Kierf - ¿§?

What is the conversion from lb/hr to cc? I'm used to dealing with BLANK cc rated injectors. Also, does anyone know what the stock 951 injectors are rated at? Preferable cc, but any answer is fine...

Russ Murphy

Multiply by 10.5

Paul Bloomberg

I am not sure what my duty cycle is? Should I buy a new one?? Maybe 100lb injectors would help?
....the detonation.. by running really rich... then I can shoot flames out my exhaust w/lots of advance....Would 100lbs injectors increase my 404whp to maybe 425???
Paul <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> biggulp: <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" /> <img src="graemlins/sleep.gif" border="0" alt="[sleep]" />
ITGZ211 no not the car I'm a TAP FAN

Danno

"Are you going to use the standard Motronic or an aftermarket engine management system? (i.e. batch or sequential injection?)"

There's no difference between batch vs. sequential injection if you're using the same sized injectors. It's just a matter of when you time the 'off' period. At 100% duty-cycle, they are both exactly the same. I drew up some pictures here: RacerX's Sequential vs. Batch Injection dissertation.

"Also, does anyone know what the stock 951 injectors are rated at?"

I think I finally figured out the stock injector sizes (thanks TT). Take a look at these two different injector reports:

R.C. Engineering - Tony Garcia
R.C. Engineering - Tom Swank

At first glance it would appear to be a discrepancy since the average of Tom's injectors are 366cc/min while Tony's averaged 262.8cc/min.

However, Tony's injectors were tested at 951 operating parameters of 2.5-bar fuel-pressure and 80% duty-cycle. The more commonly-accepted rating is at full 100% static-flow and 3.0bar fuel-pressure like Tom's. Here's how we can scale Tony's injectors to the standardized format.

Average of Tony's injectors 262.8cc/min. Then we compute flow at 100% duty-cycle:

262.8cc/min / 0.80 = 328.5cc/min

Then adjust fuel-pressure to 3.0-bar:

SQRT(43.5psi / 36.25psi) = 1.095 difference in flow
328.5cc/min * 1.095 = 359.9cc/min

So under the same test conditions, Tony's injectors would flow 359.9cc/min, which closely matches Tom's test of 366.0cc/min.

Take the average of those two results

(359.9cc/min + 366.0cc/min) / 2 = 362.9cc/min

and converting to lb/hr, we get:

(362.9cc/min) / 10.5lb/hr(cc/min) = 34.6 lb/hr

So I can finally come to a definitely conclusion that the stock 951 injectors flow 34.6lb/hr @ 3.0bar.

Ok, let's work backwards from stock HP ratings to compute BSFC. Stock Turbo is 217bhp and TurboS is 247bhp. Plugging into the equations on R.C. Engineering's website, we get:

Turbo BSFC = (34.6lb/hr * 4 injectors * 0.80 duty-cycle) / 217hp = 0.51
TurboS BSFC = (34.6lb/hr * 4 injectors * 0.80 duty-cycle) / 247hp = 0.45

Notice that the more efficient TurboS uses less fuel.

Alright, let's work forwards again and see what is the recommended injector sizing for 460bhp @ 0.48BSFC average.

(460 bhp * 0.48 BSFC) / (4 injectors * 0.80) = 68.9 lb/hr

But this is assuming you keep your car's efficiency stock. If you do high-flow mods, more efficient turbos, etc... you can get away with less. For example, the stock injectors typically get maxed out at around 280-300rwhp. But with free-flow mods such as MAF kits, exhaust, etc. like on Paul's car, you can see higher HP before the injectors are maxed out.

EDIT: Fixed URL/Links formatting...

Paul Bloomberg

Danno,
You are a wealth of info!

Regarding my MAF set-up, which I always seem to be defending, which is probabley due to me having a bad case of engine management envy : ) : )It really is a turn key set-up as long as I run the octane.
Paul

951and944S

Danno, great work, that information is very valued and needed to be posted, it surely took some time to gather those results, let alone construct that post and the logical averaging of Tom and Tony's reliable figures make your findings all the more credible.......

I'm pretty certain that the 16V "S" cars have a higher capacity fuel pump, and the injectors for S/S2's carry a different part # as well, the FPR from the S/S2/968 is commonly used as an upgrade for the 951, so, any idea if the stock S/S2 injectors are worth the trouble as an upgrade to the stock 951 injectors..?
Do you know where the information for flow capacities may be posted for the S/S2/968 injectors so I may make my own comparisons..?

<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

tecart

I will be posting my dyno results this month with hp and torque readings with my stock injectors and my maf#4 kit with a kkk29#8 turbo and such as well as with the bigger injectors i have on now, i will try to post both tests here asap and then we will see if you can run close to 350 rwhp with stock injectors or not, i think im there for sure and i know that with the bigger injectors im close to 400 but the dyno will tell, the only thing is the one shop says he cant tell me the air/fuel ratios, but another shop could but he was so snobby when i asked for 2-3 hours on his dyno so ill probally get the hp and tq readings asap and do fuel another day, look for my posts later on

ken louie

This topic is very interesting. My question to the board is how big of injectors do you need to run 400 rwhp on pump gas? I would think that it would take at least 20 pounds of boost and 72 pounds injectors. Anyone care to comment.

ken
86 951
79 930

Danno

So far all of the 2.5l ones I've seen that have achieved 400rwhp has used around 25psi.

rage2

[quote]Originally posted by Danno:
<strong>So far all of the 2.5l ones I've seen that have achieved 400rwhp has used 25psi.</strong><hr></blockquote>

I broke 400rwhp last night (FINALLY!) at 22psi. 407rwhp.

Paul Bloomberg

Rage,
Cool!!! You won't want to turn it down now : )
Did you say that was with 91 octane? If so that is fantastic. A lot easier on the wallet too!

List,
What is the trq/hp number's at 5252 RPM of some of the various cars with bigger turbos, stand alone, ect...
Paul

toddk911

There are people here running 20-25psi on PUMP GAS??? What ign. retard are you running?

With that amount of boost and mods, I would think it is worth it to spring for the 4$ gallon 104 octane or 7$ gallon of Xylene 117 octane and save the time and hassle of running a ton of ign retard.

toddk911

So stepping up to 55# injectors is about 36% increase over stock flows <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

Paul Bloomberg

I always run at least 110 octane when running 25lbs of boost or so.
From what I understand as I am a "end user" not a tuner! The turbo(mine is a Technodyne 4" inlet dual ballbearing) is key to allow you to run high boost w/o detrement. Along with getting a/f, ect...
Paul

rage2

I ran 25psi on 91 octane very briefly. Very heavy ignition retard, no detonation, but EGT's was way high, so it's not the smartest thing to do. 15psi seems to be the safe limit on 91 octane for my engine at 16 degrees of timing.