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Lower Compression for Turbo 

 

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Posted: Wed Jul 12, 2006 7:31 pm 
Getting Side Ways
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EBXR8380 wrote:
The correct or another term is quench . Opening up the chambers on the outer edges of valves is a good way to lower comp as it's bassically relieving valve which increases flow... Quench is not such a big deal with forced induction as it is with hi po n/a engine... But the idea is to get one big flame front and not many, as this causes detonation... Note the 351m / 400m motor in the States is notorious for detonation yet it has approx 8.5 compression and Clevo style open chamber heads.. The main reason for bad detonation?? The piston is designed to be way down bore .. The fix to this was to fit pistons with pin height lower essentually bringing piston closer to deck. Even though it raised compression it prevented detonation...



exactly the reason i don't like thicker head gaskets and head shims

 

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 Post subject: detination
Posted: Wed Jul 12, 2006 7:48 pm 
Parts Gopher
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I no this is way of the topic of turbo's but using premium unlended fuel will help stop detination.
The higher the octain rating of the fuel the less chance you have of detination.
I learn't this at TAFE today
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Posted: Sat Jul 15, 2006 12:24 am 
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tickford_6 wrote:
EBXR8380 wrote:
The correct or another term is quench . Opening up the chambers on the outer edges of valves is a good way to lower comp as it's bassically relieving valve which increases flow... Quench is not such a big deal with forced induction as it is with hi po n/a engine... But the idea is to get one big flame front and not many, as this causes detonation... Note the 351m / 400m motor in the States is notorious for detonation yet it has approx 8.5 compression and Clevo style open chamber heads.. The main reason for bad detonation?? The piston is designed to be way down bore .. The fix to this was to fit pistons with pin height lower essentually bringing piston closer to deck. Even though it raised compression it prevented detonation...



exactly the reason i don't like thicker head gaskets and head shims

Yep and GOOD safe tune!!!
I do find however that the smaller bore motors like 4.0 can get away with higher compression to a point...

 

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331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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Posted: Sun Jul 16, 2006 5:25 pm 
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nothing like a GOOD tune.
but you shouldn't just realy on the tunner. when the engine is built you should make every effort you can to decrease the likelyhood of detonation.

 

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Posted: Mon Jul 17, 2006 11:04 pm 
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tickford_6 wrote:
nothing like a GOOD tune.
but you shouldn't just realy on the tunner. when the engine is built you should make every effort you can to decrease the likelyhood of detonation.

Yes I think I may have got alttle carried away with 27cc dish with 61 cc chambers on my 330W strocker though...BUT it gives you every oppertunity to make BIG power...7.8 compression!!!

 

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As in ZOOM 126 edition
331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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Posted: Tue Jul 18, 2006 7:47 pm 
Getting Side Ways
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EBXR8380 wrote:
tickford_6 wrote:
nothing like a GOOD tune.
but you shouldn't just realy on the tunner. when the engine is built you should make every effort you can to decrease the likelyhood of detonation.

Yes I think I may have got alttle carried away with 27cc dish with 61 cc chambers on my 330W strocker though...BUT it gives you every oppertunity to make BIG power...7.8 compression!!!



tell me, how much boost do you plan on using?

 

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Posted: Mon Jul 24, 2006 11:39 pm 
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I have twin SC61's .. So far 18 Lb at 440 rwkw but have issues with corrupt spark....
So engine has come out to tidy some wiring on right hand side guard and cut back old loom for MAF etc...Then fitted a Motec crank angle senser / disc on front pulley.. I may have fond why I had issues??? The wire gong to alterrnator was close to sparl plug leads so there may have been some bad transmission interferance in electrical system?
The dissy is only used to pick up #1 cylinder now. All but one vanes have been removed...
Possibly 25 Lb boost..Will fitnew Haltech screen and wide band 02 senser for efficiancy and economy....

 

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As in ZOOM 126 edition
331 Dart block,3.25/ 4340 steel crank, Oliver rods,TFS ported track heat heads, TFS track heat inlet Twin SC61 turbo's
Project 1UZ-EF has started.. S475 Turbo 4.0 V8 Mustang Celica.....

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