August West

A bit of a thread hijack from another posting but I wanted to give these injectors their own thread. These injectors from fiveomotorsports ( http://www.fiveomotorsport.com/bosch-porsche-911) flow at 246 cc/min as opposed to the stock injectors at 193 cc/min.

I'm wondering if the stock barn door MAF intake is too restrictive to take advantage of these injectors. I already have Elgin Super C2 cams, Euro RS valves, K&N filter and cup airbox, Fabspeed Sport Cat and G-pipe. I'm in the middle of getting a custom chip from Steve Wong so was thinking why not try these injectors, burn a new chip and see what gains I can get.

Would I be looking at having to upgrade fuel pump as well?

Any discussion on this topic would be helpful!

ras62

I have installed these injectors on my previously chipped but stock internal engine. The car is running a little rich but seems to run through the revs smoother and faster. I cant give figures as I have not had the car on a dyno... yet. In your position with a cam etc I would say these injectors will make a difference (they cannot be any worse?!) Ideally I would get the car mapped on a rolling road rather than a generic chip.
Is the barn door sensor restictive? Honestly I dont know, but my thinking is it is not in a relatively mildly tune motor. Flow is not restricted until mach numbers are reached, the valve size, head flows and compression ratio are far more critical, but in truth it is a very complicated subject that can cause argument even between experts.

August West

hhhhmmm... I thought these new injectors would have elicited more discussion.

No comments from the horsepower junkies out there?

I'm still waiting to hear back from my mechanic as to what his thoughts are on swapping out the injectors and remapping on a rolling road dyno. Will keep posted!

ALEX P

It is an interesting subject. I have read that the stock injectors are reaching their peak past 300bhp but can't really find where this is written.

Knowing that the stock injectors are in good shape I would really like to see a direct rolling road comparison to see the difference between the two.

I would also certainly want to see some AFR figures if swapping the injectors to make sure that you're not running rich or lean.

So maybe the questions is - they can't do any harm if the car is mapped correctly to suit but are they necessary?

I'm just thinking out loud really - Hopefully someone clever can give an opinion.

Sire

Jeff and ninemeister have been written this info.

jpar

I'm reviving this thread because I'm interested in these. Has anyone used these? Anyone have a link to the discussions mentioned above?

Juha G

If your stock injectors are shot, sure. But if they work as they should, replacing them is a waste time and money. IMHO.

NineMeister

There are no easy solutions to multi-variable equations. Tuning a 964, or any engine for that matter, is much more than a just a multi-variable problem space that you can solve with linear, single focus ideas, hence there is no right or wrong answer to the OP's original question. That's why those of us with the experience to offer information are not rushing to reply on the basis that there is no definitive right or wrong answers that can be offered in the space of a reply. That said, I'm more than happy to confirm two pieces of information which may help.

I believe that I was the first person to publicise the performance limit of the stock beige fuel injectors based on my findings when tuning the very first 9m Motec conversion on a stock 964RS (see graph). I first tuned that car with the M48 ecu on beige injectors and was puzzled by the flow demand of the engine and resulting max'ed out injector pulse widths in the tables with the engine peaking somewhere around 305hp. When I replaced the injectors with a set of Bosch 803's from a 944 turbo we achieved the results shown. So yes, the stock injectors will not support much more than 300hp at standard fuel pressure.

The air flow meter is a restriction, but not as much of a restriction as the standard paper air filter and lid. The second graph shows the results of running a stock air flow meter, air box & filter assembly to same with no filter/lid and same again with a manufactured air flow meter replacement tube.

The true solution to AW's question of what to do with his modified 964 engine is to bin the Motronic completely and fit Motec with larger injectors; the resulting difference in engine power from now to Motec will be far greater than the standard engine to now.

In my opinion......

jpar

Thanks for the quick response Colin. I'm not quite ready for Motec just yet. I only brought this up because I have my engine out for a clutch and re-seal and was thinking of sending my 130k mile injectors out to get cleaned and also replace the o-rings. I can get these red injectors for not much more, and wonder if I'd benefit from them.

Vandit

Getting the stock injectors rebuilt is like $20/injector. You can get new, uprated, injectors for not much more than $20/injector?

jpar

These only retail for around $40 and I can do better than that. My point is, if I can get new ones and see even minor gains, they're well worth the extra $60-$80 over cleaning.

SuperUser

Wow, $40 is not bad, I was about to send my injectors out to WhichHunter to be checked and cleaned. I wounder if I should just make the jump up also. I already have a Wong chip and I was about to send it back to have it tweaked after I get the car Dynoed.

Juha G

+964.

I fully agree with Colin. On the other hand, I see no point in changing the injectors unless they've gone bad or if you are modifying the engine to get more power and the stock injectors are maxed out.

This is not on a 964 but on a 993 varioram engine. Nothing else was changed, same dyno, same conditions etc.

Before Motec:



After Motec:


You can make an adapter harness for the Motec so no need to cut any of the original wiring harness. I just bought a used BMW ECU for €50 with same 88-pin connector as the 993 ECU, gutted it and soldered the harness into it. It is true plug and play. I could switch back to the standard ECU in a matter of minutes.
It is even easier for the 964s as you can buy the 55-pin male connector (not the case with the 88-pin, hence the used BMW ECU).
The Bosch ECU you see in the photo below, is just an empty core. The plug on it goes directly to the wiring harness on the car.



Colin has made these harnesses before and I am sure he will be happy to provide a package (Motec+harness+mapping). In my opinion doing any other "performance" modifications on the engine is not worth it, unless you have means to fine tune the fuel and ignition (i.e. Motec or similar).

alexjc4

That's great info Juha, I've been thinking about making a harness for a Link ecu for my car without cutting up the standard harness.

With a 6 cylinder engine the maths to figure out the injector limit is pretty easy. But theres no need the do all the calculations, the rule that comes out the end is really convenient:

Flow measured in cc/min at line pressure = max bhp

So if the stock injectors are rated 193cc/min at 3bar (the pressure most injector flow rates are given) and we know the rail in the 964 is 5bar so we scale and get 320cc/min so 320bhp.

Allow for the fact that the injectors flow wont increase with pressure in a totally linear way and you don't want to run 100% duty cycle on the injectors and a 300bhp limit seems sensible.

You would be very unlikely to get more than 320bhp from the stock injectors without raising the rail pressure.

Juha G

All you really need is the pin out for the stock ECU, the 55-pin plug, electrical wire and soldering equipment:



On the other hand, I think Colin asks about 500 for the harness. I think it's a 500 worth spending for a professionally made harness, unless you are electrically inclined (so you can test and troubleshoot the homemade harness as well)