k and N's and HS2 tuning
Posted By : Mark Stradling, 03-Dec-2005, 00:02am
Currently the car is tuned for the standard set-up - paper filters that restrict the rate air can be sucked in and a pea-shooter exhaust that restructs
how fast they can get out. In this set-up the 2 changable parts of the SU carbs, the dashpot spring and the needle are tailored to the situation. The
engine doesn't change state that fast and as you press the pedal harder the amount of air going in doesn't increase linearly (the filters can't let
twice the amount of air through at full throttle they can at half throttle).
Adding K&N filters won't make THAT much difference at small throttle openings, but the further you press the pedal the more difference they make. They do let things happen quicker though, so the standard spring starts being too 'soft' and slow to react. Generally for day to day driving this will be OK though.
When you add a tubular manifold then... well not much changes, as it's still got pea-shooter tube to go through which can only pass a certain amount of gas per second.
When you add a full tubular manifold then the gas can get out faster and you can take advantage of those K&N's. At this point you will benifit from changing the needles (at larger throttle opening the K&N's will be able to let more air through than the paper filters, so you need a needle that lets more fuel through at this ponint or you have more air than fuel = lean). Partly due to this and partly due to the full exhaust system letting everything out in less time the whole system will start reacting faster and so slightly stronger springs are required to keep the responce smooth. In this set-up the ESTIMATED choice is AAQ needles and yellow (from memory) springs, but only a rolling road session can optomise this to your specific engine.
So...You are probably fine to slap the K&N's on. You might need to tweak a little richer but you have more shiny bits which will make you feel better about spending money. You won't get the real benifit of the exhaust parts (and K&N's for that matter) till you have the full system on, so I'd leave the manifold until the rest is ready and you have the money for a rolling road session (&163;60-&194;&163;100 inc new needles/springs if required).
All this said, I AM just back from the pub so...
Adding K&N filters won't make THAT much difference at small throttle openings, but the further you press the pedal the more difference they make. They do let things happen quicker though, so the standard spring starts being too 'soft' and slow to react. Generally for day to day driving this will be OK though.
When you add a tubular manifold then... well not much changes, as it's still got pea-shooter tube to go through which can only pass a certain amount of gas per second.
When you add a full tubular manifold then the gas can get out faster and you can take advantage of those K&N's. At this point you will benifit from changing the needles (at larger throttle opening the K&N's will be able to let more air through than the paper filters, so you need a needle that lets more fuel through at this ponint or you have more air than fuel = lean). Partly due to this and partly due to the full exhaust system letting everything out in less time the whole system will start reacting faster and so slightly stronger springs are required to keep the responce smooth. In this set-up the ESTIMATED choice is AAQ needles and yellow (from memory) springs, but only a rolling road session can optomise this to your specific engine.
So...You are probably fine to slap the K&N's on. You might need to tweak a little richer but you have more shiny bits which will make you feel better about spending money. You won't get the real benifit of the exhaust parts (and K&N's for that matter) till you have the full system on, so I'd leave the manifold until the rest is ready and you have the money for a rolling road session (&163;60-&194;&163;100 inc new needles/springs if required).
All this said, I AM just back from the pub so...
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k and N's and HS2 tuning
Posted By : Mark Heaps, 03-Dec-2005, 12:35pm
I think i will save up and do the whole lot at once. How does a rolling road work? Not technically but do I splutter my way there with the filters and exhaust and they will put on the correct springs and needles or do I fit the springs and needles you suggested and then get them to fine tune it?-
k and N's and HS2 tuning
Posted By : Andy Vowell, 03-Dec-2005, 05:31pm
A good giude to rolling roads here:
http://www.pumaracing.co.uk/rrvisit1.htm
Lots of other infor on that site too so worth looking at more that that single article.
Andy -
k and N's and HS2 tuning
Posted By : Mark Stradling, 04-Dec-2005, 04:45pm
The details will vary from rolling road to rolling road, but the principle is the same.
You connect the cars driven wheels to a machine that can simulate and vary the resistance the engine/transmission has to overcome. In real life this is the friction of tyre vs road and aerodynamic drag. The faster you travel the greater the friction/drag. You also connect various wires up to get spark timing and shove an exhaust gas analyser up the rear pipe.
The classic and most common rolling road has pairs of rollers in the floor that you drop the driven wheels between and press on to the tyre - basically the same as the break testing rig in an MOT station.
The other type involves removing the driven wheels and bolting the machine directly to the hubs.
Some places will do everything for you. You arrive, drop off the keys and come back at the end of the day. Others let you help out by sitting in the car and doing what your told to with the accelerator pedal.
As for driving there, you car won't have any problem getting there on the wrong needles. You might need to richen it a couple of flats to roughly counter the extra airflow but it will run OK, just not at it's best.
Normally it takes about an hour all in and, if your like me get slightly nervous when he says "Just run up through 1st and 2nd then put your foot to the floow when you get in to 3rd. Don't worry, I'll limit the revs...".-
k and N's and HS2 tuning
Posted By : Nigel Gibbins, 04-Dec-2005, 05:26pm
hehe... that's right Mark.
Rolling roads are the best for getting every last ounce of potential from your engines. But they are not for the faint hearted - that's why some garages ask you to leave the car with them... it makes them nervous having nervous owners hanging about...
As Marks says the reading will differ from one road to the next, so don't get hung up on the actual figures just rest assured that the engine will be performing at near optimum levels after the session.
You should always use the same rolling road and operator each time if you can (if you need a re-tune) as then useful comparisons can be made. But honestly speaking that's really a racing thing as we have to get the cars re-tuned each time we change something.
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