Naturally Aspirated MAP sensors + boost

[mattysshop]

how much will they see before they start poping and farting? my geuss is they would see 3-4psi or even less and then just layover

trying to run a very minimal amount of boost into a 4afe to liven it up a bit, not converting to a GE, or GZE, or anything else or trying to make the worlds fastest FE engine etc etc.. just a simple log manifold, and small turbo, a few hours of labour and i'm done..

Q - if i were to say use one from a boosted toyota, for example 4EFTE, or 4AGZE, do the voltages run the same from vac to atmosphere (as a NA map sensor), then increase voltage when they see boost?? is that how they work??

[RA35GT]

Map sensors regardless of the map range usually output a 0-5V signal. (This is a gross generalisation as in practice there is some deadband at each end for error generation).

i.e.
1 Bar Map sensor = 0V full vaccuum, 5V 1Bar
2 Bar Map sensor = 0V Full vaccuum, 5V 2Bar

etc. So basically no you can't use a boosted map sensor.

A one bar map would most likely not even register a positive pressure and if it did the ecu would likely not be tuned for it anyway.

[Shifty]

perhaps just use fuel pressure reg or microfueller

[mattysshop]

thats what i was thinking.. run initially a little more psi rail pressure, and juse use the raising rate of boost to fill in the rest.. i'll just knock 10 deg of base timing out.. might be a bit of a pig off boost!

[Shifty]

i haven't had any real experience with this but you'd be better off disabling the advance rather than knocking back your base timing

[Shifty]

oh and i'm not sure but you might need to do some electronic fiddling to stop the factory map sensor generating an error when it sees boost. don't know a lot about electronics but you will need something to stop it maxing out or your engine light might come on or ecu might go into some kind of limp mode (not sure!)

[mattysshop]

yeh probly, i'll look into that! i kinda know how i'm going to raise the rev limiter slightly (maybe by 800-1000rpm max)

[mattysshop]

maybe in limp mode it won't advance the timing.. that would be good.. haha

[Norbie]

Everything described so far in this thread is dodgy as fuck.

Microtechs are cheap. Definitely cheaper than a melted piston or a bent conrod.

[mattysshop]

yeh.. i hate microtech's... personal opinion though...

i'd rather wire up a 4agze ECU/harness.. in which case i may aswell put in a gze/gte..

it's not as dodgy as it sounds really..

and a 4afe from the wreckers would be $150-$200 on a bad day lol..

[Shifty]

norbie is just arrogant because he has a 1GZ

but that's certainyl the first time i've heard him recommend a microtech so maybe he's changing

[JustCallMeOrlando]

I think you'll find it's more a case of the usual things required to get a NA ECU work with boost are so f'ing dodgy even a Microtech IS better. The 4AGZE ECU has merit though.

[thechuckster]

using an NA ECU for boosted use is just plain retarded.

7M-GTE MX73 is 100% correct about MAP sensors.

It's not just extra fuel for boost - you have timing issues to consider and the extra fuel use is dependent on MAP not just RPM - so upping rail pressures is not a 'cheap' solution.

Get some form of 2nd-hand aftermarket ECU and do it properly.

[wilbo666]

Would you believe I have a plot of a 4afe map sensor?



Cheers
Wilbo

[benjamin]

going by that ^, it looks as if it may read slight amounts of boost. But really why bother? With the amount of time you will spend to get bugger all power increase... you could do something much more profitable.