Lucky Breathes Easy

[chrisyork]

Now that Lucky, my '70 S1 3500 is nearly ready for his trp to the rolling road, I thought I'd see if there were any quick and neat mods to help his breathing. This on the principle that changing the induction side after a rolling road set up will definitely generate another visit, whereas if I change the exhaust I will probably get away with it without resetting the engine.

Now the obvious thing to do is to throw away the Rover air cleaner cylinder and elbows and substitute a pair of K&N's mounted direst to the carbs. But in the first place I think it looks very chav and also I don't like having to sit and listen to induction roar. So I had a look round to see if I could do anything with the existing air cleaner box. Eventually I found this nice pair of K&N look alikes which bolt directly in place of the existing circular element with the addition of one extra rubber sealing ring against the end cap. The extent of the mods is to drill a hole in the end of the new filter and then find a longer screw to locate into the existing bridge piece.

The filter is an MPUAF9 from http://www.streetwizeaccessories.com/index.php which you are likely to find in local accessory shops. Advantage is a huge increase in the area of filter medium available for air to get through and elimination of the right angle turns inherent in the old circular filter. And nobody can tell from the outside! I may well go on to increase the diameter of the inlet trumpet to the filter box as well.





Chris

 

[SydneyRoverP6B]

Hello Chris,

You may well find that now having fitted the K & N filters that not only does the engine breath better, but also the mixture is now on the lean side. Certainly the rolling road operator should be able to fit different needles or polish your existing needles to bring the air / fuel ratio into the correct range for the full rev range. Could I make a suggestion and say that it would be a good idea to have your new exhaust fitted prior to the visit, especially if larger diameter pipes and / or flow through mufflers are going to be fitted.

Anything that improves the air flow into - through - and out of an engine will impact directly on the air / fuel ratio.

Hope to see Lucky's power figures...

Ron.

 

[chrisyork]

Unfortunately no chance of fitting the new exhaust Ron. It's laid out to go around the upcoming ZF HP22/24 box, and won't cope with the BW35. And there's no way I'm allowing a misfire to develop into a gearbox change!

Chris

 

[chrisyork]

Well I collected Lucky from the rolling road today. Still no rear screen in him yet so a tad draughty! Lucky scored 112BHP at the rear wheels@ 4750rpm. This is significantly better than normal - they reckon a standard 10.5:1 Auto normally scores between 97 and 105BHP.

Timing was set as follows:

880 rpm 16.4 deg
1810 rpm 22.1 deg
2450 rpm 25.7 deg
3640 rpm 28.3 deg
4770 rpm 33.1 deg
5030 rpm 35.8 deg

All with vacuum advance disconnected.

Dwell angle was 27.7 deg @ 840 rpm

Needles in the HS6's were changed to KK to give CO @ 5050 rpm and full throttle of 4.5% and 5.5% @ 870 rpm idle.

To summarise the engine state:

Standard 10.5:1 with standard heads and small exhaust manifolds
Standard distributor with new points and capacitor (!) and standard coil
RPI ignition amp between distributor and coil
Magnecor plug leads
New Bosch Super4 plugs
Large intake trumpet on standard air cleaner, elements substituted by one Streetwize MPAUF9 (K&N lookalike) filter per bank






Chris

 

[SydneyRoverP6B]

Hello Chris,

Lucky's maximum rear wheel power looks very good indeed... My old 3.5 scored only 93HP @ 5000rpm, but then the engine did have almost five times the mileage covered.

Does Lucky's engine ping Chris running 16 degrees of initial timing, although the balance of the ignition timing is essentially standard. I ask because I had to run my 10.5 at TDC @ 600rpm and it still pinged... which reduced the total ignition timing thus reducing power and increasing fuel consumption. Every 10.5 I have had an opportunity to drive would ping.

My 3.5 ran Lumenition ignition (which reduced but did not eliminate pinging), Magnecor leads, foam Unifilters inside the standard airbox, standard 16C6 coil, factor fitted BBG needles. The air fuel ratio proved to be too lean especially below peak torque which without doubt contributed to the pinging.

Ron.

 

[DaveHerns]

Isn't that amazingly flat for a power curve ?

 

[SydneyRoverP6B]

DaveHerns wrote,..

Isn't that amazingly flat for a power curve ?

Hello Dave,

Lucky's power curve only covers the range from 3500rpm to 4750rpm where the peak is and then a gradual decline to 5250rpm. That represents a difference of maybe 5 or 6 HP at best across that range.

The power curve for my 3.5 across a similar interval also shows a difference of only 5 or 6 HP.

That is the beauty of a V8 engine, and not just the Rover V8. Provided the camshaft is designed to provide a broad power band, as in the case of the standard factory fitted Rover V8 camshaft which the P6B received, then the power delivery will climb rapidly and then flatten. This makes driving so much more enjoyable than having a small power band where performance is quite dull until you hit "the zone".

Average power is of far greater significance than peak power!

Ron.

 

[chrisyork]

I thought you all might like to see a picture of the new intake arrangement for Lucky.

 

[Tor]

Hi Chris,
Reading this thread with interest and considering a similar mod to my stock engine. I'm thinking of arranging a snorkel to draw cool air from the area around the valance, but how important would you say enlarging the intake funnel actually is as long as there are no substantial engine mods?

 

[SydneyRoverP6B]

When I was in the process of having my 4.6 installed, I went through numerous calculations on what would be adequate sizing for the air filter components to accomodate the needs of the new engine.

A factory standard 3.5 litre engine has an air flow rate of 260 cfm (cubic feet per minute) based on an 80% volumetric efficiency. The standard paper element air filters will flow in the order of 140 cfm per side, so a total of 280cfm. Each HS6 carburettor will flow 210 cfm, the HIF6 240 cfm. The standard Rover P6B air box with standard inlet has a flow capacity of 360 cfm. All in all the standard components will meet the requirements of a standard engine.

Changing the intake system so as to allow a better path for air to enter the engine will allow an improvement in air flow into the engine at certain engine speeds, and as such the original factory standard carburettor needles will no longer be correct,...ie the engine will run lean at certain points within the rev range. Improving air flow into an engine to aid efficiency is always a good thing, but an engine will never pull more air than what it requires.

Ron.

 

[chrisyork]

The combination of the filters and the enlarged intake trumpet seem to give a power increase of between 7 and 10 bhp at the rear wheels. This is based on a recorded 112 bhp against best previous of 105 bhp and average 100 bhp for a standard engine, all at the rear wheels. As Ron says, revised needles are required - KK.

Opinion is divided as to whether a snorkel to a cool area is an advatage. Certainly any attempt to get a ram effect by pointing the snorkel directly forward at the front of the car is a mixed blessing. The ram effect varies according to road speed, so what works well at high speed may well leave the engine running rich at lower road speeds for the same throttle and revs. I wouldn't try to get a ram effect. A better solution is probaly to concentrate on reducing underbonnet temperature generally. Lucky will ultimately be getting a bonnet (already in stock) with extract louvres up each side of the engine bay:












I've yet to decide whether to also add a NADA type centre scoop. If I did it wouldn't be directly coupled to the air intake trumpet. Its function would be solely to ensure fresh cool air got to the area above the carbs.


Chris

 

[chrisyork]

Just to add to the discussion on filters. I understand Ron's technical observations suggesting the existing air filters are up to the job. I based my decision to change to the K&N look-alikes on practical observation of the filter in my 216 EFi. The filter on this has roughly double the surface area of filter medium compared to the two filters in the standard P6 setup. But it has only a 102 bhp 1597cc engine to service. No mismatch on engine speeds either, this is the BMC "S" series engine, red lined at 6,000 and all torque on line by 2,500. I concluded from this that the P6 filters were woefully undersized. Even if Ron is technically right, the resulting lower air velocities across my revised set up should offer improved filtration and lower pressure loss.

What is certainly the case is that there has to be a significant restriction at the intake trumpet to the filter cylinder. Just visually compare the cross sectional area of the trumpet aperture to that of the inlet elbows (2 X off) and carburettor throttle apertures. I suspect this was done so as to ensure that all the water in the incoming air dropped out in the cylinder and didn't contaminate the filters (high velocity flow into large chamber with low velocity flow is how road sweepers and vacuum cleaners persuade entrained debris to drop out of flow before reaching the suction unit).

Chris

 

[Demetris]

Hi Chris,

i was expecting you to add a flare at the end of the new intake trumpet.
it is the little detail that will help the flow and will look certainly better!

Demetris

 

[chrisyork]

Quite right Demetris. It does have a flare to the end of the trumpet, just doesn't show up well in the photo.

Chris

 

[Tor]

Thanks Chris. I'm nowhere near as science literate as you guys in this regard - the snorkel idea is for cool air, primarily, as I know and have felt the difference, and I'm considering cutting off the intake piece altogether (which is quite unsightly anyway) and attaching a "snorkel" tube directly to the canister.

 

[arthuy]

Chris have you ever seen those under bonnet extractor fans they do for Land Rovers?

Fit the three NADA scoops, outside for air in and the centre for extraction with the fan.

Colin

 

[webmaster]

In terms of getting cold air in, I suspect the main problem is actually getting the hot air out, once on the move massive volumes of air are trying to force their way in through the front grill etc, but with no easy route out, the heat builds up.

Those louvres look a good idea, if not my favourite aesthetic, there must be neater ways to get the heat out.(Without allowing all the fumes to enter the heater !)

 

[The Rovering Member]

Louvres in the inner wings?

 

[KiwiRover]

How about some vent holes in the cowl panel below the windscreen, either side of the heater intake? I had heard that raising the rear of the bonnet worked wonders so a decent hole on either side should achieve the same thing. I might try this on the estate.

 

[testrider]

If you raise the back of the bonnet then you will get rid of a lot of heat but it will also be sucked into you heater box too.

It might be better if you could keep the back edge of the bonnet sealed and maybe louvre the panel either side of the heater box so that it could exhaust away from the fresh air intake.

I've always wondered why there wasn't a cold air intake for the carbs though, I'm sure the engine would run much better if there was one.