+40 injector HP limit

[Directconnection]

The old consensus used to be that the +40s couldn't support much more than 300whp. Rick Diogo made over 400whp on his T-III back then on +40s in which some denied his claims, but the BFSC of the T-III was better, so some figured to be possible.

I have seen the +40s support 344whp where the ignition was more of a culprit in their limitation.


So, with all the new technolgy out ther ein the form of many people doing their wn cals these days and with chem and d-cal... what have people gotten out of their +40s for max. HP?

I am thinking I should have stepped up to the 72pph a while back for this project I am into and don't want to be cut shortat 330whp.

[rbryant]

From what I have read, 4 valve engines have a lower BSFC than 2 valve engines so you can get more power out of smaller injectors if you have a more efficient engine...

Our +40s are rated @ 55psi so they actually more like 46.25pph @ 43.5 psi if using most calculators...

Mitsu eclipse blue top injectors are 450cc @ so they are a cheap way to get to ~48pph @ 55psi injectors.

Here are some equations use:

http://www.rceng.com/technical.htm#WORKSHEET
http://rbracing-rsr.com/fuelinjectors.htm

After that you need to have a good idea of what your real BSFC is which will require some dyno time... Keep in mind that you shouldn't pass 85% duty cycle regularly on injectors.

-Rich

[8valves]

I ran clean on +40's at 370 whp/395 wtq for quite some time. I'm pretty sure it was getting kinda ragged up there though, and since when it got cold I popped a headgasket I think that was a good indicator of the limit.

[bn880]

If you raise fuel pressure and then calibrate for it you can easily go upto 450+ at the wheels, it just starts to get scary over 100psi. (hose wise)

65-75psi base or RRR

[Speedeuphoria]

and the fuel pump starts falling on its face at those pressures

[cordes]

and the fuel pump starts falling on its face at those pressures

+1.

The +40s are great and can be pushed very far.

The thing that turns me off to them when a very high HP setup is concerned is that the pump will struggle to keep up with them. 55PSI +25PSI will give you 80PSI which is at the limit of the walbro 255 that most of us run from what I have read. I know that there are a lot of guys running 28+PSI of boost, which to me can be a bit scary.

Also, if you look at the duty cycle of the injectors it gets up there pretty quickly. I believe that with a redline of even 6300 you will be over 80% duty cycle at only 20-22PSI, but it has been a while since I have looked at it.

I really think each person needs to look at the DC and the overall FP they will be running at their target boost level to determine if they are comfortable with the safety factor they provide.

[Directconnection]

I want to stay just shy of the 3-bar on my T3/T4. But maybe I may need to do the 5th injector trick once I get around 25psi.

Engine is far from finished so I am just getting a collaborative mutual agreement on the limitations of the +40s.

[cordes]

I want to stay just shy of the 3-bar on my T3/T4. But maybe I may need to do the 5th injector trick once I get around 25psi.

Engine is far from finished so I am just getting a collaborative mutual agreement on the limitations of the +40s.

add some alky.

[8valves]

+1.

The +40s are great and can be pushed very far.

The thing that turns me off to them when a very high HP setup is concerned is that the pump will struggle to keep up with them. 55PSI +25PSI will give you 80PSI which is at the limit of the walbro 255 that most of us run from what I have read. I know that there are a lot of guys running 28+PSI of boost, which to me can be a bit scary.

Also, if you look at the duty cycle of the injectors it gets up there pretty quickly. I believe that with a redline of even 6300 you will be over 80% duty cycle at only 20-22PSI, but it has been a while since I have looked at it.

I really think each person needs to look at the DC and the overall FP they will be running at their target boost level to determine if they are comfortable with the safety factor they provide.

Absoultey correct. Raising the pressure excessively is generally not a good idea.

[Directconnection]

add some alky.

I'd rather not. One less link in the chain, the better. Besides, isn't the purpose of alcohol injection to fight off detonation by increasing the octane so to speak and not the other way around... to add fuel to run more boost?



BTW... the how many WOT runs can you make with the alcohol injection?

[cordes]

I'd rather not. One less link in the chain, the better. Besides, isn't the purpose of alcohol injection to fight off detonation by increasing the octane so to speak and not the other way around... to add fuel to run more boost?



BTW... the how many WOT runs can you make with the alcohol injection?

It depends on the nozzle size, alky tank size, and how long your WOT runs are. IIRC Carl was filling his tank every fourth pass, but he was also pulling fuel to accommodate the added alky.

Honestly, if I were not intending on running alky with the same goals as yourself, I would get some larger injectors.

[Directconnection]

I can't get a damn SBEC 2.5 G head cal for +40s.... I doubt I can get one for 72pph.

My old ride at 15-16psi... I was kinda into the boost alot. I guess I'd run empty real quick at 25-28psi.

[cordes]

I am sure that there is someone who could put together a cal like that for you. The injector change really should not make that much of a difference.

[GLHNSLHT2]

Rick D was running a Masi, not a T3.

[TurboJerry]

I can't get a damn SBEC 2.5 G head cal for +40s.... I doubt I can get one for 72pph.

My old ride at 15-16psi... I was kinda into the boost alot. I guess I'd run empty real quick at 25-28psi.

At 55 psi and 100% DC, 340 hp is on the edge. There is no room for error. This is Assuming a .62 BSFC. 72 or 83 pph injectors are much better considering there is only 4 injectors. I found the Walbro to loose alot of steam at about 90 psi fuel pressure.

[contraption22]

Why not run 72lb injectors on your 52lb cal at lowered fuel pressure? Its easier on the pump to not have to run sky high fuel pressure, and you have extra head room.

[TurboJerry]

Why not run 72lb injectors on your 52lb cal at lowered fuel pressure? Its easier on the pump to not have to run sky high fuel pressure, and you have extra head room.

Yup, that would work, but he may need 25 psi static fuel pressure to run clean and smooth while "cruising"!!!!!!

[cordes]

Yup, that would work, but he may need 25 psi static fuel pressure to run clean and smooth while "cruising"!!!!!!

Yeah, you would have to drop that fuel pressure pretty low. It is an option, but I would rather scale the fueling tables.

[Directconnection]

Rick D was running a Masi, not a T3.

Bzzzt! It was on his IROC R/T. Rick owns masi and T-III components galore.

[rbryant]

Has anyone tried 84 RX7 injectors? They are supposed to be 680cc and low impedence...

That would support 400HP at only 43.5 psi.

I have seen remaned injectors for around $30 plus a $12 core on them from one of the discount car parts sites.

-Rich