Back Pressure on S14 SR20DET

[naz280z]

Hi Fellas,

I own a 240SX S13 with SR20DET from 96 Zenki S14 Blacktop.
Mods:
Stock Engine
Tomie manifold
Garret GT2860 Turbo
1000cc injectors
walbro 255 fuel pump
3" Exhaust
Blitz Intercooler
Blitz BOV
Link ECU Storm G4+

I was tuning my car over the weekend here in Dubai and unfortunately while my car was on the dyno i lost compression in cylinder 1 (Zero compression) due to too much back pressure (30 psi) according to the tuner.

The oil dip flew out of the engine bay twice spraying oil all over the place but second time it blew a cloud of white smoke with it then we stopped to check the compression in all cylinders and realized there was no compression in cylinder 1.

The car made 324WHP before losing cylinder 1. The tuner suggested to rebuild the engine possible piston ring failure and once the engine is rebuilt to use an oil catch can to help with the back pressure.

Anybody experience this crazy back pressure on their builds?

[gaz_moose]

if its 3" all they way through and you don't have a bung in the tail pipe then I doubt you have massive backpressure.

blowing the dipstick out points towards excessive crank pressure which would be blocked breather pipes or piston ring blow by. you probably had piston ring failure.

[KAT-PWR]

Unless you had the crank case completely blocked off I doubt that was the issue. Sounds like a ring issue.

[EarlsWorld]

if its the stock motor pushing around 330whp then my guess would be just fried your rings. you should run a water/meth kit if you want to rebuild it with stock internals again.

[naz280z]

Pulled the motor out last night and it turns out piston one had a chunk missing from it causing zero compression.
The tuner is saying injector one stopped working for sometime during the tune due to some fuel delivery issue... he believes it's not the tune that blew the piston because the rest of the pistons are okay.

The injectors are brand new Five-O 1000cc came with flow test sheet.

Is it possible that a bad ring causing insane back pressure and injector one failing at the precious time to damage the piston.

[hanzbrady]

Please stop using the term back pressure since it has absolutely nothing to do with your issue. 1 of 2 things happened here.

1) Your tuner blew your shit apart
2) You bought cheap parts

Anything thing else in between is pure bs and more than likely your tuner backpedaling and grabbing at theories to keep himself from buying you an engine.

And just to clarify, back pressure simply robs a percentage of power, it is a flow restriction. To say that you had enough positive pressure in your exhaust system to literally blow a piston apart is insane. If this was the case the car would have made NO power on the dyno.

[brndck]

I think he means blowby, not backpressure.
not sure if this is a language barrier, or what.

[RalliartRsX]

Please stop using the term back pressure since it has absolutely nothing to do with your issue. 1 of 2 things happened here.

1) Your tuner blew your shit apart

Anything thing else in between is pure bs and more than likely your tuner backpedaling and grabbing at theories to keep himself from buying you an engine.

And just to clarify, back pressure simply robs a percentage of power, it is a flow restriction. To say that you had enough positive pressure in your exhaust system to literally blow a piston apart is insane. If this was the case the car would have made NO power on the dyno.


This.........ALL of this!! And especially what it is bold above.

A failed injector would be very evident during a dyno of all places. That is one of the benefits of the dyno: Seeing real time data and being able to terminate the run as he/she sees fit.

If the injector failed at some point during the run, you would know almost immediately. Not only would the live data show it, the car itself would change both in terms of sounds and operation immediately. That and the dipstick popping out is a very clear sign of excessive crank case pressure.

I think your tuner blew your shit to high heavens........

Any data log of the run?? If he is not willing to show you any data, then that would be an immediate red flag

[KAT-PWR]

To be fair aren't Five-0 Chinese redrilled injectors?

[RalliartRsX]

To be fair aren't Five-0 Chinese redrilled injectors?

If they are sidefeed, yes. If they are top feed, they do like everyone that currently makes topfeed; use a Bosch base top feed and modify as they see fit. Only ID has a propriety design that they developed in collaboration with Bosch. Everyone else uses the same Bosch unit and modifies the ball/tip/etc

However, the dipstick blew out TWIC during the dyno session. It seems the when it initially happened, it was seemingly dismissed (not enough information to discern when it occurred or if they had several runs after it blew out so they just dismissed it) and the dyno session continued. That should have been a tell tale sign right off the bat. And as mentioned, if an injector fails or is failing, a fairly experienced tuner (or even to the most novice person), the vehicle (or in this case, the engine) itself would behave significantly different once an injector is failing or has failed. There are several tell tale signs (be it AF, sound, how quickly the vehicle sweeps through it's rev rev range, etc etc in addition to the blowing of the dipstick) that would be sure fire warning signs.

Maybe I am far off on this as I do not run a dyno, but when I do quick street pulls for tunes, there is so much information being generated by the vehicle, a lot of these issues will be very evident as you do a pull. Even a change of 1 point in AF as you sweet through the range can cause a sudden drop in acceleration very briefly that feels like a misfire for instance. Then you can corroborate this with the data stream from the ECU. There are just lots of warning signs that need not be ignored that may have been during his dyno.

[RalliartRsX]

BTW, how is the tuner measuring backpressure?? 30PSI means the turbo RPM would be strospheric to register to measure any sort of pressure at the inlet manifold........

Language barrier or not, that gave me a big ol :D

[Blk96t]

Back pressure/ blow-by was created in your motor when the dip stick initially popped out. That was a symptom of the piston initially cracking. Continuing to tune after the dipstick popped/piston crack is what melted the piston or broke it.
Put simple the boost was escaping where ever it could... Hence the dip stick popping out. Also I would bet it started filling your catch can with oil rapidly. If you have one. Your tuner should have known what happened when the dip stick flew out shooting oil everywhere. Common sense really.

Ive fried 2 motors.

[ChinkyChris]

Post up pics of the engine... I would like to see if it was a lean condition/detonation/hard part failure. Also, if you can please put up screen shots of your timing/fuel maps. Sorry your engine failed buddy.

[wurley]

^I agree with the two above me: bad tune>piston failure>blow-by

not sure what its like in Dubai, but in my area there are places that can flow test and service injectors for pretty cheap.. if possible, its probably worth it to take the injector somewhere that can flow test, just to be sure the tuner is full of shit

[Kingtal0n]

1. Too much timing ("tuner" may have used 15* of timing with 93 octane) or too lean and you lose a piston, tuning error, or it could be bad gas, or a boost leak, couple possible causes. Did you pressure test the plumbing to 15psi first? A boost leak will cause IAT to spike and together with poor fuel quality(93 octane) may damage a piston, for example.

2. it is fairly normal and acceptable to have exhast gas pressure pre-turbine equal or greater than boost pressure on high power T-25 applications, however without a gauge to monitor how can anybody know how much exhaust gas pressure exists?

3. For 350~rwhp we use 550cc injectors when using 93 octane. If you are using E85 I can understand the 1000CC and if so, it is much harder to damage an engine with poor tuning, which makes me think boost leak as the culprit more likely.

[naz280z]

I think he means blowby, not backpressure.
not sure if this is a language barrier, or what.

I'm from new zealand asshole what language barrier are you talking about.

[naz280z]

To be fair aren't Five-0 Chinese redrilled injectors?

I bought them from Enjuku racing. Five-0 injectors are made in japan by JECS and they test individual injectors before they send them out and they provide a copy of the flow testing sheet.

[naz280z]

BTW, how is the tuner measuring backpressure?? 30PSI means the turbo RPM would be strospheric to register to measure any sort of pressure at the inlet manifold........

Language barrier or not, that gave me a big ol :D

He showed me a graph from the log just before the piston blew there was a huge spike

[naz280z]

Post up pics of the engine... I would like to see if it was a lean condition/detonation/hard part failure. Also, if you can please put up screen shots of your timing/fuel maps. Sorry your engine failed buddy.

https://ibb.co/juNGMF

[naz280z]

1. Too much timing ("tuner" may have used 15* of timing with 93 octane) or too lean and you lose a piston, tuning error, or it could be bad gas, or a boost leak, couple possible causes. Did you pressure test the plumbing to 15psi first? A boost leak will cause IAT to spike and together with poor fuel quality(93 octane) may damage a piston, for example.

2. it is fairly normal and acceptable to have exhast gas pressure pre-turbine equal or greater than boost pressure on high power T-25 applications, however without a gauge to monitor how can anybody know how much exhaust gas pressure exists?

3. For 350~rwhp we use 550cc injectors when using 93 octane. If you are using E85 I can understand the 1000CC and if so, it is much harder to damage an engine with poor tuning, which makes me think boost leak as the culprit more likely.

1. The tuner used 12* timing with 98 octane
2. He was monitoring it thru his pc
3. I'm not sure what caused it but his first guess was piston rings due to the blowby then he continued to tune it and blew my shit.

On top of that he believes that injector one is faulty or something in the fuel delivery went wrong and could of caused it to run lean...
i'm going to get it the injectors flow checked this weekend to rule them out.

[brndck]

I'm from new zealand asshole what language barrier are you talking about.

Your location says DUBAI dickhead. I was trying to give you the benefit of the doubt and hope you could tell that blowing the oil dipstick out is a known symptom of too much crank case pressure, aka BLOW BY.

Unless you have a melted cat, how the Fuck would you have excessive backpressure?

[KAT-PWR]

I bought them from Enjuku racing. Five-0 injectors are made in japan by JECS and they test individual injectors before they send them out and they provide a copy of the flow testing sheet.


On top of that he believes that injector one is faulty or something in the fuel delivery went wrong and could of caused it to run lean...
i'm going to get it the injectors flow checked this weekend to rule them out.

hmmm.......

[naz280z]

Your location says DUBAI dickhead. I was trying to give you the benefit of the doubt and hope you could tell that blowing the oil dipstick out is a known symptom of too much crank case pressure, aka BLOW BY.

Unless you have a melted cat, how the Fuck would you have excessive backpressjre?

My exhaust is fine i think it was bad piston ring and it escalated to melting the piston

[rawgarage]

Well I guess you listen to all this advice and do ya own conclusion....I'd be knocking on that tuners door...

[RalliartRsX]

naz280z There are a few things that need addressing here

1) There are no "true" sidefeed injectors that are larger than the 550cc that the prior generation STI comes with. They are all modified 370 or 550 base injectors regardless of who the base injector manufacturer is (which in this case is JECS). So, that means either redrilling or recapping, at which point you lose some of the spray patter characteristics as well as losing several other key elements of the base injector. NOT saying they don't work however, this is more a FYI. So just because they are flow characterized, doesn't really mean squat without latency values, etc.

2) The simple fact that you folks had the dipstick blow out and continued to tune shows negligence on both your part and the tuner.

3) As you mentioned, he proceeded to continue to tune and ignore the blow by issue..........Negligence

4) Most boost leaks are fairly insignificant and will only cause a 0.1-0.3 or so lean spike on the AF meter, but nothing on the order of several points on the AF. If we are looking at a swing of <+1 in the AF, the leak is very massive and the car would have severe operational issues. At which point that reverts back to negligence if this was not addressed.

Now, let me ask a question: what if the injectors do come back as in proper working order, what then?? The fact that you folks continued to tune with the dipstick blowing out, I really do not have much in the way of sympathy or remorse.

As the saying goes: play stupid games, win stupid prizes.

Goodluck either way. Go find a new long block and a new tuner.

[naz280z]

naz280z There are a few things that need addressing here

1) There are no "true" sidefeed injectors that are larger than the 550cc that the prior generation STI comes with. They are all modified 370 or 550 base injectors regardless of who the base injector manufacturer is (which in this case is JECS). So, that means either redrilling or recapping, at which point you lose some of the spray patter characteristics as well as losing several other key elements of the base injector. NOT saying they don't work however, this is more a FYI. So just because they are flow characterized, doesn't really mean squat without latency values, etc.

2) The simple fact that you folks had the dipstick blow out and continued to tune shows negligence on both your part and the tuner.

3) As you mentioned, he proceeded to continue to tune and ignore the blow by issue..........Negligence

4) Most boost leaks are fairly insignificant and will only cause a 0.1-0.3 or so lean spike on the AF meter, but nothing on the order of several points on the AF. If we are looking at a swing of <+1 in the AF, the leak is very massive and the car would have severe operational issues. At which point that reverts back to negligence if this was not addressed.

Now, let me ask a question: what if the injectors do come back as in proper working order, what then?? The fact that you folks continued to tune with the dipstick blowing out, I really do not have much in the way of sympathy or remorse.

As the saying goes: play stupid games, win stupid prizes.

Goodluck either way. Go find a new long block and a new tuner.

I appreciate you comment RalliartRsX.
I was recommended to get my car tune at this garage and the tuner is some filipino guy who's well known back home. Now whether he deliberately fucked my shit up or not i wouldn't know.

Yes, the fact that he continued on tuning after the dipstick incident clearly indicates his not the best tuner. I'm not here looking for sympathy or remorse buddy i just wanted to see what other folks experienced and come to a conclusion.

Yes, its unfortunate that he blew a piston but now at least my engines out and it's time to rebuild.

[RalliartRsX]

Luckily, these engines are very very simple to dismantle and build. Apart from the machining aspect and needing a torque plate, rebuilding one of these can be done by my 5 year old nephew. And with the wealth of information on building one of these and a FSM for tolerances, you can have one built over the course of a lazy weekend taking your time.

Goodluck. Go build your own. It's worth the knowledge base to spend a few extra dollars and peace of mind :)

[5280VertDET]

https://ibb.co/juNGMF

https://image.ibb.co/iGnSTv/IMG_20170228_WA0000.jpg

[RalliartRsX]

I want to make a correction: I am not sure which batch the NISMO 740cc injectors come from or how they are made. But I am pretty sure that is the limit of legitimate side feed injector size for a "standard" injector

[hanzbrady]

Wow that got hot. That's 100% detonation due to shit tuning, take all the pistons out and look and look around the top edges if you also see it there throw one or all four pistons through your tuners windows.

[naz280z]

Turns out these JECS Injectors are rubbish. Brand new with 3 years warranty and only a few runs on the dyno closed shut during the tune eventually melting the piston.

Thanks for your help guys I'm going to rebuild the engine and this time going with set of nismo Injectors..no more cheap shit

[Kingtal0n]

it sounds like a boost leak, Ive seen this before. the backpressure spiked because the boost leak became excessive, so the compressor had to work harder to make up for the leak, thus the backpressure spike if you are measuring it. This couples to an IAT increase because now the compressor is off its map, and that is what melted the piston and blew it apart. I've seen it in LSx engines fwiw.

12* at 98 octane sounds reasonable for an IAT of 100*F~ at sea level
if you are measuring the IAT it probably reaches 150*F+ at the time of failure when the compressor went off the map.

The A/F should have been around 12:1 for anything under 17psi of boost, and 11.8~ for 17-19psi of boost.

[feito]

Is it me, or are MOST tuners dicks who dont give a fuck about your shit unless you're spending thousands of dollars on labor? You know, "fuck this guy who is bringing his car in for a tune that will only take a couple of hours. Lets focus on these other cars that they brought in and leave here for days/weeks and we can charge whatever the fuck we want".

[naz280z]

Is it me, or are MOST tuners dicks who dont give a fuck about your shit unless you're spending thousands of dollars on labor? You know, "fuck this guy who is bringing his car in for a tune that will only take a couple of hours. Lets focus on these other cars that they brought in and leave here for days/weeks and we can charge whatever the fuck we want".

Yeah especially here in Dubai it's so common either they're useless cunts and dont know anything about tuning or they're big shots and charge an arm and a leg 1500USD Minimum

[gaz_moose]

shit, I need to set up shop in Dubai.