HC turbodiesel estate.

[viva les vegas]

Just a thought on the lag side of things (I'm no good with diesels by the way) but I read there that the smaller turbo spooled up quicker, but had a limit on the upper end, and the bigger one had more upper end potential, but lower end lag. How about using both? I've heard about some manufacturer (might have been BMW) using a smaller turbo for the bottom end and a bigger one for the top end. Would something like that be doable??

[bikingnutcase0]

Yeah it's do-able, you're talking about sequential turbochargers. Theres a small one and a big one, and a flap that switches between them. Toyota used it in the mid nineties on Supras I'm fairly sure, and as you say I'm pretty certain I've seen a very recent BMW tv advert where they use it on a diesel.

With the Supras people tend to rip them off and fit two "medium-sized" ones as it were, that work together all the time with no changeover. Idea being two medium turbos flow as much gas as one big one, but spin up more quickly.

The sequential set-up is a little redundant these days however, as a variable A/R ratio turbo (that have been introduced in the last five/eight years or so) does the same job, only better. It has vanes all around the exhaust housing, that make it behave like a small turbo in one position, for quick spooling, and then open up and behave like a big turbo for lots of flow! We have one that I sectioned in the college, if you blow compressed air through it you can vary the speed by moving the vanes, would make a fun executive toy lol! They're not used on petrol engines much yet (I think Porsche are the only ones at the mo), as the metallurgy for the vanes isn't there to reliably withstand the heat in a petrol exhaust turbine, but most new turbodiesels have them. They're often cast into the exhaust manifold though, so difficult to steal for other applications...

Both things are Ideas I'd love to have a play with however! Good suggestion!

[bikingnutcase0]

I've not been on here for a while, work (and life generally) has been keeping me very busy, working three different jobs in a vain bid to make some money, planning a wedding ect. ect.

However, I've not forgotten about my Viva, done a few bits here and there.......

I got a little bit further with the rust repairs, although it still seems like a drop in the ocean in the grand scheme of things!

I patched up the driver's footwell. It's become a bit of a patchwork quilt, but rather than chop thw whole lot out and end up with something a totally different shape to original, I decided to patch up the bits with holes in and keep all the parts with ribs pressed into them ect, that would be difficult to replicate-

It's become a bit of a patchwork quilt

And I undersealed the living hell out of it, in a (probably vain) bid to stop it from corroding again....Ever!

And I undersealed the living hell out of it!

I've also modified the clutch release fork pivot, aquired the correct clutch, found the correct spigot bearing (and bought a new pressure plate, not the filthy peice of junk pictured!), in preparation for uniting the engine and 'box ready for offering up into the engine bay.

I've also done some work on the clutch assembly.

More to follow.....

[bikingnutcase0]

As I had some ambitious plans for the engine, and my collegue who has all the fancy equipment for cylinder head work is moving on to pastures new, I thought I'd better take advantage of the opportunity to use his kit while I had the chance.. (apologies now for a load of not-strictly-viva-related engine tuning nonsense!)

I stripped and cleaned the engine, and set about flow-testing and modifying the cylinder head.

First I pulled all the valves out , re-ground the seat area on the valves, and cut multi-angled valve seats into the head. Then I flow tested it, hoping to see an improvement in flow at low valve lift figures. Result-nothing, no improvement at all-Nada!

cutting multi-angle valve seats

Then I made a funky attatchment for the Lathe which by attatching an angle grinder allowed the re-profiling of the valve stem area, refitted the modified inlet valve and tested flow once more-
Result- squat, Sod all improvement! On the basis that this kind of modification weakens the valve, and reduces it's service life, and it took ages and produced no improvement I decided against doing it, and replaced it with a standard valve.

re-profiled inlet valve

Then I fired up the die grinder and ported the head somewhat.
Was interesting, theres a big bulge in the inlet port wall where the head studs pass through, that LOOKS as if it would be a massive restriction, however probing the port whilst on the flowbench with a selection of ball bearings on rods showed that actually, it's not, and even a slight building up of this area with chemical metal would probably yeild more flow. My collegue who's flowbench it is said some technical things about flow seperation and other things I didn't completely understand, and I left that bit well alone!

ported inlet port

More to come...

[bikingnutcase0]

I did what I believe is called "Pocket Porting", whereby the area around the valve guide and valve seat is ground, I smoothed out the transition from port wall to valve seat, and shaved down the bulge around the valve guide a bit. I did something similar to the exhaust ports as well.

result- somewhere around 8% improvement at high lift on the inlet ports, and approaching 10% on the exhaust side. Hopefully this will allow more air charge into the cylinder whilst off boost, and require a lower boost pressure for same fuelling/power output while on boost.

In the previous post the picture of the inlet port looks a bit scabby, grinding marks here and there, that's not the finished product, I did even everything up with some special abrasive cones, and actually contrary to popular belief surface finish makes no difference really, its all about the shape, not how shiny something is! Apparently the wall of the port is lined with a "boundary layer"of stagnant air, and as long as any roughness is not lumpy enough to break through this layer it wil make no impact on airflow whatsoever.

cyl head on the flowbench

Another thing I did, was put the pistons in a four-jaw chuck in the lathe, and then in the milling machine, and deepen the swirl-groove-pocket thingy to lower the compression ratio. As my engine began life as a non-turbo naturally aspirated diesel, it had a 22:1 compression ratio. As I am not only turbocharging it, but want to run much more boost and fuel than Isuzu originally intended I did some mathematics and figured out to drop the C.R. to 19.5:1 I would need to make the combustion chamber 3.289cc's bigger. Due to the complexities of machining with cr*p equipment, and me being possibly half-asleep, I accidentally went a bit far and have ended up more like 18.5:1. This could be an issue, the damn thing might not even start, but I have a set of extra glow-plugs I'll fit in the inlet runners, hopefully this will be enough! Only one way to find out.....

machined pistons

The last thing I'm in the process of doing now, is ceramic coating the piston crowns. this will theoretically reflect heat back into the combustion chamber, help starting, and help stop my now dramatically thinner pistons from melting. it requires baking on at 175 Celsius (gas mark 4) for an hour, causing much irratation to my darling fiance, and much hilarity with my guy friends about my "man baking" and how everyone now has broken teeth due to how hard my piston rock-cakes are ect. ect!

man-baking!

Next step is re-assemble the engine, bolt the gearbox on and offer it up inside the engine bay to see if it will actually fit with the carlton gearbox.

Oh, and the continuing rust crusade...... over and out!

[yoeddynz]

More on this please- very interesting

[bikingnutcase0]

Cheers! I'm encouraged by the fact people are interested

I've done only a small amount since the last update, I Plastigauge checked the big-ends (my 1.5td Isuzu Corsa ate a big end bearing, and I want this one to have the best chance possible!), and also checked it for crank end float.

I couldn't find any specs for acceptable big end clearance, but apparently the old rule of thumb is to provide .0007" to .001" of bearing clearance for every inch of shaft diameter in a stock engine. I calculated the Isuzu needed 0.0013"-0.0018", and when I checked them they were about 10% over that. I ordered new shells, and when I'd fitted the new shells they were then bang in the middle.

Plastigauge checking

With all the bolting on and off of big-end caps I got fed up with the 15NM, then +60deg, then +60deg business (or whatever it was) specified, so I did one to the specified torque and angles, then carefully measured the torque required to undo them, and used that figure.

similarly I couldn't find specs for crank end float, but found references to another "rule of thumb" (I forget what the measurement was), and when I checked it with a dial test indicator it was within the limit mentioned, so I was happy.

I also engaged in what I'm gonna describe as "ShimAgeddon"........ (Armageddon-the last battle between good and evil before the Day of Judgement. ShimAgeddon-the last battle between me and the bl**dy Isuzu valve clearances before the day of judgement!!)

Basically where I'd re-cut all the valve seats, it had recessed the valves enough to bring the valve clearances outside the range of available shims. To rectify this I basically shortened the valve stems a small amount, using the hideous angle grinder/lathe attachment-

Angle grinder/lathe attachment.

Then I fitted the smallest shims I had to each valve, measured the clearance using feeler gauges, then calculated the difference between actual clearance and required clearance, added this to the size of the existing shim to find the required shim. This worked reasonably well, however when I tried to order the new shims I discovered that two of them were no longer available, and I'd shortened the valve too much already for a different size to be used. This meant two replacement valves from a spare engine, seats re-cut on those, and grinding a little less off that time! I sorted though the two engine's worth of shims I already had and manage to find three of the sizes I needed. Then a month's wait as the other shims were on back order. They turned up yesterday, I fitted them, job done! Altogether it was something of an ordeal.

"ShimAggedon!"

[bikingnutcase0]

For a bit of light relief I made a choice on the colour. I really like the Vauxhall "Extra dark Wine" used on the "Sportshatch", its so subtle, I always thought they were just black until I saw one in the flesh as it were. Really really dark purple colour. As my car was burgundy, and I wanted a more modern (and consequently available!) metallic paint I found something called Volkswagen LC3U dark burgundy (used to paint Corrado's in the nineties I believe), bought a sample pot and painted a test piece. I'm very happy, it looks almost black until the sun hits it, and then it looks like this-

LC3U Dark Burgandy

I'm beginning to think about inlet/exhaust manifolds. I want to have tuned-length manifolds fabricated in stainless steel. I cant actually begin fabricating until I get the engine/transmission into the car to show me what clearance I have, and I can't design the lengths until I measure the camshaft duration for the tuning equations, and I couldn't measure the cam duration until I had the head on (which I do now) and had the valve shims in place. However what I did need to do before putting the head on was "Gasket Match" the inlet ports, I.E. do a little grinding to make sure that the outside of the port matched the profile of the gasket. Particularly important for me as I will use the gaskets as a template for the manifold flanges.

Before- the red marks are an outline of the inside of the gasket, and mark the material to be removed-

Inlet flange marked for gasket matching

and after-

after matching, finished port

Another thing I did was drill and tap one of the manifold flange mounting holes. On the engine originally one of the bolt holes is left blank, with no drilling or stud because the fuel pump prevents access to it in the car. I want to make sure the inlet manifold is bolted on as strongly as possible, to prevent a repeat of a boost leak I had on my Corsa, and am not concerned about the difficulty of accessing the aforementioned bolt/stud as access will be much better on my tubular fabricated manifold.

[bikingnutcase0]

So, I've done a bit more in the past couple of months, been rather busy getting married and re-modeling the house so most of this info is out of date, and the car has unfortunately slipped down the list of priorities for the time being. however I'll post everything up to date.

In the last post I was modifying the inlet ports, and matching them to the gasket profile. I then re-assembled the engine (hopefully for the final time!), and made some stainless flanges for the inlet and exhaust manifolds.

Back Together

Exhaust Flange

inlet flange

[bikingnutcase0]

Then I knocked together the beginnings of a sump (and oil scavenge pipe),

start of a sump

Bolted it to the gearbox and dangled it in there!

trial fitting!

This enabled me to start measuring and sizing up the engine and gearbox mountings.
First I drilled all the spot welds from the original engine mounting brackets, and removed those-

Removing factory mountings