[DigitalDUST]

I found a deal with a friend who works at a performance shop in arkansas and says that he could get me 780cc for just $300 and was asking me if my S-AFC 5 knob by apexi will handle that much fuel??

and will walbro 255lph work with 780cc injector along with cartech afpr? will it work?

just questions of precautions. because Im about to buy 780cc's rather than 550cc's bec my goal is 700rwhp and i dont want to buy another injectors after 550cc's u know what I mean..

 

[MKIIISupraGuy]

the old school afc might run out of adjustabilty...

as it is i'm at -22% max. if i ran afpr and bumped up fuel pressure, i'd have to lean out even more. max is +/- 30%.

i'm running 550's btw.

 

[DigitalDUST]

how is that possible?

how can it run out of adjustablity? if it only tunes the amount of fuel on each rpm ranges.. if it was an old school one. which AFC should I get for 780 cc injectors then???

 

[X-man]

Either the second generation or third of the afc will do up to +/-50%.

 

[DigitalDUST]

I see..

so I need to find an fuel mangement that will do an +/- 50% tuning


so u are saying my 5 knob apexi SAFC is up to +/- 30% ??

 

[ZaZZn]

turn ur fuel pressure down and you should be ok.. have base at around 25 psi?

 

[Rajunz]

Yeah, if you turn down the fuel pressure and cranked down the SAFC. But damn, 780's are way too much for what you're running. How long do you plan on running like this?

 

[DigitalDUST]

well I wanted to upgrade the turbo later on. dont want to waste the money on changing the injectors again.

with the 60-1 I could easily boost up to 28 psi so thats alot more fuel than the 550 could handle.

what would happen to the engine if I use 780cc's??

I dont know how long but I'd say propably an year or so. is that bad?

 

[X-man]

You can support safely 480 to 490 to the ground on 550's, push the envelope and 520 to 550 could be done and has been done. Larry from Sound Performance did 600 to the ground on a MKIV on 550's. 680's could easily be supported on you 5 knob afc and with the right pump will push well into the 600's to the ground. 780's are around 30% bigger than the 550's where as 680's are about 19% bigger so it could be done but you still might run to rich.

 

[dbsupra]

and dont forget when you start pulling a lot of fuel out on a s-afc 1st gen, 2nd gen or whatever your timing is gonna be way advanced. just somethin to keep in mind.

dave

 

[X-man]

and dont forget when you start pulling a lot of fuel out on a s-afc 1st gen, 2nd gen or whatever your timing is gonna be way advanced. just somethin to keep in mind.

dave

Another very good and engine saving point!

 

[MKIIISupraGuy]

ah just run race gas dang it

 

[DigitalDUST]

ok thanks guys.

IS IT OK to use 780cc??

I am going to tune it on a dyno and have them adjust it to a safe level of performance.. if that dont work. maybe I can trade in the 780's for a 680 cc instead ??

good point about timing!!!

about the "right" pump will walbro 255lph work ??

 

[X-man]

Wal-bro's are supposed to good for 550 to the ground. I believe this is when Will N. figured out he need more fuel. If you were planning to max out a set of 780's you would need two Walbro's or an Aeromotive or SX pump. I have heard of people getting 600 to the ground but it was stated that it was really leaning out. Yes it is possible to make 780's work, there is someone on here already doing it on a Lexus meter I believe.

 

[DigitalDUST]

I have decided and changed my mind.. I am going with the 680cc's with the setup I currently have.. I wont be upgrading my turbo not for another year or so. I just want to max out my turbo's capacity and 680 is perfect for 500 to the ground or so. I dont want to push the limits of 550's I just want to be in the middle range where its tuneable without putting it all to the max limit..

you have been helpful. I just got my walrbo and I think it will be sufficent for my SAFC 5 knob. and 680's with the lex afm.

if i needed to push more fuel Ill just drop in an addtional walbro to make it dual!

 

[X-man]

Good choice I think you'll be alot happier. The off boost response mine picked up by going 680's with the vpc and afc was great.