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Timing issues on RB25DET

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Hi everyone,

Being new to Skylines, this forum and the fascinating world of hitech engineering, I am amazed at the overall high quality of input and responses in these technical forums. Obviously some very clued up people haunt these pages and I feel quite fortunate to be able to seek some advice when little appears to be on offer elsewhere.

I have a power issue (duh!!)

Just had my car in the workshop having the Micotech sorted once and for all...... or so I thought!!

Seems that the motor just won't take any advanced timing!?

Currently running 15 degrees timing, a plug gap of .55mm and 12psi of boost, it's netting 165rwkw.

But that's all she wrote!!.......open the plug gap and it'll misfire.....up the timing and it'll ping!! She'll no take no more..........

Currently running 3" system, fabricated 3" dump/front pipe, Greddy front mount, GTR fuel pump, steel wheel (stock?) turbo, Pod, Cold Air box and Microtech ecu). Fuel used is Caltex Vortex 95RON.

Apparently, under normal circumstances (with this sort of setup), the R33 should be able to take up to 25 degrees of timing and be happy running a plug gap of .7 - .8, and up to 14 odd psi of boost.

A fairly safe state of tune would be about 20 degrees, gap of .7 and 14psi of boost. This conservative tune would be running close to the 200rwkw mark.

What's wrong with this picture?

It feels as though the problem is something quite straightforward, possibly something that may not have been setup properly from the start........

Any input here would be greatly appreciated.

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I like your first paragraph because i think its true :( There is more technical learning on sau then any other forum, and with such a large amount of good members it makes a great place to be apart of.

Ok, timing;

Im not to expeirenced with engine timing but i know that you shouldnt be focusing on timing to make your power. Realistically the lower the timing the safer its making the given power. Now also, the fuel you are using is fairly low RON, 95 is only a few RON off normal unleaded. In japan the minimum any descent turbo skyline is run at is 100RON. So use BP Ultimate or Shell Optimax which are 98.

The burning properties of the fuel you are using on boost, is directly related to amount of pinging/missing from the engine on boost.

Also, the standard turbo, which many of us know :), doesnt really do much after about 11-12psi. The difference in power from 12 to 14 is minimal.

165kw isnt bad considering the setup altho it probably should be making a little more, just remember, certain dynos may read 165, another mite be 175, which of the latter could be correct.

It could be alot of things though, faulty coils at high RPM, some kind of induction/piping leak, a faulty sensor etc

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Yep its the fuel.

When my R32 was stock (and that is running a lower static comp of 8.5:1 compared to your 9:1) I ran BP Premium 95, not knowing there was a difference between premium and ultimate etc..

It made 115rwkw with 95ron fuel, stock exhaust, stock airbox, stock ecu - stock everything. :P

After the good fuel and a bit of timing it made 125rwkw.

With the crap fuel mine also pinged like bugger with anything more than standard, warm days or a long squirt also had it rattling.

I put 98 Ultimate in and it made more power due to the 22degree's worth of timing, on 15psi it made 164rwkw, stock ecu, stock airbox, 3" turbo back exhaust.

The fuel was fiddled with (regulator) the lean it out to just under 12:1.

With decent fuel and a good tune you should be up around the 180rkw mark.

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Hey mate, I got your PM, will reply to it when I have a bit more time. I know the reasons you use Vortex (work Caltex fuel card) but have you considered getting Shaun to do a map for Vortex 95RON and another map for 98RON? If you have a Microtech handset (~$160-$200AUD new) then you can actually store 4 completely different maps in it. You can then switch between maps in a matter of 10-20sec.

As for the misfire issue, hmmm it's got me puzzled. I run 20+psi, same ECU, stock coils, plugs gapped to 0.8mm and I rarely have misfires unless it's really cold and the plugs are a touch fouled up. Once the plug temp comes up it doesn't misfire at all. What heat range plugs did Shaun use?

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As it's already been stated, it's your fuel. I would run it a little richer too. If it's pinging on 20 degrees (which is stock timing for a GTi-R) then it's not getting enough fuel either.

I would for the moment (until it's sorted) reduce your boost. Melting a piston will break your heart.

If you must run vortex, then you'll need octane boost to run higher boost on higher timing. Wynns "Race Formula" *cough* is available almost anywhere that sells fuel but it's a hefty $22. It will raise it to about 98-99 ron which is acceptable.

Amaru's gtr dies on 98 ron occaisionally, and when it gets to 102 it runs perfectly. Those 4 points are your friend.

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Im not to expeirenced with engine timing but i know that you shouldnt be focusing on timing to make your power.

That's true for his setup, but I wouldn't say that as a general rule.

You'll have to excuse me, I'm a timing nazi :wassup:

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The 165rwkw recorded was in shootout mode. When I originally picked up the car, it was putting out 176.6rwkw in shootout but when I brought the car back to get rid of the slight misfire and ping right up the top of the rev range, the power dropped back accordingly.

But Shaun still seemed to expect better, even with the Vortex fuel.

I agree that the grade of fuel could contibute significantly to my current situation, but could it be that simple? Shaun seemed perplexed at the sensitivity of the timing and the fact that it was not reacting at all the same as the other Skylines he looks after, a couple of which belong to some well known members on this forum.

If the timing belt were out by one or even two teeth, what would be the effect? Would there be a seat of the pants feeling that would make it obvious.... would something noticably screwy happen when you hit it with a timing light? Is there even a remote possibility that this is why it seems to be "responding abnormally" to normal tuning methods? :confused:

Is there a simple way of eliminating this possibility without tearing the engine apart?

Or should I just shut up and fill it with Optimax.....:wassup:

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The plugs he put in were NGK BCPR6E (VL Turbo). But says that he normally sets them up with a gap of .7 - .8mm but couldn't get rid of the misfire. After much head scratching, he checked the gap on the cold plugs that Tilbrooks last installed and they were gapped at .5mm!! He regapped to about the same and the misfire went away!?

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That's not a bad idea Matt!!

I actually went out and bought the Hand Controller and the Laptop interface from Tim before I took it to Shaun. He even set me up that nice little "valet" program when it was in last. But you're right, I should experiment a bit with the fuel anyhow and get a separate map done to suit.

Just I'm reluctant to blow any more money on tuning if there's a possibility of something more fundimental at play which is preventing it from reaching it's most basic potential. Would rather eliminate the possibilities or spend on having it corrected first, then have some fun in the tuning department!!

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Yep I understand and agree mate - re fixing any fundamental issues first.

The crux of the issue is the fact that it won't accept any additional timing above the stock 15' without detonating. Without a "little" extra timing it's hard to make reasonable power gains :( Look at the Japanese, they use very rich A/FR's and HEAPS of additional timing! This gives a nice piston cooling mixture (drift and drag friendly) plus sharp throttle response (very drift friendly).

So why won't it take extra timing??? Hmmm... the timing belt idea is interesting, what did Shaun say about it? I still think it might be worth filling the tank with BP Ultimate and putting it back on the dyno, then just advance the timing slightly and see if it still wants to ping. Fuel "can" make a huge difference.

The tiny plug gap wouldn't be helping power either :P Weak spark due to a poor igniter perhaps? A dodgy coil or 2?

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Shaun wasn't sure what the underlying cause was....that's why I thought I would let the problem loose here and see whether any good ideas popped up!!

The only reason I brought up the timing belt was because Tilbrooks did this about 10000km ago. Trouble is that the original owner didn't even realise it was pinging when he sold it (so he says). This makes his account of it's history a little unreliable.

Shaun thought it was a coil or two, so he got a couple of s/h units in. He swapped out #1 and he reckoned that it was all fixed. I collected it on the Wednesday night but it was pinging over about 6000rpm and misfiring over about 4500rpm at WOT. That was when I took it back. He just gapped down the plugs and that fixed the misfire, took some timing out to loose the ping.

At that point he began to doubt whether it wasn't the coil at all.

I might have a play around with the coil packs over the weekend, give them a clean up, visually check them for arcing and run the multimeter over them.

I know you can test a coil with a multimeter while it's just sitting there, but is there a way of testing a coil under heavy load to confirm whether it's arcing?

Any idea of the best way to check the ignitor pack?

As for the Injectors Joel.....dunno! Fuelling didn't seem come up as a concern on the dyno, that part seems to be quite controlable and consistent at this stage of the tune.

Still feels like something on the ignition side or mechanical timing........:confused:

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Hi R334door, I have re read this thread a couple of times and I see no reference to the A/F ratios. If you have them, can you post the power graph with A/F ratios and boost. The Microtech has air temp correction, which I assume is being used, if so a graph of that will be handly as well. That will help the diagnosis a lot.

What model of Microtech is it? Are you running wasted spark? Have you paired up the injectors (ie; using 3 injector drivers)?

I have never run a Skyline on anything other than 98 ron, it simply isn't worth it. Since you have a "free fuel" advantage, I would suggest a 20% mix of toluene (I use 10 litres of toluene with 40 litres of fuel). Don't get it on your hands or inhale it, it's not nice. One tank full and $50 on the dyno with the items above logged will eliminate many things.

Hope that helps :(

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You can check to see if your timing belt has slipped.

1. Remove your spark plugs, CAS and cam gear cover.

2. Jack up rear of car

3. Place in fith gear

4. Rotate the rear wheels by hand and have someone watch the crank pulley until it reaches TDC

5. Repeat this process until the marks on the cam gears are also at the top. (there are 4 strokes, so there are 4 cam positions)

If the cam marks are not straight up when you are exactly on TDC (either in/ex) then your timing belt has slipped or been fitted incorrectly or your idle tensioner seized etc etc.

That shouldn't cost you any money and only 25-35 minutes.


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If it was an injector playing up that could very well cause a cyclinder to run a little lean hence ping, the AFR's would still be fine as the other injectors would be running slightly richer to make up for that one running lean.

The AFR's are a average over the whole 6 cyclinders not every individual pot.

I still think its the 95RON fuel, My car was exactly the same.

Made no power, pinged even on standard timing (only slightly but) and standard boost.

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Guest Robo's

I once had to put 95 octane in my car (thats all they had up bush) in the same state of tune its now, and i will never do it again, it ran like a pig, i was too scared too floor it as i was worried about my motor. Never again, it loves 98 octane!!

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I would have thought you would be making close to that power you have with a stock ecu....

I would be interested to know what model Microtech it is - also, who set it up.

If you can find someone with a power fc, or even a stock ecu, it may just be worth seeing how it goes. My initial suspicions are ecu.

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it could possibly be aftermarket cam pulleys, i heard a story similar to this some time ago, a completely stock car that wouldnt take any timing at all without major detonation,

after trying everything they decided to check the timing belt and found that there were some aftermarket cam pulleys, with some messed up settings dialed into them.

open her up and have a look.

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