Paul's 918 V8 Rebuild

[97-Esprit V8]

My engine let go on the race track at the end of the summer in 2008, car has been sitting waiting for me to have a chance to focus on the rebuild.

When the engine let go I heard a odd sound of which I thought was something going through the engine that wasn't very compressible...

When I did a compression check one of the cylinders was reading zero, so I began to look at what the causes could have been. I took a look at the turbocharge on the opposite bank and found that it was missing some of the compressors fins. I've been told that something must have gone through the the compressor but I can't see how that would be possible with a K&N airfilter which is completely undamaged up front. I believe the turbocharger compressor fatigued and the blades started to chip off until it failed more dramatically.

I pulled the engine and today finished stripping it down to just the crankshaft remaining. The pistons all look fine with the exception of the one in the zero compression hole...the cylinder is fine as well, amazingly enough.

So for the rebuild plans, I will be installing a set of JE forged pistons, and having the crank/rods/pistons rebalanced for the lighter rotating mass.

The turbochargers are being reflowed with T28 wheels and machining to the factory housings to match. I will be port matching the exhaust manifolds to the head and turbine housing and then ceramic coating the manifolds and turbo turbine housing. The cylinder heads will be ported as well as a 5 angle valve job completed.

Along with the JE pistons I will be upgrading the factory head bolts to a proper head stud and nut arrangement from ARP.

I'll take some more pictures of the parts as I go on the rebuild. Hope to have it completed by the end of February 2010.

Further plans are to install a custom water to air intercooler system, retube the water/meth injection lines with a braided steel lines. I will also be addressing the fun policing factory ECU with a piggy back engine management system. This will do a number of things, allow me to get rid of the factory secondary injectors and to replace the factory injectors with some higher flowing units. It will also allow me to clamp the factory MAP sensor to a very low pressure and use the piggy pack to manage the fuel and timing under boost conditions thus reducing the interference of the factory ECU in timing retarding and fuel enrichment. It will also allow me to run much more aggressive timing and fuel when using water/meth injection, I will be able to run dual maps which will automatically detect when the water/meth is working and adjust the maps accordingly. All while maintaining the factory startup, cruise and day to day driving tuning of the well sorted factory ECU.

Hope everyone had a good holiday season, more to follow.

[mike_sekinger]

Hi Paul,

Great to see the thread surface for your engine rebuild.

By the looks of it, you have A-grade piston/liners installed, so you need to put some more clearance into the liners for the JE pistons.

Very interested to see how the piggy-back works out.

Keep the updates coming !

Cheers,

Mike S

[97-Esprit V8]

Finished pulling the bottom end apart, here are some pictures:

Intermediate shaft drive chain with guides, front cover still in place.

Cross hatching still visible, all in all very clean engine with little sign of wear

Front cover, water pump still installed(top), roller bearing intermediate shaft bearing(middle) and oil pump(bottom)

Crankshaft just before removal

Main bearing top shell, perfect shape

All main bearings in great shape and will be reused

Cylinder head ready for strip down

Should have the cylinder heads stripped this evening, eager to see the valve seat and pocket area. From the intake side there is much room for improvement with porting.

[97-Esprit V8]

Checking a valve for straightness

Exhaust manifold port, notice the lack of overhang of the manifold past the gasket opening.

Exhaust port on cylinder head, notice the overhang past the gasket opening. This will be 'ported' to match the exhaust.

Here is a look from the intake runner to the valve seat area. Notice the overhang, doesn't look like much but it is.

Here is the top side of that intake runner, same sort of overhang. This will all be port matched.

Combustion chamber looking to the intake runner, notice the fuel injector and it's 'pocket'

Exhaust port with back light

After pulling the valves out, I am more happy with the intake seat and pocket areas. But I will still clean them up. The exhaust side, not so much. Going to take a bit more work.

Anyone know the stock combustion chamber volume or the dish volume on the pistons?

[mike_sekinger]

Hi John,

Making good progress. The combustion chamber volume is 37cm3 with a 8.0:1 compression ratio.

I

[97-Esprit V8]

Hi John,

Making good progress. The combustion chamber volume is 37cm3 with a 8.0:1 compression ratio.

I

[97-Esprit V8]

Some more updates, been working away and not posting much. Mostly finished porting on one of the cylinder heads. Pushing 8 hours so far, I'll post up some pictures once it's cleaned up.

Here are some picture of my new JE pistons from JAE. I opted for 9.0:1 Static Compression Ratio pistons and they happily made me some up.

New pistons are 4.4 grams heavier, but their pins are 1.5 grams lighter. So I have a bit of balancing to do to bring them back to factory weight.

Just need to get the block off to the machine shop to get the pistons fitted so I can begin the reassembly.

[mike_sekinger]

Hi Paul,

Good to see some progress. Will be very interesting to see how the higher-compression works in practice. I notice that you didn´t go with the optional JAE crown or skirt coatings. Was this a conscious decision on your part?

It will be nice to see the head work. It is acknowledged to be a great time consumer, for not a huge return. Information coming with the pairs that I have had, at best indicated between 10-15% flow improvement on the bench.

Looking forward to seeing it come back together again.

Cheers,

Mike S

[97-Esprit V8]

Yes I didn't feel the coatings would be worth the extra expense personally.

I've never had a head flow benched as I feel it's not a representation of actual conditions. Making improvements to flow based on a bench doesn't make much sense. The majority of improvement comes from the valve job and port pocket area, having those done by someone with the correct equipment and experience is key. I try to avoid major opening up on the intake side and focus most of the work in the exhaust port. I agree lots of effort for minimal gains, but they all add up.

A bit more compression, bit better flow and larger capacity modern turbochargers, free flowing exhaust system with race cats. I'm pretty confident that this setup will make north of 500rwhp quite easily. I'll be much more interested in doing that with the minimal amount of boost pressure.

Paul

[97-Esprit V8]

Went to the turbo shop today as my GT25 turbocharger ball bearing cartridge finally arrived. After looking it over we determined we can make it work. Should be a nice improvement with a higher capacity modern design. Each turbo should be good to 330hp or so, with as good or better response then stock. Sorry no pictures, didn't have my camera.

[97-Esprit V8]

Intake port ported

Exhaust port ported - large increase through to manifold

Combustion chamber view

Hard to tell from the photos really, mostly just cleaned up the obvious areas - around the exhaust valve guide being a major one. Transitions from the machined valve seat area to the port and the actual valve seat. Most of the work was done in the exhaust port to improve the flow ratio. With the larger turbocharger, increased flow requirements will show some good gains. Once the engine is finished and broken in I will do some dyno testing to see the results.

[JeepinMatt]

Stupid question, but what's it cost for a typical rebuild on the V8 itself? Excluding the turbos and such. I don't own one, but I've been trying to get a grasp on prices for V8 parts and I'm wondering if they're, on the whole, simply expensive or arm-and-a-leg expensive.

[mike_sekinger]

Hi Matt,

The costs of a rebuild will vary hugely on what needs to be replaced. From memory the standard rebuild job is listed at around 60hrs labour to extract, rebuild and re-install the engine. So unless you´re doing the job yourself, there is a fair amount of wedge already accounted for.

Part wise, if it is purely an overhaul type of affair, then the top- and bottom-end kits aren´t too crazy, but the head gaskets are quite expensive (approx 140GBP each).

If you´re looking at damage to the crank, pistons/liners, or even head damage, then the costs will obvioulsy start to go up dramatically.

Budget-wise I would estimate anything from 4-10KGBP

I understand that Lotus do have some repaired engines available, which in some cases could make greater financial sense. The supplies are rather limited, but the cost of one of those was 6KGBP +VAT.

Cheers,

Mike S

[97-Esprit V8]

Well long time no update...

New turbos are finally done, here's some pictures. Hard to see much difference, the CHRA's are GT2560RS ball bearing units, the compressor housing needed to be machined to fit the larger wheels and the turbine housing needed major work to fit the CHRA.

Still waiting on my new pistons...ones I got were standard size after being told they never needed to be larger...I now have 10 overs coming and the high compression units might just end up in a really cool engine build

Paul

Edited May 10, 2010 by 97-Esprit V8

[Che]

Using Ball bearing turbo in Esprit is nice but be aware you might need an oil restrictor.

The journal type don't need a oil restrictor and proven to work in lotus esprit twin turbo. Ballbearing does need a restrictor. If your

engine start smoking chances are the turbo is overwhelmed with oil. It will zip or blow out to the turbo piston ring & goes out to the

exhaust downpipe. At the same token, If you don't know the size of the restrictor, you might end up starving the turbo and crap out too. The hardest part is figuring the size of the restrictor. Just an advice.

[Tony94S4]

^

.035"

On all BB unit's gt35 and smaller,

Paul,

R u using gt2560r or 2860rs cartrige?

lookin good bud

Edited May 24, 2010 by Tony94S4

[97-Esprit V8]

turbo has a built in oil restricter in the CHRA

I believe it's a GT2560R cartridge

Edited May 26, 2010 by 97-Esprit V8