Ok i've searched, i've been posting for awhile and know how to do my research, but ever post about this hasn't been answered...
I've got a 1991 240sx Hatchback LE...
At wide open trottle at about 5500 RPM there is definatly a notaceable power surge... I have seen this posted before and search and read everything i could find and never saw anyone come to a conclusion on why, or if its a problem, my buddies 1991 240sx SE hatchback does not do this...
Is it really a surge or maybe i'm losing power up intil 5500 RPM and then get 100%...
Nismo-freak i know you've heard about this saw your posts about the injen dyno sheet... have u heard of a solution?
-Galen
5500 Power surge? I searched!
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Cloudedone
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Exar, backpressure is exactly what it is.
The KA has a very free flowing head design. In fact, the stock exhaust manifold isn't all that restrictive to the flow at all.With an aftermarket exhaust, high flow Cat, or headers, this power surge becomes definately more noticable.
at about 5325 the KA (either one) will reach equilibrium, or a state at which the vaccuume is exactly equal between intake and exhaust. This RPM changes based on modifications like header, exhaust, and intake. But basically it is still there. If your friend does not have this to his car, that most likely means he has a model that came from the factory blueprinted. 94.5 S14's were this way, and came without the noticable boost in power based on their blueprinted design. Unfortunately, Nissan only bluprints the first 1200 motors of that kind, and then let's the computerized systems take over. The difference in these non bluprinted motors results in a diferent air flow rate, and a difference in the levels of backpressure achieved.
The KA has a very free flowing head design. In fact, the stock exhaust manifold isn't all that restrictive to the flow at all.With an aftermarket exhaust, high flow Cat, or headers, this power surge becomes definately more noticable.
at about 5325 the KA (either one) will reach equilibrium, or a state at which the vaccuume is exactly equal between intake and exhaust. This RPM changes based on modifications like header, exhaust, and intake. But basically it is still there. If your friend does not have this to his car, that most likely means he has a model that came from the factory blueprinted. 94.5 S14's were this way, and came without the noticable boost in power based on their blueprinted design. Unfortunately, Nissan only bluprints the first 1200 motors of that kind, and then let's the computerized systems take over. The difference in these non bluprinted motors results in a diferent air flow rate, and a difference in the levels of backpressure achieved.
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Cloudedone
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very interesting thanks for the reply's guys... makes much more sence then this morning... hmm... just kinda strange you hear from everyone that power starts dropping off quickly right at 5500... yet in my car its like 5500 is the strongest point, and doesn't start to slack until around 6400 or so...
In a related issue, my car in the last 2 days lost sudden power... friday night it was running fine, saturday when i started it up and drove off i first notaced it. drove 10 miles, parked for 3 hours then started the car and it was really running poorly... It sound/feels like the engine is loading up, its been idling at near 1100 rpm insted of the 750 it should be... i checked plugs, filters, car, rotor, wires, vacume lines(visually) and am still stumped... about 800 miles ago i did a COMPLETE tune to the car, i mean everything possible basicly a 60k tune up, took it to my shop (nissan dealership) and plugged it in to our computer and set idle to 754, and timing as well... my dad thinks its a bad tank of gas, but i doubt it, it honestly feels majorly slower right now, i can feel it slacking, but it almost feels like the ECU is what is making it do that... Posible ideas i was thinking is O2 sensor (but then if that was bad the car would idle higher, but it would run rich, and not lose power) bad gas maybe, (but that would make me think it would be more of a studdering problem)
doh i don't know confused for sure though, no engine light to scope at the shop either...
In a related issue, my car in the last 2 days lost sudden power... friday night it was running fine, saturday when i started it up and drove off i first notaced it. drove 10 miles, parked for 3 hours then started the car and it was really running poorly... It sound/feels like the engine is loading up, its been idling at near 1100 rpm insted of the 750 it should be... i checked plugs, filters, car, rotor, wires, vacume lines(visually) and am still stumped... about 800 miles ago i did a COMPLETE tune to the car, i mean everything possible basicly a 60k tune up, took it to my shop (nissan dealership) and plugged it in to our computer and set idle to 754, and timing as well... my dad thinks its a bad tank of gas, but i doubt it, it honestly feels majorly slower right now, i can feel it slacking, but it almost feels like the ECU is what is making it do that... Posible ideas i was thinking is O2 sensor (but then if that was bad the car would idle higher, but it would run rich, and not lose power) bad gas maybe, (but that would make me think it would be more of a studdering problem)
doh i don't know confused for sure though, no engine light to scope at the shop either...
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Cloudedone
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Luke
You sound like you are having the same problems as me. I've done every maintanence thing i can think of on my car, short of plugwires, dist rotor and cap (which is next). I did find a bad hole in a vacuum line under the EGR which i fixed and it seemed to help, but the car doesn't run too strong sometimes. I gotta keep looking at it some more though, still looking for more good ideas though.