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FI Engine building basics

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Some basic info if it helps? 


1. Understanding design and construction;

In my experience, I was surprised to find that the material specification for something like an Audi 1.4 crankshaft was the exact same as a 3.2 when I did some years of research into parts manufacturing, but in hindsight and more management based experience, it stands to reason really! There's often talk on forums about whether something is forged or not meaning it is stronger but this is often something of a fallacy! Uniformity of the construction of a part can change based on the actual process that is undertaken on the part in question - as an example, say you want something that is 3" thick all across, pouring material through a little hole as in casting, could lead to some areas, for example, only being 2.95", this is therefore a flaw in the manufacturing process (usually why you need to buy moulds and designs and make a few in creating a product). There are some elements to consider, but just because something is forged, doesn't necessarily mean it is naturally stronger, it is nothing more than a manufacturing process.
There are, of course, some benefits to certain manufacturing processes, ensuring a greater uniformity of structure in that example, which ultimately could mean greater "strength" as is required for your application. However, I would look into the variances between forging and casting if you are looking into buying upgraded parts and try not to be fooled with marketing spiel.




So, what does ensure longevity in this respect? Well, material spec counts for a lot to be honest, this is a major factor in aftermarket parts and I'll let Mahle give a little info on the differences between common aftermarket piston choices;




Generally, in this respect at least, there are certain piston material specifications to choose from, 2618 or 4032 for the most part for piston alloys as well as manufacturing techniques. This is what most of you will look at for your options in aftermarket pistons. However, in my own experience of custom product development, there are (in the UK development I was looking into at least), other options available, notably custom material. I remember reading the material spec sheets for a certain alloy (for pistons) that would outperform both the 2618 and 4032. What was interesting to note though in their tests, was that at typical engine cycle outputs (notably the stresses, strains and heat cycles pistons are subjected to at constant high rpm), the 4032 were better at sustaining the thermal loads (being good at handling the constant heat of an engine in operation) than the 2618 material. In every respect the 2618 was better apart from this sustained load/heat at certain loads, which, to be honest, is what you want for performance engines, but there were factors that you may take into account for parts upgrades like the fact 2618 alloy expands more - hence the rattles more than 4032 pistons in general..... again something you want for a daily rather than a drag machine. Of course, some have negated this problem by using custom material on the skirts/sides of pistons to stop rattling, this, balancing the expansion properties of that particular material and the rattling that people do not want on their daily driver, are all factors to consider!


So - PART 1 - If you're thinking of paying  a lot for aftermarket products, I would personally look into these aspects to get the most for what you want, if someone tells you "it's forged, it'll be better!", then it can get far more technical than that! The more someone wants to sell this kind of product, the more I would expect to be enlightened to some details in this respect, there are, of course, sales pitches and some info that they don't want to share (I'd look into things like the spec sheets under stresses and strains or, for cranks for example, looking into things like case hardening processes and what x company does in that respect - best bet to get the info you should want, pester them!).

I would be careful not to be caught up in simple miss-statements like "it's forged, it'll be tougher!" or even, to be honest, "Chinese made stuff is rubbish!" - I have personally done a lot of research into it and it is far more complex than that, material, QC's in manufacturing, cost v every aspect in manufacturing etc is all subjectively relative - lot's can vary here for a start, do your homework though and you'll be fine! - Good example was on the "what turbo" thread where I state about Holset and their Wuxi factory - good QC's no doubt and their material spec is likely to be the same.

Coming back to findings then on oem use of material; if VW test out an R32 crank under the extremities they usually do in their usual testing, then lesser engines like a 1.4/1.6 produce less stresses and strains in testing comparatively as an example (not actually true with design limitations and piston speeds etc but for a base example let's say more stress on the best engine means inferior engines will put up with it), then this means they can use the same material across the board that will handle the stresses for a 100k warranty! 


Producing a certain mould for a certain part and using the same material, obviously with different moulds for the crank sizes unless, for example 12V/24V cranks, saves a fortune in product manufacturing overall – thus saving millions potentially in production for a company of VAG size and in terms of 12/24v changing the efficiency of heads only... an efficient design change – means that potentially, oem is not always the best compared to aftermarket stuff, even if people tell you it is!

So, for example, this 4130 steel used (I think that is what is used for cranks back then but can't remember, example either way) - will handle all the stresses and strains placed on it when they test their vehicles. So, there is no need for something like a 4340 then as it will only be adding more cost! Not only that, but imagine the discounts in specifying the same steel across the board... 100 tons for all cranks instead of just 5 tons for R32 cranks for example, huge manufacturing savings to be made there! Also, there are other aspects in manufacturing the product to think about in terms of money management as well - machining a part for example. The tougher, or harder in this case, something is, the more difficult it is to machine - 4 hours machining a 4340 crank, or 30 mins on a 4130 adds up to a lot of money in big production models over millions of units! Take a look at case hardening/nitriding/shot peening etc, all aftermarket processes for ultimate performance (but) with added costs as there is more labour involved - doesn't mean something isn't still forged, just what has been done to help.


Ultimately then, there are always budgetary constraints to consider at a management level in the major oem production, I'm all for VW using 4340 specially hardened awesome material for their top of the range vehicles, but ultimately, apart from either finite speciality circumstances, chances are the material will have had some compromises made in production as it saves millions for these reasons!

Edited by RBPE
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So, once we have an understanding that there is a lot of marketing spiel, a lot of material and QC variances that you should look into to get the best, let's be more specific to VRT tuning!

Common destruction of engines;

I would say, in my experience, that there are two major factors in destroying engines and no matter how many times I tell people, this can also supersede any of the upgraded material specification aspects mentioned previously, it is what ultimately destroys engines the most in my opinion - age!


Engines are set up for certain tolerances, certain specifications like measurements, that can obviously change with time due to general wear and tear from the forces placed upon them! I did this little mod on a the wiki VR6 drawing but it simply shows how pressure is placed angularly on certain reciprocal parts...



But with other factors to consider!


G = Gravity, naturally pushing down on the offset angles of the reihenmotor - our baby's!


– in short, you've over 14lbs per square inch pressing down on you at any time, ambient pressure, you times this by the parts moving x amount of times over the course of an engines life, in this case angles against forces and so on..... you get wear and tear that changes the engine from how it was designed to be! Imagine gripping a tennis racket handle for example and someone twists it, you naturally loosen your grip, if you left is as is, the friction would burn you and eventually wear your hand down, same principles apply, often why you hear about lubrication of oil for example on rods, but even then this action over time leads to wear and tear! This is what destroys engines really, forces and use!


Quick links;










Therefore, simple rule is – if you're looking to ensure longevity of your engine, do not think it is necessarily good “as is” just because it runs right! I have dealt with many that think that only to find their engine pop when the boost is turned up, usually due to all sorts from blocked oil pick ups to plugs not even being in properly! I will always maintain that the simple refreshing of an engine by an experience builder, will ensure far greater longevity than leaving it as it is and even some "forged engine builds"! If you can't fork out for forged parts, just refresh it all to oem should really help with longevity.

Reason for that again comes down not to the material in this respect on a used engine - as such material can often receive some form of heat treatment in it's usage over it's lifetime, but the tolerance aspects and additional strains it places upon your components if it is not running right and the sheer depth of pressures/shearing forces depending on something like a small measurement difference and angular sheer stress!


Which moves us onto the tune.....

I assume most of you know that “a controlled burn” is what you always aim to achieve in terms of ecu tuning, the burning of fuel –  as is required for correct operation. Detonation is an explosion rather than a controlled burn and this explosion, to cut a long story short, means a hell of a lot more stresses!

So the tune is a very, very, important part, personally I have seen many pro tunes with little component protection/knock control but they still work based on what work has actually been done in testing, plus tunes like ASR (anti-slip/traction-control) dumbed down instead of tuned for example, meaning something works but not necessarily as best it should. Point being - most of you don't know what's in a tune, enquire!

So this explosion/knock, can destroy engines no matter how much you upgrade material spec to be honest, but the pressures alone could shear most materials, even hum dinger forged parts with better properties - you're simply protecting as best possible given resources! 

So be aware that tunes.... pretty much anything air/fuel/burn related, is no.1 on the list!




EDIT - I put this up on the vid section, good example based on fuel v spark/timing/burn etc;


So we understand the basics on building if looking at upgrading and/or rebuilding with stock so let's focus on building an engine for FI and saving money!

In short, the more you do for an engine builder, the more you will save yourself at the end of the day!

Taking it out of the car, stripping it down and bagging up/tagging parts is a good start, it'll save you a lot so I would do that first of all to save you some pennies. There's plenty of info on the forum for that.

So you save some money by stripping a lot yourself, and you're now aware that you need to specify that the engine builder needs to look into checking oem angles/tolerances etc and will need new oem parts at least for basics like gaskets, rings, bearings etc. This is when you budget for your forged upgrades or you aim your budget at further oem refreshing!


First port of call is the compression ratio then, with stock 6 pots running 10-11.5:1 ratio's as standard depending again on age, skimmed etc, then it would take a lot of tuning to get it right with various sensors missing and ability in the ecu, so generally, for safety's sake and on a road car at least - compression ratio is lowered to help protect from detonation.




What ratio you use can vary, personally, I have dealt with many big turbo/big name owners that run very low compression ratio's (sorting out their big name tunes) and they seem happy, up to dealing with a 2.8 24v owner who ran 9:1 at nigh on 700hp on pump fuel! I would therefore recommend keeping that ratio at 9:1 at most but this can come down to the tune as well, as mentioned, detonation and tune can make a difference so factor that in to what you are doing as those stresses count for a lot, you get different quality of injectors, fuel pumps etc. Get info on the tuners builds if you can (i.e. compression ratio, parts used, boost levels etc) - or simply research lot's of parts details and get an understanding of what they can do.


There are three main options nowadays to lower compression; spacer plate, pistons and rods;
Spacer plates can vary in thickness which brings about various compression ratios, adding a gap between the head and block, options being - roughly 7-10:1 compression I think on the market nowadays. Main thing as boost rises using plates would be squish, which is why head and block studs would be a good upgrade, although you're talking nigh on forged piston money now but deal with the basics first!




Forged pistons we've mentioned above, 4032 will expand less than 2618 which what they all seem to be, various options on skirt mods to negate this, various compression ratio's etc

Another option fairly new to the market is low compression rods, I've dealt with some big name tuners testing these out in Europe and they seem to be happy, it negates the need for a spacer plate and add's strength in design and material, as they are a few mm shorter as you can see, still fairly new at this time though;




Material can count for a lot in terms of psi resilience or any physical properties of material and manufacturing processes v stresses and strains;




Low compression rods have the benefit of adding material strength in these areas as well as lowering compression for detonation purposes, negating the need for pistons and/or a spacer plate! 


Some basic overviews;








Ebay rods v Big name

There was an interesting thread on another forum about Chinese rods and I think they came to the conclusion that the rod bolts were the weak point. I put a thread up ages ago to see if I could drum up numbers for some custom x beams (not enough interest though) and in dealing with the manufacturers and suppliers I saw test data of 210,000+psi on the bolts if I remember right, surprised to read that then on that forum thread! Again, this can come down to the manufacturers used and variances in that respect - so I am skeptical about their statements somewhat being a reference to any "Chinese rods" if you will. Of course the big names all put up some data and talk about the development in-house and we all know they tend to hold up - as mentioned in the thread though, there are many factors to consider.


When I was dealing with manufacturers I think it came to in-between a 3rd and half the cost of a part manufactured in the UK (buying/filing patent, moulds and initial product) to outsource it abroad unfortunately, which is why many big name companies have done similar with parts, but the quality specified was still top notch (International QC standards/material spec etc) and the part would have been just as good if I had got the numbers. So, cheaper doesn't necessarily mean any less of a product and the blasé statements about such parts or locations should really be looked into more in depth! 

So you have a few options, generally;

Rod bolts (stressed area/tolerances v usage) - Low compression plate (various ratio's, needn't go crazy but match to tuners requests) is a good base to start with,

Possibly head studs/main studs/bolts - squish and alignments etc plus strength/clamping forces added here

Low compression pistons - as above really

Rod's - low comp or stock, various material/costs, again as above info


But....... give it a good refresh first, budget that then changes mentioned above as a base to help longevity and that's why some relatively stock engines can reach big power without forged parts. Well.....


The head can set you back a lot.... a hell of a lot really! Not always necessary as some show;




But it is the crux of power and is still subject to stresses and strains!


The head can take a lot of money to upgrade but, aside from checking oem tolerances and refreshing as mentioned for the bottom end, you could keep this fairly simple if in good shape.
Valve guides are often the bane of VAG vehicles with high mileage, just general parts refreshing things, I can't really emphasise that enough as I have seen people try and take short cuts time and time again and it always ends up costing them more!

Valve float can be a problem on older engines, especially if you are upping rpm limit's like many tunes do, so heavy duty valve springs is a good idea to stop this, again check guides though. Think about the basics logically, you know usage can knacker the springs, we all jumped up and down on the beds as kids and know what happens to springs in the long run, so how harsh a life has your engine led, how much are 2nd hand ones etc, what rpm you gonna run... should all be considered!


Whilst you are stripping your engine for the engine builder or your own DIY you can do some little things yourself, it's what I did years ago, just bought some simple dremel tools, files etc and had a go! You can do things like gasket match your manifold gaskets to your ports, you can chamfer oil and water passages, even have a go at porting and polishing. This work can end up costing lot's of money, you are better with things like flow benches obviously, but you can do some clean up and lot's of measurements and if you're going to have a go at DIY building then why not, just do your homework and be uniform in that if you can!


Cams can help get a lot more power/torque when going NA to FI as many will know, again this should come down to the tune and changes in your set up/your goals as they are generally set up for emissions/daily driving - all of this head work should really be specified to your ecu tune/cams/revs/turbo/boost and it can take up huge amounts of budget - usually pro engine builders will have their own parts they use and a lot of this is worked out with them - in terms of DIY - well, World's your oyster if you educate yourself enough!


So, just a brief overview, I wanted to mention the manufacturing and material side and some basics outside of the usual "forged is better" kind of thing.

Edited by RBPE
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