General engine tuning tips (VERY General)

[waynne]

Just thought I'd put this here as it covers most of the frequently asked questions. Obviously I've knocked this out quite quickly (10 mins to be precise) so if i've missed anything out or made any glaring errors let me know.

Smaller engines under 1.4l
These are relatively solid and can withstand a fairly good redline usually higher than some of the larger capacity engines. As these engines do not produce much power there is not much of a gain to be had from them. Adding an induction kit and exhaust will make the car harder to live with. A fast road cam that exploits the high revving nature of these engines is probably the best thing you can do. It is also worth increasing the fuel by getting larger injectors. (Often models in the same range with larger engines have compatible injectors so see if the injectors from the 1600cc will fit your 1300cc engine.)

Mid size engines
1.4-1.8l This is actually a very wide band of engine types and sizes. The base upon which to build is greater so there is more of a reward from tuning them. I would recommend a sports exhaust particularly on the higher revving Japanese engines. I would still hesitate to add an induction kit but a panel filter which is a direct replacement for the standard paper air filter is a good compromise. Towards the upper engine sizes of this range you will start to see gains from the addition of forced air induction either a turbo or supercharger. Because you are adding pressure with forced air induction you should seek to reduce the compression ratio of the engine and run at a relatively low boost level. Addition of Nitrous Oxide injection can also yield some silly power gains. Fast road cams will have a good effect too but not in isolation - to free up the power generated by the cam you will need the sports exhaust and a better flowing air filter.


Larger Engines
2.0 upwards including V6 V8 etc.
These are the big daddies. The tend to provide much more low down torque than the smaller engines and all have good tuning potential. Inductions kits generally work quite well as do sports exhausts of 2.5-3inches in bore diameter. The larger the engine the more you have to gain by adding a sport computer or reprogrammed ecu. Due to the nature of these big engines I would not recommend a turbo application due to the internal engine modifications that would need to be applied, but mild supercharging is still beneficial. CAMS would also have a good impact on the performance of these engines, especially the silky smooth V blocks, but as the gains are much bigger than with the smaller engines fuel uprating becomes vital or you run the problems of running too lean. Temperature control is vital as the larger cylinders produce and hold a lot of heat. Ensure your cooling system is up to spec and use water wetter to raise the boiling point of the coolant. Overheating can be a major cause of engine failure.


Diesel Engines
Diesel engines run differently to petrol engines in that the compression within the cylinder causes the fuel and air to burn as the pressure increases. The big problem with diesel engines is that they have very high compression ratio's and the fuel does not burn as quickly as petrol engines so typically the engines have much lower redlines. This is why many performance diesels come with a 6 speed gearbox with low ratios to cope with the relatively short power band. Manufacturers have experimented with pre warming the diesel before it goes into the engine and various methods of direct injection so it is actually quite hard to give general tuning advice. With nearly all Turbo Diesel engines there are quite silly power gains to be had with a remapped ECU - or the addition of a piggy back ecu which takes over much of the timing calculations. 'Chipped' diesels are still very economical and users have reported that they are much more free revving and easier to live with. Servicing is vital though to keep the engine running at peak efficiency as a chipped engine is quite unforgiving.


Turbo Engines
The largest power gains to be had are on vehicles equipped with a turbo. A straight remap of the ECU yields a lot of extra power sometimes as much as another 25-30%. Turbo engines have to cope with a lot of stress so most leave the factory in a very strong state. Uprating the turbo with either a larger turbo or twin turbo set up can help improve power even further but with this route all other aspects of tuning should be explored to release the full power available (Sports exhaust including flowed down pipe, induction kit with a cold air feed, larger valves and flowed head, bigger injectors and a larger more powerful fuel pump, strengthened bottom end of the engine if you are increasing the power by more than 50% of its standard spec).

[HDi fun]

From a diesel perspective, anything that isn't turbocharged is a waste of time from a tuning POV. Similarly, anything that isn't using electronically managed direct injection is a pointless tuning proposal.

Get rid of those two ointment bound flies and things get more interesting. My 2001 plated Peugeot 406 2.2HDi has been re-mapped from factory spec 136bhp (and it's pretty good in that tune with 235lbft to play with!) to a whopping 192bhp@4150rpm and 329lbft (yes, that's right, I have NOT confused Nm with lbft) delivered from 2250rpm. This endows the car with mid-range thump that wouldn't disgrace a Boxster or Audi TT with the silly enigne option. NO stopwatch necessary, this is a genuinely rapid car now.

All you anti-diesel folks will bang on about 0-60. Yep, well, I've never put a stopwatch on it in anger but you can do it in well under 8 seconds without going over 3500rpm! In gear is a bit of a giggle too - 50 to 70 in FOURTH in about 2.5 seconds!! 70 to 90 in fifth in under 6!!! Flat out, who cares, the factory spec is said to be good for 129mph.

Go figure for yourselves - and then dial in over 35mpg when driven in anger - at the age of 36 I've half grown up but, boy (or lady) do I lurrve that sheer muscle.

What you MUST do, however is;-

1. declare it to your insurers - although it's probably undetectable, any underwriter will do ANYTHING to avoid paying a claim

2. Keep your servicing right on the nail. By the book or more often with the oil/filter swaps. A re-map is really only using up the reserves the manfacturers built in to cope with neglect. Sometimes I wonder if it's done to make it possible to sell petrol models, though. I recently drove a BMW 328i petrol and it felt so bloody spineless in comparison.


3. Set aside a couple of hundred quid a year extra for tyres - you're gonna enjoy the drive )

Kind Rgds,

Paul.

[waynne]

Nice post Paul you make some good points - I'm thinking of doing a whole diesel tuning section on the site and am looking into internal engine Modifications etc that work well on Diesels - I'd appreciate your thoughts. A remap is sooo easy and rewarding but there must be other options as well. I'm thinking turbo upgrades and modifications, head work, Cams etc. The engines are similar but there are some major differences so it would be interesting to see how these compare.

You seen the spec on the BMW 330D? Just proves they can make a VERY quick diesel from the factory.

[the_names_james]

Low weight and high power are the most essential things for a fast car.

Keep the inlet air as cool as you can.

[waynne]

I think I got too focussed on the Engine - thanks for the tip James.

[HDi fun]

Yes, I've driven a current 330d and also a 535d. Both are disgustingly rapid from the factory. These engines can still be made to deliver more torque, but you have to question if it's really necessary given the ease with which they both fling themselves foward in response to a gentle squeezing of the right toes

I do think that manufacturers modestly undertune the current crop of performance diesels in order to create a place in the market for their petrol powered models. For some folks, only petrol will do. Curiously, in my estimation these are of the older generation who will not even test drive a diesel car because 'they're slow and nosiy, aren't they?'. Just look how many current model Micras are being driven around with Nissan's excellent but spineless small cpacity 4 cylinder petrol units. Try the dCi 82, for example. It handles like a go-kart (Nissan is bloody good at track-like steering in road cars) and accelerates absolutely beautifully. It would suit my Dad perfectly.

As for internal Modifications for sophisticated diesel engines, I think that the rewards obey the law of diminishing returns. With forced induction there's only so far you can go with cam/valve lift and air (gas) flow. Especially with a diesel engine, given the limited rev range there's not that much reward from tuning a head in the traditional way. Diesel burns very slowly (hence the 4000rpm peak BHP most achieve, even if they will spin to over 5000rpm).

Getting the flame front inside the combustion chamber to accelerate faster than the piston crown is the only real option, and this is to some degree achieved by allow small amount of fuel to be injected during the expansion phase of the engine's cycle. Too much of this and you get smoke and soot, and burn a load of fuel. Increasing the BMEP (brake mean effective pressure) by means such as increased boost can assist. This, too, is a double edged sword as the biggest fraction of the atmosphere is nitrogen, which, although good for cooling, is still incombustible. That's where nitrous comes in, in the same way it does in a petrol powered vehicle. The gains achieved in this way can be absolutely silly, but given the cost and legal position with regard to road usage it's a bit of a white elephant.

Increasing the cetane rating of diesel fuel is quite effective in increasing the release of 'free' power. With a diesel engine, the key is getting the fuel to burn more rapidly, as opposed to a petrol engine where octane number is God. Higher octane petrol fuels burn more slowly and resist pre-ignition better than low octane fuels.

Good results can be obtained with cetane improvers. Sadly, these can prove expensive and should not be used in engines that are Euro Iv (2004) compliant. Strangely, the 2.2HDi I use (which is a 2001 model) is 2004 compliant. The particle filter (subject in itself) can become blocked or excessively obstructed by use of such products.

I will post more very soon on this topic, but I'm being hounded by my kids to cart 'em up the road and fetch 'em back a decent Indian takeaway - they've got style too

Cheers to all,
Regards,

Paul Anderson.

[waynne]

Cheers - Paul - great stuff. You've swallowed a technical manual. My wife is writing an article on Octane for me and I'll ask her about cetance - she has a sience degree so she knows her stuff and might be able to give some interesting suggestions at the chemical level for us. Hope the kids like the curry and appreciate the heavy sacrifice you are making to put food on their table

[HDi fun]

They're like a couple of bloody pirhanas - eat ANYTHING. No sacrifice really - I, too' like my tucker.

The weight thing is very very sensible. Not only does less weight mean better performance for free, it also puts less load on tyres, which allows braking and handling to be optimised. It also reduces the load on the environment as less fuel is required, thereby the release of exhaust gases is reduced. I'm not a green lobbyist, but I do take some care to minimise environmental impact. (strangely, this also applies to my eating habits - let's dump the supermarkets with their over priced low quality products. Let's dump the crap petrol and diesel,too. For the record, I buy meat from two or three local farmers and utilise my big BIG freezer, which means I can live on top quality stuff every day for well under supermarket money. This helps fund my fuel bill and heavy right boot

Back to performance diesels, and I've said it before elsewhere in these discussions, but engine mass/weight is a standard problem with diesel cars (especially FWD ones). That heavy engine can upset the handling balance of a car. Diesel units are heavy; they're dealing with big compression ratios and big torque figures. as such, the bearings are larger in diameter, the gearboxes belong in lorries and tractors even if the change quality is good. Clutches are getting on for 12" diameter and require fluid operation and servo assistance to make the things pleasant to drive.

As for the environment, any pollution is bad, but, come on Mr Blair, we do rely upon our cars for essential travel. Let's face it - is going to work a luxury? I wouldn't go if I didn't have to! So how bad are we that look after our cars and optimise their performance? Commuting is not a hobby. And if, let's sat I go for a fifty mile blast on a Sunday once in a while. I'm still contributing to the HM C&E pot for the privilege of buring fossil fuels.

Consider the pleasure yatching fraternity. They're pissed that they are gonna be required to pay duty on fuel. If they don't pay duty on their leisure activities, why should you and I? Please, Mr. Brown, can I claim back duty on diesel that I burn for leisure in my car?

Think it through,

Rgds,

Paul.

[JammasterJ]

my dad drives a 330 and i can agree, it's quite the beast! driving that then going back to my Corsa is quite depressing lol!

[HDi fun]

Oh yeah - modern diesels go stupidly quickly.