Injector size for rebuilt engine with a 68HTA???

[Macurts]

Lookin to see what size injectors i need for my motor (4G63)...i bought the new FP 68HTA they got out and don't have anything else upgraded fuel wise. DSMlink is on the way as well just lookin for some advice

 

[jrohner]

Gas or E85? What are your goals?

The price doesn't go up much for bigger injectors, so get a decent size right away so you're not upgrading them next year.

 

[5150DSM]

There is a simple formula for sizing injectors:

HP X BSFC/#of injectors X max duty cycle

For example: You are looking for 425 hp from your turbo(roughly) BSFC(Brake Specific Fuel Consumption) Typically, .60-.65 for a turbo motor, you have 4 injectors and should be looking for a max duty cycle of 80-85%(.80-.85) So...
425 x .65 = 276.25 while 4/.80 = 3.2 so using the formula 276.25/3.2 = 86.33 x 10.50 = 906 cc/min

The above formula should put you in the ballpark. Sizing your injectors somewhat larger than the formula is always a good rule of thumb as it gives you some wiggle room in case of an overboost. Also, consider your future goals, if this is the last turbo you are putting on the car go with 650's; if you plan on going bigger in the future you may want to size up.

 

[e85_4g63]

The stock 14b turbo can max out EVO 8 injectors (a tad smaller then 580's) and there is no way your getting 425hp from it.

My 2 cents is the 68hta needs to be used with a minimum of 750cc injectors on the low end even with straight pump gas.