MSefi.com read only forum (Jan.15,2018)

I'm starting a new megasquirt project, and I'm slowly collecting the pieces.

The vehicle is a 1981 pontiac firebird, 301 (4.9L) turbo charged V8 - all stock. This is an old school draw through design.

I've acquired a throttle body setup off of a 1995 chevy 5.7L pickup. This may eventually become a bottleneck, but it'll give me a place to start. This is replacing an 850 CFM quadrajet carb.

I'm ordering a fuel pump block off plate from summit racing, and I noticed they had this generic inline fuel pump:
http://www.summitracing.com/parts/SUM-G3138/

That seems like it will supply all the fuel I need and more, has any one had experiences with this fuel pump? Seems like a good price, with mounting gear as it is on sale for $74.

Thanks,
SLL

Well, I still haven't picked out a pump but I did just order up the MSII installer kit... $700 disappeared pretty quick. I still have to acquire the wide band O2 sensor and a fuel pump.

Lambo wrote:I'm starting a new megasquirt project, and I'm slowly collecting the pieces.

The vehicle is a 1981 PontiacFfirebird, 301 (4.9L) turbo charged V8 - all stock. This is an old school draw through design.

I've acquired a throttle body setup off of a 1995 chevy 5.7L pickup. This may eventually become a bottleneck, but it'll give me a place to start. This is replacing an 850 CFM quadrajet carb.

I'm ordering a fuel pump block off plate from summit racing, and I noticed they had this generic inline fuel pump:
http://www.summitracing.com/parts/SUM-G3138/

That seems like it will supply all the fuel I need and more, has any one had experiences with this fuel pump? Seems like a good price, with mounting gear as it is on sale for $74.

Thanks,
SLL

Yes, I am installing Mega Squirt on a 79 TA.
I will be using a LS1 in-tank fuel pump module like this.
http://www.vetteworksonline.com/ls1_conversion_fuel.htm

Also check out LS1tech.com, Fueling and injection forums
http://www.ls1tech.com/forums/fueling-injection-8/

Thanks for the info... that's a good write up on the tank conversion.

The conversion for the sump style pump is probably the better way to go, but I think I already have a return line plumbed for this vehicle (an odd feature on a carbureted vehicle, but I do believe it has one). So, the path of least resistance for me is to just put on an inline pump. I'll start there at least, I may want to do the tank conversion later, but I've got plenty of other stuff to figure out before that.

Yes, There are two fuel lines, a 3/8 inch feed line and a 5/16 inch return line, on the drivers side and a 3/8 in line on the pass side for the vapor canister.

but I think I already have a return line plumbed for this vehicle (an odd feature on a carbureted vehicle, but I do believe it has one)

Not at all.........

Many carb'ed cars have return lines, dating back a lot of years. They came along with un-vented fuel systems, vapor canisters etc.

FWIW....

I use an inline 255 lph pump w/ 3/8 feed & return lines. 3/8 return is probably overkill but I had it handy so I used it. Your 5/16 return is probably just fine. I have used the same pump for a tpi setup and now it is supplying 4 85# injectors on a tb with no shortage of fuel. My 2 cents worth is.... Go with whatcha got!

Good luck,

Ken

I use an inline 255 lph pump w/ 3/8 feed & return lines. 3/8 return is probably overkill but I had it handy so I used it. Your 5/16 return is probably just fine. I have used the same pump for a tpi setup and now it is supplying 4 85# injectors on a tb with no shortage of fuel. My 2 cents worth is.... Go with whatcha got!

Ah, good to hear... I have kind of settled on getting that walbro pump rather than the cheaper summit one. I guess they're kind of loud and the walbro seems well liked and well seasoned. I'd like to upgrade to that Holley 4 port TB, but I'll worry about that after I start running out of fuel and air.

Thanks!

So I'm getting around to pumping fuel delivery... I've read a few things that lead me to believe that the fuel return line is only 1/4", and the vapor line is 5/16". Will the 1/4" return line be enough?

I would not use a 1/4" return line under any circumstances!

Been there, done that...........

If you are pushing 255 lph you will have problems with regulating fuel pressure with that small return line.

If you want to try it, measure the fuel pressure where it exits the tb to return to the tank. If the pressure is more than 3-4 pounds I would get rid of the 1/4" line in favor of at least 5/16".

Ken

EDIT: Grab a set of calipers and make sure of the size.........

I just grabbed my calculator and figured out that your 43 gph pump equates to about 163 lph. (a lot less than my 255 Walbro)

Regardless, I would opt for the 5/16" return.

BTW.... Have you bought the pump yet? 85 psi seems to be a bit 'over kill' since your tbi will only need about 15-20 psi on average.

Ken

At 20 psi, that pump turns into a ~33 gal/hr pump. With a RRPR and 10 psi boost that fuel pump turns into a ~28 gal/hr (106 l/hr) or 168 lb/hr. A turbo engine has BSFC of about 0.6 lb/(hp·hr). So 168 / 0.6 gives you theoretical maximum 280 hp with that pump.

This pump is not a good choice for a turbo engine. Better off getting a Walbro inline pump for $30 more.

kjones6039 wrote:I just grabbed my calculator and figured out that your 43 gph pump equates to about 163 lph. (a lot less than my 255 Walbro)

Regardless, I would opt for the 5/16" return.

BTW.... Have you bought the pump yet? 85 psi seems to be a bit 'over kill' since your tbi will only need about 15-20 psi on average.

Ken

a73camaro wrote:At 20 psi, that pump turns into a ~33 gal/hr pump. With a RRPR and 10 psi boost that fuel pump turns into a ~28 gal/hr (106 l/hr) or 168 lb/hr. A turbo engine has BSFC of about 0.6 lb/(hp·hr). So 168 / 0.6 gives you theoretical maximum 280 hp with that pump.

This pump is not a good choice for a turbo engine. Better off getting a Walbro inline pump for $30 more.

Yeah, I did end up getting the walbro from DIYAutoTune. There seemed to be less question marks with it. I liked that it came with barb fittings as well. It probably is over kill for this setup for now... we'll see. At most I'll probably be running 20psi with the regulator. I've decided to upgrage the GM 454 TBI, or a holley 670cfm. I thought I might just order up the holley pre-filter and can filter that is used on the holley projection system. They're cheap enough and I can plumb them all together back by the tank using hose clamps.

So, it seems 5/16 return is what I need... that happens to be what the vapor line is; ahem... that is a "no-no", is it not? I've got to drop the tank anyway, so I'll pull the pickup and see how it is plumbed in. I don't plan on utilizing the charcoal canister, so, what to do with the vapor line?

Lambo wrote: So, it seems 5/16 return is what I need... that happens to be what the vapor line is; ahem... that is a "no-no", is it not? I've got to drop the tank anyway, so I'll pull the pickup and see how it is plumbed in. I don't plan on utilizing the charcoal canister, so, what to do with the vapor line?

It depends on the car - sometimes the vapor return line works perfectly well. Other times it's nearly plugged from years of gunk, or has a restrictor orifice in it. One or the other was the case on our Nova.

This graphic should really drive the point home. Below is the pump curves for a Walbro pump. The red line is the Summit fuel pump. Very weak sauce.

Nice, well, I'm glad I got the walbro then...

I'll be dropping the tank sometime this weekend and I'll find out if the vapor line will work as a return. I'll probably still USE the vapor hardline for the return. If the vapor port itself doesn't work, I may drill out the current 1/4" return in the sending unit flange and put in a fitting for more flow, then plumb the current vapor line to it, block off the vapor port on the tank and use a venting gas cap.

I'm not sure of your setup but it seems to me that you could then use the existing 1/4" return for the vent. Just thinking out loud here...........

Ken

kjones6039 wrote:I'm not sure of your setup but it seems to me that you could then use the existing 1/4" return for the vent. Just thinking out loud here...........

Ken

I hear that... I could us the 5/16 line for the fuel return, and us the 1/4 for the vent - I'm just not sure what I'd vent it to. I really don't know how the charcoal canister works, and how every things is plumbed for it, nor how the purge is setup. I'd consider hooking all that up if there was a generic way to do it. If I can keep fuel fumes/smell down that sounds like a good thing to me.