# Direct drive SBC

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#### MARCVINI

##### Well-Known Member
Here's something to think about, one of those blocks is made by a Chev with a billion dollar research department and 100 years of practice - hell, they invented the shallow block V8 and have made millions of them and all quite successful, personally I'll take the extra 12 lbs for that safety margin over a small company that's made a couple of dozen of them.
Well, believe it or not, the lightest SBC aluminum block is actually a Chevrolet Performance One. Weighing in at 90 lbs, here it is:

As for the small companies in the business, MANY, I say MANY of the major breakthroughs in engine technology, be it in terms of lightness, eficiency, durability, you name it, come from small businesses. Sometimes MASS production leaves no room for those achievements. And you can be sure that GM sees, hears and copies a lot from those companies in order to improve its products.

Aftermarket businesses like Dart, Donovan, BMP, Callies and many others are living proofs that aftermarket can, sometimes, be much better than stock/oficial.

Marcvini

#### MARCVINI

##### Well-Known Member
Whoever is in the auto conversion "endeavour", should take a very goog look at the (few) diesel engine powered aircraft on the market, as far as weight penalties ares concerned.

Here is what I have found:

1. Cessna Skyhawk Avgas X Cessna Skyhawk Diesel standard empty weights: 1.641lbs and 1808 lbs, respectively. Weight diference: 167 lbs.

2. Diamond DA40XLS (avgas) X Diamond DA40NG(diesel) standard empty weights: 1.786lbs and 1940lbs. Weight diference: 154 lbs.

3. The new Glasair Sportsman Diesel (Thielert Centurion engine) will be ofered only with the carbon fiber fuselage, wich leads one to think that the weight penalty will be in the same ballpark as the ones shown before, except for the fact that the CF fuselage weights in at 40 lbs less than the "normal" one and allows a 150 lbs increase in gross weight;

What does it look like? It seems to me that a weight penalty of up 100 is quite manegeable in airplanes in the Lyc 360 powered RVs and Glasair ranges. I am starting to think that I can go for a full CS propeller set up, regardless of the added weight.

Marcvini

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#### tspear

##### Well-Known Member
This article about a two-stroke marine conversion might be of interest, not sure if direct drive or not.
Mercury Outboard Motor for an Aircraft? | EAA

edit: looks like a PSRU mockup in the photo. Article is not clear.
He plans to run at 5000 RPM. So we can assume it has a PSRU. (plus he talks about a reduction gear in the article).

Tim

#### Toobuilder

##### Well-Known Member
Log Member
...What does it look like? It seems to me that a weight penalty of up 100 is quite manegeable in airplanes in the Lyc 360 powered RVs and Glasair ranges. I am starting to think that I can go for a full CS propeller set up, regardless of the added weight...
The term "manageable" requires qualification. I'm sure an RV (or Glasstar) will "fly" with an extra 100 pounds, but you will definitely feel that added bulk.

#### Himat

##### Well-Known Member
Whoever is in the auto conversion "endeavour", should take a very goog look at the (few) diesel engine powered aircraft on the market, as far as weight penalties ares concerned.
...

What does it look like? It seems to me that a weight penalty of up 100 is quite manegeable in airplanes in the Lyc 360 powered RVs and Glasair ranges. I am starting to think that I can go for a full CS propeller set up, regardless of the added weight.

Marcvini
There is a little more to this. Jet fuel/diesel is lighter than petrol and a diesel engine slighly more fuel efficient than a petrol engine.
Depending on the intended distane to travel the take off weight might not differ that much.

#### stol

##### Well-Known Member
There is a little more to this. Jet fuel/diesel is lighter than petrol and a diesel engine slighly more fuel efficient than a petrol engine.
Depending on the intended distane to travel the take off weight might not differ that much.
Nope.... it is about 1 lb heavier per gallon....

Also,, the Diesel discussion is going to be
tempered by the fact the Diesel is close to 100 thousand dollars....... And there is no TBO.. It is TBR = Time Between Replacement... So ya get to cough up another 100 grand...

E

#### ekimneirbo

##### Guest
I have found that those Scat Superlight forged crankshafts for SBCs, SBFs and BBCs can shave up to 10 lbs of the installed engine weight. Factor that in, as well as the fact that an SBC/SBF aftermaket aluminum block weighs in at 12/15 lbs less than a stock LS3 block, and you will came up with a 20/25 lbs weight diference between those engines. That is something to thing about.

Marcvini
You can get a lite weight crank from Callies for the LS3. You also need to consider that the LSx engines will have a lite weight plastic intake manifold vs the heavier aluminum manifold. In the ignition set up, the weight of individual coils will probably offset the weight of distributor and dual coils...........but you gain reliability with a coil for each cylinder. I would expect a gerotor pump to be slightly lighter than a standard SBC pump. Brackets for the alternator are aluminum rather than steel, although you could fabricate aluminum ones. Oil pans are steel vs aluminum although lighter aftermarket pans are available. A carb is heavier than a throttle body but then you have a computer to add to the equation. The biggest factor seems to be the difference in cost for an aluminum SBC block and a LS3 block. Also, used aluminum heads for an LQ9 or LS1 are dirt cheap (as low as $100 for a pair) on Ebay. You are probably staring a$5,000 difference in the face when looking at these two engines. That goes a long way when you are building.The point is that you need to consider the weight with all the components added, as some of the SBC components will be heavier and cancel out the lighter block. Also, I have never liked two piece oil seals. They are much more prone to leakage than one piece seals.

#### Himat

##### Well-Known Member
Nope.... it is about 1 lb heavier per gallon....

Also,, the Diesel discussion is going to be
tempered by the fact the Diesel is close to 100 thousand dollars....... And there is no TBO.. It is TBR = Time Between Replacement... So ya get to cough up another 100 grand...
I stand corrected.
Memmory didn't serve me this time, Diesel/Jet A1 have a higher energy content than petrol by volume, by weight they are prette close to equal. The only difference is then a small one in fuel efficiencey.

And for certified engines that difference do as you state never offset the cost of the engine.

#### nerobro

##### Well-Known Member
Log Member
Nope.... it is about 1 lb heavier per gallon....

Also,, the Diesel discussion is going to be
tempered by the fact the Diesel is close to 100 thousand dollars....... And there is no TBO.. It is TBR = Time Between Replacement... So ya get to cough up another 100 grand...
That heavier weight, is also "more energy." Diesels don't need to have "replace the blocks" But at least the delta hawk has the block as a wear item. IIRC, the rotating assembly is reusable.

#### MARCVINI

##### Well-Known Member
You can get a lite weight crank from Callies for the LS3. You also need to consider that the LSx engines will have a lite weight plastic intake manifold vs the heavier aluminum manifold. In the ignition set up, the weight of individual coils will probably offset the weight of distributor and dual coils...........but you gain reliability with a coil for each cylinder. I would expect a gerotor pump to be slightly lighter than a standard SBC pump. Brackets for the alternator are aluminum rather than steel, although you could fabricate aluminum ones. Oil pans are steel vs aluminum although lighter aftermarket pans are available. A carb is heavier than a throttle body but then you have a computer to add to the equation. The biggest factor seems to be the difference in cost for an aluminum SBC block and a LS3 block. Also, used aluminum heads for an LQ9 or LS1 are dirt cheap (as low as $100 for a pair) on Ebay. You are probably staring a$5,000 difference in the face when looking at these two engines. That goes a long way when you are building.The point is that you need to consider the weight with all the components added, as some of the SBC components will be heavier and cancel out the lighter block. Also, I have never liked two piece oil seals. They are much more prone to leakage than one piece seals.
Actually, a substitute for an LS intake (manifold+fuel rails+throttle body), in an SBC, will wigh in 10lbs more. So, your reasoning on that is absolutelly correct. The real problem is using the LS intake in a DDV8 instalation. The throttle body is placed too far forward from the engine and, either oriented to the front or to the rear of the airplane, you will have dificulties adding filter and other hardware without lengthening too much the instalation. That will be translated into a too far forward propeller weight hanging on the nose of an already heavier instalation. What is the solution for that?

By the way: using used parts is COMPLETELY out of question for me.

Marcvini

#### MARCVINI

##### Well-Known Member
I stand corrected.
Memmory didn't serve me this time, Diesel/Jet A1 have a higher energy content than petrol by volume, by weight they are prette close to equal. The only difference is then a small one in fuel efficiencey.

And for certified engines that difference do as you state never offset the cost of the engine.
Lets not forget that an auto conversion CAN have a substantially higher compression ratio than a Lycoming, so the fuel eficiency will be increased too.

Marcvini

#### Toobuilder

##### Well-Known Member
Log Member
...By the way: using used parts is COMPLETELY out of question for me...
You will find many people who would much rather go with "seasoned" parts like heads and blocks because of the performance/reliability benefits.

#### tspear

##### Well-Known Member
Nope.... it is about 1 lb heavier per gallon....

Also,, the Diesel discussion is going to be
tempered by the fact the Diesel is close to 100 thousand dollars....... And there is no TBO.. It is TBR = Time Between Replacement... So ya get to cough up another 100 grand...

Thielert is TBR.
Diamond AE300 is TBO.
SMA is TBO.

Point is this is manufacturer dependent.

Gas is ~6lbs per US gallon and contains roughly 112K BTUs
Jet-A has huge variations in density around the world which is why it is very important to work in lbs not gallons. But if you really want to know, most people use 7lbs per gallon for Jet-A in the States, but the fuel density can swing enough that it can go from around 6.5lbs per gallon in Asia to 6.8lbs here and contains roughly 124K BTUs.

Tim

#### stol

##### Well-Known Member
Thielert is TBR.
Diamond AE300 is TBO.
SMA is TBO.

Point is this is manufacturer dependent.

Gas is ~6lbs per US gallon and contains roughly 112K BTUs
Jet-A has huge variations in density around the world which is why it is very important to work in lbs not gallons. But if you really want to know, most people use 7lbs per gallon for Jet-A in the States, but the fuel density can swing enough that it can go from around 6.5lbs per gallon in Asia to 6.8lbs here and contains roughly 124K BTUs.

Tim
Thanks for confirming the fact Diesel /Jet A is heavier then gas... Another point you make is scary though.... I WANT consistancy in the fuel I burn in my plane so I can predict it's performace.. If there are parts of the world where poor distilling methods are used or scam artists are thinning out, watering down or using other tricks to reduce the formula .............................then I do NOT want it in my plane..... IMHO..

#### MARCVINI

##### Well-Known Member
Thanks for confirming the fact Diesel /Jet A is heavier then gas... Another point you make is scary though.... I WANT consistancy in the fuel I burn in my plane so I can predict it's performace.. If there are parts of the world where poor distilling methods are used or scam artists are thinning out, watering down or using other tricks to reduce the formula .............................then I do NOT want it in my plane..... IMHO..
It seems to me that even Avgas has huge variations in its quality. Well, all fuels have huge variations. So, the point is, what engine is more tolerant to those variations?

As far as piston engines are concerned, it seems to me that gas powered engines are more tolerant and, therefore, add a nice safety margin on this regard in comparison to diesel ones. Fuel in my country has huge quality variations and gas powered/EFI engines are the ones that have less problems because of that. Actually, they have proven to be very reliable. On the other hand, diesel ones, specially modern ones, always have problems related to fuel quality.

So, I am not really confortable with the modern diese/jet A powered aircraft engines.

Marcvini

#### TFF

##### Well-Known Member
Av gas is the most consistent fuel made. Car gas is made for local requirements for emissions and octane. That is the problem with running car gas in an airplane environment; you dont know what really is in there. Now if some airport owner is doctoring the fuel that is sad; be jail time here in the US.

#### tspear

##### Well-Known Member
Thanks for confirming the fact Diesel /Jet A is heavier then gas... Another point you make is scary though.... I WANT consistancy in the fuel I burn in my plane so I can predict it's performace.. If there are parts of the world where poor distilling methods are used or scam artists are thinning out, watering down or using other tricks to reduce the formula .............................then I do NOT want it in my plane..... IMHO..
Actually Jet-A, Jet A1 and 100LL all meet specifications. The specifications are very tight and consistent around the world.
The problem for many avgas people making the jump to turbines; what matters is energy density of the fuel. For turbines this is in the specification as energy per pound, while in 100LL it is in energy per gallon....

From what I understand/recall; the reason for the variation in the fuel density is the USA we use the smaller lighter hydrocarbon chains which allow for greater density, we have other uses for the heavier / longer hydrocarbon chains. But if you go to Asia, the distillation plant utilizes a heavier crude oil base which has a greater percentage of long / complex chains which actually have a lower physical density and they do not have the business requirements to split off the heavier / long chains.

Tim

Edit. I forgot to note, the difference between Jet-A and Jet-A1 also influences the fuel density but I forget how.

#### tspear

##### Well-Known Member
It seems to me that even Avgas has huge variations in its quality. Well, all fuels have huge variations. So, the point is, what engine is more tolerant to those variations?

As far as piston engines are concerned, it seems to me that gas powered engines are more tolerant and, therefore, add a nice safety margin on this regard in comparison to diesel ones. Fuel in my country has huge quality variations and gas powered/EFI engines are the ones that have less problems because of that. Actually, they have proven to be very reliable. On the other hand, diesel ones, specially modern ones, always have problems related to fuel quality.

So, I am not really confortable with the modern diese/jet A powered aircraft engines.

Marcvini
Marcvini,

Why in the world would you think 100LL has variations around the world? It either meets the international specification or it does not. Same thing with jet fuel. It either meets the specification or it does not.
Compare this to automotive fuel, either gasoline or diesel. The specification is set by each country. That induces huge variations around the world.

Tim