QUESTION
Thanks for inspecting the Nikasil coated liners from my Lotus Esprit SE.
I can't say that I am surprised by your comments.
What's involved with refurbishing the liners?
What is required to get that underway?
C.H. - Sydney, NSW
ANSWER
A quick summary regarding your liners
They exhibit a typical wear pattern when the piston rings are in constant contact with the Nikasil bores
1) The bores have a slight taper
2) The bores are slightly oval
3) The bores have several wear steps
4) The bores have vertical scratch marks that cannot be removed by conventional methods
Lotus Esprit worn Nikasil liner
The largest wear step is approximately 10mm down from the top of the liner
This step presents a problem when anticipating just fitting new piston rings
The Nikasil coating is so hard the step cannot be removed by conventional machining methods
If you were to fit new rings then the top ring would suffer mechanical damage when encountering the step
The only way to overcome the step is to fit stepped rings
Unfortunately stepped rings would have to be specially made for the Mahle/Lotus pistons - have been down this track many years ago
From the wear measurements taken in the bores suggests new piston rings would have a very difficult time bedding into the existing wear pattern
If the new piston rings fail to bed in, your engine will have excessive blow-by (plus excessive crank-case pressure) and lack power
In an ideal bore, there should be no taper, no ovality and no steps
Lotus Esprit replated Nikasil liner
In addition to this, the Nikasil coating is just in the process of breaking through to the aluminium liner material
Look closely at the wear marks approximately 15mm down the bore and you can see a grey band that traverses 30 degrees or more
This wear band indicates the liners should be re-plated
Before the liners can be re-plated, it is necessary to determine -
1) if the existing pistons and ring lands are worn
2) if new rings are available for the existing pistons
Can you please measure the ring lands and compare the measurements against what is in the workshop manual
In the event the existing pistons cannot be returned to service, then Lotus Marques can supply new forged pistons
Below is a photograph of new pistons and re-plated liners supplied to one of our long time Lotus Esprit customers
Lotus Esprit pistons and liners
Copyright © 2014 Lotus Marques
Thanks for inspecting the Nikasil coated liners from my Lotus Esprit SE.
I can't say that I am surprised by your comments.
What's involved with refurbishing the liners?
What is required to get that underway?
C.H. - Sydney, NSW
ANSWER
A quick summary regarding your liners
They exhibit a typical wear pattern when the piston rings are in constant contact with the Nikasil bores
1) The bores have a slight taper
2) The bores are slightly oval
3) The bores have several wear steps
4) The bores have vertical scratch marks that cannot be removed by conventional methods
Lotus Esprit worn Nikasil linerThe largest wear step is approximately 10mm down from the top of the liner
This step presents a problem when anticipating just fitting new piston rings
The Nikasil coating is so hard the step cannot be removed by conventional machining methods
If you were to fit new rings then the top ring would suffer mechanical damage when encountering the step
The only way to overcome the step is to fit stepped rings
Unfortunately stepped rings would have to be specially made for the Mahle/Lotus pistons - have been down this track many years ago
From the wear measurements taken in the bores suggests new piston rings would have a very difficult time bedding into the existing wear pattern
If the new piston rings fail to bed in, your engine will have excessive blow-by (plus excessive crank-case pressure) and lack power
In an ideal bore, there should be no taper, no ovality and no steps
Lotus Esprit replated Nikasil linerIn addition to this, the Nikasil coating is just in the process of breaking through to the aluminium liner material
Look closely at the wear marks approximately 15mm down the bore and you can see a grey band that traverses 30 degrees or more
This wear band indicates the liners should be re-plated
Before the liners can be re-plated, it is necessary to determine -
1) if the existing pistons and ring lands are worn
2) if new rings are available for the existing pistons
Can you please measure the ring lands and compare the measurements against what is in the workshop manual
In the event the existing pistons cannot be returned to service, then Lotus Marques can supply new forged pistons
Below is a photograph of new pistons and re-plated liners supplied to one of our long time Lotus Esprit customers
Lotus Esprit pistons and linersCopyright © 2014 Lotus Marques