Some quick, easy, assorted fuel injector questions :)

[MarkEmark]

Hey,

As some of you may know I'm planning on rebuilding my engine this summer with forged internals.

The compression ratio will be 9:1, and my current turbo (T3 super 60 .48 a/r turbine, .60 a/r compressor) will be upgraded to the venerable T3/T04E "50" trim. Fuel will be controlled via a JWT ECU, upgraded MAFS (Z32 or Cobra), a walbro 255 lph fuel pump, and an adjustable FPR. Ultimate goals will be around 330+ rwhp, but I can't ever see myself wanting more than 330 rwhp, but room to play is always good. Not sure how much boost will be needed to achieve that horsepower level, but from what I've been reading from dyno charts, etc, I'd say around 17 psi (The engine won't have the luxury of being tuned by an AEM EMS, and therefore it's not gonna make 750 rwhp at 17 psi! lol)

Anyway, first question:

Will MSD 50 lb fuel injectors (525 cc) be sufficient enough for the 330 rwhp mark, or is that on the ragged edge of the injectors' capabilities? Keep in mind that I have an adjustable FPR. Looking at structure240sx's specs on KA-T.org, he ran 19 psi with 550 cc fuel injectors (unless his dyno chart was updated but not his modification list).

The problem with immediately jumping up to 72 lb MSD fuel injectors is that they flow a subsantial 44% MORE than 50 lb fuel injectors and are capable of quite a bit more horsepower and boost that I'm not going to be running...And I certainly don't want to be running extremely rich all the time with those 72 lb injectors. I'd rather almost be maxing out the 50 lb fuel injectors and then be able to turn up the fuel pressure via my nice adjustable Aeromotive FPR than have to live with a constantly pig-rich condition.

Next question:Browsing through the http://www.ka24de.com website, the MSD 50's are listed as high impedance whereas the 72's are listed as low impedance...is this true for all of the universal MSD 50's and 72's? This is going to sound n00bish, but what the hell do the different impedances entail? I realize that the low impedance runs at lower ohms (2) than the high impedences (12), but why, and what effect does it have? I'm not planning on upgrading my ignition system unless I absolutely need to.

Next question:I realize that all the MSD injectors are "top feed," and not "side feed," and therefore require an aftermarket fuel rail like the JWT....but stock fuel injectors are side feed, so why does everyone go to top feed? Is it because top-feeds are more "universal" ?

I'd actually rather keep them side feed, so that way I wouldn't need to needlessly spend money on an aftermarket fuel rail, so are there any drop-in 525 cc fuel injectors that are side feed and fit the OEM KA24DE fuel rail? Would 525 cc side-feed fuel injectors (are they low impedance or high impedance?!?) work with a JWT ECU tuned for MSD 50 lb fuel injectors that are top-feed and high impedance?

Lastly, looking on JWT's website (which, btw, is pretty terribly done), the only ECU retunes they have for the MSD 50 lb fuel injectors are for use with the Cobra MAFS. I could have SWORN that they had an ECU retune for 50 lb fuel injectors and a Z32 MAFS, and that the larger Cobra one was reserved for 72 lb/hour fuel injectors. I'd rather go with a Z32 MAFS because they're available quite a bit cheaper.

Okay, that's it for now

Wow, that turned out to be a LOT longer than I had anticipated. Do your best to answer guys!


Modified by MarkEmark at 7:15 PM 12/28/2004

[nizmo240sx_22]

Will MSD 50 lb fuel injectors (525 cc) be sufficient enough for the 330 rwhp mark, or is that on the ragged edge of the injectors' capabilities? Keep in mind that I have an adjustable FPR. Looking at structure240sx's specs on KA-T.org, he ran 19 psi with 550 cc fuel injectors (unless his dyno chart was updated but not his modification list).

The problem with immediately jumping up to 72 lb MSD fuel injectors is that they flow a subsantial 44% MORE than 50 lb fuel injectors and are capable of quite a bit more horsepower and boost that I'm not going to be running...And I certainly don't want to be running extremely rich all the time with those 72 lb injectors. I'd rather almost be maxing out the 50 lb fuel injectors and then be able to turn up the fuel pressure via my nice adjustable Aeromotive FPR than have to live with a constantly pig-rich condition.

50lb injectors should be fine to around 375 rwhp. Why would 72lb injectors run pig rich all the time? If tuned right AF ratios should be the same.

[MarkEmark]

I'm not going to have an S-AFC to do any tuning so I'll be at the mercy of JWT's ECU program...and their programs for 72 lb injectors I'm sure are pretty damn rich and conservative (but maybe not more so than their program for the 50 lb injectors) considering most people using 72 lb injectors are going for some big numbers and are running quite a bit of boost...they need to make it rich and safe enough so customers aren't destroying their engines and blaming it on JWT. I'll probably eventually get a S-AFC but that's just another $350 for something I'm completely unfamiliar with. Also, I have emissions testing to deal with, and I think it'd be easier to pass with 50 lb injectors than with 72 lb injectors...but again, i could be wrong...as you can see my fundamentals regarding fuel injectors aren't very sound....

Anyway, that's good to know that 50 lb/hr will be plenty. I wonder why all the guys on ka-t.org use 72 lb/hour even if some of them are only making 330 rwhp...

Also, nizmo240sx_22: what kind of boost are you running and what kind of power are you making? Do you have a website? I'll be using the same turbo as you (probably) and maybe even the same pistons...would like to know if you're happy with your setup Also, do you know the specs of your JWT cams?

[fastpace]

I have the 50lb jwt ecu program, but I run it with 550cc side feed injectors. I have no problems at all.

[Redline240]

i only plan to make 350hp on my kat next summer but since the 72lb injectors are the same price as the 50lbs ones i'm gonna get the 72lb cause i know i'll be eventually building the engine and turning up the boost so its just one less thing to buy then....

Redline

[MarkEmark]

I have the 50lb jwt ecu program, but I run it with 550cc side feed injectors. I have no problems at all.

Awesome, this is good news...I could bypass the price and hassle of a new fuel rail...(however, now that I look, 550 cc injectors seem to be more expensive than 50 lb/hr injectors, perhaps so much more expensive that I may as well just buy the injectors and fuel rail).

What is your complete setup? How does it run? Rich? Lean? Any a/f ratios you'd like to share? Dyno charts? Psi you're running?

Is it an S13 or S14? AT or MT?

Also, what kind of 550 cc injectors are they/where'd you get them?

thanks...

[fastpace]

Awesome, this is good news...I could bypass the price and hassle of a new fuel rail...(however, now that I look, 550 cc injectors seem to be more expensive than 50 lb/hr injectors, perhaps so much more expensive that I may as well just buy the injectors and fuel rail).

What is your complete setup? How does it run? Rich? Lean? Any a/f ratios you'd like to share? Dyno charts? Psi you're running?

Is it an S13 or S14? AT or MT?

Also, what kind of 550 cc injectors are they/where'd you get them?

thanks...

It is for a S13 and with a MT. I haven't dynoed the car yet, but once I finish up with the maintanence I will dyno it in a week or so. I will let everyone know. Just by me driving it runs rich, can always smell gas in the car, but is very safe this way. The car idles around 830-900 depending on temp of the day.

My setup is jwt ecu, with cobra mafs, Power enterprise 550cc injectors(got from phase2), 255lph walbro fuel pump, and super 60 T3. Right now I am running on stock wastegate(7.25psi), I have also ran 9.55psi, 10.75 psi, and 1 bar with this setup.

[MarkEmark]

It is for a S13 and with a MT. I haven't dynoed the car yet, but once I finish up with the maintanence I will dyno it in a week or so. I will let everyone know. Just by me driving it runs rich, can always smell gas in the car, but is very safe this way. The car idles around 830-900 depending on temp of the day.

My setup is jwt ecu, with cobra mafs, Power enterprise 550cc injectors(got from phase2), 255lph walbro fuel pump, and super 60 T3. Right now I am running on stock wastegate(7.25psi), I have also ran 9.55psi, 10.75 psi, and 1 bar with this setup.

Oh yeah, i remember you posting a while back that you were going to test the limits of the T3 super 60 because you were the only one with a sufficient fuel system to push the boost on a T3. I'm looking forward to the results, especially when you're running 1 bar...should be interesting.

Keep us posted.

Also, those 550 cc fuel injectors are $500(!!!!) from phase2...I can get MSD 50 lb injectors and an aftermarket fuel rail for probably $350..Looks like I'm going with that....

[fastpace]

Yeah, they were expensive, I was just too lazy to change to a different fuel rail, injectors and deal with the connections.

[andrave]

jwt tunes for z32 and 50 lb.. thats what I have

[side waz]

Hey man what's up.

You could also look for them used and save a few bucks. As well RX-7 FD injector's are 550's and are side feed too. That's just another option for you.

I am sure you will be more then happy using injectors of this size as your hp goal will not max the duty cycle, of the injector's, out.

Good luck with your build up man it sounds like it has real promiss.

Take care.

Easy

[MarkEmark]

jwt tunes for z32 and 50 lb.. thats what I have

Okay good...I knew I remembered seeing on their site an ECU for a z32 MAFS and 50 lb injectors and had heard of them doing it before...strange that it's not on their site (terrible website....I think it needs some help from Klattr1 )

side waz/anyone else: do rx-7 FD 550cc side feed fuel injectors drop right in the KADE rail?

[andrave]

no. they do not. they need the D speed collars.

Also, if you need anything from jwt just call. Its easier to wait on hold for 5 mins than to wait for them to email you back, which can take a week or more.

[DRIFTEADOR]

while we're on the injector topic, anyone know which subie injectors drop in? something like pink or yellow tops

[Structure240sx]

550cc injectors can take you to 400rwhp. i have "heard" of people getting almost 430whp out of them.

yes sidefeed injectors are more expensive. the benefit is that they drop right in. sometimes going to top feeds you have to fix leaks at first. also top feeds require injector clips to be installed.

on the subject of high and low impedence. our stock injectors are high impedence which our ecu controls. switching to low impedence injectors require the install of resistors to change the impedence so the ecu can work with them. jwt ecu also require this.

top-feeds can be had for about $250fuel rail $150you can use the stock fpr but you want to use the aeromotive which i think is about $100brand new nismo 550's are $500 which equals your cost of the top feedsof course to tune will be another $200 or so for an safc

personally i think that using the fpr is a weak way to tune the entire fuel system. it has been know with some jwt ecu to run dangerously lean in some spots. safc's can be had for $250 brand new. i got mine used for less than $200. this way you can tune the entire fuel map at certain rpms differently. the install is only about 5 wires and its super easy to use after a few minutes.

newer WRX, STI injectors can be used. WRX sidefeeds are 480cc and STI sidefeeds are 550cc. the stock injector plug i believe can be modified slightly to work or you will need subaru clips to use

another benefit people say for top feeds is switching to a top feed rail. these rails flow better than our stock rails. to argue this point is that no one has ever mentioned that the stock fuel rail has not flowed enough. obivously it can. i dynoed 365rwhp at 5200rpms, hp was still climbing and easily would have reached 380.

if you look around you can find 550's that drop right in for $350. thats how much i paid for mine and they were cleaned prior. unfortunately one was burnt out and i had to buy a new nismo, nothing you can really do about something like that.

personally i would go with 550's sidefeeds in the stock rail and stock fpr with an safc. i would also invest in a wideband. of course this is my setup so i guess im a little bias. going with an "off-the-shelf" ecu can be risky sometimes. with a setup like this you will always know what is going on and always be able to adjust. yes it may cost $100-300 more but there is much more safety going this route.

[Structure240sx]

something else i forgot to mention.

the ecu can and does adjust quite a bit. if your arent tunned perfect say at idle it willadjust itslef to bring the afr up to 14.7.

i figured this out when i had my 480cc injectors in. i was making sure i would be able to run 550's. my setting for 480's was around -45%. i turned it up to -35% and at first it was a bit rich. then after a few seconds it began to lean out to come back to 14.7-15 afr. so the ecu will adjust itself some to get the idle right.

this mean if you were to go with 550's on a 50# program it shouldnt have a problem idleing perfectly by itself

[MarkEmark]

550cc injectors can take you to 400rwhp. i have "heard" of people getting almost 430whp out of them.

yes sidefeed injectors are more expensive. the benefit is that they drop right in. sometimes going to top feeds you have to fix leaks at first. also top feeds require injector clips to be installed.

on the subject of high and low impedence. our stock injectors are high impedence which our ecu controls. switching to low impedence injectors require the install of resistors to change the impedence so the ecu can work with them. jwt ecu also require this.

top-feeds can be had for about $250fuel rail $150you can use the stock fpr but you want to use the aeromotive which i think is about $100brand new nismo 550's are $500 which equals your cost of the top feedsof course to tune will be another $200 or so for an safc

personally i think that using the fpr is a weak way to tune the entire fuel system. it has been know with some jwt ecu to run dangerously lean in some spots. safc's can be had for $250 brand new. i got mine used for less than $200. this way you can tune the entire fuel map at certain rpms differently. the install is only about 5 wires and its super easy to use after a few minutes.

newer WRX, STI injectors can be used. WRX sidefeeds are 480cc and STI sidefeeds are 550cc. the stock injector plug i believe can be modified slightly to work or you will need subaru clips to use

another benefit people say for top feeds is switching to a top feed rail. these rails flow better than our stock rails. to argue this point is that no one has ever mentioned that the stock fuel rail has not flowed enough. obivously it can. i dynoed 365rwhp at 5200rpms, hp was still climbing and easily would have reached 380.

if you look around you can find 550's that drop right in for $350. thats how much i paid for mine and they were cleaned prior. unfortunately one was burnt out and i had to buy a new nismo, nothing you can really do about something like that.

personally i would go with 550's sidefeeds in the stock rail and stock fpr with an safc. i would also invest in a wideband. of course this is my setup so i guess im a little bias. going with an "off-the-shelf" ecu can be risky sometimes. with a setup like this you will always know what is going on and always be able to adjust. yes it may cost $100-300 more but there is much more safety going this route.

Hmm....how often does switching to top-feeds entail fuel leaks? I certainly don't want ANY kind of fuel leak....

The MSD 50's are high impedance, so I won't need any resistors. It's the 72 lb-ers that are low impedance. I'm just wondering what the main difference was between them besides impedance...

Top-feed MSD 50 lb-ers can be had brand new for $250...used I could get them for $180 or so (I just saw Fiznat selling some MSD 50's for that price), and I already have the aeromotive FPR. I've seen people selling the top feed fuel rails for like $100 or so. Injector harnesses I believe are around $15? So it'd be like $300-$315 for the injectors/fuel rail if I shop around, which is quite a bit cheaper than $550. And, come to think of it, the last time I switched out my fuel injectors, it was such a pain in the *** getting the injectors out of the fuel rail that I'd rather just get an entirely new fuel rail and then install the top-feeds.

I'm not planning to use my FPR to "tune" the entire fuel system, only to tweak it just a bit...I'm not talking about anything crazy here, just increasing the fuel pressure or decreasing it a few psi as my a/f's dictate...I have enough trust in JWT's tuning abilities to believe that their tune for my ECU will be pretty good....I have no complaints about this one...and I'm able to record with my Blitz R-VIT what kind of timing the tuned ECU is doing, so I was able to advance my timing 2 degrees to make it run quite a bit better and lower the fuel pressure 2 psi so it wasn't so rich (it's still pretty rich though). S-AFC's are the way to go, but I really have no idea what the hell I'm doing with them, and frankly I'm afraid I'd do catastrophic damage to an extremely expensive and freshly rebuilt engine. And I doubt any of the dyno shops around here know how to tune that stuff, and I'm not sure I'd trust any of them even if they claimed to know how. Also, where do you get S-AFC's brand new for $250?!? I thought they were $350 brand new. $200 used isn't bad at all...

I should have purchased a wide-band like the PLX-300 to begin with when I was searching around for a multi-checker...I didn't know they were only $300....And now that I recently spent $350 on the Blitz R-VIT (which does measure a/f, in a narrow band 0-1v format, which isn't that accurate, but isn't that bad either), another $300 seems extreme. I'd sell the Blitz for the wideband but I like knowing my injector duty cycle, MAFS voltage, timing, water temp, etc etc.

Anyway, thanks a lot for the input Anthony!

[hannibal]

boostDesigns has a great price on SAFC

[andrave]

550cc injectors can take you to 400rwhp. i have "heard" of people getting almost 430whp out of them.

yes sidefeed injectors are more expensive. the benefit is that they drop right in. sometimes going to top feeds you have to fix leaks at first. also top feeds require injector clips to be installed.

on the subject of high and low impedence. our stock injectors are high impedence which our ecu controls. switching to low impedence injectors require the install of resistors to change the impedence so the ecu can work with them. jwt ecu also require this.

top-feeds can be had for about $250fuel rail $150you can use the stock fpr but you want to use the aeromotive which i think is about $100brand new nismo 550's are $500 which equals your cost of the top feedsof course to tune will be another $200 or so for an safc

personally i think that using the fpr is a weak way to tune the entire fuel system. it has been know with some jwt ecu to run dangerously lean in some spots. safc's can be had for $250 brand new. i got mine used for less than $200. this way you can tune the entire fuel map at certain rpms differently. the install is only about 5 wires and its super easy to use after a few minutes.

newer WRX, STI injectors can be used. WRX sidefeeds are 480cc and STI sidefeeds are 550cc. the stock injector plug i believe can be modified slightly to work or you will need subaru clips to use

another benefit people say for top feeds is switching to a top feed rail. these rails flow better than our stock rails. to argue this point is that no one has ever mentioned that the stock fuel rail has not flowed enough. obivously it can. i dynoed 365rwhp at 5200rpms, hp was still climbing and easily would have reached 380.

if you look around you can find 550's that drop right in for $350. thats how much i paid for mine and they were cleaned prior. unfortunately one was burnt out and i had to buy a new nismo, nothing you can really do about something like that.

personally i would go with 550's sidefeeds in the stock rail and stock fpr with an safc. i would also invest in a wideband. of course this is my setup so i guess im a little bias. going with an "off-the-shelf" ecu can be risky sometimes. with a setup like this you will always know what is going on and always be able to adjust. yes it may cost $100-300 more but there is much more safety going this route.

side feeds "drop right in" if you can manage to get the stock phillips head screws out of your stock rail, and wrestle the new injectorts in without mangling an O ring, making them dump fuel into your cylinder...I think its easier to take off 2 screws to loose the fuel lines, 2 screw to loosen the fuel rail, and swap the rail assembly for a top feed one. From then on, switching injectors is a 5 minute affair, as they just pop in an out.I never had any problem with leaks on my topfeeds, and I made my setup myself. I think the top feed design provides a better seal than sidefeeds, myself. You don't have to install new clips, in most cases you can modify the stock ones to fit. I installed new clips on mine and they cost 12 dollars all together and its 8 solder connections, no big deal, takes about 10-15 minutes, and my aftermarket clips have little metal clips that pop right off instead of the side feed with that wrap around wire stuff that never comes off right.

Top feed injectors are available in high or low impedance, so if you end up with top feeds that require you to solder in resistors thats your fault for not shopping around for the correct injectors. Even so, the resistors are cheap and easy to install.

For your prices, you neglect to mention that your top feed setup would have an adjustable fuel pressure regulator whereas the sidefeeds would have the stock one. Even in your cost for cost comparison, the topfeeds win. BTW, the aeromotive unit can be had for far less on ebay.Try my setup- brand new flow matched 50 lb msd injectors- $230 shippedMustang fuel rail- $20 (for 2 sets of them, thats 4 rails...)Custom brackets- (free steel from scrap bin at machine shop, my labor in drilling, wedling, and bending, also free)locking slide on injector clips- 4 for $12Accell Adjustable fuel pressure regulator: $36 brand newTotal price: $298So for under 300 thats a complete 50lb high impedance setup that uses the stock fuel lines and indexes on a 1:1 ratio. Hard to beat, and it includes brand new injectors and adjustable fuel pressure regulator, all the seals you need, and just requires an hour or two to fit some custom brackets.

Your injectors alone cost $350, and you said one was burnt out. You can get the top feed setup brand new for my cost, with flow matched injectors.

You mention that adjustable fuel rails aren't a reliable way to control the fuel curve... well, they are a good way to correct gross rich/lean conditions, and a JWT ecu will straighten out the rest to get it where it needs to be. They aren't designed to be the sole source of compensation for larger injectors, but they work hand in hand with the ecu to compensate.

I've never heard of someone maxing out the stock fuel rail, but when you are using a mustang fuel rail that cost $5 (consider the 4 for $20) its not like you are losing anything but switching it out.

Just wanted to present the argument from the other side, since no one was standing on a soapbox advocating for top feeds.

[Structure240sx]

yes your mustang rail is a very cheap alternative that does take a little work to make fit right. yes it does seal although some of the injectors sit at an angle.

i can switch my sidefeeds in 10 minutes, i dont know what the big deal is.

the thing about tuning with an fpr is that the jwt has been know to run lean in different spots, not necessarily the entire map. holyshiznit recently blew his motor from a bad jwt tune.

of course if you search around and go with parts like the mustang rail its going to be cheaper. i guess its jsut me that doenst mind spending a little more for something like my injectors.

[MarkEmark]

For your prices, you neglect to mention that your top feed setup would have an adjustable fuel pressure regulator whereas the sidefeeds would have the stock one.

I already have the aeromotive adjustable FPR...it's been on the car for about 6 months and was a major contributor to my passing emissions...it's being used in conjunction with the stock fuel rail right now (needed to fabricate a 90 deg. nipple at the end to locate the FPR elsewhere), but it can just as easily be used w/ a top feed fuel rail.

I agree with you about how much of a PITA it is to replace injectors...I don't know how anyone replaced them w/o removing the entire fuel rail (which I needed to do)...mine were in t here VERY tightly. Even after removing the fuel rail it was a PITA to remove the injectors w/o tweaking the fuel rail...when I sell these current injectors I'm definitely leaving them in the fuel rail.

Also, where do you get brand new MSD 50 lb fuel injectors for $230 shipped? Are you talking about the MSD STYLE fuel injectors on ebay? Is there a difference in quality?

Anyway, I'm pretty sure I'm going to go top-feed...just makes more sense economically....plus, shiny new fuel rails look a lot cooler than old bronze lookin' ones

[andrave]

yeah mine are delphi, which are made by GM...msd style though, no discernable difference in quality.

[MarkEmark]

On a side note, is there any difference in the quality of top-feed fuel rails between BoostDesigns, JGY Custom, or JWT? They're all similarly priced. I think the BD one is the cheapest ($100--BD has a LOT of good prices!) Or are they all pretty much the exact same thing? I don't want to cheap on a fuel rail...I want a nice new one.