Power delivery.....

[Tobs]

I've had my chim (400 1995) for a few months now and noticed that there is a point in the rev range when the power 'kicks' in. This occurs around 3000rpm. Below this there is still power there, but if you put your foot down there is a definite increase in acceleration as the rpm passes 3200ish rpm - as if the car is turbo'd and it has just spooled up! Just wondering if this was 'normal'?

Toby.

[pwd95]

Tobs said:

I've had my chim (400 1995) for a few months now and noticed that there is a point in the rev range when the power 'kicks' in. This occurs around 3000rpm. Below this there is still power there, but if you put your foot down there is a definite increase in acceleration as the rpm passes 3200ish rpm - as if the car is turbo'd and it has just spooled up! Just wondering if this was 'normal'? Toby.

Mine does this a bit higher up 3700-800. Different car I know but it's the same engine etc. Feels like a turbo kicking in and goes like a b@****d all the way to 6000
Mine's got big valve heads and a MA Chip.

>> Edited by pwd95 on Friday 20th January 10:22

[victormeldrew]

Yes, I think thats normal. IMHO its why the 500 is easier to drive, once you get used to the torque. The 400 does have a step in the delivery, and it can catch you out mid greasy corner. The 500 delivery is huge but progressive.

[Tobs]

Thanks for your replies, good to hear it's normal! It can catch you out as i've had wheelspin in the wet when the 'kick' occurs - tends to keep you alert!

Toby.

[jsr]

My 400 feels powerful pretty much throughout the rev range. No real kick, but can definitely feel the car accelerate harder once the torque builds up.

This may be interest - dyno of my car...

[Tobs]

Hmmmm looks very smooth - no jump at the 3200rpm I seem to feel with my car. Is this the point at which the lambda's switch out and the engine runs open loop as opposed to closed loop below 3200rpm? Would a worn cam give this effect (car has done 68k).

Toby.

[jsr]

3000rpm ish is when the lambda sensors do their stuff, so could explain the jump.

Mine always feels smoother and happier above 3000rpm.

[plfrench]

I think most engines have a sweet spot where they 'come on cam' and you feel a surge in power. It is quite noticable in my Focus at about 4k rpm, so I'm sure you'd really feel it in a car with twice as much power...

Paul.

[v8 racing]

To be honest you shouldnt really feel a noticible jump, when i have had this on customers cars the most common problem has been the bob weights sticking in the dizzy, so you end up with around 10 degrees of advance up to 3000 rpm and then all of a sudden you get 28 deg, might be worth just checking!, pop the dizzy cap off and just try and turn the rotor arm, should be nice and free with a little resistance if its jerky that will be the problem!

[prbw]

The symptoms in this thread sound identical to those discussed in 'Hesitating' back in mid-Dec. If a marked power surge at about 3100rpm is so common on the 4 litre, I'm surprised that it does not seem to have shown up on somebody's rolling-road session, and also that a solution does not appear to be immediately available from the experts on this forum. I will certainly check the bob-weights on mine, but I have to say it seems unlikely that the weights on several cars would all free up at exactly the same point in the rev range. Still, worth a try, since every thing else seems to check out OK.

[david beer]

I would say its fuelling, i know it is with mine and many others. Swap the tune resistor for a 380ohm and it will not use the lambdas, just to check of course !! Then get Mark Adams to set up a new chip.

[v8 racing]

I am not saying it definetly dizzy related i was just offering another option that could cause these symptons, a standard will give full advance between 2500/3000 rpm and they can start sticking after a few years, the easiest way to check is just put a timing light on it and make sure your getting a nice smooth ign curve, if it goes so far then suddenly jumps theres a problem, as for so called experts not finding this problem sorry i havent driven a tiv with this problem? if there is somebody with a car with this problem and would like to come and see me if i cant fix it there wont be charge, but i am sure there is a cure whatever the cause is!!

[Tobs]

I checked the dizzy this weekend, by taking the cap off and turning the rotor arm. There seems to be some 'slack' movement before the spring of the advance weights. The 'spring' seems to be smooth so I don’t think the weights are sticking, however there does seem to be an appreciable amount of 'slack' (i.e. the rotor has about 1-2 degrees of free play). Is this normal or is this wear on the dizzy drive? If it is wear does this matter as the dizzy is only driven in one direction - so the 'slack' will always be taken up.

I also reset the timing - advanced it slightly from about an indicated 7 degrees to about 9 degrees. Engine seems to run a little better now - more power at the lower revs. Also no pinking evident- so I may advance it a bit more this weekend! Is there a set figure for the timing or is it generally best to advance the timing until you get some pinking under heavy load and then back it off a bit?

Toby.

[v8 racing]

Hi Tobs there is always a slight bit of slack so nothing to worry about there, i would disconnect the vacum pipe and leave it disconnected, then set the timing to 28 deg at 4000 rpm, dont worry what it is at idle, its more important to get the high rpm set correct

[Tobs]

Cheers, I'll give it a go this weekend...