coyoteboy
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| posted on 10/9/10 at 02:51 PM |
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I'd only have 1 ecu to 2 engines if you have a solid crank or output linkage and guaranteed gear selection, then it would effectively act as one
engine. Otherwise it's got to be a pair, the risk of running the wrong timing on one that's slightly out is too high. I may be able to
re-write a chunk of the MS firmware to do some of the between-engine-difference monitoring but writing twin-engine encoders would be a whole re-write
of the code, and not even possible on the MS1 (not looked at MS2 in that much detail). They're not expensive enough to warrant that level of
time expenditure.
[Edited on 10/9/10 by coyoteboy]
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MakeEverything
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| posted on 10/9/10 at 03:09 PM |
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quote:
Originally posted by coyoteboy
I'm not sure they would be fighting that If you have a physical parallel link on the stick they either both go into gear or both don't.
Both engines will be different, as will their gearboxes with different amounts of backlash in all gears.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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Minicooper
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| posted on 10/9/10 at 03:15 PM |
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I think Chris from ZCars told me, in order to get the 4wd twin engined car to turn and handle there were £10,000 worth of electronics required.
The last time I spoke to Chris and was talking about twin engines and the like he said forget it, have a single mid engined lightweight powerful bike
engined you will go quicker around a track and it will be cheaper and much more reliable
Cheers
David
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coyoteboy
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| posted on 10/9/10 at 03:15 PM |
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Sure, but we're talking about minimising mis-shifts, not eliminating them entirely as that's as open to operator error as it is mechanical
error, but I suppose it's just one of those things where you have to do it to quantify it. The twin shifter idea makes sense in that you can
feel with each half of your hand when each engine drops in. If pneumatic/electronic shifting could 100% eliminate mis-shifts I could do that with some
ease, I'm already working on a similar system but it's as yet untested.
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coyoteboy
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| posted on 10/9/10 at 03:17 PM |
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minicooper -it'd be interesting to discuss it with him and exactly what those electronics are and the reasons behind it. I'm not saying
he's wrong, far from it, but I'd like to hear what he has to say with technical discussion so I could make that decision myself.
We're not talking a machine for racing, it's more of a "I'll do it because I can and for fun". I can probably create all
of the required electronics myself, as part of the fun. I won't do it if it's significantly poorer than a cheaper and simpler alternative
of course, but currently it looks about the same price as a decent 1ltr+ mid engined car.
[Edited on 10/9/10 by coyoteboy]
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Mr G
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| posted on 10/9/10 at 04:04 PM |
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The Fifth gear episode on the Tiger is HERE btw 
Normal is getting dressed in clothes that you buy for work and driving through traffic in a
car that you are still paying for - in order to get to the job you need to pay for the clothes
and the car, and the house you leave vacant all day so you can afford to live in it.
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mcerd1
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| posted on 10/9/10 at 05:23 PM |
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getting them in sync in a strait line is one thing, but what about when you turn a corner ?
then all 4 wheels need to turn at different speeds and the front axle needs to go slower than the rear (as its on a slightly smaller radius)
If you really must have two engines, it'd be much simpler to have both of them connected / geared together driving a central diff....
and even simpler again to just use one big engine...
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Stott
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| posted on 10/9/10 at 06:25 PM |
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There have been loads of twin engined cars on the modded car scene since the 90's, like Mk1 golf, mk3 golf, R5GTT, MK4 escort pickup effort etc
etc and they all worked with separate engines and gearboxes. All of these were road reg'd so I don't think it's illegal in any
way.
The mk3 Golf even had a 2.8VR6 in the front, and a 2.9VR6 in the back, so definately a mismatch but I don't think it matters. The more powerfull
engine helps the less powerfull engine to accelerate, like removing weight would help it accelerate. There isn't really a constraint on how fast
an engine can reach its limit, so the more powerfull one helping it get there quicker doesn't hurt at all.
The one's I have seen have all had the twin gear levers that can be locked when both engines are to be used.
I guess under engine braking there could be an issue with one axle slowing at a higher rate than the other but when you consider a std road car, there
is only ever 1 axle slowing or speeding up so that's as much of a mismatch as is possible.
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Canada EH!
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| posted on 10/9/10 at 07:11 PM |
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Look it the history books of the result of John Coopers twin Mini, I believe he spent some time in hopital as a result of his attempt at a twin engine
setup.
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coyoteboy
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| posted on 10/9/10 at 07:22 PM |
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quote:
getting them in sync in a strait line is one thing, but what about when you turn a corner ?
But I think it's not that much of a problem. They're not forced to stay at the same speed or revs. If they were driving a wheel each on
the back (like the furore) it would be a royal pain and possibly even more of a problem than per-axle - unimaginable torque steer is possible! As
stated before, if you have two people pushing a car, one at the front and one at the back, and the one at the front is a bit lazy, all that happens is
the lazy one gets a lighter load and the less lazy guy gets a harder load and may slip a bit if he's not careful. IF you tie their legs together
(same axle) they'll end up with broken legs from tripping over each other, but as far as each engine is concerned in a per-axle setup, each axle
just sees a slightly easier or harder job.
Whether someone ended up in hospital while trying it is not really important, thousands end up dead each year in normal cars, none or all of which may
be related to having one engine. In actual fact the feature I read on it seems to suggest the rear engine seized. Not really something that is an
inherent problem with twin engine cars.
[Edited on 10/9/10 by coyoteboy]
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coyoteboy
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| posted on 10/9/10 at 07:42 PM |
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Hmm and maybe something like a GSXR600 with a slipper clutch as a possibility to limit some of the effect of one engine pushing the other ?
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mcerd1
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| posted on 10/9/10 at 07:54 PM |
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it would be a real engineering challenge as a home build and if you want to build it then go for it
I just can't help thinking it would be cheaper and easier to just stick a turbo on the one engine......
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coyoteboy
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| posted on 10/9/10 at 08:00 PM |
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You're probably right, it would be simpler. Sticking a turbo on things is not necessarily easy thought, any of the lightish-weight engines that
can be turbocharged require significant modification to do so (cost of the engine again really to lower compression etc) and then have clutches and
gearboxes that can't cope with 2x the power output etc etc.
I have a possible donor for a normal car engine option that I can easily get to 300hp, but it's not 4wd. And not sequential.
What's a sensible, cheap bike engine I can get to ~200hp without significant internal mods and then a subsequently unreliable timebomb of an
engine, and then not have traction problems? Genuine question, not having a go!
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hillbillyracer
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| posted on 10/9/10 at 08:25 PM |
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I dont think the engines fighting each other is that much of an issue, in every 2wd car the unpowered axle is fighting the driven one all the time,
seems to work ok so far!
I know it's not just quite that simple but if one engine is'nt putting quite the same power out as the other it'll just not be
pulling quite as hard as the other.
If you picture a car being moved without the engine running with one bloke at the front pulling & another at the back pushing, if the one at the
back pushes harder than the one at the front pulls then the rope from the front bloke doesnt suddenly go slack & the car catch him up, he's
still contributing to moving the car but just is'nt working quite as hard.
And if the bloke at the back finds out he'll be pissed off but that probably wont happen to the engines!
I've just thought though, one thing that would'nt be so good would be if say the front engine suddenly died (snapped a throttle cable?)
while you were powering out of an opening corner, you front wheels get engine braking while your rears are pushing hard = brown trousers
[Edited on 10/9/10 by hillbillyracer]
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carpmart
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| posted on 10/9/10 at 09:27 PM |
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Twin engine set ups are very common in Autograss racing, I think its class 10 cars!
I'm sure Google will prove a great resource for this!
I believe there are even specific suppliers of the components to link to engines and transmissions who sell to the Autograss boys!
You only live once - make the most of it!
Radical Clubsport, Kwaker motor
'94 MX5 MK1, 1.8
F10 M5 - 600bhp Daily Hack
Range Rover Sport - Wife's Car
Mercedes A class - Son's Car
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hillbillyracer
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| posted on 11/9/10 at 07:42 AM |
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Yes very popular in Autograss, but there is no 4wd class (they're fast enough with 2wd!) & all engines must drive through a common
connection of some sort before driving the wheels.
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coyoteboy
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| posted on 13/9/10 at 09:16 AM |
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OK so there's been some fairly decent discussion here, I like the fact that there have been a few negatives thrown at me so what I'm going
to do is go away and try to summarise them all, along with weightings, against other power units (V6, highly strung 4pot, single large bike) and make
a decision on which to settle on and design around. Thanks to all for taking the time to argue through it with me!
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JoelP
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| posted on 16/9/10 at 07:04 PM |
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thinking today about the problem of them ending up in different gears, and theres a fairly simple solution. Have both engines with their normal rev
limiter via their own seperate ECUs, and have an additional rev limiter that would look at both engines, and if EITHER hits the limit, cuts the spark
to BOTH engines, thus preventing one being over revved.
Resync by having a seperate lever that only changes gear on one engine. This could be combined with a flat shifter on each too, if you have money to
burn.
Torque bias can be sorted simply by having the two throttle cables connected to different points on the accelerator, so one engine gets a little less
gas than the other. Make it adjustable and im sure with an afternoon on track you could set it up well.
Then turbo both.
My layout of choice would be a normal locost chassis, with one engine backwards in the normal engine bay powering the front wheels, and one in the
front of the passenger footwell driving the rear wheels. Still leaves room to scare a small passenger!
Beware! Bourettes is binfectious.
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coyoteboy
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| posted on 20/9/10 at 01:19 PM |
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IVA seem to be happy with a twin-engine setup even if it's one per axle, providing I can fill in all the boxes on teh application form!
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Bitten hero
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| posted on 26/9/10 at 11:03 AM |
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look up russ bosts original furore two engines two wheel drive each engine one wheel (no direct connection) nothing trick just a split double gear
stick.both engines completly seperate. worked real good.
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MikeR
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| posted on 26/9/10 at 11:22 AM |
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quote:
Originally posted by Canada EH!
Look it the history books of the result of John Coopers twin Mini, I believe he spent some time in hopital as a result of his attempt at a twin engine
setup.
In Summary - a ball joint got rusty and broke, nothing to do with a twin engine being dangerous. Something similar could happen to any car. In fact
John Cooper really liked it,
Quoted from "John Cooper Grand Prix Carpet-Bagger" The Autobiography of John Cooper with John Bentley
This particular Mini actually had two front subframes, installed back to back so as to accommodate both engines one up front and the other at the
rear. The subframe fitted at the back had, of course, been modified to perform its particular job, although it was basically the same as its front
counterpart. We had removed the rack and used the steering links as another suspension arm which pivoted on the subframe. Unfortunately, it was one of
those steering links that let go. To get into slightly more detail, it was the ball joint on the end of the link which we had secured to the subframe
instead of the rack itself. We had been testing this car some time previously in the snow, because the twin-engine Minis were very good under severe
conditions. Following a demonstration to the Press boys, the car had been put aside so that we might install some better engines with a view to racing
it. I think that what happened was pretty clear. One of the ball joints had somehow got snow in it, which produced enough rust to make the whole thing
sieze up and break off. As a result, a rear wheel suddenly made a sharp right turn there no longer being anything to keep it going straight and as I
was motoring along at probably 100 mph, the result wasnt hard to imagine. A sudden veering to one side, followed by a number of somersaults!
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Bitten hero
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| posted on 26/9/10 at 03:28 PM |
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a mention was made of massive torque steer with the engine set up to drive one wheel on the furore original No such thing one engine off half the
performance (on either engine so drive shaft length made no difference at all, if my finances eventually permit twin engines is my prefered way can
be done and has been done and very simply, and proved to work.although one at each end would give so massive traction and big big smiles.
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