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Discussion Starter #1
Hey all, I am thinking about building an engine in a bit,

on a budget, not looking for any real serious power, more looking to maximize efficiency and mpgs.

Since compression is good for all that. I was thinking of getting a set of used or new depending on price mark/conti pistons (flat tops) and swapping to pi heads/cams/intake.

That should put me around i think 12.4ish :1, can i run this on 93 octane fuel safely, or do i need to consider using water/meth as well?

With a set of ported stock exhaust manifolds, true duals, larger throttle body, and a tune...

how much hp would i expect to make?
 

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My guess would be somewhere around 235 RWHP, give or take half a dozen HP. A larger TB isn't necessary at that point BTW. I don't see why you couldn't run 93 at 12.4:1 as long as it's tuned well.
 

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Discussion Starter #4
i understand the premise of parasitic losses,

but i know so little about the pumping losses.... I hear that increased EGR flow helps with that? Also lugging the engine low rps with more throttle position can help too?
 

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i understand the premise of parasitic losses,

but i know so little about the pumping losses.... I hear that increased EGR flow helps with that? Also lugging the engine low rps with more throttle position can help too?
yes EGR accomplishes just that. The problem with lugging the engine at low RPMs is that there is less torque there, so it becomes a very delicate balancing act. Frictional losses are cut dramatically the lower the RPMs are, but that doesn't mean that the necessary torque production is gonna be there just because you want it to be. More throttle position comes from using EGR It all becomes one big ol' balancing act of torque production (which alone encompasses many many factors), EGR, and throttle. In the end it boils down to minimizing the mass airflow rate for a given speed (because this minimizes fuel consumption for a given lambda), but that simple base premise is the same thing it takes teams of engineers to accomplish the tiny improvements in fuel economy for the car makers.


easy things to do (internal engine work) would be to ceramic coat the combustion chambers/valve faces, piston tops, and exhaust manifolds. You can also get custom pistons made to maximize quench action with the "quench pad" on the PI cylinder head, yet still keep compression in check to use 93 octane. This is pretty much guaranteed increased torque production.

This, and tune aside, next step would be cut parasitic losses outside the engine. Underdrive everything, electric water pump, ceramic ball bearings on on the idler/tensioner pulleys. Then you can take it ten notches further and custom make yourself some super long-tubes with 1.5" primaries, 38" lengths, tapered 2.25" collectors, and some megaphones and/or MAC-style Pro-chamber.....


-----wait, [most] all this is exactly what I'm doing! Wonder why? ;)
 

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Discussion Starter #6
I have either read somewhere, or its an arbitrary number i have in my head, that the max egr flow in our eec's is "12" is this true? I have set my egr flow table to more or less all 12's

and as far as torque production goes that i need, I am quite able to pull up a hill in 4th with the converter locked ~1200 rpms AND accelerate with enough throttle to not unlock the converter :D LOVE v8's
 

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Be careful with EGR - too much low RPM can create a misfire. As far as max, the PCM can command a certain amount, but you'll only achieve as much as can be created through the size of the pipe through which the gases flow.

Finding the optimal shift/lockup schedule takes a lot of logging/time. I spent most of last year working on it - and I'm still not 100% satisfied... :D
 

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Yea the more EGR could indeed cause a misfire, but more compression together with good squish from the quench action may be able to put it in check by allowing the flame front to propagate more evenly. Ceramic coating would help this even further. The higher compression will put the oxygen/fuel molecules closer together within the diluted, inert exhaust gases; hopefully it can prevent misfires with higher EGR flow.
 

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I would be very weary of doing 12.5-1 compression on 93 octane. It's too much to achieve maximum timing which I'm pretty sure you want for maximum power.

My motor was 12.8 to 1 and on 93 it would ping. Even with way low timing and comp 270 cams. I would do more like 11.5 to 1.

If your goal is only gas mileage and slightly better performance, shave the heads a little, do PI cams, and PI intake. Do underdrives and decent exhaust and save the rest. No mod is going to be worth it MPG wise when you consider your investment.

I did some experiments with fuel economy and found a couple more MPG but that included major weight loss, PS delete, and Electric water pump.

Like the others have said, there is a couple MPG in the tune if you have the pro racer package.
 

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Discussion Starter #10
Ya I have found about 1mpg in my tune already, I am using a Tweecer setup, I have changed the torque converter lockup some, egr and some other various things, but those two items probably have helped the most.

My major mpg issue is the driver's (read me) big fat right foot :D
 
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