K-Series R300 4-1 and silencer

[Kal-El]

I have a Roadsport 140 which is having a few upgrades done atm. One of which is an R300 4-1 system and silencer. Is this a worthwhile upgrade over std if I am going to have cams and throttle bodies or would I be better off waiting and getting an EBD/Tech Craft system after I've done the other work? I am aiming for 165 - 175 bhp...

Thanks

P

[DVandrews]

A 4-1 is not really suitable for regular driving, it kills the mid range and gives a boost at the very top of the RPM range, I would invest in a 4-2-1 such as that produced by Powerspeed, this will give a much better torque profile, just ask Jor-El.

Dave

[IBDAET]

Ny car with a 4:1 is fine at all speeds. Mad fast or gentle cruising.

[Kal-El]

Hi Dave (or is that Jonathan Kent?)

Would I be worse off than maintaining the stock Caterham manifold and silencer? How badly would it actually affect the mid range?

[Kal-El]

Ok I've decided to ditch the R300 4-1 cat and silencer. I'll talk to EBD about a 4-2-1 and order a tech craft silencer. What sizes should I go for?

Spec will be:

1800cc
VVC head
1320 or BP285 cams
DTH throttle bodies

Thanks

Piers

[DVandrews]

IBDAET said:

Ny car with a 4:1 is fine at all speeds. Mad fast or gentle cruising.

Based on a sample of one with no empirical testing against the alternatives.

I'd bet my testicles that a 4-2-1 would dramatically improve the mid range. I have done some extensive back to back testing and a change from a 4-1 to a 4-2-1 on one 1800 K gained 18lbft in the midrange and an average of 11lbft over a 3500 RPM spread. It lost 2BHP over the last 600RPM. I know which I would rather have.

Dave

[IBDAET]

Ah, but any more torque and I'd need a stupid clutch. As it is a std HD organic is putting up with 169lb/ft and 258bhp. That's plenty fast enough to test my driving ability to the limit.

[DVandrews]

You may not see more *peak* torque, you will just see it delivered over a much wider rev band.

Dave

[BigCol]

DCL's Duratech rebuild thread concluded the same - that the torque curve with a 4-2-1 is flatter/better than a 4-1

[Mellow7]

My car has the same R300/R500 system - I know a 4-2-1 will give better mid range torque, Dave told me so when he worked his magic on the engine, however Emerald were able to smooth out the torque curve so that it wasn't too bad in the end. On the road, the acceleration is very linear and I am sure any loss in torque at certain revs is offset with a kick in power - one at 4500 and another at 6500! Here's the plots from my Emerald session (albeit done on old plugs/filter and a slipping clutch - it slipped from the day I collected the car with "just" 140 bhp (although when Dave checked the timing he reckoned on more like 125 bhp). Note how the torque falls away without the airbox fitted, but the power broke the 200 barrier which was a psychological gain.

The main reason I went for the 4-1 system was to make the car standard "Caterham" in appearance, and I preferred the look of it.

[IBDAET]

That's a very interesting plot. You would get the HP gain with an airbox (asuming it grabs a good cold air feed) but only at higher speed, and only on the road, not the rollers. This is what we found with the "upturned ocean liner" airboxes I made. Massively better acceleration above 120nph. On the rollers these dropped the output 20-30bhp over running with no airbox.

I'm not saying anything negative to a 4:2:1 system - the car below had one, but what I am saying is that the R300 system is good. You could just replace the cat section with a 4:2:1 collector - Hayward and Scott could make such a thing at a sensible price.

Edited by IBDAET on Thursday 10th July 10:29

[DVandrews]

The R300 system is good in terms of primary length and size, but the primaries are arranged so that 1&4 and 2&3 are diagonally positioned making it impossible to make a 4-2-1 section.

If you look at the torque curve you will see a dip from 4500 to 7000, this has been minimised but is still substantial, a 4-2-1 will make this area bulge upwards.

Dave

[Mellow7]

"Massively better acceleration above 120nph."

...I bet it isn't with a windscreen fitted. My airbox is the Bernard Scouse version for Jenvey's. The "no airbox" plot was just that, air straight into the throttle bodies. The workshop was quite warm too...

[Toaster]

IBDAET said:

Ny car with a 4:1 is fine at all speeds. Mad fast or gentle cruising.

+1 (so a sample of 2)

Not bothered if its emperially tested, my 7 is just Bonkers in my highly subjective view

All setups are a compromise some more than others

[Mellow7]

DVandrews said:

The R300 system is good in terms of primary length and size, but the primaries are arranged so that 1&4 and 2&3 are diagonally positioned making it impossible to make a 4-2-1 section.

If you look at the torque curve you will see a dip from 4500 to 7000, this has been minimised but is still substantial, a 4-2-1 will make this area bulge upwards.

Dave

I don't think I could cope with more of an "upward bulge" - not at my age anyway My primary focus is now my "advisory" wheel hub noise which can't be adding to the speed - and then the brakes of course...

I only do 60mph these days anyway 'cos of all the flies...

[IBDAET]

You need one of these in the boot:

http://www.amazon.co.uk/Autoglym-AG-185003-500ml-G...

Incredible stuff! Essential for any long journey.

[IBDAET]

Mellow7 said:

"Massively better acceleration above 120mph."

...I bet it isn't with a windscreen fitted. My airbox is the Bernard Scouse version for Jenvey's. The "no airbox" plot was just that, air straight into the throttle bodies. The workshop was quite warm too...

Yes, just an aeroscreen.

[Kal-El]

Can anyone give me an idea of what size primaries, secondaries and system I should order, for an 1800 making 180-200 bhp?

I am guessing a 2.25" system is about right? When would this become a restriction?

Thanks

P

[simonpa]

IBDAET said:

That's a very interesting plot. You would get the HP gain with an airbox (asuming it grabs a good cold air feed) but only at higher speed, and only on the road, not the rollers. This is what we found with the "upturned ocean liner" airboxes I made. Massively better acceleration above 120nph. On the rollers these dropped the output 20-30bhp over running with no airbox.

I'm not saying anything negative to a 4:2:1 system - the car below had one, but what I am saying is that the R300 system is good. You could just replace the cat section with a 4:2:1 collector - Hayward and Scott could make such a thing at a sensible price.

Edited by IBDAET on Thursday 10th July 10:29

I thought ram-air systems went out with the 70s?

Edited by simonpa on Friday 11th July 16:49

[PurpleMeanie]

Cold laminar airflow has never been a bad thing.