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Learning how to build Lotus Seven replicas...together!
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PostPosted: Wed Dec 01, 2010 5:47 pm 
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http://jalopnik.com/5703588/kmv4-a-mini ... otorcycles

Not quite the half an LS7 like they refer to, but it poses some interesting possibilities depending on what the back side of the engine looks like. It seems it doesn't have ports like the LS7 and the displacement is just shy of 1/4 the LS7 vs half. I imagine that why the power isn't half an LS7 either.

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Awww, isn't this tiny, four-cylinder copy of the Corvette LS7.R's architecture cute? The 1,645cc V4 is destined for a new American performance bike, but only weighing 130lbs, it could be near ideal for engine swaps or kit cars. This V4 literally is half an LS7.R, just downsized. Dubbed the KMV4, it's being produced on the same assembly line as that ‘Vette race motor by Detroit's Katech Engines. Like the 7.0-liter V8 that powered the Corvette GT1 to Le Mans victory, this V4 has a 90° V, is made from aluminum and uses nickel-silicon-carbide-coated linerless bores. There's two pushrod valves per-cylinder, a chain-driven single cam mounted in the valley between cylinders and hydraulic valve lifters. Where the production LS7 puts out 505 HP and 470 Lb-Ft, the KMV4 makes 120 LB-FT at 4,500 RPM (exceptionally low for a bike engine) and 140 HP at 7,800 RPM.

The bike it's going in is called the Motus MST-01 (Katech + Motus + V4 = KMV4), which is entering the final stages of running prototype assembly at its Birmingham, Alabama factory. Intended to be a sort of real-world sportbike or a "sport tourer" in the two-wheeled parlance, the MST-01 is targeted to be all-day comfortable for real humans without sacrificing performance. The LS-motor architecture is a big part of that, giving Motus a huge spread of usable torque to counter the typical sky-high revs of most performance motorcycles. Of course, other LS-motor benefits apply too, there's no need for valve adjustments and the motor remains incredibly simple and easy to work on. It's weight is also on par with much smaller engines, despite nearly doubling the typical motorcycle capacity.


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edit: an image of the rear
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PostPosted: Wed Dec 01, 2010 6:02 pm 
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I saw this today as well and it sure piqued my interest! I wonder what sort of transmissions would bolt up to it for a locost...


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PostPosted: Thu Dec 02, 2010 10:14 pm 
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There was a long thread on this motor a while ago. VERY VERY expensive
As I recall in the $20k range. Yes 20K Nascar type parts.

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PostPosted: Thu Dec 02, 2010 10:29 pm 
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I don't understand why stuff like this gets attention... well, okay, I do. It's like looking at Angelina Jolie and thinking, "yeah, I could date her." Sure... if you ignore the entry fee and cost of upkeep.

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PostPosted: Thu Dec 02, 2010 10:53 pm 
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I'm curious, what's the obsession with pushrod* engines and 2 valves per cylinder over here? Why not OHC and 4-valves? It's like going back to the 80's :)

Am I missing something obvious here? Or am I just too used to lovely revvy Euro/Jap engines? :)

*Ok, I get that a pushrod engine can be a little shorter, anything else?


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PostPosted: Thu Dec 02, 2010 11:44 pm 
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Tom17 wrote:
I'm curious, what's the obsession with pushrod* engines and 2 valves per cylinder over here? Why not OHC and 4-valves? It's like going back to the 80's :)

Am I missing something obvious here? Or am I just too used to lovely revvy Euro/Jap engines? :)

*Ok, I get that a pushrod engine can be a little shorter, anything else?

I don't think the obsession is with pushrod engines. The LS and previous small blocks have proven to be, time and time again amazing engines for their weight and cost. LS engines are really light, quite compact and at the very least always pack quite a punch. I think that says enough.

Personally I can't wait until GM hops on the DOHC train. They touched on it with the LT5 and made a series of GREAT engines with the northstars. I think it's about time they got with the times.


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PostPosted: Fri Dec 03, 2010 1:14 am 
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What's better about DOHC engines? What they are good at is convincing people to give more of their money to the manufacturers, basically.

Locosts and especially Sevens are quite small cars, it's difficult to fit these modern engines in them. If you want a certain amount of HP, what difference does it make wether you have the extra cams or not? Are you going to spend thousands of hours building something and then feel smug while your driving down the road because you have more cams then the other guy? It just doesn't make sense for it to be a primary factor...

In general the complexity in modern cars is getting out of hand. At this point they are basically becoming disposable items. Very expensive disposable items. If you get a Locost running, there is no reason you shouldn't be able to use it for decades. If it's EFI you would probably have to replace that stuff periodically or move to carbs though. :)

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PostPosted: Fri Dec 03, 2010 7:35 am 
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horizenjob wrote:
What's better about DOHC engines? What they are good at is convincing people to give more of their money to the manufacturers, basically.

Locosts and especially Sevens are quite small cars, it's difficult to fit these modern engines in them. If you want a certain amount of HP, what difference does it make wether you have the extra cams or not? Are you going to spend thousands of hours building something and then feel smug while your driving down the road because you have more cams then the other guy? It just doesn't make sense for it to be a primary factor...

In general the complexity in modern cars is getting out of hand. At this point they are basically becoming disposable items. Very expensive disposable items. If you get a Locost running, there is no reason you shouldn't be able to use it for decades. If it's EFI you would probably have to replace that stuff periodically or move to carbs though. :)

I am in total agreement with the above statements, except for the one about EFI. My family (wife and three sons) are currently driving seven cars with EFI. One has 80,000 miles on it, the others are getting uncomfortably close to 200,000 (one is over) with no issues. Am we living under a lucky star? If so, that would be the first time.

As to pushrod engines vs. DOHC, I think the pushrod makes sense when space is an issue. Not at all convinced the DOHC offers more HP per cubic foot of engine room consumed. Does anyone have any data on such a subject?

Bill


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PostPosted: Fri Dec 03, 2010 9:41 am 
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bremms wrote:
There was a long thread on this motor a while ago. VERY VERY expensive
As I recall in the $20k range. Yes 20K Nascar type parts.


Since this engine hasn't actually been released yet and is still in the design/ concept stage, I'm going to assume you mean the scat(sp) engines.

This has been designed as a motorcycle engine and depending on the market they are going for could be quite well priced if they manufacture in quantity. Even still a 'cheap' engine brand new you'd be probably $10k if they aren't a limited production item like the scat's were...


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PostPosted: Fri Dec 03, 2010 2:37 pm 
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Now before I start, I get that the Locost mentality is keeping it cheap & simple, which excludes bleeding edge engines. It also excludes this engine due to its price tag, even though it has desirable properties for a locost, being both short (not too tall) and short (not too long). I get that these tall OHC engines are a pain to try to fit under a Locost bonnet.

But what I don't understand is why this engine was developed on this format. It was not developed for a locost :) The rest of my post is more 'in general' rather than locost specific...

horizenjob wrote:
What's better about DOHC engines? What they are good at is convincing people to give more of their money to the manufacturers, basically.

I guess the main advantage is a lower valvetrain reciprocating mass. This can let you run higher revs, run weaker valve springs, reduce valvetrain wear (increasing reliability), reduce power needed to operate the valvetrain. Those are just the advantages of OHC, not DOCH. When you get to DOHC you can then easily ramp up to 4 valves per cylinder (yes, I know it CAN be done with OHV or SOHC, but the packaging constraints are tricky). When you get to 4 valves per cylinder, you can have lighter valves & weaker springs, (reducing valvetrain reciprocating mass & stress even further), smaller ports leading to higher port velocities at lower RPM (increasing efficiency) angled valves and higher total port & valve opening area given the constraints of a given cylinder (giving higher potential flow).

horizenjob wrote:
In general the complexity in modern cars is getting out of hand. At this point they are basically becoming disposable items. Very expensive disposable items. If you get a Locost running, there is no reason you shouldn't be able to use it for decades. If it's EFI you would probably have to replace that stuff periodically or move to carbs though. :)

I get that cars are too complicated and I agree. I miss tinkering with my SU carbs and the dizzy on my old Minis (I'm hoping a Locost will be a nice substitute :) ), but this added complexity does come with its own set of advantages. When you look at the performance of a good modern euro/jap engine and compare it to these LS engines, it becomes quite staggeringly apparent.

People are saying that the LS is an amazing engine, but I just can't see it myself. The power per litre for these engines isn't what I would consider stellar. I don't really know the world of the LS engine so please correct me if I chose an incorrect LS engine for this comparison. Compare, say, a 6litre LS2 producing ~400bhp (66bhp/litre) with a BMW S65 producing ~414bhp (103bhp/litre). Note that the LS2 uses 50% more capacity to produce less power. How this is an amazing engine, I am not quite sure. Granted, it has a LOT of torque and all the power is low down, is this the defining property of an amazing engine? Now, anyone know how size/weight compares on two engines such as these? I'm genuinely curious now as power/weight/size seems to be the primary discussion here, rather than power per litre which appears to be my angle.

Sorry i've gone on quite a bit, I was wondering if maybe I shouldn't post this as it may come across a bit trollish, but really I just love discussing pros & cons of different car tech. I'm not trying to bash these engines, i'm just trying to understand the appeal/advantages, I really am curious :) I understand lots of the reasons given - simplicity, cost, knowledge - but are these really enough good points to throw away all that power? If they are then cool, I get it :)

As an interesting side note, against what I have been saying, my old 998cc BMC A+ engine would put out about 105bhp - about the same bhp/litre as the above mentioned bimmer engine. My Mini was 8v OHV and wasn't even a crossflow head (3 exhaust & 2 inlet ports). OK, so it made no pretense of trying to be reliable and no usable power below about 5000rpm (redlined at 9, destroyed itself at 9500+ ;) ). If that engine can do it, it's got me thinking even more on this subject now. *Sigh* why is there always one more thing to get you thinking :)

Tom...
Oh yeah, when I grew up, most of the new cars did have "16v" or "OHC" or "EFI" or somesuch label in the branding to indicate the new tech being used. People *did* love to show it off hehe :) Was it the same over here?


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PostPosted: Fri Dec 03, 2010 4:26 pm 
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Where are people getting price? It's an unreleased engine, but it's designed to use GM parts. It's derived from a solid engine (LS-series) and uses a lot of the same off-the-shelf components as well as built with a lot of wiggle room for "hotrodders."

While it's easy to say "Yeah, it'll probably cost like 500k" and dismiss it, why not be less negative and talk about the positives like possibility, and scalability before dismissing it so easily?


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PostPosted: Fri Dec 03, 2010 5:29 pm 
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If you want to read more about OHC vs pushrod engines, find any ford or chevy board and I'm sure it will have a big nasty thread with all sorts of mudslinging. From my prospective the LSX series of engines get great fuel economy with the right gearing, and they produce great torque and power when compared to the newest OHC engines in production cars. When people pick on pushrod chevy engines it reminds me of Jeremy on Top Gear making fun of the fiberglass body and rear leaf spring on new corvettes. In the end it runs a very respectable time around their track. From chevrolet's standpoint there isn't anything broke to fix. The engines meet the requirements of their cars and do it very well. I myself prefer low rev power and torque for a daily driver or acceleration car. If I were a road racer with rolling starts I might care less where the power is made in the rpm band. I still miss the roots supercharged v8 in my mustang. Even my four cylinder motorcycle doesn't feel as fast becuase of the lack of low end torque. With a motorcycle or lowcost, some lack of torque down low is likely a good thing for traction. :shock:

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PostPosted: Fri Dec 03, 2010 5:53 pm 
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OK, i'll look around to get ideas of why they are so good. Didn't mean to threadjack in here :)

I guess it's another one of those internet arguments of this Vs that where no side ever agrees with the other. I didn't realise this. Now I do so I won't carry on in here :)

Tom...


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PostPosted: Fri Dec 03, 2010 7:15 pm 
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If you want to read more about OHC vs pushrod engines, find any ford or chevy board and I'm sure it will have a big nasty thread with all sorts of mudslinging.


Well that doesn't sound like a very good idea then. :)

From the picture, and I forget the details of our earlier thread on this motor, it looks like the transmission is under the crankshaft. That explains why they went for pushrods in this case, because they needed the room to be able to fit it in a motorcycle. Tom, I think most of your comments were correct. The big deal for the DOHC setups is the increase in valve area when you go to 4 valves and also the ability to turn the motor faster. These engines do produce more power per litre. I don't think of the number of litres as being a primary cost though. Except for the way that racing rules are written or perhaps tax or other laws in some countries.

I don't really care a great deal anymore one way or the other. I just feel the knee jerk reaction that it needs to be DOHC and at least 4 valves per cylinder and variable timing etc. adds up to a lot of complexity and space and not really any benefit for a Locost.

I watched a mechanic friend the other day repairing the variable valve timing on a Volvo and it looked like it was going to cost some major money...

As for my comment about the EFI, I don't think it's a big issue for number of miles, I have got 250k miles out of EFI cars. I think time will be less friendly though, somewhere after 10 years all that wiring, sensors and computer start to look more iffy. The computers just aren't built to last forever, they don't have moving parts unless you consider all those uncountable atoms that will screw things up if they migrate a few billionths of an inch...

Tom, don't be afraid to post here on this site, discussion is encouraged, exchange of opinions etc. No bullying, politics or crappy behaviour though. Once in awhile we'll split a post or thread up to keep the topics a little more tidy.

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PostPosted: Fri Dec 03, 2010 7:45 pm 
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I didn't mean to sound like I was on one side or the other. I don't feel strongly either way. Being an engineer I really like the stated benfits of OHC motors. t the end of the day it's how the motor performs that I put value in. I owned two mustangs with SOHC and DOHC engines, and my miata and STIs were all OHC. The LSX crowd likes to tease others with OHC engines that don't make nearly as much power or get good fuel economy. They get the same flak from OHC owners. My biggest concern about what donor to use for a locost would be how easy it is to modify to get more power and torque down the road once the car is well sorted out just to be road worthy and fun to drive. Anymore that capability seems to be tied to the openess of the stock ECU to reprogramming or a good aftermarket controller that still idles and drives well. :cheers: PArty party. :mrgreen:

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