Conventional hot rod tricks good for FE?

[19bonestock88]

So, with the engine in my Malibu damaged, I am thinking about ways to boost efficiency of the engine during the process of a rebuild... The engine is of the Ecotec family of engines, in the 2.2 liter variation(the L61)... Now, there are lots of interchangeable parts used on other variants that work better than those used on the L61... With this, I have a couple questions relative to an eco engine build...

1. Building a hybrid... This is simply using mismatched short block and head combo for higher displacement and, at the same time, higher compression...
The stock 2.2 liter L61 runs 9.6-9.8:1 compression(depending on application), while the 2.4 liter LE5 runs 10.6:1 compression in most applications... The hybrid would consist of an LE5 block with an L61 head(eliminates the VVT that the car isn't programmed for), and he head would likely be ported while it is separate... Now, given the displacement increase, the compression could end up too high for pump fuel if the LE5 gained its compression while also using a bigger combustion chamber than the L61... More research needed there...

2. High flowing intake and exhaust manifolds... It's widely known (in the Ecotec community) that if you want more N/A power from an L61, you would change to a LE5 intake manifold(it flows better), and a header of some sort... Using this combo on an L61 will usually net gains of 10whp before tuning... Would higher flowing manifolds translate to better efficiency too?


Basically, my thought is to use a slightly larger engine, with a much improved volumetric efficiency, to move the car more efficiently than the current one does... The larger, more powerful engine could also support a taller final drive ratio(if it's possible to change it)

[oil pan 4]

Losing all the emissions control garbage that reduces fuel economy is one hot rod trick that increases fuel economy.
Also file fit rings and raise compression.

[19bonestock88]

Ditch the cats? Got it... There isn't a smog pump on my car, so that's not an issue, and EGR helps with mileage as far as I'm aware(correct me if I'm wrong)... I'm not sure how much the head could be milled for compression before cam timing becomes a problem... If I built from a bare block, I could order pistons as high as 12:1 compression, but finding fuel could be problematic... I don't really wanna spend $1-2k building this engine(think ROI) when a good shape LE5 long block could be had for ~$300 and I could get a free L61 head to work and build the LE61(hybrid) while I'm still driving my car...

Of course, the gained efficiency of running high compression(11:1) would have to offset the additional ~20% cost of running premium fuel that it would likely require...

[oil pan 4]

EGR appears to improve fuel mileage in most gasoline powered vehicles.
Catalytic converters on non-tubocharged gasoline engines that are working and not clogged up do not appear to hurt MPG.
My 489 cubic inch engine at the machine shop is going to have 11:1 compression and I am going to try to not run premium gas once I have everything sorted out. I am pretty sure these high compression engines can run and cruise down the highway just fine with regular gasoline. The problem is when you step on the gas, vacuum drops, filling the cylinders with air more, causing higher compression, more heat in the air fuel mixture.
There are 2 ways to prevent pre ignition. You can burn fuel that is more resistant to higher heat and pressure or you can try to cool the mixture off. There is a 3rd way to ward off detonation by having thinner air to start with. My thin air lowers adiabatic compression by about 2 full numbers. So an 11:1 engine at 4400 feet is more like a 9:1 compression engine at sea level.
Aside from the thin air I am going to try to cool the air fuel mixture down with water and methanol under part throttle and above.

Another dumb thing auto makers will do is run the idle ignition timing with little advance, that way more heat goes out the exhaust to the converter. You should be getting at least 20 degrees of advance at idle.

[19bonestock88]

Maybe there are some big gains in just my tune? I really wish there were somebody near me that uses HPTuners software...

What do you plan on using to activate your water/meth? On my Saturn, I plan to use a Hobbs switch at 10# boost, but win normal aspiration, I'm guessing that wouldn't be a possibility...

[Frank Lee]

Careful which hot rod tricks you choose.

Many hot rod mods are oriented towards maximum horsepower production. This means many mods are for the sole purpose of running higher than stock rpms. If you are wanting to save fuel, you won't go there. At all. That includes flow mods like "ditching the cat" which really doesn't help anyway.

Now, the mods that will help will be the ones that reduce parasitic losses and improve torque. Underdrive and/or eliminate power driven accessories, bump compression, and the like. Match the engine mods to the gearing and yes you won't be running a hot rod high final drive ratio either.

Build for the fuel you want to use. Here in the Midwest I could build a radically high compression engine and run it on E85 which is both high octane AND cheaper than regular. None of that premium fuel nonsense.

[19bonestock88]

Most of what I want, if I keep this car, is more torque for climbing the hills here in WV... Going to a 2.4 liter variant of its current engine would help, and I have read that the 2.4 used higher compression than the 2.2, which is another win... im a little concerned the higher compression might require higher octane fuel for optimal performance...

The higher flowing manifolds(both intake and exhaust) have been proven to gain power, but if it shifts power higher in the rev range, it won't help me at all...

[oil pan 4]

I was going to use vacuum and maybe throttle position.
I'm thinking 2 stage water methanol the vacuum switch kicks on the first stage and then use a proximity sensor or micro switch to turn on the second stage to dump water methanol into the secondaries when they start to open.

Water methanol isn't really going to help get better fuel economy aside from running cheap fuel. I think its only going to be needed at lower vacuum and WOT.

[SDMCF]

Originally Posted by Frank Lee

Build for the fuel you want to use. Here in the Midwest I could build a radically high compression engine and run it on E85 which is both high octane AND cheaper than regular. None of that premium fuel nonsense.

I have no experience of using E85 for economy but I am interested to know what savings you might expect from doing that. How would your MPG change?

The reason I ask is that I am involved with high compression engines using E85 in motor sport. These engines produce significantly more power but do use a lot more fuel. Economy is not an issue in this application but if it were the increased fuel usage would more than offset the lower price. If increased performance were not a requirement, would an engine using E85 consume more than a similar engine using regular petrol?

[Frank Lee]

Using E85 in stock non-flex fuel engines with stock compression ratios results in lower mpgs, in my experience usually about 20%. Supposedly much if not all of that deficiency can be recovered by raising compression ratio high enough to be optimized for E85, which means that engine won't run well on regular anymore.

I live in corn country and E85 is almost always cheaper than the lowest grade of regular, sometimes by quite a lot. If E85 is more than 20% cheaper than regular I can run it straight and break even vs filling with regular or maybe even come out ahead. Now, knowing that running a 50/50 blend of E85/regular nets virtually the same mpg as straight regular (in my State that's E10) anytime E85 is less than regular I save money running that blend.

To directly answer your question, I don't have direct knowledge of whether a high compression engine burning E85 can equal the BSFC of a stock compression ratio engine running regular. Perhaps because ethanol is oxygenated a somewhat leaner mix can be tolerated.