Quick question about Injectors:550's or 720's

[fletch]

I've been looking for some 550cc injectors and I see that price isn't that far off from 720's, in some cases the latter are cheaper. I was just wondering if I can run 720's at lower levels (like 550cc level) with the lex afm and an fpr or will that now work?

-fletch

BTW-I couldn't find a similar question in the search.

 

[spoolint78]

Its possible, you just have to pull a lot more fuel.

 

[jtamulis]

Yes you can, but you'll find the 550s will give you a better idle, better fuel
economy, and be better suited for what you want until you're really ready to
take the plunge to 720s. Also you'll be able to sell the 550s later easily.

Jeff

 

[97TSiAWD]

As has been mentioned, you would need an SAFC or some similar tuning device to properly reduce the amount of fuel if you went with 720s.

 

[djordan97]

instead of spending the money on the lex and a safc I would go maft pro then you will be speed density as well as boost controll and data logging as well as timing controll and be able to controll just about any injector you want. if you can tune an safc then you can tune a maft-pro.

 

[drjonez]

I've been looking for some 550cc injectors and I see that price isn't that far off from 720's, in some cases the latter are cheaper. I was just wondering if I can run 720's at lower levels (like 550cc level) with the lex afm and an fpr or will that now work?

-fletch

BTW-I couldn't find a similar question in the search.

#1 question is WHY!?!?!? no need to run 4X the size of inj than you need....

as always, figure out your goals for the car, then decide on the path to get there.

 

[Supra]

#1 question is WHY!?!?!? no need to run 4X the size of inj than you need....

as always, figure out your goals for the car, then decide on the path to get there.

Is there any problem running 720's with the MAFT PRO?

 

[drjonez]

personally, i think there is a problem running ANY piggyback w/65% larger injectors. if you need that much fuel, you should be running a standalone.....then again, that's just my opinion.....

yes, you can run 720s w/the MAFT pro.

 

[Supra]

personally, i think there is a problem running ANY piggyback w/65% larger injectors. if you need that much fuel, you should be running a standalone.....then again, that's just my opinion.....

yes, you can run 720s w/the MAFT pro.

You're talking to the guy who drove his "new" Supra to Dave Hall's house to get the Lexus / 440's setup some 8 years ago... :icon_bigg

 

[djordan97]

thing is 550's and afpr will provide lots and lots of power. the only reason to go bigger is if your making stupid amounts of horsepower and if your goal is stupid horsepower then you definately shouldn't be skimping on your electronics at all or for that matter any part of the car.

 

[fletch]

dr jonez, the only reason I was wondering is to save buying injectors twice. I know that right now the absolute most i need is 550s but i dunno about the future.
good point, even if i decide to go bigger later i shouldn't have a problem selling the 550's.

MAFT pro just sounded really complicated(I though it was standalone) but I'll have to ready up about it, might be the way to go. I had been thinking of doing safc + avc-r but with maft pro would the avc be worth it or better to just go with something like a profec. Like I said i'm gonna have to read a lot more.

thanks guys

-fletch

 

[djordan97]

truely the maft pro is not complicated at all. with the stock injectors you can just about hook it up and go putting off down the road with very little tuning and just setting a few settings. it's very nice to be speed density as I found that I have better throttle response with it as well as more power through out the throttle and rpm range with it.

 

[fletch]

So you'd defininitly recommend going straight to mafpro and not even worry about and safc. Thats cool I'm glad this came up, now its time to use the search button and start reading, thanks for the advice.
cheers

-fletch

**edit** aha! http://www.supramania.com/forums/showthread.php?t=11783&highlight=maft+pro

 

[Halsupramk3]

i bought some 720s for a good deal instead of getting 550s. Like you said why buy twice. I am using an aem ecu to tune and it works well. When you use a safc type piggy back you may have trouble getting an idle because if i am correct the oem ecu will only go down to 3% duty minimum at idle. you would have to go lower with 720s to lean out the idle to smooth it out. My aem is about 1% duty or so with the 720s at idle. I not know how the maft would work and what duty % it would use as i have never used it. If you are going no more than about 420 to 450 flywheel hp 550s would be in the 80% duty area. Others making this power could confirm if that is a low or high guess.

 

[bluemax]

Thanks for commenting Hal. I did the duty cycle calculations too and decided to go to 720cc for safety.

I've got an AEM and 720cc injectors in the box for my rebuild. I was worried about idling those garden hose injectors.

Incidently,my RC 720cc's were very expensive. Much more than 550's. Has the price gone down?

 

[Adjuster]

I'm about to find out if 780cc injectors will work with the Maft Pro, and idle like stockers, or close to it.



Fuel pressure will be key I'm thinking. Just enough to atomize the fuel, yet work inside of the "3%" barrier everyone is talking about.

With 550's I was over 30psi base fuel pressure to get the Vf reading near 2.5v. It's going to be interesting to see where It ends up with the Maft Pro and 780's at idle to get the Vf to 2.5v if possible. (That's the middle of the range for the TCCS.)

If would think if your worried about it, the 600 something injectors are the best compromise of power potential, and low engine speed flow rates v/s duty cycle.

 

[fletch]

cool, lmk how it goes adjuster, I'm pretty much decided on maft pro now. It seemed a little intimidationg but there's so much information on here and so many people willing to help that if I have a problem we shoudlbe able to make short work of it. Just reading about it today it makes sooo much more sense. i'd been planning on doing safc and avcr but to buy those new together would be close to or over $700! A maft pro setup as far as i can tell is more capable and runs about $600 new. Theres even a fitting for boost controller, i'm hooked!
Can't wait till i've paid for my paint job, sell my lex afm, buy injectors and go maft pro.

-fletch

 

[drjonez]

thing is 550's and afpr will provide lots and lots of power. the only reason to go bigger is if your making stupid amounts of horsepower and if your goal is stupid horsepower then you definately shouldn't be skimping on your electronics at all or for that matter any part of the car.

just so peeps don't get confused, just adding 550s + an AFPR will NOT give you any more power....

I'm about to find out if 780cc injectors will work with the Maft Pro, and idle like stockers, or close to it.



Fuel pressure will be key I'm thinking. Just enough to atomize the fuel, yet work inside of the "3%" barrier everyone is talking about.

With 550's I was over 30psi base fuel pressure to get the Vf reading near 2.5v. It's going to be interesting to see where It ends up with the Maft Pro and 780's at idle to get the Vf to 2.5v if possible. (That's the middle of the range for the TCCS.)

If would think if your worried about it, the 600 something injectors are the best compromise of power potential, and low engine speed flow rates v/s duty cycle.

it's def. possible. i set up a customer's car w/720s + the eman yrs ago...ON THE STOCK AFM. don't ask why....

cool, lmk how it goes adjuster, I'm pretty much decided on maft pro now. It seemed a little intimidationg but there's so much information on here and so many people willing to help that if I have a problem we shoudlbe able to make short work of it. Just reading about it today it makes sooo much more sense. i'd been planning on doing safc and avcr but to buy those new together would be close to or over $700! A maft pro setup as far as i can tell is more capable and runs about $600 new. Theres even a fitting for boost controller, i'm hooked!
Can't wait till i've paid for my paint job, sell my lex afm, buy injectors and go maft pro.

-fletch

the MAFT pro fits the bill for 95% of the MKIII owners out there. it's relatively cheap, flexible and scaleable (i.e. buy the base unit if you're short on cash, then add speed/density, then add boost control, etc.). don't forget i sell them, drop me a line when you're ready to order.

 

[Adjuster]

Well, and with timing control and monitoring, afm signal control, boost control, speed density and AF tracking/closed loop running at WOT, the Maft Pro is the best option I've seen short of the full stand alone. (And I've never wanted to go that far from stock money wise, however with no AFM now, being able to run if the Maft Pro fails is not really possible if your speed density.)
The flip side is with the AFM, your dependant on excellent connections and no leaks from the air filter to the throttle body. With the Maft Pro, you can have minor air leaks, vented BOV's and other stuff with zero problems as far as the engine is concerned. The fact that it can be tuned to exactly "your" engine is pretty cool too. (When setup right, from what I've read, the engine runs smoother, has better throttle response and can get excellent fuel economy using the Maft Pro, plus you have more power when tuned right.)

 

[xXxICExXx]

550's are more than enough for the set-up with most of our cars. If you go 720 you are just spending more money on something that wont gain you anything if you dont need it. If the time comes in the future you need 720s for your near outlaw supra then selling the 550s wont be hard at all. Infact, I need a set right now. Anybody?