tonytaylor

Yeah, pathetic 48bhp increase.

flatair

I tend not to trust BA these days, especially after looking at his market price evaluations.

Steve Weiner-Rennsport Systems

LOL,....A wise man, that Mr. Anderson,.....

FI injector capacity is NOT a limiting factor in 993's and 964's unless camshafts larger than RS cams, along with a whole host of other mods that require engine operation well above 7000 RPM.

Stock-type cams and OBD compliance define the engine parameters & requirements in each instance. The OEM Motronic system and its componentry is not an obstacle or hindrance to power when using smog-legal cams that limit effective RPM to 7000 or less.

Now then, if you install a tall, six-butterfly intake system (http://www.rennsportsystems.com/1-c.html), then the only way to take advantage of such a thing if you use programmable EFI such as MoTeC or EFI. In these cases, larger injectors are used depending on cams, exhaust, and CR.

I'd simply add that dyno results can be manipulated by experienced personnel.

flatair

Well there ya have it folks!

So Steve, injectors aren't nearing the 90%+ duty cycle on 993's with the 'typical' street mods?

Steve Weiner-Rennsport Systems

Flat air:

OMG,...........heck no.

LOL,....that would make it a "CIS" FI system.

Further, the injectors drivers in the ECU would not last long drawing all that current holding the injectors open 90% of the time.

tonytaylor

I haven't seen many examples of Motronic equiped cars with the normal mods running over 300bhp yet the MOTEC and larger injector package appears to produce significantly more than this with standard cams valves etc. The Motec package won't produce the same results without the larger injectors.
As I see it you can't get over 300bhp without cams and intake mods that require MOTEc et al anyway.

Which is easily spotted by experience personnel

FWIW the gains posted were not measured by installer of the MAF but 9M as I was considering MOTEC at the time. If anything it would have been in his interest to understate the actual bhp as I would have been more likely to have spent money on the MOTEC.
To be fair that was 3 years ago and since the dreaded 964 cylinder head leak has surfaced, no doubt due to the track miles, but I would still be happy for anyone with a stock 993 to find out how much power the car is running

flatair

OMG,...........heck no.

LOL,....that would make it a "CIS" FI system.

Further, the injectors drivers in the ECU would not last long drawing all that current holding the injectors open 90% of the time.

Hah! CIS, those were the good ole days! Actually I'd love to see the old MFI modified to fit on a 993 3.6 Interesting bit of information as well on the injector drivers - Steve you really are a guru! Thanks for the input.

NineMeister

With respect to the 964RS on Motec, on the very first Motec conversion we started the mapping on standard injectors, and the best performance we could achieve was 296bhp flywheel on the day with the injectors running nigh on 100% of a 20ms pulse width, i.e. running continuously at 6000rpm. Interestingly Tony's 964 with its mass flow conversion posted 297 on the same dyno with std injectors and fuel pressure. Eventually, with larger injectors, this same motec equipped engine with no other changes posted 324bhp (at well less than 7000rpm) as well as 398Nm of torque. My conclusion is that the 964 needs larger injectors running in full sequential mode in order to make over 300bhp.

Although I have not proven it for myself, I am told by reputable sources that the 964 motronic ecu switches to batch fire above a certain duty cycle, hence why the drivers do not burn out in "continuous" mode.

The 993 engine does not respond as well to the Motec treatment since there are other limiting factors coming into play like the cylinder head design. Sticking my neck on the line I would go as far to say that although the flowbench racers love the 993 & 993RS big valves and high flow numbers, in practise they are an inferior design in comparison to the 964 and actually restrict the engine performance. For this and other reasons we generally prefer to remap the motronic ecu on the 993 variants as the potential gains are not as great as the 964 models.

Anyway, to answer the question, yes you can remap any motronic ecu (964/993/993TT etc.) to run with larger injectors PROVIDED that the injectors chosen are of the same impedence as the standard injector. Unfortunately most tuners prefer low impedence injectors for their faster reaction speeds and these are not compatible with most motronic ecus as they run high impedence injectors, so you have to be very careful over what you choose. A good example of this principle is the 9m/SFR 968 supercharger conversion where we remapped the stock ecu for larger injectors to run 350+bhp; in this case we also deleted the mass flow meter (since the signal became unstable at the air flow rates we are developing) and used the default throttle position only map within the ecu to drive the injector in alpha-N mode (throttle angle vs speed), having to expand the map to cope with the full range of the load.

I would also like to add that to date we have never manipulated any dyno results............

flatair

Thanks for your great contribution Colin. I apologise for not alerting you to this thread sooner, as I referenced your work and data. I was under the impression (I am no expert) that the 993 and 964 heads were fairly close in design. So you're saying the primary problem with the 993 his head flow- Could one use 964 type heads on a 993?

Steve Weiner-Rennsport Systems

Gents:

With all due respect to Colin, I'd go on record here and mention that the 993 heads (especially the 3.8 RS ones) outflow every 964 head (RS included) that I've tested on our flow bench over the past 16 years. This covered all street and Factory race heads that we've seen.

Only 964 RSR heads flow better than the other 964 ones,...

This is only a reflection of our experience with these things and others may vary.

flatair

Steve, that include the smaller valve pre-vram 95 heads?

Christer

I guess that is the difference between a 'flow bench' and a practical solution - i.e. like in a car?

NineMeister

Steve,
I agree with you, I have a bench and have tested almost every aircooled head that Porsche make and can also confirm that 993 head outflows the 964 head at every lift point from 0.1 to 14mm of lift, what's more is that the 993RS head also blows the ports off a 993 head (on the flowbench).

Thanks, you have confirmed my point exactly.

meng haifeng

hi guys im a newbie, quite exited reading what you lot get up to, i choose this section because my car is a mixture.
firstly car started out as 964 C4, then added a 95 993 engine and kept the old 964 dual mass flywheel, and my old inlet manifold, a few months ago, we added varioram, and motec m600 all going great, a couple of months ago added 993 rear subframe and huge alteration for rear axles and 964 C4 gearbox, two weeks ago dropped engine and installed 993 C2 G50 gearbox, came with the gearbox a C2 dual mass in better condition than mine, so installed that set the fly wheel sensor 0,7 mil removed all C4 drive train put engine back, cranks over smoothly, fuel pressure in the lines, and only sparks from the top of the distributor caps NOT at the plug end...

Question is there a difference between 964 C4 and 993 C2 flywheels, they look the same, however without dropping the engine again, is the locating pin on the back of these flywheels in a different place, hence why maybe the timing is out,

looking into the engine bay, i cracked the fuel line on the right fuel rail, fuel sprayed every were, done the same on left fuel rail, just a trickle came out, is this due to the fuel regulator on the left,

my mechanic says now we need new ignitors, could this be reason for only a spark from top of cap and not down the lead itself,

i unplugged the alternator when i dropped the engine, also an excuse to have the flywheel fan chromed, has this caused problems with DME on board parameters,

have replaced battery, new flywheel sensor new plugs, 5 DME relay, fuel pump runs both distributor maybe two year old, the guy who fitted the motec, wired into the ignition side, so does this mean no DME, as i dont understand enough, i was told it no only operates the fuel pump

guys i really hope you can help, car insurance due, tax due, workshop want me out, as i said just a few days work, been there almost 3 weeks, wife is hanging in there still bless her

guys i love porsches she's my fourth, over the years i had two 944, never played up once, a 928 S4 and now this, and i cant give up on her


David

Martin S.

Chris Cervilli and Viper Bob on the same string, outstanding. These guys know from which they speak. Keep posting Chris and Bob...we need your BS detectors protecting gullible folks like me.