Rb25 falling on it's face

[wakotow]

Last weekend I installed an HX35 on my S1 rb25, I'm using the stock rb25 actuator so in theory I could hold it down to 7 pounds, but why bother upgrading (besides the holset doesn't want to run that low)? So now it's set to around 15psi, I have everything hooked up and running(more or less). My problem is after I hit about 12-15 pounds, car falls on it's face but I start spooling like mad (I get scared and let off the gas once it hits 20), although if I keep boost under 12 with the throttle then it does great and pulls ok for 45-55% throttle. First thing I checked was a boost leak, I have it pressure tested at least to 15 pounds (didn't have a very accurate gauge available). Air/Fuel is mid 11's, plugs are bcpres-11(or whatever the letters are) gapped first to .031, but I was breaking up, so now they are at .025, not breaking but still no good.

I'm running stock ecu w/ a safc2, not by any means ideal, but it handles my z32 MAF and my bigger injectors, hopefully I can save enough this winter...we'll see. Walboro 255, stock (ka24de) fuel filter.

So I'm not sure what to check next, my dad's car did a similar thing w/ high boost and nitrous (turned out to be a worn out fuel pump) so I was thinking either fuel or maybe the ecu, but I'm not sure.

[wakotow]

Well noone was interested last time, maybe I can get help now.

My coils were arcing out, so I've siliconed them and I'm not leaking spark anymore, I've changed my plugs to 7's gapped to .030, I checked ground on my ignitor, I have another from a J30 but I can't find it at the moment.

I've checked my IC piping, it held 15 psi for a couple minutes (my tester leaked, everything else was fine).

So I think I've eliminated air, and maybe spark, so I'm left with fuel and timing.

If my injectors were too small (they're supposed to be 550's but I suppose I could be wrong) I'd be running lean right? And I'm not so I doubt it's them. My walboro could be giving up, I've never heard of it happening but I'm sure it's possible. But once again, I seem to have a fine air/fuel mix.

I think I read somewhere that there is a boost control sensor that pulls timing if it reads 15psi, if so then that would be my problem, my ecu pin out has a pin for a boost control solenoid but I was under the impression that was for the factory wastegate controller. So if that does in fact exist, how do I get around it?

[240z4u]

Boost control solenoid has nothing to do with it.

That much boost from an HX may be maxing out your maf/stock injectors.

I wonder if the motor is pulling timing due to knock honestly.

[bmadd2402]

do the afr's stay in the 11's when you start breaking up? are they consistent thru the rpm range? there has to be a change when it breaks up. is the wastegate actuator is malfunctioning? does the rod have sufficient clearance to fully open? rig something up the way you made the boost leak tester and apply boost to your wastegate to ensure it is opening all the way.

The timing function of the ECU sounds like Rich and Retard. The stock ECU senses too much airflow thru the MAF, and pulls timing and dumps fuel. But since the safc2 intercepts the Maf signal, it shouldn't be an issue.

keep posting and checking. This forum takes some time for the right people to see your post.

[silviasgp06]

safc not ideal but...

I am also curious on what your afr is when it starts to break up.

something to think about:

edit:- The stock ecu (if i recall) is set for stock turbo airflow. Anything over that airflow(such as that coming from the LARGER hx35 turbo) the ecu thinks its overboosting and Rich&Retard takes effect to "try to save the motor" (even though we all know the rb can take higher boost air flows). R&R is the number one reason people wind up switching to a standalone ecu management system on the RB25. (also because there is no easy way to tune the stock ecu to get rid of it)

[S14-NEO]

i know its a pain in the a** but just as a test, get another set of plugs and gap them to .020 and give that a try...its a good possibility that the coild could be weak...with a bigger turbo its pushing alot more are so it coul dbe blowing the spark out under boost...i had the exact same issue with mine...i ended up going with a set of splitfire coilpacks and my issue was solved...before i did that i had my stock coils in there and my plugs were gapped to like .016 and i still had that same type of issue until i changed out my coils.once i put the better coils in there i was able to open my gap on my plugs to the stock or close to stock gap..

[wakotow]

Here's my story with plugs.

First I had 6's gapped at .032, I was definately blowing that out soSecond 6's gapped at .025Third 7's gapped to .020 (but some were gapped as low as .014)Now I have the same 7's gapped to .030

I suppose I could get another set of 7's and try them all at .020 again making sure that they are all correct, but right now it runs just about the same as before when I had the 7's gapped at .020-.014

I have also read that the power for that coil harness should be run directly to the battery so it has good power all the time, I haven't checked that I'll have to dig around and see where it pops out so I can hook it up correctly.

If my coils are shot I think I'll switch to lsx series coils, they're cheaper and should work well.

[DrifterProdigy85]

Are you getting a miss or does it feel like the engine just doesnt want to make power? Mine is having an issue were it doesnt miss at all but something is holding it back from making power at high loads. We could have the same problem here. I have new coilpacks and new plugs gapped at .030" so thats ruled out too. Only thing i havnt tried is a different MAF or Ignitor yet. Not trying to thread jack, just trying to help ya out with what ive come up with as well.

[wakotow]

For those of you interested in my air/fuel when the problem is happening. at WOT I hold low 12's (I pulled a little fuel out like 2%) but when the problem happens I am aroun 11.7 or 11.5, so I do go rich by about a half percent, this doesn't seem like a boost leak to me, usually it goes nuts rich (at least in my experience) but power wise it feels like it.

mostly I don't feel a miss at all, today I thought I felt one, but it was right there at redline so it might have just been my shifting.

When I gun it, I'm fine all the way through 2nd gear (holds at about 15psi +/- 1) then third hits and gets up to about 15psi and it spools to 20ish but goes flat, not a miss or sputter just like power drain. It feels almost exactally like a boost leak except my air fuel doesn't go as nuts.

[DrifterProdigy85]

Thats how mine is as well. Definitly let me know if you figure this out. Only things i havnt tried yet is to replace the Ignitor and MAF. In a way i dont think its the ignitor because i would think that if it was it would be giving less spark and would create a miss for the cylinders which it doesnt have. And usually the MAF would make for some wierd AFRs but i dont have my wideband in yet to check.

[wakotow]

I guess I don't think it's MAF related only becuase I pull really hard through 1st and 2nd, just in 3rd and 4th when I build boost past 15psi.

Are you running on the stock turbo? what ecu are you running? have you checked for boost leak? Now that I think about it, I haven't checked my BOV for leaks.

[DrifterProdigy85]

I'm all stock. No boost leaks and bov doesn't leak. Has no issues holding boost at all in any gear. It's really wierd and annoying. I'm gonna put my wideband in tomorrow and see what it reads.

[bmadd2402]

hey, it sounds like it maybe sensing some knock and pulling timing/enriching mixture. sounds like two issues. the first is causing the second. First, you have some serious boost creep likely causing a condition you have not tuned for and the ECU doesn't like it, so it pulls timing. That .5ish AFR is pretty significant (esp if it is pulling timing too, that will make it feel powerless). Can the stock HX wastegate keep up with the Air flow? Those HX's are from turbo diesels right? I bet you fix the boost creep the other issue gets better too.

Best bet, Get to a dyno, or make friends with someone who has a Consult scanner. You need more data, ie Air flow, timing, etc.
Modified by bmadd2402 at 2:17 PM 9/11/2009

[wakotow]

I have a safc that'll log air flow, or at least percentage of air flow, the highest I've seen is like 52%, I have still to learn how to view the whole log, just peak, I'll look it up. It's not recording any knock, now I know the sensor is putting out some voltage so it's not completely dead, but it may be completely malfunctioning, I'll test it by tapping the block with a screwdriver later tonight, but then my question is, if the knock sensor is dead and doesn't respond to knock, then how would the ecu know it was knocking?

The holset wastegate is pretty stinking small (less than an inch in diameter) and the way the lever works is it stops after it is just cracked open, so it probably only gets about 30 degrees of actuation, so I doubt I'll be able to fix my creep without at least major porting of the hole and cutting back the part that it stops against...Otherwise I'll be shelling out a couple hundred to get a wastegate.

Oh if only there were dyno's here, the only one I know of is at the Porche dealership, and I'm not even positive you can pay to use it. My only hope is that the two shops in town that have just opened within the last 18 months or so get theirs up and running, apparentally they are in the process of installing/calibrating/struggling in the economy, so ya.

I may have found the problem, or at least something that wasn't helping. My fuel pressure at idle was 44psi, and without vacuum at 53or so psi, I must have thought I was looking at 43 instead of 53 when I got my afpr, now it's back to stock and I'll be driving it later this afternoon to see how it acts.

[Cjmartz2k]

Sounds like you just set the fuel pressure with vacuum on it, but I don't think that's you problem if you still have decent a/f's. The internal gate on the HX35 isn't going to be able to keep up BTW. You'll need to port the piss out of it at the very least. I know you've already stated you know the SAFC isn't the best idea to say the least, so I won't hammer on it, but I will point one thing out to you. The timing maps on the stock ecu are set up for a stock AFM with no correction. The SAFC lies to the ecu and tricks it into adding more or less gas by telling it to go to a different part of the map. It'll change fuel to a point, sure, but it's changing timing along with that, and you don't know what it's changing it too. Might be your problem, might not. If you want to cheap ecu, just do the chipped VG30 ecu. I don't know if any of that helped, but it's a couple of things to think about.

[wakotow]

What're you using for a wastegate on your HX40? Will a 38mm work for me, or would I be better off getting a 44mm?

actually I emailed nistune today to ask about using an automatic ecu out of a J30 to see if that'll still work for me (I couldn't find any real answer to that question on here) so maybe in the next week or three I'll have a new ecu
Modified by wakotow at 5:17 PM 9/11/2009

[Cjmartz2k]

twin 50mm's

[scottymizt]

im having the same issues with my rb25 ecu and when i look at the consult program i have it tells me i have a knock sensor thats bad. I checked both sensors voltages and they were about 2.57volts when they are unhooked the line reads about 4.5 volts. According to my fsm it say they should be at 4 volts so i am not sure if the three sensors i have are all bad or i have an issue with the ecu. Im only boosting 9psi on a t3/t4e ebay turbo and when it does run right it hauls but it seems that the longer its running the more the knock sensor code comes up. I can clear the code and it will come right back, bout ready to put in my megasquirt2

[wakotow]

Well now I feel like an idiot, but, I decided to check my timing again (I'd been procrastinating, it's been a months since I last checked it)...it was a little off, about 7 degrees retarded. Silly me didn't tighten down all three bolts very well one was finger tight, so I'm off to stomp on it and hope I solved it.

One other thing, I'm not sure that I have larger injectors, what I have right now is grey, are those stock? Once again I can't find that info or pictures anywhere.

[wakotow]

Well, I took it for a spin last night, It pulled harder up untill about 5800 and then I completely lost spark, after three pulls, and having it do the same exact thing every time, I decided to regap my plugs to .022 and see how that works, so as I was changing my plugs I checked my power supply to the coil harness, and guess what I found, no ground wire at all. It's snipped off at the connector, the ignitor is grounded, but not the coil harness. So I'll be checking all that wiring as soon as I get home this afternoon, and putting in a new wire from power to the battery to make sure I have a good 12 volts at all times. after all that, I have to assume my spark is good unless the coils themselves are shot.

[DrifterProdigy85]

Well i found my issue i think. Was running at a 13.0 AFR at WOT. This would definitly cause the ecu to pull timing giving me my loss of power. I increased fuel pressure to 50psi and is now at 11.5 AFR. I wonder if something is clogged like the fuel filter or injectors.