Improving Engine Efficiency & Performance

[IanSzgatti]

to help the 3x00 you need to increase VE....thats about all you can do with the engine untill you start getting into areas that would require extreme modifications.

I just wanted to say that threads like this are awsome because they are a pool of knowledge all brought together by each member, and it enlightens and educates. It always impresses me; the amount of knowledge in theory some of you have.

To keep in line with the topic, I agree with the statement I quoted. Since the 3400 is a conventional "air pump", then the ease of which it performs has a lot to do with the pumping of the air. Now my little story...

Before I did my exhaust, I would cruise at around 70 km/hr until OD kicked in. Once it did, I would try to maintain that low rpm/low vac condition throughout cruising. When coming to gentle rises, the car would downshift with the slightest increase in throttle.
Now that I have changed the muffler and added a short high-flow "performance" catalytic converter, I can take the same gentle rises and maintain that low rpm while slightly increasing throttle pressure.
I suppose a little higher rpm would produce more power, thereby reducing pulse width or something, but then your still getting more rpms anyways... so i'm not sure which is more benificial. I am out of things to say that make me appear to know what i'm talking about, so I will stop at this point.

[IsaacHayes]

Yep many things that improve performance can also improve mpg since it's more efficient. Now somethings like a really hot cam can hurt MPG. I wonder how much mpg headers are worth?

[Rhedalert]

Headers are known for a couple extra MPG's in the F-bodies (after tuning) and the LS1 already has decent flowing stock exh manifolds.

Nice catch on the 3500 vs 3400 VE! I haven't been able to find 3500 bin files to check that out.

[torq455]

in a v8 with tuning. sure. the problem with comparing an engine with 2 more cylinders and more cubic inches per cylinder is whatever effect happens on it, the lesser engine will have a lesser effect. they say a K&N filter adds up to 15 HP on a 454. well, on a 305, it might be more like 8. then our 3x00's, maybe 3?

i was hoping for more mileage with my headers, but didn't see any gain. though, with my FDR of 3.05, at 65 MPH i turn ~1950 RPM. light throttle at that rpm won't need a high flowing exhaust.

[IanSzgatti]

light throttle at that rpm won't need a high flowing exhaust.

but i'll bet it's good when you pound on the pedal like a red-headed step-brother

[Bones]

A high flowing exhaust isn't nessesarily important but a low-backpressure exhaust is because any extra pressure pushing down on the piston during the exhaust stroke robs power from the flywheel. Likewise a header that scavenges the cylinder well at cruising RPM will create a small vacuum in the cylinder which helps accelerate the intake into the cylinder so that less power is lost filling the cylinder. Of course if it scavenges too well or the camshafts overlap period is long some of the intake charge can be sucked right out the exhaust port, which is good for horsepower, but it obviously doesn't help fuel econemy.

I'd say that less exhaust gasses left in the cylinder also means that the intake charge is less poluted. This could mean less ignition timing may be required, or it might allow the EGR system function better by reducing intake vacuum more. It gets a bit complicated to work out all the variables and figure out what works best at this point, would probably take a bit of experimenting with the tuning to figure that out but regardless I think reduing back pressure would help econemy.

that's my $.02
-Mike

[Rhedalert]

in a v8 with tuning. sure. the problem with comparing an engine with 2 more cylinders and more cubic inches per cylinder is whatever effect happens on it, the lesser engine will have a lesser effect. they say a K&N filter adds up to 15 HP on a 454. well, on a 305, it might be more like 8. then our 3x00's, maybe 3?

i was hoping for more mileage with my headers, but didn't see any gain. though, with my FDR of 3.05, at 65 MPH i turn ~1950 RPM. light throttle at that rpm won't need a high flowing exhaust.

What do you average on the highway for fuel economy?

[torq455]

31 mpg