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  #1  
Old 07-30-2019, 07:56 PM
rapid_ascent rapid_ascent is offline
 
Join Date: Mar 2008
Location: Dublin, CA
Posts: 1,060
Default Titan IOX-370 Decision

Last weekend at OSH I spoke to Continental about an IOX-370. I'm leaning toward that engine selection. JB offered a nice show discount as enticement. I want dual PMAGS and they are offering the Superior cold air sump so that is all perfect. My delima is which compression ratio should I pick. There is 8.3 with 187hp quoted or 9.6 which some have said is over 200hp. The cost delta isn't very much at a few hundred dollars. So the high compression option is a pretty good bang for the buck. When I was looking at an IO-360 I had set my compression ratio limit at 9:1, but that configuration isn't offered in the IO-370.

I'd like everyone's comments on any concerns I should have with such a high compression ratio. This does include the counterbalanced crankshaft. I'm feeling like I should be more conservative and go with the 8.3 but on the other hand...
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  #2  
Old 07-30-2019, 08:47 PM
Canadian_JOY Canadian_JOY is offline
 
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 2,072
Default

My personal choice would be to stay at or below 8.5:1 compression ratio. Anything above 8.5:1 mandates use of 100LL. Given that we don't yet have our future fuel situation firmed up, having some flexibility in fuel requirements would seem a prudent influence in selecting compression ratio in a new engine purchase.
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  #3  
Old 07-30-2019, 09:01 PM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,269
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I recently installed a new 370 w/9.6 CR and Bendix mags, and couldn't be happier with the performance (my brother did the same and is also very happy).
I would caution you about using Pmags on a HC engine with their aggressive timing.
Not worried about 100LL going away anytime soon and I won't use mogas anyway.
I have a good friend that opted for the 370/8.3, he can't keep up.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 07-30-2019 at 09:03 PM.
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  #4  
Old 07-30-2019, 10:43 PM
rapid_ascent rapid_ascent is offline
 
Join Date: Mar 2008
Location: Dublin, CA
Posts: 1,060
Default

I’m fine with using 100LL and I’m not worried about it going away either.

I had planned on PMAGs but I get your point Walt. I also got a quote with the CMI mags by mistake so that route would save a little bit of money.

I’m not very knowledgeable in this area so I’ll have to rely on the VAF brain trust for advice.
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Ray Tonks
2018 Donation Paid
Titan IOX-370 on order
RV-7 Fuselage in progress
* Cabin Interior - In progress
RV-7 SB Wings
* Both Wings fully skinned
* Fuel Tanks Complete - No leaks finally
* Ailerons Complete
* Flaps Complete
RV-7 Empennage - Complete (a little fiberglass work left)
Vans Training Kit # 2 - Complete
Shop Setup - In Progress (Gathering Tools, Never Complete)
RV-7 Preview Plans
Vans Training Kit #1 - Complete
EAA Sheet Metal Class - Complete

Last edited by rapid_ascent : 07-30-2019 at 11:10 PM.
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  #5  
Old 07-31-2019, 06:21 AM
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DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
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Quote:
Originally Posted by rapid_ascent View Post
Iím fine with using 100LL and Iím not worried about it going away either.

I had planned on PMAGs but I get your point Walt. I also got a quote with the CMI mags by mistake so that route would save a little bit of money.

Iím not very knowledgeable in this area so Iíll have to rely on the VAF brain trust for advice.
Read this as many times as necessary:

https://www.danhorton.net/Misc/Nigel...Advance%20.pdf
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  #6  
Old 07-31-2019, 06:36 AM
Southern Pete Southern Pete is offline
 
Join Date: Jul 2015
Location: England
Posts: 33
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If you are concerned about too much advanced use P-mags with fixed timing. Or even time them to 2 or 3 degrees after TDC to retard the timing further. Just don't fit magnetos!
Pete
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  #7  
Old 07-31-2019, 07:24 AM
rapid_ascent rapid_ascent is offline
 
Join Date: Mar 2008
Location: Dublin, CA
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Well I think this falls into the category of I donít know what I donít know.

I think the concern would be too much advance. I think that is what Dan is trying to show with the related link.

This is an area where I donít feel comfortable experimenting.
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Ray Tonks
2018 Donation Paid
Titan IOX-370 on order
RV-7 Fuselage in progress
* Cabin Interior - In progress
RV-7 SB Wings
* Both Wings fully skinned
* Fuel Tanks Complete - No leaks finally
* Ailerons Complete
* Flaps Complete
RV-7 Empennage - Complete (a little fiberglass work left)
Vans Training Kit # 2 - Complete
Shop Setup - In Progress (Gathering Tools, Never Complete)
RV-7 Preview Plans
Vans Training Kit #1 - Complete
EAA Sheet Metal Class - Complete
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  #8  
Old 07-31-2019, 08:17 AM
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DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
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Quote:
Originally Posted by rapid_ascent View Post
Well I think this falls into the category of I don’t know what I don’t know.

I think the concern would be too much advance. I think that is what Dan is trying to show with the related link.

This is an area where I don’t feel comfortable experimenting.
I'm not trying to argue for any particular view with the link. Nigel's data is the best available to the public, with excellent balance in presentation of the pros, cons, and alternatives.

Please note that the optimum values Nigel found for each flight condition would apply to a parallel valve engine, not an angle valve. All the incoming data says the angle valve wants far less advance.

Returning to the OP's question, increased CR does diminish detonation margin. High CHT, high oil temperature, combustion chamber oil contamination, high induction air temperature, decreased octane rating, and yes, additional timing advance are also factors reducing the margin. If you select high CR, you simply need to be aware of the other factors.

Ok, so now let's switch from education to opinion.

RV builders tend toward optionitis. The disease extends to engine choices. Your RV will fly great with a perfectly stock engine, and it will probably last longer and be easier to cool.

My own IO-390 is stock.
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Last edited by DanH : 07-31-2019 at 08:22 AM.
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  #9  
Old 07-31-2019, 08:33 AM
C-GRVT C-GRVT is offline
 
Join Date: Feb 2006
Posts: 288
Default What prop?

In choosing an engine it is helpful to keep in mind the prop you are considering, Hartzell for instance has restrictions on some engines, and many it has not tested for harmonics.
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  #10  
Old 07-31-2019, 08:38 AM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,269
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You can purchase the "stock" certified version of the 370/9.6 if you want a "certified" engine.
http://www.continentalmotors.aero/Pr...0_Engines.aspx

As for props, I talked to Les at Hartzell about this, he saw no reason for concern using the current Hartzell BA that Van's sells with no restrictions for the 370 engine with CB crank and mags. I'm pretty sure this is the same prop that has been STC'd with the 370.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 07-31-2019 at 08:43 AM.
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