4bt power question

[LAlessi]

my cpl 858 105hp motor is up and running in the m715



heres the deal. nv4500 transmission with . 73 od. 4. 56 gears on 38. 7 tires, 6500 lbs, poor aerodynamics



1st through 4th fine. i take 4th to 64 mph and 5th stops accelerating at 67. 8, pedal to the floor

so is it a

lack of hp?

lack of tq?

lack of gears?

aerodynamic drag?



id like to hit 70 or so..... but in the interest of fuel economy i like the lower rpm at 65.



all speeds are gps



would turning the pump up help any of the top speed? or change gears, assuming i cannot live with it?

 

[bmoeller]

What is the tach reading at top speed? Are you out of RPMs or power(both)?

 

[SRadke]

Sounds like you need more power! If I'm calculating your ratios right in my head you've got rpm to give but you can't get there.



-Scott

 

[bgilbert]

Are you getting full throttle travel? Linkage might not be adjusted, have someone in drivers seat put throttle to the floor, see if throttle at the pump is going full forward or hitting the stop at WOT. You can try www.randysringandpinion.com. It has rpm, mph ratios calculators. When I put in your numbers it showed an rpm of like 1900, I know the 6BT ve pump is good for at least 2600 rpm. Bill

 

[JLEONARD]

I'd turn up the governor a tad. The older marine 4bts (155 hp)were rated at 2800, so a couple hundred more won't hurt.

 

[fox]

What is the EGT's max? Put a pyro on it first. Then turn that pump up till you can get it to 1200* pre-turbo.

You may want to bump the timing a little also.



My 4bt is in an old bread truck and it was set last year to not exceed 1200 and it would push the truck to 75 and you are more arodiamic!!!



I turned it down because the guys driving it kept putting clutches in the junk pile.

 

[LAlessi]

tach i dont have a tach output on the alt. BUT i can hear its nowhere near the 2500 max



gears i should be at 1900 rpm at 65. it sounds close, so im missing out on 600 rpm somewhere



throttle i have full travel, as i get to my mathmatically highest speeds in 1st through 4th gears. the throttle pulls back till it stops mechanically, but does not pull the final inch or so that the overtravel spring allows on the pump. do i need it to? does that make sense?



pyro i need to buy one, i guess ill order one today

 

[fox]

You can also give it more throttle travel for more rpm. It is a screw adjustment.

It may be best to call Piers and get an exchange pump from them. Just tell them what you want it to do.

Are you getting any smoke?

you may benefit from a exhaust housing change also.



It NEVER quits!!!

 

[LAlessi]

fox i emailed you... . ill pm you too... .

 

[britannic]

Looks like you're hitting the governor's defuel curve as it heads toward the governed max. Along with the weight, aerodynamics etc. , you're going to need to tweak the pump for HP/tq gains.

 

[bgilbert]

On the throttle travel -another inch or so, I'd say yes. On mine, I get full throttle from the cab, the same if I was to be standing at the pump and pull on the throttle wide open. As to how much more rpm its get you, dont know that one. Bill

 

[randyn]

Hey Guys!



I have an 18 yr old son who has fallen in love w/ my new/first '03 Cummins & he wants to put a 4BT in my old '84 Toyota Landcruiser I gave him. It has Chev small block now w/700R4. Would this swap make sense from a mechanical ease/transmission use/daily driver/week-end trail, perspective? I'm sure the cost wouldn't make sense because the current set up is paid for. Can these engines be found/bought reasonable? Source?



Thanks for any info!



RandyN