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Discussion Starter #1 (Edited)
A Guide to Common Engine Tuning Options

First things first, power gains stated are all estimates taken from manufacturer's websites and threads I have read. Please don't go through this thinking I've a 105 engine and if I get all the mods added together they will give me 175BHP or whatever. Power gains DO NOT work like that, certain components complement each other. This is not a definitive list, if people have useful things to add the feel free, either myself or a mod will change it.

Exhaust Systems

The best way to achieve any power from the exhaust system on any K Series is the Janspeed 4/2/1 manifold and sports cat, twinned to a high quality stainless steel catback system. The most common cat back systems used on the forum are Janspeed or Blueflame exhausts. Most power gains are to be achieved from the manifold and cat, as these are the most restrictive part of the OEM exhaust system. The catback itself will barely add any power, but will make the car feel a bit smoother to drive. A full system should see power gains of 7-8BHP.

Decats - Decatting the VVC engine has been proven to lose power due to a lack of exhaust scavenging. This may not be the case for a non VVC engine, however you will not pass an MOT with a decat, unless your car can pass emissions and has something that looks like a catalytic converter in the exhaut system.

Induction Kits

There are 3 options here; Panel Filters, Open Cone Induction Kits and Enclosed Induction Kits.

Panel Filters - Cost around £35 from the likes of K&N and Pipercross. Have a greater flow rate than an OEM paper filter, which helps get more air into the engine. They also sound a little bit throatier. Far better than an open cone induction kit as they are less susceptible to heat soak, which loses power. No significant power gains, but I feel they make the car smoother to drive.

Open Cone Induction Kits - Cost around £50-£75 again from K&N, Pipercross etc. All these do is make noise basically, and it has been proven that an open cone filter will reduce power as it sucks in the hot air around the engine. If you can protect it from heat and get a good cold air feed to it, then it MAY slightly increase power.

Enclosed Induction Kits - Cost upwards of £100. The 2 main ones are the BMC CDA and the ITG Maxogen. These have the best power gains out of the 3 options, but at a higher cost. A throatier induction noise to the car, and most importantly, due to the enclosed design the filter does not suffer from heatsoak. Power Gains of 5-6BHP.

Inlet Manifolds

For those of us unlucky enough to have the black plastic inlet manifold, we can fit the alloy VVC manifold (£70-£100) as long as we use our standard injectors. This benefits from having larger ports, which allow more air into the engine. However, on a non VVC engine, the inlet ports of the cylinder head need to be matched to the ports of the inlet manifold. This removes the step caused by the difference in port sizes, and improves the flow of the air/fuel mixture. Power gains of 4-5BHP at most.

Throttle Bodies

2 options here, stay with existing the single throttle body setup, or individual throttle bodies.

Single setup - A simple modification is to swap the 48mm plastic throttle body for a 52mm Alloy one (£40-60). This allows more air into the engine, and also benefits from not being warped by heat and sticking, which can happen to the plastic throttle bodies. Power gains 2-3 BHP.

Individual Throttle Bodies - These cost upwards of £1000 for a kit made by the likes Jenvey. Very good power gains are to be had, however they require standalone engine management, which adds to the cost of the kit. These sound amazing though, and if you are serious about naturally aspirated tuning, are a great choice for power gains. Power gains from a conservatively guessed 15BHP upwards.

There are so many options for camshafts it is unbelievable.

Non VVC engines - The cheapest and easiest camshaft option is a pair of TF135 cams (around £100 second hand). These allow more air into the engine due an increased lift, which basically pushes the inlet and exhaust valves further open. They also have a larger duration, so the valves are open for longer, allowing more air in or gases to escape. If you can't source some TF135 cams, PTP R140 cams are said to be the same grind, but will cost more. Power gains on a 1.8 are around 7BHP.

VHPD Camshafts - Found in VHPD K series engines (S1 Exige, 340R and Elise Sport 190 VHPD engines). These have a very high lift and duration, which lends to high power gains. However, they require solid tappets and standalone engine management. Around £340 brand new. Power Gains from 10BHP upwards.

Piper currently offer 8 different sets of camshafts for the Non VVC K series, and prices start around £350. These will produce more power than TF135/PTP R140 Cams, but come at the cost of they may require solid tappets (standard ones are hydraulic), vernier timing pulleys or standalone engine management, which adds to the cost. Power gains range from 10-20+BHP depending on the cam grind.
PTP also offer "RT sport" camshafts. Again these work to the same principles as above, and require standalone engine management, and possibly solid tappets. Cost £343 at current time. Power Gains probably around 10BHP.

VVC Engines - The VVC mechanism is only good up to about 180BHP. Piper offer a reprofiled exhaust camshaft at a cost of £182. Expect a power gain of 6-8BHP.
Solid cams for a Non VVC engine can be used in a VVC engine, and Piper also produce a kit to allow the use of solid cams. Currently these cost from £780 according to the piper website.

Just a note about camshafts, the additional components I have mentioned cost roughly the following;
Solid Tappet Kit - £550 from PTP
Vernier (Adjustable) Timing Pulleys - Around £200

Cylinder Heads

Standard Non VVC Cylinder Head - The 1.4,1.6 and 1.8 Non VVC engines all suffer from the same pitiful cylinder head with poor high rev breathing. These can either be modified at home or by a professional (I recommend a professional does it unless you are really confident). TDR Motorsport (PM Nasty) offer a cylinder head modifying service. To get more power from the standard cylinder head you would need larger ports and valves, exhaust port polishing, 3 or even 4 angle valve seats, gas flowing etc. Expect to see gains from 7-10BHP.

VVC Cylinder Head - This has larger valves and ports than a Non VVC cylinder head, and can be used on a non VVC engine in conjunction with a piper solid cam set, or even the VVC mechanism can be used with some modification to the cylinder block. Power gain estimated at a conservative 6-7BHP using standard solid cams (I really don't know for certain). Cost £300 upwards.

VHPD Cylinder Head - This have even larger ports and valves than a VVC cylinder head, and are very sought after. Power gains estimated at 10BHP plus, but, they are very costly to purchase. I have seen VHPD cylinder heads castings with no components sell for over £1000.

Engine Management (ECUs/Remaps)

2 options here; Remaps and Standalone ECUs.

Remaps - These are where your existing Rover MEMS engine management is reprogrammed to get the best out of it. Mems 1.9/2 is not re-mappable (Rover 200's) however as soon as EU3 came out along with Mems3 they are re-mappable. Any car manufactured from 2000+ is re-mappable . Power gains from 5BHP upwards. Prices begin at around £300.

Standalone Engine Management - These are fully programmable by many engine tuners and also by yourself! For the ultimate power gains a stand alone ECU system is recommended. Common ones are Megasquirt, Emerald and Omex. Prices range from £300 second hand on ebay, to upwards of £1000. Power gains of 5BHP upwards (depending on how tuned engine is)

Forced Induction

The cheapest way of getting forced induction is a T series engine transplant.

Turboing the K series requires many custom parts fabricating, low compression pistons etc, and is a costly venture. There was a turbo K series used in the rover 75, however they are few and far in between. Some companies offer turbo conversion kits starting from £5000 upwards, and offering power gains of 30+BHP.
There is also a supercharging kit available at a cost of £4000 upwards with similar stated power gains to the above turbo kits.

Engine Transplants

The most common engine transplant is the 2.0 Turbo Rover T series engine. The engine is found in Rover 220 Turbos (Tomcats), 620ti's and 820 vitesses. The easiest way is to purchase a donor car and transfer all the engine, running gear, electrics etc over to the ZR. This can be done at home for as little as £1500. AA Autosport are leaders in this transplant, and are well worth speaking to.

Other notable transplants in the past have included the Reyland VAG 1.8 20v Turbo engine, which is offered from £4000 upwards. There is also a VTEC engined ZR. These are all costly transplants as they require a lot of time and custom fabrication.

Of course, with the right money and know how many different engines could be put in a ZR, it's just whether or not it's worth it.

That's all I can think of, if anybody has anything to add feel free.

Premium Member
6,216 Posts
FYI - My standard 1.8 with TF135's ran 125bhp on the dyno with similar torque figures.

Got some extra stuff you might want to add... Been writing it at work for my own thread over the weeks.

Nitrous Oxide - Nitrous is a great way to add power if you do it properly. On a standard non modified 1.4 K series you have the ability to run in the region of an extra 70bhp of power with no other modifications. Power gains will depend upon the size of the jets you use, most kits start off with 25 jets and work their way up to frankly silly size ones of up to 400bhp. Now, dont go rushing for the 400 jets, as its not THAT simple... First some background.

As you can see, ive put it in the forced induction section, as essentially it is. Your introducing more oxygen into the combustion chamber allowing more fuel to be burnt and more energy to be released. The oxygen is added in the form of N2O, the oxygen splits from the nitrogen and combusts with the fuel, excess nitrogen is not used in the combustion process and leaves the chamber along with the other waste exhaust gases. This has a great advantage of being able to spool a big turbo very quickly due to the large ammount of exhaust gases passing through at lower RPM. It also has the benifit of supercooling the pistons, due to nitrous being a compressed gas, like any when its released its very very very very cold. This alloys you to run pistons outside of their 'normal' limits while N20. NOTE - THIS IS NOT CARTE BLANCHE TO RUN 500BHP WHILE ON GO GO GAS!

Any engine will be able to take more nitrous at a higher RPM, so in the essence of safety, its best to scale your shots. This progression saves your engine, tyres, and you. A straight hit of 50bhp in a FWD car in the wet can produce some intresting handling characteristics. With progression you can start your extra power off at say 25bhp, scaling up to 50bhp over an extra second. This helps prevent stress on the drivetrain, less of a shock on the components such as the clutch and gearbox bearings. Similarly, it saves your tyres, and allows more a faster start off the mark, with more power on tap as you climb up the rev range.For the moment ill refrain from going into great depth over the details, as I could waffle for pages...

For a shot of 25bhp, you wont need a progressive controler as the standard pistons will be fine for this. On a 160 its possible to run a 40 shot without risking piston crown damage, but past this I would be very skeptical. Ask superspy for details on what happens... Past a 25 shot a progressive controler will be needed. These great gadgets allow you to scale in the nitrous, starting at a small shot, then over time increasing the size till a peak is reached. With this you can run much larger shots, a 75 shot is pushing the limits of the pistons, but should be possible on the 105. As for the 120, your starting with more horsepower to begin with, so the pistons are already working harder. I wouldnt want to risk running that much, but to be honest, its down to your own common sense, if its too good to be true, it probably is...

Choosing a kit is simple. Ignore every piece of advertising out there, and choose a WoN kit, they are far superior than their American counterparts (produce up to an extra 50% torque over them!!), have great support via their forum, and wont destroy your expensive engine due to solonoid failure. Entry level kits start out at £489 for the Streetblaster 150i and upwards for direct port. The entry level progressive controlers start at £229 and are more than caipable for street use.

Sounds expensive, but to put this into scale, running a 75 shot thats a mere £9.57 per BHP. Cheapest power out there by miles. Except for the fact that youve got to fill up your Gas tank every now and again depending upon how much your using it.
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