SR20DET falls on its face @ 5.5K rpms

[StryfeS13]

I've been working on my friends SR20 and I can't figure out why it's doing this. It's almost like it hits fuel cut, or a rev limiter, and just completely stops building boost, accelerating, etc.

There are no boost leaks, AFR's are good, etc.

His set up is:

S15 T28 Turbo at stock boost
Apex'i AVCR
Sard 550cc injectors
Z32 MAF

I have checked timing,ignition timing, i've tried turning the AVCR to "off," I've checked plug gaps, etc. I've tried all I can think of.

Also tried to completely remove the AVCR from the picture, by unplugging it, and routing the wastegate straight to the hotpipe, instead of the boost controller. Same issue.

Any thoughts?

[sebastianwrx]

.............

[Sileighty_85]

What are the plugs gapped to?

[thizzen4]

CHECK UR TPS SENSOR next to throttle body might have a dead spot in it holddd it all the way down with a screw driver and have some one rev and see if its thatt

[sebastianwrx]

What are the plugs gapped to?

0.28 and tps was fine we checked

[bc.]

fuel pump checked yet?

edit: what is the fuel pump?

[sebastianwrx]

fuel pump checked yet?

edit: what is the fuel pump?

walbro 255

[chininsan]

do you have the stock rubber intake piping?
check that. sometimes the spring inside of it screws up.

[codyace]

boost leak

[StryfeS13]

do you have the stock rubber intake piping?
check that. sometimes the spring inside of it screws up.

Yes, it has stock rubber intake piping.

How can the spring cause it to do this?

boost leak

We've checked all couplers, even made a boost leak tester...there is no boost leak. However, the Greddy RS bov has a little hole on the back of it (factory), and it leaks during the boost leak test, why is this?

[sebastianwrx]

hi just checked my buddy car and lil update when the car was cold it goes the boost no problems and no fuel cut ...so what could be it ?..bad fuel pump or coil?

[codyace]

We've checked all couplers, even made a boost leak tester...there is no boost leak. However, the Greddy RS bov has a little hole on the back of it (factory), and it leaks during the boost leak test, why is this?


That part is ok, it's just a little vent to aide in the operation of the blow off valve -- it leaking doesn't effect how the car runs.


WHen this condition occurs, can you go WOT and the car continues to run, albiet off the 'limiter' sort to speak.

[NismoR003]

what do you mean it stops building boost?
does it maintain boost or it falls back to 0?

can you be more specific?

[StryfeS13]

That part is ok, it's just a little vent to aide in the operation of the blow off valve -- it leaking doesn't effect how the car runs.


WHen this condition occurs, can you go WOT and the car continues to run, albiet off the 'limiter' sort to speak.

Oh, alright.

When it happens, yes the car continues to run, it doesnt turn off or sputter or anything. It just hits a wall. When the car is cold, it does not do this. I'm thinking maybe fuel pump....or coil harness?

what do you mean it stops building boost?
does it maintain boost or it falls back to 0?

can you be more specific?

The car hits a wall and does nothing...that's as specific as it can be explained haha.

[codyace]

To check the coil pack harness you could check resistance and readings via Multimeter and FSM, I'd do that as if it checks out you can rule that out.

Member Jspaeth on here had an issue like this and his ultimately was solved by back probing the ECU pins and making sure they were making contact. I had a similar issue to this and it was a loose coupler, that had escaped my initial inspection of all couplers.

Aside from that, use the FSM to troubleshoot your main sensors....TPS, CAS, CTS, MAF and O2. It doesn't take long to check signal wire integrity.

[JDMRIDDAZ]

u should rewire ur fuel pump
with heavy duty wire and relay
definatly check ohms on coils
also check the two plugs that power engine harness
to see if all wires r getting full 12v...
also is the engine like gurgling at 5.5 k ?
or cutting off?
also do u have a tuned ecu ?
if so try a stock one and see wat happens

[Sil-Eighty SE-K]

i say pump.... throw in a gauge and see hwat it reads at WOT when it happens

[sebastianwrx]

Coil harness checked theyre reading 12.5 in all 4...

[sebastianwrx]

u should rewire ur fuel pump
with heavy duty wire and relay
definatly check ohms on coils
also check the two plugs that power engine harness
to see if all wires r getting full 12v...
also is the engine like gurgling at 5.5 k ?
or cutting off?
also do u have a tuned ecu ?
if so try a stock one and see wat happens

hi i was at my buddy car earlier and checked the ohm in coil harness,tps,injectors,...tps was fine ,injectors at .14, coil harness all of them are 12.5 and when u go half throttle it goes fine and pass without fuel cut except when its full throttle than it gets fuel cut exactly at 5000 sometime 5200..could it be fuel pump getting bad?

[codyace]

I knwo plug gaps were checked, but what are they set at?

[sebastianwrx]

They were gap at .28

[JDMRIDDAZ]

also i meant the ohms on the coil packs not just the 12v source they have to be 1k ohms
put a stock ecu on it and see if it happens again

[codyace]

I knwo plug gaps were checked, but what are they set at?

Try gapping them down to .022 and see if that fixes it up. It may be spark blow out. With the age of these components getting older and olrder, it's hard to say how capable a 20 year coil pack is anymore.

[KendallH]

I'd bet 5 dollhair its the knock sensor

[codyace]

I'd bet 5 dollhair its the knock sensor

Knock sensor shouldn't even be working at that point, it's sub 4000 IIRC

[StryfeS13]

Alright guys.

- I checked ECU codes, there is no knock sensor code. I built the motor and the knock sensor is good, and the wiring to the knock sensor is good.

- Today I gapped the plugs from .028 to .025, and it's the same deal.

- I tried retarding and advancing the timing, like 20 different times. Was never any better or worse, it made no difference.

- I swapped my walbro fp into it, which I know is good because it powered my KA-T just fine, problem still persists.


At this point, I'm thinking it may possibly be the coil packs themselves being bad?

Kinda lost.

[codyace]

Is there anyway you can get a video of it when it happens?

[StryfeS13]

Yeah I can try next time I see the car.

[91s13shawn]

My car is having the same exact problem! it cuts out/ hits a wall at 5000ish but when the car is cold it runs great. Please let me know if you find what the problem is i have been stumped for months.

[StryfeS13]

Do you have an AVCR, Shawn?

I hope you say no, so I can rule that out as a problem lol.

[JDMRIDDAZ]

ur over looking something simple...i can feel it

[fullthrottle]

Try a different maf. I know it says you have a z32 but you seem to have gone through every other suggestion I had. Timing was my first answer and then fuel pump. So if it's not the maf it could be that the Ecu was tuned for a rev limiter at that rpm.

[Silverbullet]

I suffered from a similar issue a while back. Where the cut off seemed consistant to the RPM, but I noticed it was load dependant. The cut off point would be lower in a higher gear, amd the amount of throttle affected it also. For instance, at WOT in 2nd gear it may cut off at 6k rpm, and 3rd gear, it may cut out at 4.5k rpm, but at partial it may not cut out at all. Is yours like this also?

[StryfeS13]

Yes mine is similar to that. If I go half throttle, it will not do it. Sometimes it cuts at 5, sometimes at 5.5, sometimes at 6. Etc.

[Kyle W.]

Check your tps. I had the same thing happen to me.

[GSXRJJordan]

boost leak

My first thought too.

- I tried retarding and advancing the timing, like 20 different times. Was never any better or worse, it made no difference.

This worries me. Check/set the base timing per the FSM. This was my second thought.

Yes mine is similar to that. If I go half throttle, it will not do it. Sometimes it cuts at 5, sometimes at 5.5, sometimes at 6. Etc

If it's not rev-dependent (it'll rev to redline with less load) then it's load-dependent, and that makes me think fuel or MAF. If it were more or less rev-dependent, I'd think more about timing/CAS/wiring.

What engine management is he using? SAFC or ROM tune?

[StryfeS13]

Hey Jordan, thanks for stepping in.

- We checked for boost leaks, there are none.

- I set the timing back to FSM spec. It's at 15 BTDC @ 850 rpms.

- That is also what I was thinking. Because I can accelerate at 80 - 90% throttle and it wont do it. But the second i go WOT, it'll do it. The more boost I give it, the earlier it cuts. (for example, 14 PSI cuts at 4.5K) When it cuts, the AFR's don't go all crazy or anything, so I don't think it's fuel...

Maybe it is the MAF.

[GSXRJJordan]

Load dependent and not going lean = MAF or engine management. You never mentioned what you're using to tune it? I know you're not trying this all on a stock SR ECU...

[StryfeS13]

Yeah, definitely not stock ECU. It's an EFI Specialist ROM tune. We've talked to Khiem, he said it's all good.

[jr_ss]

Have good grounds on the chassis/motor/etc? Sounds more like electrical inference causing the issue... I dunno just thinking out loud here...

[StryfeS13]

Yeah we have good grounds. I'll check them just in case whenever the car is here again though. Probably tomorrow.

Still haven't tried a new maf yet either.

[StryfeS13]

Tried a different MAF. Nothing.

[GSXRJJordan]

Grounds are a great thing to start, but they tend to be more rev-dependent than load-dependent symptoms.

I'd start logging actual data, starting with MAF voltage. I'm guessing you're either max'n the MAF voltage or something's not getting enough power (voltage drop on an important component). Also what were your actual TPS readings at close/WOT, referenced to the TPS sensor ground?

[fullthrottle]

Is it possible that the injectors aren't the size you thought they were and are actually flooding the cylinders at full boost? Did you buy them new or used? It would suck to have to get the flow test but if they are say 740cc instead of 550s or whatever you have it might not be flooding until a certain boost/load. Exhaust smell like fuel at all? Do you have a wideband?

Edit. Just saw that you said your a/f ratio is good.

[fullthrottle]

Squeeze the intake and see if it's soft. It could be collapsing when the turbo starts to pull hard. Make sure the metal coil inside of it is spread out evenly through the whole intake pipe. If that's good double and triple check your couplers for cuts. Like around where it goes through the body of the car. Turbos build boost a lot faster than a compressor and can expand the couplers causing leaks that aren't apparent when testing for a boost leak. What psi did you bring the system to when doing your boost leak test? Make sure you test it at a lot higher psi than you plan to run. I test at 25psi to run 16psi.

[Sileighty_85]

What brand plugs and Heat Range are you running?

[StryfeS13]

Grounds are a great thing to start, but they tend to be more rev-dependent than load-dependent symptoms.

I'd start logging actual data, starting with MAF voltage. I'm guessing you're either max'n the MAF voltage or something's not getting enough power (voltage drop on an important component). Also what were your actual TPS readings at close/WOT, referenced to the TPS sensor ground?

The TPS voltage was .045 at closed, and like 4 something at WOT.

Squeeze the intake and see if it's soft. It could be collapsing when the turbo starts to pull hard. Make sure the metal coil inside of it is spread out evenly through the whole intake pipe. If that's good double and triple check your couplers for cuts. Like around where it goes through the body of the car. Turbos build boost a lot faster than a compressor and can expand the couplers causing leaks that aren't apparent when testing for a boost leak. What psi did you bring the system to when doing your boost leak test? Make sure you test it at a lot higher psi than you plan to run. I test at 25psi to run 16psi.

I'll try that today.
I tested it at around 20 PSI. I'm sure the car will never see more than 16 lbs.

What brand plugs and Heat Range are you running?

NGK BKR7EIX gapped at .025. Have also tried .028, .022, .030, .032

I'm trying to convince him to switch to copper plugs.

[codyace]

NGK BKR7EIX gapped at .025. Have also tried .028, .022, .030, .032

I'm trying to convince him to switch to copper plugs.

Material isn't going to make any difference in this circumstance, just on the longevity of the plugs.

Do you have a way to log the values as you drive through the ECU or your consult port?

[StryfeS13]

No, unfortunately I don't..

[StryfeS13]

Figured it out....intake was collapsing.

Thanks for all the help dudes!

[ultimateirving]

Figured it out....intake was collapsing.

Thanks for all the help dudes!

haha, make note of that shit. hard to diagnose for sure! what did u upgrade to, post a pic plz. ima gonna be upping my boost soon and wanna make sure this dont happen to me. (E85 conversion in progress)

[codyace]

haha, make note of that shit. hard to diagnose for sure! what did u upgrade to, post a pic plz. ima gonna be upping my boost soon and wanna make sure this dont happen to me. (E85 conversion in progress)

Run a proper intkae tube and couplers

[StryfeS13]

The intake that was on the car actually had NO spring inside of it.

We got a new intake and all problems have been resolved.

[GSXRJJordan]

The intake that was on the car actually had NO spring inside of it.

We got a new intake and all problems have been resolved.

Fairly common problem, and I think it was brought up earlier in the thread! Glad you got it figured out :)

[codyace]

The intake that was on the car actually had NO spring inside of it.

We got a new intake and all problems have been resolved.

Yea those stock ones collapse so easily!

A friend of mine had an instance of his car actually sucking the plastic cone inside the intake filter into the intake, essentially closing off the the intake...it would do some wacky stuff until he sorted it out.

[bc.]

Figured it out....intake was collapsing.

Thanks for all the help dudes!

Lol, what?

Can you take a picture of this happening and post it on here? It would bring this thread full-circle...

[codyace]

Lol, what?

Can you take a picture of this happening and post it on here? It would bring this thread full-circle...

Imagine the intake tube to the turbo sucking the rubber accordian junk (or crappy coupler) shut....

[91s13shawn]

no i dont have one

[Tearlessj]

I was just about to come in here and post that.

Funny story, I was a instructor at one of the events and everytime I drove this guys car it would do that. When he drove it didn't do it. We figured out it was his intake and I was flooring his car all the way and he wasnt. Go figure.

[fullthrottle]

What do I win for figuring it out?

[StryfeS13]

Here, have this:

http://2.bp.blogspot.com/_53oMB4-fxXM/SVZZdJntnPI/AAAAAAAAAAM/vXEtrdBFtqI/s1600-R/cookie.gif

[driftkid39]

I was having the same problem intake collapse and didnt know it thank you for zilvia 2 days and lots of parts changing BOOSTING NOW

[rbsidewayz]

i hope i fix my problem tmrw once i get bak to my garage thnks to this thread i,a b able to trouble shoot every idea possible...lets see how it goes ..