Is this normal? Duratec content. Could be boring for some.

[AMMO]

I woke up in the middle of the night thinking of crank balancing and cylinder head porting!

 

The bottom line is I still love engines and am still curious about them even though I don't build them professionally any more.

 

I saw Dave Walker at Emerald a while back when we were dyno testing one of my 280 bhp 2 litre Duratec race engines. He says the older you get the more you realise that you don't know anything. I tend to agree. He seems to like to quote me on things and one of his favourites is "He's a teenager, quick, give him a job whilst he knows everything".

 

Years ago when I was based in Surbiton we took on a young guy called Andy. He was 18 and knew everything. It took a while for me and my head mechanic, Max, to knock him down to size. Most of the young kids we had come through the workshop were totally useless. You gave them a job, they would do it badly and then sit down for a rest. We were supposed to be getting the cream of the crop from Kingston College. What made Andy different was not only was he a whirlwind and couldn't wait to get stuck into the next job, but that he was curious. That curiosity set him apart from the rest. I'm pleased to say that Andy turned into a top race mechanic.

 

What makes engine building interesting is that there is always new stuff to learn. I'm still curious. My 2 litre 280 bhp engine reaches the 8,500 rpm rev limit with the power still rising and the torque still in pretty good shape. Another 1,000 rpm would be nice but that is when you probably start breaking things. So far the engine has been very reliable. I have one customer in the UK who has raced one of these engines with great success for four seasons. Another customer in Italy has done 16,000 km of track miles. I cut my teeth in 24 hour endurance so reliability is paramount.

 

You could just rev the engine another 1,000 rpm and see what happens. When I have asked my customers if they wanted to rev the engine more and that they would foot the bill if it all went wrong they haven't been keen to do this. I don't blame them.

 

That extra 1,000 rpm could be what kills what has been a very reliable engine spec.

 

So I'm awake in bed and thinking. The ports are fine. They are not overly large and the 54mm throttle bodies offer a restriction to the flow. Even bigger bodies would work on these heads but that would raise the point of max bhp even higher. I've even thought of making the ports smaller to match the throttle bodies and raise the gas velocity and get some more inertia supercharge effect. Everybody is going for huge CNC ports with low gas velocity and throttle bodies that are too small so why not try something different? The ports on the heads on my own engines are not as pretty as the ones I do for customers. I use what I call a RAF finish (rough as f**k). I did an RAF spec head for a customer and he complained even though his 2.3 engine in an Elise made 273bhp. Dave Walker says the same spec. engines always make another 10bhp in Caterhams. So not too shabby.

 

The engine was one of a batch of low mileage units I had imported from the States in the early days. It had been run so there was carbon in the ports. I didn't bother porting some bits that didn't need doing so some parts of the ports were clean and others still caked with carbon. It was one of the early, lower flow heads. The job was so cheap and had so little money in it that I left the inlet ports unfinished. I'd gone in with a rotary burr and left it at that. Just couldn't be arsed to do a BS job on it. The complaint even made it into press in Walker's column. The customer was happy with the power but unhappy with the way the port looked. My attitude is who cares what the port looks like as long as it delivers the goods? Unfortunately the customer wants to see it looking nice. From my testing the rougher port performs as well if not better, but try selling that to the customer. If you want to get technical look up eddy flow and boundary layers. But the smaller rough port flies in the face of the big smooth port that everyone thinks they need.

 

The other thing is that every engine capacity, power output and rpm will have a different valve size and porting specification. The same head on different capacity engines with different power outputs is a bit daft in my opinion. There is one guy I know who turns 2 litre Duratecs into short stroke 11,000 rpm engines who makes the ports smaller and a successful motorcycle tuner in the 600 Supersport class who does the same. Everything is in proportion. A big capacity engine needs bigger ports and valves than a smaller one.

 

The cylinder head aspect aside the main problem is the revs. There are all sorts of things that can happen with an extra 1,000 rpm. The current clutch will explode, so new clutch and flywheel. The stock crank is not adequate in my opinion. It has some flaws that would not make it suitable for continued high speed use. OK for the odd sprint or track day maybe. Would I trust it to do a 24 hour endurance race at Spa where you are at maximum throttle for a long time lap after lap? No. So straight away you are looking at adding another 4 or 5 grand to the price. Who wants to pay it? Nobody in my opinion. Another reason to stop engine building.

 

The steel cranks that you can buy off the shelf are also not to my liking. They haven't been properly thought out. Some crank manufacturers are great at making cranks within tolerance but not designing them. I employed a proper engine designer who also designed a Moto Guzzi crank for me in the 90's to design my 9,000 rpm 88mm 2.2 crank. He wasn't cheap but after a year of heavy use the crank looked like it hadn't even been in an engine. Bob Vince, also an engine designer from Holbay, saw the used crank on the bench and and asked if I was putting a new crank in it was that good.

 

I've built a lot of these engines which means that I am also in the fortunate position that I got to see them again when they come in for re-builds or upgrades. The stock crank from an engine that has been raced is never in good shape. It's OK, but its main problem is that it flexes. It was also originally intended to have a dual mass flywheel so the counterbalancing is wrong as you could get away with less material as the whole assembly with its 14 kilo flywheel was effectively externally balanced. The fact that you can get away using the stock crank for quite high outputs and high rpm doesn't take away the fact that it is not really suitable. Again think 24 hour endurance rather than 60 second sprint. The stock Zetec crank is a much nicer crank in my opinion. But that was intended to run with a solid flywheel. The Duratec crank looks cheap in comparison. The fact that you can take it out of a 145bhp road engine and double the output and it stays in one piece is a testimonial to the metallurgy, not the design. I bought a bunch of blown up Duratec race engines at one point. The cranks that had survived were not in great nick.

 

When the engines let go they do one of two things. Either the bottom end or the top end goes. If you can stop them doing that everything will be fine.

 

With all this talk of supercharging it seems that my route is considered passe' so it looks like I will never get to build the engine I really want to.

 

Hope my ramblings were not too boring.

[Martin J]

Hope my ramblings were not too boring.

 

On the contrary, I found that a very interesting read, thanks.

[Garry7]

This could link to the "Why I wouldn't leave the club thread"

Its great that acknowledged experts in their field share stuff like this - I havent messed with engines for years (25 ish), but now having built my 7 my interest has been rekindled - I run a Duratec).

Thanks

 

 

Edited by - Garry7 on 26 Jan 2013 10:51:36

[CaterBram]

Ammo, Great post and thanks for sharing,

[elie boone]

it's good to see that i am not the only one waking up in the middle of the night thinking about building things.

I agree that if the design is flawed the outcome can never be brilliant, however i think that balancing and porting is key.

Forged pistons are about 1.3 to 1.5gr in tollerance, in these modern times this is huge for me, it takes 30min to bring them down to within 0.1gr and pistons are the most heavy things mouving in an engine.

Polishing ports is IMHO useless until you go north of 10.000rpm i think that valve design is more important than polished porting, a lot of people be unhappy if the ports are done manually but are soo happy if they are done CNC machined.

Supercharger are arround for a long time, they offer the same performace for a lower budget, that is unless you want a smooth engine then the work on the engine stays roughly the same.

😶‍🌫️

[ECR]

Fascinating Ammo ....

[rj]

Quoting Martin Jeffrey: 

Hope my ramblings were not too boring.

 

On the contrary, I found that a very interesting read, thanks.

 

 

+1

[tbird]

Another one (or a series) for LF ? "Ramblings by an old engine builder " 😬

 

Very interesting read

 

Tim

[Birkin S3 ZA.]

I will need help with mine.

Chris

[mav]

Always find your rumblings interesting, just a shame I've never had the money available to ask you to build me an engine.

 

Would love to see some of your stories from your 'racing days' in LF, if you ever have the time to put finger to keyboard.

[myothercarsa2cv]

Ammo, quick question if you don't mind... How do you make ports smaller? Can you add material safely?

I too woul love to build the engine I dream of, but it's a little different, and still to expensive for me! My other problem is that I don't have your wealth of knowledge! (if anyone's interested, I'd like to build a 50bhp 2cv engine that isn't with a silly cam or charged)

 

Thanks for the thoughts, though - very interesting Feel freeto impart your knowledge any time!

[AMMO]

A 50bhp 2CV. Now there's a challenge! :-) If you have some budget you should come and see me. I did a tiny bit of work on BMW boxer twins and discovered a couple of interesting things.

 

One of the things I used to do quite a bit of is engine assessment. Basically clients would bring engines in bits and pay me for my opinion. I've done work on rally engines, MGs Porches, GSXR 750 and 1000 for Rizla Suzuki (the year Jon Reynolds won the BSBK championship), old engines for historic racing.

 

The historic racing guys seem very reluctant to try anything new. "Nobody has ever done that before" Is what we usually hear. They seem to think you need to do the same old stuff that was done in the '50's to a 1950s' engine. One of my ex employees has done some good work with MGAs. He done what he calls a Raceco job on it. He even asked if he could use one of my experimental Duratec cams which worked really well in the old two valve per cylinder engine (didn't work that great on a Duratec though!). The old MGA flies and has been doing a lot of winning over the past few years.

 

When I said make the ports smaller I didn't express myself properly. What I actually meant was not make the ports as big as I currently do. In practice only alter the important parts of the port and not touch the areas that are probably doing nothing.

 

I played around on the flowbench adding clay in Moto Guzzi ports years ago. You could get an improvement by adding material to the port. I am very reluctant to add epoxy as I'm afraid it might fall off eventually and wreck the engine. So I tend to do what I think is the best job I can with what I have. The GSXR 1000 I was involved in had epoxy in the ports. I didn't do the head work, just the flowbench testing, airbox and air entry duct assessment. I did design and supply the carbon fibre trumpets for the throttle bodies though. Hard to believe that was ten years ago.

 

In the early days of owning my first flowbench I tested something like 30 heads for an MGB. The customer was very serious about his racing and had won his class outright but wanted to beat the V8s too. Something he could do in the wet as the V8s had too much torque for the conditions. We had an engine on a dyno and just swopped heads. A very interesting experience as we could compare the flowbench figures against the dyno figures.

 

Emerald have now got their engine dyno up and running, a Superflow 901. Funnily enough the same dyno we used with the MG and Porsches back in 1988. What would be really great is to build a Duratec engine that could left on the dyno and swop heads. Then rather than try to guess what is happening we could have some actual proof.

 

Last time we had a three day session at Emerald swopping bits was a few years ago. Probably five. The 280 bhp came to the dyno with my hand ported head and 45mm throttle bodies. It made 252 bhp. We put the 54mm bodies I had designed an had made by Jenvey on and the power zoomed up to 286 bhp. Jenvey said they were too big. I disagreed. The head and throttle body and trumpet had been designed to work as one. The 45mm bodies were restrictive on this head setup with the sort of cams and exhaust we were using. One interesting thing that Dave picked up on immediately was that there was no loss of torque with the bigger throttle bodies. We had already won races and a championship with a Moto Guzzi fitted with 54mm bodies in 1995 and won the singles race at Daytona on a Ducati Supermono also fitted with a 54mm in 1995, so it wasn't a new idea at all.

 

We also swopped the experimental 54 mm taper throttle bodies running 8 injectors for my new 54 mm bodies running only 4 injectors. This was on Danny LT's car running one of my 2.2 engines. They worked just as well so we ditched the 8 injectors after that. We also tested the 4-2-1 against the 4 into 1 big bore exhausts and 2.75" silencers against 3" ones on the higher output engines. No real difference on the two different header designs. Swings and roundabouts you gained and lost torque and power in different areas but overall the results were so similar that either with have worked as well. Reducing the silencer from 3" to 2.75" lost us 10 bhp on a 312bhp engine. Again you need a different silencer size for each power output.

 

Dave and I get along really well. We have friends in common from the old days of motorcycles. He still quotes the late Leon Moss on a regular basis. Dave laughs because when we get to certain stage of testing and it's time to start swopping things I say "OK, lets dick around". The first time I said that he commented that it wasn't a serious thing to say. But for me it is like playing with expensive toys. Coming from a creative background, you have to enjoy what you do to give your best. If you are not enjoying it then I can't see the point of doing it at all.

 

Dave at Emerald had so much fun testing he only charged me £1,000.00 + VAT for the three days. With fuel, hotel and food for me and an assistant I probable spent around £1,500.00. It might seem expensive but I saw it as essential to my work. So knowledge is not free as some people think. It actually costs quite a bit of money.

 

Anyway one thing I have come to a conclusion about in the last few days is that you really don't need bigger valves in a 2 litre Duratec. Yes in the 2.2 and bigger capacities if your ambition is big power. What you need in the 2 litre is more revs. The challenge is doing a good job designing the new bits needed and making it stay in one piece. Designing the new parts satisfies my creative side. It allows me to do my own thing. Copying others and using the parts you can buy off the shelf is no fun at all.

 

As for "Ramblings of an old engine builder" maybe "Ramblings of an old ****" Would be more apt. I'll let you be creative and choose the word you think would be most appropriate. The one I was thinking of is not printable.

[myothercarsa2cv]

How about "old hand"? I wish I had the budget, even the time would be great! But if you're still interested and I still have the deuche when I've got some cash to spend on it, I'll certainly track you down! The problem with the 2cv 602cc is that the crank only has 2 bearings holding it in the case. The chap who MOT's it built a turbo back in the day that made over 50bhp IIRC, but it burned to the ground a couple of years later. Apparently it was a b*****d to drive (crap torque curve), but quick!

[DJ.]

Very interesting thread, thanks

 

I was surprised to read that the duratec crank was designed to use a dual mass flywheel.

I'd been under the impression that only deisels use them. Just out of interest, does the Sigma engine use one?

 

Duncan

[AMMO]

Tuning a 2CV engine is the sort of daft thing I could like doing. Can't be any more stupid than deciding that racing a Moto Guzzi would be a good idea!

 

A lot of the Duratec engines I bought from the States had dual mass flywheels. Sorry, I don't know anything about Sigma engines.

[Alan Bowler]

Who was the MGB customer if you don't mind me asking? I spent many weekends watching my dad trying to keep up with the V8s in his fully modified B.

Cheers

Alan

[AMMO]

Alan

 

I'm pretty sure that the guy that I did all the MG work for was called Tony Price of T&L Autos based in Bedfont, Middlesex.

[Alan Bowler]

Fromm googling, looks like Tony Price joined the BCV8 championship a year or so after my dad left (after one too many expensive shunts), and did rather well!

Good memories - thanks!

[AMMO]

Tony was a very determined guy. He put some serious work into his cars.

 

I got a wrong telephone call at 4am and never went back to sleep. So another sleepless night thinking about cylinder heads, valves, ports, throttle bodies, cranks and exhaust systems. Probably triggered by the fact that late yesterday afternoon I looked at a load of photos of sectioned heads, port shapes and port moulds.

 

I remembered flowbench tests I did years ago with different valve sizes and bore sizes. I am now pretty convinced that the stock valve sizes are sufficient for the 2 litre. My port sizes must be right too. If they weren't the power wouldn't still be rising at 8,500rpm. If the ports were too small or didn't flow enough the power would be tailing off which it definitely isn't. Also the head work is very cheap compared to a big valve head that would add around another £2,500.00.

 

With the stock 2 litre crank limited to 8,500 rpm the race engine engine has been reliable for four race seasons. As I have mentioned before another customer in Italy has done 16,000 km of mainly track miles also limited to 8,500.

 

The safe mean piston speed should be 9,500 rpm. My old Moto Guzzi racer had an 82mm cranks similar to the Duratec's 83.1mm crank. We revved the bike to 9,200 rpm. The Guzzi factory made me a batch of ten cranks based on the 78 mm road cranks, some of which found there way into road bikes and some into our race bike. In the road bikes they have been 100% reliable. In the Guzzi racing video in ChitChat the engine failed after 9 hard laps due to the crank. After we had the crank re-designed the bike was 100% reliable for the next two years winning every race it entered.

 

I have no intention of repeating the Guzzi episode with a Duratec hence my reluctance to rev the stock crank. Remember I am talking about racing where all the available revs are used all the time, not track days or sprints. There is still a lot of development work to be done on cams and exhausts. At the moment we are only in the ball park. I'm a bit frustrated as I know there is more to come and for five years I haven't been able to take this engine further. If there had been a budget available at the time we would be much further up the road by now. My first customer crashed his car and the money he had allocated for engine work got spent on chassis repairs. Maybe next winter we can get to play around a bit more.

 

These are the things I think of at night when I should be sleeping.

[myothercarsa2cv]

AMMO, how much is something like this crank development going to cost? Would it be something racers could contribute towards, sort of like a crowd sourcing type thing, in return for your development and a small % off the final product? I don't know if anyone would be interested, but it can't hurt to ask? There are sites that handle these things and all sorts of people post ideas that need investment.

 

And don't worry, you're not the only person who struggles to sleep because their head won't switch off

[AMMO]

Engine development is never cheap. Engine assessment, crank design and manufacture, new rods, pistons, cams, springs, valves, induction and exhaust, dyno testing, etc. Lots of money.

 

You could do a cheaper job and try to improve what you already have. If you have an engine in bits you could bring it over for me to have a look at. I've always managed to make an engine more powerful one way or another. Some of the older stuff has been quite successful, old Kawasakis for racing, Guzzi Lodola 175cc for the Moto Giro and even a Honda C90 for drag racing would you believe. Give me a call if you want to discuss.

 

 

[AMMO]

As I am in full crank mode this morning I thought I would share what for me is some good news. A race engine customer has given me the go ahead to make a 2 litre Duratec crank. Using the same designer that designed my cranks in the past we will make a crank that can be reliably revved to 9,500. It will be based on my existing 2.2 88mm crank that has been incredibly reliable and shows none of the problems of the stock crank. The new crank won't be fitted until next year but that gives me something to play around with. I have to do some work at my end before I can give the data and specifications to the designer. I will also be designing some new parts to make the engine more reliable at high rpm.

 

When I say reliable at high rpm I mean something that can be kept at maximum rpm for a long time.

 

An American friend called Dr. John Wittner raced Moto Guzzis in the US and ended up being employed at the factory in Italy. I used to go to the factory often when my team was sponsored by them. The doctor bit in Dr. John was because after John did his stint in Vietnam he trained to be a dentist. He gave up dentistry and became a very successful engine tuner and designer. His idea of high speed engine testing was to put an engine on a dyno at full rpm, 9,200 rpm in the case of the Guzzi Daytona engine, and go out to lunch. Lunch in Italy can be quite a drawn out affair. So we are talking a couple of hours here.

 

That's what I mean by reliable at high rpm.

 

Looking forward to doing a 2 litre race engine my way with my parts even if it won't be raced until next year.

 

 

 

 

[myothercarsa2cv]

Great news! On the reliability testing... Here's a snippet from the Wikipedia article about the 2CV: "...test engines were run at full speed for 1000 hours at a time, equivalent to driving 50,000 miles (80,500 km) at full throttle..." (that's 6,000rpm ).

 

Seems lunchtime in France is even longer than in Italy

[AMMO]

😬 Actually the industry norm is 1,200 hours at full throttle I think.

 

The Moto Guzzi engine in question was a development engine, not one that was due for production. Two hours at full throttle is enough to have a strip down and have a look inside and see what's wearing.

 

I saw one of my engines let go on a Schenck engine brake dyno in the late 80s. It was a 1,000 cc 95x70 experimental engine. It had been run in at 4000 rpm for a few hours. We were running it up to 10,000 rpm at full throttle and everything seemed fine. All of a sudden the engine changed note and the next thing I saw was bits of big end shell coming out of the breather.

 

We shut it down as quickly as possible. The damage was not too bad and after a rebuild we ran it again a few days later. Turns out the 1mm squish wasn't sufficient at 10,000 rpm and the pistons had started touching the heads and knocked out the big ends. Increasing the squish to 1.2 mm solved the problem.

 

Your 2 CV engine also has a 70mm stroke. Fancy revving that to 10,000 rpm? 😬

[Dr Slotter]

Quoting AMMO: 

😬 Actually the industry norm is 1,200 hours at full throttle I think.

I would say it varies. On dynos I have experience of:

 

250 hr high speed tests (i.e. full blast) for passenger gasoline/diesel.

600 hr varying speed durability tests (i.e. replicating a driving pattern) for passenger gasoline/diesel.

1500 hr fixed speed durability tests (i.e. fixed, low speed) for off-highway diesel.

 

all purely in R&D and sign-off stages. Production versions of engines, regardless of the above would only be subjected to a short 'hot-test' predominately to make sure the bits were in at least the right places and hot oil managed to get round at the right pressure.