Hi guys, just a reminder that the 60# injectors flow is in fact 63# @ 43,5 PSI. It is exactly FIFTY PERCENT (50 %) more than the 42# injectors.

I don't know why people jump on them so fast. There is some other alternative like the 50# or the 55# injectors.

- Remember that the stock ones are 34,1# (355 cc per minute) rated @ 43,5 PSI.

- The 42# injectors flows 23% more than the stock one.

- The 50# injectors flows 46% more than the stock one. This is the maximum supported by the HPTuners injectors table for the LSJ. I would be curious that someone show me a street Cobalt (except for a few one turboed and cammed, ported ...) that puts down 40% more WHP than stock on the same dyno. Just remember that no one trapped more than 109 ishhh MPH on the quarter mile ... vs roughly 98-100 MPH stock.

- 55# injectors flows 61% more than the stock one.

- 60# are in fact 63# injectors and flows 85% more than the stock one.

What are your thoughts ...

 

i personally think this might fall on deaf ears, or blinded eyes. which ever you prefer.

there is the same type of discussion going on right now on the rlf forums. now, my idea is this. with the stage 3 kit, and a dry shot of 50 hp. how are they surviving? did gm cranked the fuel pressure while in nitrous mode to compensate for it?!?! most dry kits do this in general, we won't know for sure unless we get someone from the build team for the stage kits to answer this question. you have a better chance of willing the lottery, so don't hold your breath.

unless the hpt people get a wild hair up their ass and crack the stage 3 ecm. we probably won't know the answer.

 

241whp with airbox mod and no tune stock injectors and whatnot. (injectors were over 100% idc on a 54 degree day)... same dyno with all mods in Vb garage... 296. I dunno what percentage that works out too.

 

Thanks. It is that kind of affirmations that we need to realize the true numbers (I'm not talking only about the injectors but I'm talking about the dyno numbers and the limited LSJ potential on the stock head//M62 combination).

You dynoed your 06 SS to 241whp stock (but the airbox mod) on a Dynojet. It makes sense cause Fast06SS dynoed his 06 SS to 230whp stock (dynojet). It also makes sense cause I know someone who dynoed his 06SS bone stock to 206whp on a Mustang dyno.

And after all the mods in your Garage, you dynoed to 296whp (same dynojet). Don't get me wrong it is a pretty good number and improvement running the Eaton, but 296 divided by 230 equals "only" 28% more WHP over stock. Again this is very good, but why to run injectors like 85% larger.

Then one of the problem is the differential pressure. I would be curious to upgrade the spring in the fuel sender unit (inside the thank). That one regulate the pressure to a steady 55-60 PSI.

 

When I got concerned about running 42's w/ a 2.8" pulley. I went to two different shop owners who tune cars for a living, both of which have very reputable shops and both assured me that they went through these same calculations and were confident that the 42's were good to 300whp...

 

where can i get 50# injectors?

 

http://www.cobaltperformanceparts.co..._Set_Of_4.html

 

Thank you, uhh, what brand are those?

 

For 300 whp:

300 x 1.15 = 345

(345 x .55) (4 x .85) = 55.8


For 250 whp:

250 x 1.15 = 287.5

(287.5 x .55) (4 x .85) = 46.5

Recommended injector sizes for horsepower. This is a basic calculation, but for sure not many ppl running 300 whp, so no huge need for 60's

 

42's good for 300? interesting and I have a question I always wondered ... if hpt was reading over 100% duty on an injector how is it that the injector is flowing at a rate higher than what it was designed to use? I'm a noob to tuning and I always wondered that.

 

You're all over the place in this one, my thoughts in bold.

It doesn't. Its only being commanded in excess of 100%. It will never actually flow more than 100%.

Because its a basic calculation its assuming the amount of boost in both cases is the same as well as max rpm. On our cars, that isn't the case and skews those calculations.

I have logs of a turbo redline exceeding 100% duty cycle on 60s at 11.7 a/f and 7400rpm and dynoed ~310 mustang whp with a stock top and bottom end. This is a lot more efficient compressor so if you're still using an overextended supercharger, you'll hit this ceiling earlier.

 

If that was 310whp on a mustang then that's easily 350whp on any dynojet...

 

and this is why people freak when they see the a/f ratio spike after 6k when trying to run a 2.8 and 42's, while trying to command a 11.3 a/f. the injectors simply can not do it.

it seems that 50's with a 2.8 would be a decent upgrade, but at the same cost, no one runs them. i believe more people run 60's because it is flat out easier to get ahold of a 60lb map to tweak to their liking.

 

60s or 650s are also much easier to find as they're popular upgrades for other cars. The difference between a 42 and 50 isn't large enough to justify upgrading imo if the next step up will work without issue.

Even if you are using the largest injector possible, you'll still be spraying the same amount of fuel into the manifold as the same amount will be commanded regardless of injector size. The limiting factor is how small of an amount can be sprayed at idle or low map conditions, which really isn't a problem afaik with 60/650s.

 

this is true. speaking of which, you get that thing i sent ya
lol

ya know, 60lb injectors will support over 850 crank on a v8. why in the hell is it barely doing a damn thing over 350 on a 4 cylinder.

oh thats right, the v8 set up is a return style. i guess the question being is simple, why do people keep playing with huge injectors and trying to bandaid the problem?!!?
you're only going to make as much power as your weakest link will allow.

 

I think theres some things not being taken into consideration here

I agree throwing 60lb injectors in the car which the PCM cant properly run in HP tuners is kinda dumb, 50 or 55lb would be a better choice. Why put something into the car you cant run right? The only way 60lbers are justified is if your running a stand alone.

All these calculations that ppl are making like 42lb injectors running 300hp and such, at what kinda AFR is it at? Its a well known fact that on a stock blower you cant run upper 11s on a stock motor with the Eaton and survive. #4 will go boom every time, these cars have to be run rich in the low 11s on AFR therefore a big injector must be used that in many other cars will support more horsepower.

 

i run 11.9-12.0 a/f with the eaton.
then again, i also run 25 degree's of timing from 2500-7200.

 

Been running 60s in my car for over a year with no problems with commanded to actual air fuel ratio less than 3% error. Amount of air being ingested by the engine justifies the larger injectors. Using too small injectors is kinda dumb.

 

My car runs great on the 60s, no issues at all.

 

I agree to a degree. i seem to have the highest numbers on stock injectors to date and actually i know i can get higher. 262 whp 215 TQ 6800 redline 21* timming stock injectors. I have my redline at 7200 right now guarrented im up around 267-270 on this same tune. The other tunes paul has needs race gas to even enduldge the timming he has on them. If i can get here on stocks with a 13.5 a/f MAYBE someone can get to 300whp on 42's but things would be looking real ugly on there datalog

 

it's a never ending battle.

 

Best solution in any case is to upgrade to a return style fuel system. Takes the increase in manifold pressure out of the equation and is fairly easy to do.

 

if some one made a kit i would be all over it. Cause it ain't lean killing cobalts all by its self or else my car woulda have been dead 8 times over already. 13.5 a/fs are outta control for a boosted application.

 

what is this style you speak of mr miagi

 

this is true. rail change, regulator change, added fuel line, fuel pump change.

OR, just add a return line from the rail back. not sure how the car would enjoy this idea. let alone being converted to return style. this would also skew the numbers for the injectors as well.

well crap!