Discussion
It is normal for the engine to start shunting at part throttle at low rpm. It might start at around 1500 rpm, but it does vary from car to car and even from day to day. The solution is to change down a gear or two. This is also kinder to the engine (it isn't good for the engine to labour it) and giving you better throttle response if you need to speed up or slow down. Aim to keep the revs between 2000 - 4000 most of the time and your car will thank you for it.
new tornado chip fitted on fri and mapped by the aforementioned mr. adams. also had carbon trumpets, act indution pipes, all injectors removed and cleaned plus new plugs and coil. and she still does it ! so aint gonna worry no more, just have to drive faster than 30, that,s all. peter
petros said:
when driving at 30 mph the car has a tendancy to jerk forwards and back slightly. is this normal ? had a tornado chip on fri followed by a lenghty session on the rolling road but she still does it, peter
MA chip, carbon plenum, re-mapping........(squeezing out that last drop of precious power)..... so you can.........
c-h-u-g along at 30mph in 5th (1100rpm), would it be churlish to suggest some irony here? .........
That 6 letter word D-I-E-S-E-L springs to mind like a ghoulish apparition
Sorry Peter I'm just in that mood tonight, dont think i'm going to be making any friends at the moment.
petros said:
had a tornado chip on fri followed by a lenghty session on the rolling road but she still does it, peter
Gone on then Peter, spill the beans.
What numbers did you end up with?
How much does the induction kit / trumpets add?
Simon
BTW - mine shunts much less after MA's fettling. What did MA say about it?
petros said:
ended up with 225 at the flywheel, but am assured that,s more like 260 on any other rolling road. torque increase of 27lbs at the top end which is a hell of a lot.
Well mine was 190, I think Mark said that equated to 235 elsewhere. Maybe more than 260 then if it's relational. Thought I read somewhere that Mech Repairs road showed power at 80% of other roads, that would figure with mine, and make yours 280 (ish).
Those readings were after the new parts - did you get a power reading before as well as torque?
petros said:
throttle potentiometer (what,s that ? } checked peter
Throttle pot': this is essentially a variable resistor in the form of a carbon-track potentiometer which is linked directly to the throttle buterfly spindle. As the throttle opens and closes the butterfly rotates and so does the internal contact inside the pot', sweeping along the carbon track. A small current (from the ECU) passes from the end of the track and is picked up by the moving contact, the size of the current varying in proportion to the distance from the contact to the end of the track (the carbon acting as a resistor) and therefore also to the position of the throttle. The ECU measures this current which then gives the ECU the throttle position. Additionally the ECU can also determine speed of throttle movement and give mixture enrichment accordingly on rapid opening by additional injector cycles or by increasing opening time.
The pot' is in the form of a black plastic cylinder usually with 3 locating set screws (allowing rotational adjustment) and is found on the side of the throttle body on the axis of the throttle spindle.
The pot' is set by measuring the resistance at idle position and full throttle and adjusting to give the correct values. They can come out of adjustment and upset base idle mixture and blunt throttle response etc.
Unfortunately after a finite time the carbon track wears through, firstly over the range of most common throttle positions (usually quite small openings)and the previously smooth progression of resistance across the range becomes erratic and non- linear (jumping to infinity in places where the carbon has completely gone) with predicatble results.
Bear in mind tho' that this is not a primary determinant of fuelling (that being the air flow meter)and only modulates the basic fuelling so the effects of a fault can be quite subtle.
tried it with vac. pipe off and definately better when cold although shunting returns as the engine warms up but doesn,t seem as bad as before.marc adams suggests timing might now be to far advanced, willing to try anything now, this is one of those problems that,s starting to get veeery irritating. peter
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