Dyno results

pwcracer · Apr 28, 2007

Today was the first day I had my car tuned on the dyno. What I found out, is my 255 lph pump is not keeping up with the fuel demands at full boost/rpm.. He thought it might be the filter, so he kept it a bit conservative on the dyno. He said once i fix the fuel issue, he thinks it will do 340-350..

Has anyone had problems with the 255 fuel pumps like this, or can you recommend a better solution?

Pokageek · Apr 28, 2007

pwcracer said:
Today was the first day I had my car tuned on the dyno. What I found out, is my 255 lph pump is not keeping up with the fuel demands at full boost/rpm.. He thought it might be the filter, so he kept it a bit conservative on the dyno. He said once i fix the fuel issue, he thinks it will do 340-350..

Has anyone had problems with the 255 fuel pumps like this, or can you recommend a better solution?

Makes absoutely no sense to me... That fuel pump is MORE than enough...

Let's use the formula that says

horsepower (HP) = lb/hr (fuel) / BSFC
If we assume BSFC of .5, then HP = 2 * lb/hr. Then, if we round the weight of a pound of fuel to 6 pounds HP = 12 * gal/hr. So, if we assume .5 BSFC, then you can actually multiply the numbers in the flow charts by 12 to compute supported horsepower.

For example, If you look up the flow rate of the 190 ltr/hr pump in the Technical section, you will see that it will push 36 gal/hr at 50 psi with a 12 VDC power source. If your engine is pumping out 500 hp when the fuel pressure is 50 psi [@ 12VDC], you probably won't want to use the 190 ltr/hr pump [36 * 12 = 432].

------

Correct me if I am wrong but 255 puts out 58 gallons per hour at 40psi = 58*12= 696 HP. ?

86bluecobra · Apr 28, 2007

Was I reading the afr wrong? It looks like it was way rich to me.

chaos254 · Apr 28, 2007

86bluecobra said:
Was I reading the afr wrong? It looks like it was way rich to me.

looks rich to me as well ... the graph for the afr is showing 11.0 up until 5000rpms

SVT3183 · Apr 28, 2007

how much boost are you pushing, what kb model is it, and what type of lower manifold?

pwcracer · Apr 28, 2007

He hooked up a fuel gauge to the fuel rails and showed me the pump dropping fuel pressure at higher rpm.. It could be a bad pump too.

I have a kb 1.5 with the gt lower intake..
7 lb

go-stang5.0 · Apr 29, 2007

I wouldent be surprised if its a fuel filter.....I'm making almost as much power as you w/ a 190 lph pump. Although my car is N/A...but still, that pump should be plenty.

tjh566 · Apr 29, 2007

not terribly rich for forced induction 11.0 is considered a safe afr for boost, 12,0 being almost lean, alot of people rund 11.5:1 on FI.

The fuel pump should keep up with it no problem.

MattZ281LE · Apr 29, 2007

His power is not that low. 340-350 should be pretty spot on for that combo.

I made 385/415 with a KB at 8# with a 255 pump 38# inj. My issue was a pegged MAF from going any higher. That was Stock SB AFR 165's Crower 15511 and Ported GT40 with the KB2200 Blowzilla.

I was hoping to break 400 with a KB...just wasn't in the cards.

You won't pull much past 5500 anyway, depending on your pulley combo. Those suckers build some heat. On a KB I would HIGHLY recommend installing the air inlet temp sensor AFTER the blower. Otherwise you will not have an accurate reading of the air temp being fed by the blower. If the sensor says you are putting 75* air and actually ramming 200* air in you signifigantly increase your chance of detonation. A good tuner should really be monitoring that especially on a blower.

- Matt

Pokageek · Apr 29, 2007

:OT: I am not sure I get it with these blown combo's ..why cant he get more than 330rwhp when you here about some many combos at 400-600rwhp?? Cant he just up his boost then?

BlackVert · Apr 29, 2007

Pokageek said:
:OT: I am not sure I get it with these blown combo's ..why cant he get more than 330rwhp when you here about some many combos at 400-600rwhp?? Cant he just up his boost then?

the kb is a lower rpm torque monster. the 1.5 tends to not be able to push enough air in the higher rpms to push the hp up in the higher rpm range.

just look at that torque curve ... high and flat

high hp with blowers is always attained at rpms 5000+, not the typical "on the street" rpm range.

94gsl5.0 · Apr 29, 2007

Pokageek said:
Let's use the formula that says

horsepower (HP) = lb/hr (fuel) / BSFC
If we assume BSFC of .5, then HP = 2 * lb/hr. Then, if we round the weight of a pound of fuel to 6 pounds HP = 12 * gal/hr. So, if we assume .5 BSFC, then you can actually multiply the numbers in the flow charts by 12 to compute supported horsepower.

Correct me if I am wrong but 255 puts out 58 gallons per hour at 40psi = 58*12= 696 HP. ?

Pokageek,

When dealing with a forced induction motor, BSFC needs to be calculated at .55 or even .60. Forced induction puts much more demand on a fuel system than a NA setup. Even if they are making comparable HP.

Not bustin your balls, just FYI on the BSFC...

Pokageek · Apr 29, 2007

94gsl5.0 said:
Pokageek,

When dealing with a forced induction motor, BSFC needs to be calculated at .55 or even .60. Forced induction puts much more demand on a fuel system than a NA setup. Even if they are making comparable HP.

Not bustin your balls, just FYI on the BSFC...

No Problemo man. Thanks for the info and thanks for contributing! I was looking for someone to add to our knowledge here Also, I think his 255 should still be enough even though not as much as n/a.

BV I did not know that about forced. Wow there are a lot of factors to take into consideration with forced which makes sense as to why you can really blow up with stock internals if you max too high!

DarkProphet · Apr 30, 2007

pwcracer said:
Today was the first day I had my car tuned on the dyno. What I found out, is my 255 lph pump is not keeping up with the fuel demands at full boost/rpm.. He thought it might be the filter, so he kept it a bit conservative on the dyno. He said once i fix the fuel issue, he thinks it will do 340-350..

Has anyone had problems with the 255 fuel pumps like this, or can you recommend a better solution?

I had that problem exactly. When I was getting my car tuned, I was running out of fuel at around 4500, and I was around 340hp at that point. I added a Vortech T-rex inline IN ADDITION TO my 255lph pump, and now have no problems even with a smaller pulley! (my car was tuned with a 9# pulley making about 6#, I swapped it out for an 11# pulley so I make more like 8).

It sounds like you have a very good and responsible tuner. I would rather have it a bit rich to compensate for a hot day with the blower pushing really hot air!

Dyno results

pwcracer

Attachments

Pokageek

Active Member

86bluecobra

Advanced Member

chaos254

SVT3183

Member

pwcracer

go-stang5.0

New Member

tjh566

New Member

MattZ281LE

Pokageek

Active Member

BlackVert

94gsl5.0

New Member

Pokageek

Active Member

DarkProphet

Similar threads

Dyno results

Attachments

Active Member

Advanced Member

Member

New Member

New Member

Active Member

New Member

Active Member

Similar threads

Privacy & Transparency

Privacy & Transparency