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Safari Snorkel Performance


For years there has been a good deal of discussion relating to the engine performance once a snorkel is installed. This is primarily due to the fact that people report a variety of experiences ranging from a drop in performance and fuel economy to a marked improvement in performance and fuel economy - and of course every permutation and combination in between. This of course leads to confusion....

It is important to understand that engines and induction systems are not all equal. Neither of course are snorkels. Given that a combination of vehicle, engine type and snorkel model delivers a certain result does not mean that a different vehicle with a different snorkel model will achieve the same result.

The primary reason one fits a well designed snorkel to their Prado is to ensure safer water crossings and lessen the amount of dust ingested into the air intake and air filter system. Any performance improvement should be seen as a free bonus. Indeed, even if there is a slightly negative affect on engine performance, it is a small price to pay for peace of mind.

There are many factors that affect the choice of snorkel for a vehicle though these are best discussed in another technical article, but briefly, some issues (other than the obvious ;-) that may not spring to mind are the ability to rotate the air ram (if you ever intend to be caught driving in snow where a forward facing air ram will quickly block with compressed snow and starve the engine of air - with possible engine damage) or indeed the ability of the snorkel to separate rain water from the incoming air prior to reaching the air filter.

But back to the thrust of this article..... In terms of engine performance, the 4.0L V6 in the 120 Series Prado is an interesting one because at 24.1 lb/min of air, this engine has the highest air flow requirements of any petrol engine in the Land Cruiser line-up. Indeed greater than all the diesel engines except for the 1HD-FTE (not available in the 120 Series Prado). See chart below:

Engine
Maximum Mass Air Flow
4.0L V6 Petrol
24.1 lb/min
4.7L V8 Petrol
23.6 lb/min
D4D Diesel
23.5 lb/min
1KZ-TE Diesel
17.9 lb/min
1HD-FTE Diesel
29.9 lb/min

A straight forward test is to see the affect of a snorkel on engine performance under the worst possible conditions. That is, stationary on a chassis dyno. This will highlight any deficiency of the snorkel system when compared to standard because the test is conducted with zero air velocity (hence zero positive pressure over atmospheric conditions) to the snorkel air ram. Much like holding your open hand out of the window of a fast moving car, the air ram takes advantage of that additional air flow to move the point of zero positive pressure further inside the snorkel body, thus improving air flow further.

An automatic V6 Grande was used as the test vehicle and 3 full throttle power runs (in 2nd gear) were conducted on the dyno to determine the standard power at the wheels. The best power and torque curve was plotted below (124.7 kW). A Safari SS186HF snorkel was fitted to the Grande and another 3 power runs were conducted. In this case, the lowest power curve was plotted over the standard power curve (127.2 kW).

The result was a worst case net gain of 2.5 kW at the wheels or 2% improvement. This indicates that the Safari SS186HF snorkel delivers a less restrictive air inlet than standard. This also suggests that at speed, the improvement will be greater, however it is all but impossible to conduct accurate and repeatable tests when the vehicle is speeding along. None the less, on the 120 Series, the improvement in engine performance is real and quantifiable under worst case conditions.


What about the Turbo Diesel?

The air intake system on the 1KZ-TE turbo diesel is a good deal more restrictive than that on the 4.0L V6 engine. Just looking at the components used to source air into the air cleaner assembly, the difference is quite startling.

On the turbo diesel for example, air is sourced through a long and narrow air duct shown below.

The air entry is quite small compared to the size of the duct where it meets with the air cleaner body. A comparison is shown below.

On the petrol engine however, there is no such duct. Only a wide and free flowing rubber scoop as shown below from two different angles.

Given the fact that the petrol engine draws a significantly higher mass of air, the sizing is probably appropriate. However, given the performance improvement seen with the petrol engine, the reduction in air restriction for the turbo diesel will be even greater in comparison to the standard arrangement.


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