Sorry to dash your dreams but this is a project that most experienced mechanics would not attempt. You can plan ahead to set the car out with a "For Sale As Is" sign when you finally give up. Before you go any further, understand a BMW is one of the most expensive cars to repair, and the company is extremely customer-unfriendly. They will not release service information to the public. They won't even release their paint codes to independent body shops. They want all the work to be done only by their dealers.
Since you're still in high school, you probably have an Automotive shop class that you can take. That is a dandy place to start to learn about automotive basics and to get all the additional questions answered that you're going to have. Those classes are not meant to turn you into a mechanic. They are real good at making you a more-informed consumer and to give you enough skills to do some of your car repairs yourself.
If you still want to pursue this nightmare, start by visiting a BMW dealership and see if you can chat with one of the mechanics during their lunch hour. Someone there will know which engines interchange and what modifications you will need to do. Next, start a list of everything you're going to need and the cost. I can start you off with a few things commonly overlooked. One is the Engine Computer. It is designed to work with a specific engine. Chrysler has always been famous for a lot of interchangeability and lots of high performance parts, but with most other brands you're going to need a different Engine Computer and possibly a different wiring harness. If you can find these things in a salvage yard, you'll get them for a fraction of what they cost from the dealership, but you can still expect to pay a few hundred dollars. Since all the computers on the car talk back and forth to each other, you may need to replace some of them and the instrument cluster. One way to determine what won't work is to find out the part numbers for a part used when the car has one engine and the part number for that same part with a different engine. If those two part numbers are different, add the part to your list and find out the cost. With computers, you have to find out if they will work with the same wiring harness or if that has to be changed too.
You want to make this parts list as complete and thorough as possible BEFORE you even buy the car. If you start this project without that list, you're going to be sadly surprised each time something doesn't work and you have to search for more parts, and see those prices. Before you're half done you're going to be convinced you made a mistake, but all that money will already be spent, and all that time you could have been out driving will be wasted.
You can also ask at a salvage yard which parts are different. Look up "Body Computer" for example, in their "Hollander Guide". Those are huge books that assign a short number to every part on the car, then you look up that number in the back of the book, and it will list all the car models and years that part fits. Keep in mind though those books are meant to find a replacement part for your car from a different year or model donor car. They aren't meant to address changing from what the car came from the factory with. From reading trade magazines, you may find someone there who will know what will work for what you're trying to do.
Next, when you install an engine with a different weight, you have to change the front springs to hold that weight up and prevent nose-diving during braking and cornering. The springs are just one part of the suspension system, and this is where that shop class will be useful. Larger engines usually come with bigger tires and a stiffer anti-sway bar. Bigger wheels and tires also present a whole pile of problems that street racers aren't familiar with, but I can assure you, lawyers and insurance investigators know all about it and will use it to their advantage when the other guy runs the red light and hits you. You will end up sitting in the courtroom explaining to the jury if you understand what "scrub radius" is and why you altered it. This is a really big issue with altered ride height too. Lawyers love to find lowered cars and raised trucks because they know they will be able to shift part of the blame for a crash from their client to you.
You may need a larger radiator. You may find the exhaust pipes don't line up to the new engine. If you try to stick in an engine that was never available in that year and model from the manufacturer, things like exhaust pipes and radiator hoses will all be custom fabrications. An exhaust shop can custom-bend pipes, but with no original template to work from, it will all be trial and error, and very expensive. It may be expensive again when pipes rust out and have to be replaced.
Another thing street racers don't think about is the brake system. First of all, the easy one to see is often larger engines come with larger brakes. You can find that out by looking up brake pads or calipers to see if they need to know which engine you have to get you the right parts. Larger brakes will mean the parts those brake parts are bolted to will be different. Now we're talking about spindles and control arms. Simply going to bigger aftermarket brakes is not the answer. Bigger is not better. The front and rear brake systems were very carefully matched when the car was designed. No one is going to do a better job than that. That's why everyone knows any modification is going to result in longer stopping distances under most conditions. There's that lawyer again licking his chops when he sees a picture of your car.
What even the best little street racer boys overlook is the brake hydraulic system. Most cars have a proportioning valve to limit brake fluid pressure to the rear brakes under hard braking. That reduces rear-wheel-lockup and loss of control. There can be dozens of different part numbers for the combination valve, (which contains the proportioning valve), for a given model in just one year. Those valves are carefully tailored for the weight distribution of that car based on optional accessories, engine weight, calculated weight transfer, brake caliper and wheel cylinder diameters, number and location of potential passengers, etc. Changing ride height, tire size, and weight distribution changes the calibration needed for the proportioning valve. No one is ever going to get that right.
I have a few muscle cars of my own, but as a suspension and alignment specialist for almost 30 years, I have every one of my cars set exactly to what the manufacturer specifies.
I can't stress enough how easy it can be to land in court and having blame shifted from the other guy to you just because of these modifications. If you think the lawyers are shysters, ... Well, they are, consider this. If you watch a NASCAR race or a road course race, you will see that almost every car goes exactly the same speed on the straightaways. The winner's car was the one that handled best in the corners. Conversely, that means all the other cars didn't handle as well. The guys who set those cars up are highly-skilled experts who can teach the manufacturers a few things, so why didn't they set those cars up to be faster in the corners? The answer is either they gave up handling and braking in the corner to gain somewhere else, or they couldn't find the right combination of adjustments. Either way, handling was less than ideal. That's what the other guy's lawyer is going to convince the jury of when you didn't even cause the crash.
Also be aware that the awesome braking and handling the street racer children claim to have is an illusion. During high-speed cornering, the body is expected to roll, or lean, from the centrifugal force. While it's doing that, if the outside tire hits a bump in the road, there is still plenty of travel left in the suspension system to allow that movement to take place. Lowered cars are missing most of that travel. The body can't lean in a corner because there's no suspension travel to allow that, so when that tire hits a bump, the suspension system has no choice but to push the body up in that corner. That is not comfortable. Driving 190 mph for a few hours on a racetrack is not very tiring. The reason those guys are beat at the end of a race is they were fighting the steering while being bounced around in the car.
Cars are also expected to have weight shifted to the front during braking. The amount of nose-diving that takes place is factored in when the car is designed. That weight transfer can't fully take place on a lowered car, so while it falsely feels like the car is stopping real well because it stays level, all that weight is staying on the rear wheels with the much smaller brakes. With less weight shifted to the larger brakes on front, those wheels will lock up easier and skid. A skidding tire has no traction or steering control, so, to regain that control, you have to let up on the brake pedal a little. Or, in the words of a lawyer, "you had less stopping power than what the car came with from the factory".
Adding a turbocharger is also a bad idea. Engines that are used with them are designed with a lower compression ratio. One of the few stock engines that can handle that added stress with no modifications is the Chrysler 2.5L from the early to mid '90s, but even those will not last as a daily driver. That engine has had things added to it to get it up to 500 horsepower, but only to show what it was capable of. Chrysler never meant for people to add turbos and nitrous to stock engines.
A local shop is working on a newer Mustang right now that the owner added a turbo to. He destroyed the crankshaft and pistons within a few thousand miles. That engine was already near the limits if what it could withstand before the turbo was added.
With the little experience I've had building cars for the race track, and the huge amount of experience I have with steering, suspension, and alignment, and brakes, please learn from my 20 / 20 hindsight and many mistakes, and train for a career you enjoy, get a good job, and go out and buy the car you want. Once you learn more about them, you can consider rebuilding a project car, but don't make it your daily driver or only car.
Friday, January 10th, 2014 AT 1:25 AM