Motorgen - Automotive Events, Meets, Cruises and Forums - Time For The Cobra To Get A New Engine

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I have a hard time understanding how what you've done would increase mpg 30% @70mph.

Quote:

Originally Posted by 94cobra69ss396 (Post 117983)

I knew that I could use the fox TB to install one and that I would lose my cruise control but I don't want to do that. I drive this car to northern CA and AZ to customers and really don't want to lose the cruise control. I'll be using methanol.

Speaking of long trips, back a few years ago we had a thread about MPG on boosted engines related to vacuum. I did some mileage tests in the Cobra and found that with the old engine combo that I got the best MPG at 60 mph which was 28 something. Yesterday when I left for your shop I filled the Cobra up near my house and reset the trip odometer. When I got home I filled up again to see what kind of mileage I got. I drove 70 the whole way to the shop and mostly 70 on the way home except where I ran into a little traffic that slowed to 60 for a couple miles. I was amazed to see that I pulled 30.235 MPG. I knew it was getting better mileage but I didn't expect that. Before I would get about 23 MPG at 70.

Is it possible that the stations fuel pump might be the reason I think it's averaged so much? The reason I ask is that when I filled up the first time I used a different station than I did when I the second time. The way I filled up the first time was I set the handle to pump at the slowest rate and let it click off by itself. I did the same thing the second time but it clicked off after just .6 gallons. I knew that wasn't correct because I had driven 52 miles. So I started the pump again but it clicked off right away. So the third time I held the handle by hand as slow as I could go and it clicked off at 1.72 gallons. Is it possible that the pumps at the second station are just more sensitive to the overflow?

Not sure if you had the T56 or not but that's a big part. Your new chip allows for much better tuning capability. Longer stroke helps alot too, along with the porting of everything, new cam with the 114 LSA and increased cylinder pressure. Makes sense.

Quote:

Originally Posted by 94cobra69ss396 (Post 117983)

Where were you when I was arguing mpg with Sean Plunk years ago? Mpg relates to vacuum, simple.

Ya something is off, youre not getting 30mpg with a blown V8.

When I fill up my moms SRT, sometimes the handle clicks off before its full. It depends on the angle and temp when the fill tube will touch fuel.

You mean this one? http://www.motorgen.com/forum/showthread.php?t=522

See page 7.

I drove the same 52 miles today but this time I was in stop and go traffic on the 26 mile return. I also had 4 full throttle blasts up to about 80 moving into traffic and the gas gauge moved a lot more today. I didn't fill up the tank to check it but I'm going to North Hollywood tomorrow so maybe I'll fill up after that and see what kind of millage I get in normal driving. The real test will be at the end of next month when I have to drive up to San Francisco. Then I'll have some good long miles to compare with. On that trip I normally get about 22-23 miles per gallon.

The new LT1 gets about 30mpg on the freeway in the new C7 (using the EPA's current test circuits). It's lighter,has better aero, is direct injection, naturally aspirated, and shuts off half the damn engine at freeway cruise. I have heard of some guy getting up around 30mpg in stock C5s with a T56 and idealized driving/engine conditions.

If you want a solid idea, do a few phoenix loops and use a clock for trip average speed. With longer trips and if you're meticulous about where and how you fuel, the margin of error should be pretty small. Deep into the the 20s doesn't surprise me but I'm skeptical about 30.

Quote:

Originally Posted by Vettezuki (Post 118030)

Last trip to Vegas I got 26 mpg doing 80 all the way. And that in a car that is 3,850 pounds. I can get about 29 if i keep it around 60.

I had to drive up to San Rafael this week for business. The 30 mpg must have been something with the pump not filling the tank all the way or something because I average 22.501 mpg driving between 75-77. That's still better than it got before by about .5 mpg. It's not huge but at least I'm getting better mpg while making more power.

I got about 26 in the vette with the old motor between SD and Phoenix at 90 mph. I would get 28 if I slowed to 60 mph.

Quote:

Originally Posted by 94cobra69ss396 (Post 120029)

That's pretty fantastic. I've been daily driving the Vette these past few weeks, and with my 6th gear my freeway mileage is relatively incredible. It has to be at least double my city mileage. The motor is sitting at about 1,500 rpm on the freeway, but my cam is way too big to shift down low like that. So in the city I need to rev it up to about 2,500.

Well the Cobra failed it's smog test but just barely. I have a Magnaflow 2 cat H-pipe and I tested the cats after. The outlet is only about 100 degrees hotter than the inlet so it needs cats. I checked with a local exhaust shop about just adding the front cats to make it a 4 cat H-pipe like stock but they wanted about $400. I looked online and I can get a new Magnaflow 4 cat H-pipe for a little over $500. I've been waiting for Autozone to have a discount which finally they have a 20% discount code so I order it from them and saved about $130 with the free shipping. Hopefully this will make it pass.