muibubbles

iTrader: (36)

Currently i got dyno tuned at kdr. I maxed out at 356whp with 100% injector duty..

so now im looking into upgrading my injectors.. im looking at either 850s all around or 550/1600... i also want to keep in mind that i will be upgrading to a 35r in the future so will upgrade to 850/1600.

These are my mods..
Rebuilt with 3mm apex seals
mild streetport
550/1300 injectors
aeromotive FPR
walbro fuel pump
Stock twins (seqen)
Apexi PF
Apexi Commander
koyo radiator
pettit ast
underdriven pullies
M2 med/large intercooler
custom intakes with greddy/trust filters

I think that pretty much sums it up..

DriftDreamzSS

iTrader: (4)

why not just go 850/1600 now and save the hassle of doing it again later?

fendamonky

iTrader: (6)

/agree

muibubbles

iTrader: (36)

isnt that too much for stock twins?

im getting tight on money and dont want to spend more then i need to at the moment, but i guess that would be an option as well...

fendamonky

iTrader: (6)

Overkill is MUCH preferable to running your IDC at 100%!!!!


You do NOT want to continue running your injectors at those levels as it will (when, not if) lead to failure and you'll more than likely be spending a LOT more on a new engine then you otherwise would on new injectors and a retune.


just my $.02.


You could also have all your injectors cleaned and flow tested on a bench, then increase the base fuel pressure to get more bang for the buck w/o overheating.. I'm running 340(british)/400(US) wheel horsepower with 4x850's that way. My IDC maxes out at 85-86%.

Matt Hey

If you already have 1300cc injectors and want to save some money, why not go 850cc/1300cc? That should be enough fuel for the 35r on pump gas too.

fdracer

850x4 is less fuel capacity than your current setup.

Dudemaaanownsanrx7

iTrader: (23)

delete (double)

Dudemaaanownsanrx7

iTrader: (23)

I'm pretty sure he's on the stock setup, and asking about 850 x 4 vs 550/1600, then also mentions the 850/1600. EDIT: didnt notice his list says 550/1300.... you shouldn't be out of fuel at 350hp. My stock system was maxed around 350.

If your fuel pump hasn't been rewired you might be able to get the duty cycles down just by rewiring it. It increases pump flow around 30%, I know all my AFR's dropped a lot when I did this which then lowered my duty cycles. I can't remember how much though and this is with 550/1680s.

850 x 4 will be enough fuel for what you're doing now. Of course your whole map will need retuned. And your cruise map will be way off, and need some work to get lean cruise afr's. You're idle will probably also suffer, most people have hell getting a lean idle with the large primaries. EDIT: this is less then 550/1300 as mentioned, but even 850x4 should be enough fuel for your needs.

550/1600 should be plenty of fuel for a gt35 unless you plan on pushing 20+ psi, in which case you can increase the base pressure to get enough for your fuel supply. It would also allow you to keep a large portion of your map.

I'm running 550/1680 with a t70 @16psi on a large street port, and my duty cycles are at the upper end of safe (guessing around 450hp) I plan to increase the base pressure so I can run over 20 psi.

As fendamonky said already you can raise the base pressure on your current setup to get your duty cycles down, but you will need a FPR as the stock one is not adjustable. This is probably the most cost effective solution and then later upgrade your secondaries to 1680's. This is probably what i would do in your situation.

muibubbles

iTrader: (36)

2 factors why i want to upgrade...
1 my injector duty is at 100%
2 the failure rate of 1300 scares me and i dont wanna pop another engine....

im on 550/1300 stock rails.. how can i tell if my fuel pump is rewired? what does it mean to raise the base pressure? i also have a aeromotive FPR

thanks again for the help

fendamonky

iTrader: (6)

Check to see if there is an additional wire running from a 12v back into your gas tank.

Basically what we are talking about is raising the fuel pressure your system sees when you are at neither vacuum, nor positive boost pressure (priming the fuel pump is a good way to tell this). The stock fuel pressure is 38-40psi iirc. When your vehicle is sitting at idle and the system is seeing vacuum the fuel pressure will be lower then your base pressure. When you go into boost your pressure will rise higher than the base pressure at a steady rate of 1psi(pressure) per 1psi(boost).

You can change your base fuel pressure by adjusting that little nut on the top of your aeromotive FPR while monitoring it by the fuel pressure gauge attached to the FPR (provided you have the gauge).

I would not suggest adjusting the fuel pressure at home by yourself unless you are familiar with what you are doing. I'd ask the guys at KDR to do it for you, it takes all of 5 minutes (if that) and will, more than likely, require a retune.


Just as an example of what a difference the fuel pressure can make.. I am currently running 50psi as my base pressure (10psi over stock) and my 850cc injectors flow at the same rate as 1000cc injectors at the stock pressure. In addition to flowing more the higher pressure also creates a finer spray pattern, allowing for an easier, more complete mixture of fuel/air making things happier in the end.

The guys who did the adjustment to my fuel system are ASNU certified and have done extensive testing with different injector types/sizes at different pressures and know what they are on about, so I have utter faith in their work.

Matt Hey

I think the failure rate of the 1300cc injectors is exaggerated. Some stick when they are first returned to the customer from cleaning and modification. The cleaning fluid causes them to stick and the same happens with any injectors RC cleans and returns. There are a lot of 7 owners running the modified injectors with no problems.

You should be getting a little more fuel pressure than stock with the Walbro pump. The 550/1300 should be good for about 450 WHP...

http://www.maxcooper.com/rx7/how-to/...tem/calcs.html

What AFR are you running? 850/1300 should be good for about 500 WHP. Raising the base fuel pressure would be good for more of course.

Dudemaaanownsanrx7

iTrader: (23)

I don't think the failure rate is exagerated. You're generally taking an injector thats 15 years old and drilling it out to a much larger size then it was intended to be. While sticking injectors from the cleaning solution is a common problem with any serviced injector i personally have had a stock primary injector burn out. It wasn't sticking or being used at high duty cycles. Just one day stopped working. Tested the continuity and had none. As much as it costs to get a pair of injectors inlarged it's just not worth it IMO. At least going with top feed injectors replacement is hardly an issue being much newer injectors. And cost is much less for a replacement. Those calculators seem to be a bit optimistic in terms of realistic power. I'm sitting at around 450rwhp currently w/ 11.1 afrs and my 550/1680 at a 40 psi base, no pressure drops and rewired pump has my duty cycle close to 90%. While his setup should be more then enough at his power level i don't think 450 is realistic at stock base pressure. I don't think 850/1300 would support 500 hp unless pressure is raised as well.

Matt Hey

@Dudemaaanownsanrx7

Was your injector that burned out modified and how old was it? Some people have brand new injectors modified. It's probably a good idea to replace injectors every so often whether modified or not. The heat can really get to them in the 7. I chose to use 2 new injectors when I went to 850cc x4.

My HP estimates were indeed optimistic and used high duty cycles. It's really not good to push the duty cycles but it's nice to know what the fuel system CAN support. 850/1300 probably would be enough fuel for a 35r on pump gas which shouldn't be over 450WHP and probably closer to 400WHP. I'm not saying it would be the best injector setup but it would probably be the easiest and cheapest for someone already with the 1300cc injectors. A small bump in fuel pressure doesn't cost anything and a retune will be necessary anyway. I don't think it's a bad way to go.

muibubbles

iTrader: (36)

raising the base fuel pressure would decrease gas efficiency bc now more fuel is flowing w/o any throttle? am i understanding this correctly?

"Check to see if there is an additional wire running from a 12v back into your gas tank."
i dont believe so... how would i go about running this wire? where do i need to tap into? is there d DIY somewhere?

i cant remember what my fuel pressure is off the top of my head but i think its 30psi at idle.. does that sound right? i gotta check what its at when you give it gas..

muibubbles

iTrader: (36)

ok so ive been thinking... say i did infact have 550/850 instead of 550/1300, would i still be able to touch 100% injector duty? (oh i believe im at stock Fuel pressure btw)

basically im thinking two things... the guy i bough the car from was wrong and i have stock injectors

OR

i have 550/1300 and they are crapping out...

opinions?

Dudemaaanownsanrx7

iTrader: (23)

Raising the base pressure will have no effect on fuel economy provided you retune and remove fuel. Yes there are several write ups on rewiring the fuel pump. Somewhere i have one that i wrote on here. It's really easy. Stock injectors would make more sense given your power level, thats about the level i maxed the stock injectors. One way to check would be to go into the injector setup with the pfc commander and see whats entered in. Although if the guy before you was under the impression he had 1300's and really got stock 850's then he prob mistakenly entered 1300's into the commander. Its pretty much impossible for an injector to be crapping out. They either work or don't. It is possible for them to get dirty but i doubt it would reduce flow enough to max them at 350hp without some noticeable drivability issues when they come online. The only way to know for sure what they are is get them flow tested and cleaned while they're out. It sounds like you're at stock pressure. If you disconnect the vacuum line with the car idling or, shut the car off and ground the f/p connector in the diagnostic port with the key on whatever pressure is on the gauge is base pressure.

muibubbles

iTrader: (36)

thanks dude... ive beginning to think i was mislead and that they are 550/850... looks like im going for over kill and gonna just do a 850/1600 so ill be set in the future..

so if i go with the kgparts rail and have the injectors, what else would i need?
i dont need the fancy bling blink ss braided lines so im assume the goodyear fuel line hoses would be suffiecient or do i need the high pressure injector hoses? and do i need the resistors? 1 or 2?

thanks a ton guys, im trying to get this done before deals so i dont ahve to worry about anythign...
-benny

Matt Hey

I believe Dale Clark had the best fuel pump rewire writeup on his site but it's been down for some time...

http://www.clubrx.org/

and the forum link with some useful info still...

https://www.rx7club.com/showthread.p...el+pump+rewire

I haven't done the mod but I did add another ground and cleaned the existing one which helps.

You NEED high pressure fuel injector rated hoses! Goodyear makes some that is good. I believe Autozone carries it and it IS expensive.

Most large injectors will need resistors with the PFC. The largest unmodified injectors that don't are 850cc like the stock FD injectors. You would need 2 resistors for the 1600cc injectors if you went 850/1600cc. You should do a lot of research before doing this like resistor size, Datalogit, wide band O2, negative lag for the 850cc primaries, and injector transition/staging for example.

I bet you have all stock injectors right now also. 356WHP is excellent on the stock sequential twins with just a minor street port. How much boost are you running to get that? I think I would bump up the fuel pressure a little bit to be safe and enjoy the car as is until something breaks .

muibubbles

iTrader: (36)

thanks man, im def gonna check those links out...
for the hp fuel injector hoses- they are a bit pricey i kindaaa have a hook up at autozone, maybe he can help me out...

as for resistor size, isnt there only one everyone sells which is the correct one? (kgparts site), widebands going on this weekend and hopefully tune next week, so whatever daves whips up is what ill be running!

356 is @ 1 bar

thanks for the advice! will report back..

Dudemaaanownsanrx7

iTrader: (23)

There are several different resistors people run. From none to 10 ohm. It depends on the resistance of the injectors. Most the bosch injectors i've seen are right around 5 ohms. Some peak and hold resistors are 2 ohm, and would need a higher ohm resistor. But for the bosch 5 ohm injectors 3 ohm resistors work well. Any high pressure fuel injector hose will work, the goodyear stuff is definitely better quality then most, and costly. You will also need to tap your primary rail to use hose barbs if it hasn't already been changed. You have an after market fpr so it's probably been changed around already. I will add this, i used fuel injection hose to save money and its working very well, but AN lines would make it easier to disassemble and reassemble over and over.

muibubbles

iTrader: (36)

i just checked out kgparts install/how to
http://www.3rdgenrx7.com/keithshowto.htm

and they used 10ohm resistors.. is it better to run high ohm then needed to play it safe?

im also gonna use the fuel injector hose bc i dont want to dish out the cash either... i heard its more tedious and no benefit besides over the hoses. plus i want everything in my enginebay black lol

tap my primary rails? shouldnt they already be tapped from KGParts?

last question, will the local autozone/pep boys have the npt>barbs fittings? if so is their quality sufficient enough? or should i go elsewhere?

Dudemaaanownsanrx7

iTrader: (23)

I would use the smallest resistor you can get away with. The larger the resistor the more sluggish the injector will react and your crossover point will be more stuborn to get right. With the bosch injectors which are right at 5 ohm i would use a 3 ohm resistor. I'm using a 4 ohm now which is what my kit came with. The rx7store kits come with 3 ohm and are basically the same kit. I thought you were using the stock primary rail since you said you're going 850/1600 but if you're going with keiths primary rail then yes its already tapped. The brass fittings at any automotive or hardware store will work fine. I got mine from lowes. On the secondary rail i used street 45's (male to female) and then a male hose barb screwed into the 45's. If you're still using the stock oil injectors this is the only way it will clear.

Dudemaaanownsanrx7

iTrader: (23)

Some people have no issues running without resistors. there have been at least 2 different mathematical way shown to reach the safe value for the injector circuits. One is based on the total wattage the drivers can handle, and the other is based on amps they can handle. I don't know which one is the correct way, but the first showed that 1 or 2 ohm resistors would be safe and no resistor was borderline safe, the second showed that 3 ohms are safe with the bosch injectors. So in either case 3 ohms is safe, with 1 or 2 ohm "probably" safe too.

The larger the resistor used the slower the injectors react and the less fuel they can deliver effectively making them smaller. So using the smallest safe resistor is beneficial.

Dudemaaanownsanrx7

iTrader: (23)

fuel pump rewire diagram, there are a few ways to do it, this is my preference.