NITROUS OXIDE ( nos / n2o ) advice forum

MG,

What changes did you make to your carb to get her back up to snuff?

Hi Chev!

I fitted size 80 jets in the seconday plate. Increased my secondary shooter to size 44 and re fitted the Orange pump cams. This was after making sure I had my holes / slots looking square under the butterflies.

She did splutter a bit at part throttle in the pits so I took the primary jets down to size 72 (I think).
This combo seems to make her happy.

Heres the first run with the spider having 100 gas jets and 150 fuel jets. Just As I wanted, slow and smoky. This was after many many hours of testing and repairing a broken brake pipe. Dont ask!! I was my own fault

http://www.youtube.com/watch?v=UERr7xAhBsY


PS
Thanks to Richard BMW840 for putting the vid up.

Great, good news. Glad you got it sorted. I'm jealous you guys are already racing. The nearest track (500kms away) opens the last weekend in may

Bummer!!
500 kms to go racing eek!!
I'm lucky. Santapod only takes me 40 mins while towing the trailer

Thanks for the advice Chev! I'll be back with more questions if I encounter any more carb issue's when I get back down to last years times.

Regards
Perry

Glad I could help. You'll geta chance to return the favor, when i start asking about your spider plate tune up, as i'm running one. I was running 100hp fixed hit last year, but i'm moving my way up to 300-350 on the progessive this year on my new motor.

Sounds good to me Chev!

Mine is on the dyno for AFR checks in the morning to see how the carb is running. I know this isnt real world stuff because I still want to get jet extension tubes. But as the car does not go anywhere I will be happy that fuel flow will be stable.
Then a second run with a 200shot to see if I have got the fuel to nitrous ratio somewhere in the ballpark

Then I'll decide on subsequent passes with more juice if I have time. I know what fuel and nitrous I flow through the spider now, so I reasonably confident that at 200 and above the ratio will remain fairly linear. Down at the 25-125 shot of fuel the delivery is very rich.

The main thing I want to see is how the power and torque from the spider differ from the old crossfire plate.

sounds good. Keep me posted on the dyno results

Pel ,Careful on the rear tyres this time ,have a good day

Austin

Dont worry Austin!!

I wont get carried away like last time and do 7 back to back dyno pulls mate
I've still got the scars from the flying rubber liquid

I'll just do one nasp, and then one to replicate pass 3 from last Sunday at the track with 250 fuel and 200 gas. Then she can come off and cool while the others get on the rollers. We have 15 cars to get through in 7-8 hours. Luckily, at least half of them will only want one pull.
My last pull will be the same as run 4 from the track with 250 fuel and 225 of gas. I'm hoping to hit peak power, and then adjust timing on the fly to see if some more retard makes it better or worse on the graph??

This will be the second run with the epoxy repair to the engine block. Should be fun

What fuel pressure are you running MG? That seems like a pretty rich tune. Last year a ran 200 N2O jet with 2x80 fuel, and it still looked on the rich side with 8psi flowing.

Was this with the Spider??

Perry any theroy why you should be very rich on jets upto 125 bhp yet over that jet size you expect it to be better and more stable ?? is your fule delivery some how taloyoring off from even tho you have the requiered flow in total

Did you get any more info on why pure nitrous killed the engin stone cold dead at very low jet with no added fule

Did i read right at 5 psi you got 300+ ml yet at 10 psi you only flowed 10ml more

You bet, thats with the 4150 spider plate. I have a thread on my car named spider plate on forged 383 in the advanced section. It has pictures of my fuel system and plate set up. It has a pair of 350hp pulsoids y'd at the out lets. The nitrous is jetted at the outlet, while the fuel has 2 jets. one at the end of each 5mm line. I'm just goin by reading the plugs at the time. This year i'll be doing that plus logging data with my 2channel wideband set up for more diffinitive info. I have 400, 600, and 700 jets on their way to me to test the kit out on the engine dyno in a couple weeks

Tezz!
Fuel flow tests showed 90ml of fuel with 50 jets and 340ml of fuel with 300 jets.
Pressure from 6 to 10 psi only made a small difference?

So with a 50 shot I flowed nearly double. But with a 300 shot I flowed only about 15% more.

Fuel pressure was stable on both tests!

Remind me exactly what fule set up you have pipes pump reg ect

So from what iv read and you told me you getting double the amount of fule on 50 jet , slight rich on 200 and by looks of engin a lean run or perfect on 300 jet , which from you statics test results small jets pig rich and run like a dog you fitted bigger jet set and and rpm rose and at 200 bhp you got in a good altho very rich run on track which kind of eccos what quickchevy just said rich setting on the 300 jets before blow car was going great

i know what i would do fit 100 jets on dyno get a good A/F fitt 200 same ratio and see what happens to the A/F

sorry trying to make sence of this so at 50 jet you need 2n 1 fule at 200 2n 1.8 fule and at 300 2n 2.3 fuel asuming it was a lean burn and at 300 you at limit of pulsiod flow so could be some varibles depending on what effect Gs hade on fule in the run , and at 300 jets going from 5 psi to 10 psi had almost no effect lol that makes no sence

could this be a fule delivery/ design problem rather than just psi as your jets get bigger your delivery rate is droping off m yet the nitrous will almost be constant

But the pure nitrous killing engin i still dont get at all unless it effecting the Carb some how but im not sure thats linked to your fule delivey problem i think thats another issue