My Experience - 9XX KH Racing Chip

[zcacogp]

If there is popcorn around then pass it this way, chaps ... []

Yes, Andrew from Promax sent me a chip - probably about a month or so ago now. I fitted it a couple of weeks ago, and have probably done less than 20 miles in the car since then. (Possibly even less than 10!)

The car may be getting a more significant run this weekend, and I'll post some detailed impressions once this has happened. What I can say at this juncture is that it is more of a fiddle to fit than I was expecting; you need to dismantle the ECU to remove the old chip and install the new one, which involves removing the ECU cover to reveal two circuit boards, and then removing the top board. Getting that top board out was quite a fiddle, and given that the whole thing is a bit delicate I didn't much enjoy tugging at it. However it came out eventually, swapping the chips themselves was a doddle and putting it all back together was much easier than getting it apart.

More in due course.


Oli.

 

[AndrewS]

The 944S2 and 964 ECU units are more difficult to separate the boards than the other models.

So what about the 9XX KH chip, did that ever materialise?

 

[DivineE]

I once spoke to someone well informed about later Bosche ECU's from 1.8 and 2.0 turbo engines (he doesn't know anything about 944's so this may be totally irrelivent but) he told me those chips had various layers on them and a normal chip reader only gave access to 6 or so maps on the chip so tuners were able to alter the basic properties like ignition/fuel but could not access of undo the 140+ tables of bass data and safety trips.

Is it possible that an earlier form of the same system may exist on the 944's ecu hense why the 944 always 'coughs' as it comes on boost when tuned? It's not the end of the world but I noticed all the cars on the dyno day doing it and no one seems able to 'map it out'?

 

[barks944]

Its probably a limitation of the injection system itself. Remember the DME can't see boost, so the spool up period under full throttle is a bit of a grey area where the DME doesn't know whats happening. It is also different in different gears. In 5th I can get full boost by about 2.6-2.8k where as its more like 3k in 2nd 3rd. You need to take a conservative approace here so under some conditions its going to run very rich which is probably what the cough is you are talking about.

Edit: In fact, I believe I have noticed this on occasion and I put it down to oil getting into the intake via the turbo. Perhaps what I just described is the more likely culprit. Thanks for asking the question!

 

[AndrewS]

The following thread (on the 968 forum) throws up some interesting observations: http://www.porscheclubgbforum.com/tm.asp?m=530738

Regards,
Andrew

 

[pegasus]

With all this electronic chippery going on can any of the ecu experts answer the question I posed a long time back, why does the 944 engine have to turn a few times before stating.forget the problems of lazy starters tired batteries and ignition faults sutch as cap and leads etc, I can leave my s2 for a month and it still takes the same time (number of turns of the engine) after a month as after a day although still first turn of the key if you see what I mean,some have mused that this delay is built in to the processing system,is this true and what part of the system holds this information,a definitive answer would clear up a lot of posts about slow starting.I am talking of a purely computer based delay not about big engines,cold,bad ignition systems and how this delay increases the longevity of the engine etc, all the best John.

 

[bertelli_1]

I agree, 944's do tend to have a delay. However, I would suggest it has more to do with the fuel pressure. Most cars of this era will prime the fuel pump for 2 seconds when the ignition is turned on, the 944 only operates the pump when cranking and running.

 

[rcsalmons]

I may be wrong but I thought they had to hit a certain RPM before firing?

Rich

 

[pauljmcnulty]

With all this electronic chippery going on can any of the ecu experts answer the question I posed a long time back, why does the 944 engine have to turn a few times before stating.

Has to hit a certain RPM before fuel pump kicks in, as I understand. And, by understand I mean I have absolutely no idea why, but it's as good as an explanation as I've heard. []

Personally, I'm happy to go with the fact that it's a whacking great 3-litre 4-pot designed 30 years ago, and it just doesn't spin as quickly from cold as a modern engine. Doesn't wear out as quickly, either.

 

[pegasus]

This is what I would like answered by the electronic management buffs, the fuel pressure is not the delay as if the pump is hard wired and running befor the key is turned the engine still turns the same number of revs before starting. This is the only car engine I have come across that has this delay and would like to know exactly what causes it. Lets assume we are talking about an engine system with no faults just this delay, is it deliberate and how is it achieved, does the processor have to match a pickup signal against a clock signal with a time out function or what,I don't know but I am sure somone does and can explain it to us all.

 

[944 man]

ORIGINAL: zcacogp

...given that the whole thing is a bit delicate I didn't much enjoy tugging at it...


Oli.

I know that this is puerile; but this made me smile. []

 

[AndrewS]

ORIGINAL: pegasus

This is what I would like answered by the electronic management buffs, the fuel pressure is not the delay as if the pump is hard wired and running befor the key is turned the engine still turns the same number of revs before starting. This is the only car engine I have come across that has this delay and would like to know exactly what causes it. Lets assume we are talking about an engine system with no faults just this delay, is it deliberate and how is it achieved, does the processor have to match a pickup signal against a clock signal with a time out function or what,I don't know but I am sure somone does and can explain it to us all.

On the later cars, a dedicated timing wheel has been added to the flywheel. It requires only a single sensor that detects both reference-mark (TDC) and engine speed. The DME must sense the engine turning and passing TDC before it instructs the DME relay, which in turn switches on the fuel pump.

I have seen and owned many 944 models, some will start quicker than others. However, they do all seem to turn over slowly (compared to other cars - including the CV8 Monaro I'm using). That's just down to the gearing and speed of the starter motor.

This thread has deviated a little from the original post. Has anybody else purchased a KH 9XX chip? If so, you may want to contact barks944 (OP on this thread).

Regards,
Andrew

 

[wolfie308]

Sorry Oli, but re reading, I had to chuckle as well.....Tee hee arf arf

 

[zcacogp]

Well it wasn't meant to be funny. Sorry ...

(But, yes, I can see how it may be giggled at! [] )


Oli.

 

[DivineE]

Come on. Someone do a back to back comparison on a dyno and report back please. Same day, same car. Scientific. Not just for peak figures but looking at the whole rev range. Someone has to settle this before we lose sight of facts.

 

[Neil Haughey]

Its funny because my 968 starts pretty much on the button as quickly as any modern car, except in winter when if really cold it does churn over a little.

 

[AndrewS]

ORIGINAL: DivineE

Come on. Someone do a back to back comparison on a dyno and report back please. Same day, same car. Scientific. Not just for peak figures but looking at the whole rev range. Someone has to settle this before we lose sight of facts.

I would welcome that if we were comparing Apples with Oranges or even Granny Smiths with Cox's - but as someone will hopefully soon explain - the results of such a test are unlikely to yield any differences.

;-)

Regards,
Andrew

 

[pegasus]

Yet again we will never know if the 944 starting delay is built in of just a myth,it would have been nice to have it nailed and explained rather than the thats how I think it works answer, mabe somone will nail it someday,all the best John.

 

[AndrewS]

ORIGINAL: pegasus

Yet again we will never know if the 944 starting delay is built in of just a myth,it would have been nice to have it nailed and explained rather than the thats how I think it works answer, mabe somone will nail it someday,all the best John.

I'll stick my neck out here and say it's a myth. I have had numerous 924S, 944 and 944 Turbo variants - I've never been conscious of a delay when starting the engine, they just turn over slowly (compared to many other cars). The engine will start as soon as the engine turns fast enough to compress and ignite the injested air and fuel.

As stated, the flywheel sensor sends the signal to activate the fuel pump; there is not an engineered delay.

There are some interesting myths surrounding the DME ECU though - namely the mythical origin of a certain 'brand' of performance chip.
;-)
Regards,
Andrew

 

[pegasus]

Thanks for that Andrew but as I have said before if you hard wire the fuel pump so is is running before you start the engine the delay is the exact same. I can't go for the fast enough to build up compression thing either as the compression is there from the fist turn of the engine, the same as kick starting a large british single or pulling the prop on a gipsy four, if anything the bor clearances of the porsche are minute in comparison thus ensuring a very good squeeze from the word go,I just don't understand it,all the best John.