Engine/Transmission (1998.5 - 2002) Had my truck Dynoed why is my boost 6psi less on the dyno

[Huff N Puff]

At WOT on the road I can consistently get 46psi of boost,while on the Dyno jet the most boost I can get is 40psi If its not holding the truck back to attain max boost am I getting an accurate horsepower reading. Would appreciate any input. Merv

 

[LSMITH]

HP is close. You don't get the boost on the dyno because the load on the engine is not as large as it is on the street.

 

[fj40charles]

I agree with Lsmith. You need more load and the dynojet will not load the truck like driving it on the street.



charles

 

[Deezul1]

Thats true about dyno load, the first time I dynoed was with a stock clutch that slipped pretty bad on the street but I was told it wouldnt on the dyno and they were right, it didnt slip a lick on the rollers. And did 389 HP.

 

[Snow man]

I couldnt hti over 47psi on the dyno,but hit 52 o nthe street,peak boost. Like was said alrady,not enough load to get full boost.

 

[Sled Puller]

Dyno Jets are not designed for our trucks, fun to play with, but not very accurate.



If you have any size turbo at all, you need to "spike" or "manipulate" the dyno, to put big numbers up.



There are some real Pros at this, but I am learning!!! I can jump 60 hp, by fooling around on it, imagine if I knew what I was doing.



I did hit max boost, but you could still tell that the engine wasn't loaded, it was just playing on there, not working it at all.

 

[C Schomer]

I had the same problem on a Mustang dyno. I new right away something was fishy. I talking to the operator about the different kind of runs they can do, I had him do a "limited speed" run. He set a speed and the dyno won't let the truck excede it. That maxxed it out and hp went up over 70hp, tq about 275. Craig

 

[Huff N Puff]

Is it more accurate than a dyno if I figure HP with weight and trap speed in the 1\4m

If it is, does any one know what a 2001 4x4 quad cab sht. bed weighs. My trap speed was 101. 5mph

 

[Hohn]

HUFFN: My QC SB weighs 6810 pounds with a full tank and me not in it. I (driver lard butt) add 200#, plus I have about 100 pounds of crap in the cab and bed, so I am over 7100 day to day.



Empty truck with just full tank of fuel (no tools and crap)- 6810# (2710 rear axle, 4100 front if you care)



Hohn

 

[CUMINNTSTRKN]

Originally posted by Sled Puller

Dyno Jets are not designed for our trucks, fun to play with, but not very accurate.



If you have any size turbo at all, you need to "spike" or "manipulate" the dyno, to put big numbers up.



There are some real Pros at this, but I am learning!!! I can jump 60 hp, by fooling around on it, imagine if I knew what I was doing.



I did hit max boost, but you could still tell that the engine wasn't loaded, it was just playing on there, not working it at all.

gene



you always talk about spiking a dyno-jet? maybe i'm new to this but i have never seen a spiked dyno-jet graph? they all have a rise and a peak and a decline. do you mean using your brakes while on the dyno? if so i have tried that and it doesn't do squat. all the graphs i have ever posted have been without the brakes. the stick guys have some advantage on the dj becuase they can start there run at 1200rpm. the lowest i can get wot in 4th gear is 1800rpm. all this really changes is at what rpm peak hp is reached. the stick guys will be lower in the rpm range.



the dyno-jet does not load the trucks the same as the road, but i will put one up against any other dyno for repeatablity. i have made 5 runs in a row without the hp changing more than 2rwhp. the same can't be said for any type of loading dyno. the more you run them the warmer they get, and the results start to change.

 

[propuller]

running a stock hx-40 to 46 psi will eventualy destroy it. these turbos shouldnt exceed 38 psi. the diesel dynamics hx-40 is stock at least thats what they told me when i bought mine. (i no longer own it,bought a b-1). i also ran dd 3 & a drag comp & mine was set up to hit a max psi of 39. kurt.

 

[KLockliear]

Originally posted by propuller

the diesel dynamics hx-40 is stock at least thats what they told me when i bought mine

Musta been quite some time ago (did you have a welded closed wastegate?). They aren't stock anymore.

 

[propuller]

i bought it last summer & no it did not have a closed wastegate. what are you doing to them now is is on the order of the piers 40. can it handle 46 psi of boost?kurt.

 

[KLockliear]

Our MB100 setup is wastegated not to exceed 40psi. That is the safe limit for those turbos.