Citroen C1, Peugeot 107, 108 & Toyota Aygo Owners Club. (Discount code for CityBugStore: C1OC)

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PostPosted: Sun Nov 17, 2019 3:17 am 
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I went back and did a bit more work to the runners where I started. I should have spent more time here on the first pass - couldn't leave it unfinished!

It's looking pretty monstrous just from deburring and blending the transitions; I've kept the original angles & port diameter in tact and I wouldn't want to remove any more material even if I could.
All that's left is to check the ports align properly with the head.

This is it for the induction system now, I need to stop procrastinating and get on with rebuilding the cylinder head.

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Inlet Manifold 2.jpg
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PostPosted: Tue Nov 19, 2019 6:54 pm 
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Finally!

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I'll be commandeering the kitchen for this part.

Before I clean the cylinder head I'm removing the valves and any bits still attached.
I've recruited this lasagna tray to keep things organised..

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Valves.jpg
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Interestingly the valve stems all measured around 4.92mm diameter.
The manual has these listed as 3.90mm - 4.50mm.

It could be an oversight but then this engine is the 2012-updated Euro 5 spec and these might have been revised during production. I haven't heard of bent valves but I imagine the larger diameter stems will reduce wear to their guides under side loading - This '12 107 does a lot less cold-start tapping at 115k than my '06 107 did and I wonder if that had anything to do with worn valve stems rattling about.
-More investigation required I'd say.


The head casting is nice and the inlet ports are well formed with a few pockets machined to improve flow.
I've spent a lot of time staring at it, trying to work out what the airflow is doing and how it could be improved but we'll have a better look when it's cleaned up.

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PostPosted: Wed Nov 20, 2019 5:23 am 
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I gave the head a hot soapy bath and a good seeing to with a toothbrush.

After a while I was just pushing the grease around so I pulled it out and rubbed it down with kitchen roll. It cleaned up alright - Good enough to work with anyway - I'll be saving the tin of engine degreaser for later.

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PostPosted: Wed Nov 20, 2019 8:37 pm 
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So here's whats happening in the cylinder head..

I wasn't going to review the porting process at first but it's become quite a big part of this rebuild so I think it has earned it's place here.

I hope it's not too heavy.

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Port Form.jpg
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As I mentioned already, the ports are very well formed. The casting is properly aligned and there's a lot going on to shape the airflow through the combustion chamber.


The key to successful head porting, at least the kitchen workshop kind, is NOT to remove material to make the ports bigger. That would be bad. You need the air to accellerate past the valve with lots of energy so that the mixture is well distributed and continues to fill the combustion chamber after bottom dead centre, avoiding something called 'reversion' at lower rpm's where the rising cylinder pushes the air fuel mix back into the port before the valve closes - This is also why the inlet manifold runners to the port are slightly smaller than the port itself, to create a high pressure area acting on any air trying to revert back up the intake ports.
This isn't such an issue on peaky top-end-hp engine builds because they have the airflow momentum in their usable powerband such that this doesn't occur. This 1KR-FE however, at least how I'm building it, is not such an engine.
I'm driving for an increase in upper mid-range torque which should also see a small improvement at the top end.

All i'm doing here, like the inlet manifold, is working within the design intent and trying to bring what's there up to a level that's not economically attainable by the manufacturer during production.

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1) You can see this 'V' channel in the short radius of the ports; they begin an inch or so back up the port near the leading edge of the central divider and gradually open out toward the seat.
This kind of threw me off at first. Usually the inlet ports start high and have a relaxed short radius to keep the air attached around the short side of the valve seat. This seemed just the opposite.
Adopting a different philosophy: Considering the compact design of the engine and it's shallow port angle as a result, I think these channels are there to create an area of low pressure which pulls the air above it down at the valve seat and helps to turn it around the short radius into the combustion chamber that way.

I won't be blending the angular walls which form the side of this V into the port at all - if that were better then Toyota would have tooled this channel in with a round bit instead of casting it in as they have.
What I will do is try to smooth the rough edges caused by machining at the opening of the channel into the short valve seat radius with an additional angle, just using a light touch, that'll help the air stay attached around the radius without being so extreme that it destroys the port flow if my theory is off.

2) You might notice to either side of this channel the machined angle to the seat forms grooves which, when viewed together, toe in toward the centre of the combustion chamber as shown by the blue lines. The outside of the valves are partly shrouded by the combustion chamber's quench area and cylinder wall - These grooves will act to encourage the air to turn into the middle of the chamber, away from that shrouded area, promoting flow & mixture distribution in the process. These are therefore integral to how the air flows efficiently through the engine and I'll want to be mindful of this when I'm smoothing the transitions.

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Cast Flashes.jpg
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There are casting flashes which run the length of the port and they culminate in a very rough edge right at the critical section before the valve seat. These are just a by-product of the manufacturing process and removing them is always a good thing: reducing turbulence, improving consistency between ports and slightly increasing port volume up to the original design spec. Likewise I will be blending the small ridge around the seat itself where the port bore doesn't quite match the bore of the seat.

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PostPosted: Wed Nov 20, 2019 11:06 pm 
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Whilst you're wrapping your brain around all that nonsense I just want to cast back to what I was saying about the valve stem diameters and the reason I decided to undergo this rebuild in the first place.

After examining the valves during disassembly I realised it wasn't the exhaust valves that were leaking after all, it was the inlet valves.

I just compared the oil seals I removed from the engine to the new ones that came with the FAI gasket set and got a bit of a shock.

They're not the same!

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Both the inlet and exhaust side of the engine had the same oil seal fitted which resembles the brown seal with the flared base.
The 6 green seals that came in the kit, which I'm assuming to be for the inlet side, are actually considerably tighter than what was fitted to the engine. You might only just see it in the picture but it's worryingly obvious in real life.

I'm thinking the valve stem diameters may have been revised after all and the original larger exhaust valve seals then also fitted to the inlet side to account for the stem size increase.

Fortunately the valves still squeeze through these smaller seals, albeit a bit more snug, but I'm hoping that's fine as thermal expansion is more prevalent on the exhaust side and it was the inlet side which was leaking in the first place - a tighter seal should prevent that.

This is all terribly important because it's something you WILL need to consider if you're looking at replacing the valves or their guides - I haven't seen this mentioned anywhere before and it's still not conclusive but be advised.


Anyway, back to it...

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PostPosted: Sun Nov 24, 2019 2:44 am 
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So; after 15 hours of sanding, cleaning and sanding some more here's what the ports look like:

First the intake side
I blended the short radius into the seat and removed the worst of the casting flashes. The turbulent sharp edges are gone but I left the machined indentations as they were - They're appearing a lot more defined now without all the clutter around them and I hope the airflow sees it that way too.

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Seat Radius Form Comp.jpg
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Ports Comp.jpg
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Looking down the ports you can see I've smoothed the bowl where the seat machining met the casting and blended the bowl into the seat. I've smoothed the injector hump a little as well as the part of the roof just beyond in an attempt to increase the airflow capacity around the central divider and help that swirling motion of the air mixture as it enters the combustion chamber; I'm also hoping it's less of a sticking point for the fuel.

You can see the shmoothing a bit better here:

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Port Roof.jpg
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I've left the port walls textured on the inlet side but ran a 180-grit sanding buff along them to take off the sharpness and high points - Like a golf ball this should make for a faster surface, without the fuel atomisation problems that flat polishing can lead to.

Ideally I would have liked to knife edge the dividers a bit more, remove all traces of the cast lines and blend the seat lip the whole way around but space was pretty tight with the dremel body and I only have short fittings. I was doing most of this blind and it would have meant getting far too involved for the visibility and articulation I had.
Better to be safe than sorry!

I'll have to try and budget for one of the pen-like flex shafts and some longer bits next time..

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Last edited by Bunkey on Sun Nov 24, 2019 3:50 am, edited 2 times in total.

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PostPosted: Sun Nov 24, 2019 3:04 am 
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And the exhaust side,

There was so much crap hardened onto the combustion chamber, valves and exhaust ports as a result of the poor running - The last 7 months have seen more deposits than in the entire 7 years before it. The buildup in the exhaust ports was reducing their diameter significantly so even just cleaning this off is going to yield a huge benefit.

It wasn't easy and I'll be using fuel cleaners more often now to try and prevent it happening again.

Anyway..

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I smoothed the step just after the seat where the machining met the casting a bit off centre and relaxed the short radius at that point too.
I'd already done a bit of work to the dividers previously so I shaped this to meet the manifold angle a little better and finished up the exhaust side with a polish.


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Exhaust Ports.jpg
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Whilst I was here I removed a broken stud and replaced a thread I'd stripped a while ago.
Helicoils are pretty good - not overtightening things is better :thumbs:

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PostPosted: Sun Nov 24, 2019 10:28 pm 
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I will send my car up to you for an engine overhaul :lol:

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PostPosted: Mon Nov 25, 2019 12:40 pm 
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On Sunday you mentioned using fuel cleaners more often. What products and how often are you planning to use them. Thanks in Advance


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PostPosted: Mon Nov 25, 2019 5:47 pm 
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wee mac wrote:
I will send my car up to you for an engine overhaul :lol:

Hey I'm open to enquiries! Just don't expect a quick turnaround haha.


brixtonboy wrote:
On Sunday you mentioned using fuel cleaners more often. What products and how often are you planning to use them. Thanks in Advance

I'm going to have to do some research into this..

Most likely it'll be whatever I can get cheap which cleans the whole system and not just the injectors; the £7-a-shot that some of these products ask is pretty ridiculous though tbh.
Surfactants take a while to break down gunk - they only really become effective if you use them every time you fill the tank - so cost will be a big factor.

As an alternative: There are specialist treatments you can have done every so often which work a bit like steam cleaning the inside of the engine whilst it runs, so that might be worth a look. It takes a fine balance to achieve cleaning without hydrostatic lockup so it's definitely not a recommended DIY procedure, you wouldn't simply drip water into the engine although some people try!
If it aint too expensive then it might be worth having done every year or so depending on mileage and how shiny you like the ports :lol:

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