Hi all,

I've been working on getting my 1993 Touring back on the road (properly) for the last year or so. I'm running into some strange behavior at higher RPMs/boost levels while logging using Xavier's FCTweak. Mods/pertinent maintenance below (everything in the last 500 miles):
- Stock injectors tested and cleaned by Injector Rehab
-Simplified sequential, new solenoids, new check valves, new vacuum lines
-New UIM gasket, new TB gasket, blockoff plates installed with RTV
-New turbo lines with boost pills
-HKS filters, Twinpower, FMIC, RB exhaust, downpipe, PowerFC
-New fuel filter
-Walbro 255 (from SakeBombGarage so I trust it's real)
-Fuel pump direct wire (per Dale's instructions)

I'm seeing 90%+ duty cycle at 10 PSI of boost and imagine it can only be a few things:
-Bad pump
-Bad FPR
-Bad injectors

When I reinstalled my injectors I noted they were physically different (I think the secondaries were physically longer IIRC). Can anyone fact check me on this? Is it possible I plopped the primaries in the secondary rail (and vice-versa) by mistake?

 

red is secondary and purple is primary. the primary rail requires modification to fit the the secondaries. when you installed the pump did you delete the factory connection to the pump with the o-ring and that weird spacer thing? when removing the stock pump for an aftermarket one and reusing everything, the odds are VERY high you will have a compromise at that connection and you end up with low fuel pressure under load.

 

Appreciate the reply! I was pretty certain the injectors wouldn't be easily swappable. When I installed the pump I was bummed to find that the factory parts didn't seem to mate up (that was before I found this thread: https://www.rx7club.com/3rd-generati...sting-1150079/) so I cut the factory hanger and used fuel hose + clamps for the install. That should, at least, rule that part out. I'll pull the pump tomorrow to inspect everything I guess. This is the price I pay for changing too many things at once but this car was an absolute basketcase when I bought it.

 

is the fuel hose submersible? they are not all created equal. you also don't want to be using perforated worm clamps. if the fuel pump install checks out, it would be worth checking that the vacuum line going to the fpr is plumbed correctly. i cant say its all that common for a stock one to go bad..... not that I've ever heard or seen anyway. at what load point are you hitting 90%?

 

The submersible question is one I have to pull the pump to answer - I've been wondering about this myself. I used "fuel hose" from the local auto parts store without considering the difference between "I like fuel in me" vs. "I'm cool with fuel on me." I'll likely replace it to be safe. "Yes" on the worm style clamps at the moment. I'm assuming the best bet is the single use crimp clamp in this situation? I'll have to check my logs to answer the question about load!

 

you likely have carb hose in your tank. 99% of the parts store carry carburetor hose which has printed on it "NOT FOR FUEL INJECTION SYSTEMS". They don't care and no one else does either lol

non submersible hose saturates and then ruptures in the tank effectively putting a hole in your straw and causing low fuel pressure under some or all conditions. this creates a cascading effect of other issues. gates and dayco sell submersible 5/16 hose. its a very expensive and small section of hose but for good reason. the clamps style you want is a fuel injection clamp. its a smooth band clamp that does not eat into the hose. the parts stores usually carry a variety pack.

 

Submersible fuel hose is expensive, and parts stores might not have it. Pegasus sells the 5/16" size submersible hose (which works if you are following the instructions posted in the FDAuto youtube video) for $2.59 per inch. I bought 6 inches for my car, I think I used about 4 inches, and it could have probably worked with 3 inches. https://www.pegasusautoracing.com/pr...p?Product=3494 I also used their stainless steel clamps for 5/16" fuel line, which were nice. Part number 3617-15 on the Pegasus website. And a couple feet of their 5/16" Gates barricade MPI fuel line, ethanol rated, to replace the feed and return lines that go into the factory fuel bulkhead connector.


Fuel pressure has been good so far, but I also added new bulkhead wiring connectors to handle the current draw of the aftermarket pump. https://www.efihardware.com/products...inals-hex-head They arrived pretty quickly despite shipping from Australia.

 

On the topic of buying fuel line hoses, look for the SAE specification "SAE 30R10" printed on the hose for hose used in submersible/in-tank applications. That's the expensive stuff that will survive being submerged in gasoline/E85 at high FI system pressures. If you don't see that spec marking on the hose, or your vendor can't confirm that's what you're actually getting, don't buy it.

For high pressure FI applications outside of the gas tank, "SAE 30R9" specification hose is fine. That hose can handle the high pressures of modern FI systems, and is compatible with gasoline/E85 fuels, but is NOT rated for such use submerged in fuel.

 

I've ordered the new lines and clamps from Pegasus. Hopefully those arrive this week; I'll update the thread if this was my issue!

 

if you're having a hard time hitting the target AFR and the FC Tweak keeps adding more injector duty, that is a sign that you have some kind of fuel delivery problem.
what happens is that FC Tweak sees that it doesn't hit the target AFR, and tries to hit it, and since its a potential mechanical thing, it can't.
i ran into this with mine. i needed more fuel pump, and with that FC Tweak is happy, and injector duty came down. it went from not quite hitting the target AFR and duty in the 90's, to being a little rich at like 80% duty

 

Well the front rotor ate itself last night so that's that I guess.

 

Say what? How'd this happen?

 

There's a long story about the history of this car but the gist of it is that the seller provided me with rebuild receipts indicating 1000-2000 on a freshly rebuild motor with a full Atkins seal kit. I suspect that it wasn't done entirely properly as there were a host of issues with the car that took me 12+ months to resolve. Again, caveat emptor, I'm an idiot who didn't perform due diligence prior to purchasing. The front rotor has always had compression in the 80s. Yesterday afternoon it was in the low 80s on all faces hot. I drove the car last night and the engine popped at around 70% throttle in 3rd gear at 6000 RPM, 8-9 PSI of boost, and 10.5 AFR. Front rotor is now showing 40PSI on all faces but I'll need to retest today once the battery charges.

Fuel hose was a good call: AFRs were rock solid all night with no signs of starvation. I'm probably out at this point as further pursuits with this car would only be due to the sunk cost fallacy urging me forward. Kinda cool to have a 20 year dream smashed in seconds. I've put about 500 miles on the car since buying it lmao.

 

That sucks! But this is a great opportunity - go through EVERYTHING and make sure it's all up to spec. Fix any poor workmanship from the previous owner. Take your time.

Once done you'll have a setup you KNOW is good.

Dale