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

[mrluke]

Jun 19, 2021 9:54:31 GMT gtviva said:

Amazing work on the 3d printed stuff! the brother in law has an Elise and a 340R which bits seem to fall off or break on a regular basis!

On another note any more info on the Firenza?

My experience with Lotus is they like to be used and quickly fall apart when they aren't! FWIW i've also made replacement rear light pods for the 340r

Sorry no more info on the Firenza, I wish that was my garage but the car was actually at Automotive Sporting Heritage who were doing the work to it facebook page below. They always have some interesting toys there.

www.facebook.com/Automotive-Sporting-Heritage-191830454212646

[mrluke]

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.....

[Carsie]

Apr 9, 2021 10:34:21 GMT tom13 said:

Such a good looking little car. Love how you use it as it was intended.

Seconded!

As an Elan S3 owner (now delegated to Son No1 ) I totally agree. A Lotus, in my eyes, is about engineering and being driven. Really like the Cadwell track video; nice smooth steering inputs and neat gear changes. - I like!

[Carsie]

Apr 25, 2021 21:39:54 GMT mrluke said:

Well err that escalated quickly



Few bits and pieces need tidying up, oil lines, coolant lines and and the like. Then I accidentally bought a lightweight flywheel and here we are.

Apr 14, 2021 19:28:08 GMT jim said:

Love it! I'd be interested in hearing about the photogrametry

Basically you take a lot of photos and try to cover every single angle of the part. Then you run that through some clever software and it stitches it all together to produce a model.

The model is pretty good, dimensionally it is within fractions of a mm. However there are often areas where it hasnt quite understood the photos and it has holes in or is distorted. I've gone through a number of refinements to get to a pretty small error margin now

I use this "scan" as a reference and create my own mesh that is easier to manipulate.

Ha!

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

www.asheritage.com/

[xfu990]

"They have done a beautiful job"

You're not kidding they have, top marks! I can look at that all day

[mrluke]

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

[alx]

Would ceramic coating the exhaust help reduce heat soak?

Mate of mine does this and it looks the business.

[mrluke]

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

However this stuff reduces by >70%



Available from Thermomet

[alx]

Can you mount some fans underneath the deck lid to extract some heat too?

Someone seems to have done it on their esprit

link

AL.

[bugjam1999]

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

[thebaron]

Any updates on this?

[mrluke]

Jan 25, 2022 17:10:41 GMT thebaron said:

Any updates on this?

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.

[mrluke]

Not forgotten!

Here's a few images from Cadwell yesterday, love the photos you get from opentrack.

One wheel off, just!








I'll make some actual progress on it soon... promise!

[mrluke]

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!

[thebaron]

How's this coming along? As I've been sampling other cars over the past while that are classified as top of the sport car genre I've almost reached the point where I call it a day and have this Lotus Chassis as my favourite.

I'm going to drive a couple of Caterhams next month as I've never driven one and I need to make sure that I'm not missing something even more suited to me.

If the Caterhams don't sway me then it's time to really plan where I want to take the Speedster long term. I really enjoy this build of yours as it's exactly the place I would go if not limited by the Swiss MFK.

[Darkspeed]

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 !

[mrluke]

Progress has been a little slow lately but the updates on here have been even slower!

Lots to catch you up on over the weekend, i'll get some pictures added.

If you have a long memory you'll know the car was parked up over the winter due to excessive oil useage. I've finally gotten around to change the valve stem oil seals which are pretty much the last culprit.



The picture above shows me part way through, i'm working on cylinder 2 exhaust valves (having started at 4 and worked along). I was using an airline fixed to the spark plug holes to keep the valves up but the airline connection came apart at this moment and I lost a valve into cylinder 2.

That was enough for one day.

After sleeping on it I hatched a plan.

The valve stems are ~5mm diameter so I purchased a 4mm diameter magnet on a flexible stick. Armed with a selection of magnets, pliers/forceps/long tweezers and the like I returned.

The magnet was threaded through the valve guide and managed to connect with the valve stem. It was strong enough to lift the valve but as the guide was at an angle the valve would fall when it reached it.



I removed the exhaust manifold for access, lifted the valve up to the guide with the magnet then grabbed the stem with long tweezers, then with a bit of wiggling / pulling I was able to guide the valve back up the guide, success!

The reason for all of this faff is that to remove the head I need to remove the timing cover. The timing cover is too close to the chassis on the elise so I cant remove all of the bolts. This makes it an engine out job to remove the timing cover.

This is also the reason why cylinder 2 wasn't at TDC. I removed the cams with 1 & 4 at TDC then held the chain with a bungee to keep tension on it. I couldnt turn the crank without making this into an engine out job.

Now for something a bit less typical for RR...

I've got most of the parts here now for my new engine so I have started scanning them...

K20 Sump


Vapour Blasted K24 Block


K20z4 head, its been worked on and was too clean for a nice scan :/


K20 valve cover


All together with an rsp manifold

[mrluke]

Mar 28, 2023 6:38:41 GMT Darkspeed said:

And after cleaning it up

I see you and I raise you:

And the chamber

Strangled back to deliver a mere 66 BHP/litre


The bore on this engine - 87mm !

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

[Darkspeed]

Very nice - 300BHP N/A - I have one of those that I am well overdue building - same number of valves as well but only 40BHP per cylinder....

[mrluke]

We welcomed our first child at the end of August so everything else has been on hold for a few months now.

I've put the lotus engine back together but found it very stiff to turnover. So I took it apart and double checked everything, reassembled and still the same.

Happy I hadn't done anything wrong I tried to start the car and the starter really struggled.

On inspection turns out the alternator has seized solid and when the engine turns it drags the belt round the pulley.

To test I went to remove the aux belt and found the tensioner was also solid, even with a breaker bar I couldn't get it to budge.

I removed bolts from the tensioner until I could rotate it enough to get the belt off. Once off the engine turner over freely, success.

Finally got the alternator out and its seen better days..although didnt notice any problems with it before I parked it up.



Bought replacement tensioner and alternator.

Alternator is from wosp and comes with 20mm spacers for the bottom bolts but doesn't come with extended bolts so I cant install it.

Hopefully once I get the new bolts ordered up it can finally go back together.

I also installed the FN2 cams from the new head so that should give a small bump in power.