Got a new 914!, Post 2011 Evil Tranny Clinic update: Options

[DanT]

Exactly Jon,
If my odo is off 10% then when my mileage shows 5,000 miles I have actually only driven about 4500 miles. So I would be actually doing service more frequently than needed.

[flipb]

Jon has a good point.

The engine doesn't care how many miles the wheels have turned. Wear & tear on the engine is most closely correlated with how many revolutions it's turned.

The stock ODO (if functioning correctly) will always be a [indirect] measure of how many revolutions the engine has turned.

If you put on different sized wheels/tires, and you subsequently cover less (or greater) distance per revolution of the engine, that does NOT mean the engine has worked a different amount.

This doesn't account for difference in rotating mass, etc. - so there's a pretty complex equation here. But the stock ODO, driven off the stock gearing in the transmission, is a more accurate reflection of how many revolutions the engine has turned than "Actual miles traveled".

[Tom_T]

OK - I see your points.

But if it were on my 73 2Lthen 914 at almost 39 years old (1st sold 11/72), I think that I'd still err on the side of caution & do the maintenance a bit sooner - rather than later per the odo reading. ..... ditto on oil/filter, etc. (IMG:style_emoticons/default/shades.gif)

JMHO & JM2C (IMG:style_emoticons/default/smile.gif)

On the other side with higher error (+) - the higher odo reading is primarily an economic loss of value for a collectible car with more miles showing than actual.

[Tom_T]

Exactly Jon,
If my odo is off 10% then when my mileage shows 5,000 miles I have actually only driven about 4500 miles. So I would be actually doing service more frequently than needed.

Dan - that's only if your error is +10% (plus) on "bigger" radius/diameter/circumference - which is mainly affecting the value of the car negatively by showing more miles on it that actual.

Some tire/wheel set-ups are -10% (minus), which is what I was referring to on the maintenance issues, since the economic value may be higher reading a lower odo total on "smaller" tires.

You have to read the + or - signs on the tire calculator guys, otherwise you're adjusting bass-ackwards for the mpg & everything else! (IMG:style_emoticons/default/huh.gif)

[DanT]

Tom,
205x50s are smaller in overall diameter=more revolutions per mile=higher speedo and odo readings for same speed and distance.

[Root_Werks]

Good info guys, thanks!

I've never, ever, ever been in any Porsche that had a dead on speedo. They've all read too fast. The closest was an 83' 944 I had about 15 years ago. It was too fast, but only by about 2mph @60mph reading (so 62mph was actually 60mph)

The worst I've seen was a 914 that had 14" 914-6 fuchs with 185/60/14's on it. Sheese, that thing read something like 75mph on the gauge when it was only really going maybe 60mph, crazy!

But my exposer to the marque is limited.

(IMG:style_emoticons/default/wink.gif)

[AndyB]

(IMG:style_emoticons/default/blink.gif) (IMG:style_emoticons/default/blink.gif) (IMG:style_emoticons/default/blink.gif)

[Tom_T]

Some examples from the tire calculator on here vs. stock 165(/80)R15 size:
http://www.914world.com/specs/tirecalc.php

Some common choices I see folks use that are giving more miles on odo than actual:
205/50R15 = 9.1% smaller & reads faster/more miles @ odo
195/60R15 = 4.7% smaller & reads faster/more miles @ odo
195/65R15 = 1.6% smaller & reads faster/more miles @ odo
185/70R15 = 0.8% smaller & reads faster/more miles @ odo

Whereas, these are some other sizes undercounting odo mileage:
225/60R15 = 0.9% bigger & reads slower/less miles @ odo
205/65R15 = 0.4% bigger & reads slower/less miles @ odo
185/75R15 = 2.1% bigger & reads slower/less miles @ odo
175(/80)R15 = 2.5% bigger & reads slower/less miles @ odo

Note that 165(/80R15 & 175(/80)R15 are actually labeled as 165R15 & 175R15 with the /80 section height implied or assumed for all of the older 1970's era tire sizes without a section ht. listed (i.e.: the height of the tire's cross section is 80% of width, /65 = 65%, /55 =55%, etc.).

(IMG:style_emoticons/default/idea.gif) So this begs the question if the early 914/4's with 155R15 tires were in fact 2.5% too fast & smaller ~ or was it the other way around with the 165R15s on 914-6s & 914-2.0s & later 1.7s/1.8s were about that much too slow?? ... because I doubt that VW-Porsche changed the speedo/odo gearing for the 2 tire sizes! (IMG:style_emoticons/default/confused24.gif)

Back then a 5% speedo error was considered acceptable, average & normal - and I think still is today, and I doubt many of the "modern" electic speedos today are spot on. Yeah, I'm sure a bunch of you will now jump in on how accurate their speedo is, but that's hardly an industry average.

As such it saved my (IMG:style_emoticons/default/bootyshake.gif) a couple of times on speeding tickets by claiming that the "5 mph over the limit" was due to normal speedo error! (IMG:style_emoticons/default/biggrin.gif)

.

So Root, let us know how a set of 165R15s, with stock recco'd 26 psi or more air (maybe 28-32), a tune-up to factory specs, & a "lighter foot" on the gas works for your 40 mpg goal!!?? (IMG:style_emoticons/default/biggrin.gif)
(IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif)

[Tom_T]

Good info guys, thanks!

I've never, ever, ever been in any Porsche that had a dead on speedo. They've all read too fast. The closest was an 83' 944 I had about 15 years ago. It was too fast, but only by about 2mph @60mph reading (so 62mph was actually 60mph)

The worst I've seen was a 914 that had 14" 914-6 fuchs with 185/60/14's on it. Sheese, that thing read something like 75mph on the gauge when it was only really going maybe 60mph, crazy!

But my exposer to the marque is limited.

(IMG:style_emoticons/default/wink.gif)

Yeah, but you REALLY thought you were going FAST in that 914! (IMG:style_emoticons/default/laugh.gif)
... and if you put 205/45R14s on it you could probably tell folks you drive 100 on the freeway to work every day! (IMG:style_emoticons/default/lol-2.gif)

[messix]

Some examples from the tire calculator on here vs. stock 165(/80)R15 size:
http://www.914world.com/specs/tirecalc.php

Some common choices I see folks use that are giving more miles on odo than actual:
205/50R15 = 9.1% smaller & reads faster/more miles @ odo
195/60R15 = 4.7% smaller & reads faster/more miles @ odo
195/65R15 = 1.6% smaller & reads faster/more miles @ odo
185/70R15 = 0.8% smaller & reads faster/more miles @ odo

Whereas, these are some other sizes undercounting odo mileage:
225/60R15 = 0.9% bigger & reads slower/less miles @ odo
205/65R15 = 0.4% bigger & reads slower/less miles @ odo
185/75R15 = 2.1% bigger & reads slower/less miles @ odo
175(/80)R15 = 2.5% bigger & reads slower/less miles @ odo

Note that 165(/80R15 & 175(/80)R15 are actually labeled as 165R15 & 175R15 with the /80 section height implied or assumed for all of the older 1970's era tire sizes without a section ht. listed (i.e.: the height of the tire's cross section is 80% of width, /65 = 65%, /55 =55%, etc.).

(IMG:style_emoticons/default/idea.gif) So this begs the question if the early 914/4's with 155R15 tires were in fact 2.5% too fast & smaller ~ or was it the other way around with the 165R15s on 914-6s & 914-2.0s & later 1.7s/1.8s were about that much too slow?? ... because I doubt that VW-Porsche changed the speedo/odo gearing for the 2 tire sizes! (IMG:style_emoticons/default/confused24.gif)

Back then a 5% speedo error was considered acceptable, average & normal - and I think still is today, and I doubt many of the "modern" electic speedos today are spot on. Yeah, I'm sure a bunch of you will now jump in on how accurate their speedo is, but that's hardly an industry average.

As such it saved my (IMG:style_emoticons/default/bootyshake.gif) a couple of times on speeding tickets by claiming that the "5 mph over the limit" was due to normal speedo error! (IMG:style_emoticons/default/biggrin.gif)

.

So Root, let us know how a set of 165R15s, with stock recco'd 26 psi or more air (maybe 28-32), a tune-up to factory specs, & a "lighter foot" on the gas works for your 40 mpg goal!!?? (IMG:style_emoticons/default/biggrin.gif)
(IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif)

he'll never see 40mpg commuting to work living where he does.

the topography of the area here has too many hills [we call them hills some back east would call mountains.] and Dan has several to climb and descend on the way to work, he lives at about a 500 ft elevation and descends to near sea level and then back up to about 500 ft again near work and this is with many elevation changes along the way.

traffic in this area is another reason he won't see 40mpg... this area has terrible traffic. his route is especially bad!

high 20's will be outstanding.

[Tom_T]

he'll never see 40mpg commuting to work living where he does.

the topography of the area here has too many hills [we call them hills some back east would call mountains.] and Dan has several to climb and descend on the way to work, he lives at about a 500 ft elevation and descends to near sea level and then back up to about 500 ft again near work and this is with many elevation changes along the way.

traffic in this area is another reason he won't see 40mpg... this area has terrible traffic. his route is especially bad!

high 20's will be outstanding.

I didn't think he was looking for 40 mpg commuting in his 914, but rather as a quest in leisure driving. He'll definitely need to try it on a flat stretch of highway without traffic to get it, and work at it to not be tempted by the notorious "914 lead foot disease"! (IMG:style_emoticons/default/biggrin.gif)

If Root is looking for commuting at 40 mpg, then he needs to look at another econo-box hi miler or hybrid & leave the Teen for weekend fun! (IMG:style_emoticons/default/dry.gif)

[Root_Werks]

Some examples from the tire calculator on here vs. stock 165(/80)R15 size:
[url=http://www.914world.com/specs/tirecalc.php]

he'll never see 40mpg commuting to work living where he does.

the topography of the area here has too many hills [we call them hills some back east would call mountains.] and Dan has several to climb and descend on the way to work, he lives at about a 500 ft elevation and descends to near sea level and then back up to about 500 ft again near work and this is with many elevation changes along the way.

traffic in this area is another reason he won't see 40mpg... this area has terrible traffic. his route is especially bad!

high 20's will be outstanding.

Troy, stop following me to work! (IMG:style_emoticons/default/av-943.gif)

[sixnotfour]

Troys gets the best.....0 miles per gallon. (IMG:style_emoticons/default/driving.gif) Not ...

[Tom_T]

Troys gets the best.....0 miles per gallon. (IMG:style_emoticons/default/driving.gif) Not ...

HEY!!!!!! ..... I resemble that remark buddy! (IMG:style_emoticons/default/mad.gif)

I haven't used a gallon yet rolling mine in & out of the garage for a year! (IMG:style_emoticons/default/biggrin.gif)

[sixnotfour]

HEY!!!!!! ..... I resemble that remark buddy! mad.gif

I haven't used a gallon yet rolling mine in & out of the garage for a year! biggrin.gif

you guys should form a club

[Root_Werks]

As some know, I pulled the transmission from the 914 and took it down to the Dr. Evil Tranny Clinic here in the PNW the weekend of May 7-8. The transmission in this 914 only has 120k miles on it, shifts fine, no wines, whirs, grinds etc. So my goal was to change out a couple of gears. Dr. Evil had what I was looking for (more on that in a second).

Pre-Tranny clinic, I pulled off the raspy sounding Bursch system. (IMG:style_emoticons/default/icon8.gif) I can't stand the sound the 914 was making between 1900-2800rpms. Sounded almost like a Honduh fart can. So I added this:

[Root_Werks]

Using the tools from 914world, here is the stock gear chart with my current size tires:

[Root_Werks]

And here is the new gear chart (same tires of course):

[Root_Werks]

Driving impressions:

Loving the new combo! The little glass pack made a pretty big difference. No more raspy, crapy sounding exhaust note. Much quieter and lower from the exhaust tip. Couple that with lower rpm's and 60mph in 5th, you cannot hear the engine, just wind noise as it's turning something around 2200 rpms. Nice! the spacing bewteen 3-4-5 is perfect for the area we drive in. 4th is tall enough to use on longer freeway grades so I don't load the engine and 5th is perfect for those long flat cruises.

I ran a test for those local who know the road:

I ran up hwy204 to Frontier Village in 5th @55mph (1800rpms I think?). I tapped the gas and just kept digging into the throttle little by little as I climbed the hill. Never knocked/pinged and the L-Jet 2.0 pulled it up past 75mph until I felt a speeding ticket wouldn't be cool so I slowed back down.

Cool! I'm ready for summer driving.

(IMG:style_emoticons/default/driving.gif)

[avidfanjpl]

I am taking Orangina on a ride up to Central Coast Wine Country this weekend with 205/50's and my GPS.

If it is 500 miles on the GPS, it will be 545 when I get home.

My 205/60's are at Al Reed's but I have to go.

so much for that.

I am thinking of putting the Banana back on to keep Janice from freaking out on the Monza sound.

Not sure.

Getting 28MPG with the Pertronix on 89 Octane. May switch to 87! Runs better than on 91. Thank you, Mr. Gaglione, once again!

TOP DOWN DRIVING FOR US!

Screw that 15% rain prediction.

John