Redline and top speed. . .

Captain Spalding · Posted: Sun Apr 15, 2012 11:00 am Post subject: Redline and top speed. . .

Hello all,

I know this topic has been covered before, but I'm hoping to delve a little deeper.

In a few recent topics folks have indicated that they drive their Things on the highway at 75 mph. While I don't doubt them when they say they do, I'm wondering if it's deleterious for the engine to be run that fast for long periods.

Exhibits A and B: Sales Brochures.
This 1973 Thing sales brochure in the archives states the top and cruising speed at 68 mph. This sales brochure, for a '72, lists the top speed (cruising not mentioned) at 71 mph. My understanding is that top speed is determined by redline in the highest gear, and typically "cruising speed" should be less than top speed. It's notable that VW reduced the recommended top speed from 71 to 68 mph and called it the cruising speed too.

Exhibit C: the speedometer.
My speedometer has red hash marks indicating shift points for each gear. First to second gear is at around 16 mph, second to third gear is around 32 mph, and third to fourth at 48. If you extrapolate out to fourth gear, that's 64 mph. I realize that the gear ratios are not evenly spaced, but the difference between 3rd and 4th is not so great that 4th can be construed as an overdrive.

I suspect that those of us (with stock motors, transaxles, and tires) who are happily cruising along at 75 mph on the highway are pushing our motors beyond redline.

And now some questions. Has anyone seen in print a figure for the redline?

About redline: on what factors is it based? Not just for the Thing but for any car? Is it an issue of oil distribution? Valve float? Cooling ability? For those speed demons out there, what can be done to legitimately raise the redline?

As an aside, in a 1973 Road and Track article, under Interior Noise it says that the noise level in a Thing at 70 mph is 90 db. According to OSHA, noise levels over 80 db contribute to incremental hearing loss. So if you're cruising at 75 mph on the highway, whether or not you're not doing damage to your motor, you are certainly doing damage to your hearing.

FV195 · Posted: Sun Apr 15, 2012 2:02 pm Post subject:

I drive at 75+ on the highway, but non stock motor, and rear tires. speed checked with GPS motor running at 3,500RPMs, in my car top speed seems more limited my areo drag than power. I can not get my speedo over 90. even though I rev it much higher in other gears.
as far as noise levels, I can still hear my radio, not a monster system. no amps or anything.
THOR

SilverThing · Posted: Mon Apr 16, 2012 4:33 am Post subject:

I arbitrarily decided that redline would be 4k for a bone stock 1600 (figuring that factory torque/hp graphs only go up to 4k). For stock gearing and tires this puts top speed at around 79.5mph. Personally I try not to go faster than 60-65 (3-3.5k rpm).

For most cars, fuel economy drops pretty quickly as you drive faster than 55mph. The Thing isn't as aerodynamic as most cars.

Just my $0.02
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nikita · Posted: Mon Apr 16, 2012 3:58 pm Post subject:

There are very few 100% stock Things on the road. How many still run 185R14 tires? That has a lot to do with effective gearing. With stock gearing and tire size, I calculate 77mph@4000rpm. I suspect a stock engine cant push a brick against the wind that fast. 68 seems more reasonable. A '72 would be different with a swing axle trans and reduction gears.

Ive got a modified 002 bus trans with unknown 4th gear and 235/75-15 tires. I suppose I need to get out the GPS and calibrate the speedometer.

joescoolcustoms · Posted: Mon Apr 16, 2012 5:42 pm Post subject:

Engineering standpoint, a top cruising point would consider the effectiveness of the cooling system for long term use. I had read 20, maybe 30 years ago that the peak cooling on a T1 style VW engine is between 3000 and 3500 rpm, with stock equipment.

I do know that the cooling fan will flow more air the faster it is turned (with respect to what a stock VW engie will turn), but there is a tipping point when the heat generated by running harder over takes what a faster cooling fan will cool.

Another limiting rpm factor on a VW engine is it is not balanced from the factory. The higher the rev's, the quicker it will pound out the bearing journals and distort the case (stock engine). 4000 rpm is a good redline on a stock VW AC engine in our Things.

My '73 is bone stock and original (except for the distributer, clutch and muffler have been replaced). I have set my cruising speed at 60 to 65. Fuel milage drops as I creep over 55. It will run over 70, but I choose not to.

I did not hear what you said about the noise level though.
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Captain Spalding · Posted: Mon Apr 16, 2012 5:59 pm Post subject:

See, here's the thing. It's inconvenient that we don't have a printed specification for redline. Where are you guys coming up with 4000 rpm? Using an online RPM calculator (which, I admit, I'm not sure I'm using correctly), with stock gearing and tires, at the stated top speed of 68 mph, I'm getting 3417 rpm. As 68 is the stated top speed of the vehicle, would we not consider 3417 to be the redline?

Using the same calculator, and recalculating for the same RPM with 27" diameter tires, the car will reach approximately 72 MPH.

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50352

One of my old GF used to drive my first 1973 Thing at speeds up to 80 mph regularly. She thought she had the ordained right to drive it and any other vehicle at those speed regardless of the road condition or anything else, like my engine's well being. The engine survived her driving but actually died after I over revved it, reaching speeds of close to 80 in third gear when some drunk in a dump truck decided he was going to try and ram me from behind. That was a stock factory engine with a progressive carb. It stretched the rod bolts but she didn't blow.

Captain Spalding · Posted: Mon Apr 16, 2012 6:19 pm Post subject:

@ Joe, you're thinking is more along the lines of where I was hoping this discussion would go.

I would echo what you and SilverThing said. My car will go 75 if I push it, but there's definitely a sweet spot in the 60-65 mph range where she's not laboring so hard.

joescoolcustoms · Posted: Mon Apr 16, 2012 7:29 pm Post subject:

SilverThing · Posted: Mon Apr 16, 2012 8:35 pm Post subject:

How about a less arbitrary answer? Perhaps one based on factory information?

If you look on page 16 of the 1973 or 1974 US owner's manual you will find a short list of recommended speeds by gear. It will look something like this:

Image may have been reduced in size. Click image to view fullscreen.

*Note manuals for other markets will have a similar page*

Assuming stock AV transmission gearing (9:34 1st, 17:35 2nd, 50:63 3rd, 58:54 4th, and 8:33 R/P) and a generous tire diameter of 26 inches (185/80r14 is nominally 25.65" in diameter), you will find something like this:

1st (18mph): 3625 rpm
2nd (31mph): 3402 rpm
3rd (53mph): 3560 rpm
4th (68mph): 3375 rpm

Now for the brief period top speeds:

2nd (34mph): 3732 rpm
3rd (55mph): 3694 rpm

And just because other market's owner's manuals list 115 km/h as 4th gear top speed:
4th (71.458mph): 3547 rpm

Interesting to note:
2nd (6mph): 659 rpm
3rd (15mph): 1008 rpm
4th (28mph): 1390 rpm

Also of note is the German service bulletin describing the introduction of the 181 with 1.5L engine lists a top/cruising speed of 110km/h at 4120U/min (rpm)
http://vwbus2.dyndns.org/bulli/michaelk/vw_bus_d/tm_m/TM_M_13.html
I should note that the very early 181 have pretty low gearing.

I also note that VW listed max HP for most all of its type 1 air cooled engines at 4000 rpm.

Anyone confused yet?
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nikita · Posted: Tue Apr 17, 2012 8:59 am Post subject:

DougD · Posted: Tue Apr 17, 2012 9:23 am Post subject:

I would think if someone had a tachometer installed they could just tell us what the rpm is at the recomended shift points and top speed. That should tell you what the redline rpm is. I hit 70 once and I couldnt help but imagine what the Thing would look like after a crash at that speed. I have not gone above 60-63 since...

Captain Spalding · Posted: Tue Apr 17, 2012 10:10 am Post subject:

citroen · Posted: Tue Apr 17, 2012 11:21 am Post subject:

my thing is not stock 1776, 100 cam,stock carb, dual bugpack mufflers, 165 x 15 tires, 74 bug transmission. Also my engine was balanced when i built it. I took it out today and took pictures of the rpms and speed i do have porsche guages. With a gps speed is off 2 miles at 70. Forgive the pictures it is hard taking pictures and driving.

60 mph 4th gear

70 4th gear

80 4th gear

50 3rd gear

60 3rd gear

GI Joe · Posted: Tue Apr 17, 2012 6:39 pm Post subject:

I think the bigger question here is this:
How long does it take to go 80 miles, when traveling at 80mph? Wink

Great pics Dennis... Sure looks like she smooths out at higher speeds!! lol
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SilverThing · Posted: Tue Apr 17, 2012 7:31 pm Post subject:

Unless the internals have been changed, a 74 Beetle transmission is going to have taller gearing than any Thing transmission. IE your rpms are going to be lower.
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"I like how everyone likes talking about Zeke's Thing yet he's the only one that's ever seen it." - Katie
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citroen · Posted: Tue Apr 17, 2012 8:08 pm Post subject:

Stock bug transmission. I had a thing transmission changed it because i did not like the high rpm at 70 and the noise inside. I still drive highway speeds around 65 70 with the traffic. The extra power works great with the bug transmission it does not take long to get to 80 and it does peak out around 90. I was on a 65 mph highway and i thought 80 was fast enough driving and taking pictures. And you are right joe the picture was smoother at 80.

Captain Spalding · Posted: Tue Apr 17, 2012 9:15 pm Post subject:

With a bug transmission, when you're cruising in town at 30-35 mph are you in second gear or third? It seems second would have the engine spinning a little fast and third a little slow. Or have I just been over-analyzing this whole thing from the get-go?

citroen · Posted: Wed Apr 18, 2012 6:56 am Post subject:

Third or 4th. Most the time around town i drive around 40 in 4th gear at 40 i am running 2000 rpm torque is good at that speed the only time i down shift to third is when i make a turn or go up a slight hill. I like the bug transmission , to me it is just a lot more fun to drive and i dont mind shifting i like the sound of the engine.

joescoolcustoms · Posted: Wed Apr 18, 2012 7:22 am Post subject:

I just saw this and thought it might confuse the discussion, so of course I had to post it.

When you open the Samba web site, EB has the area in the center for facts about VW's. This was just in it:


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