Timing Fluctuations In Rb26/30

[HYPED6]

Ill grab them today.

The balancer we used is a Ross one funnily enough how ever instead of needing to use there particular balancer we made a billet adapter to fit in the front of a generic Ross balancer.

This will also fit any disk type on it. Of any teeth configuration.

The kit we made uses a modified standard cam sensor disk that any one can do at home.

When I was doing the testing, one of the problems I was having was that when we ran 72+1 (36 teeth on the crank one on the cam) I was getting a condition that the crank sensor would trigger on the falling edge.

Now if you could imagine the engine sees 1 cam...... 72 crank.....1 cam.....72 crank....... some times I would get....... 1 cam 72 teeth 1 cam 71 teeth 1 cam 73 teeth 1 cam 72 teeth.

Now some of you may thing thats no big deal.... But if you think about it that means that I am getting timing jitter over over 10 crankshaft degrees. Thats MASSIVE!

Imagine your tuner adjusting timing by 0.5 of a deg, trying to find MBT and having movement over 20 times your adjustment that you cant see.

Let alone what this looks like in your map with some ECU's jumping over 2000rpm at a single RPM point.

I'll grab some photo's today. There are some changes that need to be made to the kit but should come in well under 2k and be able to use any triggering configuration you need.

Edited February 7, 2011 by HYPED6

[Scooby]

I think the reason that some people don't have too much regard for this is that there are RBs reliably spinning to 9k rpm everywhere and holding together nicely without a crank trigger. While no one doubts that scatter occurs, some scepticism is understandable in terms of whether money needs to be spent on a solution.

Can your kit be fitted to an ATI damper and does it work in a stock config ie with a/c etc?

[STATUS]

i have heard of CA's having the same problem, there is a data log file in the Haltech formus that shows the CAS signal from a CA that was inflicted with this issue.

EDIT!! Here is it.

That could be noise (wiring issue) as your map signal is also pretty average around the same spot or its just picking up the duty (map pulse) on the boost controller..

[D_Stirls]

Not my car, it's just a data log that was in a Haltech thread that i remember was discussing the same issue.

This bloke fixed the problem buy going for a Crank Trigger setup and now this CA is running a bit over 700hp (Swedish Car).

I've bough a Haltech E8 that i'll be using on my car when i fit a GT3071R (or BW EFR) so we'll see if i have the same issue.

Just to confirm, (my understanding, is this correct?)

This issue is caused by the processor speed of certain after market ECU's?

So that is why the slower processing factory and P-FC ECU's don't have an issue as they don't process the signal quick enough to pick up the tiny fluctuations that the timing belt cause to the timing signal?

Basically 360 signals per 2 crank revolutions is too accurate if the processor is quick enough to pick up on the tiny fluctuations?

Edited February 8, 2011 by D_Stirls

[Scooby]

I think it's the other way round (see previous post re patent details of Nissan CAS signal processing) ie the Nissan ecu can read that many slots, the others can't and after an rpm point lose resolution hence the scatter ie they get overwhelmed. Bit like trying to keep focus on one individual blade on a spinning overhead fan, after a while most people lose it. Add more speed and you've got no hope.

The other theory is mechanical ie movement in the pulleys, cas, and belt flop.

What's not known is why some seem to have it and others don't. Of those that appear not to have it, it's conceivable that some actually do but it hasn't been picked up, or it has and its been tuned around. Then I've spoken to tuners that say they do check for it and some simply don't have it.

[Duncan]

Scooby...what was the outcome for you?

I had my car on the dyno today, very standard motor with a nissan timing belt and CAS. no timing cover because I was setting the CAM gears.

This is the trace of RPM from datalogit:

Have a good look at the trace in yellow. it goes from 7700 to 8000 revs instantly and incorrectly.

Now this is not a big deal, it is only moving between 2 cells in the tune so I just worked on an even, broad range in those cells.

I watched the timing belt during the dyno run. There were 3 distinct times that the belt was visibly vibrating, and 2 times in between in ran smoothly. Here is a zoomed out version of the same run from 3000 to 8000

so....this seems very reasonable to me.

Wow, I really didn't think this was a topic that was soo miss understood.

Timing jitter is something that has plagued RB engines since the dawn of time. The worst is the 30 single cam.

Now fact of the matter is, you are measuring the crank off the camshaft. Now between the crank and the cam sensor we have......

A bearing that the sensor shaft runs on.

The shaft it self that goes in the camshaft.

A rubber belt.

......

The best option is measure the crank off the crank. I have just been involved in making a bolt on billet kit for RB series engines. We started with a 72+1 then tried 72+1 with a missing tooth.

Just because not all tuners pick up on...doesn't mean there is no problem. And does it prevent you tuning? Probably not in most cases....it just introduces innaccuracy.

[R31Nismoid]

The section you highlighted is not the only point of issue as i see it.

It's occurring all through the rev range from 6,000 with the rise/fall

It simple does it twice around 7,700

[Scooby]

Hi Duncan

Unfortunately no outcome yet. I agree it doesn't stop you from tuning but mine was moving around 500rpm at 6k, presumably it would have gotten worse at 7500. Yavuz said he could tune around it so that no matter which way it went it'd be safe, but not really optimised as the safety margin for timing would have to be significant.

Mark

PS you have PM.

[Mark-32]

Old thread i know but can anyone put me in touch with Paul from red r racing. I'm having this trigger issue at 5000rpm on my rb26 and need to get hold of a 24 slot trigger disc for my cas. I'm having the problem as im running a vipec v44 ecu. For people's information we tried haltech platinum series ecu and its able to read the signal no problems so its an ecu dependant problem

[Marko R1]

I'll pm u his number

If paul asks, tell him 'rattledick' gave u his number

[Mark-32]

Thanks bud.

[Marko R1]

NP more than happy to help where I can

[STATUS]

Bit of an update we have found that the gates belts (especially the blue ones) are in certain cases causing issues with timing oscillation, the audible humming seems to also induce more belt oscillation at high rpm than the std Nissan belt. After swapping back to genuine belts the issues were fixed (3 cases now). No matter which way we adjusted the belt tension we could not get rid of the problem... fitted std belt with factory tension... issue fixed.

If anyone has some new ones handy it would be good to get some secondary measurements on the tooth profiles, I have had a customer make comment (after measuring them up) that the blue belts have a slightly different profile and are not as snug in the cam sprockets as the genuine belts.

I dont have any new ones handy to compare but it may be worth looking at if anyone gets bored. It wont be the case in every timing issue but one that is worth looking at if you run one of theses belts.

[PSI086]

Thats a very interesting thing with the blue gates belts. I had terrible timing jitter with my RB30, even at low rpm and after reading that the belt was probably a big contributing factor. I guess a reasonable size cam would make it worse also. Ended up going with a basic crank trigger set up and its been perfect ever since.

$60 home made crank trigger using a GT101 sensor and 3 slots in the balancer

Edited June 19, 2012 by PSI086

[GTRsean]

Nice work!

[KiwiRS4T]

Thats a very interesting thing with the blue gates belts. I had terrible timing jitter with my RB30, even at low rpm and after reading that the belt was probably a big contributing factor. I guess a reasonable size cam would make it worse also. Ended up going with a basic crank trigger set up and its been perfect ever since.

$60 home made crank trigger using a GT101 sensor and 3 slots in the balancer

Impressively simple! Did you use existing bolts or did you have to drill and tap them? What ecu are you using it with? Where does one obtain a GT101 sensor?

[kitto]

Where does one obtain a GT101 sensor?

RS components. $57.50 + GST here. Not sure if you have RS in NZ?

[Simon-S14]

Impressive in that it only requires 3 slots to function correctly

[Lithium]

Hi guys, a mate (not on this forum) has an issue with their Skyline running an R34 sourced RB25DET - the car is running a G4 Link and can get sporadic detonation at points from around 5000rpm up running no more than 12degrees timing on 1bar of boost with high 11:1 AFRs, this thread makes me wonder if this issue could be occurring and causing the intended timing to become much much more than intended timing?

[Simon-S14]

Trace the timing on the link and all shall be revealed.

I know with my Neo cas I get random rpm spikes of 16,000 rpm logged on the haltech.. Rare but it happens. might look into crank triggers