car goes duh on the hit

Went to the track this weekend and car is doing some funky jazz when the nitrous hits...

When the nitrous hits (press button) car falls on it's face. Then just picks up and jams out once that initial duh is done...

car is a 383 stroker lt4's comp 336/342 36lb/hr injectors..stock pump..100 shot..dual nozzle setup, #40 jet nitrous #28 jet fuel

i just ordered the race tronix 255 lph fuel setup from thunder, but am curious if some people ahve other opinions..

p.s. the car went 11.67@122.87 this weekend even being jacked on the hit...

what rpm are you spraying at do you have a fp gauge and nitrous pressure gauge? It important to evaluate these #'s first

Originally posted by n20ta2
what rpm are you spraying at do you have a fp gauge and nitrous pressure gauge? It important to evaluate these #'s first
I have tried spraying at 3000, 3500, 4000, doesnt matter still does it.

I don't have a fuel pressure gauge as of yet, but just ordered one today. nitrous pressure is at 900-1200 at all times.

*Added info*
nitrous bottle closed, car on, arm nitrous system, activate wot switch and motor bogs then goes...makes me think car is losing fuel pressure due to volume demand change on hit...

do you have a purge setup? if not that could be it.

sounds like it is partially a fuel pressure issue. what was the bottle pressure for the runs?

Originally posted by 68maro
do you have a purge setup? if not that could be it. Yes it does have a purge.

Originally posted by RacinLT1
sounds like it is partially a fuel pressure issue. what was the bottle pressure for the runs? 900-1200

nitrous bottle closed, car on, arm nitrous system, activate wot
you say nitrous bottle closed? if thats' true thn all your spraying is fuel.? is that a typo? if not there is your problem:confused:

I was doing that as a test, just to see what would happen if the bottle was closed. In my past experience the motor should still rev, and after that initial duh on the hit it still does.

With the bottle open and at good pressure it still goes duh on the hit...then just picks up and takes off...

I'm gonna put this new fuel pump then see what it does, if it doesn't fix it I'll do some data logging and see what the o2's go to when the bottle hits...

I know you have a purge....but it still sounds to me like your initial "HIT" is all fuel and no nitrous. Are you running the lines close to exhaust at all....???

Actually, where the nitrous feed line cmoes through the firewall it right next to the last primary on the header. Could this be my problem? Can I get away with heat shielding wrap of some sort?

I just read this morning where a guy was having the same problem as you. His feed line was a good 6" away from his header and still causing the "DUUUHHH". He relocated the feed line and insulated it and the "duhhhh" was cured.

Could very well be your problem.

Do you have a fuel pressure switch? Are you running the nitrous off the same fuel pump as the motor?

Originally posted by BIGBADBOWTIE
I just read this morning where a guy was having the same problem as you. His feed line was a good 6" away from his header and still causing the "DUUUHHH". He relocated the feed line and insulated it and the "duhhhh" was cured.

Could very well be your problem. Pictures or ideas of where the feed line could be run, this was the only grommet I saw in the firewall... I guess I could get out the drill if nothing else.

Maybe there is some part of this I don't understand but why would this make it go duh??

What I think is happening is the heat is vaporizing the nitrous in the line and when you hit the "go" button your getting all that extra fuel and no "go" gas. The abundance of fuel is causing it to bog...or in your case"DUUUHHHH". Once the nitrous line gets purged and has continous flow is when its running like as BIG dog. Thats my thought......

Originally posted by 12Second3rdgen
Do you have a fuel pressure switch? Are you running the nitrous off the same fuel pump as the motor? No fuel pressure switch, and yes it is the same pump as the motor.

Originally posted by BIGBADBOWTIE
What I think is happening is the heat is vaporizing the nitrous in the line and when you hit the "go" button your getting all that extra fuel and no "go" gas. The abundance of fuel is causing it to bog...or in your case"DUUUHHHH". Once the nitrous line gets purged and has continous flow is when its running like as BIG dog. Thats my thought...... Makes sense to me. I think this will work to test if this is truly the problem. Hold the purge open until the nitrous hits, if the car goes then sweet I just need to move the nitrous line. If it still bogs, then time to continue chasing the problem.

PROBLEM SOLVED....

Fuel pressure gauge revealed 28 psi at WOT on motor and 19 on nitrous...

Bowing down thanking lord for saving motor...

inserted walbro 255lph intank, solid 41 psi at all times,
heat wrapped nitrous line,
fixed purge to flow more nitrous...

car htis solid and hard from first punch..

Thanks for the input

Glad to hear the problem is fixed.

Props to all who assisted with the troubleshooting.

Good to hear. Now put the big pills in......see how she goes!!!

kindaslo,
Just curious, I have a simular set-up and wanted to know what your times are on the motor. My best is a 12.4 @ 110mph on a crappy Hawaii track, but that time seems alittle slow to me.

Thanks
Brian