Jump to content
SAU Community

Recommended Posts

Hey guys,

Im stumped on a fuel issue in my R34 GTT,

It's hitting 100% duty cyle at 11.9 AFR up top at around the 500rwhp mark. Any help would be appreciated!

I've attached some screenshots of my map if it helps? Fuel pump has bigger wiring to it with a relay and direct battery connection.

Mod list below.

Standard RB25 NEO

Steam pipe high mount manifold

Garrett GTX3582R V-band rear housing

Turbosmart ProGate 50mm

Bosch 1000cc injectors

Proflow fuel rail

Tomei fuel pressure regulator

Plazmaman plenum

Haltech Platinum Pro ER34 Plug-in

Haltech 4 bar map sensor

Haltech boost control solenoid

Haltech flex fuel sensor

Splitfire coil packs

Custom stainless dump and front pipe

100 cell Venom cat converter

HKS HighPower 4" cat back exhaust

600x300x100mm FMIC

Tial 50mm BOV

Walbro 460lph E85 fuel pump

post-89539-0-10111200-1412750392_thumb.jpeg

post-89539-0-09214700-1412750398_thumb.jpeg

post-89539-0-69661400-1412750703_thumb.jpeg

Edited by TheGeniusMoose

how's your fuel pressure though?

I'm hitting 97% with 875cc injectors on E85 with about 1.6bar boost - however running 3bar base pressure. Newer injectors don't mind more fuel pressure, so once I need more "injector" I will bump the base pressure.

interesting. the Walbro pump should be able to handle more than that for sure. As well as the injectors.

How much boost was used before the injectors maxed out?

perhaps the fuel pump isn't genuine?

Do you have a direct feed for the pump?

I believe those ones can draw close to 20A at high boost. That's more than I'd be comfortable putting through the factory fuel lid connections.

Maybe drill a hole in the lid and poke some high current wires through then seal it up

Pump has direct battery feed with a relay, geniune pump. The lid has nice thick wires and does not get hot.

24psi boost.

Edited by TheGeniusMoose

next question is, did the tuner tune to AFR or to Lambda? correct Lambda should be around the 0.81 mark... if your tuner tunes using afr his calculations could be way off in which case it's probably mega rich hence why its maxed

I'm honestly not sure.

The dyno chart shows that its at 11.9 at peak power. I didnt take a picture however.

I'm also using standard fuel pump cradle, standard lines under the bottom of the car.

Edited by TheGeniusMoose

next question is, did the tuner tune to AFR or to Lambda? correct Lambda should be around the 0.81 mark... if your tuner tunes using afr his calculations could be way off in which case it's probably mega rich hence why its maxed

Any time anyone says an AFR number when talking about E85, and the AFR sounds like a petrol AFR, then just pretend the fuel is petrol. It's that simple. No-one would tune to a real AFR of 11.9 on E85.

  • Like 1

What fuel filter are you using?

I'm not joking. I upgraded the injectors in your situation and had a limitation at that exact point.

Mind you, this is 372rwkw. It's getting 'up there' for 1000s.

If your AFR's start OK then start to leeeean out to about 12-13 as you really get into it.... seriously try something else instead of a Ryco filter. Try a dyno run without one.

Will try with no filter just too see what happens. It is running a cheap ryco one at the moment...

Who should I be taking it to so I can get this shit sorted? I'm in Brisbane.

I have had a few 34's doing the same thing lately on ethanol, large injectors suddenly maxing as the fuel flow drops off. As Greg said, we removed his filter while it was on the dyno and the entire fuel map went rich.

His Ryco had only recently been changed too. We replaced it with a stainless mesh filter.

Exactly, that is how we found the flow was dropping off. You have no idea what is happening without a gauge on the feed line, and you need to be on a dyno if the gauge is in the engine bay.

Speaking of which, it seems some factory regs can be too small for the 460L pumps, they don't bypass enough. The S15 I worked on recently was tuned at 60psi at idle, no wonder the car wouldn't idle well with twice the fuel pressure it should have had. It is definitely an important test that should be checked after any major fuel system mods.

Exactly, that is how we found the flow was dropping off. You have no idea what is happening without a gauge on the feed line, and you need to be on a dyno if the gauge is in the engine bay.

Speaking of which, it seems some factory regs can be too small for the 460L pumps, they don't bypass enough. The S15 I worked on recently was tuned at 60psi at idle, no wonder the car wouldn't idle well with twice the fuel pressure it should have had. It is definitely an important test that should be checked after any major fuel system mods.

Fuel gauge on the feed line? Is a gauge on the reg not able to tell you correct fuel pressure?

Well I just bought a speedflow filter with barb fitting to replace current ryco one and a new bulkhead fitting for the cradle as a few people have said the stock fitting is very small. I'll have a fun weekend ahead of me!

post-89539-0-08831400-1412891598_thumb.jpg

Edited by TheGeniusMoose

my walbro e85 pump is making 450rwkw at 24psi on e85 no problems so don't think its the pump

I think your injectors are at the limit, my old 1200cc injectors were at 100% duty at 409rwkw with 55psi base pressure

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • Apologies for the long post, but needed somewhere to lay out the entire timeline of events and actions taken:   I've got an 89 GTR with a R34 RB in it. It's been running great all year, driven probably 500KM in the last month. It's not my daily driver, just a weekend fun car.    Build info: R34 RB26 - HKS 2.7 stroker kit, HKS adjustable cam gears, HKS turbo upgrades, Trust intercooler, R34 factory DENSO 440cc injectors, JUN chipped/tuned R32 ECU. All of this work was performed in Japan back in 2019.    Thursday 10/2/25 - It's a nice day and decided I'll drive it to work, I start it up in the garage and I notice it took a few extra cranks and sounded a bit funny. I figure maybe it was just because it was a pretty chilly morning. I pull it out into the driveway to warm up a bit before leaving. As I leave the driveway, it feels very off and sounds like a misfire. I pull it back in the garage to deal with after work and take the daily to work. I was able to diagnose it as a cylinder 5 misfire with the old spark plug test (unplugging each plug until a sound change with the engine running). I take off the whole ignition system, ignitor, plugs, spark. *Important note, it is still on the R32 ignition system with the separate ignitor system. I test each system with a multi-meter and nothing presents as a smoking gun. I put it all back together and it starts up no issue. I go ahead and order the PRP R35 ignition conversion kit. It should arrive today (10/13/25)   Friday 10/3/25 - Another nice day, car starts up great and drives great all day. Very pleased that everything seems to be OK   Sunday 10/5/25 - Decided I'll take it to play some golf, load up and drive to the course about 25 minutes away. Drives wonderful the whole way there, I pull in the parking lot and the engine completely comes to a stop. I do not recall if it sputtered at all, but just remember all of the sudden the engine was off. I roll it into a parking spot, try to crank it back on and nothing.  It'll crank and crank and not even try to start. End up getting it towed back to my house and push it up into the garage.    Items I have checked: Fuel in the tank Fuel Pump relay Fuel pump fuse  Spark Plugs & gap Coil packs Ignitor    I know the cylinders are getting fuel as the plugs smell like fuel after a start attempt. I tried spraying starter fluid into the manifold and cranking and not even a sputter.    I decided to do the live CAS test (removing the the CAS, ignition on and spinning the CAS stalk to see if the injectors pulse and spark is active). All of the injectors were pulsing and I have spark at the plug. The half-moon end of the CAS did seem very loose, I'm not sure how much play is supposed to be there, but it was more than I expected. There was no in/out play of the shaft, just the tip end that is pinned on had quite a bit of play.    CAS Play video   When I put the CAS back in, I stupidly did not re-time the engine. I know I need to do that tonight, however, I do not think it will start given it seemingly was not the issue. My plan is to do the PRP R35 coil kit and retime the engine at the same time.    I plan on ordering the Haltech Nexus Plug-in ECU once they are available again, but ideally would like to get this sorted before firing the parts cannon at it and potentially adding more variables.    Anything glaring that I am missing here, I'm a bit at a loss?          
    • Get it on a dyno. Get something logging Consult. Run it up and find out what is causing it.
    • Looking for a plenum for rb25 de+t neo  Not looking to push much power maybe 300kw at the wheels, is there much difference in flow for Freddy “Greddy style” compared to original Greddy or options like Proflow or Otaku garage?    I won’t be porting the de Neo head for now as I think it’ll be fine 280-300rwkw but appreciate the help and any experiences anyone has between them and any advice. Thanks  Looking at this plenum for now below 
    • engine wise almost no mods: stock ecu Greddy front mount intercooler Greddy forward facing intake w R33 TB stock fuel system, stock injectors, rail etc. Kakimoto racing hyper 3 inch exhaust system Apexi intake filter New NGK –R BCPRES (.8 gap) plugs  
    • Nice one @Pac - looks like a fair few 1600's there! 
×
×
  • Create New...