Thread: P38 4.6 What would you do?

I've now got HC pistons in my ported GEMS 4.6 and a Stage 2 cam.

No change in the ECU but I do plan to fit a Haltech Interceptor (KRudd's paying for it).

With 9.55:1 you will need ULP at least and probably 98 octane, which will limit where you can buy fuel.

GEMS is very sophisticated and should compensate , as long as you do not do silly things like try and run 91 . The ECU should advance until knock then the sensors pull it back.

Whether the Low comp advance algorithm is the same as the HC, I doubt anyone in OZ will know as they were never sold HC in OZ.

There is a guy named Marc Adams in UK who is the guru on this and makes the Tornado chip fro the 14CUX.
I suggest you contact him and ask whether the ECU needs a chip or reflash and go from there, or contact RPI who are one of his retailers.
Regard sPhilip A

Apologies for my previous post, I was a little tense.

Thank-you to Phillip and Ron,

They are the helpful kind of responses. I have made a mistake in that I am more often than not, i am too trusting. I should of gotten them to write down, what they were going to do, but as my motor was in pieces and unknown condition, it was a bit hard.

So for my next question, excuse my ignorance, but with knock sensors and EGO sensors shouldn't the ecu be able to compensate for whatever fuel I run?

I spoke to someone on another forum who had contacted mark adams about this issue, who seemed to think it was ok, as long as I reset the adaptives.

Stu

So for my next question, excuse my ignorance, but with knock sensors and EGO sensors shouldn't the ecu be able to compensate for whatever fuel I run?

Sure it will go well, and on the fuel side should give a pretty well perfect outcome.
However I would think that any changes to the program would be on the timing side.
If the tuning of the low comp is "Rest of World" like a 14CUX, and I think it is, then the timing may be quite conservative to account for low octane fuels available in Khazakhstan or one of the other Stans. Even with knock sensors etc if too much timing is programmed then there will be problems. So it may be that the timing is retarded vs what is possible.

So the high comp timing may have more advance. The engine will still run fine but if you want max power and economy, a chip may be able to be set on the dyno to give a close to optimum result.

However it may not be worth doing as Ward at Graeme Cooper has told me the gains on a low comp are quite small.
Over to you.
Regards Philip A

I haven't noticed any knocking on ULP but then I mainly run on LPG.

I often top up with PULP as I don't use a lot of petrol so the cost spread over 3-monthly petrol top-ups in not a worry.

Does yours have the oxygen sensors?

My only concern is, what will happen if I am in a remote area and can only get regular unleaded? Can you get octane boost or something that can be added to the tank?

Stu

"With 9.55:1 you will need ULP at least and probably 98 octane, which will limit where you can buy fuel.....as long as you do not do silly things like try and run 91 "

Not sure what's meant here: regular ULP is 91 Octane....

The Commodore LS1 runs 10.1:1 compression. GMH clearly state that 91 Octane is quite adequate and that higher octane fuel is not necessary...I run the Commode on 91 ULP ...

With knock sensors and oxygen sensors the GEMS system should be quite capable of managing ULP (91 oct) with a 9.55:1 compression. 95 Octane would probably be better in that the knock sensors wouldn't have to work as hard...

A compression ratio of 8.35:1 simply means that the engine will be less stressed...should run "forever" if well looked after. How often do you need the few extra kW ...

Originally Posted by 81stubee

Does yours have the oxygen sensors?

No, there are no O2 sensors on an Australian '95 model. I don't think Aust got them until the '99 Thor models.