[flash]

horse puckey

 

it's not my criteria.  if it does not run as OEM, then it does not "run fine".  just because you can fire it up and take it to the grocery store, does not mean it "runs fine".  if it runs lean, which you have yet to ascertain, then it does not run fine.

 

it's also not paranoia.  if it is running lean, it could easily cause detonation, which could then result in damage.  even if it is just a little lean, then it could burn valves.  you won't be able to see this until it's too late, and right up until the failure point, it will "run fine".

 

further, a tiptronic car does not rev as fast, and also has a built in safeguard which retards timing on downshift.  this could easily mislead someone into thinking it "runs fine".  on a 6 speed, especially with a performance chip, this could easily cross the line.  suggesting that it "runs fine" without any data whatsoever, is irresponsible and negligent.

 
we have a responsibility to the membership, and we will not allow unproven and potentially dangerous modifications to be suggested to the membership.  this is yet unproven.  when you provide some A/F readings, then we will know if it "runs fine" or not.

 

this may indeed work.  but, go get some tests, and show us some data.

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[wildcat]

As I said initially, I was not suggesting this as a permanent fix, although I am seriously considering it as the performance seems to be enhanced. I was getting lag from first to second as you are aware and that is no longer the case. 

 

If someone suggested a fix for something, I would look into it... and weigh it on its merits. In this case I would have considered replacing the platinum wire, with platinum wire, that would have been the logical conclusion.  The fact that I did so with copper in no way suggested that that was what I was recommending. I suppose here these things have to be spelled out but seriously that is not the way of the world. One draws one's own conclusions and asks questions if need be.

 

I bought a door handle from a reputable mechanic that specializes in older Porsches. I asked him some particulars about the door lock in the handle.  He said something to the effect "once you get it off, the lock should just pop out".  In fact there's a rolled steel pin that keeps it in place. But he implied "you tap it out". If I had noticed the pin I could have damaged the lock.  In my experience this is not uncommon.  Caveat Emptor. 

 

My car not only runs fine, it runs GREAT.  If someone has the motivaton to try it, they'll be rewarded for their effort, or they can go out and buy a rebuilt one. I'm not selling a product here, I'm offering a possible solution. (Same with removing the center muffler which incidentally the 944 doesn't have.) But I can't be there to be sure they do it right and if that's what's expected no one will provide a "fix" for anything. 

 

As far as modifications go, I wasn't suggesting anything of the sort. I was stating that it worked, one draws one's own conclusions. 

 

There's a metal tap in the center switch in the tip gear shifter which goes bad.  I built a replacement.  Either that or pay $260 to buy a whole new switch assembly not to mention the labor of resoldering the leads and tracing the wires. I dare not suggest it, its not OEM, I do get it.

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[Waylander]

Just wondering about this must be OEM, just out of interest what page of the PET catalogue has the part number for the supercharger and inter cooler.


Or should I contact my local Porsche centre?

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[flash]

lol - i am not saying it can't work.  i am saying that before anybody says it does, and publishes it, that proper testing be done to prove it.  anecdotal stuff is NOT enough.  to address the above point, i did EXTENSIVE testing, and published the results, long before i started putting out the supercharger kit.  i ran it for over a year before i built the first kit for sale.  we insist on that kind of thing around here.

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[wildcat]

O.K. so "GREAT" is subjective... I have a 140,000 miles plus on the engine, but the compression is good, it doesn't smoke, the valves hum in rhythm etc. I've been doing a little tweaking here and there like injector rebuilds etc. It passed smog with flying colors as I've posted.

 

Now to the MAF which has been the problem of which I was not aware.  Throttle lag... specifically from idle. Its not much when you rev the engine but its there and I just concluded it was normal.

I did not make the association with "off the line" starts.  I was thinking that with the transmission engaged the computer was compensating for the transmission's drag and had therefore concluded that the transmission was the culprit as there was a delayed response to a fast acceleration. I'm not talking much just enough that by comparison with the response of the engine at higher rpms I wondered. Did they retard the transmission intentionally?

 

The solution as I posted previously was to put one foot on the brake and with the other increase the rpms for launch... hmmm...

 

Well the culprit appears to be the MAF. Little did I suspect that the MAF with age was not responding from idle as it might.  That apparently is a tell tale sign that it is going bad. Yes that is speculative and the only way I can corroborate that statement is to say that having replaced the wire I no longer have a noticeable lag either in the response to the thottle or more importantly the response to the transmission.  Starting in "D" and stepping on it it automatically drops to 1st and off it goes... Prior to this there was a delay and the delay appeared starting off in1st in manual and 2nd in Drive... I had tried several things including replacing the ATF to no avail and resigned myself to the notion that it was the transmission.

 

Happily it is not, I'm getting very good response from idle on up to preset redline...

 

I also plan to buy the plantinum wire.  Its been an interesting learning experience about MAF and its relationship with the system. 

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[ds968]

That's an interesting observation ( the MAF making a difference in off-the-line launch in terms of the transmission reaction time from idle when in " D " ) . It's tough to quantify this because I'm going by no more than the seat of the pants feel, but although I do feel feel a lag when I' in " D " and stomp on it , as opposed to being in "1" and doing that , it may be a matter of no more than 2 or 3 tenths of a sec. between the two scenarios . As for bringing up the rpm with your foot on the break and letting it go, lol, I haven't done that with the 968 ( and not willing to try..) but it was pretty common practice with some of the American cars I drove in the 70s just to create as much tire smoke as possible :-) :-) . The trannie and the differential in the 968s are too costly to take a chance on messing them up. I haven't even popped the clutch in my six speed 968 ( off the line that is ) , for that same reason. But back to the MAF , I find it amazing that it reacts so quickly going from standstill in idle to WOT , and sends a signal to the ECU in time to make an impact on the transmission's take off mode, in a fraction of second . This is not PDK, for heavens sake, LOL !

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[flash]

the ECU response time off idle is exactly .5 seconds.  it drops to .25 seconds at higher rpms.

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[williamoss]

_{What I do not understand about this whole discussion is It was stated that platinum wire is available, OK much more expensive. So why not use platinum wire. You could go to any jewelry store and buy some platinum solder from them. It might be silver solder. Then is would be the same as an OEM.}

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[wildcat]

At the time the wire in the MAF broke it wasn't available and I needed the car the next morning... so I improvised. It was a curious thing that I pulled off the air cleaner cover and inspected the MAF and noticed the wire was broken... it could have been a bad spark plug, the symptoms are similar.

 

Mine still does not react so quickly, at least not as quickly as your statement implies.... the butterfly valve has to open and there's a delay, but at idle when I give it gas (not in gear) there's a noticeable improvement in response time.  I attribute this to the MAF sensor responding to the air pressure differential more rapidly due to the sensor wire being more tensile.  An older wire especially a very thin older wire will not conduct as well, and its thermal conductivity here that is the issue. 

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[Waylander]

almost, (in Reply to Williammoss)

 

the wire would have to be exactly the same diameter and have the same electrical resistance, as I would guess the device is calibrated before its sealed up by Bosch.

 

but there are cheap alternatives that are electrically the same just a bit physically different.

 

the wire is cooled by air flow which allows it to calculate the mass of air flowing by, if the wire is larger it has more surface area so cools quicker but heats slower, at this point the maths completely out pace my limp brain

 

so I would suggest you can get quite close but to be dead on would be pure luck.

 

I doubt very much is the ECU can cope with massive changes of data from the MAF as its expecting a set of parameters that were designed in.

 

It would be an interesting exercise to compare an old MAF against a brand new one, to see if the throttle response improved in the same way as wildcat has experienced

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[Waylander]

bit more reading if this subject interest you

 





 

 

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[wildcat]

Very nice description of the principles and components.  The wire element is constantly being heated and sometimes super-heated to burn off contaminants.  With 140k plus miles one can barely imagine how many times its been heated.  The rush of air when the throttle goes from idle to full is the most radical transition the MAF has to deal with. Pump the accelerator in neutral from idle  to 5k and from 2k to 5k  and the difference is noticeable. That initial lag on this older car was more noticeable. Partly of course its the vario-cam but the copper wire has made a difference. I'm going to try a .01 in the platinum thermocouple alloy which is thicker than the stock wire and see how it works.  I might note the copper wire does not work as well in cooler temperatures. The MAF likes the ambient temperature warm with the copper wire and that's probably because its a poor thermal conductor. 

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[Inkedupfatboy]

I bet a chunk of an old extention cord would work too. I use that stuff for all sorts of wiring jobs around the house. Speaker wire rocks too.

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[Waylander]

We have taken a gamble here to test a few, the best candidate is 0208 213 012 this fits some big engined volvos and has the same connections and electrical properties,


The only difference is instead of the wide plastic screen in the intake there is a much finer mesh, they use this MAF on Ferrari but two of them


We found some on eBay for as little as $45 new but cheap copies, but even genuine Bosch is a load cheaper than Porsche price at $1000


I will let you all know how it pans out

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[wildcat]

Be most interested.  While its working well, its old and I'm considering options. After carefully inspecting the MAF, its obvious with the heat sinks etc. that this unit has a lot of potential complications due to heat, and I'm thinking when the wire gives out, its probably a short time before some other circuit in the system gives out as well. 

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[flash]

in working out the tuning on the supercharger, i learned a LOT about MAFs, and how they are incredibly touchy instruments.  the slightest thing amiss, and they don't send the right signal.  this is frequently the cause of failure at emissions tests.  it also results in poor performance, poor cold running conditions, slow starts off the line, poor fuel economy, and potentially dangerous high load lean conditions.   the airflow over the wire has to be just right.  it the screen in front is broken or changed, it disturbs the airflow and the readings change.  if the wire is dirty, the readings change.

 

it's not like the old days of carburettors and distributor springs, that's for sure

 

yes, the car may run, however, it won't run right if the MAF isn't right.  you should drive another tip car that is right to see what "right" truly is.  i'm willing to bet it will be an eye opener.

 

lol - of course that can be a very depressing experience, because then you'll need to run out and spend a lot of money.

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[wildcat]

Well I don't plan to run out and spend a lot of money, but I am considering a replacement before I have the kind of complications you've mentioned. I suppose in that light the fact the copper wire works at all is rather remarkable.  Thanks for your input on this.

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[flash]

no worries.  some simple tests would show you what it is really doing, and then you could make informed decisions.  pretty hard to tell when you are essentially poking around int eh dark.  i'm jammed for the next couple of weeks, but then i should have some time.  we could hook up the A/F and durametric and run some tests.

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[wildcat]

That's a possibility.  As its working with the copper, I'm inclined to try the platinum considering how well it is working.  Can't hurt anyway. If after that and time permitting I may take you up on your offer.

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