Dear Iain, Walt, Jerry, Good Dr., Todd, John, and mid-60s Buick owners interested in a twisted plot!
Great graphs Edouard!
Oh da' shame! All this data analysis, including graphs, are being done with Microsoft Excel when I have been a diehard Mac guy since 1988!
. . . . Did you put quiet mufflers on?
I got the quietest free flowing mufflers available according to the local experts: Dynomax Super Turbo.
http://www.dynomax.com/mufflers/super-turbo-mufflersOnce things settle down, I'm going to bring Biquette to a muffler shop recommended by my friend with the 1957 Bel Air. Both these cars are members of the family and his Bel Air was also too loud, so perhaps this shop can also do something to reduce the noise.
What weight trailer are you planning on pulling anyway?
Okay, so lets revisit this topic briefly. Early in this project I came across Author Throckmorton's epic 3000 mile journey with his 1965 Buick Special pulling a trailer carrying his 1968 GS:
https://gmcguy.shutterfly.com/pictures/622At some point in this exercise he got on a truck scale and found his consist was 10,000 pounds. So this was the proof of concept. The trailer I'm dreaming about is a Airstream 24 tradewind from the mid-60s. Here is an example from 1966:
https://www.airstream.com/wp-content/uploads/archive/9b5f2c98992b8fb9.pdfMore likely is a 23 trailer from the 1970s. There are more plentiful and after the oil crises are probably among the lightest trailers Airstream ever built. Here are the specifications for the 1975 models. The twin axle Safari was about 3500 pounds.
https://www.airstream.com/wp-content/uploads/archive/ef2f40c978cc1dc7.pdfHere is an example of a trailer on Airstream classified ads that has been gutted and is ready for a restoration:
http://www.airstreamclassifieds.com/ads/1971-airstream-safari-23-colorado/You seem very concerned with maximizing torque to the wheels.... are you guys in California doing 'trailer pull' races up mountain roads?
I think your 430 has more than enough torque to pull a trailer, and you don't need to 'maximize' anything..... just get the rpm's at your planned speeds comfortable.
Well, I'm not trying to maximize torque exactly. Instead I'm trying to make comparisons between my wagon and Buick recommendations from their 1965 and 1970 tow guides. That's what this post is trying to explain:
http://65gs.com/board/index.php/topic,3925.msg28955.html#msg28955As it turns out, I had an error in the calculations associated with that previous posting that I was now trying to correct. For example, if you compare the operational speed of the 1970 Estate wagon at 55 mph with the Buick recommended rear end ratio of 3.23:1 - the engine is within 6% of maximum torque. In that previous posting, I paid no attention to the RPM where Biquette's engine would actually make the same torque as the 1970 Estate wagon. It turns out that at 3.08:1 the engine isn't anywhere close to putting out the same torque as the 1970 Estate wagon. The idea here is to compare apples with apples and try to use Buick's own recommendations as best as I can related them to my wagon.
Let me illustrate with my 28' RV: It has a Gross Vehicle Weight, GVW, of 14,000 LBS (meaning maximum load with people, fuel, water and things). It has a Gross Combined Weight Rating, GCWR, of almost 18,000 LBS (weight of above and the weight of what is being towed). It has the Ford Triton V10 engine (410 CI) on a E450 chassis. This is the platform most commonly used in Class C RVs up to 35' in length for the last 15 years. Chevy also has a cutaway van platform used for RVs, but it is much less popular. So, the heart of this behemoth makes a maximum of ............wait for it ............ 310 HP and roughly 425 FT LBS. This is 50 FT LBs less than you are making at 2500 RPMs at probably two times any Gross Vehicle Combined Weight you would carry. This affords you the opportunity to choose from any number of gears that are economical and/or just plain comfortable for you.
Alas, I assume that your Ford Triton V10 engine has an RV cam in it. That means it makes that 425 ft•lbs of torque very close to idle. So it can handle a much heavier load. However, I assume it is a real dog on the freeway. You may remember this very old thread on Team Buick where you talked me out of trying to go with an RV cam for this engine:
https://www.teambuick.com/forums/showthread.php?20059-The-quot-epic-quot-430-rebuild-caper!&p=78108#post78108This is where things get potentially interesting. If you look at the torque graphs above, this engine is probably very close to the engine in the 1970 Estate wagon at about the same RPM ~2800. However, while the Estate wagon is maxed out at 510 ft•lbs, my wagon's engine will produce still more torque and horsepower as the RPM increases. So your advice back then may be paying some benefits now. With a heavy trailer, my wagon should still be more nimble and that should help in passing on the freeway.
We will be in California with said vehicle in less then a month. We are going to Yosemite, Redwood and Sequoia. I am not sure where you are at in relation, but I would not turn down a race up hill if it is your desire!
Well, Yosemite is a long way from the San Francisco Bay Area and it wouldn't exactly be a fair race since - I don't have the trailer yet! . . .
I would suggest plotting rpm vs speed, with separate curves for the different axle ratios and also in 2nd, 3rd, an O.D. gears.
That would show you the rpm at the various speeds you will be driving at ....
1) normal highway use at 60-75 mph in O.D.
2) pulling a trailer at highway speed, 55-65 mph, while in 3rd gear
3) pulling a trailer up a steeper grade at 45-55 mph, maybe in 2nd gear?
I might still try to do this, but I don't really have enough data points to make any clear conclusions. I need to write all this stuff up and send it to Mike Tomaszewski for his advice. Alas, it is a royal pain to convert Excel data into forum formats and converting this stuff to fit an email is basically starting the same process over again.
And you can adjust effective gear ratio by changing tire diameter.... going from a 26 inch tire to a 28 inch tire is a 7.7% change..... like going from a 3.36 to a 3.10 rear end ratio.
Unfortunately, I can go with any taller tires than I have. The spare tire well is limited to tires that are 26.4"
IMO you want 2500-3000 at 60mph. Any less and its a dog, any more and your mileage will tank and it will be buzzy at HWY speeds.
That's what I have to do anyway to reach 500 ft•lbs of torque with this engine. At 60 mph the engine is at 2890 RPM with a 3.23:1 gear and 3006 RPM with a 3.36:1 gear.
Edouard , Interesting topic so I did some calculating also . A couple more things to consider is how sticky the tires are and the brand or octane rating of the fuel you are using .
I already worked the numbers on my car and with sticky tires and REALLY GOOD FUEL its just perfect for the 3.90 gears i,ll be running .
. . . . .
Really? So how do you manage to burn the tires on the trailer? . . . . .
That should be enough amusement for
you'all to keep you busy for a while!
Cheers, Edouard
P.S. Here is a listing on eBay for a 1978 Airstream 23 foot travel trailer that is all together:
https://www.ebay.com/itm/1978-Airstream-Safari-23-travel-trailer/292613199713This one might be a decent candidate for a restoration.