Upgrading Injectors - Question about size

[Grandavi]

I have a Lexus AFM (LIPP) Housing and will just reuse my electronics, but I plan on putting on a 57 trim CT26, 3" exhaust (full from turbo) etc.. (no upgrade to Intercooler yet). Currently running a MKIV Denso fuel pump intank.

I was going to go with 550 cc injectors, but I think I might be better going with 680 cc's.

Just looking for input on that. Also, do I need to go with fuel managment with this? I think that this is a "minimal" upgrade for a bit of increased power on my 7M, so I can probably just live with the Lexus AFM upgrade and the car should run fine using the stock ECU (1988 Toyota Supra - 7MGTE).

Also, I want to do the injectors first, then turbo, exhaust and AFM upgrade after.

 

[Devin LeBlanc]

You need to do the injectors and AFM at the same time, so might as well wait till you have everything to install at the same time. With 550CC Injectors you can get away with a SAFC to tune however with 680CC's you wont be able to pull enough airflow to get the AFR's dialed in and will also being advancing the ignition timing quite a bit which could cause other problems.

The lexus AFM upgrade is made to be matched with 550CC Injectors and a SAFC or similar piggy back to fine tune with.

 

[Grandavi]

So, with a 57 trim turbo, are the 550's sufficient? I can upgrade later, but if I do that, it would probably be a major build for the engine. Just running on a stock 7MGTE with a Cometic HG (very low mileage on rebuild).
Not looking at track performance, just decent pull for the roadways.
But, from your answer I should do the SAFC/AFM/Injectors at the same time. I will be fine for a couple months afterwards with stock turbo/bov/exhaust. (no real performance increase, just prepping the fuel system for it)

Also, the 57 trim + 550's wont over tax the intercooler if I have it all figured out correctly...

 

[Devin LeBlanc]

You will be fine on 550's for anything the 57trim can push out. The stock intercooler will work but you will have a noticeable power gain if you go with a different front mount.

 

[gsxr141]

would 620's be too mush for that setup? i have a set of 560's that actually flowed 620 when tested.

 

[Devin LeBlanc]

What pressure were they tested at? 55? Maybe thats why