Top speed, suggested long term RPM...

Necro · 08-30-2019, 08:17 AM

So I just bought a 1997 International 3800 53 passenger bus. It has the T444E 210HP Navistar Automatic with a Spicer F155S 4.33 rear end. The bus barn director told me its governed to 65MPH. Does anyone know if this is electronically limited, or RPM limited? If its electronically limited how do I remove it? Id like it to be able to cruise at 75MPH and NOT at redline. If its limited by gear ratio then whats a website where I can buy a better ring and pinion.

EastCoastCB · 08-30-2019, 09:26 AM

Quote:

Originally Posted by Necro

So I just bought a 1997 International 3800 53 passenger bus. It has the T444E 210HP Navistar Automatic with a Spicer F155S 4.33 rear end. The bus barn director told me its governed to 65MPH. Does anyone know if this is electronically limited, or RPM limited? If its electronically limited how do I remove it? Id like it to be able to cruise at 75MPH and NOT at redline. If its limited by gear ratio then whats a website where I can buy a better ring and pinion.

WHat's your rpm at 65?

brokedown · 08-30-2019, 09:31 AM

The T444E has both an rpm limiter and a max speed limiter. Both are electronic and can be reprogrammed. You didn't mention your transmission but if we take for granted it's an AT545 your top speed should be a bit higher, Taking a few things for granted, likely 72-75mph at redline.

EastCoastCB · 08-30-2019, 09:48 AM

Quote:

Originally Posted by brokedown

The T444E has both an rpm limiter and a max speed limiter. Both are electronic and can be reprogrammed. You didn't mention your transmission but if we take for granted it's an AT545 your top speed should be a bit higher, Taking a few things for granted, likely 72-75mph at redline.

I could only get 62 out of my 466/643/.444 rear combo.

Necro · 08-30-2019, 09:55 AM

Im picking up the bus on Tuesday, VIN is 1HVBBABM0VH519688 if anyone knows how to look up the tranny. Im looking at preferably 2k RPM at 75MPH.
Im planning on getting this too.
International CE powered by Navistar 7.3L T444E Common Rail - Diesel MAGNUM EVO-Tech Heavy Duty Performance Chip.

I don't want to have to be bouncing off the rev limiter for 5 hours.

brokedown · 08-30-2019, 10:08 AM

Ask the seller what transmission it has, or call international with the VIN.

Your dream of 2k at 75mph is pretty funny. That's more likely your rpm at 45.

brokedown · 08-30-2019, 10:09 AM

Quote:

Originally Posted by EastCoastCB

I could only get 62 out of my 466/643/.444 rear combo.

T444E likely spins a bit faster so you can get a couple extra mph. Mine was limited to 2600.

Necro · 08-30-2019, 10:18 AM

Is it not bad on these engines to sit at 2600 rpm for 5 hours straight over and over?

EastCoastCB · 08-30-2019, 10:24 AM

Quote:

Originally Posted by Necro

Im picking up the bus on Tuesday, VIN is 1HVBBABM0VH519688 if anyone knows how to look up the tranny. Im looking at preferably 2k RPM at 75MPH.
Im planning on getting this too.
International CE powered by Navistar 7.3L T444E Common Rail - Diesel MAGNUM EVO-Tech Heavy Duty Performance Chip.

I don't want to have to be bouncing off the rev limiter for 5 hours.

Ive got 190hp, a 545, and .342 gearing in a 5 window shorty. Mine will do 65 at 1750. Not sure about the rpm's at 2400 which is my redline. Bus will do 80+.
Performance chips won't help you lower your rpm. Not at all.
You're going to need the highest (numerically lowest) gearing you can buy to try and get 75 at 2k.

brokedown · 08-30-2019, 10:25 AM

it's certainly not great for them. Generally speaking, slow down and give yourself some breathing room. There are some buses with unlocked 6 speed transmissions that can go a bit faster than the much more common 4 speed units and I am taking a few things for granted that you didn't specify (transmission type, tire size) but if it's a typical model you're gonna be living life around 60.

cadillackid · 08-30-2019, 10:58 AM

any idea what size tires it has?

since its a 97 210 HP 53 passenger it likely has the AT545 or 643 which are 1:1 transmissions.. the MD3060 was out but was expensive option at the time .. usually only saw those on the bigger RE busses..

a 4.33 rear and 11R22.5 tires would give you the ability to run 75.. im guessing you probably have lower profiles tires than that with those gears..

once you get us that piece we can determine your top speed..

the computer speed limiter is easily changed.. to change your top RPM you need the "god mode" software.. and you dont want to ru nthe RPM any faster than the factory 2600... thats how stuff breaks.. these have thinner head gaskets than the ford 7.3's so dont spin it at 3200 like they do ..

a 444E will run at 2600 RPM all day but will probably get hot in warm weather or spin the fan constantly and get kind of yucky MPG's..

I ran mine that way for many miles before I wasted the AT545 trans and installed overdrive trans..

-Christopher

cadillackid · 08-30-2019, 11:02 AM

I should also mention that driving a school bus at 75 will use a LOT of fuel compared to running at 65.. . a bus is a big ole BOX going down the road.. faster you go the more fuel you suck..

this last 1400 mile trip we drove, we set our caravan to a pace of 62 and all of us got 12 or better MPGs.. even in my old mechanical I got right about 12.. the girl in the 444E with allison 2000 got 15.5, and the 40 foot Pusher Thomas HDX 3126E got 12.5

no one bothered us on the freeway.. we all had our headlights and flashie strobe lights on so we were easily visible to traffic barreling the highway .. stayed in the right lane and rolled..

-Christopher

Necro · 08-30-2019, 01:48 PM

what about a 373 ring and pinion? Ive been looking EVERYWHERE and I cant find a single site that says Spicer F155S 373 ring and pinion...

Sehnsucht · 08-30-2019, 02:17 PM

These kinds of questions beg more research into the power curve of the particular engine in question. Basically, if you look up an engine spec and look at its power output chart, you'll see an arch which delineates the hp and torque output across the rpm range. The 'ideal' cruising rpm is wherever that curve peaks - not to say the peak output but the point in the curve where it begins to shallow, representing diminishing gains with increased rpms. This gives you some headroom but basically it represents the point where the engine is at its most efficient. Everything else should complement that target rpm. You need to make sure the cooling aystem can maintain this rpm for the duration because remember these buses weren't necessarily designed for highway travel. I always wonder how efficient those sloped hood Blue Birds are with so little air intake exposure. Anyways, then you have your transmission efficiency to consider and obviously the most efficient gear is the 1:1 gear although overdrives are certainly a bonus for top speed without overtaxing the engine. Just make sure it has a lock-up torque converter to avoid parasitic power losses. Then your differential gear ratio and tire size will round out the expected cruising speed expectation so long as they aren't so steep that they overtax the engine off the line. Imagine trying to start pedaling a ten-speed bike in top gear from a dead stop - that's what your engine is going to be expected to do if you get too extreme with your differential gearing in a quest for fast and efficient top cruising speed.

I had a calculator tool for all this back when I did Jeep Wrangler gearing but I haven't seen it in years. Basically I found a slightly deeper differential gear got the cruise rpm a little higher, improving cruising performance and fuel efficiency because it wasn't languishing on the bottom of the torque band. Wrangler lifted on 35s getting 20mpg... I just wish the manufacturer would figure this out! Anyways, the same can be figured out for buses but up to the point that the components can tolerate the stress.

cadillackid · 08-30-2019, 02:18 PM

do you still know what size wheels and tires are on it?
that is a huge factor into what gearing you will need / want

kazetsukai · 08-30-2019, 02:35 PM

Quote:

Originally Posted by cadillackid

I ran mine that way for many miles before I wasted the AT545 trans and installed overdrive trans..

HOW does one accomplish this (transmission upgrade)? I have a 37' RE and this is complete mysticism for me.

TheHubbardBus · 08-30-2019, 02:38 PM

Speaking of tires, another limiting factor on your top speed is... tires. And not just due to their impact on gearing.

From what I've seen so far, 75mph seems to be the most common max-speed rating on commercial tires for these applications. But many are below that. Just thumbing through the Bridgestone commercial catalog I see some at 68mph, some at 65mph, etc. Again, that's the MAX speed.

cadillackid · 08-30-2019, 03:34 PM

Quote:

Originally Posted by kazetsukai

HOW does one accomplish this (transmission upgrade)? I have a 37' RE and this is complete mysticism for me.

http://www.skoolie.net/forums/f27/th...ion-18188.html

EastCoastCB · 08-30-2019, 03:42 PM

Quote:

Originally Posted by TheHubbardBus

Speaking of tires, another limiting factor on your top speed is... tires. And not just due to their impact on gearing.

From what I've seen so far, 75mph seems to be the most common max-speed rating on commercial tires for these applications. But many are below that. Just thumbing through the Bridgestone commercial catalog I see some at 68mph, some at 65mph, etc. Again, that's the MAX speed.

That's not actually true. There are plenty of tires rated higher. And you can adjust the inflation for the speeds intended.
Bone stock school buses in some districts are capable of over 80.

TheHubbardBus · 08-30-2019, 04:14 PM

Quote:

Originally Posted by EastCoastCB

That's not actually true. There are plenty of tires rated higher. And you can adjust the inflation for the speeds intended.
Bone stock school buses in some districts are capable of over 80.

I didn't say there weren't higher speed rated tires. I said that 75mph appeared to be the most common. Is this not true? It is for Bridgestone. I can say that with certainty, because I have their commercial tire catalog in front of me right now. 75mph is by far the most common. And I while there are lower-rated tires in the catalog, I don't see anything here that exceeds 75mph.

They do have inflation tables based on load, but none of them include any information on top speeds based on the same. Can you cite a source? I didn't think that was the way speed ratings worked.

The following article seems to agree with the premise that most such tires are rated @ 75mph or less, as well as indicating that exceeding the speed rating is a significant factor in blow-outs. I'm not vouching for the accuracy of the article, but it would seem to agree with the offerings I see from at least one major manufacturer:

https://www.mcall.com/news/breaking/...401-story.html

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