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250 Posts
Discussion Starter #1
before further hijacking other folks threads clogging them with information, I'll open my own build thread.

Last year, I have started to build the motor for my 1999 S1 Elise.
Before deciding to go Honda, I was running a supercharged Rover K in my Elise for 12 years.
I build this Rover K myself over the years. In the end, it was changed cooled, forged pistons, steel rods, nodular iron liners, Newman ph2 cams, 4-2-1 header, 2.5" exhaust system, direct port water methanol injection.
I have always mapped it myself with the help of my ears, a J&S Safeguard knock control system and a STACK wideband lambda sensor. At some point it made more power on the road than what I can enjoy, was complex and I was missing a 6th gear.
So I decided to do what was overdue and convert to a K20.

Initially I planned for slapping on a JRSC, but for mainly the hazzle of getting it street legal, I skipped the SC part for now. Maybe later.

I bough a swap package from some chaps in Holland. They source theirs in the UK. After doing some leak down tests with numbers hitting 40%, they got me an other motor. This one was not much better.
This is when I decided to rebuild the engine. Unless you can drive the car with the K20 in there, better prepare for a rebuild. For some magic reason, all 2nd hand engines in Europe are below 100000km or 60000 miles :-((

When I disassembled the engine, the bearing shells were worn down to the copper layer, the oil channels of the shells hat molten metal stuck to them and the liners showed blank spots and excessive wear on the sides.

This is when I though about building a stroker.
I got a good price on a ZRP kit consisting of a 93mm crank and their associated rods of 135.5mm. If you want to find out, how a low rod to stroke ratio K will work, this is the opportunity.

As pistons I wanted Mahle Motorsport 87mm pistons with a 4cc dome volume.
All the shops I contacted canceled my order stating that Mahle canceled this particular piston. I had little choice but to go to Supertech as I wanted a piston in a 4032 alloy.

Pin weights deviated by up to 1.3g!!! 3 of them where within 0.8g of each other.
I took me hours to grind off material to end up with 4 perfectly matched sets.
Most weight got removed from the pins bore chamfer on both sides. A little also got removed from the pin bosses of the pistons.

Block was bored and honed with a torque plate. Final hone was a plate hone. It feels smooth sliding with a finger nail love the bores desire them looking matt.

Next was getting all the gauges and figuring out the bearing clearances.
Piston to bore was measured to about 80µm or about 3.1 thou.
Bores were pretty much round with the centres being about 20µm or 0.8 thou bigger. I was explained that he honed them to be round and that it required to take off a tad more on the middle. Better round with the tiny belly than square and perfectly cylindrical.

I found the main journals of the block being hour glass shaped.
In the end I got to the right clearances of about 40 to 45µm using three sizes of KingXP bearing shells.

I had to bend a new set of oil squirters to pass the rotational assembly. I JUST fits with about 30 thou clearance to rods and pistons.

more text and pictures later on.

5,718 Posts
Hi Mark, I appreciate your decision to document here about your very interesting engine project. I would love to read more about the build and its challenges like piston choose, bearing clearance matching, and so on.

I also would love to read about the engine swap challenges into that tiny chassis and the process of header and intake decision, the consideration you made and so on.

Also some videos of the chassis running on the track with the K engines, both the Rover and the Honda K-series engines: differences, specialities, ...

Anyway, I am looking forward to see and read more of it.


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250 Posts
Discussion Starter #4 (Edited)
a few pictures:

the car:

This is how bad the shells of the old engine looked like:

The OEM crank with overheated journals

Head back from the machine shop. 8 new exhaust valves. They are manufactured by the german OEM supplier TRW. TRW belongs to Elring. Got them through the engine builder.
Intakes were reground as well as all 16 valve seats.
Toda Single springs were installed.

Detailed view on one of the chambers:

View into the freshly honed cylinder:

The Supertech pistons. Before fitting, I machined a cutout into the wall of the valve pocket of the inlets, too. The wall is way too thin as is, about 1mm.
I dod not take a picture afterwards.

Getting an idea on the bearing clearances. KingXP std sizes to start with.

getting there with the good UK Plastigauge in the right range and resolution.

all set in the end using three sizes of KingXP bearings in combination.
This gets you a resolution of 12.5µm to set clearance. I got away with it.
the crank and the rods by ZRP had virtually no tolerances. I found all similar journals to be within 1-2µm of each other. This corresponds to the thermal expansion of a journal heating up by about 1°C!

Bending oil jets so they clear the rods and pistons:

I have chosen to install a facelift OEM EP3 flywheel plus a OEM Honda clutch. This should result in OEM drivability. :)

Got the valve cover chemically stripped and power coated.

Rods installed on pistons

and installed on crank.

250 Posts
Discussion Starter #5 (Edited)
oil pump fitted:

Pistons fitted in block. Cosworth 87mm head gasket. Standard thickness of about 0.8mm.

popped on the head to check if it fits :)

Ready to clay the motor. Reference pictures to be able to reassemble the rockers correctly. I blocked them by swapping around the pins.
I got a spare VTC gear to open and block with the socket.

Toda A3 cams, made in Japan.

After claying. There are about 3mm of clearance! I hope I got this one right as it seems a lot. Or those Supertech valve pockets are deep as advertised.

More assembly.
I have fitted a Fluidampr. The OEM unit was way to rusty to refit.

Slowly coming together:

I have set all the valve clearances according to the Toda spec sheet.

CPL Racing sump baffle

I also opened up the gearbox. Some of the synchros did not look good.

As I intended to go SC, I had the GB redone.
Wavetrac LSD, 3.9 final drive, shorter 4th to 6th from the JDM DC5R. I just hope 3rd does not feel to long. Otherwise, 1st should be a useful gear and 2nd is good for more than 60mph. 6th is overdrive for the highway. Remember, the car only weights some 1500 pounds. I have litte to no use of a short 1st gear. Watching a fair few track videos, most Elise folks hardly ever even use 2nd on track.

The conversion loom from the Elise loom to the Honda engine loom. I have build two of those. The first one is already tested and worked first time.
I'll wrap it in proper loom tape and pipes once it is tested.

The car before the engine installation. Heat insulation is self-adhesive Teknofibra 2mm.

To get you an idea on how tight space in a S1 Elise is:
Exhaust manifold primary pipes to intermediate shaft bearing. The heat shield, a modified OEM unit is not installed yet.

Corner of the gearbox has to be cut off to pass the subframe.

Rough idea on flexi and cat converter positioning:

250 Posts
Discussion Starter #6
why a ported RRC?
I am a constant car fiddler. Making is faster and more reliable is a constant urge.
As this distracts from actually driving the car, I decided to do a high spec build.
Mapping is also fairly tedious and expensive in Germany.
This led to the motto: do it once, do it right.

Pistons: Ideal Mahle Motorsport. As nobody could sell them to me, the Mahle website is or at least was a nightmare to navigate through, I gave up after a few weeks and went Supertech. I also considered Cosworth, but CPLRacing, the sole vendor advertising 87mm Cosworth pistons at the time, told me, he does not sell these (custom) pistons anymore.

Why 87mm? Well it is 1mm extra over the stock bore, so I even gain a few ccs and reduce valve shrouding.
Folks have run 87mm on the stock bore and had no issues.
If I need a rebore, I'll have the block sleeved and go for 88,5 or 89mm :))

Why ZRP? It was a very decent offer at the time compared to BCs offerings.
In the end, both are chinese cranks. BC offers a slighly better rod to stroke ratio having 1mm less stroke and 3mm lower deck height pistons.

Why RRC? It is considered the best performing OEM intake.
Why ported? User deibral had good results on a higher powered engine with the porting with gains across the rev band. As a well cam'd stroker has fairly high intake flow demands, I'd thought it might not hurt.

Why not a 2nd harmonic intake?
There was non of Joe's 8.5 intakes on the market and the only other system on the horizon is still in the making. Depending on results, I might still consider swapping.
As I have relocated the fire wall by a few cm and made the cover removable, I should be able to fit it.

Why a S1 Elise? I own the car since 2004.

Why 12:1 compression ratio? I would have also been OK with anything from 11:1 to 12.5:1. It was more dictated by the piston choice.
Full custom CP pistons would have cost about twice that of the supertech pistons and would have been made from 2618 alloy.I prefer the low CTE 4032 type of alloys.

The fuel pump is a OEM compatible unit by Spitfire engineering.
The fuel system is a return system regulated by a Webcon 3.5bar fixed fuel pressure regulator.

ECU is a Doctronic ProECU-K. It is a Honda PRA ECU converted to run custom software on its CPU. Features are very similar to a KPro.

5,718 Posts
Thanks for sharing your pictures and experience, Mark :up:

...After claying. There are about 3mm of clearance! I hope I got this one right as it seems a lot. Or those Supertech valve pockets are deep as advertised.
Did you clay the squish height too? I just can't see on graving or marker at the exhaust valve reliefs, which overlays with squish area too.

5,718 Posts
...I am a constant car fiddler. Making is faster and more reliable is a constant urge.
I like your enthusiastic allure. My enthusiasm cost me 1000's of Euros, but I see room for improvement over the RRC and the available aftermarket stuff. My developed Dampfhammer IM is getting tested before June 2018. Maybe you find the time and room to test it this year too if you have interest?!

...Pistons: Ideal Mahle Motorsport.
Beside the silicon content or the related thermal expansion aspect of the piston material there are TODA, Wössner and CP Carrilo have pretty nice pistons. Wössner and CP do customized pistons too. Would this have been an option for you?

...Why 87mm? Well it is 1mm extra over the stock bore, so I even gain a few ccs and reduce valve shrouding.
90x78.5 engine for the 2000 ccm racing market :D. Yes shrouding is an issue with the 86 mm bore, which is reduced by increasing the bore. Larry from ENDYNE is one of the few who understand and solved that issue by his welded chamber and reshape approach. The smaller angle and longer outlet distance helps to increase flow by reducing shrouding among other flow regime related effects.

...Why not a 2nd harmonic intake?...
Yes, why not :wink:?! Joe's approach was good and for some cases got verificated to improve VE over more free designable ITB's. Joe designed both, his header and IM mainly for peak power. Not only few of direct comparisons show the disadvantages of that approach. Peak power was good, but below that is lost VE support compared to ITB's support of that.

I learned a lot out of that and integrated this into my Dampfhammer intake manifold development. I focused on high leveled VE bandwidth and on cylinder VE balancing. For that purpose I integrated two innovations, beside harmonizing all alternation of load parts for my project aim (16+ bar of BMEP from 4.5-8.5 krpm).

It would be pretty cool to see how it do it's job on a bigger displacement engine, which has not harmonized parts and higher port velocities at lower engine speed. As this distorts it's approaches to be optimal. The offset of that would be really interesting to see.

...The fuel system is a return system regulated by a Webcon 3.5bar fixed fuel pressure regulator.
Is it a -6AN piping inclusive return line? With my setup this results in a heat flux of up to 600 W into the tank, which could be lowered by 50-60 % when choosing the short return line at pressure regulator instead of take a return after injector manifold. I am still not sure what is better, as the effect of air cooling at intake conquers with the vaporization time. The first increase VE and lowers mixture homogenization, the second lowers VE and improves mixture homogenization. I was more for the first, I assume it has more effect on torque as the 2nd. Any thoughts, calculation or experience on that?

250 Posts
Discussion Starter #9 (Edited)
the two flat faces of the piston are exactly at the level of the cylinder faces.
Static squish height is therefore equal to the compressed head gasket thickness of about 0.8mm.

I use AN6 lines to and from the fuel rail.
The fuel pump is pretty efficient. I don't expect more than 70-80W being transferred into the fuel.
I never had fuel heat issues despite running two fuel pumps before.
Where should these 600W come from? Heat transfer through the rubber line is not that efficient.

Regarding evaporation. The fuel is injected in the stock location. VE increases from evaporative cooling only occurs if evaporation actually happens in air. If any evaporation happens at the walls, the walls are cooled down, but not the gas. This is a major issue in many implementations of methanol water injection. Folks cool lots of piping, but little gas.
You can calculate that if most evaporation happens at the wall, you'll lose up to 3% charge density due to the vapour volume generated and its associated drop in oxygen partial pressure. This is why the fuel has to evaporate in air and not at the wall. Cool walls are not interesting.
This is why I believe that unless you run very high boost pressures or a compressor well outside of its efficient area, anything but direct port injection at the right location makes sense. Most plenum designs these days are optimised for dry flow. How folks can assume it works well for water methanol is beyond me.
I did calculations of g-forces of matter taking a bend in a intake plenum you can see numbers of 10000g and higher. This is well into the territory of natural gas dryers used in the oil and gas industry. They centrifuge the water out of the gas at similar acceleration figures.
Before doing it properly, you could even see where the water run across my pistons on my old engine with litte effect. It just blew it out of the piston.
This is why many in the US have so much better results with injecting pure methanol. It works even as a pissing stream and poorly distributed across the cylinders. Water unfortunately not.

Compared to the enthaphy of evaporation, the heat of capacity of fuel is comparatively low. Preheating fuel makes litte sense in respect to fuel mix homogeneity. With proper injector location, todays fuels, swirl and 4 valve heads, this is not a critical issue. You would rather cool it. Best would be to make sure it is not much warmer than ambient.

You can gain Ve by having the fuel evaporate while traveling down the runner, but you need to be careful doing so.
Some race series inject the fuel as a solid stream right against a intake valve. it only disperses and evaporates within the cylinder.
If you use very high flow injectors, you can time this "direct" injection to only happen with the valve open to take advance of evaporative cooling within the cylinder increasing charge density.

I had Wössner pistons in the Rover. They also had valve pockets with thin walls. Mine would have failed without the direct port methanol water injection. The crown walls at the pockets were already bend.
Wössner is shipping pistons with flawed designs.

Mahle was my favorite. I also considered Wiseco and CP.

In the world of ITBs, unequal runner lengths were successfully implemented on Rover Ks spreading the torque.

I'd personally drive development of a switchable set-up If I would have the time or skills. Ideas, plenty. Time, no.

I am still interested in the 2nd harmonic stuff. Activation energy will increase once my engine is mapped and running fine though.

The overproportional gains by bore increases due to valve shrouding effects have been recognized in the Rover K world for a long time. Folks like Dave Andrews and Roger Fabry rework the heads also regarding these issues.

5,718 Posts
the two flat faces of the piston are exactly at the level of the cylinder faces.
Deck height = 0 :up:

...Wössner is shipping pistons with flawed designs.
Which design is failure free? Only those you did yourself :D. The Mahle piston is a bit far from optimum. Their coating is not the latest technology, the edges are not heat spot reduced shaped, the valve reliefs are not parallel to valve surface, ...the green grass of the neighborhood looks always more green then the own one.

...In the world of ITBs, unequal runner lengths were successfully implemented on Rover Ks spreading the torque.
Nice approach :up:. As the inline 4 engine isn't free of free oscillating forces concerning balancing, I wouldn't do it. V8 guys use that since the early 50'ies.

...I'd personally drive development of a switchable set-up If I would have the time or skills. Ideas, plenty. Time, no.
There are disadvantages in doing switchable designs, e.g. cost, control, reliability and sealing. You can do one Diploma Thesis out of that, this is a lot of effort for an questionable win, as the development risk is high. Within a F20C-engine development I would do it, but not for the K20A2 with the VTC, the win in VE is much lower.

...I am still interested in the 2nd harmonic stuff. Activation energy will increase once my engine is mapped and running fine though.
Spring time?

...Folks like Dave Andrews and Roger Fabry rework the heads also regarding these issues.
Thanks for your hint :up:

250 Posts
Discussion Starter #13
The lessons learned from having a closed look at pistons in the past is plainly dremel off the excess metal on the edge of the valve pockets.

250 Posts
Discussion Starter #18
You could also convert to a Toyota gear shifter and just use the alitech rear brackets

250 Posts
Discussion Starter #19 (Edited)
A litte progress since the last post.

Installed the water lines for the radiator and the cabin heater.

Swivel neck thermostat housing to clear the laminova il water heat exchanger.
The engine is fed the cooling water from the radiator return coming from the bottom. The pipe is a black 32mm silicone pipe. you can see it sitting against the silver heat insulation.

RRC intake manifold fitted.

Throttle body to air filter piping added.
I use a ITG maxogen carbon fibre airbox with an ITG foam filter rated for 300HP. It has a 80mm exit pipe. I don't like the fuel return line routing. I'll add two 90 deg beds to make it nice and straight.

Valve cover vent installed.

Some cable ring terminals and crimp tool to hook up the main battery feed.

Fuse box with M8 terminals and 100A rated strip fuse.

Fuel lines and filter are also fitted. I'll have to refine the routing on two places next week.
With a little luck I might be able to fire it up next week for a initial trial.
If it all works, I need to wrap the conversion loom.
Next, I have to assemble the drive shafts, mount the rear shocks and the exhaust system.
For the first firing up, I'll just run it with the header minus the 4-1 collector, so a 4 in 4 exhaust system :))
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