Policies
and Warranty Statement
1995 993 and VarioRAM Intakes
The 1995 manifold is essentially the same as the 92-94 964 manifold
with two major differences:
The VarioRAM, however, is completely different. Note
that both have a primary plenum above the primary runners (or
stacks).
From that point down they are essentially the same. Above
that however, they are completely different.
As you may know, all 964/993 motors 2.7 Boxsters and 996 motors have a resonance chamber. This allows the pulses to flow from the left (1-3) bank plenum to the right (4-6) plenum. It is opened and closed by the computer depending on throttle position and RPM to maximize volumetric efficiency (how much air gets into the combustion chamber). The VarioRAM goes one step further. Whereas the 1995 993 has an upper and lower crossover tube (upper with the throttle body and lower for resonance), the VarioRAM has a total of eight connections, a second throttle body (opened only above 1/2 throttle) and a secondary plenum. Here's how it works:
At high RPMs and above half throttle it essentially works just like a 1995 993. The lower throttle body and crossover look like the upper one on a 95 993. Now for the upper - the upper throttle body flows to a central plenum which branches out into six runners. These runners then dump into the primary plenum to join the air coming in through the lower crossover. In effect it acts just like the lower throttle body so you get lots of air and the effective runner length is just the lower (primary) runners or the distance from the primary plenum to the intake valve. T make a long story short the VarioRAM is no better than the 993/964 intake, in fact perhaps a little worse in theory because the air coming through the top runners has further to travel and the whole assembly is pretty heavy (10 lb.?).
Now for the tricky part and why they bothered. At low RPMs (below
5200)
the top runners are connected and sealed to the lower runners.
This
has several effects:
1) The intake runner length is
MUCH longer, about 9" longer in fact, which means that the optimal
charging
RPM for tuned resonance induction is much lower. That means that
more air will get into the cylinder at lower RPM. This
effectively
boosts low end torque, below 4000 RPM there is a notable difference.
This
is also because the air velocity through the single throttle body is
increased,
which aides in cylinder charging (same old how much air).
2) The lower throttle body is completely closed off from the intake system, as are the primary plenum and resonance chamber. This is, again, a good thing at lower RPMs. It is particularly bad, however, at high RPMs (above 5200 and more than 1/2 throttle) since only the upper throttle body is operational, so no matter how hard you mash the pedal you only get about 1/2 throttle! We recently had a customer who refused to follow directions and hooked up the VarioRAM vacuum canister incorrectly. He found that the car was absolutely dead above 5200 RPMs, like 180 rear wheel horsepower. When the problem was corrected his dyno showed 265 at the rear wheels (I think that's a bit optimistic but you get the point!)
Here's how it physically works:
This is a picture of the VarioRAM opened up with the trumpets
retracted. In the lower portion is the primary stack. In the
upper
is the primary plenum with trumpets.
This is the VarioRAM in it's normal position, trumpets extended. The rubber seals seal against the individual intake runner completely blocking off the primary plenum, secondary throttle body and resonance chamber.
Now here are pictures of the trumpets closed then open. A pair of vacuum actuators (one per side) retract the trumpets so the primary runners breath from both upper and lower intake tract and throttle bodies.
Note: The DME operated the VarioRAM only at above 1/2 throttle and above 5200 RPM so it is difficult to bench test.
Look at the torque figures though:
| Model | Torque at 4000 RPM (Ft-Lb) | Change | Max Torque at 5000 RPM (Ft-Lb) | Change | Max Power at 6200 RPM (HP | Change |
| 95 993 (type 06/07) | 199 | 243 | 272 | |||
| 96-98 (type 21/22/23/24) | 238 | +20% | 251 | +3% | 282 | +3.5% |
There are three production motors that porsche made from 1994 through 1998.
The first is teh M64/05(06) (06) differs only in the size of the alternator pully, used to drive it faster for teh tipronic transmission. This engine is the same for all markets and is rated at 272 HP. The US models have an air blower for emissions in all cases as to the M64/23(24) models.
The second engine is the M65/21(22), Non-US varioram, which is the idential engine to that above with a few VERY siubtle differences. The 96-98 VarioRAM is rated at 10 more HP than the 94-95 993, at 282 HP. This is because of the valve size and revised tuning. VarioRAM engine intake/exhaust valve size is 50mm/43.5mm vs 49mm/41.5mm. This has nothing to do with the VarioRAM and only to do with revised tuning and the larger valves. Head castings are identical. When I say subtle differences I mean it. For example teh chaijn tensioner cap is made of aluminum rather than magnesium, the pins for the chain ramp take an 8mm allen rather than a 6mm allen to remove and I beleiv those are the only differences, other than the intake manifold itself. This engine uses teh SAME electronics package as teh 95 motor, 55pin DME with OBD-I electronics.
The third engine is teh M64/23(24) 1996-1998 US engine, which is identical to the European M64/21(22) with the exception of the DME and DME harness. The DME is of the 88 pin variety (similar to 97-99 Boxster and 99 996 and early GT3) and does NOT have a removable chip. 97/98 models may be reprogrammable but the chips cannot be swapped out. THis is generally expensive.
M64/21-24 all make the same power the only difference is in the electrnics. This is irrelevant if the car is not modified.
The M21/22
engine is most desirable since it has the VRam intake and the OBD-I
electronics. As mentined the VRam ONLY changes intake runnner length
below 5K RPMs. Beyond 5K RPMs it is fuctionally identical to the
94-95 intake (M64/05(06)), other than being about 12 lbs heavier.
So what
happens if you slap a Varioram intake onto a 95 M64/05 Engine, you get
essentialy an M64/21 engine with slighly smaller valves. The
valve size is wirth 2-4 HP and the remainder is tuning, so with chips
and a stock exhaust you get about 285, with a ram maybe 288, whatever,
you can;t tell the difference driving them. We have chips and
wiring available for this conversion and can tell you what additional
parts (like the crtuise control motor bracket) are required. THis
can be done without removing the engine.
The advantage of the /05 motor is that it is easily tunable, i.e. if you want to slap in some RS or even more aggressive solid lifter cams, RS valves (53/43) when it's due for a top end that is easily done and worth 30HP or so with the right exhaust. We call this the RS+ kit (with solid lifters) and it makes about 330 on pump gas, 338 on race fuel and bumps RPM limit up to 7200.. WHile you can do that with the /23 motor tuning it is a nightmare.