4-2-1

[bluezak]

Hi there, I have just brought a 4-2-1 manifold to fit to my autograss puma. The exhaust has just one plug hole for the lambda sensor at the back of the section. I think my puma has a pre cat and a post cat sensor, if that is the case then which do I put into this hole seeing as the car will now not have a cat and I don't want to startle the computer too much!

Thanks in advance, Chris.

 

[Flying Scotsman]

If it has no cat then you want the green one in, sack off the blue one

 

[Kidders]

If it has no cat then you want the green one in, sack off the blue one

Won't it throw a code?

 

[Flying Scotsman]

If it has no cat then you want the green one in, sack off the blue one

Won't it throw a code?

No it'll be fine, Have done the exact thing to a Puma in my household.

 

[Glenn_]

So on a standard car would fitting the green sensor only bring the engine light on.

 

[bluezak]

well it turns out mine was an older model and it only had the one lambda sensor and the car now runs very well with the 4-2-1. The fuel consumption seems to have gone up, I just hope this means more power!

 

[ArtfulHussy]

Seeing as Chris' problem has been resolved, and whilst on the subject of 4-2-1..

Can I hijack this thread and ask what the benefits of a 4-2-1 exhaust are? I'm going to sound stupid here, but I was under the impression all exhausts (on a 4-cyl) started with 4 pipes and finished with one. So I'm not sure what is special about a "4-2-1"? If someone could enlighten me on this I would be most appreciative.

Sorry if hijacking this was a boob. Just seemed silly starting another thread..

 

[bluezak]

The way that I understand it, is that it increases the airflow out of the engine allowing the ease of flow of air back into the engine and making it take on more fuel and then it increases the power of the engine. I have read different things about the BHP increase but most say between 5-15BHP

 

[Milkie]

4-1 Exhaust Manifold will give more power at the top of the rev range
4-2-1 Exhuast Manifold will give you power mid range power

You usually find a 4-2-1 manifold on a road car and a 4-1 on a race car. Which is why I am a little confused as to why people change the 4-1 to a 4-2-1 on a track day/race puma...

 

[Glenn_]

I still want one of these for my puma. Mine has the 2 lambda sensors so it will be a bit harser to do.

 

[ArtfulHussy]

So, with the 1.7 having vct, would the most benefit in performance not be gained with a 4-1, which would work with the vct higher up the rev range when it kicked in?

And while we're there, roughly when does the vct come into effect?

 

[RyanG]

4-1 manifolds work best with very high revving engines there would just be too much of a loss to put one on a relatively standard puma engine. You would probably gain around 5bhp but loose loads at certain lower revs

Another way which is very similar to removing the exhaust gases at high rpm is to change which cylinders are linked together in the 4-2-1 if you look at my build thread i had a reversible manifold to try back to back on my engine.
With the cylinders linked like a conventional 4-2-1 in which cylinder 1 and 4 then cylinders 2 and 3 are paired it gives you very good mid range power and still good top end

With cylinders 1 and 2 paired then 3 and 4 paired i lost 30bhp at 4000rpm iirc but gained 7bhp at the higher rpm, this was worth me using the top end manifold as my 1.7 vct puma engine didn't make peak power until 9000rpm and held within 2bhp till 9500rpm.

Also one of the most impressive cheap items i have come across was the ebay 4-2-1 which are £169, this manifold made 222bhp which was within 1bhp of a earlier works s1600 manifold we back to back tested it against.
This manifold also just made 182bhp and 143lbs ft of torque on our throttle bodied standard bottom end puma engine.
Trust me there isnt alot of pumas out there that would need a manifold made to a higher spec then this.

 

[ArtfulHussy]

So.. 4-2-1 is better for our engines when standard?

Sorry, I did try to follow that but I think I got lost.

 

[RyanG]

Yes much better, there just isn't any reason to go away from the frp designed 4-2-1 manifolds.

 

[ArtfulHussy]

I see. Food for thought if I ever start trying to squeeze some ponies outta my cat. Thanks

 

[bluezak]

it was the ebay one that I brought. Its under direnza puma 4-2-1 and they seem to auction one a week off too which is what I won for £100 instead of the buy it now price of £169. :grin: It links 1 & 4 and 2 & 3.

Its got a more throaty sound to it now and seems to be using a little more fuel so hopefully that means its more powerful, even if it is not, it has got rid of the CAT which will have saved a tiny bit of weight. Need to get it onto a weigh bridge and a rolling road and see what the specs are like now.