high compression head
Moderators: daewoomofo, Moderators Group
high compression head
when are they used, what are the pros and cons, any other info that i should know before purchase
car is coming along ever so slowly, gotta stop getting my funds of the government
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Audacity Racing
- moron
- Posts: 4493
- Joined: Wed Dec 08, 2004 5:18 am
- Location: Knoxville, Tennessee
- Contact:
WHEN USED: higher compression engines cram more "explosion" in a tinier space, resulting in a higher power/liter scenario. most "race" engines in touring cars and le mans style cars are very high compression, that's why they use a super high octane gas or methanol as their primary fuel
a few things...
~odds are it's been shaved (material has been removed from the deck surface)... this can cause small timing changes that can result in massive changes once the engine reaches high rpms. this is caused by the missing material making the timing belt travel smaller over-all resulting in a funny timing scenario
~higher compression means that you'll either have to swap the pistons out to keep the stock compression ratio, or switch to higher octane rated gasoline. the higher compression will create higher temperatures inside the cylinder, which can cause detonation if the fuel is a low grade (detonation being when the explosion happens without the spark going off, meaning it could potentially destroy a piston or valve)
~colder spark plugs need to be used. the increased compression will again be hotter and may be too hot for the spark plug to ignite, thus you need a colder rated spark plug.
~depending on the rpms you expect (most high compression engine applications rev way high) you may want/need reinforced valve-springs to prevent float. float is where the valve stays down inside the cylinder even when the cam isn't in contact with the tappet system. our engines are already prone to valve failure because they are interference engines, if your valves float, you run a higher risk of impact with a piston due to the missing material (**note: engine tolerances are very very tiny, by removing even the slightest bit of material from teh head, you could be placing the valve directly into the piston's way)
there is lots more that can happen depending on how powerful you intend on going with the whole setup and how high you plan on revving
sorry that was so long, i tried to be pretty comprehensive
a few things...
~odds are it's been shaved (material has been removed from the deck surface)... this can cause small timing changes that can result in massive changes once the engine reaches high rpms. this is caused by the missing material making the timing belt travel smaller over-all resulting in a funny timing scenario
~higher compression means that you'll either have to swap the pistons out to keep the stock compression ratio, or switch to higher octane rated gasoline. the higher compression will create higher temperatures inside the cylinder, which can cause detonation if the fuel is a low grade (detonation being when the explosion happens without the spark going off, meaning it could potentially destroy a piston or valve)
~colder spark plugs need to be used. the increased compression will again be hotter and may be too hot for the spark plug to ignite, thus you need a colder rated spark plug.
~depending on the rpms you expect (most high compression engine applications rev way high) you may want/need reinforced valve-springs to prevent float. float is where the valve stays down inside the cylinder even when the cam isn't in contact with the tappet system. our engines are already prone to valve failure because they are interference engines, if your valves float, you run a higher risk of impact with a piston due to the missing material (**note: engine tolerances are very very tiny, by removing even the slightest bit of material from teh head, you could be placing the valve directly into the piston's way)
there is lots more that can happen depending on how powerful you intend on going with the whole setup and how high you plan on revving
sorry that was so long, i tried to be pretty comprehensive
nah thats sweet, thanks for the info, anyone interested in a high comp head, theres 1 here, http://cgi.ebay.com.au/Daewoo-Lanos-Hig ... dZViewItem
but its fom aus so shipping would be imaginably large.
im gonna go with a turbo so its the complete opposite of what i need
but its fom aus so shipping would be imaginably large.
im gonna go with a turbo so its the complete opposite of what i need
car is coming along ever so slowly, gotta stop getting my funds of the government
Yeah the setup could be a bit on the edge if you are going turbo as well.
The cam is very lumpy. I remember seeing the DVE Challenge cars on TV and they had a very rough idle - reminded me almost of a rotary if you're into that sort of thing.
The high compression stuff is like turbo - its very effective but you need to worry about the fuel requirements/management.
--Tim
The cam is very lumpy. I remember seeing the DVE Challenge cars on TV and they had a very rough idle - reminded me almost of a rotary if you're into that sort of thing.
The high compression stuff is like turbo - its very effective but you need to worry about the fuel requirements/management.
--Tim