We have prepared two cars for Turbo Tin Tops and have a third in build. Andrew Marson’s AC500 had been a successful race car, it was turned into a rally car and now is back as race car. We can get 300bhp from the 1400 engine by fitting an S260 turbo with relevant injectors mapping and fuel pump but we now realise that it is very temperature/fuel related.
The second car is another ex Trofeo AC500 that has been raced in Scandinavia. It has carbon fibre doors, front wings, bonnet and tailgate, so is 60kg lighter. Again the engine mods should have brought it to 300bhp but many small issues have stopped us seeing that power. The biggest issue is that the intake air temperature is some 20 degrees C higher than the other car due, I believe, due to the front mount intercooler that looks the business but doesn’t appear to flow air and cool the charge. I have always said that there is little wrong with the standard pair of side mount intercoolers.
Both cars have 60litre FIA spec fuel tanks which gives them enough fuel for the 40 minute races, plus a high flow fuel pump which is vital for over 260bhp.
We have done what little testing we have done on Marson’s car. We started with £5 a litre MSuk legal race fuel and had very little ignition knock back. We moved to Super plus pump fuel and lost something like one and a half seconds a lap. Our second test was wet and there was very little knock back, I made a big mistake.
Come race day it was the hottest day of the year so far and the ignition knock back on both cars was horrendous. The hotter the engine and the charge gets, the more the knock sensor retards the ignition timing to save the pistons. From what I can see, and I don’t have the full data available to me the Marson car was running at something like 285bhp and the Kennedy car at only 270bhp.
At first sight the front mount intercooler really doesn’t work. Why do Porsche and Ferrari use side mount radiators? because the air flows into the wheelarches which are low pressure areas. We need to do some proper airflow testing and my gut feeling is that we need to develop a competition version of the standard production intercooler set-up and fast, we need both cars on the full 300bhp that we see on cold engines.
