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Old 08-02-2005, 11:03 AM   #1
farrell
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Default nitrous 1/4 mile time drop?

i have a 75 shot on my car. i currently run 13.4's with out the shot. any expectations of time drop off the 1/4 mile time? thanks
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Old 08-02-2005, 03:06 PM   #2
WRXAK
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You should run it, and let us know. What type of a kit do you have? Wet or Dry? Who makes it.
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Old 08-02-2005, 07:50 PM   #3
farrell
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zex dry kit 75 shot, and i will let you know
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Old 08-02-2005, 08:24 PM   #4
regan
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I want to here your times as well
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Old 08-02-2005, 09:33 PM   #5
reddevil
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an 80 shot dropped me from 16.8 average to 14.8.
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Old 08-02-2005, 09:47 PM   #6
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If you are running 13.4's w/o the gas, I can only assume you are turbo? If this is true, you will need a wet shot or direct port. If you run 13.4 all motor thats awsome!
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Old 08-02-2005, 09:57 PM   #7
Absubtle
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I would just like to vote no on 'Dry' kits. Leaking nitrous pressure on the fuel pressure regulator is not my way of having reliable nitrous shots. Have you noticed that ZEX kits dont have filters of any kind!? If that small pin-hole in the ZEX kit clogges, your motor is FUBAR'ed, unless you realize and let off.
Wet systems are always safer, as long as you upgraded your fuel pump (in the tank).
DOn't get me wrong, I sell/install ZEX and the rest, Nitrous Express, N.O.S.
But nitrous is a cool thing, if you can resist it!

Absubtle
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Old 08-03-2005, 12:14 AM   #8
no-coast-punk
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Haha! Yay! More misconceptions about N20.

*disclaimer* I don't like nitrous. I think it's ricetastic and a way to shortcut good powertrain design. That being said...

The zex kit is a very simple system that works remarkably well. It simply increases fuel pressure based on bottle pressure. The regulator of theirs clamps down on the return line to the tank to accomplish this. It has a conventional N20 jet placed wherever you want it. There is no "pin hole" to clog or any "leaking pressure" to speak of. Contamination in the system is always installer error and will simply clog the nitrous jet. This is why filters really aren't needed. Alot of the more popular kits (like the ones you can get at pep-boys/vato zone) include filters because Ray-Ray installing a system with nothing but his favorite set of vice grips just might introduce some contamination. Even if you do get contamination, your motor will run momentarily rich... stumble and die. The nitrous user will simply have to take his sideways hat off and re-start the car.

The problem with systems like this is that nitrous distribution will always be slightly un-even between cylinders. With lower power kits this isn't a problem because they run slightly rich on all cylinders to be safe. An 80 shot is really pushing the limits of what you can get away with. You will probably end up burning the #4 cylinder over time. The problem with uneven fuel/nitrous distribution gets more pronounced on turbo cars... and if you're using a RRFPR for the turbo kit... forget about it.

I REALLY don't like the idea of wet systems on DIS ignition cars. If you are still on the nitrous and have to snap the throttle shut for some reason you can cause a pretty bad explosion in the manifold. The waste cylinder fires at the top of the exhaust stroke. There is just enough valve overlap there to allow the intake valve to be open when this happens. If you have a nice dense fuel/nitrous mixture hanging out in the manifold... intake valve open... plug fires... *boom*. Have I personally seen this happen? No... but it's a very real possibility and does happen from time to time. Wet systems will cause carbon buildup in the intake runners over time and I have also seen MAP sensors fouled over time from running wet systems. That can be obnoxious to diagnose because they will sometimes give accurate readings on a bench.

Let us know how you do at the track. Rember to keep the rev's high before hitting the button
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Old 08-03-2005, 11:16 AM   #9
farrell
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thanks for all the info. and ill let you guys know on fri night or sat morning.
(racing is on fri night)
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Old 08-03-2005, 11:34 AM   #10
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Quote:
Originally Posted by no-coast-punk
... If you are still on the nitrous and have to snap the throttle shut for some reason you can cause a pretty bad explosion in the manifold....
This is why one wires in a WOT switch. No WOT, no nitrous.
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Old 08-03-2005, 08:17 PM   #11
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wot switch or not the fuel still puddles and the nitrous backs up in the manifold. You can have a nitrous backfire if you need to peddle the car. Wet single fogger systems will have nitrous backfires no if's and's or but's.

This is really common on the GT40 intakes and such with the long runners. If you get off the gas your throttle plate closes and the fuel starts to puddle and then hits that hot cylinder when the intake overlaps. Thus creating a nice explosion that will blow the upper intake apart.
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Old 08-03-2005, 11:43 PM   #12
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Quote:
Originally Posted by O2wrx
wot switch or not the fuel still puddles and the nitrous backs up in the manifold. You can have a nitrous backfire if you need to peddle the car. Wet single fogger systems will have nitrous backfires no if's and's or but's.

This is really common on the GT40 intakes and such with the long runners. If you get off the gas your throttle plate closes and the fuel starts to puddle and then hits that hot cylinder when the intake overlaps. Thus creating a nice explosion that will blow the upper intake apart.
I'm new to the Subaru club, but I have backpedaled 10s of times on a V8 in a '70 Duster drag car. The intake is wet since I am running a carb and with a nasty cam with tons of overlap (5" Hg at 1000 RPM), there was NEVER a nitrous backfire. I have see multiple cars in the same situation with no backfires and ALL of those cars have had a WOT switch. Occasionally there is a nitrous backfire with the plastic intakes (from other manufactures) that blow up and winds up on the 'net.

I have seen one engine backfire (SAAB 1/4 miler with a ton of nitrous being shot in). Driver was doing a burnout and needed the spray to turn the tires in the water box. Driver got the tires partly heated and the turbo kicked in. Engine stalled and the driver attempted to restart (oil to the turbo) and BOOM!!!!!!!!! This car did not have a WOT switch.

Backfires "usually" happen when an engine goes lean.
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Old 08-04-2005, 03:09 AM   #13
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Read how a DIS waste spark ignition system works. The conditions that would cause a backfire are totally different than something with a distributor. Oh wait... everything works like old v8's. Backfires never ever ever happen under lean conditions. A bit of afterfire under the right circumstances maybe... detonation yes.... but no backfire.
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Old 08-04-2005, 12:05 PM   #14
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Quote:
Originally Posted by no-coast-punk
Read how a DIS waste spark ignition system works. The conditions that would cause a backfire are totally different than something with a distributor. Oh wait... everything works like old v8's. Backfires never ever ever happen under lean conditions. A bit of afterfire under the right circumstances maybe... detonation yes.... but no backfire.


Oh wait everything works like a new 'Subie'...guess U have never driven a carb car with a misadjusted choke or an accelerator enrichment not working. I must have imagined that "popping" noise coming from the air cleaner. Even an out of tune FI engine will pop thru the intake and not from overly rich condition, but a LEAN condition. Whether it be a flathead lawnmower engine or some exotic pneumatic actuated multivavle engine, there are some basic concepts that both engines have to adhere to.

I'm a little familiar with DIS with the waste spark and you sarcastically bring a good point up. Strong work.
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Old 08-04-2005, 03:32 PM   #15
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A question to no-coast-punk

Did a little research on some engines that I degreed. From the cam manufacture's card, a supercharged engine has the intake opening at 5 BTDC and more radically camed engine has the intake opening at 30 BTDC.

Since ignition timing will be between 30 to 40 BTDC at the higher RPMs, how is possible that the ignition spark can light off the intake manifold mixture with the intake valve closed?
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Old 08-04-2005, 06:31 PM   #16
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well lets see..... Subaru's are fuel injected with a throttle body. So are GT40 intake manifolds which are for the good old EFI mustang. Carbs are different, very different, the fuel wont puddle like it will on a EFI car. There are no twists, and bends and horozontal passages on Carb manifold. Im sure you were using a plate or a direct port. A plate evenly distributes the nitrous/fuel into 4 runners then they split into 2. A direct port seperates into each cylinder. Now most subaru enthusiasts use a single fogger that sprays the fuel/nitrous from ONE nozzle. This is very prone to fuel puddleing if you have to peddle the car. The boost goes to 0 when the throttle plate closes and the rest is history. But if anyone here has to peddle a subaru then well im not sure what your doing. Its not liek a rwd car that will fishtail or hang the front tires, so no peddleing is needed =).
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Old 08-04-2005, 09:23 PM   #17
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I have run a wet system and "sprayed" it at least 100 times. no backfire.
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Old 08-08-2005, 12:02 AM   #18
Joncas
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I used two 480 cc injectors in the intake manifold after the throttle body as secondary injection in my old supercharger setup. No backfires, no puddling. Even distribution. That's enought fuel for 160hp additional hp. I don't think anyone here runs a 160hp shot. No puddling, no backfires - not in our intake manifolds.
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