MG Sports Cars

Curtis' response to Paul's gas tank question got me wondering so I checked my mileage. I should be getting better than 15 MPG, shouldn't I (14.9 to be precise)? 50/50 mix of highway and around town driving so I wasn't expecting Kelly's 27, but I expected something in the low 20's. Clearly something is off. Rear end gear is 3.54 so highway driving is only about 2200 rpm at 70. Gas here is 10% ethanol and I've been running premium (93) or I get run on (timing off?).

1st thing I guess I need to do is double check my speedo calibration, but I did calibrate it after Palestine and it was tracking to the GPS app on my phone so should be accurate.

Also, Curtis, where did you get the 18 gallon number for Todd's gas tanks? I consistently get right about 15.5 gallons from empty including whatever is in the filler pipe that leads up to my gas cap up between the right rear fender bead and wheel well. If the tank is 18 gallons I need to adjust the sender or check with Todd to find out what sender he used - I might need to swap in one that better matches the range my Autometer gauge expects.



Edited 1 time(s). Last edit at 11/19/2012 08:39AM by rficalora.

Rob,

I believe the number that Curtis is using came from Todd. Here's a link to what Todd said about the volume on the MGE http://www.mgexperience.net/phorum/read.php?40,747959,748271#msg-74827

FWIW, I average 23.5 to 24 MPG (US) at highway speeds of 70-75mph.
Interesting to note that at 70mph I'm also turning 2192rpm (calculated) with a 3.27 RA ratio and 225/50-15 tires....that means, for your 3.54 ratio, you must be running larger dia tires.

RE: the tank capacity -- interesting - I'm definitely only putting in 15.5 in on a empty to full fill-up so maybe my fuel sender doesn't go all the way to the bottom? Will have to check it. At least I shouldn't have to worry about running out ;).

RE: RPM's - Graham, assuming that's 5th gear, what's your overdrive ratio? My diff is supposed to be a 3.54. I just did a quick internet search & doesn't look like the R200S diff has a gear in the 3.3 range (R180 does). But, my rear tires are 225/50/15's unless the overdrive ratio would account for the difference (& I've not done any calcs), maybe my speedo is off & I'm not really going 70?

Rob,

Ya gotta keep yer foot out of it if you want great mpg. ;) Kelly's car is a well-tuned fuel injected 302 cammed for best mid-range power. Some of these 302s are running pretty healthy cams that just don't get as good gas mileage.

Rob, my 5th gear ratio is 0.68 but I suppose the 0.63 is available if you have the T5Z option.

Quote:

Ya gotta keep yer foot out of it if you want great mpg. ;) Kelly's car is a well-tuned fuel injected 302 cammed for best mid-range power. Some of these 302s are running pretty healthy cams that just don't get as good gas mileage.

The only time I checked my mileage, I got 25-26 at 70-80 MPH on its maiden voyage from Michigan to Tennessee. I don't know how much I get locally, nor do I want to know. If I knew what it cost me, it might inhibit my right foot. This is a case where ignorance truly is bliss.

An EFI engine, managed by an OEM computer and under light throttle (steady cruising speed), should get better mileage than a comparable carburated engine. In your case Rob, I would invest in a good quality wide band A/F ratio meter; that way, you should be able to monitor an overly rich mixture at different R.P.M. A rich mixture across the board will cost you big fuel mileage. Of course as mentioned above, low gearing can also deliver poor mileage even with the best tuned engines.

A/F meter is on my Christmas list. It looked good @ WOT on the dyno runs, but I don't know what it is doing @ other times. I don't think I'll get a chance to pull the plugs till Sunday but plan to do that as well as check to be sure my timing hasn't moved. I'm also going to check the distributor mechanical advance. It's from a '85 5.0L manual trans Mustang so I'm guessing the advance curve is OK, but don't recall verifying when I installed it. I know EFI will yield better mileage, but I was thinking 2-3MPG vs 25-30%. I'm not as concerned about fuel cost as I am thinking 15 MPG is telling me I have more tuning to do than I realized. Plus, if 15 is the best I can do with the carb and both Kelly and Dan are in the mid to high 20's, I might be able to justify FI to my accountant* sooner than I thought.

*today's our 18th anniversary by the way and she's now officially an author. We got the first copies of the book she wrote last week and had a friends and family book signing party this past weekend.

Rob, congratulations on your wifes' book! What is the title and what is the book about?

I'll chance a guess..."My Husbands' Rusty Addiction" ? At least with soda blasting, we have a cure ? Cheers, roverman.

LOL & that might be her next book!! Actually it's a Christian women's book called "20/20 Christian in a 20/40 World" -- my wife fought glasses & readers for many years & uses analogies from that through out the book.

Congratulations Rob, I supposed it calls for a celebration for the both of you.......

Cheers!

Where can we buy a signed copy?

PJ - thanks for the interest. Since a couple of people have asked, I'll put some info in the Pub section.