Torque Developments Blog

As part of our Stage 2 upgrade for the Supercharged Lexus iS200, we incorporate a larger intercooler than the standard TTE item.

When air is compressed (such as by a supercharger or turbocharger) it’s temperature increases (see BoylesLaw) and loses density thereby reducing the amount of oxygen available to produce power, so we can see that reducing the air temperature at the back of the intake valve is crucial for increasing engine performance.

This is why intercoolers are used in an attempt to reduce and control intake temperatures. Unfortunately the presence of an intercooler also creates a restriction to airflow which in turn reduces power so we therefore have a bit of a paradox which is generally dealt with by compromising the airflow efficiency in an effort to keep the temperatures down.

The two critical design features of an an intercooler are it’s thermal efficiency (how good it is at reducing temperatures) and it’s air flow efficiency (how good it is at transferring air with minimal internal losses).

Having very good airflow testing facilities in-house, we were able to test all of the branded intercoolers on the market and found that they varied dramatically in terms of air flow efficiency so we decided to think about how we could improve this without reducing the size of the intercooler core.

Traditionally, a larger core gives a cooler charge but more resistance to flow, so we designed an aerodynamic and plate for the core which significantly increases the air flow through the core.

We also wanted to increase the volume of intercooler core to maximise the cooling capacity so we designed a intercooler which is around 250% larger than standard. We paid particular attention to the quality so we ensured that the end tanks were properly cast and aerodynamic shaped too. We increased the size of connector spigots from 50mm to 60mm so that the Katana intercooler can be used on very high power applications. We also considered the packaging to ensure that the intercooler could be installed without cutting the body work and with minimal fuss.

The end result was an increase from the standard TTE intercooler of 123CFM to the uprated Katana intercooler of 161CFM which is an increase of 30% !!!

On the chassis dyno we found that with no other modifications, changes or tuning, we saw an increase of 0.1 bar of boost pressure (due to the aerodynamic end plates) and a substantial increase in torque throughout the power band (see graph below).

We are very pleased with the results of an additional 20 lb-ft at the hubs, and the Katana high performance uprated intercooler for the supercharged Lexus iS200 can now be bought at www.tdi-plc.com/catalog/product_info.php?cPath=107_197_214_384_392&products_id=4117

Here’s a picture of the intercooler in place

Here is the performance certificate without any tuning or adjustments being made. Very impressive!

because of the science and technology deployed in the Katana intercooler, we are confident that it is currently the best in terms of effectiveness and quality.

The standard exhaust manifold is very restrictive and is detrimental to performance, fuel economy and engine reliability.

The standard manifold has exceptionally small primary pipe diameters (probably to assist a fast warm up of the pre-catalytic converters), and the primary pipe lengths are too short (probably due to packaging concerns) for optimum torque. The manifold also includes pre-catalytic converters which are restrictive and known to fail internally.

The first stage of our development process was to accurately measure the camshaft timing so that we could run some calculations through our modelling programme to determine the ideal theoretical primary lengths and diameters, the secondary lengths and diameters, and the collector lengths and divergence angles.

Because of the packaging issues and design of the downpipe/main cat pipe, we could not implement the ideal secondary collector length so we chose to introduce pulse tuning loops in the desired location of a secondary collector. This proved to be an acceptable solution because it provided easy interchangeability with the standard manifold and gave us a good performance increase.

Dyno testing was carried out with various combinations of pipe lengths and pulse tuning loop locations, and the final design was signed off.

The improvements in power and torque makes it ideal for all fast road applications, and for any intended race use where uprated engine internals are deployed.

Benchmark testing was carried out competitive products, and we were pleased to note that the Katana exhaust manifold outperformed the other manifolds by a very significant degree.

We were not surprised by this as the Katana manifold was (and still is) the only high performance exhaust manifold for the Lexus iS200 which has had some science applied to it’s development.

Other concerns were raised about the other manifold such as incorrect pipe dimensions, quality of manufacture, slip joints instead of being a one piece construction, the collector pipes being squashed together instead of having the correct divergence angle.

The Katana exhaust manifold can be purchased at www.tdi-plc.com/catalog/index.php?cPath=107_197_214_384_385

Here is the Katana manifold for the Lexus iS200 showing the pule tuning loop pipe

Here you can see the difference between the standard manifold and the Katana exhaust manifold for Lexus iS200.

Here you can see the difference in collector design between the Katana manifold and that of a competitor. Note the poor design of the competitor.

Here you can see the difference between the Katana and the competitors manifold. Note the sharp change in in primary pipe direction which slows gas speed.

The Katana manifold can also be heat wrapped for thermal insulation

Here’s a picture of the Katana high performance exhaust manifold installed on a Lexus is200

The TTE supercharger system for the Lexus iS200 is a very well established and popular conversion for this superb but lethargic car.

We have installed a great number of these supercharger conversions, and one point were doing one per week.

The TTE supercharger system is available for sale at http://www.tdi-plc.com/catalog/index.php?cPath=107_197_214_384_388

We have had the opportunity to develop a number of upgrades to extend the performance characteristics of the TTE supercharger system, and this blog is all about our stage 2 upgrade.

Following on from our theoretical suspension calculations, we took the car to Brands Hatch circuit for testing and fine tuning the of the geometry.

We used the Race Logic V Box for data logging/capture so that we could accurately analyse the results. The data from the V Box showed that the car was still showing strong lap times even though the drivers were still getting to grips with the significant and fundamental changes that we had made.

The car was pulling more G’s than we had expected through certain corners which led to uneven tyre temperatures, so we implemented a geometry correction to compensate for this.

With some subtle tweaking of the ant roll bar lever lengths and damper rates to suit the pilots style of driving, the car was now ready to go racing!

The revised suspension has resulted in the car being 2 seconds per lap quicker over it’s previous best times, which we consider to be a resounding success.

These components along with other more road orientate suspensension parts are available for sale and can be see at: http://www.tdi-plc.com/catalog/index.php?cPath=107_108_332_333_342

Based on the result of the calculations from the mathematical model, we modified the ride heights, spring pre-load and roll bar leverage to provide a weight distribution variance of no more than 5% at 1G force. This was calculated to make the car “easy” to drive.

At this point the car has an ideal “workshop” set up and is ready to be tested at the track.

We installed the TEIN Super racing suspension components and set the ride to the calculated optimum heights.

We then measured the static weight distribution for the chassis alone and then with the simulated weights of the driver and heavy fuel loads.

Armed with this information we were then able to calculate the Dynamic Index for all possible load conditions.

The next step was to piece together all of the data into one linear mathematical model in order to estimate how the chassis would distribute ground pressure when operating at G Force conditions.