Outer Limits 4x4 Board

.... .... ....







http://performanceunlimited.com/illustr ... aders.html

want33s wrote: .... .... ....

LOL



quote Performance Unlimited 'The more power an engine produces, the more important the exhaust concerns become...."

I think in the case of a standard 1.3 Sierra the concern is very minimal, but still.

I like listening to this banter... I'm learning stuff

-ZukChiK- wrote:

want33s wrote: .... .... ....

LOL



quote Performance Unlimited 'The more power an engine produces, the more important the exhaust concerns become...."

I think in the case of a standard 1.3 Sierra the concern is very minimal, but still.

I like listening to this banter... I'm learning stuff

Good point, it's not like there is much restriction.

Just another opinion, but....
In all the Suzuki engines I've tuned-1.3-1.6L they all run their best overall with the tri-y headers and 2" pipe . It doesn't have to be loud, just very free flowing and the correct diameter .

Backpressure is a bad term, exhaust velocity is the real key issue here . Stock cams really aren't very efficient with headers since there isn't much overlap at the valves . This is why most don't get much when they add a header to a stock engine . Add a decent performance cam and now the header can do it's job of helping the intake charge into the cylinders . Once the cam and header are added intake mods or larger induction including aftermarket carbs really makes a difference . Things have to be run as a package . For example, just buying the largest cam you can afford won't work well since the engine is trying to breathe through a restrictive stock carb and intake . Once all the valve work, cam, induction and exhaust is all done these little engines can really perform well . My own 1.6L will pull nearly 125hp at the ground now, but it's all been done albeit a weak block ....with higher compression it would be pushing over 140hp..
Sarge

Good to know Sarge, and I can see how that makes sense.
Which are the tri-Y headers again? the ones that are '1&3' & '2&4' pipes leading into 2 into 1?

I now have to check what my Hurricanes are... can't remember, LOL. But they have served me well over the years. Just looking for another set of headers for the soft top we're fixing up that are similar

You are correct, pairing of the cylinders is what produces the scavenging effect . Here in the States, Calmini and Thorley produce the best tri-y designs overall . I'm not familiar with what is available in Australia , but I'm sure there are some decent designs .
I've heard Calmini is releasing a new tri-y in stainless steel this year .
Sarge

Hmm, probably cost a fortune over here for the Calmini stainless if they ever get released in Oz. In fact I didn't even know they made headers!

Well, in my case I think the basic gain of having any type of extractor & a free flowing exhaust to match will serve better than the inevitably cracked manifold that has been on since stock... so, unless I can find a set of tri-Y's under $200 I think I'll get a set of the MPH's which are the 1-4 type. I don't think I'll notice the difference anyway, LOL.

Interesting how many myths have an element of truth hidden away in them.

As I understand it the removal of engine back pressure on CARBY equipped vehicles can lead to valve problems and lower performance.

This is how I had it explained to me.... With many factory exhaust manifolds ( which are a compromise like everything else ) there is measurable back pressure. The effect of this ( and a heap of other things ) is a reflected pressure wave which can cause a flow reversal through the carby - effectively richening the mixture. So the manufacturer corrects for this richening by making the jets smaller and so the overall AF ratio is maintained.

However when the exhaust is "improved" this reflected pressure wave is reduced, causing less flow reversal through the carby and ultimately a weaker mixture possibly causing valve issues and poorer performance.

These flow reversals are also caused by cam timing changes and on engines fitted with ram tubes you can often see a fuel cloud above the tubes intake on a dyno.

On any closed loop EFI system this is no longer an issue as the Lambda sensor gives the system the ability to maintain a correct AF ratio.