Bosch 42lb Injectors, why waste the money?

[tsbpenguin]

So for the last 6 months or so I've been casually looking at fueling options on our cars. While a lot of people are opting for the larger 60lb injectors, it seems like a substantial amount still end up with the 42lb injectors. Having come from the mustang world before this, I knew that the 42lb green tops are a very popular upgrade for mustang guys. You figure that they're ~$50 a piece, so for 6 you'll end up spending over $300 on a set.

With my involvement in the mustang world before, I knew that the "budget" alternative to buying brand new bosch injectors, was getting a set of used stock Terminator (03/04 Cobra) 39lb injectors.

When you compare, you'll see that both injectors use the same clip. Also, although the cobra injectors are "39lb" that's actually 39lb @ 39psi fuel pressure. The 42lb injectors are 42lb @ 43.5psi fuel pressure. When you do the calculation for the 39lb @ 43.5psi, they're actually 41.2lb injectors. That would make them 47.9lb @ 4bar (58.8psi) fuel pressure (our stock fuel pressure), and they'd be 53.5lb with a 5bar (73.5psi) fuel pressure regulator.

PROS:
-You can pick up a low milage set for ~ $100-$150 (Click Here)
-You get 8 in a set rather than 6. That way even if 1-2 injectors is, or ever does go bad, you'll have spares.
-They have a good track record with reliabillity in older mustangs, v6 mustangs, focus, etc.

CONS:
-I've seen the flow pattern of 42lb bosch injectors, but can not find any pictures of the flow pattern of the 39lb cobra injectors, so I can't say which has a better flow pattern for our cars.
-As with buying any used parts, there's always a chance of getting your product in sub par condition.


This is in no way meant to be the end all injector solution, but it's just what I've found in my research. If any of my information is incorrect, please feel free to correct it. If anyone can chime in on the flow pattern of the 39lb injectors, that would also be helpful.

[hercfe]

The question shouldn't be a matter of why not. You need to base your fuel injector size around your horsepower goal. Plan on .6 BSFC (brake specific fuel consumption) and 80-85% duty cycle MAX. Those terminator injectors are only good to about 350 bhp. that's like basically s1 and full exhaust ish on a 2.7T. This is really no different than the bosch 42 lb injectors. I've always preferred the budget method myself, as long as it was done right the first time. With an S4, the option to make BIG power is always there. That's why most guys use 60lb injectors. It just makes sense when it can be tuned with a flash.

The terminator injectors flow pattern is much better than the standard bosch 42 lb injectors FYI, and for a basic bolt on car, should be great. The reason you can make more power with those on the stang is; #1 you have 2 more injectors, and 2 the turbo compounds the need for fuel. Naturally aspirated/low boost fuel consumption is a linear curve. Forced induction is exponential when you start raising the boost because you are now using fuel to cool the engine as well. Your 2.7T probably makes from the factory around 600 horsepower, but over 50% of that is lost in heat exchange to keep the engine cool.

[tsbpenguin]

The question shouldn't be a matter of why not. You need to base your fuel injector size around your horsepower goal. Plan on .6 BSFC (brake specific fuel consumption) and 80-85% duty cycle MAX. Those terminator injectors are only good to about 350 bhp. that's like basically s1 and full exhaust ish on a 2.7T. This is really no different than the bosch 42 lb injectors. I've always preferred the budget method myself, as long as it was done right the first time. With an S4, the option to make BIG power is always there. That's why most guys use 60lb injectors. It just makes sense when it can be tuned with a flash.

The terminator injectors flow pattern is much better than the standard bosch 42 lb injectors FYI, and for a basic bolt on car, should be great. The reason you can make more power with those on the stang is; #1 you have 2 more injectors, and 2 the turbo compounds the need for fuel. Naturally aspirated/low boost fuel consumption is a linear curve. Forced induction is exponential when you start raising the boost because you are now using fuel to cool the engine as well. Your 2.7T probably makes from the factory around 600 horsepower, but over 50% of that is lost in heat exchange to keep the engine cool.

Appreciate the informative response! I wasn't really inquiring for myself because I'm going larger than k04 and these wouldn't come close to fulfilling my needs. Just a general inquiry out of curiousity.

[AudiSportB5S4]

Some hard data for you via ECUx logs.... You can see how the 42s run @ 90% IDC, whereas the 60lb injectors whether they are Siemens Dekas or the new Bosch EV14s they will hit 60-70%.

42lb. Bosch Green Giants


60lb/hr Siemens Dekas

[tsbpenguin]

Some hard data for you via ECUx logs.... You can see how the 42s run @ 90% IDC, whereas the 60lb injectors whether they are Siemens Dekas or the new Bosch EV14s they will hit 60-70%.

42lb. Bosch Green Giants


60lb/hr Siemens Dekas

Thanks for the hard data. What was the setup of the car for these graphs?

[The_Jerbel]

The 42lbs GG's are good for a heck of a lot more than 350bhp, that's for sure

[AudiSportB5S4]

Thanks for the hard data. What was the setup of the car for these graphs?

Good call! My car is PJ K04s, the second graph with the 60's is the same PJ K04s, but running meth injection as well.. Everything else is the same as far as exhaust, intercoolers, etc. That's all in my signature

[hercfe]

The 42lbs GG's are good for a heck of a lot more than 350bhp, that's for sure

Not denying that...but they are running at maximum duty cycle above 350bhp--i should preface that with at 3 bar, so at 4 bar they will support about another 25-40bhp. Of course, its all up to you if you are willing to do that or not. Chances are it won't hurt the injectors, but if one fails because of the extreme IDC you are going to hear a very loud bang followed usually by several tears. Can it be done? Yes. Has it been done before? Yes. Should it be done? Eh...not on my dollar, especially when 60lb injectors are so readily available, and cheap.

[AudiSportB5S4]

The 42lb setups for fueling kits run the injectors using the stock 4 bar FPR, so 520cc/50#

[tsbpenguin]

Not denying that...but they are running at maximum duty cycle above 350bhp--i should preface that with at 3 bar, so at 4 bar they will support about another 25-40bhp. Of course, its all up to you if you are willing to do that or not. Chances are it won't hurt the injectors, but if one fails because of the extreme IDC you are going to hear a very loud bang followed usually by several tears. Can it be done? Yes. Has it been done before? Yes. Should it be done? Eh...not on my dollar, especially when 60lb injectors are so readily available, and cheap.

Hmm I see what you're saying, but don't think you're 100% accurate on your numbers. AudiSportB5S4's graph shows that he was at 90% duty cycle on 42lb injectors with pjk04 setup. That should be well over 400bhp, whereas according to your numbers, they would be maxing around 390bhp.

[tsbpenguin]

The 42lb setups for fueling kits run the injectors using the stock 4 bar FPR, so 520cc/50#

Any clue what the duty cycle would be on 5 bar? 80%?

[The_Jerbel]

Not denying that...but they are running at maximum duty cycle above 350bhp--i should preface that with at 3 bar, so at 4 bar they will support about another 25-40bhp. Of course, its all up to you if you are willing to do that or not. Chances are it won't hurt the injectors, but if one fails because of the extreme IDC you are going to hear a very loud bang followed usually by several tears. Can it be done? Yes. Has it been done before? Yes. Should it be done? Eh...not on my dollar, especially when 60lb injectors are so readily available, and cheap.

I've run over 400 at the wheels using 42lbs GG's on the stock 4bar FPR at around 85-90% IDC, and run setups like that for 3 years with no problems...

I'm not debating the virtues of running 60lbs injectors on Stage 3 setups, because they are a great choice, aside from the extra lumpy idle, but the GG's will get the job done just fine, as well.

Now for anything bigger than K04's, 60lbs injectors are the clear winner.

[The_Jerbel]

Hmm I see what you're saying, but don't think you're 100% accurate on your numbers. AudiSportB5S4's graph shows that he was at 90% duty cycle on 42lb injectors with pjk04 setup. That should be well over 400bhp, whereas according to your numbers, they would be maxing around 390bhp.

Just one thing to add here- your IDC really depends on MAF values, both of which will be major factors in determining power output.

[mrpeterparker]

Those terminator injectors are only good to about 350 bhp. that's like basically s1 and full exhaust ish on a 2.7T.

are you high? what stage 1 s4 has 350 brake horse power? must be a super happy dyno

[NogaroWonda00]

Tyler you're getting 84lb and two walbros for e85.. At least you will after mines done ;)


PS I went out last night to denver, off arapahoe, shit was crazy lol

[tsbpenguin]

Tyler you're getting 84lb and two walbros for e85.. At least you will after mines done ;)


PS I went out last night to denver, off arapahoe, shit was crazy lol

Haha ya I'm definitely gonna need some serious fueling, just thought i'd open the door a little for some more options for stage 3 guys.

Is that where they do the runs downtown now? Run anything good?

[BITRBO]

Some hard data for you via ECUx logs.... You can see how the 42s run @ 90% IDC, whereas the 60lb injectors whether they are Siemens Dekas or the new Bosch EV14s they will hit 60-70%.

But wait: Didn't you say the 2nd log (60lb Siemes/Dekas) also had meth injection? Cause meth will increase the octane rating of the fuel, so won't this affect IDC? Just curious.

BTW, are you running the Siemens or the EV14s now? If so, how are they around town (idle and cruising)? Any roughness? TIA!

[NogaroWonda00]

Haha ya I'm definitely gonna need some serious fueling, just thought i'd open the door a little for some more options for stage 3 guys.

Is that where they do the runs downtown now? Run anything good?

Yeah I guess. Like that ihop parking lot overlooks i25. I got a couple, it was a 3 way, me vs a supra powered Lexus gs 430 with a 70 somethin mil, vs a eg coupe built gsr 35r

the civic runs mc-tens so he flew by like I was standing still, but I spanked the gs pretty good. There was cams in both of the other cars.. I'm tryin to track down the vids lol

[The_Jerbel]

But wait: Didn't you say the 2nd log (60lb Siemes/Dekas) also had meth injection? Cause meth will increase the octane rating of the fuel, so won't this affect IDC? Just curious.

BTW, are you running the Siemens or the EV14s now? If so, how are they around town (idle and cruising)? Any roughness? TIA!

The absolute value of the AFR will decrease with meth, but the IDC shouldn't change much. The richer mixture will cause the O2's to read slightly higher, causing the LTFT's to decrease slightly, which will, in-turn, cause the ECU in open-loop to decrease the injector on times very slightly, which will cause the IDC to decrease VERY VERY slightly. But it won't be much, like I said before.

[BITRBO]

The absolute value of the AFR will decrease with meth, but the IDC shouldn't change much. The richer mixture will cause the O2's to read slightly higher, causing the LTFT's to decrease slightly, which will, in-turn, cause the ECU to decrease the injector on times very slightly, which will cause the IDC to decrease VERY VERY slightly. But it won't be much, like I said before.

Got it. I figured one has to affect the other, but I guess not that much....

Dude... So glad you're back!! You got PM

[AudiSportB5S4]

But wait: Didn't you say the 2nd log (60lb Siemes/Dekas) also had meth injection? Cause meth will increase the octane rating of the fuel, so won't this affect IDC? Just curious.

BTW, are you running the Siemens or the EV14s now? If so, how are they around town (idle and cruising)? Any roughness? TIA!

Yep Jerbel already got to your first question, but yep I switched it up to BOSCH EV14s... They are amazing. Completely different animal than the Dekas. Idle like stock very smooth, part throttle is insanely smooth for the amount of injector it is. I recommend them over Dekas if you have to choose.

[BITRBO]

^Cool, thanks for the feedback!

[tsbpenguin]

Yeah I guess. Like that ihop parking lot overlooks i25. I got a couple, it was a 3 way, me vs a supra powered Lexus gs 430 with a 70 somethin mil, vs a eg coupe built gsr 35r

the civic runs mc-tens so he flew by like I was standing still, but I spanked the gs pretty good. There was cams in both of the other cars.. I'm tryin to track down the vids lol

Nice dude I hope you track that shit down, I'd definitely like to see it.

The absolute value of the AFR will decrease with meth, but the IDC shouldn't change much. The richer mixture will cause the O2's to read slightly higher, causing the LTFT's to decrease slightly, which will, in-turn, cause the ECU in open-loop to decrease the injector on times very slightly, which will cause the IDC to decrease VERY VERY slightly. But it won't be much, like I said before.

Running E85 is the opposite right? IDC's would increase even though the AFR decreases?

[The_Jerbel]

I don't think so. I haven't used E85, but afaik, E85 just has a much lower stoich value, so needs to run a lot richer, which will increase IDC a bunch over regular gas.

[CTS Turbo]

Just FYI bosch stopped making the 42lb green tops. They do sell knock off Chinese ones, they have the STS turbo systems logo stamped in them, because STS was planning to make their own.

Anyway, if anyone's looking for new fueling we have good pricing on 630cc and 415cc green giants which are compatible with most of the tuners software