Locost builders sometimes start with a FWD engine because they’re more widely available, then separate the engine from the transaxle and use an adaptor plat to connect it to an inline transmission; all this so that the engine stays at the front of the car. Right front the start, Midlana uses the entire FWD drivetrain as-is, installed behind the driver* and ahead of the rear axle, forming a mid-engine layout. Advantages:
FWD drivetrains are far more common than front-engine rear-drive setups.
It combines the engine, transmission, “driveshaft”, differential, and axles into a single package, reducing weight, volume, and eliminates the need for a transmission adaptor plate.
Moves the drivetrain out of the foot well, greatly increasing foot space and virtually eliminating high temperatures in the passenger compartment.
Shifts weight aft, which increases acceleration all without having to increase engine power.
Shifting weight aft also improves braking because the rear weight bias allows the rear tires to contribute more to braking.
Builders must decide what their car is for. A full-up (with driver and fluids) Midlana will weigh 1600-1800 pounds, so it doesn’t take much to make it move, yet many builders will want more.
Summing up a long and contentious topic, I feel that for the street and drag strip, use anything you want; For track day events, well, read on:
Leave it stock:
Advantages: Very reliable and inexpensive
Disadvantages: Dull, boring – “appliance-like” comes to mind – and the car may be slower than desired
The Honda H22A1 engine in my first design (www.kimini.com) was left dead-stock other than intake exhaust, and a KPro-modified ECU. Perhaps because of this, it never once broke and never had to be pulled out of the car. It worked so well with the chassis that ironically, I felt like I needed more, and down the rabbit hole I went with Midlana.
Modifying the engine:
Advantages of more power: Like a supermodel girlfriend, she’s everything hoped for
Disadvantages: Like a supermodel girlfriend, she has hang-ups, is high maintenance, and is expensive
There are two ways to go when modifying an engine, leave it normally-aspirated (NA), or go forced induction (FI). How much additional power over stock will start to steer the discussion.
Normally Aspirated (NA)
Less than ~40% over stock it’s cheaper to stay NA. Making more power with an NA engine happens by getting more air in, more compression, spinning it faster, and getting that exhaust out. “More air in” means a free-flowing intake, a good intake manifold, cams, and a ported head. “High compression” means just that, swapping in higher compression pistons to extract more power. Of course if you’re already in there then you should probably install better rods since the very next item on the list is “spin it faster. To make more power there needs to be more combustion cycles, so figure on spinning the engine up to as much as 30% faster. On the way out, that exhaust will need to see a very well designed exhaust system, with equal-length primaries. Expenses range from several to many thousands depending on the port job, cams, header, and ECU.
Advantages of modest NA modifications: Still fairly reliable and simple
Disadvantages: High compression means it needs better fuel. Where you are and the engine’s compression will dictate fuel choices. In some areas, E85 is widely available and is pretty good for what it is, though it will require a rebuilt fuel system (in short, no aluminum anywhere in the system). Higher output NA engines need low exhaust back pressure, so there’s the triple problem of needing a low-restriction (loud) exhaust, coupled with increased noise due to both the high compression and also the higher rpm. Some road racing tracks have fairly low noise limits (think: 90 dB) which will likely prevent running any high-performance NA car on such a track.
Obviously the closer one moves to that 50%-over-stock line the more expensive it gets. Above 50% and it becomes less clear which way is better to go. Let’s say you “need” to have 100% more power over stock. It’s still possible to obtain this via NA but it’s gets ridiculous for the street; expect to have to wind the engine to around 10,000 rpm (really), run race gas only, and expect that the power band won’t start until you’re somewhere around 6000 rpm. Not good for the street, never mind the ear-splitting noise level. This engine would be great for the drag strip and track events, but terrible for the street.
Forced Induction (FI)
This refers to turbocharging or supercharging; both push more air into the engine, providing more oxygen to be combined with additional fuel in order to produce more power. “In general”, a supercharged engine produces more low-end power, while a turbocharged engine produces more high end power. Which is better depends (it always depends) on what it’ll be used for; for the street, yes, drag racing, sure, and track day events… mmm, read on.
Think of a drag race, but one in which you keep your foot down for 20 minutes. Imagine how hot your engine will get, how will it cope? If your radiator is good for 200 hp, how will it cope with 400 hp? In addition, it’s not as simple as “I’m going to add a turbo today” – to do it right requires an entire redesign:
- All new exhaust
- Water hoses
- Oil hoses
- MAP lines
- Boost controller
- Much longer intake tract
- Far more heat
- Possible engine, ECU, and transmission modifications
- Possibly new MAP sensor
I always wanted to own at least one turbocharged sports car, so I built a Honda K24 outputting 430-500 whp on E85. In early 2016 the threw a rod on-track (after catching to a Porsche GT3 at least!) and the failure left me puzzled about why it happened since it was very overbuilt. I sent pictures of the broken parts to a dozen engine professionals and got a dozen different answers. Some said I detonated it to death, others said it was run lean, some said the mixture was fine and showed no signs of detonation, that a rod bolt broke, that “sometimes stuff just breaks.” It was frustrating because I’d spent the money to essentially build an 800-hp engine and derated it to what I thought would be a reliable 400 hp. On the one hand, I sort of accomplished that because the engine lasted 7 years. The catch is that 7 years isn’t real because the car didn’t run until 3 years ago, and probably doesn’t have more than 4000 miles on it. It was supposedly built for 9300 rpm – I ran it to around 8000. The rods were good to 800 hp, as were the rod bolts and sleeving, yet something still failed at 400 hp. What happened no one will ever know and I’m left wondering about engine v2.0; different parts, yes, but there’s always that not knowing. The experience has been expensive enough that it has me questioning my choices about going forced-induction at all, at least with a 4-cylinder engine. It makes me wonder if I should have:
1. Started with a larger engine right off the bat.
2. Started with a OEM setup with enough power that I wouldn’t have to touch it.
3. Just been happy with less.
The problem with #1 is that large engines are, well, large and heavy and take up more space. Depending upon choice it can alter the car to the point that it causes the project to lose focus (the goal being to create something light and nimble). The problem with #2 is that newer engines are not only more expensive, but many of the cutting-edge units are direct-injection. This may well put you in the position of buying an engine which doesn’t yet have an aftermarket tunable ECU, leaving you hoping that there will be one before you finish the car. Also, many tuners have never worked with direct-injection engines, leaving you to figure it out for yourself – or your tuner may use your engine to train himself on. #3, yeah, well, there is that, just be happy with 200 hp and leave it at that. If I ever build another car, I don’t see myself building another crazy engine from scratch again. For more sensible people this is a moot point – they aren’t interested in crazy power levels and a stock engine will suit them just fine.
For those wanting more, my advice is to go with an engine that’s good enough as-is and truly a case of “do as I say, not as I do.” Note I don’t differentiate between supercharging and turbocharging – from the engine’s point of view, they’re identical in terms of pressurization and produced power.
Summed up, properly converting an NA engine to FI can be very expensive, then once it’s done, you’re never quite sure how reliable it is. Most people who have turbocharged their engines stick to running them on the street or maybe doing a bit of drag racing. For those two cases I think you’ll be fine, but for track use I’m just not sure. I guess I’ll find out, as of this writing engine V2.0 is about ready to start.
Examples: The 2016 Ford Focus RS produces 350 hp and 350 ft-lb of torque from a 2.3 liter turbocharged engine. The 2016 VW Golf R produces 292 hp and 280 ft-lb of torque from a 2 liter turbocharged engine. If I was doing it over again today I’d consider paying a little more up-front for something that makes enough power that it won’t require any modification. That said, buying newish drivetrains isn’t just more expensive, it may also mean buying something that may not have an available – and tunable – ECU. Also, cutting-edge engines are typically direct-injection, a whole new dimension that few tuners currently have little experience with. That’ll improve over time, but if you’re a cutting-edge buyers, either you or the tuner is going to have to learn the new system in order to make it run.
Larger engines are heavier and tend not to rev as high, but are less stressed that smaller engines. They tend to have better low end so that you don’t have to wind them as high.
If you plan to modify the engine, research the transmission to determine whether it will be reliable with the increased power – some are and some are most definitely not. The Honda K-series transaxle is a known weak point when increasing power. Because of the drivetrain’s popularity there are always solutions, but a straight-cut “dog box” will run you about $3500-5000; don’t pretend you won’t need one. Other engine brands may have more robust transaxles so you may be fine without upgrading, but please do your research before going nuts!
If your car will be used solely as a cruiser for leisurely drives along the coast or going to lunch, you can pretty much ignore this section.
For everyone else – regardless how much power your engine makes, exposing it to high-G cornering environment means researching how well it copes with those cornering forces. Not doing so means rolling the dice – maybe it’ll be fine and maybe it won’t. One Locost builder found after driving on twisty roads resulted in “pretty sure the engine’s tost again.” Note that last word, where he destroyed the engine more than once because he didn’t correct the situation
Dry sump discussion and alternatives
People typically consider a dry sump system after their car loses oil pressure in a turn. After seeing the $3-4K price tag however, they instead go with adding an additional quart, running an Accusump, or maybe upgrading the oil pan.
Also, running an engine at high rpm for an extended period whips (“entrains”) air into the oil, resulting in a milkshake-like mixture of as much as 50% air.
In an OEM setup, oil in the pan is picked up by the pump and distributed throughout the engine, with the most important destination being the main bearings. The oil isolates the bearing halves from each other and with pressures of many thousands of pounds, it’s important the two never touch else bearing damage and engine failure are soon to follow. The problem starts with the engine being run at high rpm. Air becomes entrained (mixed) into the oil by the spinning crankshaft to such an degree that it becomes an emulsion, a milkshake-like mixture of oil and air, with air constituting up to as much as a third of the volume (in fact, dry sump tanks are recommended to be filled only to ~60% capacity due to oil foaming potentially filling the rest of the tank). (As an aside, consider adding 30-40% volume to the oil mass, which raises the level enough that it’s now constantly being beaten by the crankshaft, which only exacerbates the problem.) The emulsion is sucked up by the pump and sent to the main bearings, where the normally-incompressible oil film has been contaminated with air. The thousands of pounds of pressure is now able to compress the oil/air down to a dangerously thin layer and greatly increases the chance of bearing damage. Even worse, if and when the pump sucks air, oil pressure drops and the entrained air bubbles expand to about double, effectively doubling the amount air in the oil. This situation of having the oil system contaminated by entrained air cannot be fixed by adding an extra quart or an Accusump, but others disagree. So be it.
What do you do when you’re told by people that a dry sump is a silly idea – not a bad idea, just an unnecessary and expensive addition? Of course, other than cost, these same people also agree that it’s a great idea, so their actual complaint isn’t with what it does, but how much it costs to achieve it. (The irony is that several of those who said so run dry sumps on their cars.) I’m told that there are better ways: “Add an extra quart of oil.”
Yes that works, to a degree, it’s just that no one knows to what degree.
“You don’t need one on a street car.” Define “street car,” and newer Corvettes have dry sumps.
“You don’t have space for the tank.” Says someone who doesn’t own a Midlana… it fits fine.
“Unless the engine’s sucking air, it’s not necessary.” True, until it does, then there’s $$$$ damage which I have to pay for.
– “Get an Accusump, they work practically as good for one tenth the cost.”
This takes a bit longer to explain. I had one and didn’t care for it. It’s a tank of oil that’s pressurized to the same pressure as the engine’s oil system, so an equilibrium is reached where as long as the engine’s oil pressure doesn’t change (up or down), oil flows neither to nor from the tank. The idea is that if oil pressure drops and the now-higher pressure Accusump will push its contents into the engine, “stepping in for” the engine’s failed oil system. I don’t have an issue with the above; it’s the details that bug me. For example, as the car slows for a turn or a stop, engine oil pressure drops and the Accusump starts pushing oil into the sump when it’s not needed, which then gets whipped by the crank. Once the engine starts speeding up, oil pressure rises and oil pump is assumed to have the extra capacity to not only fully lubricate the engine, but also recharge the Accusump tank at the same time. What rubbed me the wrong was the salesman assuring me that their system has a special valve that charges the tank slowly, but releases the oil quickly – a one-way valve. No. It. Doesn’t. Lastly, consider the case where the pump starts picking up air bubbles; they pass through the pump and get compressed along with the oil. Because the air/oil mixture is compressed to standard oil pressure, the oil gauge (and Accusump) will not see any problem, yet the engine is still being starved for oil.