Pathetic dyno results, NA vs nitrous

[fiveohpatrol]

I'll let the graph speak for itself.

first pass was at 16deg initial timing, and without the nitrous. I was hoping to see it in the 260 range, but oh well. Also it was way lean on this pass, well over 14:1. So I bumped the fuel pressure up about 2-3psi

2nd pass, timing was the same, this time with the nitrous on. The "100"hp jets were in, and it got no where near 100hp gain, only about 66, but the torque did jump nicely. Wideband showed good AF ratio's, it hovered right around 12:1

3rd pass, same jets, but the timing was brought down to 12deg initial. It picked up a tad but not as much as i'd like.

I didnt have a bottle pressure gage at the time of the dyno runs, but the bottle was all the way full and it was pretty hot out, so it had to have pretty good pressure in it.

Anyone else ever had a nitrous hp gain fall well short on the dyno of what it is supposed to be?

[Unit 5302]

14:1 is not horribly lean. It's where it should be under normal driving conditions. The 12:1 is conservative, anything lower than that and you'll begin to lose power. 14.7:1 is the optimal air fuel ratio, 12.6:1 is the most powerful, 15.4:1 is supposedly the most economical. All that is mathematical though, so it's not necessarily perfect in real world applications. Actually, since you're not specific in your a/f ratio info, it's hard to tell where you are. 12.1:1 and 12.9:1 are all 12:1 but are pretty large in difference.

You're making 300hp N/A, and 380hp on the N20. You should never expect to gain a full 100hp from a 100shot if you're tuned reasonably. Running the N20, you should be tuned more conservative, and because of that, it will take a few ponies away.

You're looking at rwhp numbers, which are not good at showing your true power gain. 66rwhp = 80hp at the crank. To find out the gain on a 5spd, you should be dividing by .83 or so, as you'll lose about 17% of your power through the driveline.

[ultraflo]

Originally posted by fiveohpatrol
Anyone else ever had a nitrous hp gain fall well short on the dyno of what it is supposed to be?

I've read/heard that some nitrous companies rate the HP gains on thier systems according to FWHP (NOS for example), while others rate the HP according to RWHP gains (NX)... I've never done any nitrous tuning on the dyno... I tune the nitrous system at the drag strip for track conditions and weather.

What was your fuel pressure before you added the 2-3 psi?

And you should make it a priority to get a bottle psi gauge in order to maintain consistency and to accurately log your results in reference to a/f ratio compared to bottle psi... the higher the nitrous psi, the leaner it will run. A bottle heater is a must IMO... again, to maintain consistency.

According to my calculations... I'm getting a full 200hp gain from the wet kit currently being used on my 'stang... to the wheels, that is. Through tuning you'll find your HP gains... I prefer the drag strip (and reading plugs) when it comes to tuning nitrous oxide.

[fiveohpatrol]

well I was figuring it would probably be a flywheel hp gain, but even at that, I would have seen atleast 75-80 at the wheels. I put a gage on it today, which was about the same temp outside, so the pressure would be close to the same it was yesterday. The pressure was about 850psi, which would explain a small loss in power, but would it explain a whole 20hp difference?

I did a search over on the corral and found a guy with a similar combo to mine, with the same NOS 5115 kit as I have. But he had the 75hp jets in. His NA numbers were almost the same as mine, and he actually made more power on the 75shot than I did with the "100" shot. He went from 240hp/286ft lb to 314hp/386ft lb.

heres a link to that thread http://www.corral.net/forums/showthr...t=nitrous+dyno

Bottle heater is next on my list for sure

[fiveohpatrol]

pressure on the first run was 43psi, then i put it up to 46 for the 2nd and 3rd pulls

[ultraflo]

I'd try 42 psi fuel, 950-1000 psi nitrous, and 12 deg. initial... and you already run a colder plug, right? See what that does for you... you might just find that 20hp you're looking for...

The low bottle psi coupled with the high fuel psi could explain the rich condition that would cause a loss in power... what is your fuel psi when spraying? Isn't it supposed to be around 80 psi on a dry kit?

Have you consulted with the guy that you linked to from the corral? If you do another dyno session, try the 75hp jets and see what happens... good luck

[fiveohpatrol]

double post

[fiveohpatrol]

I'm running autolite 24's

I did PM that guy from the corral, and he said his bottle pressure was 950psi.

I doubt I'll be doing any more dyno testing for a while. The only reason I did it this time was because I got 3 wideband pulls for $45. I really only wanted to see what RPM i was making peak power at. and it turns out I have been shifting way too late. I was shifting at 57-5800 and I made peak power at 5200 on and off the nitrous. So bringing the shift points down to 5400 or so should give me a little quicker ET's


I'll be goin to an 1/8th mile track this friday, where I'll supposedly be able to get alot of runs. So hopefully I can get it in better tune while I'm there.

I just checked out my AF graph, and noticed that it actually went a little too rich after I bumped the pressure up. I'll try 44psi and see how that goes.

Yes the dry kit is supposed to shoot the pressure up to 80psi, but the gage is under the hood and I wasnt reading it while it was on the dyno.