780 injectors with 16g?

[KelTsi90]

Hi i have an evo III 16g, 550 injectors(r7 TurboII), walbro 255 pump, MAllory fpr, and 3"MAf translator i also have tubular manifold,3"exhaust, fmic, etc. Now I have the car set at 15psi of boost but i want 20psi. Some friend recommended me to go with 650's but i cant find them, I find 780's for a good price. is it Ok?? to go with 780 injectors with the 16g or they are too big for this turbo?? or should i keep going with my 550's??

Thanks,
Kelvin

 

[kittay]

It's a bit more then what you really need, but it won't hurt anything.
I'm running 750s, but I also run E85 in the summers.

Just make sure you have a fuel management, wideband/ logger is good too

 

[skeeter4200]

its not going to hurt anything to run those injectors but I would recommend getting an SAFCII or better yet the DSMLINK which im currently trying to get , do you have a fmic

 

[skeeter4200]

ok just read that you do have a fmic , you can run at 20psi now just need to make sure you get your motor tuned for it at a local dyno shop but you will need some kind of engine management system

 

[My1GLaser]

Yeah like ^^^^ are saying. You will need some sort of management system for those to work properly. I have a MAFT & tried tuning with just that and it sucked...or maybe it was me. 650's are about the highest I would go using a system that "tricks" the ECU about airflow because when the ECU sees less airflow it puts you in a different part of the timing map that is very aggressive. And our 1gs are high to begin with. Check out this link if you are interested. http://jeffgst.com/id20.html

I don't remember the exact numbers because after about a month of fuel cut and a horrible tune I just bought DSMLink and never looked back.

The MAFT or SAFC will be lying to the ECU about airflow numbers to compensate for the extra fuel flow. If the ECU "sees" less air then it will put in less fuel. But actually the motor isn't getting any less air and the ECU is calculating fuel "thinking " it has the 450 injectors still. So now the larger injectors are supplying the right amount of fuel for the actual airflow because the ECU is firing them for a shorter length of time.

The only way I know of to get the ECU to know that you have 750 injectors is:

1. Get a chip burned.
2. Get DSMlink.
(You will need an Eprom ECU for both of those, which you probably have since its a 90.)
3. Get some kind of standalone engine management.

I wanted to explain it as much as I could, since I was in your EXACT situation not long ago. I was running my EVO III 16g at 14 psi with 450 inj and trying to tune with a MAFT. I was getting horrible fuel cut at 5500 rpm right when it was getting fun. I looked at all the options and figured I would end up with DSMLink in a year anyway, so I just got it first and saved the headache. People bi*** about the MAFT & DSMLink together, but I haven't had a whole lot of problems. And that link is the best info on DSMLink & MAFT.

Well that was longwinded. So in short 750s will be fine to buy. They are not to big for the turbo, they are too big for the ECU to control without issues. Mostly running rich as hell and a longer time to respond to the ECU telling them to fire. They are bigger and take longer to respond, but the ECU doesn't know that because it thinks you have 450s. Idle is mostly where the "deadtime" issues are a problem, but it can affect higher rpms as well.

The good thing about lying to the ECU about airflow being lower is that you hit fuel cut later in the rpm range.

Good luck.

 

[skeeter4200]

if you have the 550's already just stick with them you can still get around 300 hp with them , I got them and Im at 280 cause my boost controller wont hold anymore than 18psi i getting ready to order dsm link and new cams

 

[mach4g63t]

You can look here for deals on injectors.

 

[KelTsi90]

I will have to find an eprom or dsmlink before getting those injectors.

Thanks for the help,
Kelvin

 

[My1GLaser]

You might have an eprom, unless you already know for sure that you don't. DSMLink - FAQ - EPROM