OK i've just got a trophy yellow 120+ 1.8 zr. I known nothing about mechanics/modding etc. How I can I increase the BHP on a tight budget? I like the acceleration as it is now but it has given me the taste for more power!!! :flex:
Cheapest will be a filter change (probably 1-3 BHP if you are lucky). Couple this with a decent sports cat exhaust with performance manifold. add a 52 MM TB at a later date and also chipping. After that you are in to serious dismantling (and money) but then your options are for high lift cams, vernier timing pullys, gas flowed heads, bigger valves etc.
Then again there are the more 'exotic' modifications, forced air induction (Turbo/Blower), Nitrous.
Once you start getting serious with your power then expect things to break more often as you start to subject them to greater stresses and strains. Extra power means extra strain on transmissions so be prepared to buy more clutches/brakes/tyres etc.
You will need to spend more on servicing as well as a performance engine will be more temperamental and need greater looking after (think of Scoobies and Evos with thier 4000 mile servicing regime compared to the 12000 on the ZR)
Dont forget the extra costs as well of Insurance (most insurance companies hate modded cars) and the increased fuel consumtion. You will almost certainly have to use Optimax full time as well to prevent engine damage.
Of course the cheaper option would be to buy a 160 or a different make like an Evo/scooby etc!
Hmmmmm I remember Mike S doing a Tune up on a mates ZR 120..............and Burning the Valves out!
There are no shortage of "Automotive Snake oil" out there that is total B/S. MGR themselves do parts Xpower Sport & Raceing. I was reading their information on Thursday............as i remember they employ Janspeed parts and get an Honest 150 BHP.
Be VERY worried about power claims, Janspeed can be trusted, but most other just want to lift your leg.
Please don't get sucked into this "fit a chip and get 200 BHP" crap!
The biggest problem with the 1.8k is that it was created from an engine that originally had a ceiling of 1400cc and with the head carried over for all Mpi versions of the 1600 and 1800 K series developments, it means quite simply that the flow capacity of the head and the cam profiles are being stretched by the extra capacity, especially the 1800's extra 400cc. This has the effect of pulling the torque and power peaks lower in the rev range and sees the power plateau quite early in the over 4500rpm range, then drop away quickly over 5500rpm.
In the years I have written features for magazines, be it the MGOC mag or commercial specialist mags I have explained the engines operation using the simple analogy of a water pipe with many taps along it's length. Essentially the input is the base water pressure, equating to normal atmosperic pressure, and the output equates to the power you get. The various taps along the way are open or closed different amounts and these relate to the various aspects of the engine, and how efficient they are.
Thus you take a global view of all parts and in simplistic terms if you want the maximum water flow you have to see all taps opened fully. If you left one tap that is closed the most alone, and opened every other tap you would see little change in the outflow, until you opened up that one near closed tap and the you would see a big increase in flow.
Engines work in just the same way in that you have to assess the various parts of the engine and how they are restricting the engines power production capacity or not. Unfortunately there is no one single tap to open as there are many which are closed differing degrees and as you open up the one closed most, then there is another which now becomes the most restrictive. This is why there is so much complication and to a degree a number of routes to achieve a given power level.
In base terms if money was not a restriction you would be changing much and fettling what is left, but the reality is that most of us have relatively shallow wallets and we need the cars to be kept working for daily transport. This means we have narrow windows to fit various bits and bobs and hope that we get value for money. Plus we have different goals depending how we want to use our cars.
The advise above is pretty spot on for the 1.8k with the most effective mods being a replacement induction system from cold air pick up to throttle body, and then an exhaust manifold and matching cat back system. Interestingly the cat if in good condition and specifically not blocking up through internal breakdown through mistreatment contacting speed humps or driving through water etc, (they can be pressure tested on the car) is in my experience completely non restrictive for engines up to 160bhp. I have been up to 180bhp and not shown any characteristic restricions in the power graphs, but I feel the 160 level is a sound one to operate with.
If a cat fails then I have done tests with cat replacements, and various available cats and noted that generally you often lose a little power with a cat replacment pipe, normally in the region of about 2bhp. Sometimes there is a gain, but the best I have seen is 2bhp again, so really cat bypass is a waste of time unless you want a noisier exhaust or the cat has become partially blocked. This of course is of little value to any ZR, as at the begining of 2001, before the Z range launch, ECD3 emission compliance arrived with the post cat Lambda sensor and if the cat is removed of fails then the MIL lamp illuminates and the engine managment drops into a failsafe mode that doesn't give best operation. Bypassing this is now much more complex and in truth for these levels not worth it.
On the positive side of things I have to say that the standard cat was actually better than any aftermarket cat tried and only bettered by the sports cat with the much bigger gas passages within the core of the cat. It shows you should never rule out the efficiency of a standard part until categorically proven to be restricted!
Anyway I have gone off at a tangent. Once the induction and exhaust is done then the 'tap' closed the most is the cylinder head, for just the reason I identified at the top of this post. The VVC is a recognition of this but with a clever and quite effective degree of complexity thrown in to try and get the best of two worlds, which it does.
There still remains very significant scope for improvement in the MPi head and this is why a modified head is included in the XPower tuning kits. There are some significant production compromises within the standard head casting, specifically around where the valve seats are fitted into the head and where there are inefficient steps between the back of the seat inserts and the ports. These is considerable scope for gentle cleaning of the ports and blending in these steps. This and a little reprofiling provides quite a significant increase in flow that does transpose into additional power throughout the rev range, giving more torque throughout and adding a bigger boost to peak power. Personal experience with much wilder modifications shows that you can add over 30% more power through Mpi head mods, so that which is acheived in the XPower kits is quite modest but something that can be regarded as a quite reasonable real world expectation, and which is often bettered.
One other thing that is often considered at this stage with a modified head would be to look at cams. These are included in the XPower stage 3 kits and even the production 134bhp TF135 spec is largely achieved through a cam change. It would be possible for TF135 cams to be fitted to a ZR120 and then MEMS3 to be updated with the TF map. Without it expect the engine to be a poor runner at lower rpms as the management system relies on MAP (inlet manifold pressure variation) sensing for calculation on engine load conditions, a fundamental core input for correct engine management control. Cam changes have the most significant effect on manifold pressures and so have a larger knock on effect with engine running.
A couple of years ago I tried a new pair of Kent first stage cams in a standard MGF 1.8i. These were said to work with the standard engine management system, but small print did say ECU changes 'may' be needed! From the moment the engine started it ran like a complete dog! I spent hours checking cam timing and a range of other engine parameters to no avail. I then hooked up Testbook and found a couple of minor fault conditions which when rectified still made no difference. I then used Testbook's live time reading for each sensor circuit and noted that at idle the inlet manifold pressures were running between 62 and 64kPa. I know that a standard engine needs to see below 40kPa to have any chance of smooth running and ideally below 35. In essence the cams were allowing the vacuum level in the manifold to be only half what the system is mapped for, so no wonder it was grumpy as hell until 3000rpm was reached.
Since the whole point of this excercise was to see how effective a cam change was on it's own, as this is about as far as many MGOC members would wnat to go with engine mods, it was a resounding flop. To confirm nothing was wrong with the car I simply refitted the standard cams with all the same parts and started the car by just reaching in and turning the key. It started and idled perfectly smoothly and continues to run that way today.
On the other end of the scale I have seen Piper's basic cams, that are said to be useable with standard management system mapping, fitted to other engines and indeed they were. Needless to say I am biased towards Piper.
Other things that has been tried include the substitution of the original plastic manifold for the alloy one first used on the VVC and now also used on TF135. (Incidentally the 1993-5 MEMS 1.6 spec alloy manifold is quite effective on smaller engines, but is a little restricted for 1600 and 1800 engines) Generally speaking the plastic manifold promotes slightly better low rpm torque and whilst it is said to be restrictive above 140 bhp this is a progressive thing and I have found little difference below 150bhp. Once above this mark though and I feel that the VVc inlet becomes a worthwile change and probably going to give you another 5 or 6bhp. Note though that minor differences in the specs of these manifolds exist depending on age and this impacts on sensor fitting. Additionally there are some other mounting variations, such as the return fuel pipe under the manifold and additional support brace rods to help with the alloy manifolds extra weight. If changing it is best to get a complete kit from one of the specialist suppliers.
There is quite a port mismatch between VVC manifold and MPi head as the manifold has much bigger ports to match the VVC head. In addition it is designed to mate to the 3mm higher set VVC port, so you have to take care that some VVC inlet gaskets are able to squeeze out at the edge of where manifold and head ports meet, thus generating air leaks. Before TF 135 I used the old 1993-5 MPi gasket which overcame this. There is just a single current inlet gasket which should cater for this though.
In overall tuning terms access to the ZR engine is great - especially compared to my more frequent dealings with the same engines in the MGF and TF! I know that being familiar with the engine is a great help, so I would simply open the bonnet and have no qualms diving in and changing a head within 3 to 4 hours. However, aside from the specific considerations applicable to just K series engines, they remain simple to work with and exceptionally light, so fitting a modified head can be regarded as simple as changing a head gasket. The benefits of such a change will be felt immediately and get better over the following 2 to 300 miles as MEMS adapts to the new smoother engine characteristics.
150 very torquey bhp in a ZR does make for an exceptionally quick cross country car and in some important respects quite a bit quicker than a standard 160 (Just look at the standard 120 in gear acceleration times against the 160 and imagine these enhanced) The KISS principle of Keeping It Simple S***** applies and is why so many less exotic spec cars are always the most surprising in terms of what they deliver.
However,Most people are NOT that keen on swaping heads on their cars!
Yes, if you know what your doing its stright foreward, however there are problems.
The K series is VERY water sensative, eg if its not blead the right way its HGF time, Lotus had a number of Elises go after just 50 miles on the clock because some bod at Hethel didn't do his job!
I think you need to KEEN to start swapping heads etc, and their is the warrenty issues as well. My Advice would be to fit X-Power parts and than MGR have no come back. If you want more than get a Dealership THAT KNOWS WHAT IT IS DOING to fit the mod head, again your Warrenty is covered.
Bolt on bits...............good idea
Major re-build work...Bad Idea.
If you want more BHP than Move to ZS V6.
You will see a decent improvement without having to take the head off of the 1.8. Induction kits and exhaust manifold fettling and cat back replacement do a good job on this engine. Anymore and you are going to be spending money that would be better off going towards a 160 in the first place.
The performance gains from fettling the exhaust are quite suprising and certainly is a better way to go than throwing cash at a new manifold if you are on a budget.