Advice: Heavy VAN TPI -torque and MPG build: Knock Risk

[rebelrouser]

For what it is worth here are my advice. 1st If you increase the HP and torque output out of an engine, it will burn more fuel, I just don't see how you get around that. 2nd I would design the build around the RPM you will run the vehicle down the road the most which is Hwy cruising speed. Select camshaft, manifold runner length and size, etc. to that goal. Whatever gears you choose, figure out what cruise rpm will be and then pick a camshaft to give maximum torque in that range. Maximum torque should be the most efficient combustion of fuel and give you the best fuel economy. If it is going to use fuel injection make sure it has a system to detect spark knock, lots of timing at low load cruise will give you the best MPG, then under a load the timing needs to retard. If it is just a conventional distributor, one of the adjustable vacuum advance diaphragms is something I would do. I base a lot of this on engines I have built, in particular a 400 SBC in a 1978 chevy crewcab I used to pull my race car trailer. When I first built it empty it got a respectable 15 MPG. Loaded with an open trailer, equipped with a storage box it got 13MPG. Then I switched to an enclosed trailer and the truck pulled the load great, but economy dropped to 8 MPG. I bought a Dodge Cummins diesel, it will pull anything, and still gets decent mileage. 20 MPG empty, and 10 to 13 MPG trailer loaded 18,000 lbs. It runs 1,600 rpm at 65 miles per hour. It will outlast two gas engines at least. When I was a young tech at a chevy dealer, we sold a lot of dump trucks, clay mining in our area, this was the early 70's all the trucks were gas engines, a few were still 409's I swapped several 409's out with 427 chevy truck crate engines back then. How many gas powered dump trucks do you see now?

[NewbVetteGuy]

Of course these projections do not, cannot show what effects wind resistion and rolling resistion will be and how they will affect the real world MPG. But I believe it will only be minor.
...
The only thing that will be a facture will be how much wind resistion will hurt my MPG…which seems to not to all that it is trumped up to be.


Rich

I'm not convinced that wind resistance won't be a big factor for a giant box-shaped van with a HUGE frontal area driving down the highway. Wind resistance goes up 4x as speed doubles...

There's loads of low rolling resistance tires available now and they often tend to last longer, too. The new EV tires have a lot of characteristics that seem relevant to your TPI van build as they're built for heavy vehicle, to reduce rolling resistance AND to provide lots of traction to deal with EV's ridiculous torque. (But they're not exactly budget and I keep seeing Michelin releasing their newest and best EV tires only in the EU lately...)


Adam

[racprops]

"For what it is worth here are my advice. 1st If you increase the HP and torque output out of an engine, it will burn more fuel, I just don't see how you get around that."

Well back in the 90s I swapped in a OLDS 350, no change in MPG from SBC350. It lost two rockers, so we dropped in a OLDS305: Major mistake, lost major hill claiming power, was in the way of big rigs, and MPG dropped like a rock.

"2nd I would design the build around the RPM you will run the vehicle down the road the most which is Hwy cruising speed. Select camshaft, manifold runner length and size, etc. to that goal. Whatever gears you choose, figure out what cruise rpm will be and then pick a camshaft to give maximum torque in that range. Maximum torque should be the most efficient combustion of fuel and give you the best fuel economy. If it is going to use fuel injection make sure it has a system to detect spark knock, lots of timing at low load cruise will give you the best MPG, then under a load the timing needs to retard."

Done, engine old school 383, cam makes torque from 1500 and peaks at 1800RPMs, running Rhoads Roller lifters. Heads 193 unchanged, intake 87 Camaro TPI, computer 16197424 moded for MPFI. Whole set up will not run over 5K. I will run a rebuilt 4L80e with a US gears Dual Range Over Drive so this combo will allow running at 75MPH at 16/1700 RPMs.


"If it is just a conventional distributor, one of the adjustable vacuum advance diaphragms is something I would do. I base a lot of this on engines I have built, in particular a 400 SBC in a 1978 chevy crewcab I used to pull my race car trailer. When I first built it empty it got a respectable 15 MPG. Loaded with an open trailer, equipped with a storage box it got 13MPG. Then I switched to an enclosed trailer and the truck pulled the load great, but economy dropped to 8 MPG. I bought a Dodge Cummins diesel, it will pull anything, and still gets decent mileage. 20 MPG empty, and 10 to 13 MPG trailer loaded 18,000 lbs. It runs 1,600 rpm at 65 miles per hour. It will outlast two gas engines at least. When I was a young tech at a chevy dealer, we sold a lot of dump trucks, clay mining in our area, this was the early 70's all the trucks were gas engines, a few were still 409's I swapped several 409's out with 427 chevy truck crate engines back then. How many gas powered dump trucks do you see now?"


All very well. Diesels have high torque, my engine shows around 400FTPDs at 2000RPMs....diesels have no pumping loses, I may be able to offset that at cruse by adding extra EGR. Diesels have higher internal drag.

I have a picture of a window sticker of a 2019 Chevy long wheel base 3500 Express Van a higher, bigger, heavier, VAN than my G20, running a 4.6 V6 with a 8 speed transmission that is rated at 29MPG highway. I will also run lean burn cruse model or now called highway mode.

The van stock got 14 MPG, I will be happy with 20MPG highway, anything over that will be icing.

Rich

[racprops]

"I'm not convinced that wind resistance won't be a big factor for a giant box-shaped van with a HUGE frontal area driving down the highway. Wind resistance goes up 4x as speed doubles...

There's loads of low rolling resistance tires available now and they often tend to last longer, too. The new EV tires have a lot of characteristics that seem relevant to your TPI van build as they're built for heavy vehicle, to reduce rolling resistance AND to provide lots of traction to deal with EV's ridiculous torque. (But they're not exactly budget and I keep seeing Michelin releasing their newest and best EV tires only in the EU lately...)


Adam"

I have a picture of a window sticker of a 2019 Chevy long wheel base 3500 Express Van a higher, bigger, heavier, VAN than my G20, running a 4.6 V6 with a 8 speed transmission that is rated at 29MPG highway.

Interesting about the low rolling resistance tires, up until now such tires normally traded traction for low rolling resistance, thus I would trade in a MPG even a couple of MPG for traction and shopping grip. I have stayed away from long mileage tires as to get those miles means harder rubber and less traction.

Got any reports of these new super tires compared to normal good traction tires??

Rich

[NewbVetteGuy]

"I'm not convinced that wind resistance won't be a big factor for a giant box-shaped van with a HUGE frontal area driving down the highway. Wind resistance goes up 4x as speed doubles...

There's loads of low rolling resistance tires available now and they often tend to last longer, too. The new EV tires have a lot of characteristics that seem relevant to your TPI van build as they're built for heavy vehicle, to reduce rolling resistance AND to provide lots of traction to deal with EV's ridiculous torque. (But they're not exactly budget and I keep seeing Michelin releasing their newest and best EV tires only in the EU lately...)


Adam"

I have a picture of a window sticker of a 2019 Chevy long wheel base 3500 Express Van a higher, bigger, heavier, VAN than my G20, running a 4.6 V6 with a 8 speed transmission that is rated at 29MPG highway.

Interesting about the low rolling resistance tires, up until now such tires normally traded traction for low rolling resistance, thus I would trade in a MPG even a couple of MPG for traction and shopping grip. I have stayed away from long mileage tires as to get those miles means harder rubber and less traction.

Got any reports of these new super tires compared to normal good traction tires??

Rich

I know you know my opinions on how different a Variable Valve, Direct Injected v6, with a modern computer-controlled 8 speed transmission is vs. a Gen1 SBC, but the 1st will ALWAYS get my money in a fuel economy contest...

Search for "Michelin Pilot Sport EV" tires. I couldn't find the article that I originally read on them when they were first announced for the European market only, but LOTS of high tech wizardy in compounds and tread patterns to deal with the heavy truck-like weights, the insane torque of an EV, plenty of silicon to give low rolling resistance and long wear life, and the special acoustic foam that the luxury EV Tesla and Porsche buyers want. -But only released initially in standard Tesla sizes, and $400 a tire, IF you can find them. (Although a set of Pilot Sports on a van is kinda of hilarious...)

A good bit of tech all thrown into a single tire. I think they were advertising that a long-range Tesla Model S could get up to 37 miles extra range out of them.

TireRack only has a single size right now. https://www.tirerack.com/tires/tires.js ... R0PSEVXLAC

A heavy van with a torquey TPI engine and MPG goals and an EV share a shockingly common number of tire-related requirements to me. (Ability to deal with heavy loads, still have good traction, low rolling resistance, and good life -especially if they're $400 a tire!)

-I like that EVs are forcing tire manufactures to build a tire that has maximum rolling resistance AND good traction and I can only hope that the technology becomes widely available and starts trickling down.


Adam

[Clemson327]

That 37 mile range delta must have been compared to the Pilot Sports offered on the optional 21” wheels on the Model S. Mine has 19” wheels, and the OEM tire is a Michelin Primacy MXM4. Per the results on the Tesla forums, these provide the best range compared to Goodyear/Pirelli EV offerings, and they have excellent wet/dry traction for a touring tire. With sizes available down to 17” wheels, I’d look for something like that.

As a reference, I reached almost 50k miles with the original set and currently have over 20k on the second set with no replacement coming soon.