ITA 240sx struggles a bit in 4th

[hgrewal]

i took the car to a HPDE last weekend at Sears Point (Infineon) and at couple places around the track i noticed the car was struggling a bit to go faster


(before i explain any further here is a reference link to the track map as i am going to refer to various turns on the track and where i noticed the problem)
http://www.infineonraceway.com/images/faci..._nascar_web.jpg (http://www.infineonraceway.com/images/facility_nascar_web.jpg)

this was constantly happening coming out of turn 6 and shifting into 4th after the turn and between turn 12 and turn 1 (more close to turn 1) in 4th gear. i did not notice this to be the case between turns 8 and 11 when i was in 4th but maybe that was because the paddle was not fully floored as i was going through the turns as it was normally the case around turn 6 and turn 1. also, both in turn 1 and after 6 it was occurring around 100mph and it would just struggle to go faster.

i have no idea why this was the case hence hoping some of you might have some insight or have experienced something similar yourself.

any help is greatly appreciated.

[Chris Wire]

Fuel pickup problem?

Turns 1 and 6 appear to be the highest g, long duration lefthand turns on the course. Is it possible that given the long duration of the corner, the fuel pickup is being uncovered?

On a stock tank with a factory sump, sometimes this can happen on long corners.

Also, doesn't the factory ECU have a speed limiter set at just over 100 mph?

[hgrewal]

thats what my initial thought was as well but it does not have a stock tank or fuel pump. it has a RCI fuel cell but i am not sure what pump it has as this was put in by the previous owner. also the ECU has been modified so it does not have a speed limiter.

what can be done to make sure that fuel pickup prognosis is correct?

i do not have a fuel pressure gauge either maybe installing 1 would help me narrow it down and confirm whether or not fuel pickup is the problem.

[Joe Harlan]

thats what my initial thought was as well but it does not have a stock tank or fuel pump. it has a RCI fuel cell but i am not sure what pump it has as this was put in by the previous owner. also the ECU has been modified so it does not have a speed limiter.

what can be done to make sure that fuel pickup prognosis is correct?

i do not have a fuel pressure gauge either maybe installing 1 would help me narrow it down and confirm whether or not fuel pickup is the problem.
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You have to address the pump deal first. These things will just kind of lay over if you don't feed the pump positive pickup. I would suggest that the first guess is right but the fix for it is a surge tank gravity feeding an efi pump. I had similar issues with my s14 until I did exactly this. i'll see if I can post a photo of my setup.