Fuel injection rebuild

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Re: Fuel injection rebuild

Post by Simmy » Thu Feb 21, 2019 10:27 am

You guys can blame Tony - I think his immense VW/engineering brain forces me to up my game. But hopefully I am not the only one learning stuff here :)

Hopefully no surprises when I attempt measuring the deck height this weekend!



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Re: Fuel injection rebuild

Post by Riaan.N » Thu Feb 21, 2019 1:31 pm

Simmy wrote:You guys can blame Tony - I think his immense VW/engineering brain forces me to up my game. But hopefully I am not the only one learning stuff here :)

Hopefully no surprises when I attempt measuring the deck height this weekend!

Agree totally and thank you Simmy for sharing your buildImage I also try and follow and pick up tips & tricks!

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Re: Fuel injection rebuild

Post by Wentzel » Thu Feb 21, 2019 3:30 pm

It is always good to watch and learn. I love reading build threads always something to learn or figure out.

Deck height should be simple. What are you aiming for? Using copper gaskets or not?
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Re: Fuel injection rebuild

Post by Simmy » Thu Feb 21, 2019 4:31 pm

I am pleased that there is some entertainment value in this. Its certainly a long process, but I feel its actually going somewhere now.

I am aiming for 1.4mm, which will give me a static CR of 7.82 (dynamic at 6.9 according to the interweb's calculator). Its slightly lower than I would like for NA, but if I turbo later, then it doesn't make sense to flycut the heads (56cc at the moment).
I was going to use the copperslip method someone (Armand?) recommended to you at some point in the past. I have already lapped the barrels into the case and heads, so I am happy they will be pretty leak-free. Copper gaskets will come later if I need to drop the CR for the turbo.

Out of interest - which is better: checking deck height with or without rings installed? checked TDC without and that was pretty accurate.

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Re: Fuel injection rebuild

Post by Wentzel » Thu Feb 21, 2019 6:16 pm

My cr is around 7.9 on my current engine and it works good for me so your cr should be good.

On my new build I used copper gaskets and cut the sleeves to give 0 deck so the combustion will be in the head and gasket and not on the sleeve at all. This is my first attempt at it so can't say how it works from experience but ot has been done with great success from what I read and was told.

My current engine has 1.5 deck and I used the copper slip, it is still working well so you should be good.

The copper slip was a tip from Armand on a post here on the forum.
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Re: Fuel injection rebuild

Post by Simmy » Mon Feb 25, 2019 8:36 pm

Post weekend update:
I managed to measure the end-play on the crank as well as its runout. End play is at 0.087, so I will need 3x0.26mm shims to bring it right into into spec. The runout was also minimal - I don't recall the figure right this minute, but I do remember it was 1/3 of the allowable maximum (yay!).

And then I got a little wound up in measuring deck height. I made up a "depth gauge" using my dial indicator and a piece of ally-angle and set about trying to measure it. As it turns out, the machining ridges make it a little variable, so I opted for the statistical approach and took a bunch of measurements to get an average over the surface.... I realise that's probably not the normal way to do it, but just taking measurements from the piston centre gives you basically the same result. I believe this to be a function of 2 things: the crank not being parallel with the parting line (which explains ~0.03mm variance) and stacking of tolerances (which seems to be roughly the same).

Now, given that the tops of cylinders are inline (checked using a straight-edge) and I want to keep it that way means that whatever I do must be done equally to all cylinders on that side. Now I figure the following is possible (my machinist knowledge is sorely lacking, so please correct me if I am assuming miracles):
  1. Swap around the rods and pistons for cylinders 2 and 3, which are the "longest" and "shortest" respectively. Hopefully this will cancel out and presto... everything works out and we go off early for tea and scones. Will try this during the course of the week.
  2. Sand down or machine the tops of the pistons to get them all to spec. Its not a lot of material, so I don't think it would compromise the parts, and I can still do this from home, but it will mean balancing them again.
  3. Deck the case slightly and at an angle to match the out of parallel issue, and then shim for correct height. I think this is probably the right way to do it, but I don't know if its reasonable to expect someone to accurately machine at the angles required to get this straight.
  4. Just shim the buggers to get 1.4mm at cylinder 3 and move on with life. Note that 0.1mm in deck height is 0.64cc's... 1.14% change which seems silly to quibble over.
Imagine my surprise when the first cylinder came out dead on 1.4mm.... beginners luck I guess...
Image

The array of measurements on cylinders 1 & 2
Image

The array of measurements on cylinders 3 & 4
Image

My attempt to measure the parallelism of the crank relative to the parting line. Basically across bearings 1 & 3, there should be about 0.03mm.
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Re: Fuel injection rebuild

Post by fourier » Mon Feb 25, 2019 9:14 pm

Image

Image

This is how I get the job done with repeatable results...

I use a thick deck plate and torque it down to head nut spec.
Then I place the piston at TDC using a dial gauge measuring in the centre of the piston, to avoid effects of the piston rocking about the wrist pin.
Then determine deck height using a depth micrometer, also measured in the centre of the piston.
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Re: Fuel injection rebuild

Post by Tony Z » Tue Feb 26, 2019 3:42 am

I like to aim for 1.25 to 1.4mm on most builds. But really, anything from 1.2 to 1.5mm is fine.
On my bus engine, I used two different sets of barrel shims to get 1.38mm (from memory) on both sides. The crank obviously wasnt perfectly in the center. So for you, I'd try to get shims 0.1mm thinner to get your 1&2 side lower to match your 3&4. But, yours are still closer than stock ever was, and its within the "tight" side of deck height, so you could also just run it as is.
Whatever you do, just ensure you keep the barrels at the same height to ensure cylinder sealing. Dont worry about fancy decking which no-one will do correctly and you'll probably end up with a scrap case.

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Re: Fuel injection rebuild

Post by Simmy » Tue Feb 26, 2019 7:59 am

fourier wrote:
Mon Feb 25, 2019 9:14 pm

This is how I get the job done with repeatable results...

I use a thick deck plate and torque it down to head nut spec.
Then I place the piston at TDC using a dial gauge measuring in the centre of the piston, to avoid effects of the piston rocking about the wrist pin.
Then determine deck height using a depth micrometer, also measured in the centre of the piston.
I have seen the deck plates and they look like they are substantially more rigid than my fabricated tooling (I did observe bending when I first torqued it up, but then changed tact and used the flat bars to hold it down instead). A depth mic would also be great, but I didn't think it was worth getting one for this one build. And the issue is not so much with repeatability - I can get the same reading within a few hundredths - its that it varies over the surface. I think the difference is that the mic's flat end wont be subject to surface imperfections, whereas the ball on the dial gauge would?
Tony Z wrote:
Tue Feb 26, 2019 3:42 am
I like to aim for 1.25 to 1.4mm on most builds. But really, anything from 1.2 to 1.5mm is fine.
On my bus engine, I used two different sets of barrel shims to get 1.38mm (from memory) on both sides. The crank obviously wasnt perfectly in the center. So for you, I'd try to get shims 0.1mm thinner to get your 1&2 side lower to match your 3&4. But, yours are still closer than stock ever was, and its within the "tight" side of deck height, so you could also just run it as is.
Whatever you do, just ensure you keep the barrels at the same height to ensure cylinder sealing. Dont worry about fancy decking which no-one will do correctly and you'll probably end up with a scrap case.
Thanks for the clarity on tolerance. I still want to try swapping the parts around to see if I can get it a little closer, but I will also look at getting shims for the one side to keep things as even as I can.

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Re: Fuel injection rebuild

Post by Simmy » Fri Mar 15, 2019 7:29 am

After what seemed like a million combinations of rods and pistons, I managed to get the deck height evened out between all of the cylinders, with the 1-2 side coming out at 1.34-1.36, and on the 3-4 side 1.24-1.26 (so one set of shims will be needed). Its definitely overkill, but I had the time... so why not.

Made up the adjustable pushrod yesterday, so hopefully I can get onto checking the valvetrain geometry over the weekend, and cut the pushrods to length. I see that some people do this with a pipe cutter... which I can do, but is it not better to do this with a lathe? Chromoly seems like it would really challenge the pipe cutter.

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Re: Fuel injection rebuild

Post by Simmy » Fri Mar 15, 2019 7:43 am

Oh... and I was fortunate enough to have earned a bit of a bonus at work, so I am going to treat myself with some parts. Some of the ideas I am considering are:
  • Ceramic coating pistons, valves & heads. This is almost certainly overkill for this build in NA configuration, but I am thinking longer term when I do forced induction. @Wentzel - I think you only coated the new engine, and your current one is really running well... How much more could you get out if it if you had done this? If I were to try get mine to run like yours (I think my heads are more restrictive and I dont have the dual throttlebody intake like you do), would you think the coating would help adding boost?
  • Swap out the ECU to a unit compatible with a crank trigger. The current Gotech unit and Distributor (modified Golf - of which I am feeling suspicious as to how well it works, since it certainyl doesn't fit well) are unused, so I could probably sell it and get something for it, but I think the tuning later on will benefit from the accuracy of a crank trigger. I also already have an IGN-4 coil pack from my old Mini Cooper, which means I don't need that.
I am not sure if I can do both, but maybe you guys have strong feelings about it one way or the other.

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Re: Fuel injection rebuild

Post by Tony Z » Fri Mar 15, 2019 12:27 pm

crank trigger is a good call. Surely you can add it to your Gotech?
the bigger the spark you can get, the better.

Ceramic coating helps, there is no debate here. If nothing else, use it on your exhaust valves.
Dont think of it as allowing more boost, think of it as keeping your charge cooler inside the chamber and thus reducing the chance of detonation. If you coat the piston tops, it just might save them if you ever lean out under boost.

For the pushrods, use a dremel and cut-off wheel, then file it flat. The tube cutter will bend the tube inwards a little causing a stress point and also making it difficult to get the tip in without removing material from the ID.

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Re: Fuel injection rebuild

Post by Simmy » Fri Mar 15, 2019 1:40 pm

You would think that the ECU could, but it only works with a trigger per event, not a toothed index system. Wish I knew that at the time we bought it...
I think the bigger Gotech units have the same wiring harness, so I could get lucky and not have to rerun that.

I will look into the cylinder tops and valves then. The heads and exhaust ports get pricey quickly.

And thanks for the Dremel idea. That certainly would be easy enough to managed with a bench sander as well.

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Re: Fuel injection rebuild

Post by Wentzel » Fri Mar 15, 2019 2:29 pm

Glad to see an update have been waiting. I did thr valves and piston tops on my engine wotch ceramic. Would have liked to do chambers and everything but price was a problem too.

I cant remember if your engine was balanced already. If you still have to I suggest doing it before the ceramic to avoid damage to the pistons coatings.
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Re: Fuel injection rebuild

Post by Tony Z » Fri Mar 15, 2019 2:48 pm

it would be worth coating the exhaust ports too, this keeps the head temps a fair bit lower

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