De comp a DE

[Jairn01]

Posting in this section as the engine is currently DE. Wondering if anyone has gone down the path of lowering comp by simply adding a slightly thicker HG. 

I can't seem to find info on ratios for different size HG's As I'm sure we all know -

De -10.1

Det- 9.1

I'm looking to get close to that ratio

and yes I know there are conflicted opinions on just whacking in a thicker gasket

[Ben C34]

Why?

 

[Jairn01]

Because I'm considering a DE+t conversion. But I'm not ready to strip the entire motor down to chuck in low comp forgies....

[Jairn01]

Or to rephrase - I'm not prepared to have the car off the road for an extended period of time while I wait to have an engine built $$$

[Ben C34]

You don't need to reduce the compression to turbo the engine.

[Jairn01]

Yea, I'm know. But for the sake of reliability ect, I'm looking to go down this path. Will also be trying to source a GTT exhaust cam (or aftermarket if funds permit)

[Ben C34]

5 minutes ago, Jairn01 said:

Yea, I'm know. But for the sake of reliability ect, I'm looking to go down this path. Will also be trying to source a GTT exhaust cam (or aftermarket if funds permit)

For the sake of reliably dont and undo bolts and let the nissan out.

many have added turbos without touching the engine. Reducing the comp ratio doesn't increase reliability, spend the money and time on decent ecu and tuning

[GTSBoy]

36 minutes ago, Jairn01 said:

Yea, I'm know. But for the sake of reliability ect, I'm looking to go down this path. Will also be trying to source a GTT exhaust cam (or aftermarket if funds permit)

As Ben said above.

In addition, it's not 1983 any more. You can have compression + turbo. anyone building a DET up these days should be looking to increase compression from what the factory had.

[Jairn01]

Yea look, im all about compression. Have +t swapped a couple NA cars without an issue....difference being they were like 1500$ shitboxes and didn't care if somthing went pop

- I've just read some conflicting information alot of which on this site, most say don't do it at all, others say, do it but don't go over 10psi, and some have had good results.

Edited May 9, 2020 by Jairn01

[GTSBoy]

Look at the dates on those posts.

[Shoota_77]

Lower the comp??  You've been watching 1998 YouTube videos!  Run 98 octane and you'll be absolutely fine. 90's turbo engines were designed with those comp ratios to handle the junk fuel back then. No such thing as readily available high octane fuel back then without going avgas or stupid expensive race fuel. 

The vehicle will be waaaaay better to drive off boost with the higher comp, better acceleration out of corners, etc. 

Most modern petrol turbo motors out of the factory are well over 10:1 ratio now. 

If you're being conservative limit your power with boost which is effectively what you're doing by lowering the compression ratio but making it a pig to drive at the same time!

Be a man and leave it how it is!  As Ben said, don't you dare let the Nissan out. Once you do you can never jam it back in there again!

[Jairn01]

Thank you for the honest feedback fellas, just gonna run with the C.R as it is, not like it's running 13:1.

 I will however still look to change the exhaust cam out As I've seen the specs it's just gross.

[KiwiRS4T]

BTW what engine are we talking about? RB20? RB25? Neo?

[Jairn01]

25Neo

Edited May 12, 2020 by Jairn01

[KiwiRS4T]

7 minutes ago, Jairn01 said:

25Neo

Strangely the R33 has the same cam for DE and DET but the Neo has a dramatically lower lift for the exhaust. You should be able to pick up a stock Neo DET cam easily from someone who has put  Poncams or suchlike in. Not worth getting aftermarket - you'll just go slower.