chris_stampe

Hey,
My mods are listed below and right now I am running 10 psi. I am up to race a civic that I beat handily without his nitrous, but hes gettin his bottle refilled and wants to run em again. He was the fastest car around untill I beat him. It is fully built and alot of weight reduction. I have 2 720cc injectors right now and I was thinking about installing them and turning my boost up to like 13 psi or something. I do not have a fuel computer of any kind tho. Should I do this? Ive heard of people saying that they lost power by installing 720s, but I will need the xtra fuel to run that kind of boost, right?

Also what would be the max I could run on 720 secondaries w/ 550 primaries?

One more thing, I install the 10k resistors inline on 1 of the wires going to each secondary injector, right?

Thanks,
Chris

chris_stampe

Has anyone just installed the 10k resistors inline successfully or do most people just get the pre 87.5 resistor packs?

Do the resistors install inline on one of the wires going to an injector, or install running between the 2 wires? Thanks,
Chris

2a+RoN

you'd need to get some sort of fuel management to run those injectors otherwise it will run way rich. I am planning on installing some 750 seccondaries and using a s-afc to control them. I just need to figure out what part number the injector bungs are for when i do it. Any help???

NZConvertible

You need a fuel computer to do this properly, or you'll just run pig rich. Also, 13psi will put a lot of strain on the turbo, and it won't last long. That much boost is well past its efficiency peak, so it adds a lot of extra heat, increasing the chance of detonation. Your over-rich mixture might drown the detonation, but it's pretty crude tuning. The stock injectors are good for ~300hp as long as you upgrade the pump, which you have. Replacing the secondaries with 720's ups this to ~340hp. Yep. Personally I think it'd be easier to do this at the ECU end, rather than at the injectors.

rxse7en

NZ, I trust your judgement...you're confident that the stock 550s with an upgraded Walbro can handle up to ~300hp? I'm looking for around 280hp in a '91 with stock turbo, stock injectors, 3" DP/MP, SAFC, RB FCD and a Walbro 255. Think I'll be OK?

Brian

BlackRx7

TEDs site says so too, and my car was runnning good and fast before I put my 720s in, now my car is sittng at a shop wthout an engine

Just get a walbro and maybe an FPR and be done with it, as far as you stay wth the stock turbo..

RETed

I'm not exactly sure what you're trying to say, but I think there is only one section which I quote a HP figure, and it's not 300hp.

http://fc3s-pro.com/TECH/MODS/FUEL/inj.htm

BTW, it's *10*ohm, not "10K" ohms.


-Ted

rxse7en

From Ted's site:

"Keep in mind, the stock fuel injectors (4x550) can sustain about 250bhp at the flywheel under stock fuel pressure (35psi)._ 4x720 will support a little over 300bhp at the flywheel at stock fuel pressure. "

I'm starting to believe that any boost mods should be accompanied by an injector upgrade. If a dp/mp combo with an FCD can increase HP by 40+ you're already getting into max duty cycle on the stock injectors. Throw in a streeport and TID mod and you're really pushing the envelope. Of course, I'm basing this on research and not experience and would love to hear from the latter.

B

chris_stampe

Alright first of all. I know that the turbo isnt very efficient past about 12psi, and that it will shorten its life. I dont care about the turbo going, because it isnt worth much anyway, and I have a rebuilt s5 one just waiting for a manifold and possibly a compressor upgrade.

By the first reply it would seem that I can run 13 psi on the stock injectors. But then someone else said that they max out at 250fwhp. Who else has an opinion on how much the stock 550s can handle?

Also, I have a fmic, so the extra heat caused by the turbo shouldnt be as much of a problem, right?

Straight up, will raising my boost past 11 psi to say 13 or whatever yeild me any gain? Or will the rising inefficiency of the stock turbo outwiegh the higher boost?

BlackRx7

hehe sorry I got alittle confused, funny its like you know when someone says your name, oh the reason why my car is without a because after I installed the 720s turned up the boost to 13-14 psi and kept getting times slower than when I had my stock injectors first run I got a 14.7, best run with my 550s was 13.8, I started leaning out my car and get it down to 14.1 with the 720s thats when she blew, I think I may have run a mid to low 13 if I finished the run, I had a 2.0 60ft and ran a 14.1 at 92 mph on the apex seal cracking run....shoulda stayed with the 550s

NZConvertible

You need 8cc/min of fuel per kW of power, so 4 x 550 = 2200cc/min; 2200 / 8 = 275kW = 378hp. Max safe injector duty cycle is 80%, so 369 x 0.8 = 295hp. You need to maintain adequate fuel pressure at that flow, which the stock pump cannot, but the Walbro can. This also assumes you're not using heaps of boost to get your power. I think the injectors will be the least of your worries. I highly doubt you'll make 280hp from the stock turbo even with heaps of boost. With high boost comes high intake temps so you'll need to drown it in fuel to prevent detonation, and that may be beyond the stock injectors. You should look at compressor and intercooler upgrades. Also, with a 3" exhaust you'll need to port the wastegate to keep boost under control.

Ni5mo180SX

This ones similar to the above situation and im sorry for the repetative questions but

With a turbo back exhaust, FCD, Walbro 255, ported manifold and ported wastegate, the general concensus is that im ok with the 550cc injectors. Can I safely get by on the 550s? Im not planning on increasing power/boost anymore so then what it goes to after the exhaust.

rxse7en

UPDATE: The engine is rebuilt, stage 2 streetport and ported wastegate. I'm still breaking it in and when complete I'll install the DP/MP, Walbro, FCD and SAFC. I'm still not confident that the stock 550s are going to be "safe." Any other input?

Brian

NZConvertible

You're still runnning the stock turbo right? As long as you can control the boost I think you'll be okay, since the compressor isn't good for much over 250hp anyway.
Since you have to get the S-AFC tuned anyway, the first thing you should do is get onto a dyno and see what's actually happening. You'll see if it's starts to lean out before it can do any damage, and can decide if you need bigger injectors.
If you plan to upgrade the turbo later (i.e. 300+hp), then go ahead and do it. There's no problem with bigger injectors as long as they're properly tuned.

Jahoo88

I just put gsl-se (orange top) into my stock turbo s5 t2. it doesnt seem to smoke black much over 3500 with these injectors untuned. I used 10 ohm resistors on the green wire.

I guess i should get an s-afc and boost controller now and tune it on a dyno.

rxse7en

Stock Series 5 turbo with ported wastegate. I'm hoping to keep the boost down to ~10#. I'm not as concerned with power as much as I am with safety. Unlike the NA 7s I've owned, I drive this TII very conservatively. After break-in, I'll mod the car then get it on a dyno and see where we're at with A/F.

Thanks again Jason,

Brian