2JZ less power after pump upgrade

[thrashlux]

Ok the results are in they were not quite as i expected but explain why i have had over fueling problems
Once again we can all come up with the theory of what should happen but sometimes when we actually do it it works out a little different

what I did was ran both fuel pumps with a permanent 12 v one at a time through the same lines (3/8) and fuel filter through the fuel rail so as not to have any diferences other than the fuel pump its self
I mapped the regulators output pressure from 25 INHg to 20 psi sense pressure using a vac pump and pressure regulator this is what i found

first i did the standard toyota pump (LH is sense px ,RH is fuel px)

25 inHg =35psi ,20 inHg=32.5psi ,15inHg=35psi , 10inHg=3psi ,0psi=41 psi ,10psi=51psi ,15psi=56psi ,20psi=61psi


then I carried out the same test with the large fuel pump

25InHg=34psi ,20InHg=37psi ,15InHg=39psi ,10InHg=41psi ,0psi=45psi ,10psi=56psi ,15psi=61psi ,20psi=66psi

It was as I expected the large pump has increased the presure across the board by about 4-5 psi
what surprised me was it actually got worse the higher the boost level
off boost it was 4psi on boost 5psi
well the test proved that the standard fuel pressure reg cannot flow enough fuel when connected to this kind of setup causing the pressure to rise above std levels and more so on boost which would be exaggerated further by larger duty cycle times while on boost making over fueling even worse

It also proves that the regulator has a linear output pressure curve ie 1psi more map for 1psi more fuel rail pressure not a rising rate curve

I think there is a lot of confussion with fpr's between rising rate and rising pressure on boost because a linear pressure reg will still raise pressure when boost is applied but at a linear rate where a rising rate will raise pressure at a non linear exponential rate as you move away from 0 psi under boost

Now what I need to work out is how to solve my problem
these are some of my ideas
!) buy a new aftermarket fuel fpr (linear)(favorite option)

2) get a second std fpr and fit it in the rail some how and recheck the pressures under all map conditions(could do this soon from local parts as many wrecked toyotas on the island)does any body know if any other engines run an fpr with the same out put perameters or will I have to test them one by one to find out.

3) install a restrictor to limit the fuel flow to some where close to the std 2j fuel pump's flow (on the high side) so the std fpr can handle it
(this would be no diferent to running std steel lines) and recheck under all map conditions

4) run a dropping resistor to the fuel pump to reduce its output
and recheck as above

So guy's let me know you thoughts also if any body knows of a place i am guanteed to get a large linear output fpr (not rising rate most on ebay are)
thanks thrashlux

[Norbie]

Sorry, to clarify; I wouldn call a linear FPR rising rate but ive known of them to be called that cause they both have pressure rates that can rise.

Wrong, the pressure rises in a linear FPR but the pressure rate does not rise. You're right though there is a lot of confusion around this.

[thrashlux]

I cable tied the fuel pressure guage to the windsreen wiper at lunch today and went for a full power run up the runway
The guage sat at 56 psi at 10 pound boost (the same as the static test results)
when i plant my foot the fuel pressure laggs behind the boost by a split second and at the exact moment the fuel pressure passes through 50 psi at 10psi boost you can feel it wanting to go then the fuel pressure rises and it looses power

I tried running a restricterbefore the fuel rail to try and limit flow, statically (eng not running) through all of the same sense line pressures but the out put was not stable so then i tried bypassing fuel from the pressure to the return with a ball valve this was stable but failed the road test because as the engine used more fuel it threw the balance out and the pressure dropped off below target pressure

Now i have had another idea, at the moment the off boost performance is fine even with the 4 psi over target fuel pressure. This probably due to the low duty cycle being used at this power. The afr would not be as markedly different. What i will do is treat the fuel pressure reg like a waste gate and let it think it is at 5psi when it is actually at 10 which will put the output smack on 50 psiFP at 10psiboost (target) as per my tests
I will set it up static first then run it carefully watching the FP guage
this will do for now as it is safe( all on boost FP figures as per factory)until i come back to aus for a holiday or go to the states sometimes

Ill let you know how it goes

[mic*]

Yeah sounds like a your best idea. A restrictor in the vac reference to the FPR?

Just out of curiosity did you notice whether the small pump was returning much fuel at ~50psi?

[thrashlux]

The small pump was returning fuel at 50psi though nowhere near as much as the big pump(this is staticly eng not running) with the eng under power I am unsure


with the set up i have now the engine revs cleanly all the way to redline and makes more power than without the restrictor and bleeder or the small pump
I still have the fuel pressure gauge fitted what I have noticed is that it feels a little bit slower to get on boost than with the small pump I think this may be because the fuel presure at 0 -5 psi boost is still 5 psi higher than it is suposed to be causing it to be a little fat in that range hence the delay in response
so i will still be looking to get a new fpr soon

cheers