in tank fuel regulator - "no return"

[noam]

hi
first time asking, long time reading http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

if i am using the original fuel pump from the bike, which has the fuel regulator built in it. how does this affect my fueling or PW as the gradient of pressure (fuel line-manifold) changes all the time and thus changing fuel flow?

p.s
i used the find option. havent found an answer

i am using a MOTEC M4 ECU

[Kirk Feldkamp]

Long story short, you will probably be just fine. The shape of your fuel map will look different from a manifold referenced FPR... but that doesn't really matter. No matter what you do, make absolutely sure you're using a MAP sensor (referenced from the plenum of your manifold) to compensate for changes to manifold pressure. If you're going to do speed-density, that's already sorta baked in. If you're running alpha-N (TP vs. RPM), then you'll do that as a MAP compensation table (simple). Other than that, make sure your get your IJPU on the M4 small enough so that your largest numbers on the fuel table are somewhere between 90 or 100. This will really help your fueling resolution at lower PW's where large stock injectors might have some inconsistency. As long as your idle PW's are at least about 2ms, then you should be just fine.

-Kirk

[noam]

Originally posted by Kirk Feldkamp:
Long story short, you will probably be just fine. The shape of your fuel map will look different from a manifold referenced FPR... but that doesn't really matter. No matter what you do, make absolutely sure you're using a MAP sensor (referenced from the plenum of your manifold) to compensate for changes to manifold pressure. If you're going to do speed-density, that's already sorta baked in. If you're running alpha-N (TP vs. RPM), then you'll do that as a MAP compensation table (simple). Other than that, make sure your get your IJPU on the M4 small enough so that your largest numbers on the fuel table are somewhere between 90 or 100. This will really help your fueling resolution at lower PW's where large stock injectors might have some inconsistency. As long as your idle PW's are at least about 2ms, then you should be just fine.

-Kirk

Ok. thanks
Just for clarification, my MAP sensor is reading its pressure from between the intake valve and the injector - very close to the injection point.
On the subject of the M4:
The manual states that it is recommended for NA engine to use TPS mapping, furthermore, if using TPS mapping the MAP sensor should be open to barometric pressure.
On the other hand, if using a MAP base mapping, the fuel regulator must be referenced to the manifold.
I am a bit confused, are these all just recommendation? What you wrote here makes a lot of sense to me but it doesn’t quite seats with what is written in the manual of the M4.

I appreciate any info you can add on the subject. This is my first time tuning and I am a one man team.
Again thanks
Noam

[Kirk Feldkamp]

I would avoid using a sensor port location that's on a runner. The transients that happen in the runners during a drawdown event will mess with your compensation. If you look at a stock motorcycle TB, they daisy chain the four ports together into one line (averaging them), and feed the MAP sensor that way. It's sort of a matter of opinion on a FSAE engine how to do it, but I've never had any issues with placing it somewhere on the plenum. The idea is you just want to pick a spot that's less likely to get any direct pulsations from the runners. The base is fine, and the end of the log usually works too.

Motec means well, but their recommendation probably assumes a "racing" airbox with ITB's that are breathing essentially barometric pressure. In that case, their recommendation makes total sense. In the case of FSAE, you've got a single throttle body feeding a common reservoir, and a restrictor that will mess with your manifold pressure at higher power levels. I've always just used a MAP on the manifold (no separate baro sensor), and never had any noticeable issues. I'm pretty sure any barometric changes will get baked into your MAP comp if it's in the manifold anyhow (think of where the engine is drawing from).

-Kirk

[noam]

Actually we are mimicking the original set up you mentioned by connecting the MAP to 1 hose which is connected to 4 runners. If I will encounter problems I will move it to the plenum as you said.
On the subject of choosing a load of reference for mapping, I understand that MOTEC's "recommendations" are to be treated as recommendations only.
Thank you for your insight. I will properly have some more questions ahead. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

Noam

[Mumpitz]

Be aware of the increased chance of vapor lock, recirculating regulation will pull heat from your rail, unless your gas tank is hotter than your rail http://fsae.com/groupee_common/emoticons/icon_redface.gif