CalsonicSE

iTrader: (3)

N/A dynoes:

1) About a year and a half ago, I dynoed with the basic bolt-ons (CAI, y-pipe, exhaust, RT-Cat, & UDP). My best pull was 171hp/186tq.

2) Eight months ago, I dynoed again with the addition of one-step colder sparks plugs (for my nitrous). My best pull was 167.5hp/176.5tq. Compared to the previous dyno, not only did my peak hp & tq #'s drop, I lost some hp/tq at all rpms.

3) Today, I dynoed with the same basic bolt-ons, the same one-step colder spark plugs, and a VIM (aka MEVI), my best pull was 170hp/172tq. In this case, just like all other USIM/VIM dyno comparisons, I lost a bit of hp/tq up to the switchover point (about 5hp/5tq), and then I saw crazy gains afterwards with a difference of around 30hp/30tq up top!

BTW, at first I had the switchover point set at 5000rpms, but there was a slight dip in hp/tq right at that point, so I then set the switchover point to 5200rpms and everything was fine - identical numbers; no more dip in power; both hp & tq curves were smooth as butter. My conclusion: 5200rpms VIM switchover point is the way to go for N/A.


Nitrous dynoes:

4) Eight months ago (with USIM), my best nitrous pull was 267hp/331tq.

5) Today (with VIM), my best nitrous pull was 275hp/301tq. Compared to the previous dyno, I gained 8 peak hp...but lost 30 peak tq! However, don't let the numbers fool you

For nitrous dynoes, peak tq is usually achieved at lower rpms when the nitrous first hits and then decreases in a linear fashion. In lower gears, most of that initial peak tq is wasted anyway because there will be traction problems when the nitrous hits. With the VIM, although the initial dose of tq wasn't as great compared to the USIM, the tq curve did not decrease as fast nor as much. Also with the VIM, the hp curve is flat up top whereas with the USIM, power will start to drop off around 5400rpm. All in all, with the VIM, up top I saw gains of 60hp & 60tq compared to the USIM!!!!!!

Furthermore, when I did my nitrous run using my optimal N/A switchover point of 5200rpm, hp and tq would actually increase a bit at switchover. So, just for kicks I did a nitrous run with the VIM always open. Below 4800rpms, VIM-closed had a slight advantage; from 4800-5200rpms, VIM-open has a slight advantage; from 5200rpms onwards, the curves are identical. Therefore, my conclusion is since 4800rpms is where the curves start to cross, 4800rpm is probably the best VIM switchover point for nitrous. Edit: Looking at the graphs again, there is rougly a 100rpm difference between the dips/rises in power on the dyno graphs & the exact rpm I had set on the Harlan rpm switch. So, perhaps 4700rpm might be optimal for nitrous.


My Findings:
1) 5200rpm - optimal N/A VIM swithover point (I will be using this setting for daily use since I'm running N/A 99.99% of the time.
2) 4800rpm (or perhaps 4700rpm; see edit above) - optimal nitrous VIM switchover point (I will be using this setting for the track).
3) VIM/nitrous on the highway is VERY nice! I did a run from about 70-130 and the car kept going and going - no more feeling a loss of acceleration like before. It's now a VERY constant and steady pull all the way to redline. With the USIM, I used to say that nitrous wasn't really meant for highways, but the VIM has completely changed that notion.

hakk97se

I dunno what the computer said, but it felt like it was well over 80 degrees in that shop, even with the fans. Also .. that was loud Glad I could attend.

mitch33x

iTrader: (5)

Post some pics of the dyno plots!

xHypex

iTrader: (1)

Yeah I'd like to see dynos so I can compare once I get mine How much of a shot are you running right now? I would imagine that would also affect the optimum nitrous switchover point.

For the track it seems like the VI was made for boost/nitrous. The torque loss is made up in the high end (so you end up with more area under the curve), and the loss helps with off the line traction.
-hype

Y2KevSE

iTrader: (13)

I agree, it felt much hotter than 80 degrees in the shop.

IceY2K1

iTrader: (3)

Man...pictures are sure worth a thousand words.

Post those dynos please.

deezo

iTrader: (3)

Thanks for the NA info.

JAY25

iTrader: (38)

I myself have a dip @ around 5k so I am going to switch over to 5100RPMs on the RPM switch to see if that helps to straighten up the dip and keep it going up.

hokiemax

iTrader: (2)

thanks for the post. this is one of the most informative and helpful dyno posts. I dynoed with one stop colder plugs and I got just about 167 HP too. OH man if I had regular plugs I woulda gotten 170 too!!! I was wondering why I didn't get 170.. I guess the plugs were the culprit.

CalsonicSE

iTrader: (3)

Hokie - You would've gotten a lot more torque, too.


Here are the NA dynoes:
http://images.cardomain.com/member_i...67_27_full.jpg

Here are the nitrous dynoes:
http://images.cardomain.com/member_i...67_28_full.jpg