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Engine Specific Info and Questions => IDI Engine => Topic started by: Smokey Eddy on January 06, 2009, 12:55:11 pm

Title: what is the comp ratio?
Post by: Smokey Eddy on January 06, 2009, 12:55:11 pm

what is the compression ratio for a 1.6td mf?
I am curious but i can't find the number?
If someone just pm's me i'll delete this post. It's kind of useless.

Title: what is the comp ratio?
Post by: TurboJ on January 06, 2009, 01:15:30 pm

23.0 : 1


I don't think it's useless - you can't find that too easily on the net

Title: what is the comp ratio?
Post by: Smokey Eddy on January 06, 2009, 01:16:27 pm

sweet thanks TurboJ!

Title: what is the comp ratio?
Post by: shegel on January 06, 2009, 01:31:55 pm

i thought the turbo cars were 17:1 instead of the 23:1 like the n/a cars

Title: what is the comp ratio?
Post by: TurboJ on January 06, 2009, 01:36:30 pm

Nope..  Engines are identical apart from the piston oil squirters the TD has.

Title: what is the comp ratio?
Post by: Vincent Waldon on January 06, 2009, 02:30:40 pm

Quote from: "shegel"

i thought the turbo cars were 17:1 instead of the 23:1 like the n/a cars

I've heard this thought before from other people as well... I wonder if it partly comes from the world of gasser engines where it's common to reduce the compression ratio when adding a turbo to reduce the chances of detonation?

In any event, diesels don't have that same concern and so there's no real reason for the compression ratio to change when you add a turbo... bring it on!!!

Title: what is the comp ratio?
Post by: shegel on January 06, 2009, 02:47:23 pm

Quote from: "TurboJ"

Nope..  Engines are identical apart from the piston oil squirters the TD has.

dont forget that the actual pistons are notched so they dont hit the squirters

Title: what is the comp ratio?
Post by: TurboJ on January 06, 2009, 04:28:31 pm

Quote from: "shegel"

Quote from: "TurboJ"

Nope..  Engines are identical apart from the piston oil squirters the TD has.

dont forget that the actual pistons are notched so they dont hit the squirters

Good point.

Also, about the compression ratio. Many IDI and TDI engines do indeed have lowered compression ratio when a turbo version is made. Even some VAG diesel engines do. Personally I have always wondered why they didn't do it with the 1.6 TD. Maybe because of the relatively low output they didn't feel the need. If only they had known what enthusiasts will be doing to those engines in 20-years time....

Title: what is the comp ratio?
Post by: Sprockets on January 07, 2009, 07:40:34 am

Indeed, the high CR's are due to getting the damn things going! a CR of 23:1 is FAR from optimal, I believe the best is in the 15:1 range.  I did do some research into this a while back and it made some fascinating reading.  I'd advise the curious to plunge some key words into google and have a little look.  I'm not going to comment much further as it was a while ago I did all this, and I can't be 100% sure of my facts, so I don't want to tell people wrong information :)

-Gavin