The Basics
-What's an IDI engine?
--IDI stands for InDirect Injection, it is a diesel engine which directly injects diesel fuel into the cylinder, via a high pressure injector to a pre-cup.
-Why Hot Rod a IDI?
--I admit, there are other engines which are simpler to hot rod. Even other diesels which are simpler to hot rod. But if you're reading this, you probably know the answer already. Because it's fun. It turns heads. And because it's relatively simple compared to modern passenger diesels.
-Getting Started
--While IDI's are internal combustion, piston engines and thus share many of the same parts as petrol engines, there are some key differences you should know about before jumping into tuning your IDI.
Diesel engines do not use external sources of ignition, they are compression ignition engines, meaning that air is compressed into such a small space that when fuel is injected it cause the mixture to ignite. Because of this, temperature is very important to an IDI tuner. You see, in order to auto-ignite a fuel-air mixture the air must be compressed into a space roughly 20 times smaller then it's original area during the compression stroke, the addition of fuel to this air causes quite a bit of heat to be generated. In turn creating very hot exhuast tempuratures, often in excess of several hundred degrees celsius. If a inadequate part is used to make any part of the exhaust, the part runs the risk of being severely damaged. Turbo's are especially susceptable to this kind of damage, it's refered to as a melt down, and the turbo will fail do to a relative melting of the blades. However, almost all turbo's approved for use on a diesel engine should with stand your average exhuast temp. and a few hundred degrees above.
In short, you should know your vehicle, and research your parts before modifying.
All internal combustion engines act as air pumps. Basically they intake air and expell air. Armed with this knoledge know that cold air is especially important to a diesel. The colder the air the more air will be able to get into the cylinders, resulting in better oxidation of fuel and a more powerful stroke. This is the thing to keep in mind while tuning your IDI, the more cold air, the better.
-Fueling
--Just like in a petrol engine, the amount of fuel being delivered is vital to the amount of horsepower being put out by the engine. One thing you don't have to worry about, is running lean. A diesel engine can run extremely lean and there will be no damage to the engine whatsoever.
How do we up the delivry in a an IDI? There are a few ways.
---The Pump. This is the most basic upgrade you can do to your IDI, it requires no parts, and only a few tools. All IDI's that use the Bosch VE pump can be manually adjusted via a screw just below the throttle, at the top of the pump body. From the factory there is a stop welded on to the top of the screw, this keeps the valve in the pump open a certain angle to allow fuel in. If you want to open the the valve further, you will need to remove the stop. I suggest using a die grinder. Once the stop has been ground off you can move the screw by loosening the nut at the left end of the screw. Once you've adjusted it, tighten the nut. Thats it. :)
Advancing the pump as mentioned can be tricky busines, it will require constantly starting your car, revving the engine (to see how much smoke your putting out) and then shutting off again, adjusting... so on. But it is an easy way to pick up horses and torque. and a good place for beginners to start.
-Air
--Like previously said, a internal combustion engine is an air pump. And the more cold air you can get into it, the better. There are 2 ways to get more air into the engine.
---Natural Aspiration. In short, this is the tuning of proper intakes , cams, and gaskets. But for the IDI we cut out about 75% of the usual NA tuning procedure. Why? The IDI compresses air at a 23:1 ratio (roughly 483psi, with a wear limit of about 398psi), so increasing compression is not really necassary. What you can do is make a set of cold air intake's. Let's walk through the process.
The factory intake is hardly adequate for a hot rod. It's a snorkel the sucks in air from about 5" away from the intake manifold. Hot, engine air. Not the kind of air an IDI likes. The kind of air you want is cold, straight from the front of the car. Your going to need some parts to make this happen, so here goes: 2 4"-3" air-duct adapters, 1 4" diameter dryer hose roughly 5 feet, 2 4" hose clamps.
The above parts can be bought from any hardware store and cost a total of roughly 12 dollars.
You will need some tools too, a 3" hole saw and some caulking glue. Got em? Here's how to assemble, step by step:
1. we will need to detach the top of the air-box from the intake manifold. Simply flip back the metal straps on either side of the box, and pull up. Now take out the panel air filter, and remove the snorkel from the side of the airbox with a phillips screwdriver.
2. Now we need to mark the hole for our hose adapter. Since there is already a 1.5" hole in the side of the box we will make it bigger. Take your 3"-4" adapter and place it over the existing hole, make sure no part of the adapter is over any edge of the box. Now use a brightly colored marker and mark your new outline, make sure to mark dead center of the pattern otherwise you won't know where to put the pilot bit of the hole saw.
3.Cut your hole. Make sure its even, and does not have any overjagged edges. We want the 3" end of the adapter to fit in there.
4.You will ned to whip out your caulking gun and glue the 3" end of one of the 3"-4" adapters into your newly made hole. you should glue both sides of the adapter (being insde and outside the box) to make sure it holds. Now let the caulking cure for a day. Curing is important, you want a good seal so don't get ahead of yourself and skip the curing process.
5.Put it all together. Put your filter back in the air box, and the airbox back on the manifold. Clamp it down tight. Now it's time to assemble the the intake itself. Simply attach one end of the dryer ducting to the air box you've just made, clamp it down with the hose clamp so it doesn't come off. Now run your hose to the front of the engine compartment, make sure the place you have put it is getting a cold air. Behind the radiator is generally a bad idea, since the air coming out of it is hot. Behind the head lights is always good, and running it to street level can have it's advantages as well (in this case, DO NOT go below the tranny, sucking up rocks is no fun). Now your probably asking "why did I get a second 3"-4" adaptor?" for a cone filter silly! You will get the best performance from your new intake by slapping a 3" conefilter on the begining of the intake. this way you can dispose of the crappy panel filter all together and keep the intake clear of unwanted blackages like rocks, and anything else that might bounce up there. Your typical cone filter cost about 26 dollars from most autoparts stores. You will want one that is high flow, and high quality. K&N makes good filters, so does Vibrant. But there are a variety of filters to choose from so get one that you are comfortable with.
---Exhuast. It's no good to have a badass turbo, or a super hi flow cold air intake, if the air can't get out of the cylinder smoothly and quickly. If your driving an early model IDI, you will probably have a very simple exhuast. A header, a flex pipe, a front muffler, a pipe, and a rear muffler. Notice there is no catalytic converter. All in all the widest part of the exhuast is about 1.5" in diameter. To promote the smooth flow of exhuast gases you will need to do away with the entire stock exhuast. Unless you have the equipment to do your own exhuast, you will have to take it to a muffler shop. I suggest replacing the stock exhuast with a 2.5" straight pipe ending in a nice turbo muffler. Make sure you have a flexpipe between the down-pipe and the the rest of the exhuast. if one is not installed the torque of the engine will tear the pipe free. resulting in a loud bang. There are other exhuasts available, but you will want one that is not to skinny, and not to fat. If the exhuast is to wide air will become stagnant in the pipes, and you will lose performance. If the pipe is to skinny you will restrict the breathing resulting in a loss of highend power.
---Turbo. A turbo Charger is almost always the solution to your diesel horsepower needs. Below is a link to a Turbo tuning how-to for A2 VW diesels. This should help for starters. More to come.
http://babelfish.altavista.com/babelfish/urltrurl?url=http%3A%2F%2Fwww.vwquebec.ca%2Fforum%2Fviewtopic.php%3Ft%3D4344&lp=fr_en&tt=url
|
