Steve's Sport Evo Project

[stevesingo]

Cheers Jake. It's all your fault [peace]


The full results...

Piston A
3.66
3.66
3.56
Average 3.63

Piston B
3.46
3.56
3.46
Average 3.49

Piston C
3.36
3.46
3.46
Average 3.43

Piston D
3.96
3.86
4.06
Average 3.96

With a bit of juggling of the smallest pistons to the largest chambers, I get the following combination...

Chamber 1 - Piston C Compression 11.91:1

Chamber 2 - Piston D Compression 11.885:1

Chamber 3 - Piston A Compression 11.93:1

Chamber 4 - Piston B Compression 11.935:1

This gives a spread of 0.05:1.

Because I have 0.25mm of the dome left on each piston I can loose a little material to try to equalise. But, this nay effect the balance of the pistons, so I can only take material off the heavy pistons. I will look in to it and post back.

Just to put in to perspective 0.05:1 difference in compression is 0.27cc or about 0.1g of aluminium.

Steve

[UweM3]

just out of curiosity, how much is your piston sticking out of the block face on TDC?

[stevesingo]

On average 0.56mm.

This is using the same rod and the same crank journal.

I'll check the individual pistons with their rods in the correct bore once I have it together.

Steve

[stevesingo]

As piston C was a little heavier than Piston B, I decided to swap them but also remove the remainder of the dome from Piston C, which is a mere 0.25mm.

I also removed a little from Piston A to lower the compression a little as chamber 3 had the highest compression. Unfortunately, Piston A was on the light weight side, so I couldn't remove as much as I would have liked.

We now have

Chamber 1 - Piston B Compression 11.900:1

Chamber 2 - Piston D Compression 11.889:1

Chamber 3 - Piston A Compression 11.926:1

Chamber 4 - Piston C Compression 11.906:1

The difference is now 0.037:1 across the 4 cylinders.

I'll buff up the piston crowns tonight and match the lightest rods to the heaviest pistons. This won't make much difference as the weight of the rods is very similar across the four.

More to follow...

[stevesingo]

In response to Uwe's question, in detail...

I measured the distance from centre of piston pin to the face of the piston, in the area where it causes quench.

Piston A 30.67

Piston B 30.67

Piston C 30.69

Piston D 30.66

The average is 30.6725, lets call in 30.67.

Add this to the rod length and half the stroke length will give the full height of the assembly.

43.5+144+30.67=218.17mm

A new block has a deck height or 217.5mm

Piston pop up = Assembly height-deck height.

218.17-
217.5=
0.67mm. I will check this when I put the pistons in tomorrow or Thursday.

Quench = gasket thickness-pop up

GpA 1.4mm
Stock 1.82mm

Quench with GpA gasket= 1.40-0.73= 0.73mm (BMW MS spec is 0.8mm I believe) so a little tight.

Quench with Stock gasket=1.82-0.73= 1.15mm. A lttle slack.

I will check this when I put the pistons in tomorrow or Thursday.

Steve

[Jake]

This is definitely one for the hard drive. Excellant info mate.

Jake

[stevesingo]

I have installed the pistons and checked the pop up

Cyl 1 0.58mm

Cyl 2 0.60mm

Cyl 3 0.59mm

Cyl 4 0.59mm

These were measured in the centre of the piston to avoid the rocking of the piston in the bore throwing the readings off. I then subtracted the dome height from this to get the pop up.

There seems to be a slight discrepancy between these installed figures and what I calculated. This maybe because I never measured the block, stroke or rod lengths. I did check the rod of the cylinder that had the damage and it was 144.002mm.

With the GpA gasket quench is as follows.



Cyl 1 0.82mm

Cyl 2 0.80mm

Cyl 3 0.81mm

Cyl 4 0.81mm

Near enough to the BMW MS spec of 0.80mm.

Forgot the camera again!

Steve

[UweM3]

I have installed the pistons and checked the pop up

Cyl 1 0.58mm

Cyl 2 0.60mm

Cyl 3 0.59mm

Cyl 4 0.59mm

These were measured in the centre of the piston to avoid the rocking of the piston in the bore throwing the readings off. I then subtracted the dome height from this to get the pop up.

There seems to be a slight discrepancy between these installed figures and what I calculated. This maybe because I never measured the block, stroke or rod lengths. I did check the rod of the cylinder that had the damage and it was 144.002mm.

With the GpA gasket quench is as follows.



Cyl 1 0.82mm

Cyl 2 0.80mm

Cyl 3 0.81mm

Cyl 4 0.81mm

Near enough to the BMW MS spec of 0.80mm.

Forgot the camera again!

Steve

On a standard SE block with OEM rods and pistons they stick out 0.7mm from the block face.

0.8 is spot on IMHO

Where did you get the info of 0.8mm QUENCH?
I wouldn't run this on a mostly road going engine.

[stevesingo]

I seen to remember John posting it up somewhere, and Jake also refers to 0,8mm.

Steve

[Wiretowner]

Hey Steve, firstly thanks for sharing this journey with us. Some cracking information for the archives. Between you and Jake, the ones of us building 2.5's with similar specs are getting some amazing insight and how-to info. Just a question, when all said and done will you get your rotating mass balanced?

[stevesingo]

I decided to not have the crank, clutch, flywheel and damper balanced. There is no where near me that does this and given my experiences with 3rd party work, I didn't want to risk someone screwing it up good and proper. I figure the BMW dynamic balance is good enough, and balancing doesn't add power any way!

As for the pistons/pins/rods, I weighed everything and paired up lightest rods to heaviest pistons. The resulting variation is 1.58g lightest to heaviest. Stock tolerance for the rods is + - 4g.

So, what does this mean?

At 8000rpm, the piston is subjected to slightly over 4000g acceleration!

1.58g exerts a force of 0.01549 Newtons

0.01549*4000=62 Newtons

62 newtons is 6.32kg.

That 1.58g is therefore 6.32kg at 8000rpm. An extra 6.32kg of load on the conrod/crank pin would not be critical IMO. If the engine is that close to the limit, there is something fundamentally wrong.

I'll post up all of the measured weights later.

Steve

[Wiretowner]

If there is one thing we can be assured of on this forum (from a chosen trustworthy few)... its detail, maths and formula's. Thanks Steve.

When you put it like that who can argue!?

[stevesingo]

When installing pistons I tightened the rod bolts by measuring the stretch of the bolt. The Arrow spec is 0.0055"-0,0059" of stretch. I had the tool to hold the DTI made at work, in Titanium! No need, but that is what we use at work, so it is easy to get off cuts.

Bolt before tightening


Bolt after tightening


Pistons installed


Head on


Cam tray on


I have to re install the cams and re check the valve clearances.

That's all for now...

[stevesingo]

Cams went in yesterday. It's amazing that I went to great lengths to set the valve clearances only to find that now it is back together 8 valves are out.:confused: After some juggling about, and using some spare shims, I managed to get to the point that I had only one shim that needed adjusting. 0.01mm needed removing which I did on a whet stone in about 5 mins. Phew. Probably mixed them up on disassembly knowing me.:rolleyes:

Next job, timing the cams. In order to save a little time I used a permanent pen to mark the cams and cam bearing cap at TDC before disassembly. These meant that I could get the cam wheels on the correct tooth on assembly, without messing about.

The first thing you need to do is mount your cam timing disc on the front pulley. I used double sided tape for this and mounted it with the engine at TDC, but aligned the TDC marker on the disc with the alternator bracket bolt. This was where I was intending on mounting my pointer. The pointer is made by bending a piece of wire. Before you fix the disc in place, don't forget to put the socket on the crank nut/bolt and make sure tour extension fits through the hole in the disc. Otherwise, you have no means of easily turning the crank.



Finding TDC. As most will realise the TDC marker on the engine may not be very accurate. To find TDC I used a DTI over the No1 sparkplug, using an extension to allow the piston to operate the DTI. The piston dwells at the top for quite a few degrees around TDC, so what I did was bracket a point 0.100" of piston depression either side of TDC.

1, Rotate the crank and find the maximum height of the piston and roughly set the pointer to the TDC marker. Note the DTI measurement at TDC.

2, Rotate the engine clockwise until you have the piston is 0.100" BTDC. Note what degrees on the timing disc this occurs. 22deg BTDC.

3, Continue rotating until the piston has passed TDC and in now 0.100" ATDC. Note what degrees on the timing disc this occurs. 28deg ATDC.

4, Now we can find the centre of the dwell period. Add both readings together 22+28=50deg then half this number to find the centre of the dwell period; 50/2=25deg.

Add this to the BTDC number 22deg BTDC+25deg-3deg ATDC.

5, Rotate the engine again this time stopping at 3deg ATDC. Adjust the pointer to TDC on the disc.

This now should be TDC. But always recheck by repeating the above. TDC minus 0.100" should occur 25deg BTDC/ATDC.


It doesn't matter what height below TDC you use. I used 0.100" because my DTI is imperial.

It is quite difficult to turn the crank small amounts accuratly. I found that if you stop a little short of where you want to be and use a lever on the ring gear to make the fine adjustments.



Hope that makes sense.:confused:

Next is to set the cam timing...

It is useful, when initially installing the cams, to set them slightly advancedso the peak lift for the cams occurs early. It makes setting the exact measurement easier.

I used a tool produced specifically for the s14 engine by JAKE that hold the DTI at the correct angle above the valve bucket, with a long thin probe on the DTI. It was a god send!



Finding the point where peak lift occurs relies on finding the centre of the dwell time at peak lift. The pics show the Exhaust cam.

1, Turn the crank until the cam dwells on peak lift and zero the DTI.

2, Turn the crank again until you get to a point below peak lift, I used 0.010" below peak lift.

Note the deg this occurs.

3, continue to turn the crank until the cam passes peak lift and returns to your set distance, 0.010" in my case.



Note the deg this occurs.

4, Calculate the centre of the dwell point: 124-88=36/2=18

Peak lift is then 18deg after 88deg= 88+18=106deg BTDC. Spot on.

If you had initially set up the cams a little advanced and found that peak lift was at 111deg BTDC, i.e earlier than 106 BTDC, then correcting the timing is easy.

1, Turn the crank until you reach 111 deg BTDC (peak lift).

2, slacken the pulley retaining screws enough to allow the pulley to turn without turning the cam.

3, turn the crank clockwise (always clockwise!) until the crank is at 106deg BTDC. Keep an eye on the DTI so you are sure the cam isn't moving with the pulley.

4, Tighten the pulley retaining screws and use the procedure above to recheck.

That is why it is a good idea to initially set the cams advanced.

If the cam is retarded, i.e you find peak lift is 100deg BTDC you need to slacken the pulley retaining screws and turn the crank backwards to put the cams in a retarded position and start again.

Hope this is of help to some.

Steve

[Yan-3]

even though ill probably never be going all out like this, i love this thread, your level of comitment after what happened with the block and the knowledge is over the top. thank you for posting photos to explain some stuff, as sometimes i find myself lost. this thread is amazing!