98 topfeed conversion fuel supply problems
 

So, Here it starts..

Car is a my98 GT turbo, Boost control comes from an AVCR
Has an ESL ecu with motorsport pack, tuner is well known with the system and mapped cars before.
I Have AFR, Fuelpress, oil press, oil and water temp gauges (No, not from ebay..) for monitoring.
Turbo is a Kamak TD05H 20GTX STS

Build up the engine bay from scratch from a working car,
Since phase 1.5 injectors are hard to come by, and i own a cnc machine, i made the conversion kit myself for STI topfeeds to fit them into 98 manifold.
That works, no leaks.

https://scontent-ams2-1.xx.fbcdn.net...66&oe=56C36E25

System is made parralel, with all AN6 lines, Y pieces. return system.


When we did the remap and got to the boost adjustments (we went from 0.8 to 1 to 1.2 bar), he saw the AFR leaning out past 6k rpm, it went from 11/0 to almost 13/0.

We have to change the tables to around 8/0 to get them to a true 11/0 afr.
We later saw the fuel pressure rising to 3.8 instead of the 4.2 we needed (3 bar base pressure). Sensor mounted in FPR.

He suspected the FPR to be faulty(Tomei Type S), so replaced that with a Turbosmart FPR 800. also the pump could be bad, so replaced the 4 week old fake walbro for a new genuine walbro 255..
Still problems!

Then checked pump voltage.. on 3 bar i lost about 2 volts in the wiring, at 5 bar fuel pressure about 3 volts loss.
Ran new wiring directly to the pump. (6mm2)
0.1v loss trough 5 meters of cable..
Still problems!

Than checked without fuel filter(it was new, but nvm), no solution.

Fuel flow through the system was checked, and yielded good results.
With a flowmeter in the return to tank line, i measured the following:
3 bar pressure: 220L/h
4,5 bar pressure: 155L/h
5 bar pressure: 135L/H
Measured @12V supply, engine not running.

This is alright, according to the pump flowchart.

Still no solution so far..

Than changed the fuel system to a semi returnless feed,meaning the FPR is in between the rails and the pump, close to the rails.
Still no solution, only got worse since the fuel pressure fluctuates now as wel..Sensor mounted in the rail.

Im out of options now... dont know what to check anymore..

Maybe someone has some inside info or has dealt with this before?:cry:

I have not checked yet if it does the same with oem rails/injectors since 380cc isnt enough to feed the 20G @1.2 bar.

Return to tank flow is not true flow, the pressure reg is a restriction

Install the fpr in the normal position

Bin the Walbro pump and get a proper one, Scoobyworx sell a Colossus 340 litre per hour pump

are the injectors getting to 100 % idc? ... could be

Pink 503cc injectors wil max at about 390 bhp dependant on fuel quality mods and the afr you choose to use

bob

True, however since i measured in the 0 pressure line, it is the flow the pump has wilst pumping under pressure. No losses as the engine was not running nor were the injectors open. Flow was tested in paralel setup and semi returnless and yielded same results..

My tuner has had results up to420 hp, maxing the pink injectors., (about 11.2 target afr) and up to 480hp with the walbro pump..

We are getting up to about 90idc, however the power is about 250hp max.

Both i and the tuner, as does my parts supplier do not think the walbro is maxing out. This is consistent with the fuel pressure gauge, as it is not dropping pressure, even at 100idc.

It not just the walbro maxing out it's also about reliability

I can see the point in that... however shouldnt be the issue now.. have to get it to work right first before i will start changing random working components.

Took the time to check the rails, filter etc, everything spotless and clean.
Ran a line directly from the pump to the rails, to make sure the steel supply line was OK.

Same problem.

@darrell, could it be the walbro..? have you ever seen this problem?

So... I put the base pressure to 4.2 bar,

Went logging in 3th gear,

I literally saw the pressure drop to 3.9 approx..
have ordered a new bigger pump..

Bigger 340lph pump.. No improvement.

Does anybody have an idea?

If not fixed end of this year car will be sold in parts. I've had it.

stupid idea perhaps: but do you have any other fuel pressure gauge to use?

I used depo gauges before and they were not very accurate at all.

For boost gague i had 3 gauges, all from the same place boost set at 1.30

Apexi ECU reads beetween 1.30-1.34
BLITZ SBC I-Colour Spec R reads 1.27-1.29
Depo gauge? well it was reading anything between 1.3 and 1.5 bar depending how fast i was boosting up lol.

When i overboosted, Blitz went up to 1.39 , depo read 1.7. That's a very big difference. and note the gauge was about 2-3 months old, bought from new from their supplier "xenon-uk".

As a rule of thumb I said them depo gauges are not good enough for accurate reading, but more for an idea of how things go. So it would be good to see a different gauge, see how that will read.

Presumably no split in vac hose to fuel pressure regulator?

I guess you've tried regulator in many positions, so unlikely you used the same hose each time.

is the vac pipe connected to the fuel regulator

Use a Mityvac or similar to apply +ve pressure to the fpr reference line with the engine idling.

Do you see a corresponding linear increase in fuel pressure, and a progressively richening AFR?

**Yes.


*
Video is tested with 1.2bar of pressure with a diagnostic pump directly to the FPR. thats why fuel pressure isnt rising normal 1:1 rate.
Mixture doesnt richen under closed loop lambda, goes to 11afr in MAF (under full load) operation. and than leans out in top end to 12. (after about 6200rpm)

FPR reference Hoses are replaced with new ones 2 times, both 4 and 6mm tried.

I import the Depo's myself and had very good result with them with over 60 gauges sold.
yes, i tried with a normal FP gauge with a seperate line to the windscreen, results were exact the same(appart from possible reading error)
Whether or not its a depo, if it runs 4.2 under 3 bar base+1.2bar diagnos. pressure, needle should stay put.

Turns out it was likely a problem with the tank cover connectors.Replaced them with a long wire+pump plug and a PG gland, and the problem wasnt as bad.

Went mapping again,
Pressure now good even up to 1.5 bar boost. (we couldnt get any higher due to a weak wastegate)

Now for some new problems.. Uppipe gasket leaking, Misfiring above 6500rpm and the boost wont go over 1.3 bar:freak3:

The brackets that hold the fuel rails did you buy them or were they on the manifold if you bought could you tell me where you got them from please

Cnc'd them myself..