Does anyone know what size injectors a stock 04 GT has. Also, would it be worth it to put larger injectors in my stock motor? im planning on running the 70mm throttle body and plenum combo.

 

19# is stock. Adding bigger injectors doesnt add any hp. they only feed the hp you make.

And the 70mm Tb and plenum are a good n/a mod.

 

I beleive he wanted to know if he should get the bigger injectors to compensate for the higher air flow.....

I have the 70mm T/B and plenum combo and im still using the 19# stock injectors.......but I need to get my car dynoed with a air/fuel monitor and see if the ratio is still good................

 

no...i have seen people get new MAF meters tuned for 24#, but it is worthless on a stock motor

 

dont get bigger injectors unless you have heads and cams, or a power adder

 

Yup. Stock injectors can support about 350 rwhp. Though some say only 300. Either way, you are fine. Going with bigger injectors will just cause you to go rich and loose power unless you have you tune compensated.

If you have plans for future mods and get a good buy on some 24 pounders, you could always buy them and save for later. I still have the stockers with my bolt-ons and a 80 - 100 shot of nitrous. While on the raged edge of safe, they still support my power output.

 

I just got the car back from having the Cobra dyno tuned on the nitrous...and aside from the Venom Nitrous kit not working properly, Jerry @ SCT says i've run out of injector (Cobra's have stock 24 lbers) at 333rwhp and 389 rwtq. I was a little pissed that this was all she put down on the spray, and this was with 1000 psi bottle pressure. I think i'm only seeing about a 50 shot though, and jumping to 42lbers and a LMAF or SCT Big Air meter will solve my problems.

I'm going to get on the horn monday to venom performance and try to straighten out what's going on with the system. The fuel enrichment was not working, so the car saw 15:1 A/F on the first nitrous pull...and Tim got out of it early enough.

I've probably been seeing this A/F the entire time on the spray...and never knew it so something is up. The Lean condition safety shutdown was not working.

Philip K.

 

wow. good thing you got out of that before you caused some damage. its hard to pinpoint a given rwhp level for injectors, as every application is different, and with power curves, timing changes, and spark patterns differing, fuel injector load can vary. its best to get your car on a dyno anyway if your at a power level that can constitute more fuel, to see what injectors suit you

 

Let me know what the Venom folks tell you. I have been running with a VCN-1000 since last October with no issues. I have never had it on a dyno, but I always check my plugs between each bottle.

 

I'll post my results here. I am a little perplexed by the whole thing. I have a few of my EE buddies at school that I'm going to have tear into the module and look a EEC schematic of the Cobra to see what this black box really does. Everything looks good on paper. But the Fuel enrichment, and Lean shutoff are DEFINITELY not working. I suspected a wiring problem...but I was quite thorough with the installation, and the system definitely is injecting nitrous...so the only wires that could be causing a problem would be the connections to the fuel injectors, but I dunno.

I also read somewhere on here where a gentleman purchased custom larger jets from venom-performance... a .060" jet, and a .065" jet. He stated that the .060" jet was a 100 shot, and the .065 jet was a 125 shot.

I was under the impression the large clear aluminum nozzle (.055") supplied with the kit was the 100 shot pill. This would explain a bit about why the car isn't seeing as much power as it should, but something better get sorted out quick, b/c im getting a little frustrated.

I should be seeing at least 4-5 more mph in the 1/8th with my race weight, and 60 more rwhp and tq with a 100 shot. I think it'll just take some working out, as noone i've ever heard of has run this kit on a Cobra. So I'll be a guinea pig.

Dyno sheet and Video's will be posted by the end of the week.

Philip K.

P.S. Get her on the dyno if you can...I'd like to have something to compare to. And then I'd be able to see if it's a wiring problem I may have. Besides...a tune would be worth 20-30 hp on a nitrous tune...not to mention the insurance.

 

I believe the 04's may have 21# injectors (can't remember where I read this - most late models run 19#, as does my 02 GT vert).

To compute injector size, I got this info from Summit:

"Calculating Fuel Injector Size
Here is the formula for calculating injector size in pounds per hour:
Injector lbs./hr. = horsepower x BFSC/number of cylinders

BFSC is short for Brake Specific Fuel Consumption, which is the amount of fuel required to produce one horsepower. According to Accel, a BFSC of .45 is a good general figure for normally aspirated engines, and .55 is good for supercharged engines.

Let’s do a calculation for a 400 horsepower, unblown V8 engine:
Injector lbs./hr. = 400 x .45/8
Injector lbs./hr. = 400 x .05625
Injector lbs./hr. = 22.5#" - summit racing"

Hence the stock 19# injectors, which give some headroom in a 260hp stocker, will fall short somewhere above 330hp:

Injector lbs./hr = 330 x .45/8, or 330 x .05625 = 18.6#

Personally, I've always felt these numbers were a bit optimistic, since 100% efficiency/consumption of fuel is rarely achieved. (quote from one of my other posts).

I find this info very valuable when evaluating injector sizing. It is something of a backward way of doing it, but it really does work.

In the case of simply bolting on a plenum/tb combo, I doubt this will need any upgrade to larger injectors. You'll be lucky to get 15hp or so from this upgrade (I've got the 75mm combo, and I netted about that much). Unless you're going to go through the complete engine (ported heads, big cams, long tube headers, performance tune, etc, etc), leave the injectors alone for now.

Hope this helps.

tripleblack

 

Ulp. Just remembered - I think the 05's have 21#.

tripleblack

 

I got this data from Summit:

Injector lbs./hr. = horsepower x BFSC/number of cylinders (.55 for sc). If we think positive, you should be running 500hp+ at the flywheel soon...

Injector lbs./hr. = 500 x .55/8
Injector lbs./hr. = 500 x .06875
Injector lbs./hr. = 34.375#

Since this is an optimisitic method for calculating injector size, and a modest estimate of your motor's power potential, I believe you will probably need 42# injectors, particularly with the nitrous.

As for the problem with your lean condition, perhaps the knock sensor was cutting in and saving the situation before it went critical? (Not an opinion here - just a speculation.)

Luck with your car - wish I had your problems, by the way...

tripleblack


[QUOTE=Lightning247]I just got the car back from having the Cobra dyno tuned on the nitrous...and aside from the Venom Nitrous kit not working properly, Jerry @ SCT says i've run out of injector (Cobra's have stock 24 lbers) at 333rwhp and 389 rwtq. I was a little pissed that this was all she put down on the spray, and this was with 1000 psi bottle pressure. I think i'm only seeing about a 50 shot though, and jumping to 42lbers and a LMAF or SCT Big Air meter will solve my problems."