B951S

As far as stand alone MAP bases systems, basically all your aftermarket systems (fulll blown Motec's, SDS, Link1 and 2 etc) use MAP. Piggback MAPs (Link AFM) can have the issues mentioned here. Stand alone MAPs are usually smooth and accurate once programmed. Ask any of the guys here with stand alone MAP ECU's and they can attest to stock like or better drivability once set up. However, the cost and effort to put one in is far greater than MAP based piggback like Link AFM. For a piggback with best drivability, a MAF would give you better drivability out of the box.

fast951

Most 951 owners already upgraded their injectors. So why charge them for something they already have. If you do not have injectors, we can provide them or you can mail order them directly yourself.

Stock WG if in good condition can hold 17psi.. However, a dual chamber WG is much easier to control

Tom M'Guinn

417 rear wheel horsepower for $3000 on an otherwise stock motor? Has anyone installed the kit on a stock car and obtained these results? At what boost pressure? At what octane?

v944god

fast, how much hp/tq does the stage ii and stage iii have? and at what psi?

i'd like to run high hp numbers w.o. high boost levels.

lets say this includes boost controller, cat-back, and new wastegate.

fast951

v944god, the dyno charts are on the website...

If you want high HP w.o. high boost, you need to run high RPM (over existing red line). I'm not in favor of running high RPM on a 951...
The 951 engine was not designed to run high RPM

Also, plan on spending big $$$ on engine work to allow it to rev higher... And reliability will be questionable...

jsonnen

Hey Tom, I beleive those figures are at 17 psi with 94 octane, but i'm not 100%
sure! As Fast951 said , you can crank up stage 1 to 19 psi and run around 360 rwhp! 337 rwhp is at 17 psi. Still an amazing deal!

v944god

Reliabilty is an issue. But I'd like to shy away from any type of engine work.

So how much psi are stage 2 and 3 running? and is it racing or pump gas?

But it sounds like it has great results.

FSAEracer03

Go with a MAF setup. Part of the reason why MAP systems stumble and are harder to properly tune are becuase of an inherent lag in information time. Think of this on simpler terms and you'll see what I mean. Air pressure read isn't fully consistent with air pressure entering the heads. This fluctuation causes a slight variation. However, using MAF you get real-time info on how much air is entering. MAF also naturally accounts for variations in static air density (denser air means more airflow across wire, cooling it slightly more). It is the ebst system to go with if you do plan to change from AFM.

either way, good luck!

turbo951fan

I have a set of 55 LB injectors for sale, inc. Guru racing ballast resitors and installation instructions. Make me an offer

B951S

I think its important to make the distinction between MAP based stand alones and AFM replacement systems. I don't think any one here with a MAP based stand alone has drivability issues, please chime in if you are. Many OEM's use MAP systems with no drivability. A friend sent me this article from a magazine.........

Types of Load Sensors
A load sensor is an essential part of any production car EFI system. The load sensor serves to inform the ECU of the amount of air being consumed by the engine. This enables the correct quantity of fuel to be injected and helps determine the appropriate ignition timing for each situation.

There are two different types of load sensors - airflow meters and MAP (Manifold Absolute Pressure) sensors. Leon Vincenzi of Adelaide's Awesome Automotive suggests that today's car manufacturers favour airflow meters because they offer greater tuning accuracy.

"This enables tighter control of emissions," he says.

There are three different types of airflow meters.

The most commonly used airflow meter in late-model EFI cars is the hot-wire airflow meter. The hot-wire airflow meter incorporates a thin platinum wire mounted in the intake system prior to the throttle. The mass airflow into the engine is calculated by the amount of current required to heat the wire to a predetermined temperature.

Many older EFI systems - such as the BMW Bosch system seen here - employ a vane-type airflow meter. In this arrangement a pivoting flap is mounted in the intake system prior to the throttle. This pivoting flap opens as engine airflow increases; the ECU receives information on the flap angle. Mass airflow into the engine is determined by the flap angle and the input from a separate intake air temperature sensor.

The third type of airflow meter is the Karman Vortex, as used on many Mitsubishi engines. The Karman Vortex meter operates by producing internal vortices. An ultrasonic transducer and sender measure the frequency of these vortices. Unlike most hot-wire and all vane airflow meters, a Karman Vortex meter sends a frequency output to the ECU.

A MAP load sensor operates on a completely different principle to an airflow meter. A MAP sensor is a pressure sensor that's connected via a hose to the intake manifold downstream of the throttle. In the case of a naturally aspirated engine, the MAP sensor reads manifold vacuum only, while those fitted to forced induction engines measure vacuum and boost. The output of the MAP sensor is fed into the ECU where it is referenced against revs and intake air temperature. These inputs allow the ECU to calculate the engine's mass intake flow, enabling it to provide the appropriate fuelling and ignition timing.

Pros And Cons of Both Types of Load Sensors
The airflow meter is widely regarded as the most accurate type of load sensor. To achieve the optimal air-fuel ratio, it's the mass of air entering the engine that it is critical to determine.

"The airflow meter gives a grams of air per second measurement of intake flow, which is exactly what the computer needs to deliver the right air-fuel ratio," says Leon Vincenzi. "It's not like a MAP system where it arrives at an indirectly calculated value."

Hot-wire meters provide superior transient response to vane-type meters. Vane-type airflow meters are better damped and offer greater smoothness.

But Leon Vincenzi says the MAP sensor offers even more advantages in terms of transient response.

"You can feel that the earlier MAP-sensed V6 Commodores are a lot snappier than the late airflow metered V6s," he says.

Further advantages of MAP sensors include compactness, no requirement for maintenance and potentially greater reliability. Another important point is since the induction air doesn't have to flow through a MAP sensor (as it does with an airflow meter), it poses no intake airflow restriction, allowing optimal torque and power to be generated.

An Aftermarket Perspective
When modifying an EFI car (with extractors, an exhaust and air intake, for example) the MAP load sensor arrangement typically gives the biggest power gain. But this does come with some drivability trade-offs.

Leon Vincenzi uses the example of Holden Commodore V6 to illustrate the characteristics of a MAP-sensed vehicle with breathing enhancements.

"You can do extractors and exhaust on a late VS-onward Commodore [which uses an airflow meter] and the management system will know what's going on and it'll maintain about the standard air-fuel ratio.

"But the earlier cars [with MAP sensors] will be running off the same base program - oblivious to the effects of the exhaust changes. That means there'll be a mixture variation at high load - it goes leaner. This leaner mixture helps to make power in itself, but you'll often end up with flat spots."

Note that, in addition to giving leaner air-fuel ratios at high load, the MAP sensor allows the engine to breathe without restriction. In contrast, as the engine's airflow capacity increases, so does the restriction of the airflow meter.

According to David Alexander of Sydney's Silverwater Automotive, MAP sensors also have advantages in high power turbo applications.

"Some modified turbo engines that run airflow meters can suffer mass flow reading issues. When you've fitted a big turbo you can get a lot of turbulence that affects the airflow meter at idle and during low speed operation. This can be very tough to fix if you aren't aware of exactly what's going on. When you make a speed-density calculation [as you do with a MAP sensor arrangement] intake turbulence isn't an issue," he says.

Yet another advantage of a MAP sensor induction system is its resistance to engine backfires. Airflow meters, particularly vane-type airflow meters, are very susceptible to backfire damage.

Various programmable management systems are available with external 1, 2 or 3 Bar MAP sensors while other aftermarket ECUs come with an in-built MAP sensor. In the latter case, note that running a vacuum/boost hose from the engine bay through to the cabin (where the ECU is typically mounted) is illegal in some areas. MAP sensors in production cars are invariably mounted on the firewall or directly on the manifold.

Having said all this, the airflow meter has a few advantages up its sleeve...

"An airflow meter system gives more modification flexibility before you have to re-chip the ECU - it's measuring the actual airflow of the engine," says David Alexander.

"If you make an exhaust change, for example, it won't upset the ECU's operating characteristics. There may be other hidden functions in the ECU that override that advantage, but that's another whole issue...

"Also, in most cases, an airflow meter system is more accurate and requires less computer brainpower - it doesn't have to make constant calculations like a speed-density system. Airflow meter systems generally also require a bit less tuning," he says.

Airflow meters are also more suitable in applications where hot cams are used. Big cams can cause pressure fluctuations in the intake manifold at light load. These fluctuations are known to confuse a MAP sensor.

"You find that vacuum drops at low rpm and the engine will run too rich," says Leon Vincenzi.

One of the biggest benefits associated with a MAP sensor is that is poses zero intake flow restriction. While this is a valid consideration, Leon Vincenzi points out that many people ignore that availability of 80mm airflow meters that flow extremely well - the Cobra Mustang SVT engine (pictured here) comes standard with a 80mm airflow meter.

"I know a lot of people rip out the screens or honeycomb in airflow meters," says Leon Vincenzi. "All that does is stuff up their intake flow readings, particularly in the case of airflow meters that have a thick internal honeycomb.

"Another thing people forget is that they can run twin airflow meters if airflow restriction is a concern."

Final Words From the Experts
David Alexander suggests in most instances the decision to go for an airflow meter or MAP sensor is not terribly important.

"Each approach does have some subtle advantages but so much comes back to how well it's tuned," he says.

In contrast, Leon Vincenzi suggests a different approach for modified forced induction and naturally aspirated engines.

"MAP sensors are easier to set up on a forced induction engine - you can get a very good result quite easily. But I tend to lean toward airflow meters for serious naturally aspirated engines," he says.

"The best approach, though, is to rely on a MAP sensor for transient response and an airflow meter for steady-state conditions. We've run a few Commodores with that set-up and it works brilliantly."