Hi guys I just wanted to thank all of you for the information i have learned being on here i don't post very much but lerk around alot,

I have had a a 92 250 4x4 CTD NV4500(get rag gernaded 3rd week of ownership) 302 000kms Since August ,I Have Put 33x 10.5 tires and 3.54 gears but always seems to rev super high on the hwy at 65mph its at 2400 and about 650-700 degrees empty it that normal???

The only thing I have done to the pump is turned it up 1 1/2 turns and backed the smoke screw out a few turns to get rid of smoking out all that is behind me ,The truck feels alot stronger and I have seen up to 16psi Boost, the truck has always reved high and had higher egts at 65-70 was wondering what could be killing its top end with a .73 final ratio and 3.54 Its just not right could it be stuggling for air???injectors???theres a K and N on it. or plugged exahust (stock ) other then super slow hwy traveling its always getting 21 mpg and never uses any oil


also when you back off the smoke screw should it be raising or lowering egt's its backed out pretty far right now


Thanks guys any help is great

 

Nice truck, at 2400rpms with the 33" tires and 3.54 axles you should be doing around 89mph. Id verify your speed with a gps. Maybe your clutch isnt fully engaging or your axle ratios maybe a little taller than you thought? The egts dont seem to be that far off.

 

Egt's are a little warm, but there's definately something that doesn't add up with the rpm's. I'd agree with ares, and go so far as to say that the clutch is my #1 suspect. If you put the gears and tires in yourself, then you're probably dead on about your ratios.

Have you had any similar symptoms in lower gears, or pulling loads? Try it out. If it's not slipping on this type of work, then you have wonder what's up with 5 th gear rather than the clutch. Unfortunately I'm not familiar enough with the nv4500 to know if there's any common problems with it.

I'm not much of a help on this one, but that's a great looking truck..

 

Definatly them numbers dont add up. You must have 4.10s. do a search for rpm calculator and you can figure it yourself. I think 4wheel parts has a calc on line.

 

Thanks guys i dont have any pics with the new rims yet i will try and post them

Its defintly 3.54s it has the tags on the diff and on the case and the trans is a full rebuild with 4000kms on it, and feels the same as the getrag..the clutch is like new and feels awsome

the truck seems to fall flat on its face though every shift unless it is right matted and spooled up. Im really not sure whats the deal is its very strange

 

Stock muffler? The muffler may be clogged or restricting flow? Check the air tube from the intake to the AFC on the pump with soapy water and look for cracks. Check the intercooler for leaks and the gasket tube connection.

I hope this helps.

 

Nice looking rig.

I agree with "ares". The 65 mph at 2400 rpm with 33 inch tires does not compute. According to my calculations you should be at 86 mph.

 

I think you are the first guy do do 65mph on the highway in Edmonton. I have been there and have a hard time keeping up to everybody at 75mph. Check it with GPS as something does not add up. Very clean truck for alberta,nice.

 

Your truck really looks great. Is your tach a factory unit or aftermarket? it might out of calibration for the RPM vs speed. Can happen with the ones that use the alternator and the pulley ratio is not right. Also I would drill and tap a port in the exhaust and check for excessive back pressure with a U-tube. You say "you have seen up to 16 PSI boost" Are you sure your turbo is spooling? seems kinda low. I see 20-25 @WOT with no pump mods. Restriction would cause low boost indications depending on how bad, since its operation is perpetual also air in fuel, low fuel pressure could cause it to flatten out. Just a thought. Good Luck. Jim.

 

Have you changed the turbo housing? I changed my housing and turned the pump up and put a straight thru ehaust on and it made the truck run great.

When the truck was stock if I had any weight in the truck the shift from 2nd to3rd was so bad I almost had to downshift back to 2nd. After the mods it is no problem.

Dean

 

Thanks guys

Exactly my point BIGBADBOB I cant keep up with traffic around here drives me nuts !!

DeanM still has stock exh and housing which i really would like to change


The truck has an autometer tach with alternator probe, It could be out of calibration but not too much, when it reads 2400 @ 65 with 3pi of boost and i floor it it will pull to around 3100 but it falls on its face after that so i assume its pretty close.


any more ideas or tests thanks

 

No more ideas??

 

I say to check your tach..you say you have not touched the gov screw but if you can get to 3100 then something is wrong.
My guess is that your tach is off around 400 rpm.
I have the same tire dia and diff ratio and I'm doing about 2000 rpm at about 65.
Jay

 

for got to say the governer screw is removed, it is just very strange the truck even gets better milage in the city then the hwy its crazy

 

As other fellows have said in this thread before: It is physically impossible for you to have 3.54 axle ratios, a .73 OD ratio, 33" tires, and have the engine running at 2400rpm going 65mph. One (or more) of those numbers MUST be wrong, or your clutch is slipping so badly that it would be burned out by now.

16psi of manifold pressure is normal for a stock '92 250 with a 21cm turbine housing -- a tad low if you have the 18cm housing. A smaller housing would lower your egt's.

From the factory, the engine is set up so that it does not really have much torque until you get up to 1700rpm. This means that you really have to wind the engine out before you shift, as the gear ratios are slightly too wide.

Running the pump without the governor screw is not good for it -- it forces parts inside the pump to be the throttle stop that are not designed for the task.

The amount of fuel a diesel burns is proportioanl to the amount of power it is putting out. Unless you spend a lot of time stopped and idling, it is normal to get as good or better milage at more moderate city speeds.

I think that you have something wrong with your governor, though it is *possible* that you have a clogged fuel filter, fuel line, or bad lift pump.

Get your tachometer fixed, and see what the max rpm really is, and then work from there.

Good luck,

Alec