The V8 Owners Forum -

hi guys,
im still trying to get the car to run better on map (via Kpa)
am thinking of going over to Alpha 'n' control,
what does every one else use????
and any problems while using it,

the problem i have is my idle signal is noisy and i have an idle kpa of around 60-70 kpa due to the crower cam im using.

Have you fitted a damper to the map line to reduce pulses? If not then you would expect some bouncy signals. 0.4mm mig jet and a plastic carb fuel filter should do it.

Decent ECUs offer an alpha-n to MAP blend at the low end to deal with lumpiness. Yours should as well.

cheers Bill,
got any pictures etc of this please?

What do you think I am, david blardy bailey?



http://www.johnmaherracing.co.uk/jmrshop/carbs.htm scroll down to 'inline fuel filter'

what is the reason for the filter Bill?
is it to stop the tip from moving? if so no worries in my silicone hose about it moving

mig tip is like a resistor

filter is like a capacitor

Together they make an accoustic low pass filter.

It makes the vac signal more steady, like a damper so you get a steadier reading rather than all over the place.

Bill, in doing this will it make the vac signal slower to repsond elsewhere in the rev range therefore requiring a complete remap?

If you arent using boost...why not just map it using TPS vs RPM ?

that should help with the idle situation.

ihatesissycars wrote:Bill, in doing this will it make the vac signal slower to repsond elsewhere in the rev range therefore requiring a complete remap?

No. The damping removes the high frequency components (effectively without it you are traking the accoustic waves in the inlet) so you get a better average MAP reading. Motorbikes have just the same setup on their map feeds and they rev a bit higher than you do.

Personally I am not a fan of alpha-n unless you have to use it, but some people are happy with the fact that their ECU has no idea what is actually going on and I won't stop them. At the end of the day you can get as good a tune that way with time and patience.

more and more people are using MAFs on MS now. A number of american hotwire sensors have been well calibrated and some swear by them.

Yup the itb's from the cbr 6's i had had teeny tiny vac holes in each tb and then another when all four lines came into one.

Couldn't get that to work on my v8 though It was showing nearly 100kpa at idle!

It should also have had a little film canister on the map line to damp things. Bike TBs have a lot of ports on them. Chosing the wrong one can cause problems. I would normally expect 65kpa at idle on hot cams and ITBs.

There was a reducer squeazed inside the single line where all 4 joined. T'was the correct line though, i know that as it had a Honda map sensor on the end of it!

Curious, as all the TBs in my collection have a canister as well. They may have changed things in a later design. I know that they do time sample the MAP reading in the later ECUs to get over the pulsing.