rpmagazine
|
| posted on 16/12/07 at 12:21 AM |
|
|
it is a reasonable work through but fit to purpose becomes an issue. If you want to seriously use the vehicle on a track one of the first issues is
wheel/tyre availability. 15" wheels immediately limits your choice of brands and compounds in my market (note US/UK may be different).
You are also assuming no modification to components. With more modification the advantages are lessened or changed...but the Subie is limited in this
respect.
Having said that I think they are a very good thing, it's just that the picture is always more convoluted that we realise.
|
|
|
|
|
kb58
|
| posted on 16/12/07 at 06:42 PM |
|
|
quote:
This is exactly the same overall height as a flat four BUT the straight four has big cast bits such as the block and the head above the crank
so the CoG is higher.
But then there's the accessaries. There's nowhere for the heavy alternator, starter, intake, and maybe turbo to go, except up above the
engine. I agree that the CG will still lower than a I-4, but I suspect the advantage is less than expected; the CG certainly isn't at crank
centerline. The flat-4's advantage is even smaller when compared to an I4 with an aluminum block and head.
[Edited on 12/16/07 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
|
|
|
gator
|
| posted on 17/12/07 at 12:35 AM |
|
|
Message for Del
A mesage for Del, I have accidentally deleted your Email address when clearing spam (Oh Bugger).
The dimensions you were after: O/all length 760mm; distance from leading edge of bellhousing to centerline of driveshaft approx 165mm. Hope this
helps, sorry for the stuffup.
Regards, Alan.
|
|
|
cymtriks
|
| posted on 17/12/07 at 11:20 AM |
|
|
quote:
Originally posted by rpmagazine
it is a reasonable work through but fit to purpose becomes an issue. If you want to seriously use the vehicle on a track one of the first issues is
wheel/tyre availability. 15" wheels immediately limits your choice of brands and compounds in my market (note US/UK may be different).
You are also assuming no modification to components. With more modification the advantages are lessened or changed...but the Subie is limited in this
respect.
Having said that I think they are a very good thing, it's just that the picture is always more convoluted that we realise.
Assuming you you mean the traditional racing size of 13 inch wheel then the numbers won't change much.
For racing the rolling radius will be slightly less (but not much as side walls of the tyres tend to be taller) but the ground clearance will also be
less as it's a race car.
The result will be that my numbers are still about right, only with a small change in drive shaft angle and overall height due to everything being a
bit lower.
|
|
|
Delinquent
|
| posted on 17/12/07 at 11:35 AM |
|
|
quote:
Originally posted by gator
A mesage for Del, I have accidentally deleted your Email address when clearing spam (Oh Bugger).
The dimensions you were after: O/all length 760mm; distance from leading edge of bellhousing to centerline of driveshaft approx 165mm. Hope this
helps, sorry for the stuffup.
Regards, Alan.
Many thanks Alan  - when you say overall length, does that include the gearchange link (which I believe still pokes out the back of the 2WD
box?)
Would be rather handy if it did, as it is a perfect fit within the bodyshell design at that size - would only require me to move the fwd mounts for
the wishbones back - which is a point to note for anyone else considering this unit, the distance from the driveshaft centres to the back edge of the
engine mean you're either going to have very short wishbones or the leading leg of the wishbone is going to be nearly perpendicular to the
centreline.
|
|
|
cymtriks
|
| posted on 17/12/07 at 11:36 AM |
|
|
quote:
Originally posted by kb58
quote:
This is exactly the same overall height as a flat four BUT the straight four has big cast bits such as the block and the head above the crank
so the CoG is higher.
But then there's the accessaries. There's nowhere for the heavy alternator, starter, intake, and maybe turbo to go, except up above the
engine. I agree that the CG will still lower than a I-4, but I suspect the advantage is less than expected; the CG certainly isn't at crank
centerline. The flat-4's advantage is even smaller when compared to an I4 with an aluminum block and head.
For a flat engine I'd expect the intake to be balanced by the exhaust hedders and sump casing which leaves only the starter and alternator.
I have no idea where the starter is on a flat engine, I'm just guessing that it'll have to be on top like the alternator is!
I'd guess that the CoG is about 2 iches above the crank.
For a straight four the cylinders, head, intake and exhaust are all above the crank. The cylinders by about 4 inches, the head, exhaust and intake by
about 11. The crank is probably the heaviest bit of the asembly by a long way.
The starter and alternator are often above the crank as well but even if they're not I can't see the CoG being less than half way up the
block.
So the advantage of a flat engine is all of 2 inches in CoG!
There is still the advantage of overall height without having to mod the gearbox but, as rpmmagazine points out, there's nothing outside
fiddling with the turbo boost in the way of tuning for Subaru engines and personally I'd steer clear of that in a fibreglass car (turbo heat and
fibreglass can be bad neighbours). On the other hand there's a huge ammount of normal aspiration tuning stuff for Duratec straight fours.
|
|
|
kb58
|
| posted on 17/12/07 at 02:33 PM |
|
|
quote:
Originally posted by cymtriks I'd guess that the CoG is about 2 iches above the crank.
I would have thought that the in-lin CG would be lower, due to the heavy steel crank moving the CG to below half way up the block. I forgot about the
CG effect of the intake assembly... I'm assuming an aluminum block and head, too. If both are steel, it's a lost argument for the
inline.
While I'm not up on modified Subaru engines, I agree that aftermarket "go-fast" parts are much more widely available for inline
engines. Just look in any car magazine and it's hard to find ads for Subie drivetrain parts.
All this stuff aside, the homebuilt car that a Subie will fit must have a really wide engine bay, and accomodate the long transaxle tail shaft. It
would be a very different Locost, and not so low cost either. I recently saw a complete drivetrain from an STi... $10,000. That's crazy. Oh
sure, there are Subi engines much cheaper, but they're the old ones that don't make much power.
[Edited on 12/17/07 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
|
|
|
cymtriks
|
| posted on 17/12/07 at 05:27 PM |
|
|
CoG heights assuming the lowest mounting for each type-
Flat
4 inches for ground clearance, 6 for the exhaust and 4 for half the cylinder head gives a crank centre at 14 inches. The weight of the intake above
the crank is balanced by the weight of the exhaust and sump below it (though the sump will need cutting as it looks deeper than the exhaust as
standard). That leaves the effect of the remaining ancilliaries which raise the CoG to, as a guesstimate, 15 to 16 inches. The overall height is about
28 inches.
Straight
4 inches for ground clearance, 7.5 for the bell housing (the lowest point on the assembly, not the sump) gives a crank centre at 11.5 inches. The sump
is just a hollow box and the cylinders, head, intake and exhaust are all higher. While the crank is still the most massive bit the combined weight of
the intake, head and exhaust can't be far off and it is about 12 inches above the crank. So a guesstimate of the CoG would be about 15 to 16
inches. The overall height is about 28 inches.
So assuming you are not restricted by anything other than the engine there's no gain either way. The CoG is in about the same place and the
overall height is about the same.
BUT
In order to mount a flat engine at the height given above you can use the transaxle as it came and run low drive shaft angles. To do this with the
straight engine requires that you invert the box (cost and time to modify) and run higher driveshaft angles (possible long term reliability
issues).
Question-
Can the cheaper (not porsche G50 or Hewland!) boxes be inverted at reasonable cost?
Audi?
Renault?
Subaru?
For the home builder this might be the deciding factor.
|
|
|
kb58
|
| posted on 17/12/07 at 08:36 PM |
|
|
I recently discovered that Volvo has an in-line transaxle, too.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
|
|
|
Ringius
|
| posted on 17/12/07 at 10:54 PM |
|
|
Hi Kimini!
Do you mind telling what volvo has the in-line transaxle? Since I live in Sweden, this might be an attractive alternative to the Audi box for me
(availability of wrecked Volvos is pretty big here).
BR,
Ringius
|
|
|
gator
|
| posted on 18/12/07 at 12:14 AM |
|
|
quote:
Originally posted by Delinquent
quote:
Originally posted by gator
A mesage for Del, I have accidentally deleted your Email address when clearing spam (Oh Bugger).
The dimensions you were after: O/all length 760mm; distance from leading edge of bellhousing to centerline of driveshaft approx 165mm. Hope this
helps, sorry for the stuffup.
Regards, Alan.
Many thanks Alan - when you say overall length, does that include the gearchange link (which I believe still pokes out the back of the 2WD
box?)
Would be rather handy if it did, as it is a perfect fit within the bodyshell design at that size - would only require me to move the fwd mounts for
the wishbones back - which is a point to note for anyone else considering this unit, the distance from the driveshaft centres to the back edge of the
engine mean you're either going to have very short wishbones or the leading leg of the wishbone is going to be nearly perpendicular to the
centreline.
Hi, the 760mm includes the basic gearshift mechanism as shown, it's the most rearward part. I haven't given any thought to the arrangement
of linkage(s) forward to the cockpit as yet.
Regards, Alan.
 
Rescued attachment 100_1610.jpg
|
|
|
rpmagazine
|
| posted on 18/12/07 at 09:19 AM |
|
|
quote:
Originally posted by cymtriks
CoG heights assuming the lowest mounting for each type-
Flat
4 inches for ground clearance, 6 for the exhaust and 4 for half the cylinder head gives a crank centre at 14 inches. The weight of the intake above
the crank is balanced by the weight of the exhaust and sump below it (though the sump will need cutting as it looks deeper than the exhaust as
standard). That leaves the effect of the remaining ancilliaries which raise the CoG to, as a guesstimate, 15 to 16 inches. The overall height is about
28 inches.
Straight
4 inches for ground clearance, 7.5 for the bell housing (the lowest point on the assembly, not the sump) gives a crank centre at 11.5 inches. The sump
is just a hollow box and the cylinders, head, intake and exhaust are all higher. While the crank is still the most massive bit the combined weight of
the intake, head and exhaust can't be far off and it is about 12 inches above the crank. So a guesstimate of the CoG would be about 15 to 16
inches. The overall height is about 28 inches.
So assuming you are not restricted by anything other than the engine there's no gain either way. The CoG is in about the same place and the
overall height is about the same.
BUT
In order to mount a flat engine at the height given above you can use the transaxle as it came and run low drive shaft angles. To do this with the
straight engine requires that you invert the box (cost and time to modify) and run higher driveshaft angles (possible long term reliability
issues).
Question-
Can the cheaper (not porsche G50 or Hewland!) boxes be inverted at reasonable cost?
Audi?
Renault?
Subaru?
For the home builder this might be the deciding factor.
When we are engineering from given components we are in some respects reverse engineering. Our priorities for intended purpose and ability to produce
our final item will make many decisions for us.
For me the wheel diameter was set by the convergence of two facts: in my part of the world there is more competition tyre choice in 17" in the
desired sizes and going larger resulted in a heavier wheel/tyre combination (and more weight further from the centre increasing gyscopic effects,
power loss and cost as tyres were much more expensive, plus there was a loss of desirable compliance in tyre sidewall, but I digress.)
So wheel diameter is set by what is important to you. This then sets the outer driveshaft height. This influences the inner driveshaft height as you
cannot have more than a given static deflection dependent on driveshaft joint type. The often quoted 7deg is a misnomer for normal ride height as you
need a couple of degree of leeway so 5deg is safer, remembering that the angle will increase/decrease dependent on level of suspension travel.
So wheel center actually 'sets' inner drive shaft flange height. The ability to lower mass below this point then becomes the issue. With
an inline engine this is difficult as the input shaft is fixed and competition transaxles are expensive. Flipping the transaxle will work, but not all
are suitable. However there is another element: box ratios and suitability for purpose and cost of replacement...a Pfitzner gear cluster for a Subie
box will cost $4000AUD plus build. So this may influence choice.
But getting back to CoG even if you flip the box, that is about all you can do.
Transvarse box has all the same driveshaft issues, however you can cut and rotate the box on the bell housing and thus lower the engine relative to
the driveshaft or you can rotate the whole assembly assuming the oil drainage in the engine and lubrication in the box will allow it. You can maximise
this effect by reducing the FW diameter and cutting the bell housing down to suit and then rotating the box/bell housing some more...you cannot do
this with the inline if the driveshafts angles do not allow it.
Now having said all of that the inline allows a greater level of lowering in most instance due to the fact that the driveshafts are longer
Let me finally add that I think the Subie gear is very good.
[Edited on 18/12/07 by rpmagazine]
|
|
|
Delinquent
|
| posted on 18/12/07 at 11:51 AM |
|
|
quote:
Originally posted by gator
Hi, the 760mm includes the basic gearshift mechanism as shown, it's the most rearward part. I haven't given any thought to the
arrangement of linkage(s) forward to the cockpit as yet.
Regards, Alan.
lovely job - that would fit nicely, cheers
|
|
|
Benonymous
|
| posted on 19/12/07 at 04:33 AM |
|
|
I'm a bit slow..
Am I missing something here? If one was to use a Subaru engine/gearbox, in a mid rear engined car, then the gearbox is already twirling the wheels
in the right direction. No need for flipping gearboxes because the Subaru motor is already ahead of the gearbox in the engine compartment. The
reason for flipping Porsche gearboxes is to get the mid rear engine to spin the wheels in the right direction due to the fact that the venerable 911
is rear engined. Also, using a 2WD box would definitely be the best solution as it would lack the components for 4WD output. have you ever
noticed how similar Subaru parts are to VW beetle pats ? 
|
|
|
gator
|
| posted on 19/12/07 at 05:03 AM |
|
|
I'm with you! I know someone who has the setup in a Porsche spyder replica. Seems OK to me despite the concerns most express on gearbox
weaknesses.
Regards, Alan
|
|
|
Delinquent
|
| posted on 19/12/07 at 12:16 PM |
|
|
quote:
Originally posted by Benonymous
Am I missing something here? If one was to use a Subaru engine/gearbox, in a mid rear engined car, then the gearbox is already twirling the wheels
in the right direction. No need for flipping gearboxes because the Subaru motor is already ahead of the gearbox in the engine compartment. The
reason for flipping Porsche gearboxes is to get the mid rear engine to spin the wheels in the right direction due to the fact that the venerable 911
is rear engined. Also, using a 2WD box would definitely be the best solution as it would lack the components for 4WD output. have you ever
noticed how similar Subaru parts are to VW beetle pats ?
People flip the box to try and get the engine seated as low as possible in the car (driveshafts sit below centreline in "normal" position)
- as you say with a Scoobie unit this poses a problem as you'd then be spinning the wheels backwards, so would need additional work on the diff
to correct it.
The VW box IMO is no good for this type of app - I used to be heavily into modded VW's and you could pretty much guarantee an upgrade in the
engine would result in ripped up boxes. Even the Hewland Mk9 (based on VW shell) is only rated to 180 lb ft
|
|
|
kb58
|
| posted on 19/12/07 at 02:23 PM |
|
|
Volvo has some FWD transaxles, oriented for north/south engines.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
|
|
|
rpmagazine
|
| posted on 24/12/07 at 01:47 AM |
|
|
http://www.blastautomotive.com/photos.html
|
|
|
THAWA
|
| posted on 30/12/07 at 07:03 PM |
|
|
quote:
Originally posted by kb58
quote:
Originally posted by cymtriks I'd guess that the CoG is about 2 iches above the crank.
I would have thought that the in-lin CG would be lower, due to the heavy steel crank moving the CG to below half way up the block. I forgot about the
CG effect of the intake assembly... I'm assuming an aluminum block and head, too. If both are steel, it's a lost argument for the
inline.
While I'm not up on modified Subaru engines, I agree that aftermarket "go-fast" parts are much more widely available for inline
engines. Just look in any car magazine and it's hard to find ads for Subie drivetrain parts.
All this stuff aside, the homebuilt car that a Subie will fit must have a really wide engine bay, and accomodate the long transaxle tail shaft. It
would be a very different Locost, and not so low cost either. I recently saw a complete drivetrain from an STi... $10,000. That's crazy. Oh
sure, there are Subi engines much cheaper, but they're the old ones that don't make much power.
[Edited on 12/17/07 by kb58]
10 grand for a US STi swap is ridiculous. Especially when you can get a v8 swap for like 8.
You're right there isn't a "tuning catalog" like there are for hondas, ford, nissan , and whatever. Which I think is good.
Helps keep the silly poo to a minimum.
You can easily make tons of power from any subaru engine, all you need is a good turbo, injectors, and engine management. Sure in stock form the
EJ257 is killer, but the same amount of power can be made with an EJ22T, EJ20G, EJ205, or EJ20K. Actually the EJ20G and EJ20K pretty much the same
power, 280ps vs 300 hp, and cost significantly less.
Depending on the dyno a stock STi will put down 230-250 WHP, and 230-250 FT/LBS. There are multiple people dynoing EJ22T's at 200-250 WHP, and
230-300 FT/LBS, with nothing more than a larger turbo, bigger injectors, an intercooler, and sometimes management. The EJ22T stock is 160hp, 181
ft/lbs at the flywheel. People with EJ20G's are putting down good numbers with less changes to the engine, simply because it's made to do
so.
Of course if you take an STi engine, and give it the same treatment, you will make more power, but it's not like it's unattainable with an
older engine.
Oh BTW,
EJ22T = 91-94 US Legacy Turbo
EJ20G = 89-92 non-US Legacy/Liberty Turbo, and 92-97 Impreza WRX and STi
EJ20K = 96-97 Impreza WRX and STi sedan only
EJ205 = 99-present non-us Impreza WRX, and 02-05 US Impreza WRX
EJ257 = 04-present US Impreza WRX STi
The EJ22T is a sad engine in stock form. It has the smallest turbo since the Loyale, no intercooler, tiny SOHC heads, and an old 8-bit ECM.
|
|
|
Gakes
|
| posted on 13/1/08 at 06:59 PM |
|
|
I know this is an old thread but, the advantages of having the flat 4 suby is that almost all mechanical forces are balanced, including gearbox, and
shafts. most i4's have a long and short driveshaft that creates torque steer in front wheel drives and tail happy middy's
 
Description
|
|
|
TheGecko
|
| posted on 13/1/08 at 11:47 PM |
|
|
quote:
Originally posted by Gakes
I know this is an old thread but, the advantages of having the flat 4 suby is that almost all mechanical forces are balanced, including gearbox, and
shafts. most i4's have a long and short driveshaft that creates torque steer in front wheel drives and tail happy middy's
Not strictly true nowadays. Most modern transverse drivetrains with any significant sort of power output have a fixed shaft with the inner CV on the
end of it so that the moving driveshafts are equal length.
I have two different drivetrains at home (long story ) and both of them are configured that way. And they're a lot more compact in plan than
a boxer layout.
Dominic
|
|
|
kb58
|
| posted on 14/1/08 at 02:19 PM |
|
|
Can someone please tell me the approximate size of the drivetrain:
1. How far forward of axle centerline is the front pulley of the engine?
2. How tall is the engine above the crankshaft, including all accessaries?
3. How wide is the engine, side-to-side, including any manifolds.
4. How far behind axle centerline does the transmission tail shaft extend?
Thanks!
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
|
|
|
RazMan
|
| posted on 14/1/08 at 04:16 PM |
|
|
I can't take credit for these so apologies to the person who originally uploaded them
 
Rescued attachment imprezaenginesize.jpg
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
RazMan
|
| posted on 14/1/08 at 04:17 PM |
|
|
Any help?
 
Rescued attachment imprezaenginedimensions.jpg
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
kb58
|
| posted on 14/1/08 at 06:24 PM |
|
|
Very cool, thank you both!
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
|
|
|
