Question about horsepower

[MO Fred]

I have a 1990 6cy CTA 8.3 cummins rated at 250 Hp. I have seen posts where others with the same engine, maybe not the same year, have rated horsepower at 300 or 325 hp. My question is how do they have that much more horsepower than mine? What do I need to do to make mine higher?

Mo Fred

[JohnBoyToo]

tuning and year over year upgrades in exhaust, intake, etc...

first thing to do is make sure your current engine is tuned as well as it can be,
then you could look into more free flowing muffler/exhaust systems that don't drone, air filter updates/intakes, and tuning that would make you engine parameters more efficient...

you actually MAY get more horsepower AND improved mpg (if you don't use all that new hp all the time )

[BFlinn181]

You need to check with transmission manufacturer to be sure it can handle more horsepower and torque. It's not too difficult to increase torque and hp (torque is more important) on a mechanical Cummins, but if the transmission can't handle the increase it can get real expensive quickly. If it's an Allison, go to their website with your serial number and you can get all the information on your transmission.

[Borderbuster]

My 1993 8.3 started out as a 250hp. Original owner didn't think it was enough and had it converted by Cummins to 300hp, cost was $2869 in 1994. A few years later he didn't think it was enough so had a Banks modification done raising it to 360hp. This set him back another $1942 in 1998.

Since I have never driven a 250 hp version, I don't know what kind of performance our 30,000 pound motorhome would have with a 250. What I can say is that the modified 8.3 will pull any of our Washington cascade passes at the legal speed limit and then some.

I also have the original owners fuel costs and mileage figures and there is no change in miles per gallon from before modification to after modification. I have no idea how the original owner drove the vehicle but he managed 9.5mpg and that is exactly what I get at highway speeds of 60-65mph.

I should mention that our MH has the Allison World 6 speed, which supposedly can handle more than 1000 pounds of torque, and that is almost what the modified 8.3 puts out.

I have the invoices that detail the work done, and most of the mods were to the injection pump, injectors, related fuel transfer components, intake manifolds and turbocharger. More fuel and higher boost pressures equal more HP.

[MO Fred]

Thanks Randy! I have a 4 speed Allison trans. I will weigh some options to see if it's feasible to raise the horsepower. My powertrain is okay but it Slows way down going up steep inclines and the transmission starts to overheat. Was thinking that adding horsepower would help solve this problem.

Mo Fred
1990 Barth, Regency

[NHRA225]

From experience !
Anytime you install power adders IE: Fuel plate changes you will also need to add an EGT monitor of some type. Although you will see and feel noticeable increases in power -- your temp gauge and EGT's will also increase and need to be managed for your driving style.

[Dutch Star David]

Originally Posted by MO Fred

Thanks Randy! I have a 4 speed Allison trans. I will weigh some options to see if it's feasible to raise the horsepower. My powertrain is okay but it Slows way down going up steep inclines and the transmission starts to overheat. Was thinking that adding horsepower would help solve this problem.

Mo Fred
1990 Barth, Regency

I doubt that more HP will help with transmission cooling. I'd look into an add-on transmission cooler, or if you already have one, a larger one.

[Skip426]

Originally Posted by MO Fred

Thanks Randy! I have a 4 speed Allison trans. I will weigh some options to see if it's feasible to raise the horsepower. My powertrain is okay but it Slows way down going up steep inclines and the transmission starts to overheat. Was thinking that adding horsepower would help solve this problem.

Mo Fred
1990 Barth, Regency

The 4 speed trans will definitely limit your options, and adding power will not (JMHO) help if you have a trans overheat condition.
How hot is the trans getting ? Service records ? Fluid condition ? Burnt smell?
To set up a signature line ; so you don't have to type your coach info in with every post, Go to your " User CP" and on the left side "Edit Signature" you can put the info in and have it automatically appear below your posts.

[Mekanic]

Originally Posted by MO Fred

Thanks Randy! I have a 4 speed Allison trans. I will weigh some options to see if it's feasible to raise the horsepower. My powertrain is okay but it Slows way down going up steep inclines and the transmission starts to overheat. Was thinking that adding horsepower would help solve this problem.

Mo Fred
1990 Barth, Regency

More horsepower is gained by burning more fuel. More Fuel = More Heat in the engine. More heat of course to make it go, more heat out the Exh, and more heat output at the radiator.
Your Trans is more than likely cooled in the bottom half of the radiator.

I should add if your trans is slipping slippage adds,........you guessed it.... HEAT.

[MO Fred]

The transmission stays cool and never warms up during normal driving. It starts to warm up when going up and down several steep hills. it has gotten as high high as 200° For a short period of time. My mechanic changes the transmission fluid and filters when needed. The previous owner added some additional fans with a toggle switch on the dash to cool the transmission when I gets that hot. Other than getting hot on rare occasions, the transmission runs like a champ. Thanks Skip for the tip on editing my signature.

[Skip426]

My 99 Allison transmission manual , list trans temps as follows ; for an overheat condition. Depending on the location of the trans temp sensor.
I'm not sure where your sensor is.
Sensor in trans sump 250 f.
Sensor in cooler line ( trans fluid to cooler ) 300f
These numbers are for regular trans fluid , if you have upgraded to Allison's new Transyd fluid I think you can add 25 degrees; to each figure; , before the trans is considered overheated.
New numbers are on the Allison web site , I'll confirm ASAP.

[sc3283]

summer weather combined will hilly terrain..200 is not uncommon for trans temps...certainly nothing to worry about

[MO Fred]

Really glad to know 200 plus temps are not too dangerous. Hoping to get another 200k miles out of my cummins/Allison combo. Have 104k on it now. Also, I did an edit on my signature and hope it shows up below.

[Skip426]

Looking good and you can change/ upgrade it any time .

Sorry I haven't got back with the Transyd , fluid temps , Allison changed the web page and I haven't found them yet.