walbro255 lp or hp?

[pitbull419]

Whats the difference between the two.
PLease dont just tell me the difference is high pressure/low pressure i figured this out.
Are there certain mods to my car i have to look at to decide which one i should get?
Also what kind power are these reliable for?
Thanks

 

[chicagoavenger]

They flow the same at idle and well the hp has more pressure up top then the regualr 255 if I remember correctly. Don't forget that afpr when you get a 255 so you won't have issues with over running your stock one.

 

[pitbull419]

So does the pressure differ anything past idle with the hp?Or does it only have higher pressure at wot or close to wot?
It wont make my dd idle or run weird?
Thanks for your response

 

[CanadianTSi]

Well considering you should have an AFPR with either 255, get the HP and call it a day.

 

[pitbull419]

Yes i have afpr.Thats what i was thinking to just get the hp.
I just wanted to see if there were any other differences.
Thanks for the replies.

 

[Mikelb]

http://www.dsmtuners.com/forums/showthread.php?t=245608&highlight=255+lp+hp

 

[zippyshoe]

I agree with CanadianTSi - I would go with the 255HP. The HP (high pressure) version has similar fuel flow capabilities as the regular 255 at idle and low-boost conditions. However, under high-boost conditions, the HP version provides higher fuel flow capability than the regular 255 - these are just the conditions where fuel capacity is most critical. Also, I don't recall a significant price difference between the two.

 

[pitbull419]

There tha same price
I was just wondering if there was anydifference because they were tha same price and both 255

 

[Project2G]

The HP allows for higher pressure applications. My friend has the HP one so
that when he wants to crank up the pressure for bigger injectors and the
fuel rail he wont need to add a second fuel pump to get the pressure up
enough.
If you get a 255 pump Hp or Lp, you NEED a fuel pressure regulator,
which then you need different lines Aeromotive I believe sells a kit.

 

[Mikelb]

Ok, I kinda indirectly linked to this yesterday, but let me explain.

To determine which pump is best for you, you should look at your goals. You have to look at your turbo size, injectors, and how much air your engine can move.

The turbo will be rated for a certain efficiency, check the compressor maps. The manufacturer should have published specs on the turbo, telling you how many lbs of air it is capable of pushing.

You should also take into consideration what size injectors you plan on running (as big as you can, as long as you can control them). with an SAFC I wouldn't suggest anything bigger than 650's (I think some people advocate using 680's). If you're running DSMLink, whatever injectors you can afford, 850+...

Look at how much air your engine will be capable of flowing. This will be affected by things like: porting, exhaust manifold, exhaust size, head work, etc.

Now here's a thread that lays out different fuel pumps and injectors and how much air they can support:
http://www.dsmtuners.com/forums/showthread.php?t=244522

 

[daren_p]

Personally I don't know why you would bother with the 255lp for a turbo car, probably fine for a NA. Like was said they flow basically the same at lower pressure (HP always seems to be abit more) but when you get to about 60 psi the LP starts to drop off in flow compared to the HP. Being our FP raises with boost we usually see 60-70 psi fuel pressure at full boost. At this level the lp will have dropped off a good amount. Think their the same price so why would you buy a pump that flows less where you really need it? With a proper fpr (not a b&m modifier) both will run like stock with the base pressure adjusted properly.