968workaholic

Don't forget about the checksums and to turn off the six minute timer in the binary code when your making chips

Eric_Oz_S2

Yes I have heard varying comments about whether or not the checksums are used by the ECU. My Promax chip in my S2 doesn't have the correct checksum, and it appears to run fine, but the 968 may be different. What is the 6 minute timer about?

If you go standalone, it would be prudent to keep knock sensing. For more power, why not use a custom headgasket to reduce the CR and then up the boost? I have heard that tuning with the RRFR is difficult, in that because the 968/S2 engine needs more fuel in the midrange (because of the increased VE). The stock maps reflect this, so you end up multiplying the effect more at lower boost and getting a rich midrange. In effect you have 2 different shaped curves for the fuel map and boost map and are trying to draw a straight line through both - which is never going to work perfectly. The only solution to get this right is go standalone or re-write the Motronic maps (which is my plan). Once you ditch the RRFR, i presume you will need larger injectors - at least that is what was required on a recent installation on a 968 that I am aware of.

I am also considering bleeding the boost off using the 928MS valve just upstream of the intake. Not very elegant with a MAF or AFM though, as you need to tune as if there is less air going into the engine. Another option is to use a restrictor plate on the SC inlet. I expect this would increase the heat gains somewhat though.

Are the 928MS bleed valves noisy in operation?

Carl Fausett

The engineering on the new crank pulley for the 968 kit is finished, and I have my manufacturing bids.

If I order 5 of the crank pulleys, I can get them at $393.00 each. If I order 10 of them, I can get them for $315.00 each.

The new crank pulley is 6.125" in diameter, which will turn the impeller at 46,838 rpm at 6500 crank, when using a 2.55" SC pulley. There will be no belt slip in this combination.

Currently, 928MS Kit owners are running a 5.11" crank pulley and a 2.35" SC pulley to spin the impeller 42,402 rpm at 6500. Most report 5 psi of boost from this setup.

Experience with the 968 has shown us that a change 922 impeller rpm translates to 1 psi.

My best estimate of the boost made from the new Stage II crank pulley and a 2.55 SC pulley is 9-10 psi on an otherwise unmodified 968.

Be advised that I am certain the stock fuel system, even with our FMU installed, will not be able to fuel a 10 psi boost kit. Larger injectors will be needed, and quite possibly a larger pump or modern engine management system.

My question for the forum is: now that we know the price of the new crank pulley, how many want one?

Lemming

Me!

I'm giddy to think what my little car would be like at 10 lbs of boost, not that I would ever try it

Guess that set of green top bosch fuel injectors on my shelf might come in handy sooner than later!

Carl, what is time frame for shipping?

Lemming

C'mon guys, you need one of these!

Carl Fausett

I have also emailed all the 968 kit owners who are not on the Rennlist to try to get them to order.

I'm trying to acquire the minimum number I need to start the machinist on the crank pulley.

Lemming

One thing to remember, if you go with the larger crank pulley, you can then also increase your SC pulley size to 2.8" and still have 5 lbs of boost at 6500 rpms, you don't have to run 9-10 psi.

Carl has a nice calculator at http://www.928motorsports.com/servic...tingpulley.php

Carl Fausett

A little feedback on the Kenne Bell Boost-a-Pump.

I am designing a supercharger kit for the 3.2L V6 in the Mercedes CLK, SLK and Chrysler Crossfire, and we have installed a Boost-a-pump in it. Like it very much so far, and at only $229, its less expensive than a new FMU, or a fuel pressure regulator, or a set of injectors.

I'm thinking it might be a sweet solution to getting more fuel for you 968 racers- and less expensive than a complete new EMS too.

Here is a link to it: http://www.kennebell.net/accessories...boostapump.htm

We are using the 20 amp Model # KB89067. There is a 40 amp model only $20 more.

Lemming

I spent the weekend at Barber Motorsports with BMWCCA this past weekend. It was hot, humid and sunny.

The car pulled well and ran strong. I did not have any issues with the external belt slipping but did change it after the track went cold on Saturday. By that time it had one dyno session and two track days on it and I was starting to see cords through the back side.

Sunday was great till the last session of the day. Just about everyone had left and a few of us had the track to ourselves. On the second lap out the internal belt broke and that was it. This means that two belts have now gone out on me I got approx 4 tracks days on the 1st belt and 3 on the second. Raptor had provided me with a Greddy BOV with hopes of extending belt life but it didn't. BOV was working fine and it sounded cool.

Jfrahm

Yikes! I did not know you were having internal belt problems. Do they think you are getting into surge on lift throttle? I was looking into a boost limiting valve plumbed into the intake tube near the line to the BOV.

My other idea was to tee off the vacuum/pressure line to the BOV and run it to a small regulator like is commonly used to control turbo boost. This would be set to allow the recirculating valve to leak above the preset pressure point. Normally full boost is delivered to the back side of the BOV so that under boost the pressure on both sides of the BOV piston is perfectly in balance, like Megan Fox on a yoga ball. If not all the boost pressure is allowed to reach the back of the valve, it will creep open as boost increases and it might also be more reactive to spikes.

Plumbing the BOV in closer to the manifold might also be wise. Mine is teed off the RRFPR and I bet the signal to it is not idea.

Cheers,
-Joel.

Lemming

The system was not surging, the BOV was working very well and was placed between the SC and the IC as instructed by Carl. The SC cooling fan runs as soon as I turn the car on.

I've pretty much decided at this point that the SC is coming off the race car.

Carl Fausett

No one pushed the envelope harder or further than you did, Tim.

I applaud all your efforts - everyone learned a lot from looking over your shoulder.

Lemming

Carl, I enjoyed working with your on the project. I believe that it has potential but my focus needs to be on racing and not so much on development. My plan it to put a new belt on the SC and either install it on my daily driver 968 or possibly sell it. The only reason that I would sell the SC kit is that I'm considering selling my daily driver 968 to get something different. The race car is once again going to morph, Franky III will be sporting 8 cylinders

Carl Fausett

I'm putting a belt in the mail to you today.

Lemming

Thanks!