Decompression plate 3mm and ratio

[siimsalabim]

I have 3mm decompression plate, and im wondering what compression ratio it will give me when im using 2 standard headgaskets with this plate ? pumanoob got 8:5:1 with 2mm plate . . . :roll:

 

[siimsalabim]

Hwo is smart here ? :grin:

 

[PumaNoob]

Sorry mate, I only just read your message.
I calculate that to be 8:1 ratio (7.97:1) but with an additional head gasket you will be a touch lower.

k:

 

[Wild E. Coyote]

the head gasket is 0.45 mm thick :wink:

 

[siimsalabim]

0.2 when tightened.

 

[PumaNoob]

Ok, so if it's 0.2mm, the exact compression ratio is 7.856:1

If it's 0.45, the exact compression ratio is 7.718:1

We might as well say rounding to the nearest 0.1, that with a 0.2mm gasket, it's 7.9:1, & with a 0.45mm gasket it's 7.7:1

 

[siimsalabim]

Kind of low . Garret t25 and low compression . Im hoping to see 200+ hp and i really hope this low thing is drivable .

 

[siju]

In low boost conversions it's not obligatory to lower the compression. There are plenty of Miata VVTs(10:1 compression) running 7-10psi with OEM compression.
As far as I understand the most important thing is to have really good ECU programming to avoid detonation. That's what kills pistons.

 

[PumaNoob]

[post]355440[/post] In low boost conversions it's not obligatory to lower the compression. There are plenty of Miata VVTs(10:1 compression) running 7-10psi with OEM compression.
As far as I understand the most important thing is to have really good ECU programming to avoid detonation. That's what kills pistons.

I agree, with higher octane fuel & good mapping, higher compression ratio is more efficient too, better power, better spoil, & better economy.

But there is less room for error with higher compression. For me personally, if I was going to run low boost, I'd still lower, but maybe around 9.5:1, a good compromise at low boost

 

[Wild E. Coyote]

Guys, no matter how low you go on boost, the weak links are the conrods. Have a look at them, they are the prime example of something that was optimized for its purpose; great for N/A revvy engine, but no good for turbo conversion. Yes, it would work, but the question is how long before it breaks down. In any turbo conversion you should upgrade the conrods IMHO.

 

[PumaNoob]

The conrods are the weak link for sure, that's what snapped in my 1.7 turbo. But if the turbo is bigger, the torque will be a bit lower on low boost so you can still get away with around 180ft/lbs, as long as heat is properly managed.

 

[siju]

Off course I agree that if you go down the boost road you have to treat the engine as a consumable!!

Pumanoob if you don't mind can you tell the ft/lbs of your 1.7 turbo and how many miles did it survived?
I want to turbo/supercharge my 1.7. Ideally I would want to supercharge it but I'll have to lose the A/C! Tough decision!

 

[PumaNoob]

I'll try and find the files for my 1.7, but I think it was over 200ft/lbs, I'd guess around 215-220?? And it lasted 5 or 6 years from memory, some hard launches on the drag strip, & some hard street driving, but never on track.

 

[siju]

:grin: Not bad performance at all!!