I read a post somewhere that said there was a guy who has a 500HP daily driver that gets 20MPG. I'm guessing he has a 6 speed in order to do that. Looking at 350-400HP whats the best gas milage you can try and aim for when going 4BBL? Are there are "proven" combos that not only build HP but MPG? What is "acceptable"..I would think 15MPG would be the absolute minimum....any info?

 

400RWHP(500FW) and 21MPG on the hiway with a Yank 3,800 Stall and 3.73s

 

This would be more proper in a gen spacific forum. Moving to 3rd Gen.

Thanks.

 

Yea, it's called a 98+ LS1 F-body.

 

One of my friends is in the 12's and is getting great (over 25 mpg) milage. He is running FI but still that to me is a sweet thing. He has a 355 with TW heads, LT4 hotcam kit, ported TPI with 30# injectors (not 100% sure on that one). He was running an auto but now is onto a 6 spd so he might be getting better MPG and he also switched to SD from MAF so his tuning is much better. He is also running 3.23 gears in the back. He has 3.73s on the way. That is a really mean car.

 

I mean, I'd say mostly it's possible, I don't know how these people are getting 25mpg, because that would indicate that they may have an aftermarket ECU that is programmable, like Anaccel to run mixtures that produce good mileage off the track and also has enough to supply the motor while racing, my car gets around 15mpg and runs 12.2s on slicks, of course if you race a lot, the lower mileage you will get, but during normal driving it should be farely easy to meet that ratio.

 

if youre talkin 4BBl, i think itd be pretty hard to get 20mpg but still have some fun with that car. we could all get 20mpg if we drove around in 5th gear lol. if you were to bore the motor...would that take more gas? wouldnt the cam only open the valves enough to still only let in X amount of air/fuel? then youve got more BOOM area thus more power. and you are talkin N/A right b/c theres always the bottle...

 

I can't see it on a 3rd gen. I get about 16MPG city and highway driving. That is babying it all so. That is with a 700R4 and 373 gears. I only got about 18 miles per gallon when the car was new and stock.

 

It is there buddy. You are really fighting old school tech with a carb, but it is still there. I will be dumping over 700 at the wheels out of a 355, and as long as I stay out of the boost, I will cut the same gas mileage as a stock LT1. It really is all in the combo.
If you havge a 396 carbed motor going through a four speed and a 4:10 rear the you can expect 5: miles per gallon. But if you build a 350 or 355 running boost such as mine, as long as you keep the injectors from turning in to sprinklers, and you have a good over drive tranny, you can easily cut some wicked gas mileage.
It really does not have to go as extreme as my set up, all you have to do is build a good N/A combo that will respond well to a power adder, whether it be nitrous, or charger.
I personaly built the strongest possible bottom end at 7.5:1 compression. then hit it with 15# of intercooled boost, and made 720RWHP. Then I added a 150 horse TNT wet kit and put 890 to the ground. The thing is that as long as the switch is off, and the car is cruising at 1400 rpm in sixth I can drive anywere in Canada with out worry about blown engines, and horrible gas mileage.
The technology is there, you just have to use it.

Martin

 

the guy the original poster was refering to had a small roots blower and holley commander 950 injection.

it can be done with alot of tuning.

 

It's all the your induction and your cam. Well, that and how much you get into it.

It think it would be pretty easy to get that amount. Especially if using nitrous is involved, since it won't be there all the time.

Blownyellow sounds correct to me. Friend of mine has a 400 with 22lbs of intercooled boost and was running 150 shot as well. Although when on it, his mileage is horrible, but when off of it, it's pretty good.

It's all about how you manage your car while driving, your induction (carb/FI) and your cam has alot to do with it.

 

High HP, carbs and good MPG don't usually go together, your best bet would be to shoot for about 350 HP + 150 shot of NOS, then use Vortec type heads with a dual-plane intake and a well tuned Q-jet with a manual trans with a deep overdrive like a T-56, with RPM's of less than 1500@60MPH, or fork out the cash for a modern programmable EFI set up.

 

I was just wondering if there was a way to make an "efficient" engine. Meaning, when you are in WOT it makes alot of power, but is ALSO build in a way that it can cruise around as a daily driver. If you only need "X" amount of power, then you use "Y" amount of fuel. Thus if your just driving around your using less fuel. Why must more HP mean worse MPG.....your not driving around USING 400HP, so why should your engine be feeding it more fuel....someone want to try to explain this to me. Does anyone understand how my brain is trying to reason this? Sure, your PEAK HP occurs at "Z" using "Y"' amount of fuel. Your not driving at peak HP all the time, so why must you use more fuel then ANY other car driving around the same way you are? Get me.....two cars, one with 500HP, one with 200HP, when at WOT car 1 is pouring X amount of fuel to accelerate, eating gas. Car 2 is pouring X amount of fuel to accerlater, much less because the engine simply doesn't make power and can't process any more. But at cruise why should either car use more fuel, shouldn't a higher HP engine get BETTER MPG when not at WOT, because it's built better that it can make power easier. I mean, 200HP or 400HP, when BOTH are making 100HP shouldn't they BOTH be using the same amount of fuel, so if your car is making 135HP (im just making up numbers) to cruise at 45MPH, shouldn't ALL engines use the same amount of fuel to make 135HP to cruise, but simply a better build engine can flow air, and combust more fuel when at WOT to create more power. I'm sure torque comes in somewhere, and I must sound like an idiot trying to "reason" it out like this.

 

Yea, it makes sense. If it's making more power with the same ci, then it outa be more efficient. But when ya got the power, ya usually use it, having fun with it, so it doesn't do better, LOL. But if you were easy on the throttle, it should be.

 

To answer StealthElephant, excluding rear gear ratio's and slipping high-stall converters the reason high HP engines get such crappy mileage when just cruising around has to do mostly with the cam, the big cam needed to make the high RPM power are very inefficient at low RPM due to lots of overlap when both valves are open at the same time, the carb gets a poor vacuum signal and has a hard time metering the correct amount of fuel, it usually dumps in too much. Plus the engine makes so little power at low RPM that you have to use more throttle to go a certain speed. Using a programmable type EFI system you can get much better MPG by having total control of fuel and spark curves, you can force the engine to only use so much fuel at low cruising RPM, and you can have presets that have either maximum mileage or maximum HP at the touch of a few computer keys.