bp944

iTrader: (4)

I am curious as to how one would port a head for MPG and if anyone has done something like this before. I think, if done right, a head could really improve MPG and power. I mean, it is essentially making it more efficient, right? I'm assuming one would begin with a high velocity flowing head like 205. It would need to be a high compression and a great airflow for atomization. It would be going on a ls1 block with standard stroke and bore. Please correct me if I'm wrong on this, I am by no means knowledgeable about porting heads.

Reher Morrison

The factory heads are a perfect example of what should be done for fuel economy. They have a very high speed throat and short side area for throttle response and fuel atomization at part throttle yet just enough port volume to still make peak power all the way up at 6000 rpm. I am not saying they cant be improved upon with time and money, they can. Just not a whole lot if MPG is your primary goal. So, you have the heads for the task what else can you do?


(1) KEEP YOUR FOOT OUT OF THE THROTTLE! Sorry to yell like that, just trying to make a significant point. My point is, keep the engine out of power enrichment and you will have fabulous fuel mileage.

(2) Design a camshaft with no overlap and moderately high valve speeds to reduce seat timing (low duration) Oh wait, that’s what the stock cam does!

(3) Run the engine slightly leaner than Stioc. I am not saying to run an engine with a fuel stioc of 14.67:1 at 15.5:1 that would not be good. Just run it at 14.9:1.

Those are really the only things you can do if MPG is your primary goal. Just don't plan on making a lot of power if this is your goal because powerful modified engines with high overlap cams and fully ported heads will get significantly less MPG than a stock engine which, is designed for moderately high HP with high MPG. I am not saying you cant gain some power and maintain MPG or have slightly less, all systems can be optimize with time and money. Its just a whole lot harder to get more MPG and make more power at the same time. in order to make more and more power you have to raise peak VE higher and higher in the power curve which kills low speed driveability and consequently MPG because your driving an engine around that's "out of tune" 90% of the time. The only time its in tune is when your laying into it and its up around 3500+rpm.

Reher Morrison

I want to make a secondary point here. The factory engineers have to work within stringent regulation as far as exhaust gasses, noise restrictions and a plethora of other tight rules they have to work with. We however do not! We can take the factory vehicle and if we want, increase MPG by increasing exhaust efficiency (headers and large diameter exhaust) along with increased noise levels (less restrictive mufflers). So in effect we can increase power slightly while maintaining MPG with the two things that allow us to do so. Time and money. Of course don't forget the intellect of the person performing the task. That counts a great deal!

bp944

iTrader: (4)

Can you give me a ballpark of what you define as a lot of power. Will I start seeing huge mpg downfalls at 400hp, 500hp, 900hp? I know it does depend on the setup. Lets say I'm bumping compression as high as I can on 91 octane and have a very free flowing exhaust and intake. The intake will be a ram air straight from the front.

Reher Morrison

A ballpark guess is all I can give you. I have never tried to do what your attempting. I wish I could whip up a Specific recipe but when moding a car I have always went from stock strait to 500+rwhp. If I was to try what your attempting to do I would do the following.

(1) 228 232 .600 .600 116lsa in 6 advanced (don't now if this grind actually exists its just hypothetical)
(2) Ported heads specifically for your combination.
(3) Smaller 1 1/2 headers with long primary's and merge collector with cross over.

This is simply my hypothetical combination for increased MPG and increased power and has never been proven. How much power and MPG it will make is any ones guess. Maybe someone on this forum who has developed this kind of combination will post.

anheuserbusch08

iTrader: (11)

u want mpg get a prius or a metro lmao

speedtigger

iTrader: (16)

Compression, cam timing and a incredibly fine tuned fuel injection and going to be your biggest contributors per a given displacement.

427zm

iTrader: (9)

Now this is a thread with some serious intellect going on!

bp944

iTrader: (4)

Can you explain your choice in exhaust? Why a smaller set rather than a really wide headers?

As for tuning, I will be running a custom mega squirt setup with 8 o2 sensors so I can get the leanest burn from each cylinder. It will also allow me to control a/f ratio for specific rpm's. I know this is very possible but I need to get the exact details figured out. I am also looking into a setup to kill the injectors while decreasing speed. I know the easy way is to mount a kill switch but I want to see if I can program it.

For compression, I will be running 91 octane so what would be static compression be? Is that something I should be desciding after a cam is chosen? On that track, who would do a custom cam grind like you mentioned and why did you pick those specs?

bp944

iTrader: (4)

Oh, if I'm running a lean burn, do I need to look into aftermarket sodium valves so the valves don't burn?

mark21742

I've run a cruise a/f ratio at 17+:1, but drop to 12.8-13:1 as soon as throttle is tipped in with no problem on stock valves.

Also another option would be to setup a large and very aggressive eve type system so you would be pulling in a lot less fresh air and in turn need a lot less fuel to keep a safe a/f ratio.

My fathers 98 318 dodge ram got a good solid 10 mpg. I ported the heads and intake, then dropped in a 360 with these heads and intake, opened up the throttle body and now pulling a solid 16 mpg with a lot more power over stock.

bp944

iTrader: (4)

eve type system?

mark21742

Sorry....typo lol EGR system either I typed it wrong or auto correct got me.

A.R. Shale Targa

iTrader: (2)

My Vette gets pretty decent mileage at 30-33 freeway by having a 6 speed
and 3.42 gears....as well as keeping my foot outta' it. Only deviations from
stock are a tiny EPS 218/226 cam, pocket polished and milled .030" 241 heads
for 10.75 ish compression, and XS Power 1.75" long tube headers w/3" X-pipe
and hi-flo cats. Corsa cat back was on the car when I bought it. Besides
the bowl work on the heads I ground off the IN. rocker boss and gasket
matched the exhaust port as well as streamlined the EX guide area...so while
my intake only flowed 12 cfm more than stock @ 246 (factory valve job); the
exhaust picked up a bunch to 200 cfm @ .600" lift (220 flowed w/pipe). So I'm
thinking the keys to my combo are a really efficient exhaust mixed with a wide
lobe separation cam to capture as much of the ellevated compression as
possible.

Ari G

iTrader: (25)

I saw you other thread and like what you are thinking about,im playing with simmilar concept engine/car

You would want to max the stroke out
Low octane fuel with as much compression as it can handle
As short of a rod as possible for max pressure duration on piston
Small Rings .043 and 2mm oil rings that will cut the friction down and increase efficiency but still be usable for many miles
Scavange pump or what i like free scavange from exhaust E-vac to collectors

For the heads,valvejob is very important as a steeper 50deg will help with reversion plus the throat aeria and shape the bowl and short turn to even out the velocity over the whole valve keeping the port at full efficiency

roadracer380

Megasquirt and all factory ecm's do this for you. Megasquirt calls it "Overrun" GM calls it DFCO ( deceleration fuel cut off)

01 ss vert

iTrader: (1)

Tuning for part throttle is a must.