timing belts - race vs OEM

[NOLAW]

Hey guys, pretty basic question, whats the differences between the race timing belts and the factory OEM one, and is it worth paying the extra $?

cheers

[iOnic]

They're stronger which = less stretch at higher than stock RPM. Not really necessary. Stock belt will do just fine and stretching is only really a problem if triggering off the cam which can result in timing shift. And again, you have to be spinning fairly quick, all belts stretch a little as engine speed increases.

[jondee86]

Works on the same principle as the $95 TRD billet oil filler cap

Cheers... jondee86

[DVSMOTORSPORT]

Out of all the race engines Ive built and seen built (NZRC race engines etc) not a single one of them had one of those belts fitted.

[touge_ae101]

it can make a difference to the tunability of the car. as a race belt has extra reinforcing etc so won't stretch at high RPM/load. i have heard it can make as much as 3-5deg of timing at the top end which is a bit to have to account for when tuning.

but best to look at such things in perspective. extra $$ vs probably unnoticable gain. prob only be worth it on mega cutting edge engine.

[RomanV]

Or made redundant by VVTI, which can accomodate for belt stretch.

[MAGN1T]

Do timing belts actually stretch?
How much by?
Where's the proof?

Steve

[touge_ae101]

Do timing belts actually stretch?
How much by?
Where's the proof?

Steve

the internet. everything you read there is the truth.

but srsly had this discussion with a mate (ONPSI) who attended one of the STM workshop thingys where they explained all this type of stuff. Lith will prob know more about it than anyone else who frequents on here.

[iOnic]

I attended the same thing as Haagen and Daniel (Lith) and yes it was pointed out (with evidence) that this happens and what effect it has on your tuning strategy. I've personally seen it plenty of times on various engines. Many ECU's can take this into account with constantly variable trigger angles eg below. You can tune around it and it's not much of a change but bear in mind that the belt does have a breaking point so if it's getting a fair bit out it's probably safer and cheaper to get a stronger belt. Doesn't have to be a bling brand, various other brands make belts with more reinforcement than stock.

http://files.haltech.com/downloads/plat ... gger_angle

"Race" belts are pretty much a case of you either need it or you don't. If there's nothing wrong with your current belt, you won't gain anything from getting an expensive "race" belt - don't waste your money. But if you have huge cams and are chewing belts after a few thousand hard kms or have a stretching issue, then there is something to gain from having one. Or you could just replace them every couple months I guess?

[MAGN1T]

Normally when a cambelt fails, the belt itsself is intact, it's just the teeth that come off.
In fact even cambelts that run around the waterpump, when the waterpump seizes, it'll start to melt and smoke but won't snap.
Personally I think the whole "stretch" thing is a load of shyte.
The strength in the belt is normally fibreglass or for the ricer versions it's carbon fibre.

There you go, you can find anything on the interweb.

http://www.aa1car.com/library/ar594.htm

Timing chains are bad for stretching though, that's because every link is a bearing which wears, no different from bike chains which need constant adjustment.

Steve

[iOnic]

You're the expert.

[MAGN1T]

No, I don't know anything.
But know enough about most things to know when I'm being told porkies.
I've been told plenty of porkies by persons who should know better.

I used to have a townace with a 3Y in it, the chain on that was severely stretched, you could hear it rattle.

More than likely STM got mixed up between belts and chains.

Steve

[iOnic]

No, I don't know anything.

I'll take your word for it.

[Grrrrrrr!]

Oh dear, Magn1t is confusing plastic yeild with elastic yeild.

Simple fact is nothing has a youngs modulus of infinity, so everything stretches as tensile load on it is increased. So yes, even those $260 race timing belts stretch, just hopefully a lot less.

[Emperor]

No, I don't know anything.

I'll take your word for it.

Seconded.

Minutes taken.

MAGN1T for president of $&#$% all.

[Luke - BZG]

More than likely STM got mixed up between belts and chains.

Steve

Yea, I bet a tuning company like STM hosted a course full of people who know a thing or two about tuning, and discussed more in-depth concepts about tuning and engine performance and not a single person realised a huge mistake like that.

[Mr Revhead]

Oh dear.

The thing that will apply to what belt you need is the state of tune of your engine. As mentioned unless it is a wild beast a stock one will be more than fine.
I would be keen to see examples of proven belt stretch causing issues. Would be interesting to see at what level it became an issue.

[matt dunn]

I can see that an engine where all the position sensing is done from a camshaft like the 4AGE's or the Nissan RB engines and they done have any actual sensor on the crank,

that there will be enough, lets call it "stretch" to make the timing a few degree's out.

if a few degrees of timing change makes a difference to your engine or not is another matter.

[NOLAW]

the engine im running is a very similar setup to the 7agte in barrys levin, although because its going into a KE20 i wont be planning to run it on 300+ kw all day everyday, thats not to say i wont wana take it up to there at some stage though just to see how it does

[loudstealthGT-Four]

No, I don't know anything.


Steve

Then please stop posting stuff in the tech section