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AMC 258 w/4.0 head & EFI

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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcguru Quote  Post ReplyReply Direct Link To This Post Topic: AMC 258 w/4.0 head & EFI
    Posted: Jul/22/2011 at 8:58pm
Originally posted by farna farna wrote:

Some of the more streamlined cars don't hit that wall until 70-75 though. 
Very true.  My Benz has a .25 Cd and ambient temp/humidity plays a greater role in fuel economy than cruising speed.   The truck on the other hand is a whole different story...20.5mpg @ 65 and 17mpg @ 75.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tyrodtom Quote  Post ReplyReply Direct Link To This Post Posted: Jul/20/2011 at 9:18am
  Air resistance squares with speed.  Go twice as fast, resistance increases 4 times, 3 times as fast 9 times more resistance.
 
  Ever notice in the late 80 when NASCAR was still running somewhat stock appearing cars , with some aerodynamic improvements.   The cars had about 4 times the hp of the stock car but wasn't quite twice as fast, even at Taladega and Daytona.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/20/2011 at 9:02am
Are there any pull-a-part type yards in the are? Plenty of XJs in them now! If you find a Renix powered one the wiring is even pretty easy as the ECU/engine wiring is totally separate from the body wiring. The wiring is similar to the later H.O. engine, main changes are some of the sensor types. Shouldn't be too hard to convert a Renix harness to an H.O. ECU, but I haven't looked into that in detail.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jul/20/2011 at 8:53am
>>Seems like more people are complaining about gas prices, but many of the loudest complainers are also driving big vehicles at 75-80 and won't slow down.<<

Ain't it the truth!

I have done tests with my new truck.
55-60 I can do 22 mpg highway.
60-65, she drops 2 to 4 mpg with no other changes.
65-70, forget it, might as well be driving through KC during rush hour as far as mpg.
But if you can stand to be 2 minutes later when driving from here to Ankeny, keep it at 60-65 and you'll do very well.

OK, so that's a truck, right - brick through the wind........ but I've found it to be similar for many vehicles i've owned, including the javelin. When I can keep it under 80, it's a lot better for mpg.
The Javelin is hardly brick-shaped.

I do have to admit - if I could afford it, I'd be putting some form of fi on the 258 in the '80 Eagle wagon for my wife. She's been so long away from carb'd cars - it would just make sense.
She's not mechanical and gets frustrated if something doesn't start quickly and allow her to simply drive off. (frustrated is a nice word for the effect)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/20/2011 at 8:07am
I've heard 60-65 is about the limit for most cars and more modern light trucks that are a little more aerodynamic than in the 70s. Most of out AMC cars are about the same aerodynamically as 90s-00s light trucks. Just a bit better than pushing a brick through the air (I'm NOT including an XJ Cherokee as a bit more aero...).  The more frontal area the lower that speed. Some of the more streamlined cars don't hit that wall until 70-75 though. Seems like more people are complaining about gas prices, but many of the loudest complainers are also driving big vehicles at 75-80 and won't slow down.

Nali, I was referring more to a ready built system that a racer could use. You can assemble and piece together a Mega Squirt system for under $800.  The MSIII assembled with daughterboard for sequential injection and wiring harness (which still doesn't have connectors) is just over $700. Then you need a laptop. I should have specified when I mentioned MS though -- I was considering the premium system, not the basic. An assembled MS1 unit with everything you need still runs around $500. The Micro Squirt would be the base level of EFI, and can be used on cars though it was designed for smaller engines. You're still looking at $400 (+connectors). The Micro and MSI are both batch injection with two injector drivers.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote poormansMACHINE Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2011 at 3:35pm
Double the speed and resistance goes up by a factor of 4. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2011 at 3:09pm
70 mph ain't gonna get you MPG in any case........... you drop off seriously above about 60 or so, no matter how much you tweak, EFI or carb.
The smaller the engine, the bigger the drop in many cases.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nali Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2011 at 2:14pm
Farna , a Megasquirt doesn t cost 800 $ ... The controller is about 260 $ .
For this price , assembly is required , of course :P
http://www.diyautotune.com/catalog/megasquirt-ii-kits-c-30.html?osCsid=a9b390422824ef8a7fdf45beff572c4c


Edited by nali - Jul/19/2011 at 2:14pm
No more car :)
Maybe a 1965 Ambassador Coupé someday .. If I can find a cheap one.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2011 at 1:59pm
EFI is expensive for drag racing. The guys with big bucks ARE running EFI with computers. Instead of breaking out the jets and screw drivers they pop open a laptop. For an easily adjustable EFI system you have to start with at least $800 (Megasquirt), but that only gets you a controller and wiring. You have to come up with sensors and half the wiring harness. Figure more like $1200. I'm not sure the MS system is all that great for racing, but then I don't see why not. Carbs are way cheaper and easier to learn than an EFI system for most.

Most people (self included!) simply don't know HOW to set carbs up right. But I say even then they are only "right" within a certain set of parameters. They simply can't adjust for as great a driving condition range as EFI.

I think we are all describing our "worst scenario" conditions. My truck didn't act up all the time, only on the colder days. Most other times it ran fine... except when the secondary float stuck, TWICE... mainly because the poor old thing hardly ever pulled in the secondaries. I don't think it was creating enough vacuum due to worn rings. I had a screw in the slot so at 3/4 throttle it would crack open the secondaries anyway.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 7Xpacemaker Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2011 at 1:58pm

TWO new cars were taken to my friends Chevrolet dealership in northwestern Pennsylvania because one would barely run and the other would not run at all. Long story short- the gas was drained out and a sample was sent out from each vehicle. It turned out that there was 21% ethanol in the gasoline. You can take or leave my information or call it "hearsay", it matters not to me. No matter what I say it is all hearsay to anyone else. I have also gotten good mileage from carb'd vehicles as well. My daily driver (84 miles per day) was an '81 Concord/ auto with a two bbl carter. The best I could get out of it was 22 mpg at 70 mph. I had the car tweaked as close to stoich as I could without detonation. I am an aircraft mechanic by trade and definately have the skills to properly set up a carb. My intention when adding to this thread was not to stir up other people's emotions. I apologize if I have. I sometimes come across wrong, I guess.Disapprove

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