1st Gen R53 Cooper S Most liked posts in thread: Headwork - general discussion 2.0

Oops, I was thinking outside the box. This would be for non supercharged.

Still, doing a flow test with the intake manifold is the next step.

The intercooler can also be flow tested by it's self. These are critical area's of concern.

 

Thank you for all the work getting this back BlimeyCabrio. I appreciate your and Nathan’s efforts.
Matt, Thumper, and Jeff make some excellent points. What is important is the combination. Engines have been called air pumps, and it is true. To make power you need combustion. That takes air (specifically oxygen) and fuel. The limiting factor is pumping air. You can make the tailpipe black with too much fuel. Packing the cylinder with the most air involves every part from the air filter to the tip of the exhaust. The engine speed, the engine will pack the greatest amount of air is the point the engine makes peak torque. Air, and specifically in the case of a running engine, air and fuel mixed together have mass. The air fuel mixture does not stop and start instantaneously. The valves do not open to full lift instantly. Camshafts have both valves open at the same time to overcome the fact it takes time to get the air moving through the port. All the pipes (intake manifolds, cylinder head ports, exhaust headers) have internal dimensions. When the piston falls on the intake stroke it displaces a certain amount of volume. Depending on the speed of the engine you get volume over time. I will leave the blower out, but it is just like a piston except it pushes. The point is the gas will move through the pipes at a specific speed given a specific engine speed. The camshaft uses the opening and closing points of the valves to optimize starting and stopping the movement of air in the pipes to affect the filling of the cylinder. It uses the rate of change in valve lift to help this process. Remember that the piston stops at the top and bottom of each cycle, therefore the piston is moving at different speeds as it descends the cylinder. The affect is the amount of vacuum created is constantly changing. This can get real complicated real fast. The head, intake, and exhaust need to have their internal dimensions shaped so the air can move without restriction. Bigger pipes are not better in every case. It turns out that engines will pack the most air when the velocity or speed through the pipes is at a specific speed. Make the pipe bigger and the speed that the engine will make peak torque will increase. Remember the mass thing from above. The air will keep flowing even though the piston has started to go back up the cylinder. The best flowing pipe would not have any turns and would not have a valve in the way. Car engines are designed to allow the hoods (bonnets) to close, and all engines require valves. The point is the pipes have a lot of restrictions. Production parts have manufacturing limitations for cost. The ideal port or pipe would be the smallest cross section without creating turbulence and that created the ideal gas speed at whatever speed you wanted the torque peak. A larger than ideal port with turbulence might create peak torque at the same engine speed as the smaller port, but the performance below peak torque would not be as good.
Matt is correct there are plenty of books on this, and I am starting to write one, so I will stop.

 

Are all stainless valves the same or which ones are better?

For the Mini Cooper they offer standard, .50 mm, 1.0mm, 1.25mm, and 1.50mm oversize valves. Is larger better than standard? depends

Then there is hollow stems, undercut stems, sodium filled, nitried coatings?

Each manufacture determines the under head radius, or tulip, some are flatter, some a short radius, which are better?

Valve angles, is the rule of thumb the best? 30 / 45/ 60?

 

I'll be the bad guy...

To the average enthusiast.. the average get on the track once in a while..
This post is interesting.. It has discussed the HOW ( to a degree) and the WHY ( to a degree). And to the average guy, can start to get into over load!
How about the NEED??

Does my MINI NEED the sodium Valves?? or Hollow stem ?
Does my MINI need the Oversize Valve, to what size?? +.5mm +.15mm ??
Does my MINI need 96-112-114 cc intake runners..

All this thread is cool to show the knowledge is out there.......... the Parts are out there............... The Heads are out there!! But what is the use , IF we dont discuss the purpose of what is out there??

There will still be the guy that will buy a $2200.00-$3000.00 HEAD, and be disappointed!! In the performance... he will , however be able to brag all the "whiz-bang" parts he has!! YES?? But once he pulls out on the street or the track... it will be apparent that he "Over Bought".

I am of the "School" ( Old) that we help to evaluate and then suggest the Head mod to the customer!! IF He decides to go BIGGER or smaller.. then it is HIS choice.. BUT, How does HE KNOW?? Form posts like these, and the Head mfg's suggestions..yes? Testimonies from others!! I try to sell by APPLICATION, not bottom line!

As Blimey said earlier.... I understand most things are a matter of trade-off decisions - but it also seems that some relatively "mild" reworked heads actually seem better at just about everything - better or equal fuel economy, better or equal low-end torque, no change to idle manners, and significant mid-range to high-end torque gains.

I feel this is the answer.... IF you are a RACING Car and Driver.. then you are in the small 10% and all the "whiz-bang" Trick procedures are yours!! If you are with the rest of the 90%.. it is nice to know, but what works on OUR cars is closer to reality!! There are times when the High Dollar Head ISNT right for our car..!! Right Blimey??

Just me......................................

Thumper

 

I do when I'm on my 50 CC scooter

Mark

 

:cryin:

 

:yesnod:

send me your engine when I am finish you would not be able to make this comment. :lol:

 

There is a big bore kit, kicks it up to 65 CC

Mark

 

Good discussion....I would probably say, for most people, this would be the last item to consider, a modified cylinder head. Usually most people start off with alot of easy bolt on's, looking for small amounts of easy horsepower.

But for those that have a interest in this direction, you can still have a smooth idle with a substantial horsepower increase and a good torque curve.

We have seen some good power increase's with a stock camshaft, and a modified cylinder head, stock valves, and keeping the same max rpm's. Add the underdriven pulley, hedder with the cat back exhaust and a tune.

All things considered.

 

Ya but see I was factory Honda trained (Elsinore days)in 2 stroke barrel modifications....:ihih:
ring.. ding... ding... ding

 

Porting and a pipe will make a two stroke fly

 

and piston trimming