Turbocharging/tuning help (injectors, tuners, etc)

[Christine_4.0xlt]

So here we are ladies and gentlemen, I'm tired of earth shattering 160ish hp that my 4.0 ohv struggles to make and I'm seriously considering turboing the old girl. I've already pretty much decided on how I'm going about it and most of the details but I keep stumbling over the tuning aspect. I know I'll probably have to get a tuner (been looking at SCTs products) but some people say the stock 19lbs injectors are ok with a tune, some say 24lbs injectors AND tune are better, and some say injectors alone are ok. I'm not used to tuning a gas engine let alone a newer efi one. I'm pretty much ok with whatever I have to do i just want to make sure I'm doing it the correct way

Thanks in advance

 

[adsm08]

If you want to run any significant amount of boost I'd get bigger injectors. Running lean is bad. Running lean on boost burns holes in pistons. A great way to do that is having injectors that can't keep up with demand.

Take a look at supercharging too. It done more on the 4.0, and you may be able to find someone selling a complete set of the stuff you would need.

 

[Curious Hound]

I think ran across some info a while back that had a formula to calculate injector size. You could google that. Injector size is based on how much air you're putting through the engine. You need a certain amount of fuel to keep the fuel-air ratio correct. The injectors are open a certain amount of time per cycle, calculated by the engine based on load, row, air mass, etc. So if the injectors are too small, the ecu will be trying to keep them open too long to get the right amount of fuel in. If it has them open 100% of the time and needs more fuel, you go lean. On the other hand, if they're too big, you have rich conditions at low rpm/ low load. There is some fiddle room in the numbers. But you want to get it close. Displacement, boost pressure, fuel pressure, etc. Are all key factors.

(This description is very simplified and maybe not perfectly accurate. But that's the general idea.)

 

[Christine_4.0xlt]

If you want to run any significant amount of boost I'd get bigger injectors. Running lean is bad. Running lean on boost burns holes in pistons. A great way to do that is having injectors that can't keep up with demand.

Take a look at supercharging too. It done more on the 4.0, and you may be able to find someone selling a complete set of the stuff you would need.

That makes sense, I guess the next step is to find a good set. Ive been told 24lbs injectors are about right for mild boost (I dont intend to push more than 8psi to start, sounds lame I know but its a start and a safe place to start).

And I did look into supercharging awhile back but some if the kits were upwards of $3500-$4500, whereas the turbo im looking at is roughly $325ish, and tuner is about the same. Its a budget thing more than anything

 

[adsm08]

And I did look into supercharging awhile back but some if the kits were upwards of $3500-$4500, whereas the turbo im looking at is roughly $325ish, and tuner is about the same. Its a budget thing more than anything

Yes, new. A few months ago there was a full supercharging kit for sale, blower included, on here for $1500.

Now your turbo itself is $325. You need manifolds and pipes to mount it up, and intercooler, pipes to handle the air, unless you can custom fab the stuff yourself that is going to add up quick.

 

[sgtsandman]

It also depends on what you want the boost for. Super chargers are great for low end grunt. Turbos are better for when you are already rolling and have some RPM.

Of course, you could always turbo super charge it and have the best of both worlds!

 

[MikeG]

One (or more) of RonD's posts addresses injector flow rates.

If I remember correctly..... divide horsepower in half, to get pounds of gasoline per hour. Eg. 160 HP, divide by two, 80 pounds. Divide by # of cylinders to get injector flow rate needed (max). 80 / 6cyl = 13.333...... and so on (so round up to next size injector, use 14 lb/hr for a 4.0 OHV as an example).

Whether or not that changes with boost, I don't know. Hopefully I put it correctly.