detonation issues standard RB25DET

[mikel]

detonation issues standard RB25DET

My R33 GTST has developed some detonation under high load, low power street driving conditions - eg driving up my steep street at 40kmph in 3rd gear - engine light comes on, hear the rattle, back off the throttle and/or drop back to 2nd to stop the detonation - I try to be mechanically sympathetic with the old girl.

The car went in to the tuner this morning to get it sorted and we discussed the detonation issue - on the dyno the detonation was able to be replicated, but it went on the dyno late in the day so she's having a sleepover to get it resolved.

I read this thread with great interest 

 

The car has only recently started to detonate under high load/lowish revs conditions - and when I hear it or see the engine light come on, I back off and/or change gear.

It's been daily driven on commuter runs for the last 12 months - almost no "spirited" driving to blow any carbon out. Not all stop/start traffic, some highway driving.

Obviously I'll take guidance from my tuner, just seeking some input from SAU on:

• possible reasons why an engine would start to develop detonation issues (I always use BP Ultimate and use about a tank per week) 
• sanity check what my tuner proposes - I've no idea yet - likely new plugs, which is fine, even though the current plugs have only done <10K km or so (Platinums)

ECU is an Apexi Power FC, turbo is HKS 25/30, engine is a standard RB25DET.

Definitely not looking to flame my tuner - I've been using them for a long time - I'm just trying to be better informed so I understand what my issues are and they're likely resolution.

cheers

Mike

[admS15]

Maybe just a batch of crap fuel. Have you refilled the tank since it started doing it?

[GTSBoy]

It'll be bad fuel (has happened to me), or if it has been from more than one tank from more than one servo, then it will be one of several usual causes.  The first possible you've already identified.  Carbon buildup in the chamber somewhere.  Needs a clean, either by running light load high speed carefully until it gets better (which could take a drive to Alice Springs!) or via water injection, which can be done on the dyno.  The other causes are oil contamination from blowby or from turbo seals, dud plugs, or maybe there has been other detonation in the past that has chipped a piston and caused a sharp edge.  Oh, or a dirty injector.

[mikel]

44 minutes ago, admS15 said:

Maybe just a batch of crap fuel. Have you refilled the tank since it started doing it?

it's been happening across multiple tanks of fuel - mostly the same servo, but not always - always BP 98

40 minutes ago, GTSBoy said:

 or via water injection, which can be done on the dyno. 

I'll ask my tuner if they can do this - thanks

40 minutes ago, GTSBoy said:

The other causes are oil contamination from blowby or from turbo seals, dud plugs, or maybe there has been other detonation in the past that has chipped a piston and caused a sharp edge.  Oh, or a dirty injector.

lots of possibilities of course   

injectors were serviced/cleaned late 2015 and plugs changed at the same time, new CAS - the car has done <15K km since then.

I'll see what the tuner says...

Thanks for your input guys - greatly appreciated.

cheers,

Mike

 

 

Edited August 15, 2017 by mikel

[mikel]

well all bad news from the tuner

they ran a compression test with number 4 way down (100)

compression numbers were 150, 135, 130, 100, 150, 150 - 2 and 3 down also

My tuner's recommendation is a rebuild or another 2nd hand motor...either is a significant cash investment

Discussing with others since, some other tests are warranted - eg a leak down test and inspection of the bores/combustion chambers to:

• clarify if the issue is head/valve related rather than bottom end (rings etc)
• assist to diagnose why the engine started detonating in the first place

Of note is that back in late 2014 the water pump failed and I cooked the head - long story short and it ended up with a NEO head on it and was re-tuned

Prior to the water pump failing in 2014, it made 235kW at 15PSI boost, and ran that reliably since I imported the car in 2006.

When the Neo head went on I had other issues with the boost controller and its been running around 10PSI boost since late 2015 and 200 RW kW. Compression across the cylinders was consistent - I don't remember what it was. Approx 15k km later I've got detonation issues, with 3 cylinders down on compression, one of which is way down.

Obviously if I start down a (best case) of head removal or (worst case) engine swap/rebuild I need to know and fix what caused the detonation in the first place..

The engine still runs fine (currently), and I'm nursing it around when I need a car - it feels no different from before it started detonating - I'm just very careful now to watch the engine light and keep an ear out for detonation.

• ECU is an Apexi Power FC
• Turbo is an HKS 25/30
• standard, but serviced/cleaned injectors

I keep wondering if that Neo head was a bad idea back in 2014 - but the detonation issue is recent.

Questions to you guys:

• other than carbon build up (unlikely after 15,000 km) and crap fuel (unlikely with numerous fresh tanks), what can cause ongoing detonation issues that just "start" to occur? ECU gone faulty? Injectors? faulty sensors?
• are there specific tests/diagnosis steps I should be asking my tuner to do before I start down the path of head off, or worse engine out?
• views on 2nd hand jap motors vs rebuild? You can go nuts on a rebuild of an RB25, but in my research so far a "standardish" rebuild with forged pistons, current rods/crank, new bearings/rings and a bore hone is "similar" in cost to a 2nd hand motor install - my power requirement is around 235 - 250 rwKW
• any recommendations for engine builders in Brisbane? Between my current tuner and a 2nd opinion from a different tuner today, the cost varied significantly. If I have to rebuild I'd like to ensure I get a good outcome - a reliable engine that could take say 300kW but makes 240-250 kW is fine. My HKS 25/30 turbo will be running out of puff at 240kW or so, and I'm still running standard injectors at the top end of their duty cycle at 235kW. 

 

cheers

Mike

Edited August 18, 2017 by mikel

[Dose Pipe Sutututu]

I can only assume you upped the compression with the NEO head and kept the same tune for the original head/motor combo.

NEO heads have much smaller combustion chamber volume and when used with stock R33 pistons you've efficiently upped the compression.

Throw in a stock motor, cheapest option for you since you're after such little power.

 

[GTSBoy]

Wot he ^ said.

Neo combustion chambers are about 85% the volume of the vanilla 25.  Even with a retune, your compression would have been much much higher.  Your safety margin for detonation would be much skinnier, if not altogether gone.  It might only take a little oil breathing to start it pinging.  It could and would ping at levels that you won't notice, and gradually eat itself.

Let this be an objective lesson.  Neo heads do NOT go on vanilla bottom ends.

[steventt]

Fuel pump, low voltage. Possible fuel pump.

[mikel]

Bloody NEO head,

20/20 hindsight etc...

So I have a dilemma

Existing tuner that I've been using for 10 years (they didn't put the NEO head on) recommends engine swap or rebuild:

• engine swap with a low km RB25 (approx 70,000km) sourced from Japan - > $5k parts and labour
• rebuild RB 25 with "good bits" ~ $10K parts and labour

2nd Opinion from another tuner, recommended by a colleague, but I have no direct experience

• engine swap ~ $1500 for motor, ~$2.5K labour, but no guarantee on the motor = $4K
• "basic" engine rebuild, forged pistons, re-use rods/crank/block, hone the bore, new bearings - $5k

I need to get rid of that NEO head if I rebuild,unless I went stupid and built for E85

12 minutes ago, steventt said:

Fuel pump, low voltage. Possible fuel pump.

possible issue - cheers

and if I went E85 a definite requirement...

Right now I have $0 to spend, but will need to find the minimum required  - In a choice between an "unknown" 2nd hand motor at $4K, and a basic engine rebuild at $5k - I'd lean towards the $5k "basc" rebuild option

cheers

Mike

 

 

 

[WMDC35]

If you're changing the pistons you could sort the compression and keep the neo head 

[mikel]

2 hours ago, WMDC35 said:

If you're changing the pistons you could sort the compression and keep the neo head 

that's good thinking

[Scott Black]

Rb25/30 neo

[Dose Pipe Sutututu]

NEO head and 3.0L is win. 

[AngryRB]

I would of thought the comp test would be higher?  My last r33 motor had up to 170 in comp without any issues 

+1 for RB30 bottom for $200 , is too easy?

Edited August 19, 2017 by AngryRB

[mikel]

2 hours ago, AngryRB said:

I would of thought the comp test would be higher?  My last r33 motor had up to 170 in comp without any issues 

+1 for RB30 bottom for $200 , is too easy?

what Dose Pipe and GTSBoy are saying is that the NEO head should never have gone onto a factory RB25 bottom end - especially a bottom end with 140K km on it.

That some cylinders are at 150 and not at 170 or so I can only assume is all whole bottom end has copped a flogging in the 15k km done since the NEO went on.

It's always been down on power since the NEO went on, and that's possibly as they pulled timing out of it (2 different workshops) as it must have always been on the brink of detonation, leaving me with a lunched motor 15000km later. - rather than saying the NEO head is a bad idea on an R33 RB25.

It is what it is - I just need to determine the best way forward - rebuild or swap in a 2nd hand RB25.

If I re-build do I keep the Neo head, or source an R33 RB25 head.

RB30 bottom end sounds interesting, but I'm sure it would be a lot more than $200 extra - crank and conrods would need changing surely? block also?  If I rebuilt I'd be trying to re-use my crank and conrods, and only replace pistons, bearings and rings - my HP requirements aren't high - a reliable 250kW is fine.

Mike

edit: had a quick look at the RB30 sticky - one can pipe dream, but not realistic at this point in time

 

Edited August 20, 2017 by mikel
clarification

[GTSBoy]

You have the block and you have the head.  If you're going to rebuild rather than swap in a bunky, then keep the Neo head.  It is the best head choice out there.  You will just need to get pistons to suit the head, which is doable.  Stockish rebuild, just buy stock type pistons.  If you're going to use forgies, then you MUST make sure that the people you're buying from know that it is a Neo with the small chambers, because others have been caught by piston suppliers not knowing the difference in the past.  Other than that, aftermarket pistons for Neo are just as easy.

Neos use RB26 rods which are better.  If you need rods then you could consider getting some, just because.  But if you need rods, then the other thought is simply to go aftermarket.  Money spent buying a set of neo/26 rods gets you at least part way to some tougher new rods anyway.

Neos have an N1 oil pump.  With ANY RB25 rebuild you should be looking at your oil pump and its drive anyway.  There is money to spend in there, but it would have to be the single most important bit of money you can spend.

Put in some ARP head studs, etc etc while building it.

All these things will affect that "budget" price of ~$5k you've been given.  It's kind of hard to get away with a build that you'll be happy with (ie one that you know you've done all the things you should do, not cut any corners, etc etc) for that much (little) money.

[Scott Black]

Compared to rebuilding a rb25 with aftermarket pistons properly and building a 25/30 there is prob around 1k differnece,
Both engines would need
Pistons
Crank measured and linished/grind
Tunnel checked and close and honed if needed,
Block honed or bore and hone if required
Block decked if required
Head serviced properly (check valves. Cams. Tappets, new seals)
New rings and bearings
New gasket kit
Check all clearances
Crank machined for crank collar,
New oil pump
Oil breather modifcations and oil restrictors,

And rb30 will require the purchase of an rb30 short motor
And welding the vct feed on the neo head and tapping the gallery then running an external feed for vct oil feed, its a couple of hundred for the block, a couple of hundred for welding and tapping the gallery and a couple of hundred in lines and fittings for the feed

Rebuilding a motor vs slapping something together cheap is a lot of money, yet you then dont end up with issues like huge comp destroying your motor from miss matched parts thrown together by a backyarder or Kmart mechanic.

Also needed to be considered if doing somethinf other than a factory build is the cost of tuning the car to suit and ecu if required.

If your on a budget the easyest safe option is a decent condition 2nd hand motor with warrenty.

[mikel]

On 8/20/2017 at 7:49 PM, Scott Black said:

If your on a budget the easyest safe option is a decent condition 2nd hand motor with warrenty.

Cheers Scott,

I agree, and am likely to head down this path.

Currently researching appropriate engine supplier and workshop to do the swap.

Any suggestions on reputable Brisbane companies people would recommend would be appreciated - but potentially could ship the motor from interstate if compression tests done prior yada yada and warrantied etc

I'd be interested in whether people think it still worthwhile doing a leak down test on my current motor for a couple of hundred $ to confirm it's not head/top end related..

Similar for a 2nd hand engine - if the compression test is OK, is a leakdown or other tests necessary?

cheers

Mike

[mikel]

On 8/20/2017 at 7:49 PM, Scott Black said:

Rebuilding a motor vs slapping something together cheap is a lot of money, yet you then dont end up with issues like huge comp destroying your motor from miss matched parts thrown together by a backyarder or Kmart mechanic.

agreed - with 20:20 hindsight, no decent mechanic/tuner would have "recommended" a NEO head on an R33 RB25 bottom end...and I should have sought advice from SAU before proceeding...

On 8/18/2017 at 11:20 PM, GTSBoy said:

Neo combustion chambers are about 85% the volume of the vanilla 25.  Even with a retune, your compression would have been much much higher.  Your safety margin for detonation would be much skinnier, if not altogether gone.  It might only take a little oil breathing to start it pinging.  It could and would ping at levels that you won't notice, and gradually eat itself.

Let this be an objective lesson.  Neo heads do NOT go on vanilla bottom ends.

Neither the shop that installed the head (and tuned on their dyno) or my normal tuner (who tuned afterwards on their dyno), highlighted the peril of a NEO head on an R33 RB25 - no reward for guessing I'm unlikely to go back to either...

...it is what it is, and I just need to sort the best option going forwards, and a 2nd hand engine or a "bunky" as @GTSBoycalls it, is likely the most appropriate option. 

For a 2nd hand engine, a colleague today suggested Asian Auto Spares in Slacks Creek (Brisbane) - they've been around for ages (he bought an SR20 from them >10 years ago) and they offer a warranty (1 month). Their website quotes $2500 for an RB25 (non Neo) - I haven't spoken to them yet re availability, ability to do a compression test etc etc.

I'm interested in others' views on what should be replaced on a 2nd hand motor - timing belt and water pump are obvious candidates, but are there others?

My current turbo is an HKS 25/30, ECU is an Apexi Power FC, boost controller is a Turbotech manual boost controller.

This setup was running 235kw at the wheels previously at 1 bar boost - I'd like to get back to that at least, but may throw some injectors and a fuel pump in to get closer to 245 RWKW.

I wouldn't push a "bunky" (2nd hand engine) past that (245-250 RWKW).

cheers

Mike

 

[GTSBoy]

On top of water pump and timing belt, all the coolant and vacuum hoses.  Possibly the crank seals.  Plugs definitely.  Thermostat.  Consider taking off and inspecting the oil heat exchanger for potential corrosion problems.  Look for signs of oil leaks at any significant gasket (cam covers, etc) and swap any that show.