Chipping

Don't Chip - Here's Why

Last Updated 20 April 2001

The views expressed here are my own, are the results of several peoples work and experiences, and I believe are correct. I'm not saying anyone is a liar, or even being economical with the truth; I just think they are wrong, mistaken or badly advised. If you disagree with me, then email me, and I'll post your opinions on a page linked to this.

For some unknown reason, some people think that the standard cars' 377BHP and 419 ft/lb of torque isn't enough. So, to pander to these peoples wishes, several companies have produced so called super chips which reprogram the onboard Engine Control Unit to produce more power and torque. I've seen several chips, advertising various power increases from a relatively small 420 BHP (11%) to a huge 525/550 BHP (40%/46%). As far as I'm aware, all these power increases are achieved by chipping (and occasionally some extra boost control) alone, and none of them involve any engine reworking at all. You can expect to pay £400 to £600 for such a 'chip only' conversion, and then £1000 per 1000 miles to repair the damage it causes. These are the reasons that I would advise anybody and everybody to avoid buying chipped cars.

MEMCAL's Are Rare As Rocking Horse Sh*t

To chip a car, the chipper had to dismantle the ECU and replace the 'chip' . This is easy on some cars, but not on the LC, because the 'chip' is soldered into a module called a MEMCAL. If the chipper damages your MEMCAL during the chipping process, neither they nor you won't be able to replace it, and your car will be worthless. For more information on MEMCAL's, and what chippers do to them, click here

Head Gaskets

I could give you the names and EMAIL addresses of half a dozen people who have had conversion, and only one has not had any trouble with it. The usual scenario is for the head gasket to blow somewhere near cylinder 5 or 6, the place where the block gets hottest. Two different people, each with an (allegedly - see later) 500 BHP+ conversion, have each needed 3 replacement head gaskets in the last year. To exacerbate the problem, Vauxhall ran out of supplies last year, and new ones only became available last December. And there is a big question mark about the design of these replacement gaskets. They appear to be modified GSi3000 ones with extra holes cut in them. Even if they are genuine LC gaskets, several people have already blown 'new' head gaskets, so something is wrong somewhere. Vauxhall are reportedly investigating this, but I wouldn't hold my breath if I were you.

Even if the gaskets are OK, another problem has surfaced. Having made some new gaskets (reportedly about 100), how many head bolts have they got at Luton? I'll give you one clue - its less than one. That's right, having made 100 head gaskets, the stupid !"£$%^& at Luton have run out of head bolts now. You need 14 to bolt the head down, and any sensible company making 100 head gaskets should have ensured they had 1400 head bolts in stock at the same time. This inescapable fact seems to have escaped Vauxhall, part of the worlds largest automotive group.

One final point is that when a head is removed, often it needs to be skimmed to make it perfectly flat again. The workshop manual only permits 10 thou to be skimmed off the head. Any more than that, and you are supposed to replace it, and that's over £2000, if you can get one. Skimming more off risks bringing the valves into contact with the top of the pistons, and also increases the compression ratio, leading to more head gasket problems.

Other solutions to this head gasket related problems have been tried, including wells rings and copper head gaskets, but so far I haven't heard any good results reported from them.

How do chippers increase the power?

Small power increases are available by improving the inlet manifold, the exhaust manifold and the exhaust pipes. But as I stated earlier, none of the conversions I'm aware of include any engine modifications whatsoever. All of them rely on increasing the amount of boost pressure the turbos can generate. To understand how this works, first you have to understand how a turbo increases an engines power output.

A standard LC has two Garrett T25 Turbos which are driven from exhaust gasses from the engine. These 'pump' air into the inlet manifold, and hence force more air into the engine. The amount of power and torque that an engine can produce is directly related to the amount of air (or more accurately oxygen) that can be burnt in the cylinder. So doubling the amount of air that enters the cylinder will (more or less) double the torque and power the engine can produce.

Normally aspirated cars (i.e. non turbo ones) rely on standard atmospheric pressure to force the air into the cylinder. If you were to measure the pressure in the inlet manifold of such a car with the throttle wide open, it would be close to one atmosphere, which is 14.5 psi, or 1 bar. However, on a turbo car, the turbos effectively pump high pressure air into the inlet manifold. The more air goes in, the more exhaust gasses are produced, causing the turbo to spin faster, pumping in yet more air. If this were allowed to continue indefinitely (so called uncontrolled boost) the pressure would grow out of control, and the engine would explode (or the head gasket would blow).

To prevent this happening, there is a mechanical bleed valve, called a Wastegate, on the turbo. On the LC, this is set to open when the inlet manifold air pressure reaches 1.55 bar. So, all other things being equal, the LC can get 1.55 times as much oxygen into its cylinder than an equivalent, non turbo car, and hence can produce 1.55 times as much power. However, car makers soon realised that for short periods of time, (like for the traffic light grand prix !) extra boost is desirable. To achieve this, an electrically controlled valve (called a wastegate solenoid) is inserted in the path to the wastegates. The ECU can pulse this on and off very rapidly, allowing the mechanical wastegate to see only a portion of the real manifold pressure. On the LC, the standard ECU software allows the boost pressure to be raised to 1.7 bar for short periods of time in this way. This is where the 377 BHP figure comes from. So as a baseline, the LC's engine can produce 377 BHP with a boost pressure of 1.7 bar.

What the chippers do is to reprogram the ECU to permit higher boost pressures. The Wastegate solenoid is under the exclusive control of the ECU, and so in theory it could maintain any boost pressure you like. Suppose you were to chip the car to permit 2.0 bar. This would yield approximately 430 BHP (377 * 2.0/1.7) . To get 550 BHP, the boost pressure needs to be close to 2.5 bar (1.7 * 550/377).

Power, or Torque ?

Most of the claims people seem to make regard increased power, or BHP. However, for the reasons explained below, I simply don't believe that without fairly major modifications to the engine sensors, fuel pump and injectors it is possible to exceed about 430 BHP. All the standard components seem to be tailored to support a maximum of around 2 bar Manifold Air Pressure. So until someone can explain to me how simply changing the chip can increase the power more to more than this, I'm sticking with my view.

And even if someone has rolling road figures that ‘seem’ to show the above is incorrect, I won’t surrender just yet. Unless the figures are actual flywheel figures, rather than extrapolated ‘at the wheel’ figures, the margin for error is probably +/- 10%, so you can’t be sure to within 40 HP anyway. Take a read of http://members.aol.com/pumaracing/power3.htm if you want to see why.

But what I can't deny is that chipped cars do seem to have more power. I have driven a chipped car, and it does have a lot more mid range 'grunt' than a standard car. But I'm pretty sure this is due to increased torque, not power. Read http://members.aol.com/pumaracing/power2.htm for more information, but basically torque is directly related to the amount of air you can get into the cylinder. Increasing the boost pressure has the effect of forcing more air into, and so will have a dramatic effect on torque at all values of RPM. However, power increases are only really available at high RPM, where on the LC other factors like fuel injectors and fuel pumps actually conspire to reduce the available power.

At lower RPM (2000-4000 rpm), the fuel injector and fuel pump issues don't come into play, because there is much longer for the fuel to be sprayed into the cylinder. I think this explains why people (including me) say the car feels more powerful in the mid-range, but I reckon its all down to increased Torque, not power.

So I'm claiming that it isn't possible to chip an LC to produce more than 430 BHP. Why I hear you cry.......

The Manifold Air Pressure (MAP) Sensor

In order to know how much fuel to inject into the cylinder, the ECU needs to know how much air is going in. If you do the physics, you'll work out that for every gram of air going into the engine, you need to inject 14.7 grams of fuel. This is called a stoichimetric mixture, and is a compromise between maximum MPG, maximum power output and minimum pollution. In practice, at wide open throttle (WOT), a lower figure is used (around 13:1) to maximise power at the expense of fuel economy and pollution. The ECU calculates how much air is going into the cylinder from the RPM and from the pressure of the air in the inlet manifold. To know the pressure, there has to be an inlet Manifold Air Pressure (MAP) sensor.

The LC has a single MAP sensor mounted on the middle of the inlet manufold. It is a linear 5V device, which can measure pressures from almost 0 bar (0V output) to approximately 2.05 BAR (5V output). The voltage output does to the ECU where an Analogue to Digital converter converts the signal into a digital number that the onboard microprocessor can use to calculate the fuelling.

So - Have you noticed the first problem with chipping yet ? The MAP sensor can only measure up to just over 2 Bar. Anything above that and the ECU is working blind, and has to guess what the MAP really is. It is possible to buy 3 Bar MAP sensors, and you could fit one of these to an LC, but as I stated earlier, to the best of my knowledge, none of the aftermarket chipping companies modify the engine, or its sensors in any way.

Overboost Protection

The MAP sensor performs a second function. If the mechanical wastegates were to jam shut, or the boost solenoid failed in the open position, or one of the pipes to the solenoid became detached or split, then there would be nothing to limit the pressure that the turbos could generate. This would lead to an exploring engine in no time flat. To guard against this, the ECU continually monitors the MAP sensor, and if it detects a pressure in excess of 1.98 bar, it switches off the fuel injectors until the pressure drops below 1.3 bar again. This is the so-called overboost protection. In addition to this, the ECU will log a fault code so that an engineer can tell what the problem is. Typically the fault codes are TC16, TC46 or TC66.

So - Have you noticed the second problem with chipping yet ? The MAP sensor can only measure up to just over 2 Bar. The chippers can't raise the overboost protection pressure value above 1.98 bar because that's basically the maximum the sensor can measure. So to permit 2.5 bar, they simply disable the overboost protection software. It's no wonder then that several owners have reported getting almost daily TC16, TC46 and TC66's, is it !

Fuel Injectors

OK so lets assume we've fitted a 3 bar MAP sensor, and recalibrated the chip with new overboost protection values. What do we do next? Well, if the MAP pressure has increased from 1.7 bar to 2.5 bar, then obviously there will be about 50% more air going into the engine. So if there is 50% more air going in, the ECU will need to inject 50% more fuel (remember, the mix is about 13:1). This is where we hit the next problem.

Several owners, including me, have been connecting computers to our cars for the last year or so, and logging the ECU data via the ALDL link. We have all noticed that at high revs, the injector pulse duration approaches 100%. In otherwords, the injectors are open all the time, squirting in as much fuel as they can. Max power on an engine is usually close to the maximum RPM, and in the LC's case occurs at about 5500 RPM. At this engine speed, there is only 22ms per induction stroke. But if you increase the amount of air going into the engine by increasing the boost, the ECU can't match it by increasing the amount of fuel, because they are already working flat out. This leads to fuel starvation, and a weak mixture, which in turn leads to very hot engine temperatures and exhaust valve burning. In other words it is very expensive to repair.

The Workshop Manual states that the fuel injectors are capable of supplying 4.75g of fuel per second. This is at 100% injector pulse duration, and it is generally recognised that this amount of fuel is enough for about 420 to 430 BHP. One owner has even spoken to the original injector manufacturer, Rochester Products (now owned by Delphi Automotive) and they do not recommend sustained running with more than 80% pulse duration. In other words, enough for a sustained 350-360 BHP.

So - Have you noticed the third problem with chipping yet ? The standard fuel injectors can only supply enough fuel for a standard car running a standard boost pressure. There are a couple of ways to overcome this, the most obvious of which would be to use bigger injectors. However, as I stated earlier, to the best of my knowledge, none of the aftermarket chipping companies modify the engine, or its sensors in any way.

Fuel Pressure Regulator

Another way to overcome the fuel starvation problem would be to change the fuel pressure. The standard injectors are calibrated to deliver 4.75g when there is 3 bar of fuel pressure across them. What this means is that when there is a complete vacuum in the cylinder, as there is with the throttle closed on overrun, the fuel pressure needs to be 3 bar. When there is 1 bar in the cylinder (partial throttle opening) the fuel pressure needs ot be 4 bar. At WOT, the fuel pressure needs to be MAP + 3 bar.

To achieve this, all cars, not just turbo ones, have a fuel pressure regulator mounted on the injector rail. This device has a pipe going to the inlet manifold, and its job is to ensure that the fuel pressure is always MAP + 3 Bar. To increase the fuel flow, you could change the Fuel Pressure regulator to a 4 (or even 5) bar device. This would increase the fuel flow rate by 20 to 30 %, but as I stated earlier, to the best of my knowledge, none of the aftermarket chipping companies modify the engine, or its sensors in any way.

But even if you did change the fuel pressure regulator, you still won't have cured the fuel starvation problem because....

Fuel Pump

Although the standard fuel pressure regulator tries to maintain the fuel pressure at MAP + 3 Bar, it can only do this if the fuel pump is capable of providing fuel at sufficient pressure in the first place. On the LC, the fuel pump is a Bosch device, and is capable of providing fuel at up to 5 bar. Therefore, when using a standard fuel pressure regulator (MAP + 3 bar), the maximum boost pressure is going to be 2 Bar.

If you changed the fuel pressure regulator to MAP + 4 bar, then sure enough you'd get more fuel into the engine at low MAP's. But once the MAP exceeds 1 bar, the fuel delivery will not be predictable, because the ECU assumes a constant pressure across the injectors. Similarly, on a standard fuel pressure regulator, once the MAP exceeds 2 bar, the fuel delivery will not be predictable for the same reason. If you were to chip the car to produce a MAP above 5 Bar, instead of fuel being injected into the cylinder, the contents of the cylinder would be injected into your fuel tank !

So - Have you noticed the fourth problem with chipping yet ? The standard fuel pump and fuel pressure regulator are good for a maximum of 2 bar MAP, or about 430 BHP. The only way around this is to fit a bigger fuel pump, and change the fuel pressure regulator. However, as I stated earlier, to the best of my knowledge, none of the aftermarket chipping companies modify the engine, or its sensors in any way.

Turbo Overspeed

I don't have any figures to support this, but none the less, I believe it to be true. As stated earlier, the LC uses 2 Garett T25 turbos in parallel. The Idea is that 2 small turbos spool up much quicker than one large one, and thus reduce so-called 'Turbo Lag' On the standard LC, there is virtually no turbo-lag. However, small turbos spin-up quickly, and can reach very high rotational speeds, in some cases several hundred thousand RPM.

I am told that the 2 T25's on the LC can only supply enough air to support a 2 bar MAP on an engine as big as the LC (3615 cc). If you try to increase the MAP above this, then the turbos overspeed in an attempt to supply the air demanded. This causes them to overheat, and in extreme cases, they can destroy themselves.

So - Have you noticed the fifth problem with chipping yet ? The standard turbo's are only good up to about 2 Bar, or 430 BHP. To overcome this, you would have to fit bigger turbos (some people fit T35's). However, as I stated earlier, to the best of my knowledge, none of the aftermarket chipping companies modify the engine, or its sensors in any way.

Conclusions

All the above seems to me to indicate that perhaps 400-420 BHP is achievable fairly easily, but more than that ? One owner actually said to me that any company claiming to be able to chip an LC to more than about 430 BHP without having modified most or all of the above is "Bogus". On the present evidence, I agree with him. What is true is that you can get quite large increases in Torque at low to medium RPM by chipping. This gives the impression of a lot more ‘Power’ but it’s not power, its Torque.

During out ALDL logging experiments, many of us have found that there is a lot of knock sensor activity at medium to high power and RPM. We are only guessing at the moment, but this may be as a result of a lack of fuel due to the injectors and/or fuel pump not being up to the demand (and it’s probably not helped by me running cheap 95RON fuel). Anyway, the result is that the ECU pulls out huge chunks of timing, and this will inevitably affect power output. But if we are right, and the knocking is due to fuel starvation, then the last thing anyone ought to be doing is increasing the boost (unless your pockets are deep enough to pay for the inevitable damage that will result).