Still surging!!
12-04-2003, 09:12 PM
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Still surging!! Ok ill start from the top. I get surge in the high rpm's 5500+. The surge is HARD spikes in the graph. Up and down in sometimes 50HP jumps and SHARP edges. Telling me (I ASSume) it is an ignition problem (not firing) only on the 150 shot. This is a heads/cam car. 125 shot and under runs fine and smooth. Kit is a single nozzle NX WET kit. With MDS window switch at 3000 and 6400 pills. No fuel pressure safety sw.
Things I have checked and I THINK eliminated...
1) On the dyno with a wide band fuel is steady through the surge about 11.8:1. A little rich I know but leaner fuel jet made less TQ and still surges. So I think fuel can be ruled out. I have a walbro 340 intank.
2) KR. Yes I have the dreaded unknown intermittent KR problem. Sometimes ill get a couple deg. Some times not. It does this on motor also. No change with the spray. During one surge run while I was watching it I was getting 2 deg. Steady across the rpm band. (while it was surging) I was also on 93 octane.
Max timing on my nitrous tune is 26*
3) Plugs and gap. Plugs are NGK TR6. Fresh change. Same on old or new plugs. Tried everything from .38 to .32 on the gap with the exact same result. They are at .36 now. Changed the wires for the heck of it with no positive results.
4) Read about belt slipping issues on other car(s). So I know have a solid billet tensioner. Same surge.
5) Thought about possible solenoid grounds and such. But like I said on the 125 shot or less all is good. Would the 150 shot make that much difference in voltage/grounds at the solenoids? Is so if my Nitrous sol. was chattering could it make that hard of a spike? I thought about hooking a test light in line on the sol. to see if they keep voltage during the surge?
6) Botle pressure was about 1000. Same surge at 900 on my first run. Nitrous filter is clean. Bottle mounted properly. Has had this problem for a while so I can rule out "bad fill"
So what next? I THINK i have for some reason an ignition failure. How would i find it? A-tap and look for current missfires? Could i still be blowing out the spark at .32 gap? I would like to think .36 is fine.
Dyno #'s are in sig. The HP was at 5200. After that is started surging and falling on it's face. I would like to get a little more out of it but i cant if it wont hold steady.
Things I have checked and I THINK eliminated...
1) On the dyno with a wide band fuel is steady through the surge about 11.8:1. A little rich I know but leaner fuel jet made less TQ and still surges. So I think fuel can be ruled out. I have a walbro 340 intank.
2) KR. Yes I have the dreaded unknown intermittent KR problem. Sometimes ill get a couple deg. Some times not. It does this on motor also. No change with the spray. During one surge run while I was watching it I was getting 2 deg. Steady across the rpm band. (while it was surging) I was also on 93 octane.
Max timing on my nitrous tune is 26*
3) Plugs and gap. Plugs are NGK TR6. Fresh change. Same on old or new plugs. Tried everything from .38 to .32 on the gap with the exact same result. They are at .36 now. Changed the wires for the heck of it with no positive results.
4) Read about belt slipping issues on other car(s). So I know have a solid billet tensioner. Same surge.
5) Thought about possible solenoid grounds and such. But like I said on the 125 shot or less all is good. Would the 150 shot make that much difference in voltage/grounds at the solenoids? Is so if my Nitrous sol. was chattering could it make that hard of a spike? I thought about hooking a test light in line on the sol. to see if they keep voltage during the surge?
6) Botle pressure was about 1000. Same surge at 900 on my first run. Nitrous filter is clean. Bottle mounted properly. Has had this problem for a while so I can rule out "bad fill"
So what next? I THINK i have for some reason an ignition failure. How would i find it? A-tap and look for current missfires? Could i still be blowing out the spark at .32 gap? I would like to think .36 is fine.
Dyno #'s are in sig. The HP was at 5200. After that is started surging and falling on it's face. I would like to get a little more out of it but i cant if it wont hold steady.
12-04-2003, 11:00 PM
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Tim, three things I have related to surging:
1) as you said ignition, wrong plug/gap
2) clogged nitrous/line/filter
3) not enough fuel, THIS WILL cause a car to surge. When I blew my fuel line out, I was running 175 wet shot, twice if not more, without the fuel theres no fire. You could be fine at 125, but no at 150 fo r whatever reason, and it wont necessarily show up on a WB.
A .32, .032 actually is a decent gap, I used .038 for my 150 times, and some 175s. Using TR6, good. Walbro 340m, good. Filters clean, what about the screens? What about the nozzle? Check fuel Filter also, hell replace it, its only a couple dollars.
Please post back any finding.
Charlie
1) as you said ignition, wrong plug/gap
2) clogged nitrous/line/filter
3) not enough fuel, THIS WILL cause a car to surge. When I blew my fuel line out, I was running 175 wet shot, twice if not more, without the fuel theres no fire. You could be fine at 125, but no at 150 fo r whatever reason, and it wont necessarily show up on a WB.
A .32, .032 actually is a decent gap, I used .038 for my 150 times, and some 175s. Using TR6, good. Walbro 340m, good. Filters clean, what about the screens? What about the nozzle? Check fuel Filter also, hell replace it, its only a couple dollars.
Please post back any finding.
Charlie
12-05-2003, 06:20 AM
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Fuel filter was changed about three months ago I did that after the pump swap and the tank was CLEAN!. Hmm so how would I be able to tell if it was still fuel?
Ill check the screens. They are at the sol. correct? I did mess with them since my kit it new but hey I can’t over look anything at this pint.
Race gas. Yes I was planning on that next time I hit the track just for safety and also see if it helps. My misfires were nothing odd last time I checked. a few at idle but good every where else. I do need to look into that and will next time I fire the car up. I will log my next n20 run w/a-tap.
By fuel trims do you mean l-terms? If so they are about -8 to -10 at idle and light throttle. Seems to keep the kr a little more under control that way. I don’t know what they are at WOT I never look at them. Should I?
EDIT: Oh yea heads are Local Ported ls1 heads. Cam I just switched from a 224/.581@112 cam to a raging228/234 @ 114. Surge was the same on both cams. New Valve springs were used also. No posive results. Well positive dyno #'s from the new cam just no surge help.
My all motor Dyno's are 405RWHP/385RWTQ. With the wide band at 12.2:1 and maxx tming at 26*
Ill check the screens. They are at the sol. correct? I did mess with them since my kit it new but hey I can’t over look anything at this pint.
Race gas. Yes I was planning on that next time I hit the track just for safety and also see if it helps. My misfires were nothing odd last time I checked. a few at idle but good every where else. I do need to look into that and will next time I fire the car up. I will log my next n20 run w/a-tap.
By fuel trims do you mean l-terms? If so they are about -8 to -10 at idle and light throttle. Seems to keep the kr a little more under control that way. I don’t know what they are at WOT I never look at them. Should I?
EDIT: Oh yea heads are Local Ported ls1 heads. Cam I just switched from a 224/.581@112 cam to a raging228/234 @ 114. Surge was the same on both cams. New Valve springs were used also. No posive results. Well positive dyno #'s from the new cam just no surge help.
My all motor Dyno's are 405RWHP/385RWTQ. With the wide band at 12.2:1 and maxx tming at 26*
Last edited by Tim 98z; 12-05-2003 at 06:25 AM.
