Exhaust and Manifold Combo

[StiflerMR2]

Hey all,

Having resolved to keep the S1 rather than swap it for an R (unless anyone is selling a cheap 190 Exige...anyone?...no..okay.... ). The next logical step was to throw more money at it

It's almost time to send it north on it's yearly pilgrimage to Mr Moncrieff so as always I'm drawing up a list. I know it can be risky tuning the K and tbh, 118bhp is enough, but I image a few of those ponies have left the stable.

In a bid to recover them (and because my current back box is looking a little worse for ware) I was wondering if anyone had any advice on manifold and exhaust combinations that might offer some increased HP?

If anyone has any recommendations please let me know. I'll chat with Craig but he's such a good gent he'll probably try to stop me spending money!

Cheers,

-Mark.

[mwmackenzie]

The elise parts 4 branch looks good! I had a 4-2-1, decat and a larini on my S1 with a huge induction kit and it sounded glorious at full chat, i don't recall it being droney on the motorway, maybe Jimbo who bought it can confirm. I have an S2 now and it was horrific on the motorway with a janspeed, broken down cat and clogged hurricane. I swapped the exhaust for a de-cat and standard 111s back box, it is far more tollerable

[Dominic]

Last winter I put the big bore 421 manifold and downpipe on the car. I run it with a sports cat and quicksilver sports back box. It's too noisy with the de-cat pipe, and as discovered at the rolling road, the de-cat pipe made little difference to the power.

I think the 421 has released a few more ponies - I am sure the car feels a bit more lively since fitting it. Also sounds a little sweeter, slightly deeper note to my ear. A big factor for me going for the 421 was that the flexi joint on the standard down pipe seemed to fail on an annual basis on my car and I was getting sick of replacing it.

The 421 was not the easiest part I have ever fitted (access and getting it in situ) - would certainly be easier to get CMC to take it on.

[DDtB]

Exhaust will give you noise and psychological horsepower increase as a result. But that's about it.

Likewise... A 421 on a 118 will do nothing noticeable I believe.

If you want more ponies then you're looking at head and cams really... 135-150 is easily achievable for not much hassle or cost and you would definitely notice a difference there... Not just noise.

Other than engine work...a CR box would make it feel a bit more frisky if you don't already have one.







Sent from my iPhone 6 using Tapatalk

[StiflerMR2]

Interesting feedback chaps!

I see the EP manifold claims 15bhp when twinned with the exhaust, I'm very dubious of that. Last winter, when speaking to Craig about power gains he advised to leave the engine alone as there was nothing wrong with it, other than it being standard.

But Dave, this is an interesting comment: "135-150 is easily achievable for not much hassle or cost " Will have to do some research and have a chat with Craig.

Keep the info coming chaps!

[Dominic]

Sounds live Davienomics at work

I reckon 150 BHP is a pretty good level of tune for the K. Leaves you with some reliability, but a wee bit extra power.

I am far from expert, but believe that the K responds well to better breathing - induction and exhaust working together. I doubt a new exhaust would give as much as 15BHP though. Just my 2p.

[DDtB]

No way you're getting 15bhp from a manifold and exhaust on a standard K I reckon.

Sabre heads kr1 spec head or equivalent and some mild cams makes a huge difference.

Not much cost is obviously a relative term. Just meant it's easy to get to that spec and great vfm. Anything more and the price/hassle jumps exponentially really.

I'd start with the exhaust as you seem to need that. Then consider head etc...before I'd waste money on a 421 personally.


Sent from my iPhone 6 using Tapatalk

[mwmackenzie]

I believe a big bore 4-2-1 will see you lose power on a standard engine, i think they say narrow bore up to 170bhp if my memory serves me right? big bore if you're flowing enough gas for above that.. Please correct me if i'm wrong

[robin]

I agree with all the above The exhaust will make you feel happy but won't actually do very much (but being happy/thinking it's quicker is worth more than actual horsepower!!)

Big bore shouldn't work on standard head/valves/cams _but_ weirder things have happened.

Cams + verniers is best - the verniers so you dial out the overlap that will otherwise cause you problems with idle and emissions; the bigger cams will give you some more torque at higher RPM, but don't go mad - crazy cams only work at high RPM (usually). There is the option of using a pair of VVC exhaust cams - if you fit those to inlet and exhaust you'll get a 135 without lifting off the head and with verniers (or just luck) your idle will still be OK. Alternately you can just use the same kind of cams from Piper/Kent/Newman and get similar results.

KR1 head is awesome upgrade but will take a while as Rog is always busy - best done with a spare casting so that you can then get CMC to swap one head for the other and keep the car mobile while Rog fettles it. A proper KR1 will give you near enough 150BHP on standard cams and standard engine management.

To be totally safe you want to boost fuel pressure a tiny tiny bit because otherwise your engine is going to run lean at full throttle. That said you can also not bother and probably never suffer and significant problems as a result - depends whether you do endurance racing or road runs really.

The Piper 4-2-1 manifold is a good idea to fit at the same time as a KR1 - future proofs it a bit and much easier to fit with the head off Probably makes little to no difference to headline power but _might_ help recover some lost torque low down.

Alternately buy somebody else's head - I think Tut has one lurking around somewhere!

Cheers,
Robin

[StiflerMR2]

Thanks very much for taking the time to write the informative post Robin, certainly a lot to think about!

I have been reading various upgrade stories on seloc today and seems as though thete are multitude of avenues to take.

The Rog head seems ideal but as you say, turn around is the issue. I'd be over the moon with 135 so I think it's best to investigate the cams and verniers route.

Again, thank you for the information, I was beginning to tie myself in knots!

[Corranga]

I recently bought a pair of vvc exhaust cams and a spindle drive for 65 quid, unfortunately I did it 3 months after having the cam belt done so haven't fitted yet, also need verniers, but it certainly seems to be a cheap way to a decent gain.

I already have a Piper 421 and a sabreheads head, which might well be a KR1, cone filter, CR box, 52mm tb and I'm in a happy place
I fitted the 421 in my mum's driveway, car on rear axle stands, in the dark, not something I'll be repeating!
CR box has been a great mod and isn't that expensive (unless you do the clutch and lightweight flywheel at the same time...), note that 421 had to come out to allow access to 2 of the gearbox bolts


Oh and give me a shout if you want that decat

Chris

[campbell]

CR box is often rated as an excellent improvement but watch the impact on drone levels if you do long mway runs.

[Corranga]

CR box is often rated as an excellent improvement but watch the impact on drone levels if you do long mway runs.

This is true. It reminds me of the mk1 mx5s we used to have. They rev a little too high at motorway speeds too.. Also, you can watch the fuel economy drop off a bit.
My car isn't used for that often though so it doesn't bother me

[mwmackenzie]

CR box is often rated as an excellent improvement but watch the impact on drone levels if you do long mway runs.

That's why you need a B6BST, Close Ratio, Torsen Diff and a long 5th. Pricey bit of kit though.....

[campbell]

Yup not economic for me