Cam choice for supercharged engine.
Turbo Mini Forums

I am looking for some advice on what cam to chose for my, to be built, engine.

Basic specs will be:
- 1293
- MSE6 head (with 28cc chambers)
- 1.3:1 rockers
- M45 SC
- intercooler
- Wet manifold injection.
- Boost about 10psi

Currently I have a NA MG metro cam but running a supercharger allows me to use a hotter cam.
The options I have in my head:
- SW5
- 276
- 286
- 274 SP (scatter)

I know some have very good results with the scatter cams so was leaning towards the 274 SP also to reduce charge robbing however is that worth 200quid when you can get a 276 and 286 for a lot less.

For a NA engine I would have probably chosen the SW5 over a 286 as I am not the kind that revs to 7000rpm but a supercharged engine would probably work well with a 286 without needing to rev it (?).

Also, will there be a noticable difference between a 276 and SW5 in a supercharged engine?

I would appreciate your thoughts about the above (I hope it makes sense).
Thanks, Han

Edit: added planned boost level

Edited by Yo-Han on 9th Nov, 2011.

Dazed and Confused....

I use a 276 with mine and stuart at VMAX recons there are much better cams to use. He just so happens to supply them but one day I may just get round to trying one

Thanks for your reply; did he by any chance elaborate on what cam would be better?

Dazed and Confused....

I am not that knowledgable about cams but saw that the kent cams have a bit more exhaust duration which I thought would be beneficial in a forced induction application.

Someone offered me a 286 cam but I am affraid that that will be too wild for my engine.

Can someone please comment?

Dazed and Confused....

a 286 is probably pretty good, but getting to the top end of being nice....

Ok, thanks Joe.
I guess I should give it a try
Thanks for your reply

Dazed and Confused....

The vmax site has a little bit of info on what cam works best, they give a spec of 112 lca I think and state it works well?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

got a link to that graham?

Yes i moved to the darkside

Instagram @jdm_brett

More importantly, what sort of idle and low end would you like ?

Regardless of any of those cams, making power with a blower is easy.

And as for rpm ability my turbocharged setup with an SW5 will pull 7500rpm with ease. So I imagine it will have that same ability with the blower, unless the blower itself is become inefficient up around there.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

http://www.vmaxscart.co.uk/

It's on his home page in the light blue writing. The website is not very easy on the eye. Extract below

What can be supercharged?
 
    Most A series can handle a bit more power , If  adding a supercharger to your current engine It must be in good condtion to handle the extra power . If you are building and engine decide on the power you want  to achieve and what use you want out of it , eg motorways , track days occasional fun etc . With the increased torque available you can usually pull a taller diff ratio without loosing any accelleration time . Straight cut gearboxes with close ratios are not ideal for road use as the gears are generally close ratios, better for road use with high torque figures are 'boxes with wider ratios. ultimately straight cut gears do handle more power. A 4 pin diff, minispares 2 core comp radiator , suitable fuel supply  are all essential . Forged pistons are definately  recomended on engines of 150bhp plus . keep Bore sizes small to increase reliabillty. Wrap manifolds to reduce heat transfer and keep underbonnet temps lower.
 Fuel injecting over carb /dizzy.  carburettor set ups mostly produce the same power  as the same size throttle body , gains with injection are being able to acurately measure fuel and time the ignition without relying on a mechanical input. Major gains are seen in  fuel economy and throttle proportions , these are  more precise /easier to adjust for , making it smoother  to drive . If you are using the carb /dizzy then always use a vacuum type distributor  to give the variable timing a road use engine requires for varying loads and conditions . 
 Cam shaft choices : aim for something milder than you would use in a non supercharged engine as the charger extends the range above and below its normal specification , wider lobe center angle is recomended to reduce fuel being wasted on overlap ,112 lca seems to work well . Supercharging works with everthing from standard to race profiles  , but in varying degrees. 
  
 

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Thanks for the reactions guys.

Nice link Graham, cheers.
A 286 106 lca seems for off that recommended 112 lca...

To be honest this car will not be for daily use; more of a weekend toy.
Little rough idle is not much of an issue.
I was thinking low end would not be so bad with a 286 and if you floor it the SC will compensate.... (?)

Han

Dazed and Confused....

I have a VMax 274 for my supercharged engine

You could give Piper/Kent a call and tell them what you are up to. I reckon they would brew you up something suitable.

Plus then you can be a git and say you are running a "Top Secret" cam! lol

If something is worth doing, it's worth doing half of.

I sent Kent cams an email, this was the reply I got:

Dear Sir,

Thank you for your recent E-mail, we already offer the 500 profile for a turbo charged engine and I’ve no reason to think it wouldn’t work as well in a SC engine. The MD286 has way too much overlap in my opinion.

Dazed and Confused....

Ok here is the trouble, most people assume that you need the sam characteristics for turbo and supercharged engines, this just isn't the case,

on turbo lumps there is usually more pressure in the exhaust than in the inlet which (ignoring inertial effects) tends to make cams more... cammy. so for turbos you want short ish durations and limited overlap (asumng your not trying to do somthing clever)

on charged engines there is not the restriction in the exhaust due to the turbine, and in fact you can get scavenging as per a N/A engine, on the inlet side you will also get a siutuation akin to an N/A engine, but as you suspect when you nail it the charger will move air get stuff flowing in the right direction and get the engine on cam, however at part throttle somthing like a 286 might be a bit wank low down just as in a N/A lump. also with a narrow LCA on a charger you might find that the charger blows som mixture out of the exhaust hurting mpg, this is why V max grinds the wide LCA cams.

the 286 will work but you will need to rev it, probably good for 8k+, worth using if you have one to hand, and its just a "fun" car

The Vmax cams are well worth a look as IIRC they are quite cheap,

another cam worth trying is the RE13T (112 deg LCA) from keith calver, its short on seat timing (264 deg In & exh) but it gets the valves open VERY quick,

Thanks Joe, for confirming my thoughts about the difference between turbo and SC cams.
When I got that email from Kent cams I thought the answer was not quite correct hence putting up a post here.

A bit of mid end would be nice.
I have sent a mail to both Piper and Vmax as they don't have info available on their websites.

Will let you know what comes out of it.

Dazed and Confused....

Just bang a SW5 in it. It'll be sweet.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I got the info from Vmax and Piper;

Stuart uses the SW5 for passing emissions.
When emissions are not an issue (like my car) this is the spec of the other cam he has; a cam with 270/260 duration with 112 lobe separation which should give a little more power.
At a price of 120 quid!

I asked Piper for the RE13T equivalent cam.
They answered they had done a camshaft for a customer with a very similar setup, basically a 285 profile on the inlet and the 270 on the exhaust with lca of 107.5....
Priced 175 quid.

Having this info I think I will go with the Vmax cam, seems Stuart thought this through and pricing is very sensible...

Dazed and Confused....

good choice,

Mr Gurr has done more with the A series and chargersthan anyone.

This might be a rare instance when importing a part from America could be the best choice. The Vizard/Anton crew sell a cam specifically for supercharged A series engines:

http://aptfast.com/ListItems/MainCategory/Camshafts.aspx

I have dynoed several supercharged A series, mostly in MG Midget/AH Sprite cars. You do not want a long duration cam because the late intake closing is bleeding off the compression you are trying to build with the supercharger.

$359 = about £240 plus shipping and tax. I'd rather get one from VMax for about £100 -£120....

To pay or not to pay, that is the question. Whether tis nobler to add the additional horsepower, and to suffer the slings and arrows of outrageous prices in pursuit of the all mighty dream, more power! Aye, there is the rub....

Seriously, you have to ask how much you want to pay for the extra power. If the cam can get you 10% more torque, then how much is it worth? Not saying you need to buy this cam, but it might be worth sending an email to APT and ask what kind of power increase you might get over the cam you have selected. Vizard/Anton put some real research into designing a cam for this application, it's probably as cost effective as everything else you are spending money on.

It will probably be a very good cam, but $359 is pretty steep.
I am not after max power, just resonable power at reasonable expenses (...) is good enough.
Thanks for your reaction though.

Dazed and Confused....

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

With high-lift short duration cams, damage to the cam lobes is a very real probability - look at the issues Swiftune have had with the reground SW5s...

The APT cams are all supplied with oil-fed lobes, which is certainly worth a few extra quid in my book !

Metric is for people who can't do fractions.