R33 Skyline Detonation Issues Hks Gt2835 Turbo Cams

[Turbz RB-25]

Hi Guys,

I got my car on the rollers again yesterday to fit my electronic boost controller and it was still having detonation issues.

I have an r33 GTST with a HKS GT2835 turbo, Pon cams on the the inlet side 256, and Pro cams 260 on the exhaust side with 8.5mm of lift (and yes the procams can be fitted on the hydrolic lifters as they are >10mm of lift), and all the other supporting mods; bocsh 040 fuel pump, 555 Nismo injectors, FMIC, PFC etc.

I am running 17 PSI and VERY conservative timing; in the mid range the timing is around 6 degrees advanced and at the top end it is around 11 degrees.

From my understanding, this is pretty low? The figure I pulled off yesterday in 34 degree heat was 260rwkw with around 27 knock figure on the PFC (which isnt too bad).

However, if we tried to advance the timing to around 12-13 on the top end, it would pull around 270rwkw but the knock was well above 100.

We tried putting top engine carbon cleaner through the inlet manifold which helped a bit but didn't solve the problem.

The tunner thinks it may be a hot spot on the piston somewhere which is causing the detonation?

I was running BP ultimate fuel.

What do you guys think it may be?

Before my VCT stuffed up, I was making 272rwkw with 17 PSI but WITHOUT the cams and cam gears and no detonation. WHen the VCT stuffed up I thought it would be a good oppertunnity to get cams fitted.

Anyways, what could it be, and what tests can I perform to discover the problem?

Cheers.

[The Mafia]

To be honest with you mate, thats about the best that turbo is going to do. Its probably at the top of its efficiency range and is running out of puff.

Either that or your rear housing is too small.

If you want to beat the detonation, get a Water Methanol injection kit.

[(OO)Firty Free(OO)]

I agree with Mafia with my car running 18psi anymore than 11-12 degrees up top would detonate in 100's also.

[Turbz RB-25]

I agree with Mafia with my car running 18psi anymore than 11-12 degrees up top would detonate in 100's also.

I made 273 rwkw previously with the same boost without cams and no detonation advancing timing by around 15 degrees on the top end.

Now I am making 260 rwkw with cams and detonation with timing advanced 11 degrees on the top end.

It doesnt make sense. Something is wrong.

Bear in mind my midrange timing is only 6 degrees advanced, any more and it would detonate. As I understand this is VERY low.

Could the adjustable cam gears have something to do with this?

[Turbz RB-25]

Would I have to re-gap the spark plugs because of the new cams?

[The Mafia]

mate, certain cams aren't there to make top end power, but to make the turbo come onto boost earlier, and give you more mid range. Have you overlayed the graphs and had a look at where you power moved to?

Edited January 6, 2009 by The Mafia

[Dale FZ1]

+1

An overlay would be great - especially if it's torque before/after.

Maybe you could consider playing with cam timing and move the torque curve around to suit your goals, and then get more serious with ignition timing.

Carbon deposits can cause problems with hot spots and preignition, but that doesn't seem to be something commonly encountered by people making mods?? Properly configured water injection will make a difference in controlling knock, but if your main aim is bigger power numbers then best go to a GT3037. Be interested to know if you've got a 0.68A/R turbine housing too.

[Turbz RB-25]

+1

An overlay would be great - especially if it's torque before/after.

Maybe you could consider playing with cam timing and move the torque curve around to suit your goals, and then get more serious with ignition timing.

Carbon deposits can cause problems with hot spots and preignition, but that doesn't seem to be something commonly encountered by people making mods?? Properly configured water injection will make a difference in controlling knock, but if your main aim is bigger power numbers then best go to a GT3037. Be interested to know if you've got a 0.68A/R turbine housing too.

Yes I have the 0.68 A/R.

I haven't plotted the old and new dyno sheet in the same chart, however, by looking at the two side by side, I have lost power everywhere.

I have lost power in the low-mid range because boost comes on alot later because the VCT was removed and the cam gears were installed. Top end power was also lost because the timing was ALOT less in comparison to the run I had done without the cams.

SO in other words, I have less power and less torque throughout my whole curve. This is why I am saying that something is wrong.

We tried playing around with the cam timing to get the same power curve I had previously without the cams, it was close-ish, but still less than without the cams.

I am going to by some more top end engine cleaner today from subaru and give it another clean. maybe it might help some more.

I am thinking it may be a spark plug issue in that the spark plug is getting too hot and causing pre ignition, or, there is a hot spot somewehere on the piston causing preignition...

[Lithium]

Does the tuner use an EGT probe, or even better do you have any way of measuring intake vs. exhaust manifold pressure? There is the possibility that badly dialled cams could cause such an issue. Another option if you have lost power everywhere... are you actually using the exact same dyno as last time, or has anything such as wheels/tyres changed? Silly questions perhaps, but I know most Oz tuners are still using old rolling road dynos which seem to be finicky/inconsistant at the best of times.

Also rule out the possibility of air leaks etc, is it at all laggier than it was before?

[discopotato03]

Two things could be looked at here IMO , firstly you could try using the matching Tomei exhaust R33 Poncam and refitting the std VCT assembly .

I am curious to know what made you decide on the 260 10.5 Procam on the exhaust side .

Correct me if I'm wrong but is the 260 10.5 an RB26 or Neo25 cam ?

Secondly , some will disagree , consider using the larger 2835 Pro S 0.87 A/R turbine housing .

I know people have different ideas about cams and turbos but if the power output and detonation threshold falls then I think it's trying to tell you that the combination is not so good .

I haven't heard too many people say that R33 Poncams were a backwards step , also IMO headwork done well really enhances the breathing and performance everywhere .

My thoughts only , cheers A .

[STATUS]

i reckon you might be getting float too.... anything bigger than pon's on stock valve springs usually ends in tears.

timing sounds way off to in the mid you should be able to have at LEAST 20 degrees tapering down to about 13-14 (if base timing is set correct. The car i just finished 10mins ago was happy @ 18 degrees at 18psi (pfc load line 154000 ish) std rb25 except for bolts ons (base timing was set also) Plugs were BCPR7ES.

Oh what cam gears? i had issues with some VISION / arespeed ones awhile back they were ground like one tooth out.... customer lost 20rwkw's by fitting cams and these gears, i have since built an engine for another customer and he supplied the same brand and they are also out one tooth when i dialed in the cams....

Edited January 7, 2009 by URAS

[PM-R33]

Sounds like the same issue i had with my hks 256/264 cams and stock valve springs. Made less power every where and started knocking badly when we put timing into it. Ended up pulling the head off to do the valve springs and a bit of head work. I reckon your having a similar problem on the exhaust side with too much lift on old standard valve springs.

[Turbz RB-25]

Sounds like the same issue i had with my hks 256/264 cams and stock valve springs. Made less power every where and started knocking badly when we put timing into it. Ended up pulling the head off to do the valve springs and a bit of head work. I reckon your having a similar problem on the exhaust side with too much lift on old standard valve springs.

Sorry, I failed to mention that I have the type A Tomei valve springs in there so it rules out float.

As for the Pro cam, it is NOT 10.5 lift, it is 8.5, thus, suitable for the hydrolics lifters the R33 has.

I am really not too concerned anymore as my RB30 bottom end is coming in soon with my GT35R, but anyways, it's still buggin me.

Thanks for your help and comments anyways guys.