Map sensor reference
 

Ok not sure if this should be here, in the microtech section or in the FC section.

S4/s5 intake manifold, old MTX8 ecu, Laggy map signal.
Tried various locations two tuners have told me to to put it in different locations, the latter where i had it the first time.

Symptoms; hesitation on slight tip in and full lean on the AFR guage.This happens at small throttle openings - basically the change from idle vacuum to part throttle vacuum.

I suspect its the MAP sensor inside the ecu.

Im on the verge of tapping a new ref point and running 1/4" EFI hose to the MAP.

The question is; should i be taking from the primary or secondary chamber/runners on the IM for best response?
Should it be near the throttle body?
I notice that the the primary and secondary butterflys all open in unison but the primary and secondary chambers and runners are completely seperate from each other.
Would it hurt to bridge them and run from both?

Do not increase the size of the hose going to the MAP sensor. If anything it needs to be a small ID and a short run to reduce the volume that needs to be pressurized. Ideally the MAP should be read from a place that is the most representative of what the chamber will see, typically on the manifold near a port (or equivalent) and averaged across two (Y-connection) or in a place that has such a feature.

All of that being said, IF the signal is simply laggy (with no underlying hardware issue behind it) then place the MAP hose in a place that see pressure before it reaches the end of the LIM. Although, this can potentially cause an oddity where the MAP sensor will see the wrong pressure if there are pressure wave oscillations.

Do not place the line near or at any venturi, valves, or other items that cause vorticity or flow acceleration. Ideally you want the reading to be in as close to a stagnant section of air as possible.

There is the possibility of a hardware issue even down to the possibility of the hose being cracked enough such that enough air is leaked that it only appears there is MAP lag. It could also be something such as your throttle enrichment setting being off (assuming the ecu has/uses such a thing).

While this is not a complete answer I hope it gives you some food for thought and fruitful avenues of exploration.

Thanks that makes sense regarding the hose size, I'll stick to 3mm then.
Might put an extra port on the plenum area and see what happens..

If everyone else isn't having those issues with similar setup i'd say it is nore likely no change in tps signal at small angles or incorrect throttle enrichment which is likely the problem if it is only on transient. If it is sustained I'd suggest a leak in the line or fittings.

Thanks. Will double check.

sure sounds like tip in fuel tuning to me.

^ Yeah. Thats what i think too. And what i was thinking the whole tim e i was pulling the strut bar and intake manifold off and looking for a better way to hook up the vacuum line. And what I was thinking when i put it all back exactly the way it was, lol.
I did play with the TPS adjustment on the TB which helped a bit.
Its either the tune or the flintstones MTX8 ecu. Looking at the handset, tps sensor and map sensor seem responsive enough, so will have to get the car back there and get him to clean the tune up a bit.

Just a thought - could it be the result of cold-ish plugs, big-ish injectors and a low resolution ECU?

Those things don't help but again others no doubt have similar working well enough. Make sure they check tps signal across its range and earthing etc is good as well as throttle enrichment stuff.