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Author: Subject: Engine sits high
Alez

posted on 18/12/11 at 02:13 AM Reply With Quote
Engine sits high

Since years ago, it's become very a common approach to take a transverse engine + transmission as found in most FWD cars and use it to build all sorts of middle engined cars: Riot, Atom, Elise, MR2 and so on.

The one thing I don't like about this, compared to other arrangements like say the Locost, is that I get the impression that the engine ends up sitting a lot higher because the transmission sits kind of underneath.

Then there are middle engined cars using other approaches, such as chain driven bike engined cars, BECs using a special transmission like the Radical SR3 and cars using a longitudinally mounted engine coupled to a transaxle.

I know many examples of chain driven bike engined cars, I think they are ok but they can handle little torque. If you make them handle good torque and your tyres have good grip, you need to readjust and retension the chain all the time. The chain is most typically the weakest link in terms of reliability.

I know few cars using transaxles and they are all expensive. You have big V8 Ultimas, tiny Retogas using Elite Racing Transmission boxes, Norma Le Mans type things where the gear box is a fully stressed member and so on.

The summmary would then be:
-Go classic front-middle engined
-Have the engine sitting high-ish
-Go chain driven which is unreliable
-Spend big on whatever transaxle thing
-Spend big on an SR3-like BEC solution

Comments and opinions, please? What options am I missing? What do other cars use, like say Nobles or whatever else out there? Why not couple whatever 2 liter 4 cylinder engine to a cheap transaxle like those classic Renault ones? What's the reason why nobody seems to be going that route? On the high engine option, would it be possible to like tilt the power train, i.e. make the cylinder heads point more towards the occupants in order to make it sit lower, maybe using a dry sump system? Would that help?

Enough thinking for the day, off to bed...

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kb58

posted on 18/12/11 at 06:24 AM Reply With Quote
quote:
Originally posted by Alez... Why not couple whatever 2 liter 4 cylinder engine to a cheap transaxle like those classic Renault ones? What's the reason why nobody seems to be going that route? On the high engine option, would it be possible to like tilt the power train, i.e. make the cylinder heads point more towards the occupants in order to make it sit lower, maybe using a dry sump system? Would that help?...

Cost and complexity. With enough money you can do anything, but typical builder's aren't rich. You can indeed tilt the drivetrain - I did - but you can't go too far before you run into oil drain-back issues. A drysump doesn't help since the bottom of the flywheel and transaxle bellhousing is just as low as the OEM pan.

Really, lowering the engine further simply isn't a hard requirement for amatuer-built cars. Sure, if you're in a hardcore race series it's a big deal, but typical builders aren't. Summed up, there's no practical reason to bother. Using a dead-stock FWD drivetrain mounted mid-engine in a car that weighs less than half the original gives plenty of performance for most people.

[Edited on 12/18/11 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

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orton1966

posted on 18/12/11 at 07:28 AM Reply With Quote
Midi Options

I have/had the same dilemma, Id also add that going the midi route with a regular fwd engine/box also makes the car rear heavy as the engine sits right over the rear axle line, more rear-engined than mid-engined

In an ideal world Id have gone light high reving car engine on a proper transaxle but cant justify the cost of a racing transaxle. On a side note these seem ridiculously priced even second hand for ones regarded as unreliable and fragile!

I did consider Audi or Subaru units but these produce a lot off rear overhang, arent light etc.

One ingenious solution Ive seen was on a car called the Onyx Mongoose, now unavailable, although I believe the company is still trading. Bassicly they took a regular fwd engine box and inserted an adaptor plate to allow the engine to be rotated forward, in relation to the gearbow, doing this had two benefits; it lowered the centre of gravity and additionally moved its mass forward.

So my conclusions were as follows: if I was making a big engined car GT40 replica etc. Id have used an Audi or Reanault Transaxle, for a small light vehicle Id go proper new transaxle, on a sensible budget (my decision) go chain drive and bike engine

[Edited on 18/12/11 by orton1966]

[Edited on 18/12/11 by orton1966]

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liam.mccaffrey

posted on 18/12/11 at 08:53 AM Reply With Quote
I wouldn't say my front middy volvo 850 engine/gearbox combo is any higher than it would be if it were mounted north south as in a seven.

My sump sits about 2-3" below the chassis rails iirc





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MakeEverything

posted on 18/12/11 at 10:36 AM Reply With Quote
The advantage of using a transverse engine and subframe, is that you can get the engine, transmission and drive train all in one package, and just build the rest of the frame around it. Mine is mid engined using a transaxle and is plenty low enough, with the sump about 15mm below the chassis.





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f750sgr

posted on 18/12/11 at 11:08 AM Reply With Quote
Not Locost, but it does show what you can do to a fwd transverse donor.

Race kits Falcon

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Simon

posted on 18/12/11 at 04:44 PM Reply With Quote
I think you'll find most fwd engine/box combo's have the box of to the side with the output for the driveshafts rearwards!

'twas the Mini (proper one) that had the box under the engine

ATB

Simon

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matt_gsxr

posted on 18/12/11 at 05:15 PM Reply With Quote
Are you familiar with this car?


I believe it uses a duratec and associated FWD gearbox, but then drives each rear wheel from chain. So, 2 chains and half the torque on each, and a bit more freedom on orientation of things (I guess).

To my mind it is about the prettiest home-built car I have ever seen. (Lotus c23 perhaps excepting).

The lotus c23 also does a decent job of keeping height down (duratec engine, audi transaxle, clever adapter).

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matt_gsxr

posted on 18/12/11 at 05:16 PM Reply With Quote
more details of eclipse in this thread. http://www.locostbuilders.co.uk/viewthread.php?tid=155961
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iank

posted on 18/12/11 at 05:21 PM Reply With Quote
Transverse FWD engines sit no higher or lower than a longitudinal RWD. The gearbox sits on the end on all modern engines not underneath.
I can only think it's either the mini with it's gearbox in the sump thatmakes people think they're all like that, or the fact that almost all modern OHC engines are higher than the old engines in RWD's.

Here's a picture of a Zetec on an iB5 gearbox. As you can see it's above the bottom of the sump, which in itself is pretty shallow compared with some.



[Edited on 18/12/11 by iank]





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kb58

posted on 18/12/11 at 05:36 PM Reply With Quote
quote:
Originally posted by iank
Transverse FWD engines sit no higher or lower than a longitudinal RWD. The gearbox sits on the end on all modern engines not underneath....

^This. As was said, the bottom of the flywheel is what dictates overall height of the assembly, and a FWD lump is no higher than it's front-engine/rear-drive counterpart.

The Honda K24 I used is virtually the same height whether used at the rear of the car or the front, 4" under the pan/bellhousing.





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

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Alez

posted on 18/12/11 at 07:12 PM Reply With Quote
quote:
Originally posted by kb58Really, lowering the engine further simply isn't a hard requirement for amatuer-built cars. Sure, if you're in a hardcore race series it's a big deal, but typical builders aren't. Summed up, there's no practical reason to bother. Using a dead-stock FWD drivetrain mounted mid-engine in a car that weighs less than half the original gives plenty of performance for most people.

I do frequent track days and I'm more interested in the handling than in the performance, in fact the handling is the main reason why I personally favour mid-rear engined cars over traditional mid-front. Actually, the reason for all this thinking is that I have an Ultima which has absolutely perfect handling, and I'm wondering how to get a similar handling in a smaller and cheaper car.

quote:
Originally posted by orton1966In an ideal world Id have gone light high reving car engine on a "proper" transaxle but cant justify the cost of a racing transaxle.

It doesn't make sense to me either that half or more of the total build cost goes to the transmission, hence this thread.

quote:
Originally posted by orton1966One ingenious solution Ive seen was on a car called the Onyx Mongoose, now unavailable, although I believe the company is still trading. Bassicly they took a regular fwd engine box and inserted an adaptor plate to allow the engine to be rotated forward, in relation to the gearbow, doing this had two benefits; it lowered the centre of gravity and additionally moved its mass forward.

Very interesting, it would be nice to see a good set of pictures of that.

quote:
Originally posted by SimonI think you'll find most fwd engine/box combo's have the box of to the side with the output for the driveshafts rearwards!

Indeed it could be a wrong impression, I haven't seen so many engine bays of cars like that, but one that's very easy to find pictures for is the Atom (since it's got no bodywork) and whenever I look at pictures of it I think it looks like the engine was next to the occupant's heads.

quote:
Originally posted by matt_gsxr
Are you familiar with this car?

I believe it uses a duratec and associated FWD gearbox, but then drives each rear wheel from chain. So, 2 chains and half the torque on each, and a bit more freedom on orientation of things (I guess).

To my mind it is about the prettiest home-built car I have ever seen. (Lotus c23 perhaps excepting).

The lotus c23 also does a decent job of keeping height down (duratec engine, audi transaxle, clever adapter).

OK, that's yet another two interesting solutions, and no I didn't know either, or to be more precise I had seen both but never paid attention to the drive train, assuming it would be similar to all others.

quote:
Originally posted by iankTransverse FWD engines sit no higher or lower than a longitudinal RWD. The gearbox sits on the end on all modern engines not underneath.
I can only think it's either the mini with it's gearbox in the sump thatmakes people think they're all like that, or the fact that almost all modern OHC engines are higher than the old engines in RWD's.

Here's a picture of a Zetec on an iB5 gearbox. As you can see it's above the bottom of the sump, which in itself is pretty shallow compared with some.

Indeed so it seems looking at the picture, I suppose it's a wrong impression then, my post doesn't come from a measuring tape exercise at all.

quote:
Originally posted by kb58^This. As was said, the bottom of the flywheel is what dictates overall height of the assembly, and a FWD lump is no higher than it's front-engine/rear-drive counterpart.

The Honda K24 I used is virtually the same height whether used at the rear of the car or the front, 4" under the pan/bellhousing.

Looks like a case closed then...

Just so we have as many solutions as possible summarized in one thread, I'd like to mention this interesting email I've received from Marco:

"
As I can't post on locostbuiders I hope you still use this email adress.

http://www.blackbird-gtr.co.uk/

Look at how a bike engine is mounted at the rear to a Differential.
With a Hayabusa or ZX14 you would have reasonable torque and BHP...
And no chain in sight!

Regards,

Marco
"

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Alez

posted on 18/12/11 at 07:37 PM Reply With Quote
quote:
Originally posted by orton1966Id also add that going the midi route with a regular fwd engine/box also makes the car rear heavy as the engine sits right over the rear axle line, more rear-engined than mid-engined

I'm ok with that. It's clearly not ideal in terms of weight distribution, but it helps steering by putting that weight close to the rear axle, which is the only point in the car that never changes direction...

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Alez

posted on 18/12/11 at 07:50 PM Reply With Quote
quote:
Originally posted by matt_gsxrThe lotus c23 also does a decent job of keeping height down (duratec engine, audi transaxle, clever adapter).

The Duratec engine is mounted longitudinally I suppose? I always thought this arrangement would be the most straightforward option and I'm surprised that it's not used much. Maybe the Audi transaxle is overkill in terms of torque handling capability, adding unnecessary weight? Or maybe the resulting power train is very long?

My Ultima uses an Audi power train, the engine is the 4.2 V8 used on the S4 and the transaxle comes from a Passat TDI as far as I was told. Not sure if that's the very same transaxle you mentioned, but I'd say it's definitely overkill for a 2 liter 4 pot.

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coyoteboy

posted on 18/12/11 at 11:04 PM Reply With Quote
Indeed most FWD arrangements have the box to the side and the outputs to the rear, allowing the engine to be leaned backward or forward if needed, but technically there's no reason at all for it to be higher than any other configuration. The only configuration that might NEED to be higher is a front engined 4wd using solid axles or a front diff, due to the underneath arrangement of the front axle. Even 4WD front engined audis have the engine pretty damn low by shoving it forward and putting the diff part way up the back of the bellhousing.

MR2 turbo engine:



Pug Mi16 engine (i think)


[Edited on 18/12/11 by coyoteboy]

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TheGecko

posted on 19/12/11 at 02:42 AM Reply With Quote
Just to add to the chorus pointing out that most modern transverse FWD drivetrains have the gearbox end-on to the engine and the axle line not that far below the crankshaft centreline, here's photos of my original Corolla Silvertop drivetrain and the Mitsubishi Lancer 4G69 package I'm using now.

FWD Corolla drivetrain
FWD Corolla drivetrain





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hughpinder

posted on 19/12/11 at 04:40 PM Reply With Quote
I am using a zetec and standard box from a mondeo. The engine is tilted forwards 12 degrees in the standard car. I intend to use the engine tilted forwards to 22 degrees, (extra baffles in the sump to stop the oil surge on braking - I saw the onyx and that was their major problem) you end up with the 12cm of ground clearance and drive shafts parallel to the ground when using 195/50/15 wheels and tyres. This gives a height to the top of the engine of 64 cm (with the 12cm ground clearance). The centre of mass of the engine and box is 24-25cm in front of the drive shaft centre line when installed this way). You can see the mock up in my avatar/gallery.

Regards
Hugh

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kb58

posted on 20/12/11 at 02:39 PM Reply With Quote
Another thing to note is how nicely a FWD assembly installs into the rear of a car. Doesn't require the car to get abnormally long, and it's one reason why I used one on my Sevenesque car, Midlana. However, I do agree that even though the engine is ahead of the rear axle centerline, it does result in a sizable rear weight bias. I haven't checked mine recently but it's somewhere between 60-70% rear weight-biased. Depending upon driving style, it's either no issue, really fast, or scary.





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

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