boosting an old 4 cyl engine

[derya kongul]

hi everyone
i have an very old 1.6 8v 4cyl carb engine in my car. As NA it produces around 80hp at crank. My plan is boosting it. I kinda sorted out pistons rings rods gaskets etc, not made any purchase though. (In turkey you cant swap other engines its illegal) My problem is because it is an old engine it does not have any sensors on it. İ thought about going efi but how am i going to put sensors on my engine or should i go preturbo carb? If i go preturbo carb will it be laggy? So many questions in my mind not enough knowledge to answer them. Im good with my hands though welding etc. So if someone can help me out i would appericiate that. Here is a pic of the engine (not mine just an example)
Edit: BTW it is a pushrod 4cyl 8valve engine

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[Nicholas Clark]

First of all, allow me to welcome you to the ETCG forum, as I can see you are new here! (2nd Post) I would like to say that I already learned from you that doing engine swaps in Turkey is illegal. In America you can usually swap what you want as long as it passes emissions testing. And even then, the emissions testing is only in certain areas. There are areas in the US like where I live where there are no laws whatsoever regarding engine swaps.

On to the meat of the questions here. . . When you have a blow through carb it has to be specially made for that application. Because with a carb you will have the pressure from the turbo going into the fuel bowls. That means you have to have a boost referenced fuel system. Carbed engines usually run on 8 pounds of fuel pressure. If you have 8 pounds of boost, that pushes back into the fuel line, and you will have no fuel pressure. So you will need to up the fuel pressure if you run a blow through carb or at full boost you will run out of fuel, lean the engine out, and possibly hurt the motor.

Going to EFI is a real possibility. In America we have a lot of aftermarket companies that make EFI for older cars. It’s pretty common to convert here. They have all the sensors essentially contained in one unit, and they are convenient, but they are not cheap. The only sensor you would really need is an Air/Fuel sensor. That would make sure you keep the proper ratio and not hurt the motor. Something between 11.5 and 13 is about right. Although 12.5 is optimal.

Usually carbs before the turbo can be good for cooling the intake charge, but are fairly unresponsive and laggy. I am not saying it can’t be done well, but it’s more difficult to pull off.

When it comes to modifying cars, there’s almost no limit to the amount of learning you can do. I hope this helps.

[derya kongul]

@Hockeyclark thank for your reply clark. yeah im a newbie here 🙂 my first post was an introducing myself post anyways. I actually do not like blowthrough carbs even with raising fuel pressure system carbs might act badly.and i believe efi needs crank sensor minimum. is there a cheap way for me to put a crank sensor in? fuel pressure water temp AFR are the easy ones my problem and concern is with crank and camshaft sensors. If i go preturbo carb i am thinking about putting the turbo as close to the head possible and put the carb directly on it.because exhaust and intake manifolds are in the same side runs will be VERY short. The unresponsiveness and lag freaks me out too that is the only reason i havent done it yet. will the close proximity between carb-turbo-head reduce the lag?

[Nicholas Clark]

I don’t know how hot it gets in Turkey, but if it gets really hot, you could get detonation in the turbo if you have the carb before the turbo. Rare, but possible. Usually the fuel will cool the intake charge, and detonation will not be the problem. If you make all the piping really short, it will be less laggy for sure.

Remember, it’s your car. So do what you want.

[dan]

Hockeyclark hit the nail right on the head with this one.

If you boost a engine there are several things you need to take into consideration.

1 can the fuel system take it? more air in the system means it needs more fuel, ideally a 14.7-1 air fuel ratio is best for efficiency, for power a 12.7-1 a little on the rich side helps prevent spark knock as the extra evaporating fuel helps decrease internal combustion chamber temps, and as Hockeyclark already stated, when you have a carby engine, that poses a special set of issues because a carburetor works on the principal of using “vacuum.” by drawing fuel out of a bowl through a jet to atomize the fuel. in order for it to work the boost pressure will also have to pressurize the fuel bowl, and as stated if you exceed the pressure of the fuel pump or get close too it via boost pressure, you can run your engine lean at higher revs and watch it go bang!

2 can the cooling system take the extra heat? When you add more power to a engine it is going to create more heat energy as a result, increased dynamic compression results in higher pressures in the combustion chamber meaning more heat, more friction due to harder pressure on moving parts means more heat, and increased combustion makes more heat.

3 can the engines gaskets and seals take the pressure? the whole “blow the welds off your intake.” joke isn’t too far off, can the intake manifold gaskets support boost pressure? and most of all what about the head gaskets? how about the piston rings?

4 is the engine tuned for it? you can run a old mechanical engine off turbo its been done thousands of times before, but you have to tune the engine for it, the ignition, the carburetor, typically a boosted engine requires a little bit more retarded ignition and a bigger set of jets to allow more fuel to pass through the carby. For computerized cars a PCM must be able to recognize boost and make adjustments to ignition timing and air fuel mixture accordingly! if it can’t best case scenario your car runs like crap, worst case scenario your cars engine blows a piston out the side of the engine.

5 can the mechanicals take the extra power? this happens all the time in the 3800 community, guy isn’t happy with the smaller supercharger pulleys anymore, goes with a turbo for more boost! but he has the stock L-26 bottom end rather than a L-32 OR L-67 bottom end with the thicker con rods… throws a connecting rod because it can’t take the increased force of the piston being pushed down… and BLAM or at the very least ends up with a bad case of rod knock which to me is a sound comparable to taking your finger nails and scraping them across a chalk board, what will hurt worse is your wallet afterwards.

[Author]

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