Turbo on the SUPER cheap.

So let's say I want to add a bit of power to inline 4 motor.  I really don't care about longevity but I don't want to blow it up on the first pass.

I found a new chinesium turbo of unknown (but small) size on marketplace for a whopping $65.   How exactly would I go about mating it to my BMW 318?  Would the computer be able to keep up with just a bit of boost (say 4-5 psi) without spending money on fueling/tuning/etc?

Learn me the ways of SUPER cheap boost please.

You'll have to adjust the fuel somehow, even at that low boost level.

I guess you could go 1990s-stylee with an adjustable rate fuel pressure regulator if your fuel system has any headroom, but you've got to do something other than admire the fresh block vents .

I would imagine you could go even cheap with a junkyard turbo setup, using everything from a volvo.

As far as the ECU handling low boost....over my head.

You'll need an adjustable fuel pressure regulator, easy to package an aftermarket one. That will increase base fuel pressure based on boost, and should get you enough fuel for LOW boost. Any more than 5-6psi and you'll need bigger injectors and pump.

ECU will not know what's going on, unless you reprogram it.  It only has a MAF for airflow measurement that then controls fuel based on that.  You may start maxing out the stock mapping tables in the airflow range, and as for timing it won't know to run lower timing in positive manifold pressure.  It will basically run at the max ends of the tables for fuel and spark, and you'll likely get some knock. Absolutely crucial to use at minimum 93 Octane fuel, maybe even with octane booster to avoid engine damaging levels of knock.

You'll also need to figure out oil feed and drain lines. 

Other than that, it's a simple fabrication job

In terms of the install w/o tuning- that's kind of a tough one.

If you are talking a car that uses speed-density- which means there's a MAP sensor measuring the air- check and see if you get to atmospheric pressure at WOT.  If you do, then you can't boost it.  If you don't, then you can boost it up to that.  Pretty much all pressure sensors are either limited at 1bar absolute (atmospheric pressure) 2 or 3 bar absolute.  And OEMs are cheap bastards, so for a non turbo, the limit will be 1 bar.

MAF cars are different- I have never seen a MAF car that actually uses the full range of the MAF sensor.  So, in theory, you can run the boost right up to the MAF limit, and it will be reasonably well done.  For the most part, the injector limits are normally quite close to the MAF limit- so, in theory, you can run the injectors unmodified, too.  You do want to change to a raising rate pressure regulator- as the injection is totally calibrated on a fixed pressure drop across the fuel injector.  Which gets a little complicated for non-return systems....

For the most part, you should be able to boost to a couple of PSI on a MAF car, and it will deal with it reasonably well- all the tables are calibrated to a load of 1, and that rarely happens on an NA application- so if you can record the OBD signals, and get load- that's where you want to stop boosting- anything over a load of 1 - the ECU is cutting off the data change at 1, so it's purely guessing.

In terms of the amount of fuel- so very many cars over fuel so keep the components safe, with light boost, you should still be good to go.  That works more for post '96 cars than before, as I've heard of more than one OEM that went lean to lower exhaust temps.  Which sounds nuts, but it sort of works.

This is relevant to my interests. In for the info.

You also will need a wideband and controller for it. And gauge. If you keep the engine happy, the Ecu doesn't care. That said, you'll not get far on Boost before the stock injectors run out. Changing them out helps. 
The Ecu can only remove so much timing  

the biggest hurdle I found was sourcing a wastegate spring that will go low enough. Lowest I ever found was 6psi, and that was too much for my 22re. The eBay turbos comes with some dubious spring set for like 7psi. 
 

On a positive note- I condone this. Post back ideas. Oh, and make sure you put it on YouTube so the haters out there can understand. 

In typical GRM fashion I'll give an alternative suggestion. Instead of turbo what about slapping a supercharger from a Mercedes C230 on there? Will probably live longer than the cheap turbos and deliver the low boost levels you're after.

In reply to clutchsmoke :

Actually I'd considered that exact thing. 

In reply to KyAllroad (Jeremy) :

Let me help enable you. 

Is this an M10 or M42?  I'm not sure how well mechanical FI will take boost unless you source some 2002 turbo fuel bits.

Something that was suggested to me at one point, but I have not looked into: Grounding the ECU coolant temp signal. Supposedly that will make the ECU think it is cold all the time, and dump extra fuel in. Similar to others, likely only good for 6psi or less.

Again, I do not know if this is a legitimate thing. I imagine it would have some downsides, and might not run the best. I'm curious to see if anyone else has heard of this idea.

Install just fuel nozzle for a nitrous kit and then boost reference the switch. When the manifold goes from vacuum to pressure, start spraying fuel into the intake. Even get some charge cooling from the fuel vaporization. Runs too lean, crank up the pressure regulator. No clue if this would work or not. It would be plenty janky even if it did

Re wastegate springs: My ebay GT15 I used on the boost beetle was set for a claimed 14psi and I had zero luck finding one cheaply for the 7-8 psi I wanted. I went full redneck and added a helper spring externally. Took some experimenting to find the right spring to use but in the end it worked really well. Right up until the turbo blew is oil seals out.

Cant you pull the thermostat to trick it into running richer?

The modifying the engine temp to run rich is an old wives tale.  Unless we are talking a very old car with a very basic fuel injection set up, cars will be running stoich almost immediately- from 7 seconds up to maybe 30 seconds for cars older than 1995 and newer than Motronic/EEC IV era (roughly 88-90).  

Don't bother modifying the engine temp signal or the T-stat.  That won't change anything.

Why no mention of the cheapy Eatons off the 3800's?  Plus the APR discussed earlier.  it probably isn't hard to find bigger injectors but not sure what level of ECU hacking would be needed to change maps.

clutchsmoke said:

In typical GRM fashion I'll give an alternative suggestion. Instead of turbo what about slapping a supercharger from a Mercedes C230 on there? Will probably live longer than the cheap turbos and deliver the low boost levels you're after.

While I love superchargers, realize that mounting one is really a skill.  It has to be square and true to the crankshaft or you will throw belts.  It has to be in exact line with the groove(s) that drive the belt  or the belts burn up. 
The sum total of the length belt required has to be available for some common use or you will be waiting for them to make a run of belts that size.  
and it has to have access to intake and pressure. 
then there are things like fenders and hood etc. that the whole package has to clear.  
Finally your fabrication skill  will be exposed for all to see whenever you open your hood.  Jerks will love to criticize anything or offer alternative suggestions.  Knowledgeable people will realize at a glance any shortcuts or mistakes. Loudmouths will tell you what else you should of, could have, must do. 

In reply to KyAllroad (Jeremy) :

I did it on a 1975 Jaguar but it really wasn't right.  I tricked using the adjustable fuel pressure regulator to trigger the cold start injector to come on at 2 psi. And adjusted the pressure regulators to run rich.  
The only reason I got away with it is Champion  used to make gold palladium spark plugs. 

alfadriver said:

The modifying the engine temp to run rich is an old wives tale.  Unless we are talking a very old car with a very basic fuel injection set up, cars will be running stoich almost immediately- from 7 seconds up to maybe 30 seconds for cars older than 1995 and newer than Motronic/EEC IV era (roughly 88-90).  

Don't bother modifying the engine temp signal or the T-stat.  That won't change anything.

Coolant temp sensor mod works with OBD1 and some early OBD ll cars. I've used a pressure switch (and in some cases 2 staggered) with a linear 5-10K pot to adjust the amount of fuel needed and run up to 25 psi with this kind of setup. I've also run (and seen run) on MAP cars up to 4-6 psi on a completely stock setup. Some will do it, some won't. The only problem with the CTS mod is that it doesn't always work well at part throttle/very small turbo applications so Ive scabbed in an extra injector or used the cold start injector to add fuel.

I built some adjustable 555 timer based extra injector controllers that used RPM as the input and boost reference for fuel pressure output and they worked well, but the proper ones will also use a load (MAP) sensor as well.

In reply to Suprf1y :

I can't think of an OBDII car that I've worked on where the coolant temp mod would change anything related to desired a/f.  But if people want to try it, go for it.  

Like I mentioned about MAP cars- it's more about the range left in the sensor more than anything else.  If there are cars out there where WOT is not actually atmospheric, well, you can boost that.

Turbo of choice, log manifold made from stainless steel Weld-Els and cut up header (or make your own flange using an exhaust manifold gasket as a pattern on a piece of flat steel plate), turbo flange ordered online (make sure it matches the turbo of choice).

temporarily mount turbo in engine bay approximately where it fits best.  Use steel strapping/angle/wood to hold it approximately in place.  If it has an external wastegate, then you'll need to make room for it and its flange.  If its internally controlled, then you should be fine.

Start cutting and fitting turbo manifold parts in the engine bay, when you get it close, start tacking it together until it is close enough to remove and weld it completely.  Test fit a few times, then have the flange faces cut flat and if its a long term plan, ceramic coat it inside and out.

Install turbo oil feed line (tap it from an oil pressure sender or similar) and mount drain line so that it runs at a 45 degree angle to above the oil level in the oil pan/engine.

Use aluminum tubing/connectors for the air intake/boost outlet to the intercooler/intake.  Add lips on the tubing with modified pair of vise grips.  Get tubing and connectors from cast off "cold air kits" and similar.

As for fueling the engine, honestly there are hacks as described (cold start injector controlled via hobbs pressure switch and a relay for example), but controlling the fuel is only one piece as you also generally need to retard the timing as well.  I really would install an MS1 (because its cheap, there's one for $110 on the board), add Extra code and control the fuel and ignition plus the turbo wastegate.  Done.  It isn't the latest and greatest and it has its limitations, but its a known quantity and for this situation it will work.

Or a speeduino. Those things are like $150 for the basics of programmable Ecu. 

Before buying an aftermarket ECU, see if the BMW one can be tuned open source.  Several of them can.  And if you don;t have one that can, see if the harness mates to one that you can, because then you are only $40 at a U-Pull-It away from a tuneable solution.

Rising rate fuel pressure regulator and retard the base timing, assuming it's a fairly stupid ECU. Crude but it actually kinda works. I don't know how old this 318 is. If there's any headroom in the injectors, a piggyback such as our Voodoo Box is a bit slicker.

Keep in mind that if you pull the stock ECU, you are now responsible for EVERYTHING. Cold start, AC compensation, tip-in behaviour - all that stuff is actually pretty hard but is ignored by most people and as a result there are a lot of MS cars that run like crap. With this boost level, work with the stock ECU if at all possible.