Janspeed manifolds - Worth the money?

[Mark S]

Originally Posted by dave23572

If only I were able to make such a thing!

It's a shame there was never a performance replacement for the entire plenum (apart from the Sprintex supercharger plenum).
The normal plenum really doesn't look like it would flow well. And we all know how well designed and reliable the VIS system is don't we?

Theoretically, I expect with the exhaust manifold you described and an optimal plenum, the KV6 would have performed much better.

very true, if you sorted the plenum and exhaust, dropped in some cams you should see 200lb/ft and around 220-230bhp.

[Fred68]

With a decent set of manifolds and well designed exhaust system, the standard ZS180 would be a ZS195 or there abouts. Include a well flowing air filter housing and the std 2.5 V6 will make 200 bhp.
We don't really know how much is gained or lost by the plenum as not many have replaced them. I know of a couple of Rover 800 KV6 twin TB inlets. As to the power of those, I'm not sure.
Looking inside the plenum, it's a wonder the engine makes what it does.
It's almost like MG Rover built in HP restrictions. As to why, who knows, but I suspect it was to do with budgets.
Don't forget that in the right hands, the works 2 Liter KV6 made near 300 Bhp!!

[top_man_eldo]

Originally Posted by Fred68

With a decent set of manifolds and well designed exhaust system, the standard ZS180 would be a ZS195 or there abouts. Include a well flowing air filter housing and the std 2.5 V6 will make 200 bhp.
We don't really know how much is gained or lost by the plenum as not many have replaced them. I know of a couple of Rover 800 KV6 twin TB inlets. As to the power of those, I'm not sure.
Looking inside the plenum, it's a wonder the engine makes what it does.
It's almost like MG Rover built in HP restrictions. As to why, who knows, but I suspect it was to do with budgets.
Don't forget that in the right hands, the works 2 Liter KV6 made near 300 Bhp!!

Fred you sound like you know what you're talking about, why don't you make up a batch of these exhaust manifolds for the 180?!

I'll be the first to put my name down!

[Mark S]

I know of only one person who had custom mani's made (that were of a tuned length - forget haywood and scott) and they cost more than most people here would want to spend on a ZS!!! (although they are very good) Small quantities are still expensive until you get the numbers where its worth making a jig to produce them...unless you can find someone who would do it as a labour of love...???

[petet16]

Did Tony Law make some as well ?.

[top_man_eldo]

Originally Posted by petet16

Did Tony Law make some as well ?.

I was talking to a fella from Ipswich way on MGR forums a while ago and he was going to have a go at making some for the KV6, not sure whether he eventually got round to it.

[Fred68]

Originally Posted by top_man_eldo

Fred you sound like you know what you're talking about, why don't you make up a batch of these exhaust manifolds for the 180?!

I'll be the first to put my name down!

My knowledge of what works and what doesn't comes from building some rather interesting engines back in the 80's. Then things were limited by head flow capacity.
With modern multi valve heads, it's the bolt on bits that limit power from the factory instead. The KV6 seems to be worse than other engine in this respect. It's almost like MR Rover were worried about warranty claims, deliberately down rating the engine.

I did loads of mods to my first ZS180 some time in 2003. I did use the JS manifold and custom made system to match. I was never happy with the manifolds though.
It wasn't until I did some number crunching that I realised that the primaries need to be long.
With the KV6, it's all about optimisation and knowing what does and doesn't work.

The problem with making up manifolds and systems now would be sales volume. There just isn't the demand for them to make it a viable proposition.
This would leave you, the owner to find an exhaust fabricator willing to make a 1 off.
The JS manifold will work for most owners needs and it is miles better then the factory manifold. But it's far from optimal.
This was discussed at length some years ago on XPF.
I don't have a ZS180 any more.
I do still run a KV6, sadly it's coupled to an auto box in a Freelander!!

[petet16]

The sales volume issue is a valid point, a while back I spoke with JS about making up some duel outlet systems for the 180, they would only make them in batches of 5, which I would have fronted the money for IF I thought there was any chance of selling the other four on, as it turned out I was pointed in the direction of a used system on ebay, so the JS idea never went anywhere.

[Skillen]

Just thought I would see how much a mandrel bending machine would be thought I may as well give it a blast by myself and what better way to start to learn to weld.
Well I gave up at the mandrel bender part. £15k for a pneumatic one. Nearly £600 for a manual one.
Ha. I'll stick with my janspeeds.

[Fred68]

Thankfully there are lots of ready formed bends available for the home constructor. These would need welding together to make pretty much whatever you need.