View single post by NigelK
 Posted: 07-28-2015 09:39 am
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Joined: 07-16-2014
Posts: 171
Thanks Gordon. I've decided to go with the early Excel airbox setup (round hose attachment, clipped not bolted together) with a high performance K&N filter. While this setup is not original, it at least looks like the later GT / Lotus Eclat setup while being more robust (the box tends to crack when the bolts are tightened).

I've read Greg's comment on here that the stock Jensen airbox setup actually offers a small power advantage over K&Ns fitted directly to the carbs. While this sounds counterintuitive from a "free access to air" perspective, perhaps the fact that the stock setup draws slightly cooler air and then funnels it into the carbs actually leads to faster and denser airflow at the carbs compared to pancake filters. I suspect the exhaust system is also a factor - perhaps it makes relatively little difference what airbox setup you use with the stock exhaust system, as it is the latter which is the real constraint on airflow through the head?

In which case the replacement of the stock exhaust system with the LotusBits big bore system on my GT has in effect shifted the airflow constraint from the exhaust to the intake side of the head, which is why there was such a big dyno reading difference yesterday between the Jensen airbox setup and having no airbox at all?

This is all very interesting stuff, and has helped me to understand that engine tuning can sometimes be a bit of a black art!