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Posted by: draperjojo Sep 24 2006, 05:51 PM

Yeah, it was looking a little grim at first for the draperjojo mobile. I'd like to thank McMark, Andy, and Jeff and everyone else that helped out on Saturday morning. I feel pretty fortunate to have had an engine problem with so many experts readily available. Luckily it wasn't a dropped valve seat, but a loose adjuster and locknut that managed to stay in the valve cover for the 35 miles down the hill to Moab.

By the way, the car behaved all of the way home, after we left Dead Horse Point this morning, we gassed up and drove into Salt Lake. 211 miles and it took 5.52 gallons to fill up.......I thought that can't be right..38mpg....fuel injection rocks!!!!!

We've already been talking about the next one we go to..Thank you to all for making our first 914 rally an absolute blast!!!! My kids were kind enough to point out all of the ones they liked better than ours..haha I really didn't expect to see that many 914's so that was really cool.

For those of you that helped organize this event, thank you!

draperjojo
(and Jeff, thanks for the ride in the "six"!!)

Posted by: Eric_Shea Sep 24 2006, 07:04 PM

(I have a spare -6 in my garage )

Did it perform better once the valve was adjusted properly? Looks like it... 38mpg!! Very Cool.

Posted by: Air_Cooled_Nut Sep 25 2006, 12:45 PM

We're assuming stock tires are being used? That is a very good (high) number.

Posted by: ChrisNPDrider Sep 25 2006, 12:56 PM

38 mpg = believe it.
I just finished my 3rd 700 mi+ road trip in just over a month. In my '72 1.7 FI I've been getting 33-35 mpg on hwy 101 in CA.
This is with 195/50 tires, cruising at 3.5-4k on the tach and roughly 70-80mph.

Posted by: WRX914 Sep 25 2006, 01:02 PM

I only got between 25 and 28 mpg. I was cruising at about 4k on the tack, but I was clipping along at between 100 and 110 the entire way to Vegas. Took us about 6 hrs flat and came home to a newly born nephew! Sorry we had to leave early...

Posted by: grantsfo Sep 25 2006, 01:23 PM

My stock 1.8 averaged 36 MPG when I drove it from Georgia to California a few years ago. Skinny little 15-165 tires helped I'm sure.

Posted by: draperjojo Sep 25 2006, 06:39 PM

I just put on a set of Yokohama 195/65r-15 before the RRC, so really close to stock size. The trip home I was just cruising in the 65-75mph range since the wife was following behind me. That may be why the higher number. Had I been running 100mph I'm sure the mpg would have suffered.

Posted by: Crazyhippy Sep 25 2006, 07:07 PM

I kicked out just over 30 coming home from Vegas... and we were over 100 for several long streches Made 315 miles in 3:40 For an AVERAGE speed of 85ish

BJH

Posted by: Howard Sep 25 2006, 07:56 PM

According to Jill, the nagging voice in my GPS,
1694 miles, 54 gallons of dead dino juice = 31mpg??? Wow!
Average moving speed for whole trip = 72.6mph.
Top speed = MYOB
2.0 with 195/65's.

Posted by: jimtab Sep 25 2006, 08:37 PM

Mark will have to confirm but I think we did 1050mi in 13 hrs at about 25mpg in the Pontiac Brick....

Posted by: McMark Sep 25 2006, 08:43 PM

Posted by: Air_Cooled_Nut Sep 25 2006, 10:12 PM

If the aspect ratio of the tire is not specified on the sidewall it is 85. Thus a P165R15 would normally be designated a 165/85R15. 85 is the default aspect ratio for P-metric tires so they normally don't put it on the sidewall.

According to my references the 1975+ cars were equipped with 165 SR 15 tires. That's our base line and gives a 26.04" tire diameter.

195/65R15 gives a 24.98" tire diameter. Thus the speedometer/odometer error is 4%. So for every 100 miles indicated on the odometer you've actually traveled 96 miles. This also means that an indicated 75mph is actually 72.0mph.

Pre-1975 cars used 155 SR 15 tires. The calculations vs. 195/65R15:
Speedometer error: 2%
Indicated 75mph is actually 73.9mph
-- A pretty close match! --

1975+ cars used 165 SR 15 tires. The calculations vs. 195/50R15:
Speedometer error: 13%
Indicated 75mph is actually 65.3mph
-- A lousy match! --

Pre-1975 cars used 155 SR 15 tires. The calculations vs. 195/50R15:
Speedometer error: 11%
Indicated 75mph is actually 67.1mph

It may not look like a big difference but it IS and it DOES add up. Even a 2% error needs to be corrected for more accurate results.

If you want to check yourself then you can download http://www.icbm.org/erkson/personal/auto_math.xls from my website (uses Microsoft Excel). Look on the "Tire Size Formulas" sheet.

These are simple mathmatical calculations and don't account for tire squish and assume the speedo matches the tires

Posted by: Toast Sep 25 2006, 11:28 PM

I got about 28 mpg on this trip. Not bad considering the statistics.

Statistics:
Had to make frequent stops to add oil, have huge tires (205/65/15), flogging a tired engine with a loose valve, AND a push rod tube that was draining 2 quarts of oil every 50 miles for 93% of the time to try to keep slits from bitchin about my driving (that didn't help....just heated my engine and burned more gas ), had an extra 200 lbs for 832 of 1400 miles (still had to flogging the engine for slits).

Posted by: GWN7 Sep 25 2006, 11:37 PM

28 mpg....how much oil did you use on the way home?

Posted by: Toast Sep 26 2006, 12:34 AM

1/2 quart.

Posted by: SirAndy Sep 26 2006, 09:29 AM

you could have saved yourself a lot of time and just used the TSC™ (Tire Size Calculator) in the "914 Info" section. (see menu on top of each page) ...

Andy

Posted by: Air_Cooled_Nut Sep 26 2006, 10:21 AM

But I already have the Excel workbook and I program in Excel (but the wkbk wasn't my creation) so I could set up multiple data sets for comparison -- it was no waste of time and far more flexible. Besides, the TSC doesn't allow for 155 SR 15. It is a neat app., thanks for pointing it out.

Posted by: SLITS Sep 26 2006, 12:15 PM

Try 205/65/15 for tires (25.4" rolling diameter)

Push rod tube seal - not a valve

Will not bitch about your driving style anymore .... I'll just drive my own style and see you when (or if) you arrive at the appointed destination.:insertstickingtongueoutsmiley:

Posted by: Toast Sep 26 2006, 12:23 PM

changes made to original post.

i'll get there eventually, that's why I have the 200 mile AAA tow.

Posted by: draperjojo Sep 26 2006, 12:28 PM

I could be off a little. My car is a 1974 and the 195/65r-15 were very close to original specs. The wife's Durango showed the trip distance at 208 miles, not 211. That still puts my mileage at 37.68 mpg for 5.52 gallons of fuel burned.

Posted by: SirAndy Sep 26 2006, 12:41 PM

that's because that wasn't a stock size ...
Andy

Posted by: Air_Cooled_Nut Sep 26 2006, 12:49 PM

So the Haynes manual is wrong? Well, I wouldn't be totally surprised. But I thought I read in my other references that tire size as well...I'll need to check when I get home. Or was that tire size available like the Sportomatic?

Posted by: Air_Cooled_Nut Sep 26 2006, 10:47 PM

I have two Brooklands Books (ISBN's: 0-948207-45-0 and 0-906-589-843) on the Porsche 914 (magazine articles of the time) and I have tagged several articles where cars were tested with 155 SR 15 tires. Not just listed on the data sheet like the automatic tranny, actually tested using the tire. The 155 was designated for the 914/4 (early models) while the 165 was for the 914/6. The 165 was also an upgrade and later became stock on later models. This is what I've read from the magazine articles, some USA, some European (and one Austrailian, a Crayford right-hand drive conversion!).

I also found it in my VW/Porsche 914/4 1.7 and 2.0 Litre Repair Guide by Peter R.D. Russek, Glovebox Series, ISBN 0-903168-93-6, and in the Grp. 6, section 4.1, Porsche 914 914/6 workshop manual.

Simply what I've read so far.