I got my re-tuned for 13psi. Everything went very well during the tune. The only thing that i didnt like was the 100% injector duty, but the car still held a solid 11.1 Afr. but thats less of my worries now.

I drove the 30miles home, WOT couple times on the freeway 3rd and 4th gear. Pulled very nicely. As im about to exit 30mintutes later, i do another 3rd gear WOT and notice its not pulling too hard. I exit, then do a 30mph 2nd gear WOt and the car start BUCKing Very badly with boost comming on and off. Little power. Good vacum, good boost reasponse.Idle is fine. MAP sensor is good... WTF is going on!

 

Your on ******* 13psi stock twins and fuel system.
Im surprised you dont hit fuel cut every 5 seconds... 100% injector duty, holy ****.

I say detune to 11-12psi, get a new fuel pump, and if you still got money.. bigger injectors.

Good luck with everything.

- Artin

 

I just installed a walbro before tune. I think it is fuel cut thats happening\. I also do have a 1/5 gas tank which is now what i think is the culprit.


edit: maybe i didnt instal the pump right? and on the bumpy road back something went wrong?

 

Im not sure about the 1/5 gas tank thing.

But im thinking either the pump wasnt installed correctly or its not gettin a full 12v. Theres a rewiring how to on ClubRX but i think its down right now.

Fill up the tank and drive for like 30 minutes and do some WOT runs and see if it happens again. If it does, then theres the possiblity of the gas slushing around (not sure if the stock gas tank is baffled) and the engine is getting fuel surges because the fuel pump/sump not sucking any actual fuel.

If it doesnt happen, well then that was probably the problem.

I can look at the pump this week if you want.


Also... wtf is up with the 100% injectory duty.. thats scaring me.

 

You have a PFC. Fuel cut is not 12psi unless it's programmed that way.

I'm not a tuner, but it seems that whoever tuned your car to use 100% injector duty is a complete idiot. 100% injector duty means 0% margin against blowing the engine. 12-14psi is doable on a stock fuel system, but only if you're getting it without maxing the injectors.

Were your injectors ever cleaned and flow tested? Have you changed your fuel filter lately? Have you tested/verified the fuel pressure?

Dave

 

Your running out of fuel. Your injectors are maxed out. You are at risk of your injectors sticking open. The dyno will never be able to push the amount of air through your intercooler as driving on the highway will. On the dyno you tuned it to 13psi but when you get cooler air you might be going up to as far as 14psi therefore you might be leaning out. I had this problem once and then I just upgraded to bigger injectors. I didn't continuously drive it in that condition. BTW that was at 13/14psi on the stock twins.

R.K.

 

If you were low on gas that could be part of the problem, but 100% duty cycle is never good. I really cant run my fd lower then a 1/4 tank. The low gas thing is a problem with many fd's. The baffles are not great, and a lot of people get problems around turns. Some people add those styrofoam block things, but I would focus on that injector cycle more then anything else in your case.

goodluck,
-josh

 

Don't add those fuel cell foam blocks. I'm working on that problem, and I'll post my results publically soon.

Dave

 

I was thinking about it yesterday and it has to be one of these... or all..

1. 100% injectory duty cycle is clipping the injectors and overloading components of fuel system

2. 1/5 full gas tank + turns + bumpy roads = problem is obvious

3. possible FPD (fuel pulsation damper) malfuntion

 

I doubt it's the FPD - it's been shown that running without an FPD is no problem.

Perhaps you meant FPR? Even still, a bad FPR won't change your injector duty %. It would cause you to lose fuel pressure and affect AFRs without changing inj. duty.

Dave

 

OK.... First of all, I did WOT on the freeway and boosted .84 on the PFC right after the tune. The car has a new fuel filter. This morning I tried to turn the car on and it took a while before it fired, and it idled bad. It would stall unless i gassed it. I added fuel, and the car idled beautifully, but it still cuts fuel at around 3k rpm ONLY when i try to boost. My fuel pump is making a loud noise now alos, which it never did. I took it back out and it looks fine.

I have no idea what could be wrong.... Fuel pulsation dampener? regulator?

----BTW my tuner tuned it at first for 12psi with 87injector duty, then i asked him to raise it to 13. He changed the map alittle and upped the fuel making the 11.0 AFR quickly. Eitherway, the problem im experiencing now is not happenin at a point when my injectors are maxed out. Its happening at low RPMS when i JUSt start to boost. ~30% duty.

 

my car buck'd really bad when i swaped in 2ndary injectors that are stuck closed.

very likely, something went wrong with ur injectors. Possibly went bad after the tune and few runs.

My car is tuned rich for 12psi and my stock injectors were really old + possibly clogged, and was still at 95% dutycycle... so i would really check the injectors.

like mentioned.. ur not getting enough fuel

 

its cutting only when i attemp to boost watever RPM. MY car has 40K on the chassis, so its doubtfull my injectors are gone. Im trying to find out if their are any other possibilities other than jumping to ripping of my IM and opening my injectors.

 

I had a wierd similar problem back when I was running 14psi on stock twins and 1300cc secondaries. Sometimes out of the blue on full throttle it would buck (like I hitting a wall)...my injector duty cycle would hit 100%, even though I was normally 80-85% at those boost levels. Never understood it, but I would start by swapping out the 850's with new ones... if you need help let me know, I live in Glendale. It takes me 10 minutes to get them out...

 

It's not that they're gone, it's that they could be clogged just a little bit. 13psi is not an unusual boost level to max out stock injectors.

Keep in mind too it doesn't matter how 'old' your injectors are - if you're hitting 100% they're not supplying enough fuel. If thinking about slightly dirty injectors makes you fret, consider that you could very shortly be wondering why your 40k old engine is toasted.

 

Well... i went over to Armen's today and checked out a couple of stuff.

He was getting 80-100 knock levels at 2k rpm (wtf), injector duty was around 30% which is normal... we took out the fuel pump..... and apparently the hose that connects the pump to pipe that goes up to the top of the pump holder fuel feed was not sealed properly. When the pump was pumping, it was probably leaking right back into the tank.

We got a new hose, clamps, and everything and test it out tomrow. I will try to take pics.

 

Thanks, ill let you know, and prob im gonna put in 1300cc secondary,(when i find some for cheap) so i could use a second hand.

If this fixing the fuel-pump dosent work, then ill check out the injectors and the fuel dampners/regulators. The one thing thats still confusing me is why does the car idle good with half a tank, than 1/4? but it still cuts out fuel under boost.

 

Armen did you finish up and put the pump in? or are we doing that tomrow?

 

i cut the piping to the fuel pump, bought fuel lines and clamped then on to the fuel pump, not using the stock design. The car idles 100% normal, drives 100% at low RPMs even when boosting. I tried to take it to 8k rpm WOT second gear and i THINK is cut out again around 6.5K rpm. Im too scared to do it again cause i dont want to blow my motor. Im gonna take the car back to the tuner and have them check it out with a Wideband just to be safe. Im not taking any chances.

 

Get bigger injectors for ***** sake....100% duty?!

 

Yes im looking for some used ones. Im actually gonna install them before i go to the tuner, so he can also tune it for the injectors really quick.

 

should i go for 850cc primaries, or 1300cc secondary.

I found 1000cc secondaries for real cheap. Is it worth buying that?

 

850 and 1300 is like single turbo territory...



Your secondaries are what are topping out.... this would be PERECT for your situation and price..

http://www.rx7store.net/product_p/secrailfd.htm

 

I had that problem but a vacum line slipped off my boost control solenoid.... I was overboosting to like 20 psi. Put the vacuum line back on and all was right with the world.

 

I fixed the prob. First, the fuel pump wasnt on tite enough. Second, 1300cc injectors fixed the 100% injector duty. The hesitation i was experiencing ontop was ignition break up i believe. Now all i need is another retune, and maybe a HKS twin power. Thanks everyone