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v8GTmac1

The Subaru tranny in a Lotus idea

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I had started playing with the idea months back and although it has taken a back seat due to funds for the 1.64" /41.7mm  plate needed. I wanted to populate all my measurements here rather then keep them all jotted down on several pieces of paper. So here it is...

-  a mid-engine capable 5 speed

- Trans mounted starter (Yes!)

- 8 bolt flywheel evenly spaced

-similar length as UN1

shifter linkages on rear aswell (hoping to use Lotus cables)

--------------------

EJ255 FW bolt holes   -   .4115"             Lotus FW bolt hole - .485" 

FW edge to edge/ bolt ->pilot .4695"

FW edge to edge/ bolt -> bolt .585"

pilot bearing hole - 1.256"                   Lotus spigot bearing hole  - 1.771"

FW bolts  M10 x 1.25                                Lotus bolts M12 x 1.25

8 bolt PCD      -   2.6064" (66.2mm)             Lotus PCD  - 2.757" ( 70 mm)

input shaft diam .470"                               Lotus input   .688"

                                                                    B/H bolt holes - .421"

    dowels OD .393 (10mm)                   dowels OD - .597"

    B/H holes .443-.445 (11mm)             dowel holes ID  .465"

 

 

 .

 

 

 

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Hi Michael,

Do you mean just the transmission or the engine and transmission ?    If just the gearbox i see no reason myself to replace the renault tranny for another 5 speed unit, maybe if the Subaru unit was 6 speed then i could see the reason for the change. 

i am pretty sure a company out there does a six speed conversion for the renault or a least much better internals, just cant remember the name of the company off the top of my head.

 

 

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That's I lot of work for little reward.  The torque capability on most stock scubby tranny's is less or equal to the UN1 027 which you have fitted.. It is also worth knowing a lot of the ratio's are not compatible for use in the Esprit.  .   The TY754VB or VN  which were fitted in the STi 5-6  will not take the power of the Esprit for long, the diff bearing are not man enough.  Even a STi wagon fitted with the forester  6 speed kit which will give you more still has the diff issue.   You would be better looking at the Audi O1E  6 speed out of the 2.5 diesel ..  Its worth remembering that all the work involved along with the cost will be more than fitting an uprated kit in the UN1  capable of taking far more power and just bolts in like for like. 

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Permit a few words about Subaru gearboxes...

I am making the assumption that you would like to change box because the UN1 is known to be weak, is somewhat sloppy and can’t take the torque out of the V8. 

We have raced, hillclimbed and rallied Imprezas’ for years (and still use one as our poor weather road car), the gearboxes are the weakest link. The EJ25 gearbox is significantly better than the earlier short ratio boxes. BUT much past 450bhp you will run into the same issues as with the UN1; broken input shafts, broken selector forks, broken rear layshaft bearings, and if you’re really lucky the casings can twist and crack and throw the secondary shaft out the side. They suffer from the same problems, which are mainly due to the rapid torque curve, as Imprezas’ are not powerful without the turbo boost, it’s the fact the boost comes in so dramatically the gearboxes suffer. In short, replacing a UN1 with the Subaru box in question would be a relatively pointless swap.

To give you an idea, to run an Impreza track car for a year at 460bhp, you’ll rebuild the engine twice and the gearbox probably six times if not just replacing it.

I don’t wish to kill your idea, but there’s zero point in doing all of the work and ending up with the same issues!

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20 hours ago, silverfrost said:

Hi Michael,

Do 

i am pretty sure a company out there does a six speed conversion 

 

Not any more, i've asked GTO about it. 

17 hours ago, CHANGES said:

That's I lot of work for little reward.  The torque capability on most stock scubby tranny's is less or equal to the UN1 027 which you have fitted.. It is also worth knowing a lot of the ratio's are not compatible for use in the Esprit.  .   The TY754VB or VN  which were fitted in the STi 5-6  will not take the power of the Esprit for long, the diff bearing are not man enough.  Even a STi wagon fitted with the forester  6 speed kit which will give you more still has the diff issue.   You would be better looking at the Audi O1E  6 speed out of the 2.5 diesel ..  Its worth remembering that all the work involved along with the cost will be more than fitting an uprated kit in the UN1  capable of taking far more power and just bolts in like for like. 

I would consider a different trans option but that leaves me with needing a custom flywheel/ring gear and still utilizing the Lotus starter. If someone can point out another affordable option that has a trans mounted starter????

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What is your reasoning behind doing it?

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17 hours ago, Blackngolds3turbo said:

Permit a few words about Subaru gearboxes...

I am making the assumption that you would like to change box because the UN1 is known to be weak, is somewhat sloppy and can’t take the torque out of the V8. 

We have raced, hillclimbed and rallied Imprezas’ for years (and still use one as our poor weather road car), the gearboxes are the weakest link. The EJ25 gearbox is significantly better than the earlier short ratio boxes. BUT much past 450bhp you will run into the same issues as with the UN1; broken input shafts, broken selector forks, broken rear layshaft bearings, and if you’re really lucky the casings can twist and crack and throw the secondary shaft out the side. They suffer from the same problems, which are mainly due to the rapid torque curve, as Imprezas’ are not powerful without the turbo boost, it’s the fact the boost comes in so dramatically the gearboxes suffer. In short, replacing a UN1 with the Subaru box in question would be a relatively pointless swap.

To give you an idea, to run an Impreza track car for a year at 460bhp, you’ll rebuild the engine twice and the gearbox probably six times if not just replacing it.

I don’t wish to kill your idea, but there’s zero point in doing all of the work and ending up with the same issues!

I actually dont want to increase the power levels (I say that now). I just want a reliable stock power Esprit without worrying the ring and pinion shatter and lock up on me in a intersection or in front of a semi truck. I really dislike the Roll pins for the axles. 

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2 hours ago, ramjet said:

What is your reasoning behind doing it?

Really just want to try a conversion for the first time. I can always upgrade to the 6spd if need more power. Needs to have the starter mounted on the trans and not on the engine side as the turbos wouldnt allow it. Keeping the Lotus starter is not what I want. Matter a fact I dont want anything but the Knock sensor sitting in the valley. 😥. Too much heat in Arizona. 

Updated my first post and will continue to do so as I retake some measurements. 

 

Edited by v8GTmac1

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actually I cant update the post......so here some more

Subby 5spd trans with FWD block off plate   =   26"

+ the linkages that hang out back   =                 2.75""

Un1 trans end ->end   27.5" 

amount of dead space behind Un1 trans before the body is 3.5"

Un1 is 1 1/4" shorter and with 3.5" of dead space leaves  2 1/4" of room for Plate which I calculated at 1 5/8 already. 

Edited by v8GTmac1

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What's your aversion to all the Lotus bits on the engine Michael?

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I once read about the friend of a mate whos neighbour had this very issue.

forgotten what make of car it was now - but it’s a very real concern :sofa:

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4 hours ago, Barrykearley said:

I once read about the friend of a mate whos neighbour had this very issue.

forgotten what make of car it was now - but it’s a very real concern :sofa:

If your talking about the CWP 

That one is a good example of locking up in a intersection. I shopped a lot of Esprit's before owning one and heard a lot of different stories.  

Like the guy selling random parts on Craigs, he used to have a v8 but blew up 500 miles after rebuild and gave up. I have to hear this as i'm about to embark the same journey?

Edited by v8GTmac1

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8 hours ago, ramjet said:

What's your aversion to all the Lotus bits on the engine Michael?

Clarkson warned about meeting my Hero's. The first time I drove an Esprit ~8 months ago I already began to recall his words and fear started to set in but my Lady kept me motivated as she also loves it. I love to tinker so I will innevitable convert to Megasquirt and COP. It's just too damn hot out here in the Wild West.

I'm taking bits and pieces of advice from every expert be it this forum, JAE, PBC, and listening to actualy owner stories, then you have me wrenching for 20 years with my own ideas. Truth be told, they are sometimes conflicting advice!! 

Edited by v8GTmac1

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2 hours ago, v8GTmac1 said:

If your talking about the CWP 

That one is a good example of locking up in a intersection. I shopped a lot of Esprit's before owning one and heard a lot of different stories.  

Like the guy selling random parts on Craigs, he used to have a v8 but blew up 500 miles after rebuild and gave up. I have to hear this as i'm about to embark the same journey?

Yup smashed a set myself. Not really an issue and more a fault of the company whose rebuilt that gearbox previously

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COme on Fellas!😒😏😥

Lets have some positive forward thinking, somebody has to try some out of the box thinking. I'm gonna push for the project to take shape unless someone can present me with a mid-engine trans that has the starter in the "right" place. Not Audi/Vw, Not Porsche, Not Mendeola $$$, and for god Sakes not this ---->Acura

Lotus 8" bell to Axle centerline

5239b111dc85458fb103867bd9e4bc7a.jpeg

SUbby 6.5" bell to Axle center line.   Add 1 5/8 adapter and.......

1887de5c4a1849e1866bc5302049efd2.jpeg
 

 

9 hours ago, Barrykearley said:

Yup smashed a set myself. Not really an issue and more a fault of the company whose rebuilt that gearbox previously

I smashed something in a FWD myself, might have been my fault aswell but since the semi truck ate the car whole, I never found out what caused the near death experience, I just know what it sounded like and how fast the car could come to a stop from 80mph. 

Edited by v8GTmac1

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The problem i see is there is no reason to even consider this conversion as it has no benefits at all in my eyes.   The starter been n the trans side i do not understand as it has no problem been on the engine side on the lotus v8 engine and one could be fiited to any transmission on the trans side if a person really wanted to do it by just welding in and attachment plate on the bellhousing and reverse gearing the starter imo.

It is your car and we are all entitle to do anything we want with our cars, but from a forum and that will also include any other forums you use,  it is hard to think outside the box for a problem that in my eyes does not need solving in the first place.  

Just my two cents,  If you do go ahead it will still be intresting to follow your project but i just feel it will be for no benefit. 

Plenty of V8s running extra boost and still on the factory standard trans will plenty of miles on them.  :) 

 

 

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Someone else with no engineering finesse or competence 

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I've been thinking about the Subaru box for a while, but I'd only do it if I could fit an H6 engine in there as well.

My esprit turbo engine has never been reliable even though I've replaced almost everything to do with the fuel and ignition systems.

It's on it's last chance now. I've just had the dellortos ultrasonically cleaned again and getting rid of the lumenition system while the carbies are out.

The 1st gear ratio is a bit too high to use in traffic compared to most cars. It's more suited to racing.

Injectors are easier to replace than rebuilding carbies, electronic ignition and no timing belt and a simple cooling system.

I just don't know if it would be too wide for the chassis.

Then there's the whole inboard brake thing to think about and centre diff to disable. So not as simple after all.

Anyone else thought about the H6 ?

 

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No way the H6 will fit - it is far too wide and the heads would end up right where the radius arm mounts are, so you would have to completely redesign the engine cradle and suspension. However an Audi v6 does fit and then you have the choice of 6 speed gearboxes of various strengths.....

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