Blowtus

Ok. Well I've got a reasonable quote for insurance on my rx7, but apparently I have to make engine mods before they'll accept it :p
Has helped convince me to get the boost up a little... Currently it appears the limiting factors to this are a factory ecu which cuts fuel once a specified voltage is reached in the pressure sensor, and then a lack of fuel once the ecu is tricked into not cutting fuel above certain boost.

I'm informed that it's a reasonably simple process to clamp the voltage of the pressure sensor at a specific level. My present thoughts with regard to getting more fuel in once the voltage is clamped, is to modify either the water temp or afm output in proportion to the amount pressure sensor voltage rises past the cutoff. Hopefully via some sort of twisty **** for ease of tuning. Now it's nice and easy to say like that, but I'm interested in some opinions and thoughts from anyone who hopefully knows a little more than me... interested in both the feasibility of the electronics, and the general idea of it. It's similar to what an safc would do, but anything under fuel cut would function normally, it'd be much simpler to tune (at the expense of af ratios possibly not staying as steady I guess) and would cost a whole lot less

thoughts?

BDC

That's the problem -- you can't just manipulate 'sensor signals for more fuel'. It's more precise than that unfortunately. You'd be better off shooting in a pitch black room, trying to hit a moving target, then you would being able to 'tune' the engine right.

Your best bet, if you're wanting to remain budget, is to dice the FCD and find an ECU chip that eliminates fuel cut.

B

Cheers!

i agree with BDC, but back in the day people have tried fooling that ECU such that the engine was always cold, so the ecu willdump more fuel to try to warm the engien up.

THis will richen you entire RPM band. This mod however is not suggested.

If you want to go fast you have to pay

Blowtus

all thoughts appreciated... but if the engine only gets told that it's cold *when it needs more fuel* then it'll hardly richen it up all the time...
I'm not talking about running 16 psi, larger injectors and a new turbo off it... just adding enough extra fuel for maybe 4 psi...
would an ecu chip that eliminates fuel cut have revised fuel mapping, or was that simply a 'forget about extra fuel' suggestion?

Cheers!

upon initial start up of the car in the morning, the engine is cold. Sensors tell teh ECU that the engine needs to warm up, therefore the ECU will dump more fuel during this warm up time.

You can trick the ECU into thinking the engine is always cold, regardless if you just started the car 1 min after parking overnight or finished a 2 hour drive on the highway.

When you engine is cold the Ecu dumps fuel in to warm it up quicker.

look up paul stokes, he figured out how to do this back in teh day.

btw.

7 psi + 4psi extra is a lot of psi on stock fuel system that is 14+ years old

Blowtus

sorry, you're misinterpreting
I wouldn't want to tell the engine it's always cold, only when it's under boost levels that the ecu can't deal with.
That way driveability and fuel consumption aren't reduced in normal driving...

I thought plenty of people were managing 10psi with just an safc... only 2psi past fuel cut innit? if it turns out the fuel system can't cope I'll wind the boost back until it can...

I'll see if I can find what Paul's done on the subject...