Is this block $&#$%?

[allencr]

Just need to confirm that this block is gone?

Gone where?
No, it doesn't look pretty and doesn't look like a candidate for a race engine with machining/aligning $$$ invested in it, but if it's rare or you're desperate, it's solid enough.
If that crack pic is just an optical illusion & it's a DD & it's not getting super/boosted/turboed/NO2, then just skim it .25-.75. If the head has also been cut, cam timing adjusters would be nice.

[sergei]

Just need to confirm that this block is gone?

Gone where?
No, it doesn't look pretty and doesn't look like a candidate for a race engine with machining/aligning $$$ invested in it, but if it's rare or you're desperate, it's solid enough.
If that crack pic is just an optical illusion & it's a DD & it's not getting super/boosted/turboed/NO2, then just skim it .25-.75. If the head has also been cut, cam timing adjusters would be nice.

This is 3SGTE block, which means it was "turboed"...
I pulled the head off because of leaky gasket.
Do not want to skim a lot as it will raise the compression. (if raising compression is unavoidable, then I could get a cheap gen2 easily).
.25-.75, I assume that is mm? if head and block is skimmed to combined height of 1.5mm that will introduce piston to head clearance issues, increase the compression to ~8.9-9.0 (rough estimate), which puts it into gen2/gen4 range.

I am just thinking of value for money. All I want to do is run 1bar on track days with reliability in mind. I am not going to run stupid amount of boost or stupid amount of revs (rev limiter is set to 7200rpm, which is moderate). So in my opinion building a forged engine is waste of time and money.

Giving option of Gen3 that should be able to handle 1bar in stock form all day long (especially if it is running 98 and tuned "safe"), vs spending $$$ then having faith that engine builder didn't screwed up somewhere along in the process (improper bearing clearances, improper piston clearances, wrong hone pattern, various assembly mistakes).

[Scottie]

I have a gen1 motor thats done 160k. It was working when it was pulled out of the car.

[sergei]

I have a gen1 motor thats done 160k. It was working when it was pulled out of the car.

Can I look at it? let me know how $$$

[MilfHunter]

You gotta be real careful when skimming these blocks. Dunno why but mine was overskimmed and I'm stuck using 1.8mm gaskets on my GE.
Compresssion is 210psi (nuts in a road car!)


I think you could use late 5S-FE pistons to build a strong GTE with low compression, anyone tried it?

I hear you on the antifreeze thing, normally the gaskets come out looking like this

Who buys a performance car and then saves $20 buy not using antifreeze?

Probably the same mentality that goes with upping the boost while saving money on oil and engine cleaner

[sergei]

Compresssion is 210psi (nuts in a road car!)

most of the good (and not so good) engines will give you compression in that ball park (12-14bars). It is dynamic and not reflective of the static compression.
For example that block on my original post made 14bars (~205psi) on all four even though the compression ratio is 8.5:1.
I think compression test should treated as relative, and will only show really bad things (badly worn rings - that you could see wall of smoke anyway, cracked piston, spun bearing, badly blown head gasket - wall of steam out of exhaust will show it anyway).
Leak down test is little bit better at determining state.

[DVSMOTORSPORT]

Dunno why but mine was overskimmed and I'm stuck using 1.8mm gaskets on my GE.
Compresssion is 210psi (nuts in a road car!)

Your engine builder should have seen this and decked the pistons to suit.

[MilfHunter]

That's the kind of thing that happens when you rush an engine build. My fault

Sergei - I think you got Static and Dynamic mixed up. Static is with a gauge and dynamic has to worked out using volumes, cam timing etc.
Do you have a BGB? BGB states min static compression is:
ST165 - 128psi
ST162 - 142psi

At 210psi I'm stuck using 98RON, the oil pump has to be primed to start etc

[QikStarlie]

nar sergei is right. testing compression with gauge is just for fault finding

[Scottie]

I have a gen1 motor thats done 160k. It was working when it was pulled out of the car.

Can I look at it? let me know how $$$

Ok. I'll let you know after the holidays.

[sergei]

Sergei - I think you got Static and Dynamic mixed up. Static is with a gauge and dynamic has to worked out using volumes, cam timing etc.
Do you have a BGB? BGB states min static compression is:
ST165 - 128psi
ST162 - 142psi

At 210psi I'm stuck using 98RON, the oil pump has to be primed to start etc

Even at cranking the compression is already "dynamic" .
I did compression test many engines with a few different gauges, but most of healthy engines read in vicinity of 12 to 14 bar.
The cracked ring lands read about 4 - 5 bars (usually) and run bearing reads about 1-2 bars less than rest of the cylinders.
Worn rings only show up when you add little bit of oil and you get 2-3 bar increase. Adding oil to healthy engine would just increase by ~0.5bar at most (due to increased compression ratio).

Compression ratio is calculated just by volume ratio: volume inside of the combustion chamber when piston is TDC vs opposite. It is called static as there is no inertia of the air is involved.

When you crank engine it is dynamic (even if the RPMs are low, they still have a great effect), the compression increases due to inertia of the air and cam timing.

[DVSMOTORSPORT]

Adding new oil wont increase your compression, it will assist (very marginally) your starter motor in getting an increase in in engine speed while cranking, which will in turn give you more compression.

As for the rest of the results, they may have been the result you came up with at the time, but it wont be the same everytime.

Someone previously talked about using a compression test to find a spun/run bearing, thats not something you find by doing a compression test.

[sergei]

Adding new oil wont increase your compression, it will assist (very marginally) your starter motor in getting an increase in in engine speed while cranking, which will in turn give you more compression.

As for the rest of the results, they may have been the result you came up with at the time, but it wont be the same everytime.

Someone previously talked about using a compression test to find a spun/run bearing, thats not something you find by doing a compression test.

Adding oil into the combustion chamber will increase compression via two things:
1) it reduces effective combustion chamber size (this effect is minimal, barely noticeable in result)
2) it helps the rings seal (this effect is more apparent in engines with worn rings)

As for the spun bearing not affecting the result: it does.
The reason why it does, is because piston never reaches the TDC, thus the volume of combustion chamber at it least is increased, thus difference between max volume and min volume is less.

[DVSMOTORSPORT]

Ahh your meaning adding oil into the combustion chamber, when you said adding fresh oil I thought you meant doing an oil change, yes your right it does help the rings seal, but reducing the combustion chamber size.......... How much oil are you adding? haha

If a bearing is so badly rooted that it affects the compression then your going to hear it, even just by turning it over with a power bar etc. To not be able to hear it you would be looking at wear on the bearing of about .2 - .3 of a mm, I doubt that would make much difference to the compression (in saying this I have never done a comp test on a buggered bearing, if its fukd then its fukd)

[MilfHunter]

I don't see a worn bearing affecting the Compression ratio, a knocking bearing only needs a clearance of 0.08mm to sound pretty bad.

Back to compression, technically you are wrong and I quote:

"Definition: The Compression Ratio (CR) of an engine is the ratio of the cylinder volume compared to the combustion chamber volume. A cylinder with 10 units of volume (called the sweep volume) and a chamber with a volume of 1 has a 10:1 compression ratio. Static Compression Ratio (SCR) is the ratio most commonly referred to. It is derived from the sweep volume of the cylinder using the full crank stroke (BDC to TDC). Dynamic Compression Ratio, on the other hand, uses the position of the piston at intake valve closing rather than BDC of the crank stroke to determine the sweep volume of the cylinder.

The difference between the two can be substantial. For example, with a cam that closes the intake valve at 70º ABDC, the piston has risen 0.9053" from BDC in a stock rod 350 at the intake closing point. This decreases the sweep volume of the cylinder considerably, reducing the stroke length by almost an inch. Thereby reducing the compression ratio. This is the only difference between calculating the SCR and the DCR. All other values used in calculating the CR are the same. Note that the DCR is always lower than the SCR.

Dynamic compression ratio should not to be confused with cylinder pressure. Cylinder pressures change almost continuously due to many factors including RPM, intake manifold design, head port volume and efficiency, overlap, exhaust design, valve timing, throttle position, and a number of other factors. DCR is derived from measured or calculated values that are the actual dimensions of the engine. Therefore, unless variable cam timing is used, just like the static compression ratio, the Dynamic Compression Ratio, is fixed when the engine is built and never changes during the operation of the engine. "

[sergei]

I don't see a worn bearing affecting the Compression ratio, a knocking bearing only needs a clearance of 0.08mm to sound pretty bad.

Back to compression, technically you are wrong and I quote:

"Definition: The Compression Ratio (CR) of an engine is the ratio of the cylinder volume compared to the combustion chamber volume. A cylinder with 10 units of volume (called the sweep volume) and a chamber with a volume of 1 has a 10:1 compression ratio. Static Compression Ratio (SCR) is the ratio most commonly referred to. It is derived from the sweep volume of the cylinder using the full crank stroke (BDC to TDC). Dynamic Compression Ratio, on the other hand, uses the position of the piston at intake valve closing rather than BDC of the crank stroke to determine the sweep volume of the cylinder.

The difference between the two can be substantial. For example, with a cam that closes the intake valve at 70º ABDC, the piston has risen 0.9053" from BDC in a stock rod 350 at the intake closing point. This decreases the sweep volume of the cylinder considerably, reducing the stroke length by almost an inch. Thereby reducing the compression ratio. This is the only difference between calculating the SCR and the DCR. All other values used in calculating the CR are the same. Note that the DCR is always lower than the SCR.

Dynamic compression ratio should not to be confused with cylinder pressure. Cylinder pressures change almost continuously due to many factors including RPM, intake manifold design, head port volume and efficiency, overlap, exhaust design, valve timing, throttle position, and a number of other factors. DCR is derived from measured or calculated values that are the actual dimensions of the engine. Therefore, unless variable cam timing is used, just like the static compression ratio, the Dynamic Compression Ratio, is fixed when the engine is built and never changes during the operation of the engine. "

Good to know correct terminology.