What's new

Subaru Engine rear subframe thoughts

ydeardorff

New member
Please pipe in here with your ideas.
Id like to compare ideas for the subaru engines ranging from the relaible EJ22 through the SVX.

Im looking at both the SVX engine setup, as well as the EJ22.
My thoughts on this are to essentially make a 4 point roll bar that will be welded to the bug chassis in a way that the body will still fit down over it if it needs to be removed.
This will have mounts built at four locations that can be unbolted to remove the entire rear sub-frame, and drive train as one piece.
I am also looking into the idea: Using the following hard points already found on a standard bug pan.
1.)The trans mount
2.)Rear shock tower mount points.

Now add this type of front mount found here: Vanaru - Subaru Vanagon Conversions - Turn-Key subaru engine conversions for Vanagon!

I think the engine should be solidly mounted

Heres a quick sketch of what Im talking about.
STERLING REAR SUBFRAME IDEA.JPG

This isnt totally accurate, as I missed out on the trans mount points. But I think its gets the point across. Blue are weld points, red are bolted mount points, and purple are where the sub-frame attaches to the roll bar/ sub frame support.

The Subarus have two mounts at the rear of the motor by the bell housing for the trans. So especially with the mid mounted setup like Im looking into, I think the front mount may be a good idea, even if abit of overkill.
Im wondering though, what diameter of tubing and what wall thickness I should use, for both the 4 cylinder, and the 6 cylinder as well.
Let me know what you think.*thumbs up*
 
Last edited:

letterman7

Honorary Admin
Essentially what you're building is a Kafer bar system. With the four cylinder, I don't think you'll need any reinforcement at all, or minimal at best, as the engine weights are very close - something like 40 pounds of difference. I can't say about the flat six, though finding it's weight on a website somewhere should be easy. If you're going to triangulate into the frame rails, you'll need to cross-brass widthwise point to point as the frame rails themselves are rather thin. A better solution, though more a pain in the ass, is to cut the bottom of the frame rails out and slip in a 2x3 heavy wall steel tube, weld that full length to the rails, then cross-brace. The more you can brace to the tunnel itself, the better off you're gonna be - just don't weld anything to the bottom of the tunnel... it's only 18ga steel.
 

Brett Proctor

Well-known member
Are you keeping the IRS suspension?? or fabricating your own rear end??
If your keeping the existing suspension do you plan to cut the trany support horns off after the IRS brackets??
Just trying to get a visual of what your trying to do before I comment on it.

Later
Brett
 

ydeardorff

New member
I am hoping to retain as much of the original vw chassis as possible.
Im attempting to come up with a rear modular sub frame that will support the engine, transmission, and keep everything rigidly in its proper place, all the while unifying the rear suspension into the chassis as well, making it less flexible.
I am planning on adding the 944 rear suspension, eventually.

The idea is to keep the engine easy to get at. Properly supported while keeping a route for everything like fuel lines, exhaust, collant lines, etc. But also making the entire unit a modular piece that can be fairly simply disconnected and removed from the chassis as one piece, should I need to.
I figured adding in a roll bar with forward canted arms would help spread the load more forward.

This will be a mid engine format, my hope is to shoe horn everything in place, and still have a decent useable amount of gaps around the engine/trans. Side to side isnt a worry, but the length is. 3 inches of spare room for the SVX setup is cutting it VERY thin. I also have to keep the motor off of the torsion bar pivot, and above the travel of the trailing arms too.

But my intention is to have everything fit UNDER the skin. I dont want to chop up my sterling.


Does that help at all?*hmmm*
 

letterman7

Honorary Admin
Something to keep in mind, Yaughn - the same issue I'm running into: where are you going to put a fuel tank?
 

ydeardorff

New member
Actually, I had started drawing up sketches on something simlar to that of what lauren is running. I just dont know how much volume it would be able to hold.

I can relocate the battery, thats no biggy, the rad and condensor will go up in the nose, with the tank behind it.

Yes each item in my car has to be planned out very carefully, and each item will in turn reflect how the next is installed. Its not a light job re-engineering a car. *proud*

But nothing Im not willing to work at, one project at a time.;)
 

Brett Proctor

Well-known member
Found this in the Modification manual Page 92. I would modify the intake to take in more air but its another option to think about plus the water has less distance to circulate threw. Plus if you did something like this it would give you more room in the front for a gas tank. If you put the radiator in the front were you going to use an auxilary water pump to get enough water to circulate through the system? That's a long distance for a stock water pump to pump. What material were you going to use for tubing. I've been told aluminum tubing is the only way to go.
I've given it some thought on your frame work for mounting the motor and I'll get back to you when I have more time to discus it.

Later
Brett

*very frustrated*Can't get the picture to come through.

Here is the link to the manual if you don't have it http://www.euro-nova.co.uk/Euro Nova Scans/Modifications_manual.pdf
 

letterman7

Honorary Admin
Plumbing is always a second guess for going watercooled. I've seen guys use everything from aluminum to copper to EMT conduit (not recommended). I'm using 3/4" copper right down the middle... the car has no road time yet, so we'll see how it holds up. But based on some of the UK folks who have many thousands of miles on their copper based systems, I don't think there will be an issue.
 

ydeardorff

New member
Found this in the Modification manual Page 92. I would modify the intake to take in more air but its another option to think about plus the water has less distance to circulate threw. Plus if you did something like this it would give you more room in the front for a gas tank. If you put the radiator in the front were you going to use an auxilary water pump to get enough water to circulate through the system? That's a long distance for a stock water pump to pump. What material were you going to use for tubing. I've been told aluminum tubing is the only way to go.
I've given it some thought on your frame work for mounting the motor and I'll get back to you when I have more time to discus it.

Later
Brett

*very frustrated*Can't get the picture to come through.

Here is the link to the manual if you don't have it http://www.euro-nova.co.uk/Euro Nova Scans/Modifications_manual.pdf


Thanks, If I tried that I would go the lamborghini method of twin radiators, with pulling fans exiting out the rear on each side, force fed air from the hip vents.
Its a simple output to a T split into the two small rads, then they join back up at the bottom via another T, then back into the motor.
Lamborghini-Reventon-Wallpaper-1024.jpglamborghini-reventon-2.jpg
-Which I actually thought would be less effective, than running the system in series like on pg 92 in the manual you provided. But if lamborghini has been using that setup for decades, im sure it must work just fine. And it also leads to a single high point right at the top of motor.
Then just have to modify the rear inside of the car to route the gathered air from the scoops, and direct it into the rads.
I dont think though that the stock openings would provide enough airflow even at speed, without the fans running constantly. They might have to be enlarged abit. I think the hip vents would probably have to be widened at least to twice as wide with raised scoops added. Like from Daves RX package just wider.

A couple of Geo Metro Radiators should work well in that application.

But in doing that would allow for a huge gas tank up front, or even possibly a baby spare tire.
 
Last edited:

Brett Proctor

Well-known member
I figured out another way to mount the subaru motor and tranny and still allow you to install and remove the body with no problems. From reading your posts I figure you know how to weld and fiberglass so it should be no problem to build. Just give some time to get it on paper. Its not to difficult. I don't have any CAD programs so it wont be pretty but it should work.

Later
Brett
 

Brett Proctor

Well-known member
OK lets see if I can post this one with out deleteing it(my fault)and I know it looks like crap. I'm not a CAD engineer.This is my first time using this program that I found in the computer.

The intent is to build a taller tunnel section(in yellow)(you will have to determine how tall) and using that for the base for the support structure(in red) for the motor(again you would have to figure out where all of the bends would go). The section of the car where the tunnel is will have to be cut out to accept the taller tunnel and a new flange will have to be fibergassed into the bodys shell.
You can add any addional supports. Maybe one going to the two transmission horns that would be cut off.
Anyway you get the idea. The new tunnel section would be welded(of course, and should not create any space problems.) and the support structure can be welded or a bolt on design and the motor could be removed by unbolting it and droping it down from the structure. With this configuration the body can easily be removed with out any problems.
Your basically taking the existing structure and raising it to go over the motor or along the side of the motor.
For the tunnel section I would mic the thickness of the existing steel(probably metric) and use that to go by for starters and for the support structure I would use at least 0.095" thick square or round tubing.

The support structure would go inside the new tunnel section to the front of it and welded to the old tunnel section for strength. And of course that whole area gets welded all so till it comes out the back and then you can use a bolt on system if you like.
 

Attachments

  • 000_0122.jpg
    000_0122.jpg
    174.7 KB · Views: 2,617
Last edited:

ydeardorff

New member
OK, Nic,

I got the measurements here for ya.

Overall:
19H x 15W x 6D

Radiator itself, without the fan and coolant tanks: 15W x 14H x 1/2D



Dimensionally it seems doable, the only problem I really see, it the thickness of the rad is so thin. That's not going to help the cooling efficiency much, as far as cooling capacity goes.

If the rule is 1 x 1 x 1 per horsepower, Then this guy is worth just over 100hp max. The geo metro is rated at 55 hp, so thats almost a 40% cooling capacity reserve for the car if that rule is accurate.

I would think a couple of R1 rads might be a better option.
 
Last edited:

ydeardorff

New member
You know Ive been thinking about the engine mounting for the EJ22, or the EG 3.3. And Ill have to talk to someone whom knows more about mounting engines, and making sand rails etc. to get a good gouge on whether this will work. But, I had though about using that front mount in the link I posted, tie that into the shock towers, and use the trans horn mounts for the main motor mounts.
I could make a smaller sub-frame off of those two connection points, to hold the trans.

I'm hoping that since the motor would be strattling the trans horns, rather than hanging off the back of them, And it will tied in with the shock mounts, in all it should be a strong enough setup to hold the whole setup without drooping. Without having to go the fancy overkill route, I was talking about.

I'm hoping to have the toys soon to start physically checking into some of this stuff.*rock on*

One of the bigger concerns actually is clearance for the exhaust, given the trailing arms and all are right there in the same general space.
 
Last edited:

Brett Proctor

Well-known member
I was at a junk yard yesterday looking at the two motors. If you plan to mount the 6 over the tranny horns the angle of the axles might be to steep and cause the CV's to fail premature.

Thats why I was thinking you would have to cut them off to get the transmission in a better position to line up with the stub axles and get the motor as low as possible.

Another thought all so. Going with a six the extra weight in the rear is going to move the CG back even farther making the front lighter, causing it to push more in the corners. Have you given this any thought or how you were going to resolve this? You know what a tail heavy plane is like to fly.

The power to weight ratios look good but there's other things I'm looking at before I go with the 6 and I was wondering if you had looked into it and came up with any ideas or maybe I missed something.
Right now I'm leaning towards the 4 banger because of this.

You made that model of the sterling to show how it's like a wing. Making the front lighter will sure help you get airborne faster. It's the stalling out part I don't like.*laugh*
 

ydeardorff

New member
Good point!:D

But placing the motor ahead of the wheels will place more weight forward, rather than aft. It might not be much,but any amount helps.
Hopefully a nose mounted gas tank, and rad will help too.

The EG33 is 22 inches long, which if placed behind the firewall would place the CV's way too far back. In that position it places the rear of the engine behind the center of the axles.

Moving the engine forward another 4 inches, would remedy that, but that will encroach into the cockpit behind the seats. Which can be tolerated to a minimum, but isn't what Im wanting if I can help it.

The four cylinder is a good choice. The engine would fit but actually still be a tight fit as the output shaft are 6.5" from the bell housing to the drive shaft on the WRX STI tranny(center) so it may in fact be still a tight squeeze within the engine bay too. But the impreza trans may be different, as the WRX STI motor is actually larger than the EJ22 by quite a few inches.

Ill need to find out how much deflection can be tolerated by CV's (while still being reliable for normal use) to find out what can or cant be done for both setups.


Anything is doable, yes, but that's also why I don't have the EG33 engine in the garage yet. I do already have an EJ22 in the garage. Being rebuilt. As a back up, for if the EG33 just isn't workable. Id just like more power out of it. But I'm not willing to spend 3K for the WRX STI setup. The six is the prefer choice because of the power, reliability, and smoothness of the motor.


140 hp will still be fun, but I'm going to exercise every option to test the viability of the EG33, before I give up on it.


It will be a carefully thought out decision before I decide on cutting into the body tub though.


P.S.
I just got off the phone with RCV performance, RCV PERFORMANCE ONLINE STORE - CV JOINTS - AXLE KITS - TOOLS and had an nice chat with one of their engineers They have custom center plunge type drive shaft available for decent prices, that can tolerate up to 45 degrees deflection. (thats the combination of the outer CV, and inner CV's angle) If the drive shaft is perfectly straight from the tranny to the wheel that is a deflection of zero.

So now out comes the protractor:D
This is the golden moment my trig teacher said would come back to haunt me.:D

rear engine and trans layout measurements.jpg
This is what I came up with, please feel free to double check my math.
 
Last edited:

Brett Proctor

Well-known member
Not sure what your measurments are to but here's how I interpolated your drawing.

Remember the axles are traveling in an arc and this angle needs to be part of the equation all so.

If I missunderstood anything sorry.

Left out the hyp = 26.401"
 

Attachments

  • 000_0138.jpg
    000_0138.jpg
    87.1 KB · Views: 1,131
Last edited:

ydeardorff

New member
Thank you, it has been 20+ years since I was in high school.

Time base amnesia sucks!

So the 22.5 degree mark would be closer to around 8 inches then? off of the 90 degree point?

I found the 45 degree mark based on measuring 2:1 ratio. Then I divided that in half again to get the 22.5 degrees.

I found a formula yesterday for this, and it was more confusing than helpful. LOL
 
Last edited:
Top