question on boost and injectors

[troubled4g64t]

okay so basic break down I'm about to start the tear down and rebuild but the basics are 01 4g64 9.0 factory comp. doing the Kia head swap over sized valves evo intake manifold t3/t4 turbo

Now what I'm asking is how much boost will I need to bring me up to factory comp. ratio I know w/ the head swap I end up about 8.0:1 roughly since it will be a little while till I find a place to get this tuned at I just want to run enough boost to bring me around stock or just over that way I don't have to change the injectors till its time for tuning.

[03-Galant-ES]

you will still have to change injectors, cause your air to fuel will be off not based on compression, but based on volume. The stock injectors wont be able to pump enough fuel into the engine.

[troubled4g64t]

I have read about guys running 7 pounds on stock just fine but thats kind of the prob there are quite a few shops to tune but its hard to look in to which to use since I dont trust shops they charge to much for doing jack shit I just want to run about 5 pounds or so give me plenty of low end and good top end till I get it tuned and the oem injectors are not running at the 85% max even at wot stock they only run about 60% max duty so I still should have 25% to play with but what boost range does that put me in

[03-Galant-ES]

Im not sure about range, but our stock ecu also wont read over 100% I believe so if you piggy back it you can load in roms to the evo ecu and it will be a basic tune for a basic build. Honestly to wait until you can do it right is best, buy the extra couple hundred in parts you need and run a nice 8psi tune on stock block.

If you are trying to take shortcuts then it isnt worth it you will probably end up breaking your car. I almost took short cuts, but I decided to wait for now with turbo, exhaust, 5spd, brakes, fuel pump, fuel rain, all that shit sitting in my garage.

[Poison457]

I have read about guys running 7 pounds on stock just fine but thats kind of the prob there are quite a few shops to tune but its hard to look in to which to use since I dont trust shops they charge to much for doing jack shit I just want to run about 5 pounds or so give me plenty of low end and good top end till I get it tuned and the oem injectors are not running at the 85% max even at wot stock they only run about 60% max duty so I still should have 25% to play with but what boost range does that put me in




Seriously don't run stock injector's even if their only running 60% duty, well the max is still only what 225/250cc's? that's not even good for 5psi, and lets not even get started on that combined with the fuel pump, you'll need at least the walbro 255 to run any kind of boost. A wooden nickle worth of free advice buy second hand but do it right the first time, i set of used 550's won't run you more than a C-note on e-bay and a good portion of the time you'll even get the resistor box with it.

When you read about people running boost on stock, it means stock internals IE stock rods,stock pistons,stock valve train...ect

will your engine hold on up to 5psi i would say more than likely it will, will your fuel delivery? absolutely not

[03-Galant-ES]

Or you can get 440cc WRX injectors and you dont need resistor packs.

[SPD_FRK]

If you are seriously going to boost the engine, 4-8psi even your stock fuel system will not work. You will run very lean under boost (even that low of PSI), this means that engine even if tuned still won't make it very far/long at all. You are forcing more air into the combustion chamber and this requires more fuel. A lot of places that tune will also tune for a rich mixture under high boost to prevent knock.

You really need to talk to your tuner and find out how they tune vehicles that are boosted, but most importantly you need to get all of the vital engine components before you boost.

The WRX injectors are a great option because they are large enough to support a low and moderate amount of boost, yet if you go for higher boost numbers those injectors can be modified to flow in excess of 500-600cc.

[troubled4g64t]

look let me explain the motor will be fully built when it goes in I don't know any good tuners locally and getting injectors is not the prob. what is the prob is that I'm affriad of putting in say 440 injectors running low boost and running like shit till i get it tuned I have over a G in to my kia head rebuilt bottom end w/ all arp studs And new gaskets etc.
like i said the new comp. ratio is to low for normal driving w/ out the turbo so I just need to make it comparable to factory till the tune I'm not talking about leaveing it this way permanetly I only mean a few weeks and It won't be daily driven, correction really driven at all till the tune but I may have to drive 50+ miles to the shop for the tune does this make it more clear I am talking like 2-4 pounds and I dont mean driving like I stole it

[SPD_FRK]

look let me explain the motor will be fully built when it goes in I don't know any good tuners locally and getting injectors is not the prob. what is the prob is that I'm affriad of putting in say 440 injectors running low boost and running like shit till i get it tuned I have over a G in to my kia head rebuilt bottom end w/ all arp studs And new gaskets etc.
like i said the new comp. ratio is to low for normal driving w/ out the turbo so I just need to make it comparable to factory till the tune I'm not talking about leaveing it this way permanetly I only mean a few weeks and It won't be daily driven, correction really driven at all till the tune but I may have to drive 50+ miles to the shop for the tune does this make it more clear I am talking like 2-4 pounds and I dont mean driving like I stole it
Ok let me explain the basics here for you.

If your CR (Compression Ratio) is 8.0: or 8.5:1 you cannot change the CR unless you change the pistons. This is the ONLY way you are going to make the compression "comparable to stock." No tuning or setting of the boost pressures is going to change your CR...Period.

If you put a turbo on the car, regardless of the CR it HAS to be tuned or it will;
A - run like shit
B - Run too lean or rich
C - Have knock like no other
D - Ultimately kill (read blow up) your engine completely.


There is a very good, and very specific reason why people tell others to do their homework, and do it right the first time when it comes to going turbo. You can't just put parts together and slap them on the engine without tuning...you just can't...well you could but see "D" above.

If you have $1K into the head swap, be smart and do it right or don't do anything at all. If you don't take the advice that has been explained and given to you, refer back to "D" and be sure to share pictures of the hole in the block, bent rods, valves and everything else that is pretty much 100% gaurenteed to happen if you choose to ignore the guidance