1997 Lotus Elise S1 - The quest for 125bhp per L (NA)

Small update that has been a long time coming.

The guys at Simpson Race Exhausts have been busy making a full new exhaust system for me



They have done a beautiful job



with not a lot of space to spare



Two big reasons for doing this, the first is to get cat installed again and the second is to refit the boot.

before



after



Starting to look like a science experiment.....

Ha!

Looks like you're at Ash's place where my son's Elan was built

www.asheritage.com/

Monday saw me back out on track for the first time since the car was put back together.

Despite seeing inlet temps of 50C(!) everything has held together.

Need to have a serious think about engine bay temps as the body was getting hot to the touch.

Here's a short video for now with a more considered post to follow

The ceramic coating is an option, it should reduce surface temps by about 30%

However this stuff reduces by >70%



Available from Thermomet

Brilliant cars, I’ve never owned one but I’ve been in a few including at trackdays and drove one with the original k-series engine at a trackday some time ago.

The most bonkers one I had a ride in had an Audi TT engine in it, guy said it had about 400bhp!

Following with interest- the building up of the virtual model in CAD via photos isn’t something I’ve ever seen before.

Cheers

Not as yet, I've been on honeymoon which has taken time and money from car projects at the moment.

Next step is to get a proper map on it and back to back the 3d printing vs stock manifold.

However, I need to get the wideband moved as its currently after the cat rather than before, then I need to wire that and the egts into the can on hondata (fingers crossed) then we'll be making progress again

Also found my speed sensor has been wired up with 10v rather than 5v which is why it's not working.

Ouch nearly a year since the last update!

Over the course of last year the oil useage continued to increase to the point I started buying oil in 20L containers..

Having had several reputable garages look at it including borscopes, leak down tests, compression tests and even engine removal and reinstall to find/resolve any leaks, nobody had found anything that would really explain the oil use.

At this point I collected a cheap run about and decided that if the engine was going to be rebuilt then it should be a bit special.

I have always been a subscriber of power:weight being more important that overall power, but having driven the lotus for a while now with ~300bhp/t from only 230bhp, I have begun to see the limitations of power:weight. The lotus is pretty quick to about 100mph, but after that its as fast/slow as any other 230bhp car because power:drag becomes much more important.

In summary I wanted more power to keep modern cars honest.

The easiest route to power would be to build for boost and put a turbo on but airflow for charge cooling is quite tricky, especially enough to deal with a 20 minute track session. Possible yes, but complication. I've got the Ginetta to mess around with silly power turbos so decided against that for now.

Supercharger is a well trodden path, but nearly all of the lotus installations have inlet air temp problems on track.

I have always seen the S1 as the "best" elise and the Honda Vtec as the "best" na engines, so what would be the best K20?

After a bit of research I collected a K24 block



with a .5mm overbore (87.5mm)



a standard k24 crank



and less than <1000mile used pistons and rods



Which I cleaned up a little bit and they looked okay to me



I also collected a new K20 head from an FN2 (making this a RSP head)



This one hasn't had any machine work done to it...yet



I'm not an expert but ports look pretty good to me from the factory



The camshafts are being made up by Toda which are still 4-6 weeks away.

However the goal is for a 2.4L K20/24 frank running 300 naturally aspirated ponies at 8krpm.

While its only another 70bhp peak, the torque at 3krpm will be higher than the K20 makes at any point in its rev range, and it only goes up from there.

So a lot more power, everywhere, a similar rev range and no worries about Inlet air temp or the extra weight of turbos, intercoolers, etc.

Thats the plan, but its quite a big ask so we shall see how close we manage to get!

The port that Honda was using on non performance engines 35 years ago - this one feeding 450cc





And after cleaning it up





And the chamber





Strangled back to deliver a mere 66 BHP/litre


The bore on this engine - 87mm !

I see you and I raise you:









Quite interesting to see the differences, i'm going to be running a lot more stroke (99mm) and the valve sizes are somewhat different! But then I am going for 75bhp per cylinder