edz968s

Carl, the current set up is oem injectors, standard crank, 2.24" grooved head pulley with double sided belt, which incidentally I am getting no belt slip, but therein lies the problem. With the boost now knocking on 6-6.5 the engine is running out of steam approaching 6000rpm, hence the questions as to wether the S2 injectors would alleviate this.
My a/f guage is an analogue type

edz968s

The new and improved 968 sc kit, where will that put the kits already out there? Will there be upgrades available.

Carl Fausett

Of course! They will be available, and optional. You can upgrade, or stay where you are.

Keep in mind that the new Stage II kit is coming out as an "advanced" kit. To please the racers, I'm going all-out for boost and performance. Some changes to the fuel system will be required to fuel it. They may take the form of a complete engine management system (like the TecGT we recommend and sell), larger injectors, a larger fuel pump, or any combination of the three.

Just advising that the stock fuel system will NOT be able to keep up with the air flow of this Stage II kit. That's what the Stage 1 kit is for.

On the 968 that I am doing here in the shop, we will be using the TecGT for engine management and larger injectors. We are going to go with the stock fuel pump unless/until we learn it cont keep up.

MN

Carl:

Will the new-and-improved 968 Stage II kit require any internal engine changes/modifications (special head gaskets, lower compression)?

MN

Carl Fausett

Good question. As with the Stage 1 kit, no changes to the engine internals will be required.

IF you are already replacing your head gasket for some other reason, I would recommend at that time that you upgrade to our GCS gasket which seals better and handles more boost. But it is NOT necessary to replace a head gasket that is already working well. I do not believe in prevenative head gasket replacement - leave them alone until they fail.

Here is the information on the GCS gasket:
http://www.928motorsports.com/parts/gcs_head_gasket.php

MN

Thanks for the reply.

But if the Stage 2 kit gets pushed to its limits, I assume at one point the compression must or ought to be lowered. Do we know at which boost pressure this becomes necessary or recommendable?

MN

Carl Fausett

"Must" be and "Ought" to be are wildly different.

As long as the engine is fueled and tuned correctly, detonation (pre-ignition) should not occur and there is no "Must" to changing the CR. The key is a good tune by a competent tuner. No Air Fuel ratios higher than 11.5 to 1 anywhere, and 10.8 is preferred. I have seen 14:1 CR engines running 40 lbs of boost on ethanol. Gasoline is trickier, you have to know what you are doing. At some point the stock head gaskets may fail just from the increased cylinder pressures, but that's because of the power being produced, not just the CR.

"Ought" is another matter. If I was building an engine for boost right from the start, then I am no longer talking about a kit. And yes, if I knew I was going to build a high boost (10+ psi) application, then I would make changes to pistons/rods and that would include lowering the CR.

I will have answers within about a month now as to what is the max PSI this kit will produce. Then I can answer your question more definitively.

MN

Thanks Carl. I am sure that many here are anxiously awaiting the reveal of the new Stage 2 Kit.

MN

Carl Fausett

...as am I. I designed it for simple installation and street use.

Now that I see how strong the desire is to "go nuts" with it I think there is a market there for a built-out bolt-on kit. I will provide.

Carl Fausett

Just in - these pics of our kit on a 968 at the Nürburgring

Jfrahm

Must be running a different ECU. No MAF.

Carl Fausett

This is because the hot-wire sensor is old technology and cannot read high air flow rates.

There is a little headroom in the design - so when we run up to 6-8 psi of boost the MAF can see and respond to the higher air flow. But it will hit the ceiling shortly after that - where there is more air and it simply cannot measure it.

Hot wire sensors are old technology. Remove the MAF and use a MAP sensor instead (like Motec, Electromotive, Halltec, whoever) and then you can measure (and respond to ) all the increases in air flow.

The MAF is a large part of the problem why you cannot get enough fuel up top, because it simply stops measuring. It has hit its limit. The next problem is even IF it could see the increase in fuel, the LH Computer and EZK are not designed to be adjustable for boost anyway.

So... low boost kits must operate under these limitations - like Stage 1.

High boost kits will require the replacement of the computers and the MAF with systems that can see and understand what to do with boost.

Eric_Oz_S2

There is a way around the limitations of Maf flow. The wot maps can be set to compensate at wot. In practice what this means is you are removing the Maf component of the injector pulse calculation and therefore need to further increase the wot maps above above the Maf flow limit. Once you exceed the load value in the pt maps itgets more difficult. At 7 psi on the s2 dme the afm is at it's limit at 5000rpm. You can retune via ostrich and tunerpro to a point ( probably around 7psi). After this I suspect standalone ecu would be required using a map sensor.

pudjnr69

Car is at the dyno. Running the larger crank pulley, intercooler, upgraded supercharger, no MAF, aftermarket ECU, dropped compression to 10:1 - and made 230kW (up only 20kW) at the rear wheels. Only making 5.5psi boost versus 4.5psi on the original kit and 11:1 compression ratio.

Boost is dropped off over 6,000rpm.

Something is up - any suggestions? Is there a by-pass on the dump valve at which at 5.5psi it vents?

The supercharger should be running at something like 30 to 40% higher speeds and therefore making more boost.

Eric_Oz_S2

I know that Raptor don't publish their compressor maps, but do you have any confirmation from them what sort of flow and pressure you should get at the current SC rpm? They say 10 psi up to 4 litres, but no indication of what rpm. Did they give you any more info?

With the lower CR, you will be putting more air into the cylinder, which by itself will reduce boost as flow has to increase.

What sort of bypass valve have you got? I presume you don't have a boost limit valve.

Do you have the boost curve from the dyno?

You're right it does sound low. If the bypass valve is not leaking it must be the head unit (presume there is no belt slip now?)