Throttle lag from idle, duratec

[Austin David]

I've got a bit under 3k miles on this 360 duratec.  Stock plenum and airbox, paper filter, 360 cams.

 

Some video of the behavior: Cold / Hot

 

Basically there's a noticable throttle lag, a little worse when cold.  It doesn't really appear when I roll on, and it's fine at WOT, though I haven't put it on a dyno.  But it's fast as sh*rt so I don't think anything significant is wrong.

 

I tried resetting the ECU to reset TPS.  I also tried rotating the TPS a little forward and back, that didn't help the stab and it made idle worse.  

 

I've also put a K&N cone on the TB, same sucking behavior / throttle lab.  I mathed it out, the cone had the same surface area as the paper so I kept the stock airbox in place while I work on the WAF for RBTB.

 

Any ideas what's going on?  And most importantly, is there an easy adjustment that doesn't involve flashing the ECU?

 

 

[KnifeySpoony]

https://www.caterhamlotus7.club/forum/techtalk/throttle-response-duratec-0

[Austin David]

Yeah, I saw that post -- it's what got me poking at the TPS. I have no other negative issues than the lag when poked.  Otherwise it pulls smooth and strong and is a delight at street RPMs when my wife is watching.  That is, it's very smooth and well-behaved when needed. 

 

I can try backing the idle down a bit to build more vac, see if that changes anything.

[Dave W]

Could be low fuel pressure. Check the pressure with and W/O the vac connected. Possible pump, filter or pressure regulator. 

[Croc]

@Austin David By the way, have you seen John Vine's message to you on Blatchat this morning?

[MV8]

I'd look for vacuum leaks everywhere on the intake side including anything connected through a hose. I don't know what you can see with software, but also check the TPS volts at idle, fuel pressure, and temp indication for out of cal sensors or wiring/connection problems but it seems like delayed or poor MAP response.

If the MAP is located off the engine and connected by a soft hose, to decrease the delay in response to manifold pressure, I'd fit aluminum tubing that is the same OD as the end fittings with just an inch or so of hose at the ends to slip on for sealing. You can get the tubing from Aircraft Spruce. I'd mount the MAP as close as possible for minimal tubing length.

[Austin David]

17 minutes ago, Croc said:

@Austin David By the way, have you seen John Vine's message to you on Blatchat this morning?

thanks for the heads up.  If only there were some sort of international network of these forums, so members of one could have privileges in all

 

 

[Croc]

@Austin DavidThere is such a network.  But it does not seamlessly connect the way we would all want/need and it excludes the UK which makes it a lot less relevant.   

[Alex-Ks1]

does your car have a MAP sensor, it can be LAZY, I have seen this many times, there made very cheap, You can check it with an ohm meter or just by unplugging it, if the motor misses, shakes, then its good. A scanner will tell the story

[MV8]

You can also ruin it with an ohm meter.

[Austin David]

I'm gonna try it disconnected, but I don't expect to learn much.  It runs great in all cases except this "stab from idle," where it's noticably worse cold, but still always present.