wahlbro 255 fuel pump..will it over run injectors?

[boostdog]

i just put my wahlbro 255 in and the car feels a little sluggish..am i now running extremely rich? and will this hurt my injectors by over running them? i have yet to buy a fuel regulator and was wondering how easy they are to tune to the systm. any info will help as i am still new to this dsm game!

[kjewer1]

The 255 wont overrun the injectors, it over runs the regulator. So your pressure is higher, but no where near the top of the injectors range. You should only be rich in closed loop (idle/cruise) but should be fine once you get over some boost level (7 psi for example, varies by setup but thats a typical number). When you get the adjustable reg, you really shouldnt "tune" with it so to speak. Just set pressure to stock (38 psi for 1g, 43 for 2g) so the ECU can do its job properly again. And its very good at what it does, when everything is correct

[KevinE326]

which regulator should he/me buy????

and isnt 42psi on a 2g a lil high?

[JoeWagon]

"43.6psi at zero psi" is stock 2g at idle. Of course, it rises in direct proportion (1:1) with boost pressure.

[kjewer1]

I run the aeromitve regulator that most dSM vendors sell. Its about 130 bucks, but you have to buy line, fittings, and rail adapter. Bushur makes a bolt on version of that regulator for 275, only works on 1g fuel rails (they can be swapped to 2Gs, just not the 90s). Fullthrottlespeed makes a bolt on for both rails, but I have no experience with them myself. They are about 140 bucks IIRC.

[TurbosR4me]

Doesnt the Wahlbro 190 handle plenty of HP, considering you dont need to upgrade the FPR. I dont understand why people jump straight to the 255. How much power can the 190 handle???

[kjewer1]

You cant measure a pumps capacity in HP. Different cars use fuel more or less effciiently than ohters. I put a page up on my site that demostrates this, in the tech pages section. But lets look at a typical example. Pump gas AFR of 11:1, 30 psi boost, pump is reqired (everyone should rewire!). So the 190 flows 104 LPH in this case, which is 27 gph, and 162 lb/hour. Multiply by 11 (AFR) to get airflow/hour, 1782, divide by 60 to get lbs/minute, 29.7. Now, I cant remember the last time I Was below 30 lbs/min on pump gas. Thats a 14b maxed out, for reference. Let say you only run at up to 15 psi on pump gas. The pump will flow 163 lph! in this case. Same example as above, we're good to 47.3 lbs/min airflow, which is just under the limit of a 50 trim, and just over the limits of a 20g.

Now the important thing to take away from this is how much fuel pump flow varies with boost pressure! I used 15 psi and 30 psi just because its easy using RRE page (http://www.roadraceengineering.com/f...pflowrates.htm). But you can get the flow graph for any pump, and do the math at any fuel pressure (base pressure plus boost pressure equals rail pressure). I highly recomend everyone do this! Stock pumps are listed there too. It would have saved me a motor if I did this a month ago.

Now, lets look at the same pump but on race gas, with an AFR of 12.5:1 for example. Should come out to about 13% more capacity, since we are leaning out. I get 34 lbs/min airflow and 54 lbs/min airflow for the 30 psi and 15 psi examples, respectively.

Now, use the 10 HP per lb/min of airflow rule (thats why I converted all this to lbs/min airflow capacity). Thats how much power you can make, IF you are using that fuel effectively. That means perfectly tuned.

Now, some poeple tell me I should be fine with a 255, people have run 10s with it and I'm still in the 11s. Well, lets look at this differently. What if the 10 second cars are lighter (almost garanteed!). Take tym switzers car, ran high 10s on a 20g. Would a 255 supply enough fuel for a 20g? Using our examples above of what the 190 can do, I would certainly say yes. Would my car ever run a 10 on a 20g? Not a chance in hell at my weight. So you can see that you cant use track numbers to rate pumps either. You have to use airflow, AFR, and rail pressure (determines actual pump flow). And remmeber that the flow the pumps are named after are not using the variables like boost pressure and voltage that we typically run in our cars, thats why we had to use the info on the RRE page, or the flow graph if you need to find a number in between what RRE gives you.

When looking for my new fuel setup, I spent a lot of time doing this math. The pump I'm using now (aeromotive A1000) will flow 435 lph at idle (43 psi fuel pressure) but only 315 at 30 psi boost (73 psi fuel pressure). Even for a huge pump, it still drops off dramatically as boost goes up. But this is still good for 100 lbs/min airflow, which I Could obviously never reach at only 30 psi. So as you try to raise airflow, you raise boost, which LOWERS pump flow. So that 100 number will drop. Have to be careful!

I hope people find that info useful.


EDIT> Dont be afraid to double check my math and make sure I did it right. The only other assumption I made that wasnt mentioned is the weight of gasoline. I use 6 pounds. Water weighs 8.33 pounds per gallon. Typical pump gas is .76 specific gravity, or .76 times the weight of water, or 76 percent the weight of water. Thats 6.33 pounds. The sunoco race fuel I use (NOS Supreme 117) is .724 SG. Or 6.03 pounds per gallon. So my race numbers will be accurate, while the pump gas numbers will be about 4% low. Since you have more fuel per gallon. You can look up the SG for any fuel, even whatever pump gas you typically use.

[JoeWagon]

If i could actually follow that, i'd do it for my future setup. At elevation I expect fuel requirements to go down proportionally with airflow (from atmos. pressure). If I'm going to be buying an AFPR, is there any reason not to go with a large pump like the supra pump? Expect for the fact that people can't run stock fuel level gauges with them? I'm going as big as possible the first time, maybe the Walbros rated for like 390 or whatever? bosch? cosmo? aeromotive?

[BoostedSpyder]

damn... i get so excited when Kev is dropping his knowledge on us... OK time to re-read that!

[kjewer1]

If you are doing a reg, by all means go big on the pump. The 255HP (I have the regular version, the HP is better at high boost) is actually pretty decent, good to ~70 lbs/min using similar criteria to the examples above. And its cheap and a simple drop in. This is the first time I have heard that a supra pump doesnt allow use of the level guage though. A know a bunch of local guys with supra and cosmo pumps that still use the guage. Is it only a certain year or AWD/FWD configuration?

To simplify what I said before, here is what you are doing to figure this out. Find the flow of the pump at the fuel pressure in question using a flow graph or the numbers on RREs page. Then convert to gallons per hour (I have a program called "convert" that makes this a no brainer). Then convert to pounds per hour using the 6 lbs/gallon figure I mentioned, or to be more accurate, calculate the weight per gall on fo the fuel by using its specific gravity (density expressed as a percetnage of the weight per volume of water). Now you have lbs/hour fuel flow. Using your target air fuel ratio (AFR), you know that for that much fuel, you'll have more air. 12:1, you'll have 12 times more air, etc. So just multiply. Now you have lbs/hour of air. Divide by 60 to make that pounds per minute. Simple!

[95_GSX]

Kevin, you cease to amaze.

[TurbosR4me]

Wow....Thanks Kevin. My brain hurts now.

[JoeWagon]

I thought it would not install with the gauge. Looking into it more, I'm seeing posts on tuners saying:

I just installed a Supra pump on my '96 2G AWD.
It went fine, but there is NO WAY to hook up the
wires for the fuel gauge.
The Supra pump is SO DAMN HUGE it totally blocks
off the electrical connector socket for all the wires
but (fortunately) the pump power wires.

I read every thread, every VFAQ before I got this
pump and saw NO mention of this.

Anyone else had this problem?

I mean, the pump is about 3 times (at least) bigger
than the stock pump. I can't believe I've never
heard of this problem before. During the install, I
found myself saying "I wish I had bought a Walbro.

While others say it installs fine.

here's a picture where it works:


and the reply is

That's my problem. It wasn't "a little close". The fuel pump covers up the ENTIRE connector. I tried bending it to the side... no joy.

Maybe if I know it CAN fit, I'll mess with it until it does.

[kjewer1]

Cool, thanks for the info. I had never heard of that! I would just rewire that bastard somehow and drive it on...

[boostdog]

i went with the 255lph instead of the 190lph simply because i did not want the pump to be the weak link down the road. it was the same price as the 190 and installs the same. my ? back would be why not?