L8Apex

As some of you might know California has some crappy gas. 91 octane is the highest at the pump unless you hit the 76 station that carries 100 octane. I have been advised to run a .8 bar spring instead of the 1.0 bar.

So, my question is can I run this higher boost (1.0 bar) on 91 octane without damaging the engine?

Adrian

The 964 Turbo 3.6 is actually designed to run on this fuel. It performs best on higher octane like we use here of 98 RON which I think for you guys is 95. I would not worry about the boost spring rating to be quite honest because the over boost protection for the engine will still activate. The lower octane fuel is not exactly going to co-operate to allow you reach max boost anyway. Did you install this 1.0 bar spring yourself into the wastegate or were you told it was already fitted?
Ciao,
Adrian
964C4

Staffan

Just make sure your engine doesn't run to lean.
Take the car to a dyno and check your Air/Fuel ratio. You could be running lean without knowing it, which isn't a good thing especially when running higher than stock boost.

The usual advice when running higher than stock boost is to run without the catalytic converter, disconnect the O2 sensor and set CO to 3% at idle.

Instead of a 1 bar spring, you could use the stock wastegate spring and install an Electronic Boost Controller instead.

fc-racer

Adrian,

I don't think the 964 Turbo 3.3 or 3.6 would run any differently on higher octane fuel because it has no automatic capability to adjust its mixture or timing based on fuel quality (knock). Unlike the Motronic Turbo cars (944 Turbo, 993 Turbo, 996 Turbo), the 964 Turbo does not have a knock sensor and the only feedback mechanism it has would be the O2 Sensor which is disabled on full throttle where you would need the higher octane fuel.

The only way to make the car run better with better fuel is to manually adjust the mixture, boost and timing to compensate for running higher octane fuel.

The key with this car is to keep it from running lean and to prevent detonation. The only way to really know if you are running lean is to get a wideband O2 sensor and put the car on a dyno, map out the mixture and see where you are at and adjust accordingly.

My 3.3 runs 1.05bar boost in the midrange, dropping to 0.98bar or thereabouts at the top end and the mixture stays at 11.9:1-12:1 throughout the range with the CO% at 2.0% at idle and the Andial Fueller at the 2nd setting.

fc-racer

Adrian

Dear FC-Racer,
Whilst I do not disagree with your statement about the knock sensor system and running too lean I have to ask the question why do Porsche recommend 98 RON for the Turbos and 95 RON for the NAs? if as you say it does not make any difference? 91 Octane in the US is 94 Octane here which is 1 below the normal Euro Super fuel of 95 RON. 98 would burn better and be more efficient. This would also allow the programmed timing maps to be advanced further. Please do not forget that the ignition control unit is pre-programmed with ignition maps and receives a pressure input as well. I have to agree that my full understanding of how the CIS and these digital systems are fully intergrated when it comes to issues such as fuel octanes is somewhat lacking.
Ciao,
Adrian
964C4

Staffan

There is a pin on one of electronic boxes where you can tell the "system" what fuel you are using, if I remeber correctly it's factory set for "low" octane fuel to be on the safe side, but I am not sure.

Does anyone have more info and/or experience of changing this ?

Miles965uk

Hey Staffan, any luck finding out this pin you can change?

Sameer

I would stick to the stock 0.8 bar spring at 91 octane unless your running twinplug. If you go up higher octane, 1 bar is all yours to enjoy but in the mean time, play safe rather than being sorry.

Staffan

It's an empty contact left side of the engine bay.
If you short this contact the EZ69 unit retard the spark a bit to save the engine when running bad fuel. Not much use for us.

Kevin

I had the very nice experience to run through the midwest and rockies on my way back to the Northwest. I was able to run 93, 92, and 91.. With a stock engine at .07 I could definately tell when better fuel was ran. It was really apparent at the high elevations.. Yes, I realize that the air was thinner and that the turbo was working 30-35% harder.. Adrian, being that the engine lacks the precise control of timing and boost control, compared to the 993TT and 996TT, I would NOT install or recommend the installation of a 1bar spring AND run 91 Crap octane. You lose you reserve capacity or safety margin for detonation that will hammer your rings and bearings...

Sameer

I think Kevin just about says it all. We have to agree with him.

Miles965uk

cheers staffan,Kevin & Sameer, not any good to me i use 98 (UK) shell optimax all the time. i will put it on a set of rollers soon- which makes me think will they adjust the timing to accomodate this? i thought the engine did it automatiacally anyway...

Sameer

Miles,
cheers mate.

Whats rollers? I've set my ignition timing to 24-25 degrees(Ruf specs for my car).

leonardtay

Rollers means rolling road dyno.

911 2

im running 98 octane and run it all the time i was under the impression a 965 3.3

1. the mixture can only be adjusted for idle but once driving the ecu takes over therefore cant be adjusted

2. how do you adjust the timing i thought it was fixed and self adjusted via ecu

3. could someone explain what this pin adjustement is i run 98 octane all the time but never have adjusted any pin for the engine to accomodate the 98 octane