Duratec porting, a few thoughts.

[AMMO]

Let's go back to basics. What is written below can be the basis for some discussions. The reason I have gone back to quite an old post is because since then quite a few engines have been built and many dyno tests have been done and quite a few facts discovered. When I say dyno I mean the rolling road at Emerald. Dyno is shorter than writing rolling road every time. The flow bench tests were all done on a Superflow 600 and all the dyno graphs, unless otherwise stated, are from Emerald. The following was posted quite a few years ago and lifted word for word with no changes from the original post:

 

Posted - 23 December 2003 18:36

 

I finally managed to fire up the new Superflow 600 in anger for the first time today at 3 pm. Just before the workshop closes down until January.

 

I did some quick and dirty testing on a Duratec head which has cylinder #1 left standard. The other cylinders have been modified in different ways. I have left the head on the bench and will do some more detailed testing in the New Year. All testing was done at 25” of water. To convert to 10” divide by 1.58. I did some testing at 10” and at 25” to check that the conversion is correct.

 

The exhaust ports have also been modified but I will have to wait until later to test them.

 

Cylinder #1 was tested with 11 mm of lift using a Kent cam at full lift as a valve lifter with a Raceline direct to head throttle body and 90 mm trumpet. Normally I check at 1 mm increments and over-lift to see if there is any benefit in using a higher lift cam. Not enough time. The test was on a completely standard intake ports with no mods. The result was 213.2 cfm. Enough flow for 232 bhp. This is in theory with the correct cams and exhaust. With short 260 / 270 degree road cams the 2 litre has been dyno tested at around 210 / 220 bhp.

 

Cylinder #2 as above plus a very small mod to the short side of the port just before the seat. The stock port has a tumble feature which I removed. The result was 226 cfm / 246 bhp potential.

 

Cylinder #3 as above but with mods to the throat. 231.2 cfm / 251 bhp potential.

 

Cylinder #4 as above but has has the ports cleaned up but not enlarged by much. 237. 2 cfm / 258 bhp potential. This is equivalent to 150 cfm at 10” which is what I predicted months ago the head was capable of doing without too much work.

 

It is possible to get more if you are willing to put the work in. I'm aiming for a mere 220 bhp for my own engine. Probably more than I know what to do with.

 

I am very happy with the results. To achieve the same results with a lesser head would take more than the cost of a Duratec donor engine. Some heads will never achieve this because they just cannot accomodate the valve sizes.

 

I am convinced that the Duratec will become the engine to have. There is nothing else out there that I have seen that can give these sort of cfm figures with so little work.

 

AMMO

 

Back to today. The above was written when very few Duratecs had found their way into Caterhams. There was a lot of resistance to these engines by the K-Series and VX crowd. Talk about reliability and if they really had the potential to make the 300 bhp I claimed. I joked at the time that these engines would be embraced once they were discontinued. I have heard a rumour that this will be next year.

 

The above flowbench figures are for the early 2 litre / 2.3 Ranger head which is inferior to the late head (but still bloody good). Some people call the late head a high port head. The inlet at the gasket face is the same as on the early head. For me a high port head is a head that has had the induction angle changed to a higher, steeper angle moving the port entry higher. I looked at doing this but it required too much work. I will refer to the heads as early and late. Late heads came in around 2004.

 

To get the ball rolling Ben Willis' 210 bhp engine fitted to had work done only to the throats, was fitted with DTEC 10 260 degree cams and made 217bhp. Graph here Some years later Ben brought his car to one of the dyno events held at Emerald and when re-tested it made 226 bhp. 9 bhp more that when it was new. I always say the engines make around 5 bhp after they have been run in but in this case it made more than expected. I don't have the graph for this but maybe Ben still has.

 

This is far off from the 246 bhp predicted but than nobody has had the balls to stick 280 degree or perhaps higher duration cams on an early head with hardly any work and see what happens. The next step is the 220 bhp engine and by that time I go for the full porting job and 270 degree cams. Graph here

 

I did build ten 210 bhp spec engines for Elises. Some have done some pretty high mileages by now. When we built a couple of engines with 260 degree cams and full porting jobs as opposed to just working on the throats they still made the same power. In other words improving the head made no improvement to the power. The cam was holding the engine back.

 

Virtually the same head as the 220 bhp engine but with maybe a bit more attention paid to the porting and 48mm throttle bodies instead of 45mm does this here 260 bhp. You could make the same power on 45's but the 48's were fitted as they left the option open to make more power later.

 

If I remember correctly a few weeks after these tests were done Pete McEwen from Raceline sent me a late head to test. We got 158 cfm @ 10" straight out of the box. With no porting this is as good as a ported early head. Again to my knowledge nobody has tested this head on an engine with decent cams and throttle bodies but there is no reason to believe it wouldn't make 260 bhp out of the box. If money and time were no object I would try it.

 

Once ported the late head with my own cams and throttle bodies it does this on a 2 litre. http://www.dyno-plot.co.uk/dyno/dynoplot/id%3D535%26sort%3Drec%26but_sea%3Dqs%26sea_simple%3Draceco/Westfield-RACECO-UK.htm

 

If you then go to town, put bigger valves in and increase the capacity to 2.2 you have this here

 

Once development is done on the 2 litre I am hoping to see 295 / 300 bhp. I can't see vast increases in torque from this engine and the extra power will come from higher rpm.

 

The head on the Duratec is very good as standard, especially the late head that has a much better port shape. Don't dismiss the early head if 260 bhp or lower is your target.

 

The first 300 bhp engine I built had an early head with 1mm larger valves. It was 2445cc though. here

 

The development of the engine wasn't easy. The early version made only 276bhp and caused many sleepless nights. Lots of new parts had to be made.

 

The other thing to keep into account is the size of the throttle body. I have figures of ported heads with different throttle bodies on. In many cases the throttle body can add a restriction and decrease the airflow. The throttle body, port and airflow have to be in proportion with each other. If big power is required a 54mm throttle body with the stock 35mm valve sizes is about right. On a bigger valve head the 54mm bodies restrict the flow so an even larger size would work.

 

At the risk of repeating myself I have been using these size throttle bodies on twin and single cylinder motorcycle engines since the mid 90s. It is nothing new. The stock throttle body size for a 1993 Moto Guzzi Daytona is 50mm on a road bike. A race Ducati had 60mm and a Race Honda a 65mm body per cylinder.

 

The work I did with Suzuki on four cylinder engines in the 90s was mainly to do with the cylinder head and airflow. The 750 cc engine had 45mm bodies whilst the 1000cc engine had 50mm.*

 

The thing about using smaller than required throttle bodies on car engines is a throwback to carburettor engines and the requirement to have a Venturi to drag the fuel out of the float bowl. With fuel injection everything changed and we can run a much better throttle body / port shape with higher flow than before. I did some work on old racing Porsche 911S and 911Ts. The port size on the carburettor heads were much smaller than those fitted with mechanical fuel injection.

 

There is no need to run a bigger throttle body than you need to make the power you want although it seems that it not detrimental if you do. One negative effect is that low throttle opening control suffers as there is a rush of air when you open the throttle. This can be controlled with a suitable linkage although on a race engine that is running a between 5,000 and 9,000 rpm it is not required. There is no point in running a bigger port, or valve size if the engine and target horsepower does not require it.

 

All components, cylinder head, cams, throttle bodies and exhaust have to work in harmony to produce the best result.

 

* Edited to add a point about the Suzukis. When the throttle bodies were added to the Suzuki heads the head did not "see" them on the flowbench. In other words the flow of the bare head with a radiused inlet was not decreased by the addition of the throttle body. Every modified Duratec head I have tested has had its flow reduced when a throttle body has been fitted. I have tested quite a few different size bodies as well as my own 54mm bodies. The 54s outflow everything else, but when added to the head caused a 1.5% reduction in flow. There is just enough room to bore these bodies to 56mm but with the 2 litre wanting to go to 10,000 rpm as it is I can't see any point at the moment. Again it is not the airflow that is stopping the engine making power, it is the rpm.

 

 

 

 

Edited by - Ammo on 11 Feb 2013 12:48:07

[myothercarsa2cv]

Thanks AMMO Another corker 😶‍🌫️

 

Is there any way of mathematically determining what flow rates, valve size and throttle body size you need for a given engine / target power? Or do you just make an educated guess and see what works?

 

You say there's not much potential for more torque on the 300bhp Duratec - what's the limiting factor? Is it just that you can't physically get any more fuel and air in to the cylinders without forcing it? Or the stroke? Something else?

 

Sorry for all the questions 😶‍🌫️

[AMMO]

Hi 2CV

 

I suppose the very first thing I always look at to determine the potential of an engine when someone brings me one for assessment is the intake valve area. From the area with the aid of some simple calculations you can make predictions of the power potential of the engine.

 

I would say that producing power from an engine is a combination of empirical testing (flow benches, dynos and race tracks), educated guess work based on past experience and a creative mind. The creative mind is an important aspect in my view. Without this no innovation is possible. We would still be running pushrod engines with two valves per cylinder and carburettors without innovation.

 

In the early days I've was very fortunate to have mixed with some very clever people and have learnt a lot from them. It is a source of great pride that now some of these people call me up to ask my opinion. Once upon a time it was the other way around. One of them called me last night. He was building engines that would finish 24 hour endurance races when I was still learning. The person in question has lots of experience but is still asking himself questions and looking for answers.

 

I was fortunate that I did a year in 24 hour Endurance as one season of 24 hour racing is like doing ten seasons of normal racing. You learn a lot. I quit my job as a workshop manager to do it and started my own business as an engine tuner. What was to become Raceco was started on February the 14th 1986. Another anniversary coming up in a couple of days.

 

To give you an idea of how far we have come my first dyno session was in December 1985. The FZ Yamaha 750 we were testing on the Schenck at Mistral Engineering in Stoke Newington made 104bhp. Roll things forward to 1998 and the Suzuki 750 I had some involvement in made 162bhp at 15,000 rpm. From 138 bhp per litre to 216 bhp. Makes the 150 bhp per litre of the Duratec seem quite tame. The parts alone to update the road Suzuki engine into a race engine cost £85,000.00 at the time. Some of the parts I supplied to Crescent / Rizla Suzuki got sent of to Japan and put into the World Superbike kits by Suzuki. It was a fun time and like now I spent a lot of time awake at night thinking about things.

 

Another thing that springs to mind is that when we were racing against factory Ducatis and watching Superbike races is that every year new bits would come out. Ducati had new exhaust systems, larger throttle bodies with dual injectors, fuel pumps. Development never stopped, it was never over, nobody ever said "That's it, that's as far as we can go". There comes a time with an engine, or cylinder head for that matter, that you say that it is not worth continuing due to the law of diminishing returns. Time to move onto something else. The FZ Yamaha was replaced by a Honda RC30. The Guzzi 2 valve carburettor bike by a 4 valve fuel injected one.

 

In the case of the Duratec we still haven't reached the stage where development is complete or a better N/A engine has turned up.

 

When it comes to tuning there are so many variables that sometimes my head swims with all the possibilities. The person that thinks that tuning engines is simple maybe hasn't thought about all the variables. I spent eleven years of my life at the side of racetracks trying to make things go faster. I built my first race engine in 1984. After almost 30 years I know almost bugger all. I haven't even started to scratch the surface. At the moment I am somewhere in the ball park with the Duratec head but all the questions I have been asking myself still haven't been answered. It works well in conjunction with the cams and throttle bodies I designed but I have only designed three cams for this engine. There are still possibilities to explore there.

 

If there was 10K available I would undertake some serious exhaust development. What we are running now is made to my specification but based on an educated guess based on past experience. It is good enough but far from perfect. Apart from the ports, the cams and the throttle bodies it is the exhaust that fills and empties the cylinder.

 

I don't even know if I answered your original question 2CV. I suppose the limiting factor to making power is how many new bits you can afford to design and test. The limiting factor is money. That is why your 2CV engine is making only 30bhp and my 2 litre Duratec only 280 bhp. If more money was available we would be further down the line.

 

Edited to add a link to the 24 Hour Endurance bike racing team I was involved with in 1986 for those who are interested. here

 

 

 

Edited by - AMMO on 12 Feb 2013 09:25:00

[elie boone]

About the 2CV, it would get interesting if a 4 valve head could be adapted to the cilinder, BMW maybe ?

[myothercarsa2cv]

Thanks Ammo!

 

Elie, I thought the 4-valve boxers were twin cam rather than pushrod? Probably a bit of a pain to fit. Twin spark plugs is not uncommon though. Found these guys the other day. Bit out of budget, but it looks like a 10k rpm 2CV is achievable for non-racers!

[elie boone]

No intention to hyjack but i found a exploded vieuw of a boxer and it has the cam in the head but it still uses rockers to operate the valves.

[AMMO]

Looks like the Belgian guys have done a lot of the work on the 2CV. Their steel one piece crank is similar to what I had in mind. It would be cheaper to buy their crank than to develop your own.

 

Something I noticed from the video here it looks like they are running a 2 into 1 into two similar to what I ran on my race Guzzi. If you watch the dyno run you can see that the left hand header is getting hotter than the right hand one which indicates that it is running leaner.

 

When you run an exhaust like this on a V-Twin the exhaust scavenges one cylinder and interferes with the other at certain rpm. As the plug chops indicated that the left cylinder was running leaner I flow tested all the injectors I had and fitted one with higher flow to the left cylinder. This evened things out and was a good temporary solution. In the end we ran a lambda probe in each exhaust header and data logged the fuelling. From the lambda traces you could see one cylinder going rich and the other lean. Even with the old Weber Marelli P8 ECU we could re-program each cylinder individually to solve the problem. This was 1996.

 

I haven't even got close to doing anything similar with a 4 cylinder engine yet. I have always wondered what number 4 cylinder is doing on a Duratec with its tortuous exhaust port. I have thermocouples I could put in the headers and find out but it would be opening a can of worms I don't want to open. Individual cylinder optimization is something you do when you have already done everything else and we are not even close to that yet.

 

Even with a humble 2CV you could get carried away if you have the budget to do it. Depends how obsessed you are.

 

In the 80s I quit my job, made myself 22K overdrawn in the bank, sold both my road motorcycles, juggled credit cards, using one to pay of the other and re-mortgaged my house to go racing an air-cooled V-Twin with shaft drive. Probably the stupidest bike in the world to race. I worked on the principle that I would never have the money to do it or if I eventually did I would be too old to go gallavanting around. It eventually came good when we got factory sponsored. If I had the chance to do it again I would not change a thing.

 

The problem you have 2CV is that you are just not obsessed enough. 😬

[myothercarsa2cv]

Or not brave enough!

 

About the exhaust scavenging - is there not a better exhaust design to prevent it interfering with one cylinder? Or is adjusting the fuelling the best way?

[AMMO]

The consensus of opinion on that type of collector an a V-Twin is that the advantages outweigh the disadvantages. Things that would affect the running of each individual cylinder could be the firing order, one cylinder will be doing more work than the other, the crank rotation and how much oil is thrown into each bore. V-Twins get better lubrication to the left hand bore. Don't know if this is the same on boxer twins.

 

In the very old days if a Guzzi V-Twin did have a piston part seize in the bore or pick up it was usually the right hand side. I've heard of V8s being the same. Something that stuck in my mind a long time ago is that there was a Messerschmitt V8 supercharged fighter plane engine that ran different compression ratios on each bank. 8.5:1 on the left and 8:1 on the right. I always wondered if this was to stop the right hand seizing or if it was for some other reason.

 

In the case of the 2CV it could be that the collector wasn't made exactly as it could be because of packaging constraints. Maybe the silencer has to go to either one side or the other of the engine. I think the collector needs to be more symmetrical and more of and X shape where it joins. If you look at the right hand pipe after the collector it looks hotter than the left hand one. The hot gasses are following the path of least resistance. I would maybe have joined them centrally over the top of the engine and had one pipe go off to the right and one to the left rather than both to the left. That would have perhaps made a some difference.

 

As an alternative for a boxer twin you you could run two completely separate tuned length headers and silencers with no connection between them or with a balance pipe at the right point to be determined. The latter should give more torque than the individual pipes. I have run both configurations. However, the guys that are tuning the 2CV seem to know a what they are doing and if they have opted for a 2-1-2 system I reckon it must be for a reason. I wonder if it has two silencers?

 

 

[myothercarsa2cv]

Thanks Ammo. I ran twin pipes on the 2CV for a while with a modified crossbox (the original system has equal length headers, a cylinderical cross box, and an exit on the LHS) which had an extra exit on the RHS. It sounded good 😬 I don't know if it went much better though! It didn't last long; it fell victim to a speed bump that I took a little too enthusiastically, and getting these things made for you isn't that cheap, so I went back to the original. If you look at the 2CV race cars, every single one has a different exhaust design! I guess any gains are so minuscule that most don't bother testing...

Anyway, sorry to take it off topic! Back to the Duratec... 😶‍🌫️

[7 wonders of the world]

I've heard of V8s being the same. Something that stuck in my mind a long time ago is that there was a Messerschmitt V8 supercharged fighter plane engine that ran different compression ratios on each bank. 8.5:1 on the left and 8:1 on the right. I always wondered if this was to stop the right hand seizing or if it was for some other reason.

 

Probably just had the block decked HERE

 

 

Edited by - 7 wonders of the world on 16 Feb 2013 07:39:58

[AMMO]

7 Wonders, link doesn't work for me. Can you give it another go please?

 

Back to Duratec porting.

 

The other night I was looking at dyno graphs and I found one that was not from Emerald but from the two Steves at Track'n'Road. The customer's name was on it which jogged my memory. It was the graph of a Duratec R500 that I had rebuilt after it had dropped a valve and made a bit of a mess of the head. Sometimes when an engine drops a valve the head can be brought back from the dead by welding, fitting new seats and fettling. I've done a few in the past but in this case the spark plug and spark plug hole had taken a bit of a battering and as there is a coolant passage around the plug (how many of you knew that?) I opted to start with a new head.

 

Rather than buy a CNC head (fitted as standard to the R500) to save money and time I opted to port by hand, something I advocate on a Duratec with stock size valves as the original ports are pretty close to being optimal out of the box and are very close to the proportions and dimensions I have been using for a very long time. There is a good story about this but I don't want to go off at too much of a tangent.

 

The dyno sheet is dated 2011 so it was probably one of the last engines I built. The result looked good but I had nothing to compare it to. I called the two Steves, had a chat about this and that and asked if I could have a graph from a standard R500. Steve Greenauld emailed me the information at about 3 am and was surprised when I sent him a thank you note in reply. Seems like I'm not the only one who is up in the middle of the night!

 

The graphs show that the stock R500 made 259 bhp @ 8,500 and 170 ft.lb of torque and the re-built engine made 269 bhp also @ 8,500 rpm and 178 ft.lb of torque. The engines have the same pistons, rods, cams, compression, etc. The differences were the head, a keyed and balanced crank and all the other bits and pieces that I do, and a Raceco silencer. In the morning I called the customer up who re-confirmed that the engine felt smoother and had more urge than before.* He also said that Steve Greenauld told him at the time that if he could have revved it more it would have made more power.

 

Caterham produce a fine car with a fine engine in it. This post is in no way aimed at detracting from what they do. They have to produce engines to fit to cars within a time limit, with constraints on budget and make sure that they are all the same, hence the CNC head. It all makes perfect sense if you are producing cars commercially that you do it this way.

 

The way I make engines is different. The R500 I re-built had a lot more time put into it and costs more to produce. As the post is to do with porting the conclusion I have come to and that I have been an advocate of is that it is possible port a Duratec by hand and obtain good, if not better results than the head that is currently fitted to the R500. As I do not port heads commercially anymore I'm not blowing my own trumpet to get work. Just in case anyone was speculating. The only heads I want to port from now on are for race engines over 280 bhp and development heads for the flowbench to put finishing touches to the work already done. In fact for the DIYers I may at some point make all the findings on the head public so that those who are interested can do the porting themselves.

 

Another snippet of information is that the engine in my own car that was running before that R500 was introduced also runs exactly the same pistons, rods, cams and compression as an R500. The main difference is that it has the early head made 263 bhp and 183 ft lb of torque. This is with 48mm Jenvey throttle bodies and an experimental exhaust and collector that I never produced commercially. A year after it was built it made 268 bhp which justifies my claim of the engine usually making around 5 bhp more after they have been run for a while. Something I have seen on quite a few engines. These measurements were taken at Emerald so it may not be fair to compare them to the Track'n'road figure as there could be a a horsepower or two difference either way.

 

*On the subject of smoothness Dave Walker said a couple of interesting things to me recently. Since he has installed the Superflow 902 engine dyno he can't feel what the engine is doing anymore, whether it is vibrating or feeling happy. He also said that some of the big engines, up to 2445cc I produced didn't feel that nice in the car. His favourite Duratec is the 2 litre as it is also the smoothest. As the 2 litre engines are plentiful second hand it seems to me that these are the engines that I want to concentrate on and perfect. I am pretty confident that the ports, cams and throttle bodies are there or there abouts and require little or no work. Things to look at now are crank, valve springs and exhaust.

 

When I have time I will write something more about porting, how I got into it and what I learnt very early on is still applicable now. At some point I will pull up all the posts that I have written on an off here over that last ten years or so an use them as a basis for articles that will be collated into some sort of tuning book with stories from the racing days. I had a drink with Mankee last night who will do the proof reading for me (thanks to the others who also offered). I told him a few war stories that he seemed to enjoy but I often wonder if what I have to say is of any interest. I decided that the main reason for doing this is as a legacy to my sons. So they can see how their father spent his time. That's a good enough reason for me.

 

 

[7 wonders of the world]

Linky now works

[Mankee]

Cheers for the beer, Ammo! Wish I stuck around to look at those graphs, but just had to get back home unfortunately. Stories were really, really interesting. Good to see someone so passionate about the achievements in their life and have so much to tell and share.

[GasMan]

Ammo you are a priceless gem. Your sons will be very proud of you if they are not already.

Thank you.

Matthew

[AMMO]

A friend once commented that my sons and I run a kind of mutual appreciation society. We get on very well. I attribute a lot of my son's personal success from a very early age to the fact that since they were little they came to the race track and saw my team win races. They saw it required a lot of hard work. I am sure it has given them a "can do" attitude. They also saw that we had a lot of fun doing it. Life is a balance between work and play.

 

I am sitting in my youngest son's flat in London as I write. He is just got up and about to have breakfast before going to work. Just asked him the question about my "can do" theory and seeing the racing as a young boy. His answer without hesitation was "Yes, definitely".

 

On Sunday I went to a memorial lunch with the Team Bike / Team MCN crowd. People came from far and wide to remember some of the guys that are no longer with us from those days. One of the guys was a rider, then mechanic Dave Chisman. The event is held on his birthday. His mum who is in her 80's always attends. This was the 26th year. Also to remember Howard Lees and Kenny Irons. Once the glasses had been raised some of the old stories started coming out. They still make us laugh to this day.

 

Getting a lot of the things we in writing is a good idea. Some of the stories around the racing are really funny and would be good to share. I spoke to rider turned journo Mat Oxley at the lunch. He says that there is less money in writing than there was ten years ago. The advances and royalties on books are hardly worth having but if I do it it will be for the same reason I have done most things in my life. For fun and because I enjoy doing them. His parting words were if you want to make money writing books write one about Valention Rossi. They sell.

 

Tuning engines, racing and all the other things I have done I did for the sense of satisfaction not neccessarily for the financial remuneration. That is why if there is no money in a job and it is also no fun I won't do it nowadays. I get up at 4 am to look at dyno graphs because the passion has come back after a couple of years of not really thinking about engines that much.

 

A friend, mentor and teacher to me was Manfred Hecht of Raceco Cycles based in Brooklyn, New York. When I asked him how much money he made tuning Guzzis he said "You don't think I do this for the money do you? If I wanted to make money I would do something else". Manfred worked from 9 am to 9 pm every day of the week. I was introduced to him by Guzzi tuner John Wittner in 1986. Manfred did John's heads.

 

It is because of Manfred that I eventually bought my first flowbench and started porting heads. In the late 80s we paid Manfred $1,000.00 to port a pair of Guzzi heads we supplied. I asked for a trade discount. He said no, because you will only ever buy one pair of heads and after you see how they are done you will do your own. In all the years I dealt with him I never got a penny discount. I used to import his parts into the UK and Manfred imported my parts into the US. Manfred taught me not to discount, there is little enough money in the jobs nowadays. To be magnanimous and give away money as if it grew on trees is not that smart. When people don't charge enough they go to the wall. If I can't make a profit I won't do the job. I'd rather have a nice lunch and watch a cowboy film and fall asleep on the sofa in the afternoon. Financially the result is the same but without getting your hands dirty.

 

When I asked Manfred what secrets or principles he used for porting, rather than tell me he said to look at a Jaguar D type head. This was in the days before the internet so I went to the library (or it might have been Chater and Scott's in Isleworth as I lived around the corner at the time) and after going through a lot of books found one cross sectional drawing of the port, manifold and carburettor. This gave me some sort of idea but the drawing was quite small.

 

Not knowing what to do next I decided to call up Jaguar and asked if the guys who did the D-types were still around. They said no that they had retired but gave me a number I could reach them on. I called the number and got this really nice old boy on the 'phone and told him what I was trying to do. He spent time explaining things to me. What he told me can be summed up in very few words. The critical dimensions of the throat and ports in relation to the valve size. These "magic numbers" are the ones I have been using since the late 80s and seem to always work. Apart from the fact that they are not "magic" at all. They are well documented.

 

The Ford Duratec is pretty much spot on with the critical dimensions. Anything you do is to improve what is already there. It is possible to get the intake up to 178 cfm @ 10" with the stock valve and without resorting to ports that are that much bigger. The heads with bigger ports give worse flow figures at low and mid lifts. They make big numbers at lifts we don't have cams for at around 15 or 16mm. As realistically you are not going to use cams like this best it is best to stick to sensible dimensions for the port, save time and money and keep the gas velocity high as ultimately this is what will help fill your cylinder and help volumetric efficiency.

 

 

 

 

 

 

 

 

[ruff seven]

Hi Ammo, I kind of think you are pushing this thread into an abyss, sadly the days of good technical debate are gone, with the likes of Mr Carmichael now sailing the seven seas, I have only just renewed my membership after a long time away, and I guess you have inspired me once again as we are both professional engine builders and have over 6 decades of experience between us alone, although in different products we both work to very same standards, we have no Bull**** factor! we also are rubbish business men! we have never sold ourselves by adding the wow factor, you mentioned the Nissan Touring car power figures, that was bull**** they never made that, they were not far off ISTR being at a certain Wiltshire based company when Keith Odor was driving they never made that late 270 early 280, Vauxhall,s were quicker late 280 early 290s but the BTCC bull**** is the same as all the others,you as well as a few others who build there stuff on proper formulas will get the power you quote, I have seen Raceco work,Dave Andrews, George Wadsworth to name but a few, and the stuff is right, screwed together well and a great attention to detail, I guess this is why our failure rate on our engines is so low, but it does still frustrate me how some comanys products are so hyped on what they offer and it isn,t near the mark, It made me laugh when you mentioned BMEP, I had a couple of young lads in my workshop a few days ago spurting massive figures on a VAG 2.0, honest mate they are going to go to the Moon with that, I hate writing stuff so I am going to hit the Coffee mmmmm

[AMMO]

I was kind of hoping that posting would start a technical debate like the ones we used to have.

 

As for BS numbers we used to get that all the time in racing. At the end of the day all the calculations, flowbench and dyno testing are pretty meaningless. The real test is the back straight at Snetterton where we did a lot of our racing in the early days. When we had 78bhp out of the old 2 valve Guzzi we went past guys who quoted 90 bhp. When we got the engine up to 91bhp we went past guys with over 100 bhp.

 

I did a V8 4.2 Ford race project. Assessment, porting, plenum mods, cams, etc. Up from 327 bhp to 397bhp on restrictors. Everyone else was quoting 440bhp. From the outside the stock cast plenum looked standard. On the inside it was a different matter. Flag drops, BS stops. I was told that the car went past everyone else, sounded completely different and revved 1,500 rpm more.

 

Been doing more BMEP calculations this morning specifically related to the BTCC engines which makes me rethink some of the statements I made in the past. Will fire up the BMEP thread again. From a totally selfish point of view, even if nobody else participates it helps me organise my thoughts and put them down in writing.

[Klunk]

Please keep going with the technical stuff - some of us are very interested

 

I've been trying to get to grips with some of the calculations but struggle to find explanations that start from words, if you see what I mean. Lots of calculations but not from first principles. Also nearly all the calculations are for 2 valve not 4 valve engines. As an example, do you just translate valve areas/port areas from one to the other maintaining the same overall area, or are completely different calculations required?

 

Would it be possible to work through the key calculations for an engine with a view to highlighting issues of the design? I don't want you to give away your secrets, but would welcome any wisdom you could impart.

 

Regards,

 

Giles

 

[AMMO]

Klunk, it is good to have some feedback and to know that someone is actually reading this stuff. Sometimes I think that I probably sound like a deluded old twat that is talking to himself. People who know me personally might actually agree with this last statement.

[Jonathan Kay]

Please keep it coming.

 

Earlier on you discussed the various ways of publishing your thoughts. I'd encourage you to put them on the web with free access, good proofreading and lots of pictures. You can then have informal discussions (like this one) on whatever forums you choose, but the more definitive bits can look good, as in traditional books.

 

Two people who have done this well are Sheldon Brown (although I don't like the design) and Edward Tufte.

 

The extra effort and cost of producing a traditional book made from dead trees doesn't seem worth it, unless you want to try and make money from it, which is very hard.

 

Jonathan

 

Edited by - Jonathan Kay on 24 Feb 2013 10:43:11

[myothercarsa2cv]

😬 Reading every word and can't wait for the next instalment!

 

Don't be disheartened that there isn't the kind of technical debate you were looking for - you have to understand that this is way over most peoples' heads. If I tried to start a debate about what I do for work, I'd be talking to myself

 

But do know we appreciate the insight, it's fascinating

[Tony Whitley]

If you're looking for feedback: yes, you do sound like a deluded old twat that is talking to himself But please don't stop, I've found every word enjoyable and enlightening.

[Klunk]

deluded old twat that is talking to himself

 

ROFLMAO! 😬 I sometimes get that feeling when discussing technical minutiae. I've got better at spotting when people are about to reach for the matchsticks nowadays!

 

Would very much like to understand the details so please keep it coming *thumbup*

 

Regards,

 

Giles

 

 

[John Vine]

Quoting AMMO: 

and to know that someone is actually reading this stuff.

Well, someone is -- over 1900 views at the last count. I for one find your posts gripping and most informative, so please don't stop!

 

JV