Non Oem Timing Belts

[edizio]

I'm currently running a HKS kevlar timing belt for my RB26; I started asking around and I'm getting quite poor feedback from non OEM belts. The engine I am running is fairly powerful and I was under the impression that the kevlar belts were required for making big numbers.

I'm looking at replacing this belt now and I was thinking about using a tomei kevlar belt but now I'm thinking maybe just go OEM or gates, even though I'm running a lot more than a standard skyline.

Thanks!

[89CAL]

Mentioned quite a few time that you are running more power but havent given a figure. Will make a difference what people will recommend if your running 1000hp or 500hp

I run Gates, im running 'alot' more power than a standard 25 but its only around 300rwkw

No problem with my belt

[Ben C34]

How does power affect spinning the cam around?

Spinning is spinning.

[edizio]

Well, with power comes the extra stress from non standard cams and valves

I've always gone for the kevlar belts but it's just whether or not I'm doing more harm than good by adding additional wear on the water pump and tensioners.

[Ben C34]

With non standard cams and springs comes extra load on the belt.

Still nothing to do with power.

How would it wear the water pump?

[edizio]

I believe that the OEM belts have very little vibration whereas the kevlar belts tend to be more rigid which puts additional stress on the pump.

I'd be inclined to suggest that there is a correlation between a vehicle with higher power figures and uprated cams/springs. I certainly have none-standard parts on the vehicle in question which are part of the package for increasing the amount of power that it can produce.

I'm not an expert at this and if you're trying to prove me incorrect then I'm more inclined to accept this and listen to what you have to say; if you have anything constructive, that is?

[Ben C34]

What I have said is constructive.

Making more power doesn't mean the timing belt needs to be upgraded.

Running more aggressive cans and springs might mean the belt is under more load, but realistically with a 100,000k service interval on a stock engine, if you used an oem belt and replaced it every 50,000 that would surely be ample.

The timing belt doesn't touch the water pump, so don't worry about that.

Perhaps you are confused as the pump typically gets replaced when the timing belt is done, thats only because the belt has to be removed to take the water pump off so it makes sense to do it then (just like cam and crank seals)

[Ben C34]

Also the issue with different belts tends to come from them causing the timing to scatter, when using the standard cas in particular with aftermarket ecus.

[edizio]

Thanks for that! So if I change my HKS kevlar belt to an OEM, I'll need to tweak the ignition timing? I can do most of that stuff, I've got the equipment and some experience tuning on my d-jet PFC. Still using the standard CAS.

[Ben C34]

Not necessarily. If everything us working happily I'd leave it as is.

The scatter issue causes trouble when tuning, with the car pinging when it probably shouldn't etc.

The power fc doesn't seem yo be badly affected anyway, as it is an older and slower ecu which doesn't see the scatter like newer faster ecus do.

[edizio]

Well, unfortunately, upon inspection at the weekend, I found a small, almost incision like, cut on the kevlar belt; it's only a 1mm nick that doesn't even go deep past the surface but it's enough to bother me. It's probably been there since the belt went on, in all honesty, as it doesn't look like a wear and tear rip.

Probably just going to go with just replacing the belt with an OEM one as the HKS belt hasn't been on long, maybe 10,000km so no need to replace the tensioners, unless anyone thinks otherwise?

[Ben C34]

I'd leave the tensioner for sure.

[KiwiRS4T]

I have heard of people having problems with Gates belts but not with OEM (although no doubt there are lots of people who haven't had problems with their Gates belts!).

[jay-rod]

I have gates

Only problem i had was putting it to tight can cause "whining"

[iruvyouskyrine]

Have put on 7-8 gates timing belts and never had them whine. My mate (qualified mechanic) put his HKS belt on and it whines. I'm going to assume it's all to do with how much you tension them to rather than the gates belt itself tbh.

[Piggaz]

My HKS pink but belt is quiet as. Would say it's over tightened.

[GTRPSI]

There has been some extra timing scatter found when using Kevlar belts with high ramp rate cams with heavy springs.

So far much of it, including the noise produced has been thought to be the belt tooth design when meshing with the gears, current thinking of many engine builders belive this aggravates/adds to the scatter issue.

OEM has been found to be the least effected, or the most forgiving, or the best at absorbing the harmonics.

With force on the belts and the harmonics produced, its based on how much lift and how agressive the ramp rate (both opening and closing the valves) of the cam lobes is combined with high spring loads working against the lobes, these harmonics are transfered to the cam gears and on to the belt.

Enough spring force and crazy cam ramp rates can even twist cams on some engines (more so pushrod engines), in these cases billet cams that have the lobes joined are used to add strength to tie the lobes into phase from front to back.

Low gentle lift with softish springs should produce little force onto the cam belt.