Compression Ratio With Pump Fuel

[styler]

Yeah its all relevant but a good starting point is duration and a static compression figure,

then also what fuel you want to run and lastly ignition timing can be backed off if

it pings from what I have heard.

[altezzaclub]

and lastly ignition timing can be backed off if it pings from what I have heard.

 

Yes, pinking is the fuel mix exploding instead of burning, and is initiated by the spark plug. Usually on wide throttle and low revs, so you can overcome it by changing down a gear.

 

Different to that is the pre-ignition from the mix actually dieseling without the spark plug being needed, which it what a motor will do when you turn it off and it runs on.

 

You can fix both with raising the octane, and fix pinking by retarding the timing. Having just gone from 95 down to 91octane to see what happens, I get a touch of running on after switching off, although I haven't had it pinking on acceleration.

[KE20Rally]

I had a similar Cam, standard pistons, twin webers and a fair amount shaved off the head (3mm) and no pinging. You will be ok as long as you put it on a dyno and check the tune, if you don't, you may end up rebuilding your engine again.

 

Pinging is actually the sound of 2 flame fronts hitting each other in the combustion chamber, one from the spark plug, and one from a hotspot in the combustion chamber (piston crown, carbon deposit etc), this gives instantaniously (spelling?) high combustion pressure, thus squeezing the oil from between crank and rod bearing, "spotting" the crank and eventually causing a bearing to spin, also melts pistons!

 

Number 1 rule when modifying engines "get a dyno tune/check"

 

 

Pete

Cheers,

 

Pete

[agius]

I had a similar Cam, standard pistons, twin webers and a fair amount shaved off the head (3mm) and no pinging. You will be ok as long as you put it on a dyno and check the tune, if you don't, you may end up rebuilding your engine again.

 

Mmm makes sence, alot of people mixed opinions

 

Was that motor you talking about a 3t?

 

Pinging is actually the sound of 2 flame fronts hitting each other in the combustion chamber, one from the spark plug, and one from a hotspot in the combustion chamber (piston crown, carbon deposit etc), this gives instantaniously (spelling?) high combustion pressure, thus squeezing the oil from between crank and rod bearing, "spotting" the crank and eventually causing a bearing to spin, also melts pistons!

 

Number 1 rule when modifying engines "get a dyno tune/check"

 

 

Pete

Cheers,

 

Pete

[agius]

I had a similar Cam, standard pistons, twin webers and a fair amount shaved off the head (3mm) and no pinging. You will be ok as long as you put it on a dyno and check the tune, if you don't, you may end up rebuilding your engine again.

 

Pinging is actually the sound of 2 flame fronts hitting each other in the combustion chamber, one from the spark plug, and one from a hotspot in the combustion chamber (piston crown, carbon deposit etc), this gives instantaniously (spelling?) high combustion pressure, thus squeezing the oil from between crank and rod bearing, "spotting" the crank and eventually causing a bearing to spin, also melts pistons!

 

Number 1 rule when modifying engines "get a dyno tune/check"

 

 

Pete

Cheers,

 

Pete

 

Mmhh makes alot of sence, every one has a mixed opinion about this

 

A dyno tune once everything is done was my initial plan from the start i really know how important a tune is.

 

Was the motor you were talking about a 3tc?

[agius]

I had a similar Cam, standard pistons, twin webers and a fair amount shaved off the head (3mm) and no pinging. You will be ok as long as you put it on a dyno and check the tune, if you don't, you may end up rebuilding your engine again.

 

Pinging is actually the sound of 2 flame fronts hitting each other in the combustion chamber, one from the spark plug, and one from a hotspot in the combustion chamber (piston crown, carbon deposit etc), this gives instantaniously (spelling?) high combustion pressure, thus squeezing the oil from between crank and rod bearing, "spotting" the crank and eventually causing a bearing to spin, also melts pistons!

 

Number 1 rule when modifying engines "get a dyno tune/check"

 

 

Pete

Cheers,

 

Pete

 

Mmhh makes alot of sence, every one has a mixed opinion about this

 

A dyno tune once everything is done was my initial plan from the start i really know how important a tune is.

 

Was the motor you were talking about a 3tc?

[KE20Rally]

Yep, 2t block with 3t crank/pistons/head, I am now running arias 12.1 comp pistons with a 296F schneider cam, pinged on 98 first time on dyno, had to switch to race fuel with that combo.

 

Cheers,

 

Pete

[agius]

Yep, 2t block with 3t crank/pistons/head, I am now running arias 12.1 comp pistons with a 296F schneider cam, pinged on 98 first time on dyno, had to switch to race fuel with that combo.

 

Cheers,

 

Pete

 

Wow 12 now thats heeps! Haha don't blame the motor for pinging in that situation

 

[KE20Rally]

See below for pistons, there was talk earlier about machining your block to increase compression ratio, IMO I would prefer to take the meat off the head, as once you start taking it off the block your pistons will sit proud of the block, and your pistons may foul with the head, as always, check your piston-head-valve clearances before final assembly.

 

Edited June 23, 2012 by KE20Rally

[SLO-030]

Yes, pinking is the fuel mix exploding instead of burning, and is initiated by the spark plug. Usually on wide throttle and low revs, so you can overcome it by changing down a gear.

 

Different to that is the pre-ignition from the mix actually dieseling without the spark plug being needed, which it what a motor will do when you turn it off and it runs on.

 

You can fix both with raising the octane, and fix pinking by retarding the timing. Having just gone from 95 down to 91octane to see what happens, I get a touch of running on after switching off, although I haven't had it pinking on acceleration.

 

PINGING!

[KE20Rally]

http://en.m.wikipedia.org/wiki/Engine_knocking

 

Its called a few Things

[bruce]

Here's some info for calculating the compression ratio with t-series dome pistons:

 

http://www.dorikaze.net/showthread.php?37478-AUTO-NERDS-T-series-compression-ratios

 

The dome is around 20.0 cc

[agius]

So after all that i found out the hard way why every one ditches the 3tc head for a 2tc head

 

Couldnt get more than 10:1 due to them damn air pump pollution holes in the head, the head is almost shaved right down to the threads

 

And again because of them pullution things, there was no point porting it because they have theese massive bumps in the intake ports, where the air pump hoses screw into...

 

I hope I'm going to be satisfied with the engine when i put it together..

 

[bruce]

Yeah, the 2tc head is a nicer starting base for an NA engine.

 

Normally people block up the ERG holes. With the bump in the exhaust ports, I think they could be ground down with a die grinder and deburr bit. I think people leave them in there and the setup has been successful (check out 3tcgarage, turbo applications). Porting the intake port is more important.

 

How much did you get shaved off the head? What did the chamber volume (cc) turn out to be?

Going by the Engine Analyzer Pro program your dynamic compression ratio works out to be 6.71 with the Crow cam and static compression ratio of 10. Ideally the dynamic compression ratio should be between 7 to 9. Looks like you would need a minimum of 10.5 static compression.

 

Could try a thinner head gasket:

 

http://www.euroexpor...89mm-c4176.html

 

Or you could put over sized pistons. Can get 1mm+ oversize. Going larger is only available in forged I think, like Wiseco or Arias. They've got more dome for compression. Expensive though.

Edited July 5, 2012 by bruce

[agius]

Yeah, the 2tc head is a nicer starting base for an NA engine.

 

Normally people block up the ERG holes. With the bump in the exhaust ports, I think they could be ground down with a die grinder and deburr bit. I think people leave them in there and the setup has been successful (check out 3tcgarage, turbo applications). Porting the intake port is more important.

 

How much did you get shaved off the head? What did the chamber volume (cc) turn out to be?

Going by the Engine Analyzer Pro program your dynamic compression ratio works out to be 6.71 with the Crow cam and static compression ratio of 10. Ideally the dynamic compression ratio should be between 7 to 9. Looks like you would need a minimum of 10.5 static compression.

 

Could try a thinner head gasket:

 

http://www.euroexpor...89mm-c4176.html

 

Or you could put over sized pistons. Can get 1mm+ oversize. Going larger is only available in forged I think, like Wiseco or Arias. They've got more dome for compression. Expensive though.

 

ahh godamn itt

 

they shaved it right down to the EGR holes thats the most they could go without interfering with the EGR holes..

 

10.1 compression was worked out with a 1.5mm thick head gasket

 

how much static compression would a 30 thou head gasket give me can that program work that out?

 

thank you so much for your time and every one else helping out i really appreciate it!

 

think its time to find a 2tc head..