Fred
This is where the WOT numbers come in to play. This car is stock with a stag 1 kit, but the owner has switched to slightly smaller pulley. This person now needs a supermaf, but for now to compensate he has numbers in the in the WOT map above 4800 to compensate

 

WOT "compensation" only helps at the highest load values when the switch is activated..... below that the fuelling is going to be compromised depending on how much headroom is left.

 

Victor,


It would be intereresting to know just how much extra fuel can be thrown in by using the WOT map route. For sure what I do using the cruise map cannot work at those MAF values.

Even more interesting to know would be what MAF reading that curve would be reading if it had the correct rangeability. Maybe Jim or John can correlate that one. Either way it must be pulling like a herd of elephants from 4k rpm upwards.

Although it is counter intuitive, I have often thought that over gearing the blower to get it to kick in earlier might be a way to go to improve mid range pick up and then have a blow off valve to avoid excess pressure at high rpms as long as the blower is not oversped. Indeed, doing this and setting the rpm limiter to 6k on auto models at least might even help protect the motor from the deadly 2/6 syndrome.

Regards

Fred

 

Fred
Simply put, the correct thing to do is contact Jim or John and get a SuperMaf. If I was to guess I would say about 550. Just for fun here is a plot from my car before I went supermaf

You may be surprised though how much fuel you can throw in using the WOT map on top of the standard map, but your shooting yourself in the foot by going this way. The problem is you can now reach these cells in 2 ways. You can tune these cells for an overboost mode when the MAF maxes out it's voltage, like seen below. But if it hits these cells in a Normal MAF voltage situation, than it will be super rich!!

Friday I was doing some power testing on the black car and blew apart the MAF boot At first I was bummed, but after realizing I had enough speed to coast back to the shop, and then saw what I did, I was actually laughing

So I had to get the stock white 89 S4 out, which I haven't driven in a long time. What a dog!! I cannot believe the difference in power between the two cars. From bottom to top, what a difference. So I hooked up the sharktuner to see the numbers .... The supercharged black car hits 100% on a stock MAF at 4500rpm. The stock white car never even comes close. 40% on the MAF is about all I can get to. Which would be about 212 on the plot below. Over 80% on those little 19lb injectors though haha

 

Victor,

I have ran this boot on my car since day one. It works really well and is only 50 bux....

http://www.034motorsport.com/fabrica...b1mh59ftkprs43

 

Mike
thank you for the heads up on that. I actually new about those already, and I ordered a couple of them on Friday right after it blew. I'm just hoping they still have them

 

Quoting from John's post above:

Cheers, Jim

 

Just talked to the guys there and he says he hasn't had one in years and to keep looking on the net for them.

Damnit, this would be prefect too. Just found a blew some hoses off mine.

 

Sean,

George Suennen has a special boot design to withstand boost on his awesome beast. I cannot remember where he got it from but I am sure he would share that info. I think the heads would disintegrate before his boot!

Not wanting to teach granny to suck eggs but on my boot I use a jubilee clip very lightly pinched on the side connections and some silicon RTV to help seal the joint. whether it would make any difference on a boosted 928 no idea

Victor,

At least you hav eproved without doubt you achieved sufficent boost to blow the bugger!

Indeed with a n/a set up [and maybe our air temps] I struggle to get decent MAF numbers. Initially I thought it wa ssoemthing wrong with my motor but it seems mor or less typicaly behaviour-or so it seems.

I would surely like to drive my car with the MAF curve you posted! At least I get to play in the Cayenne as well but it would be kind of nice to have the output in something that weights about 3/4 of a tonne less and does not have a drag coefficient of a large brick.

Regards

Fred

 

So I put in the maf air straightener. It solved my problem to the point I don't notice the surge anymore. Victor came down here with his new car (let him post about that, it's something else!) and tuned it while we drove for an hour. Runs great.

Note to WBO2 owners. You can blow the fuel pump fuse if you sit with the key in the on position while you are programming your digital display for boost, etc. Victor supplies a digital display that is custom configurable and we blew my fuse while we were programming the display. Little 10 amp fuse couldn't take the eternal preheat of the sensor I guess.