod C engine cowling is getting butched around the E-box... One day I will do some fiberglass work to fix this.

The biggest concern now is to find a way to hang the muffler in a good way.

IMG_20211012_200219.jpg

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Posted

Fixed some clearance in the firewall and managed to hang the muffler.

IMG_20211019_203530.jpg

IMG_20211019_203539.jpg

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