Evo magazine

[GrahamClarke]

Interesting one page article in this month's Evo magazine (one with a picture of a silver TVR T350C on the front), stating that many K series engine failures are down to replacement steel cranks and their poor balancing creating additional stresses in the engine.

 

Also commented that with correct balancing, the existing internals are good for 9200rpm and 300bhp.

 

I'm not commenting on whether I believe this or not (I frankly don't know), just passing the details on, so please don't shoot the messenger

 

Graham

 

[Meldrew]

How very interesting. That must explain the enormous proliferation of 300 BHP K-series engines, then. 😬

 

Fond as I am of my K-series, I can't help feeling that the only way I'll get 300 BHP out of it is by balancing it on top of a Honda engine.

[GrahamClarke]

The implication in their article was that this was new research, so simply maybe no one has tried.

 

Whilst the engine may have the potential to develop 300bhp there may be many other factors as to why no one has tried this. For instance prohibitively high development costs, cost of resultant engine, market demand, ridiculously short service intervals, ability to meet emission requirements, poor driveability at low revs, less tractable due to lack of low end torque etc etc.

 

Graham

 

[Slarty Blat Fast]

Did they surmise how long the engine would last? 6k? 6km?

 

Absolutely no hitchhikers

[Peter Carmichael]

I know a practitioner who has strong opinions on this subject - different to my own. Said practitioner is scathing with regard to the Doug Kiddie crank of mine that he inspected. Said practitioner possibly didn't appreciate the analysis that I have put into an engineering model of reciprocating stresses.

 

I am wary of a journo getting the right end of the stick on a technical issue.

 

Far more likely is that the steel crankshaft manufacturers are a little too keen to remove weight from the webs between the journals. These distort under severe loads, causing the journal clearances to run tapered and pick up. The K in 1.8 form suffers because there isn't much overlap between the main and big end journals, so the web provides all the strength and stiffness; this is a consequence of the long stroke design of the engine.

 

The Farndon Superlight crank (as used in the R500) is probably a bit suspect in this area. The Doug Kiddie cranks that I use are fairly hefty in this area and are fully counterweighted. Received wisdom says that the standard crank can go to 8500 as long as you go to steel rods. Pull out strength on the small ends of the standard cast rods is actually higher than for Arrow steel rods, but the more likely mode of failure is lower down the rod.

[normalbloke.29]

All this talk of peak BHP, give me torque any day!

 

(Cue the abuse!!!)

[greg]

normalbloke.29,

 

An an iron block! 😬

 

I also agree with Meldrew - Honda do seem to be makeing some spanking engines. Peter any thoughs on the KA20

 

Greg, Q 86 NTM (Green 185BHP XF)

[RobM]

O/T but on the subject of Honda engines, my Integra driving m8 is going on a trackday with me in 4 weeks time, and is slightly worried by the fact that I'm fitting an Apollo tank beforehand to my VVC, when, he says, his Integra R engine is very similar to mine and with no such device. Any comment?

[normalbloke.29]

Iron block and torque....now we're talking.......

[caterhamnut]

People with far more knowledge will correct or add too...but ISTR one of the issues with a 'k' in a Caterham is the fact it is mounted longitudinally, where as in most tin tops such as the Integra (and the Elise) it is mounted transversly. The lubrication system was designed to work in the transverse orientation.

 

😬41,000 miles in 21 months!

angus@tinyworld.co.uk

Caterham pics

here

[Chris W]

To get 300bhp @ 9200 rpm would mean generating 171 ft lbs of torque @ 9200 rpm. Where's that going to come from?

 

Even the R500 with a max of 155 ft lbs of torque @ 7200 rpm is only (!) generating 140 ft lbs of torque @ its max rpm of 8600. (ie: 230bhp)

 

It sure isn't going to come just from an rpm increase. To go from 8600 rpm to 9200 rpm is only a 7% gain in max revs and therefore a 7% gain in bhp. To go from 230 bhp to 300 bhp is a 30% increase. Where's the missing 23% coming from?

 

Chris

 

1.8K SV 140hp see it here

[Jason Plato]

"Where's the missing 23% coming from?"

 

- A turbo or supercharger ??

 

the 300bhp will not be at 9200rpm , but the engine may be capable of those revs ??

 

dave

 

 

 

 

[Peter Carmichael]

No Natasp K is going to make 300bhp on pump fuel. The head cannot breath enough for this. 253bhp @8600 is achievable, but just scaling in some more revs does not give you more power unless the engine has greater ability to breathe. With an 80mm bore it is just about done at these lower power levels.

[oilyhands]

The suggestion is that the *crank and existing internals* are good for I.E. strong enough for 300BHP and 9200, not that the K series is capable of churning it out. Debating whether the K can generate that sort of output is missing the point.

 

Oily

[Chris W]

Dave

 

Not sure I understand what the point is then. It's like saying the radial bone in my arm is capable of withstanding 2 tons vertical pressure; yeah and......? interesting but of no practical value.

 

Chris

 

1.8K SV 140hp see it here

[oilyhands]

The point being made is that you *may not need* an exotic and expensive steel crank for your K series engine and that using one may actually have detrtimental affects which would seem to the layman to be counter-intuitive. If the stock crank is good for more power than the engine can currently produce then why fit a steel one? The 300BHP/9200 was an illustration of that point.

 

Oily

[julians]

Is it true that you dont need a fancy steel crank to produce high power reliably though?

 

If it is true , why did PeterC and various tuners use a fancy expensive crank.

[Chris W]

One can of worms just freshly opened

 

Chris

 

1.8K SV 140hp see it here

[Jason Plato]

Is it true that you dont need a fancy steel crank to produce high power reliably though?

 

Well , a very well respected crank manufacturer says that the 1800 K crank is the weakest crank they make . Owing to the lack of overlap web .

The 1600 K crank has greater strength and less stress placed on it - rod angle etc .

 

But I guess it all depends what stress you are going to place on the crank , and for how long and of course how lucky you may be feeling .

 

With little or no firm data to base any calculations on I dont believe that this question can realy be answered . As with much of the development of the K , we all learn as we all progress .

 

Its interesting to see that QED run a 1800 K with a std crank to 220 bhp . I run a 1600K to 210+ with a std crank .

 

dave

 

 

 

 

[Joe 90]

A standard crank can be used with turbocharging to produce outrageous powers. You need a steel crank if you want to use more RPM than the standard crank will tolerate. All this talk of 300bhp doesn't really seem to have much relevance.

 

Upgradeitis ward, awaiting open wallet surgery. 100,016 miles

[Peter Carmichael]

Another slant on the point is...

 

Just because an aftermarket crank is billet steel EN40B nitrided, does not make it good. It needs to be designed right as well.

 

In many cases it just won't have been designed with the same highly intensive computational methods used in the production item. In this case such a crank could be worse than a standard one.

 

The Kiddie crank seemed to work OK though - that is a product endorsement borne from first hand experience rather than a statement derived from an in-depth engineering assessment of its merits.

[Julian Thompson]

Guys - you've all seemed to skirt the point.

 

What they are saying is that the standard setup is so well balanced that it puts little stress on its self and the bearings. On the other hand, the steel bits they tried (and of course flywheels - and probably pulleys 😬 were implicated) put the motor out of balance and put nearly 50 times the load on everything.

 

They did, however, say that "careful balancing" could remedy the situation, even if you've got the steel crank and stuff.

 

BUT.

 

1) Their "standard engine" presumably uses a standard, millstone sized flywheel. Would that mean that all Caterham setups are wobbly Bob?

 

2) Has anyone we know ever had a motor with a steel crank wipe its bearings or pull itself to pieces?

 

3) Has anyone we know ever tryed turning 8500rpm with a standard plasticine crank?

 

4) Presumably, and based on this research, an engine like mine, for example, sporting a very small pulley and lightweight flywheel may well be at risk from the increased loads they mention.

 

SO.

 

How do you balance it all? How much does it cost? Has anyone done this apart from Rover?

 

(Sorry about my lack of technical knowledge!)

[Meldrew]

The article is also interesting in that it looks like a bit of MG X-power PR.

[AMMO]

Julian

 

All engines are dynamically balanced on a purpose built machine. Production engines are good enough out of the factory. Race engines and blue-printed engines should be balanced dynamically as well, but with a bit more attention than you would with a production engine.

 

When balancing a four cylinder engine you first of all balance the crank on its own. You either remove or add metal (usually tungsten)so that the crank spins smoothly. You then add the flywheel, clutch pressure plate and front pulley one at a time, balancing each component as you go along. Prodction engines are not done this way as all the components are done individually and then mated on a production line.

 

Zetecs and the Duratec I have had done recently are very good from the factory, requiring only minimal correction. I know of one Formula Ford engine builder who no longer re-balances the Zetec cranks because they are always so close. I always balance just in case. In the case of the flywheels and pulleys if they are correctly machined / concentric they require no balancing. The Raceline ultra light flywheel for the Duratec was spot on. I would still check though.

 

Forgot to mention the pistons and rods. Pistons are all weighed and balanced / lightened to the lightest piston. Connecting rods are balanced end for end. This is done on a special jig or customised scales where the small end and the big engs can be weighed separately. Again they are lightened to match the lightest small end / big end.

 

I don't understand if the article implies that engines are being put together without careful balancing or not. If engines are failing to lack of balancing this is very poor. I can't see a pro engine builder putting an engine together without proper dynamic balancing. On the other hand I wouldn't always believe what you read in magazines either.

 

AMMO

[greg]

I'm with Ammo, what engine builder worth his salt would put together loads of expensive bits, and miss out ballancing it all, especially when this is a relatively inexpensive part of the whole process. Read the aticle and it seems abit odd.

 

Greg, Q 86 NTM (Green 185BHP XF)