16 replies to this topic

[I could eat a horse Haha]

Looking to fit a Megalojt system to a 1380 - not sure which throttle sensor to use?
Ideally I would like to use the MAP sensor as it is much easier to fit.

Problem is:-
The engine has a Kent 286 cam in it.

Megajolt suggests that for extreme cams that a MAP (Manifold Air Pressure sensor) is not the best option as the cam can cause a a pulsing effect in the manifold.
Question is does anyone know if this cam will cause problems? - Or do I have to fit the throttle position sensor to the carb??


Cheers in advance

[Ouster]

286 isn't 'extreme' - MAP should be fine. If you find you are getting a 'pulsing' reading then plumb in a small chamber (like a fuel filter with the innards removed) going from the manifold to the input on the MJ unit.

[Pooky]

I have a Morspeed PH3 cam which I have been told is a rather lary cam but is fine on MAP.

I'd go for MAP if I were you, I think you'd have to have a rather extreme motor to actually need to use TPS.

[1293sleeper]

cool i was going to ask this to saved me the hassle

[HARBER07]

I think the MAP sensor would be fine on a 286 to be honest as its not a crazy profile. Do as Ouster said with the chamber as it stabilizes the reading. You could also leave a couple meters extra of vacuum hose before it get to the Megajolt if your not worried about neatness (which is what I've done and hidden it under the carpets)

[mini-geek]

wouldn't fit a TPS with an SU anyway the float will cause inacuracys in the readings.

[HARBER07]

How?

[mini-geek]

because the float will not always be at the same position as the butterfly.

[HARBER07]

Not sure if we're both on the same wavelength . The throttle position sensor is attached to the throttle shaft on the carb is it not? (well no its not always - can be at pedal end?)

[mini-geek]

it's hard to explain but I'll try my best. and it's slightly more difficult that I don't fully understand it myself.

lets take the TPS out of the equation firstly, as you 'floor' the throttle the butterfly opens as fast as you put your foot down, but the float, because it's dampend it will slowly open as the engines need for air increases along with the RPM for now I'll call the the 'float catchup time' (I just made the name up)

so while using the TPS the TPS will read FULL THROTTLE even though the float (because of the catch up time) is still not fully open IE not having full throttle.

Dose that help?

[HARBER07]

Good point, and well explained! But surely its not going to be a massive problem for the few seconds it needs to fully open? (for the example anyways) As i think the float (is that the correct name as i got WAYY confused with the fuel float ) open up with increase in air flow?

[mini93]

i use MAP on my rally car with a 286...works alright

[I could eat a horse Haha]

Thanks chaps.

Decision made - Will go for a MAP sensor I think - They always do a kit for TPS conversion if it is giving problems.

[mini-geek]

sorry yes I mean the piston (I often get them wrong) but as you say how much of a problem it will cause I don't know I guess the only way to find out is to do a back to back test.

[HARBER07]

PISTON thats it

Nice info though cheers