I don't think I want the motorcycle engine. . .they trade off in RPM for displacement is a trade off for flow efficiency for weight.
The moto engine will be lighter, but it will get worse gas mileage.
Also. . .I doubt I can find a motorcycle engine with comparable power for the price. Less than a grand for all drive line components is pretty hard to beat with any sized engine and one that drops more than 160 horses and 137 lb-ft. is pretty impossible to get for less than 2.5 k. Even if there were fuel savings it would take forever to pay for that difference. Also the aftermarket parts to survive boost to attain the desired output I know are more expensive.
Moto engine would be way more expensive, to build and maintain, and less FE I am pretty sure.
I'm to the point of buying up final drive components and suspension.
I'm somewhat considering loading all the wheels up with ceramic bearings as well as the diff bearings in the rear. Whats the vote? Looks like ceramics will run 90 a bearing, whereas normal ones are whats on the parts. . .so free.
This guy did use a motorcycle engine with good results. Not all motorcycle engines rev to 10K rpms; a lot of the twin v and single jug engines have loads of torque and spin relatively slowly compared to the I-4 crotch rocket motors.
I think a 2 stroke dirt bike engine might even be fun.
Another idea I had, kind of off topic, but somewhat relevant, would be to have 2 motorcycle engines, and only use both when the extra power is needed. While cruising, 1 ought to be plenty.
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Quote:
Originally Posted by jamesqf
I think you missed the point I was trying to make, which is that it's not rational to do either speed or fuel economy mods for economic reasons. You do it as a form of recreation, for the fun and for the challenge.
I have thought about going with a v-twin(small displacement) moto engine, but I wasn't able to find one for the same price as I was able to get a full 2 liter 4A-GE silvertop with complete drive train. A survey of ebay and several engine shops that I work with said about 800 bucks for the engine. Then to harvest the neccessary components to get at least 2wd I'd have to drop another couple of hundred bucks, plus I still would be without the drivetrain(joints, bearings, diffs etc).
If I could find a complete drive for less than a grand for one I probably would have considered it.
That said, I found an engine that pulls reliable FE in a vehicle nearly 2kips more with more frontal area and a comparable Cd. Just with the 2,000lb weight reduction I ought to be able to hammer 50+ mpg from the corrolla engine and light chassis.
I enjoy pushing the envelope in all directions as far as possible, for that reason I stopped hunting anything less than 1 liter engines and moved on to full-blown engines with lots of aftermarket parts(rods, pistons, cranks, flywheels, clutches, etc). The second purpose of this vehicle is going to be quickness and cornering. Cornering has no bearing on engine(other than extra momenta), but the 250cc engine won't have enough block to survive heavy boost.
I'm aiming for 60+ mpg and 30mpg with the blower running hard. By hard I mean running 0-60 in 2.7-9 and 0-100 in 5.0-5.4.
The second stage after I reach those two objectives in once vehicle without modifying it between runs, I'm going to look at wiring in lean burn override so I can leave the blower on full tilt and just vary the resistance and achieve really high AFRs. I'll have to carry an onboard to monitor engine temps and control H2O injectors to keep temps under the fatigue limit. With that mod in place I think I ought to be able to beat out a stock old Insight and maybe one thats driven conservatively. Also it will run the water injectors outside of lean mode to keep the cylinders cooled because the iron block is going to have trouble with heat.
I'll be reworking the exhaust into straight pipes exiting directly out of the block out the rear of the chassis in a 4-1 system and I'll be mounting cooling fins on the block and trans themselves to supplement the oil coolers and coolant. All the secondary pumps(second radiator and oil coolers) will be on a switch and shut off during the winter(not that I am considering driving it in the blasting cold(current design has no wind-screen just a half canopy)).
I think I'm going to pass on the ceramics on the MKI. . .the MKII will probably see those as upgrades as well as anything else I find along the way. . .maybe an NSX aluminum block ^_^.
The objective of the project is to beat a prius in FE and to beat it in a race to 100(the prius only has to get to 60).
Oh, I obviously will be rebuilding the transmission that the silvertop comes with. I really have no need for either of the first two gears. So its going to be a shuffling down with 3rd as first and so on and then custom gears for 4rth and 5th.
I'm lining up a 6 speed for the MK II, but it will require extensive fab to mate to just about anything. I would just stick with a 5-speed and put 4rth as 1st but then the off the line speed would really be low and it would eat the clutch pretty badly. 3rd will supply way more torque than is needed to move a 1100-1300 lb object very quickly(stock the silvertop does 120-127 ft-lbs year depending, and supercharged I'm planning on getting alot more than that.)
Last edited by theunchosen; 06-07-2009 at 02:49 PM..
I like this idea. Not sure about the supercharger though. I think you will find the Toyota motor plenty zippy in a dune buggy chassis.
I've wanted to do something like this for a running around town car, but just have too many other projects on my plate. I also don't want to deal with passing safety and other considerations right now. BUT, if I were going to do it, I'd start with a 4 seater sand rail chassis, mod it for a FWD drivetrain mounted in the rear. Manual tranny, manual steering. Keep it fairly low to the ground. But not so low I couldn't take it on some trails...
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I am kind of torn on what you said. I have been considering ground clearance for the reason you mentioned.
It would be amazing to have a trifecta(Ecobox, super-car hunter-killer, and an offroad toy). I don't think I can do it though.
It obviously could be done but you would have to sacrifice a little on the ecobox and supercar fronts to achieve the offroad capability. Its only going to have enough ground clearance to make it over small, medium and extended speed bumps(3 inches). I'm also going to be using F1 front suspension and aftermarkets for the rears to keep it low. The wheel center is above the bottom of the chassis(which is flat except for a 2 inch drop that forms a scoop to cram air into the engine bay) with 14 inch rims and 185/60s on the front and something much fatter on the rears.
I have also put some thought to the blower. . .Its going to be on a clutch(think AC) so I can disengage it and engage a short track CAI instead when I am aiming for those 50-60mpg. I have a few local exotics that show up down at Thunder Valley(1/4 drag strip associated with BMS(Bristol Motor Speedway)) that are the targets of the Hunter-Killer and she is going to need the blower to accomplish a blowout defeat. It may be possible to destroy them without it(290 hp/ton without and 400-500 hp/ton with). . .but who wants to just beat a twin turbo NSX. . .^_^ I want to demolish it and get 30 mpg in the process.
I like your thinking. There is no reason you shouldn't be able to have an awesome sleeper/econobox. I wonder if you could take some cues from high end motorcycles, such as the Honda Goldwing, for some minimalistic body work to push the air where you want it. Do it clever enough and you can dodge some of the rain in a surprise rainstorm. Sometimes a very small windcreen can make all the difference in the world. That and keeping your electrics dry would be a nice benefit.
I can't say as how I can blame you for going for the cheaper solution; I'd probably do the same. I would think keeping your expectations low would be advisable. While you may be reducing the weight drastically, you will have quite a bit of drag if you're going for little to no bodywork. And I know I would have a hard time keeping my foot out of the throttle when there is a supercharger whining in my ear......
How long are you planning to make the buggy? If you're planning on doing any serious cornering, making it a bit longer than a typical go cart will give you a bit more stability and decrease your chance of oversteer.
From the sounds of things you're going to end up with a mini F-1 car! I'm severely jealous of you right now.
__________________ RIP Maxima 1997-2012
Quote:
Originally Posted by jamesqf
I think you missed the point I was trying to make, which is that it's not rational to do either speed or fuel economy mods for economic reasons. You do it as a form of recreation, for the fun and for the challenge.
The chassis is 7.5 feet in length total. I dropped in some screenshots I fabbed from sketchup to make an idea of the layers I wanted to make sure I get it right. Green is FG blue is CF as is Red and Yello but those are engines mounts and I don't think I have images of those layers. .. .
The new rear adds 2-3 feet of styling instead of it just ending. . .I'll get pictures up shortly . . .
Ok there they are.
I'm feeling graphite color. I forgot to upload images here. Not shipping it off with CAD and doing my molds myself so these are to get a feel for the look and the needed shape for various mounts.
To get back to the motorcycle suggestion, in case other people are thinking of it for their projects or just for brainstorming... Another problem with a motorcycle engine is a transmission. If you use a motorcycle transmission, do you want to push the car backwards every time you need to reverse? And the "reverse" gear on a Goldwing is basically a starter motor that contacts the tire to push it back. Impractical for a car and custom gear boxes are expensive. Even just staying stock, you can't really find decent motorcycle hardware cheaper than better automotive hardware.
Moto engines are really appealing especially the 250s(because they focus alot more towards FE than the big L4s). IT would seem that the moto engine would be cheaper. . .but they really aren't.
Motorcycles have virtually no features that make automobiles expensive(which makes it bizarre that any of them go for more than 5-6K. . .). Its actually not the features that make them expensive. . .its just the number of features and making everything fit together correctly in a very small space.
Also if you buy a complete block it comes with an AC compressor new most of the time which you can turn and sell on ebay for 150+ to recover cost(new compressors go for 300 of the shelf). Also you can sell the exhaust manifolds and a few other bits and pieces to make it cheaper.
Keep in mind motorcycles are considered high mileage with 20K miles(not that they will fall apart then). High mileage for a car is 100K(200K for Honda's ^_^), so if you are going to build something do you really wanna risk having to redo it in 4-5 years?
Also a note to anyone considering. Make your engine bay spacious. Leave ample room around the parts. If you have to take it to a mechanic they will charge you less if its very easy to access everything(it takes far less time and its far less frustrating). It also makes it much easier to maintenance almsot everything yourself if you have room(otherwise you'll need to disassemble 3-4 pieces to get at what you want and then its mechanic land).
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