hesitation on cruising

dark_knight

dark_knight

Member +
mods, this is a little bit of a mix between several categories of what could be wrong so please feel free to relocate it appropriately if necessary.

so here's the scenario: cruising down open road (a pretty long stretch) and was granny shifting all the way to 5th.. then i let boost kick in and carry me all the way to about 110mph - was at about 5,000 revs then. but. when i held the throttle steady to maintain that speed, i could feel some hiccups of hesitation as if the turbo/engine was cutting out. and no, it wasn't the speed cut engaging - it's disabled. i also wasn't at WOT but was past the half-way mark on the throttle.

car spec is:
- ct9b turbo on stock manifold (cat still in place)
- stock wastegate & stock actuator (set to 0.85bar)
- blitz LM filter
- kakimoto straight-through exhaust

any ideas what could be causing the hesitation..? i'm thinking it's at that spur of the moment when my wastegate is tying to expel the exhaust but not doing such a brilliant job at it and the hesitation results from the boost spiking..? and it's also not seat-jolting hesitation, just a slight pause in the engine hum.. like a brief power loss..
just an idea..not sure..
 
Jay

Jay

Admin
Generally the stock setup does tend to run out of puff around the 100 mark. If it's a very noticeable drop in power you may find you are hitting the standard 112mph speed restriction that all JDM imports have.

Jay
 
dac69er

dac69er

Super Moderator
could be a misfire. would just do the normal checks of the ignition first then see if its fuelling related. have you changed your fuel filter?
 
dark_knight

dark_knight

Member +
ignition? fueling?

@dac69er: a misfire..? car idles sweet and revs flawlessly all the way up the rev range - in neutral off-boost, but when on boost for extended periods, then that's where the issue is.
yes. fuel filter is new.
 
dac69er

dac69er

Super Moderator
you can get misfires when not under load. it can be something igntion related breaking down over time, rather than under load.

i would think it is more fuel related though.
 
dark_knight

dark_knight

Member +
bad fueling?

@starletgtturbo1: have RON97 fuel here..

@dac69er: so you are saying perhaps the fueling is not right..? :(
 
dac69er

dac69er

Super Moderator
i would doubt that. either a blockage/restriction somewhere or a faulty fuel pump, or possibly fuel filter on pump blocked etc etc
 
dac69er

dac69er

Super Moderator
you would only notice on boost as lower octane fuel would mean the timing would be retarded. probably wouldnt see a noticeable difference. would make no difference when cruising
 
starletgtturbo1

starletgtturbo1

Member +
jesus cruising at 110mph lol, at 5000rpm he will be at full boost. when i ran 95ron in my starlet as soon as i high full boost it would stutter and feel sluggish, so i just ran it wit low boost till the tank emptied
 
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dark_knight

dark_knight

Member +
fuel(ing)-related

so you all think it's fuel-related..?
i'm pretty sure it's not the filter coz i recently swapped that for an oem one.

i mean, i don't mind the stutters - they are not all that bad to say the truth, was just curious to know what was causing them..
in as much as we have RON97 fuel, i may not be certain that's what we are getting at all/most of our gas stations.. some have been known to sell 'flavored' gas.. :p
 
gibby1980

gibby1980

Member +
What is your boost gauge reading? 12-13 psi?

When I run mine in 5th gear and the boost goes and holds at anything higher than 12psi the hesitation presents itself. Hope that helps!
 
dark_knight

dark_knight

Member +
stock engine limits

@gibby1980: i run at 0.85bar so that's about 12PSI on the ct9b turbo. i'm guessing this is somewhat stock behavior when pushing the engine to its limits and not necessarily something wrong..?
 
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