Engine Physics

[DRaven]

I have a 2000 5.9L with several mods. I have dynoed the truck several times through the years and just dynoed again yesterday on the "new" setup. I gained horses and lost torque.

Previous setup:
5.9L
MP PCM
CAI
180 Thermostat
PPH Headers
Fastman 52mm TB
Underdrive pulleys
MBRP 3" IN / Dual 2.25" Out
3" Catco Cat
3.55 Gears
Stock Trans
29" tall tires
150 Shot NX
-- 345 RWHP / 497 RWTQ --

New Setup added the following:
R/T 2.02 Heads with valve job and gasket matching
1.7 HS Roller Rocker
John Mercedes Cam (I have to look up the exact specs)
4.10 Gears
TransGo Shift Kit
-- NA run was 273 RWHP / 303 RWTQ --
-- 150 NX was 382 RWHP / 445 RWTQ --
This is the setup that put me in the 12's last year with 17" M&H Drag Radials

I expected the HP numbers due to the heads and cam, but I am surprised the TQ went down that much. My engine has 90K plus miles, may be getting tired. What effect do you think the gears had on the RWHP and TQ?

Also, found out that I don't have my heads torqued down as tight as I should to spray N20. They are still at the factory 95lb setting. I am using ARP head studs.

Any opinions on this result from the mods listed?

Thanks for the input guys.

[grapejuice1998]

I have a 2000 5.9L with several mods. I have dynoed the truck several times through the years and just dynoed again yesterday on the "new" setup. I gained horses and lost torque.

Previous setup:
5.9L
MP PCM
CAI
180 Thermostat
PPH Headers
Fastman 52mm TB
Underdrive pulleys
MBRP 3" IN / Dual 2.25" Out
3" Catco Cat
3.55 Gears
Stock Trans
29" tall tires
150 Shot NX
-- 345 RWHP / 497 RWTQ --

New Setup added the following:
R/T 2.02 Heads with valve job and gasket matching
1.7 HS Roller Rocker
John Mercedes Cam (I have to look up the exact specs)
4.10 Gears
TransGo Shift Kit
-- NA run was 273 RWHP / 303 RWTQ --
-- 150 NX was 382 RWHP / 445 RWTQ --
This is the setup that put me in the 12's last year with 17" M&H Drag Radials

I expected the HP numbers due to the heads and cam, but I am surprised the TQ went down that much. My engine has 90K plus miles, may be getting tired. What effect do you think the gears had on the RWHP and TQ?

Also, found out that I don't have my heads torqued down as tight as I should to spray N20. They are still at the factory 95lb setting. I am using ARP head studs.

Any opinions on this result from the mods listed?

Thanks for the input guys.

Well, since you didn't provide an n/a baseline run, I'd have to guess and say your bottle pressure, or volume, wasn't what it was when you dyno'd it last time. That's two of the biggest variables when running nitrous, pressure and volume.
You don't have to over-torque the heads to run nitrous either. That end of things should be controlled with ring gap.
Tire size and gearing can play a role as well. What about a torque converter? Have you changed that out as well?

[bad360rt]

You also need to compare both dyno graphs, and not just the peak #'s. A lot of times there are gains under the curve that don't show when you compare peak #'s.

[DRaven]

Well, since you didn't provide an n/a baseline run, I'd have to guess and say your bottle pressure, or volume, wasn't what it was when you dyno'd it last time. That's two of the biggest variables when running nitrous, pressure and volume.
You don't have to over-torque the heads to run nitrous either. That end of things should be controlled with ring gap.
Tire size and gearing can play a role as well. What about a torque converter? Have you changed that out as well?


You just pointed out a major failing of my setup. I have been looking for a "deal" on an electronic N2O pressure gauge and just need to stop being cheap and buy the damn thing. Bottle was full but somewhat cold and it was snowing all morning.

My prior NA numbers are 226 RWHP and 306 RWTQ.

The convertor is unchanged from the factory.

Thanks for the input.

[DRaven]

You also need to compare both dyno graphs, and not just the peak #'s. A lot of times there are gains under the curve that don't show when you compare peak #'s.

I'll post those in the morning. I have my old graphs in a file at my office.

I am not pissed off by the numbers, but I feel there is a good bit more to be had from this setup. I still get shit for not having an ignition system and spraying 150 on the MP PCM, but it works for me and doesn't detonate.

I do need to get a N2O gauge and hook my bottle warmer up to be more consistent. I am just being stupid on that one.

Thanks Guys.

[slammedR/T]

Bottle pressure is where the drop off came,also about the head bolt/stud torque for spray.The factory specs are fine for a little 150 shot its when you start spraying 200 or more when you need to torque the head studs/bolts more I found that out the hard way.:D



DEPUTY

[mtlcafan79]

Bottle was full but somewhat cold and it was snowing all morning....


I do need to get a N2O gauge and hook my bottle warmer up to be more consistent. I am just being stupid on that one.

Thanks Guys.

That's it right there. You really don't need a gauge as much as you need to have that heater hooked up in that kind of weather. An 1100psi bottle verses the ~600psi bottle you had will make a world of difference.