I would think you could drop the FP solenoid control without much issue, since you've got pretty much complete control of the mixture without it. The VDI and Aux ports are important for streetability. For racing, since we rarely drop below 5000 RPM we just keep them wide open all the time.

 

yeah, but since I'm making a plug 'n play setup, and I don't want my users to have to do much other than hook it up and run a vacuum line to it, I want to control the solonoids...

I could just require the user to move the vacuum line directly to vacuum instead of controlling the solonoid... but I think that'd be asking too much. Also, allowing vacuum to get to the regulator makes tuning low load and other low pulse-width situations easier.

I have several people who want to remain streetable... for example, tofuball's megasquirt has full control of electric fans, VDI, and aux ports with the extra output circuits on the msns-extra daughtercard... he gets pretty good mileage and low-end torque (he can start off from a stop in 4th gear without too much trouble), and he gets a lot more power than stock.

Anyway, it may not be necessary for individual installs to do this since each individual user knows what he/she wants to do, but I don't know what my users are going to do, so I have to plan for everything.

 

Yea if that's the FPR solenoid you really don't need it. I think it's only used on a hot start, and during cranking you really don't have much vacuum--so it doesn't do much at all.

On the turbo cars, it would be good to control the fuel pump relay resisitor, for this you will need an output channel.

 

well, when the fpr solenoid is on, there is vacuum going to the FPR... so it has to be on almost all the time. It is turned off sometimes on cranking...

So anyway, I need to turn it on while the car is running so vacuum gets to the FPR. Otherwise you'll be getting full fuel pressure all the time, and I don't think that'd be good. So it's exactly BECAUSE the FPR gets vacuum while the engine is running that makes me need to control that solenoid... even if it's just to turn it on all the time.

 

I'm building my setup for a T2 engine, which i remember reading no one was certain about the vacuum line on those engines. Also, i don't have the 5th/6th ports or the VDI to worry about.

 

I would run the FPR pressure sensing line straight to the manifold and NOT thru the solenoid. This way you are assured the FPR is sensing the boost pressure and adjusting the fuel pressure accordingly.

IIRC the FPR line is under the UIM so it can be hard to get to unless you have the UIM off. I think if you leave the vacuum lines as they are it will still work if you don't energize the solenoid (i.e. leave the solenoid disconnected). Pretty sure when the solenoid is activated, it vents the FPR sensing line so the FPR sees atmospheric pressure and results in a higher fuel pressure during startup (since it is not seeing vacuum idle pressure).

That's on a S4 T2, the S5 may be different.

HTH,

Scott

 

At the moment i don't even have the T2 engine (saving up to order it soon), so we'll see. I'm doing a lot of firsts for myself. First build of a megasquirt, first T2 engine in a vert...should be fun.

 

What I'm saying is that with that solenoid on, unless it is broken, you ARE sure that the FPR is sensing the manifold vacuum/boost. I've tested my setup to make sure it turns off and on when I tell it to, so I know it's working, and I pretty much have it set up to always be on when the engine is running.

My point is that I have to support that even if other people don't because otherwise I'm not really "plug 'n play"

I'd definitely recommend taking that solenoid out of the loop and just running manifold pressure straight to the FPR, but I can't expect that everyone will want to do that. I have to plan for as much as possible.