660's or 720's?

[Kaane]

Here is my question, Car is almost done, now I have to decide which injectors to use.

I have a 6bolt built motor, Crower rods, Wiseco Pistons, Fully built head, with Ferrea Valves,HKS 272 cams, Crower Titanium Retainers, Crower Springs, blah blah blah blah.....

I am installing a 20g TDO6, along with a FMIC, Supra TT fuel pump, AFPR. I am in california, where the gas sucks and is 91 octane. Most people say that 660's are more then sufficient for a 20g, but some say that running on crappier gas you need to have a some bigger ones so you dont have excess knock at high boost, on the other hand people say that they have problems idling with large injectors. So which ones should I go with? My goal is 400WHP. (might not be possible on pump gas I know)

Thanks.

 

[candela]

As you said 660's should be plenty efficient. I also feel you on the whole 91 pump thing, it sucks bad...

 

[Kaane]

ok, What brand injectors are the best? I can get some Greddy ones cheap, are they any different then Denso ones? How good are the Injector Clinic 650's ?

 

[Tranman]

GReddy just rebadges Denso Injectors...so does Blitz, but I'm not sure about HKS.

 

[fast_talon]

I am running a T3/T4 50 Trim and I am using ND 660's. I have plenty of fuel.

 

[candela]

ya greddy isnt anything special, no difference. Just go with the proven Nippon Denso, but injector clinic is good also. If you search around you should be able to find em for 400$

 

[Nappy94]

660's Denso.

 

[95GST]

660s will be fine, if you feel you're maxing them out, you can always increase the fuel pressure with your AFPR.

You can only make so much HP with 91 octane unfortunately and 720s is NOT going to give you any more advantage. 660s will be easier to tune.

I have the supra pump and APR like you, I was about to run the 660s rich enough too sputter and make my oil smells like gas. Oops. way too rich.

In fact I'm considering going back to a 16g and smaller injectors.. I'm going to sell my denso 660s on tuesday, they're coming off the car. If you're interested please e-mail me [email protected]

 

[ProStreetOnline]

660s are plenty. Buschur is an example.

 

[AWDGSXownsU]

why is everyone so scared of 720's its only 8% more fuel than 660's. i personally like the injector clinic 750cc injectors. i ordered me some still waiting for them to come in the mail. bigger injectors mean lower IDC's, probally more timing, better egts, more power, if your worried about fuel consumption just lean it out 8% more than 660's. injector clinic injectors cost the same as nd's or greddys or blitzs (which are all the same just rebadged) the ball style injecots of ic injectors is supposed to be superior. better atomization better power etc etc. id call them up and ask them why you should run thier injectors. they convinced me. i did further reasearch just to feel safe. seems like a very good injecots. i wouldnt worry about having big injectors tibor, your getting the aem ems. you should have no problem controlling those big puppies. if you get the aem ems u can run staged injecotors. 2 sets of 450's. 1 set for bottom end next set for when boost kicks it. 900cc's worth of fuel an no idle problems blah blah blah. custom fuel rail with 8 injector ports might be pricey but seems like a cool idea

Manny
92 GSX

 

[Kaane]

No one, is afraid to run them, problem is there is a set ammount you can lean out a injector, and once it reaches that point and it is still dumping too much fuel, your car will run like #@%#@%#@%#@% at idle or stall.

 

[AWDGSXownsU]

that is true but im sure 720's can be leaned out 8% more. especially with a standalone. if you want great idle and lots of fuel i guess the 2 sets of 450's is the only way to go. hopefully custom fuel rails are not more than 300 bux.

Manny
92 GSX

 

[RocketDSM]

A while back I remember someone online had a calculator for how large an injector you would have to use to get a desired horsepower. It had something like a dozen variables you had to enter. If you can find it, it may help some. If I remember right you needed to enter BSFC which I don't know for our engines (and probably varies widely on mods). Frankly, if you have the management for it, I would run the biggest injectors you can. Find out what the minimum pulse width the AEM can make is, compare that to the minimum reaction for the injector and do some hardcore math. See if you can lean it out enough on paper first.

 

[TURBOSPYDER]

720cc injectors are bit too big. My car runs crappy at Idle, and on the AFC at high throttle, Im at -45 or so, with EGTs hitting 850-875c. I put some race gas in there one time and my car was just misfiring all over the place cuz with one step colder plugs and 114 octane fuel, the injectors couldnt ignite the gas in the cylinders.

 

[TURBOSPYDER]

720cc injectors are bit too big. My car runs crappy at Idle, and on the AFC at high throttle, Im at -45 or so, with EGTs hitting 850-875c. I put some race gas in there one time and my car was just misfiring all over the place cuz with one step colder plugs and 114 octane fuel, the injectors couldnt ignite the gas in the cylinders.

 

[marksae]

yeah, 720s are too big if you're running just an AFC and race gas. You need to be able to lean out the car another 10% or more with race gas. I had a TRE afcMASC, 720s, and a pair of 272s on my 1g and I got it to idle like stock. I say get the largest injector you can control so you don't have to worry about upgrading later.