KirkF

What is the flow rate of a stock 964 injector?
(cc/min or lb/hr)

What is the stock fuel pressure? 3.8 bar?


Thanx
Kirk

JasonAndreas

Check out Stan Weiss' -Electronic Fuel Injector Flow Data Table, he has data for every injector known to man.

0-280-150-731 :

18.45lbs/hr - 193.9 cc /min - 139.5 grams /min

KirkF

Hmm.

I dont get numbers that make sense when I use this website to calculate max hp from those injectors.

http://www.injector.com/injectorsele...58353a5c78d045

It says the maximum horsepower would be 178?

What am I doing wrong?

Unfortuneatly I am out of town for work (as usual) so i cant check the actual number on one of my injectors.

Kirk
(Great website by the way! I added it to my bookmarks)

JasonAndreas

What is the BSFC for a 964? If it is 0.4 then it works out, I think?

KirkF

I think .5 is the typical number used. And we should expect that the injectors are capable of 300+ hp
I see there are serveral columns marked porsche 3.6 in his data.

I guess we will need to have someone tell us the actual bosch number of the injector. I have several spares at home but I am out of town for two weeks for work. (It pays for the porsche parts. )

Anybody have an injector in front of them or know the model #?

Kirk

JasonAndreas

Everything I've just read says its mostly based on engine compression and a 3.6L is a high compression engine so .4 should be possible?


The part number I posted is the actual Bosch part number. I used it to order replacement filter baskets and pintle caps when I "rebuilt" mine. I didn't just pull it off that site, it was taken off an actual injector. I don't trust websites to have the correct part number either.


If you ever need to find a Bosch part number for any car look HERE.

KirkF

Jason,

Yep I went through the catalog, and they definetly list it as injector # 0 280 150 731
But to make this injector work for even the base 964 hp (250) i have to lower the bfsc number to 0.35

Do you know of any other websites that list this injectors flow characteristics? Maybe its the 18.45 lb/hr thats incorrect?

I have been searching, but I havent found one yet.


Kirk

Geoffrey

don't forget to do the calculations at 3.8bar rather than 3 bar.

KirkF

The injectors are rated at 18.45 lb/hr (193.9 cc/min) @ 43.5 psi (3 bar)

If you compensate for the higher fuel pressure 55psi (3.8 bar) the new flow is 20.746 lb/hr (214 cc/min)

However the injector flow sheets say that for 250hp / BSFC of 5 / 6 injectors and a duty cycle of .8 we would need 26 lb/hr (273 cc/min)

And on top of that we know the injectors dont max out at 250 hp. They are good for something over 300 Right? That would be over 31 lb/hr

So either the BFSC number I am using is wrong or the injector flow rate is wrong.

For naturally aspirated engines, estimate BSFC to be 0.4 to 0.5
For nitrous engines, estimate BSFC to be 0.5 to 0.6
For forced induction, estimate BSFC to be 0.6 to 0.7
For rotary engines, estimate BSFC to be 0.6 to 0.7

Of course all this leads back to the supercharger I want to install. When I figure out how much boost the kit is setup for, i need to figure out whether they used different injectors to make the HP.


Kirk

KirkF

I should probably post the links to the formulas I am using. (most of them from Jason)

Injector Data
http://users.erols.com/srweiss/tableifc.htm

Injector Worksheets
http://www.injector.com/injectorsele...58353a5c78d045

Injector Pressure / Flow worksheet
http://users.erols.com/srweiss/calcpchg.htm

Lots of Handy Car formulas
http://users.erols.com/srweiss/index.html

SimonExtreme

Once you adjust for fuel pressure, the injectors work out at 248 bhp with a BSFC of 0.4. Taking it further, at 100% duty cycle you can get 311bhp, which is 3 bhp more than the most I have seen on standard injectors. So, I now have further evidence that to tune my car further, I need bigger injectors. Then I need an engine management system that can easily be set up to manage those injectors.

SimonExtreme

Kirk

I think the BSFC for our cars should be 0.4 or maybe, at worst, 0.42. The figures then stack up.

What I find interesting is that for the 964RS (ROW) they get 260bhp which would suggest that at times, in standard form, the injectors are at more than 80% of max injector duty cycle.

Geoffrey

I can tell you from experience that the stock injectors are done somewhere in the 305-315hp range and after that, they cannot maintain a 13.2:1 AFR.

I have several recent flow sheets from getting some injectors cleaned. I'll see if I can them up. I think they are 24lb/hr, not 18lb/hr at standard fuel pressure. I think the 993s are 26lb/hr, but I could be mistaken on both accounts.

KirkF

The numbers on these injectors drop way down when I run the calculater for a forced induction engine. (BSFC .6) It drops the max hp down to about 160hp at 80% duty cycle.

Kirk

Christer

Simon, if you happen to use a management system without knock sensors - make sure you get some warning light that can advise you of detonation...