Direct drive SBC

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Badwookie

Member
Joined
Nov 9, 2012
Messages
9
Location
Brisvegas, Australia
Greetings,

This has been an interesting thread to peruse and develop ideas for my (seemingly distant) future kitplane endeavour.

Anyway as a new member, is there much information readily available about turbo compounding an Auto V8?
I ask as I came across the idea on Paul Lamar's site Turbo and I was wondering if it could be used to kill two birds with one stone - firstly upping the hp available at a given RPM, and secondly dependent on it's mounted position if it could help tame some TV and other harmonics?
If you could reliably predict that the turbo and it's connecting gearbox would bear a large amount of these forces then you would have an easily removed, inspectable (is that even a word?:nervous:) and of the shelf replaceable component.

At the moment this is an exercise in thinking out loud and I have no thoughts on implementation or nor knowledge of which actual components would fit the bill.

Cheers.

Tom
 

rv6ejguy

Well-Known Member
Joined
Jun 26, 2012
Messages
3,749
Location
Calgary, Alberta, Canada
Greetings,

This has been an interesting thread to peruse and develop ideas for my (seemingly distant) future kitplane endeavour.

Anyway as a new member, is there much information readily available about turbo compounding an Auto V8?
I ask as I came across the idea on Paul Lamar's site Turbo and I was wondering if it could be used to kill two birds with one stone - firstly upping the hp available at a given RPM, and secondly dependent on it's mounted position if it could help tame some TV and other harmonics?
If you could reliably predict that the turbo and it's connecting gearbox would bear a large amount of these forces then you would have an easily removed, inspectable (is that even a word?:nervous:) and of the shelf replaceable component.

At the moment this is an exercise in thinking out loud and I have no thoughts on implementation or nor knowledge of which actual components would fit the bill.

Cheers.

Tom
Paul Lamar likes to dream about many things but actually builds very little in the flesh and makes his ideas work in real life.

Safe to say that turbo compounding is a very complex thing to make work- far beyond the budgets and capabilities of most folks here. This would be an incredibly complex and expensive way to boost hp at low rpm when we can simply turbocharge the engine which is cheap, reliable and well proven in other DD aircraft applications. Wright, Allison and Scandia spent fortunes making TC work in real life.
 

nerobro

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Log Member
Joined
Nov 6, 2011
Messages
1,111
Location
Northern Illinois
PRT: Power Recovery Turbine ... Actual meaning? "Parts Recovery Turbine." With a PRT, nothing escapes the engine without other damage. :)
 

popeto

Active Member
Joined
Nov 2, 2014
Messages
34
Location
port charlotte fl usa
Hi all,

Been lurking here for a while and have been reading this and other threads about auto conversions. My question is, could you use a large displacement engine, (all aluminum. 632 cubic inch. approx. 800 HP for example) run it at 3000 RPM direct drive (and in my scenario with a drive shaft), and still end up with approx 400 HP? I have been keeping an eye out on the race car sites for used aluminum motors and there are some deals to be made. And yes it would have to have the right parts, not wore out and changed over to F.I. but it could be done. Nothings is cheap for sure. What's the consensus?
Thanks!
 

stol

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Joined
Feb 15, 2008
Messages
497
Location
Jackson Hole Wyoming
Hi all,

Been lurking here for a while and have been reading this and other threads about auto conversions. My question is, could you use a large displacement engine, (all aluminum. 632 cubic inch. approx. 800 HP for example) run it at 3000 RPM direct drive (and in my scenario with a drive shaft), and still end up with approx 400 HP? I have been keeping an eye out on the race car sites for used aluminum motors and there are some deals to be made. And yes it would have to have the right parts, not wore out and changed over to F.I. but it could be done. Nothings is cheap for sure. What's the consensus?
Thanks!
With that many cubic inches, you will have no problem getting 400 hp @3000rpm..
 

Himat

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May 5, 2011
Messages
2,861
Location
Norway
Consensus?
One thing for sure, on auto conversions there are no consensus.:gig:

The question of power is easier. If you can find the torque curve as a function of rpm the power at 3000 rpm can be calculated.
Actually, if you find the power at 3000 rpm for another engine of 630 cid capacity that is the first approximation of what you get.

Edit; STOL posted as I was writing.
 

BBerson

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Dec 16, 2007
Messages
12,764
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Port Townsend WA
It would depend on fuel type and boost. Without boost, most private airplane engines at 2700 rpm, develop 1/2hp per cubic inch.
 

popeto

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Nov 2, 2014
Messages
34
Location
port charlotte fl usa
Thanks guys! Good info to chew on. I was hoping to keep it simple but I think a turbo will be a good thing even though its another point of failure. It will help on both ends. I'm thinking about 5 to 8 lbs boost is all it would need and it would live a little better in the long run.
Thanks
Tom
 

cheapracer

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Toobuilder

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400 HP, 638ci at 3000 RPM = a BMEP of 165. This is right in line with a typical Lycoming. I'd say there would be no need to turbo the engine for such a modest output.

OTOH, 400 HP requires a big prop. It's going to be tough to keep the diameter small enough to keep the tips subsonic at 3000 rpm.
 

MARCVINI

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Apr 16, 2014
Messages
295
Location
Pitanga/Paraná/Brazil
Hi all,

Been lurking here for a while ...
Hi, popeto!!!

What airframe do you have in mind to instal on such an engine?

Marcvini

PS: Altough belonging to a BBC 572, this dyno chart from Smeding Performance can give you a clue of what you can expect from a 638 ci engine:
Smedding 572.jpg
 
Last edited:

popeto

Active Member
Joined
Nov 2, 2014
Messages
34
Location
port charlotte fl usa
Marcvini,
Thanks for the graph. Every little bit of info helps. This combo, if I decide to go that way will be in a one off pusher aircraft.
Thanks
Tom
 

MARCVINI

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Apr 16, 2014
Messages
295
Location
Pitanga/Paraná/Brazil
This is how a DD LSXV8 RV7 would seem like:

Vans RV7 LSX for Homebuiltairplanes.jpg

Notes:
a. simple aluminum 4 inch prop extension;
b. a conventional spider like intake manifold would be use, in order to allow a better streamlined lower cowling;
c. only the lower cowling would have to be changed, in order to accomodate the intake and cylinder heads and covers;
d. radiators would be placed inside the cowling, two of them, one on each side of the engine;

Tailwinds.
 

dsigned

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Joined
Aug 8, 2018
Messages
87
Location
Illinois as of 08/12/2018
Hi all,

Been lurking here for a while and have been reading this and other threads about auto conversions. My question is, could you use a large displacement engine, (all aluminum. 632 cubic inch. approx. 800 HP for example) run it at 3000 RPM direct drive (and in my scenario with a drive shaft), and still end up with approx 400 HP? I have been keeping an eye out on the race car sites for used aluminum motors and there are some deals to be made. And yes it would have to have the right parts, not wore out and changed over to F.I. but it could be done. Nothings is cheap for sure. What's the consensus?
Thanks!
Yes, but this is almost certainly unnecessary. Automotive engines run cams that are designed to make peak power at their rated RPM, and make it gradually for a nice linear powerband. A racing cam can be used, with much higher and longer lift profiles, but tends to make the engine FAR thirstier (obviously), and makes it much harder to tune the engine for a wide powerband. Some automakers partially got around this by having (in effect) two cam profiles: a "small" one for low RPM and a "big" one for high RPM. So you're not sucking gas if you stay out of the powerband, and the car runs fine. But when the VTEC kicks in (yo), the engine is using a lot more fuel. With modern EFI, swapping a cam and setting up the timing to produce a lot of power low in the powerband (e.g. below 5000 rpm) isn't "hard" (it is hard, just because doing fuel mapping is apparently a pain), it's just not a terribly common request. But AFAIK, this is exactly what EPI does.
 

Doggzilla

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Joined
Jun 2, 2013
Messages
2,181
Location
Everywhere USA
This is how a DD LSXV8 RV7 would seem like:

View attachment 43921

Notes:
a. simple aluminum 4 inch prop extension;
b. a conventional spider like intake manifold would be use, in order to allow a better streamlined lower cowling;
c. only the lower cowling would have to be changed, in order to accomodate the intake and cylinder heads and covers;
d. radiators would be placed inside the cowling, two of them, one on each side of the engine;

Tailwinds.
Its also possible to put the radiator behind the engine to avoid making modifications to the power train, as they can cause vibration and bearing issues by changing the torque on the bearings.

Also dont forget that radiators can be fit in sideways and fed from a duct sticking out the side and feeding the rad at a 90 degree angle like the cold air intakes for superchargers on muscle cars. They dont have to be inline with one another.

In fact, it could even be attached horizontally to the belly of the crank case in that manner, fed with a chin intake like a Typhoon.
 

Erik Snyman

Well-Known Member
Joined
Oct 9, 2019
Messages
46
Hello All
Early morning idea:
We have a problem with a DD V8 sitting upright in the cowl, as the prop thrust-line is too low. Right?
How about this: NOTE-this is just an idea. No details have been worked out yet
1. Remove intake.
2. Mount a shaft in the valley, supported by pillow blocks on the ends, parallel to the crank shaft.
3. Another bearing in the center of the shaft to counter the shaft bending.
4. Decide which end of the engine you want to face the air stream.
5. Fit a prop hub to one end of the shaft, a belt pulley to the other.
6. Fit same size pulley (1:1 ratio) to the corresponding end of the engine. If you want reduction, vary the size of this pulley for the desired ratio.
7. Get creative with the intake.
8. Result: You can run either side of the engine to the front.
You can have a reduction ratio if you so wish.
The prop thrust line is now above the crank line, so there is more prop-to-ground clearance, and improved looks.
You can have the drive belt on either side: rear or front.
The engine is right-side-up, no oiling and cooling mods needed.
9. As I said, just an idea. No details worked out yet.

Erik in Oz.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
7,368
Location
North Carolina
Hello All
Early morning idea:
We have a problem with a DD V8 sitting upright in the cowl, as the prop thrust-line is too low. Right?
How about this: NOTE-this is just an idea. No details have been worked out yet
1. Remove intake.
2. Mount a shaft in the valley, supported by pillow blocks on the ends, parallel to the crank shaft.
3. Another bearing in the center of the shaft to counter the shaft bending.
4. Decide which end of the engine you want to face the air stream.
5. Fit a prop hub to one end of the shaft, a belt pulley to the other.
6. Fit same size pulley (1:1 ratio) to the corresponding end of the engine. If you want reduction, vary the size of this pulley for the desired ratio.
7. Get creative with the intake.
8. Result: You can run either side of the engine to the front.
You can have a reduction ratio if you so wish.
The prop thrust line is now above the crank line, so there is more prop-to-ground clearance, and improved looks.
You can have the drive belt on either side: rear or front.
The engine is right-side-up, no oiling and cooling mods needed.
9. As I said, just an idea. No details worked out yet.

Erik in Oz.
That will have all the difficulties of a redrive and lack it's primary benefit: lower revs.
But it's basically what I'm doing with a Briggs V twin, with reduction. It suits my application and engine. It may not work as well for a V8.
 
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