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Discussion Starter · #1 ·
Is it the 1.8 rods with the 2.0 pistons that raise compression, or is it the 2.0 rods with the 1.8 pistons that raise the compression.

I heard that higher compression engines run more efficiently if there is adequate cooling and I was just wondering what it would take.

Here in cali we have **** for gas 91 octane rating, do you think it would be safe to run an 11.5:1 CR or somewhere in the ballpark with 91 octane?

If the piston/rod combo raises it to 11:1 shouldn't shaving a bit off the head achieve closer to an 11.5:1 without clearance issues?

I have read that on a stock engine at 11:1 it should net around 4-5 horses, but with it somewhere around 11.5:1 and a cleaned up mildly ported head and some odds and ends, shouldn't it achieve around 15-25 horses with a pretty mild tune?

Odds and ends are like ported throttle body and port matched intake manifold.

Just throwing this out there, because I am just wondering why people rarely point out the efficiency increase and better fuel economy provided by a higher compression motor.

Been thinking about it, and everything should cost a little over a grand.

I need the fuel economy, but I also want more power.

Would it be worth it to run a good sized turbo with the stock compression to retain fuel economy and gain power. Maybe get a turbo with an assload of lag, like an old 1990's HKS turbo or something so you will be out of boost until like 4000 rpm.

A lot of guys seem to have problems rigging up their turbo setups and they seem to cost more than anticipated for them, so I thought that this NA setup should be more predictable and easier.

I've looked around and have searched a lot on the forum, and I just needed some clarification on some things.

· lag, lag, lag, bye.
1,312 Posts
So you're asking if you should spend a thousand dollars or more to gain a few hp and slightly increase fuel economy? I say don't bother. I'm not sure about n/a builds as I never cared enough to look into them, but 11.5:1 sounds like about the limit you would wanna go to keep the car streetable on pisswater 91. I don't think the work involved, as well as the extra money per gallon for 91 will weigh out the MPG increase. As for boost... If it's not hitting boost until 4K+ on a 2.0L, chances are it's a big boy which will flow enough lbs/min to blow the stock bottom end to all hell. Contrary to popular belief, turbo makes the engine a whole lot less fuel efficient. Yeah on paper it helps when out of boost, but in real life situations when the boost bug bites (and believe me... it WILL bite) you will be going through fuel (91+ as well!).

· Registered
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Discussion Starter · #4 ·
alright, thanks for your input killer.

So in that case, if he is correct, then 1.8 rods with 2.0 pistons should raise the compression safely. I have read that the 2.0 pistons are of a better design and should not retain the heat as much as the 1.8's.

I see what you mean by that, but an na build shouldn't be too hard if I do the work myself. Already build a b18a1 and that was a cake walk, and I have heard that once you've seen one you have seen them all.

I'm talking 1 grand in parts and machine work. 91 about 10-20 cents more per gallon around where I live, and seems like a waste. I could get 100 octane but that would cost an *** load and my fuel econ would go to ****.

Yeah, I have just been looking around at viable options to maintain power to economy, and it seems like using an outdated large turbo with the mbc set around to 7 psi should be my best bet. I am wondering what lower compression around the low 8's would give me in terms of fuel economy...

Or since I am waiting to crack my engine open till 200k miles I could save for another car as a DD and collect parts for the elantra. Maybe use the 1.8 pistons and rods to get a healthy 7.8:1 CR and then use a metal head gasket to lower it to down around 7.2:1 then have a large turbo set to around 25 psi.

It seems the lower the CR the less knock you will get on lower octane fuels.
Problem with that setup would be that I would have prius like power until boost kicks in and the fuel economy of a muscle car.
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