Fuel Injection System Description Page
Fuel Injection Problems Page
1. The program that Superchips use depends on the type of MCU used in the ECU and the serial number of the ECU itself for a particular car.
2. For the installation we did, Superchips advised that our ECU and MCU, and the corresponding TVR program data, was specifically for a car in tropical conditions and probably also to meet local legislative requirements.
3. Our Superchips program was therefore a remapped version under those conditions. A 15 HP increase is claimed (rpm not quoted), and no figures yet from them on torque.
The noticeable changes after re-chipping are:
1. A more stable idle, resulting in less "rocking" of the car.
2. Pulls more cleanly from low rpm.
3. Noticeably less transmission snatch although not eliminated.
4. Exhaust sounds different; more regular pulsing and sounding more burble (than rumble) at idle, which works up to a very nice roar.
5. The engine also runs hotter; 92deg instead of this car's usual of 89deg, but this could be due to other reasons.
6. There was no noticeable change in power or torque. However, I suspect this is hard to feel subjectively since the HP increase only represents 4.4% of the Griff 500's standard output @ 5500rpm. Such a change may even occur with ambient temperature/humidity fluctuations. I believe Superchips base their claims on rolling road tests.
In summary, it made the car more driveable, especially under urban
conditions, and enjoyable in part due to the exhaust noises. With
that, we thought its well worth £165. I have to make a qualifying
statement that these observations were made after re-chipping
a car which was not well tuned in the first place [see Timing
Problem under Engine section], hence my posting on the list for
tuning specs. We would like to sort this out within the next few
days, depending when we get specs, and perhaps I'll give an update
then, which will be a more conclusive one, hopefully.
Kenny Heng
Sprint Feb 97
I have covered 4000 miles in 1996 in my 400, with few problems,
the exception being that the car often stalled. Apparently many
of the ECUs are from Range Rovers and think that the TVR is an
automatic. Mark Adams, the ECU guru, carried out various adjustments
and although tick-over became better you were constantly braking
and the idle speed was very slow to die down. Mark decided the
sensible way to do any adjustments was to carry these out on a
rolling road. He suggested Power Engineering in Uxbridge who have
carried out this service on many TVRs and 400s in particular,
and so have a good benchmark to go by.
Steve Haggen of Power Engineering appeared very competent. The car was well tied down and connected to various computers. A check was made on the state of the car's tune ie. plugs, timing etc., to check no immediate obvious problems. Then various runs were made with adjustments being made to the ECU, timing etc. It is an interesting experience to listen to your own car at 6000 rpm and be on the outside.
The rolling road used by Power Engineering is a modern one and only loads the car at maximum revs for a few seconds. During this operation every measurement is being taken ie. torque, CO2 levels, BHP etc. 400s should have 275hhp but they don't. Most have 230-240 at flywheel. Mine had 218 bhp at the beginning. After 15 runs and many adjustments the conclusion on my car was that the engine was not normal. Mark suggested that I have special heads and cam, although TVR Power say not, I have been unable to contact the first owner to verify further and as the car had only done a genuine 8000 miles when I bought it owner mods seem unlikely.
As my car is in theory more powerful than the norm, the ECU problem was even more exaggerated ie the ECU thinks the car is a Range Rover! And then does not wish to give sufiicient fuel at much over 4000 rpm. In my case at over 4000 rpm it needs even more fuel. Therefore the mixture was very weak on full throttle - pinking! Mark estimated my car to be 4-5% short of fuel at high revs. By re-profiling the ECU to give more fuel at over 4000 rpm the mixture becomes richer and the engine can run with advanced ignition settings. As a consequence my car obtained an extra 41 bhp, although it is fair to say that this is unusual.
I finally ended up with 261 bhp and 280 lbs torque at 4300 rpm.
The car was a revelation drive, much quicker yet with power throughout
therange. Costs were £300+ for the correct chip for my car
and £150 for the rolling road (£60 per hour) which included
the technician. Marks Adams now normally only ever runs his ECU
modifications in conjunction with the roling road as this is the
only way to accurately compare minor changes.
Jack Acres
Sprint April 97
Following Jack Acres letter in last month's issue of Sprint, I
feel that a few myths about ECUs and power outputs need to be
dispelled before they fester into "facts". The following
notes appertain to Rover based engines using the 14 CUX fuel injection
system as used by all later TVR Rover V8 models.
1. Large power increases can be achieved by modifying the ECUs for most modern turbo charged engines. This is possible because the boost pressure is controlled electronically, and to put it simply more boost equals more power. Obviously this is not possible with a normally aspirated engine, all that you can alter is the quantity of fuel injected and the ignition timing. So there is very little scope for power increasing. To make matters worse only the quantity of fuel injected is controlled by the ECU on the Rover V8. The ignition timing, which is more critical, is controlled by the traditional distributor.
2. No TVR left the factory with a standard Range Rover ECU. The amount of modification depended on the state of tune and intended application. Most had the following modifications:
a) Removal of the speed limiter which prevents Range Rovers exceeding their tyre speed rating of 112mph.
b) Increasing of the rev limiter in line with the camshaft and valve train capabilities.
c) Adjusting the idle speed control to achieve the best compromise of emission levels and smooth running.
d) Re-calibration of the main fuel maps (including cold start and accel/decel maps) to achieve the best power output, fuel economy and smooth running consistent with low exhaust emissions.
e) Modification of the closed loop control strategies and overrun fuel cutoff for improved driveability and emissions performance (cat cars only).
f) Re-calibration of the air flow meter input to cope with high air flows (5 litre engines only).
3. No TVR thinks that it is an automatic. There is an input on pin 34 of the ECU consisting of a 510 ohm resistor connected to ground to enable 'manual' mode. If this is not present idle speed may be low or erratic.
4. If your engine is unmodified, running the correct ECU, and everything is working correctly, it will not be short of fuel at high rpm. If you suspect that your engine is running lean then check the following:
a) Idle speed mixture: Adjust to give 1.5% CO (2.0%.will give better throttle response but poorer fuel economy). Non cat cars only.
b) Full throttle operation: The throttle must be held up against the stop to enable full throttle enrichment, corresponding to a voltage of 4.6V on the throttle potentiometer, otherwise the engine will run lean by 5-10% depending on rpm. NB. A few engines were produced, or converted, to run with large throttle diameters (usually 4.3 to 5.O litre). It is very important that these engines run the correct ECU which will enable full load enrichment at 3.6V.
c) Tune resistor: The ECU contains several "tunes" for different applications. It is essential that you are using the correct tune resistor for your engine. TVR only use two tunes, one of 470 ohms for non cat cars and one of 3900 ohms for cat cars. If the tune resistor is missing then the ECU will run in default mode.
d) Fuel supply and pressure: Check that the correct fuel pressure is maintained under full load conditions. If it is low check: regulator, fuel pipes for damage or kinks and both fuel filters (before and after the fuel pump).
5. Road speed input: This is required for correct idle speed control on all cars and it enables full load enrichment on cat cars. (check with an oscilloscope on pin 6 of ECU).
6. Improvements were made on a continuous basis. Serpentine engines benefited from improved idle speed control. Late model 400s, V8S, early Griffiths and Chimaeras may benefit from this change.
7. All TVR ECUs have a socketed EPROM holder to allow the chip to be changed easily. Standard Range Rover ECUs do not.
Ignition, Horsepower, and Detonation
Most TVR Rover V8 engines give maximum horsepower with an ignition
timing of 30 to 33 deg. total advance. However due to the gradual
decline in fuel octane ratings many early cars can no longer run
on their optimum settings due to detonation. In order to prevent
detonation and consequential serious engine damage, the ignition
timing will need to be retarded a few degrees. This can be minimised
by the following:
1. Ensure your engine is running the correct fuel mixture as above.
2. Ensure your engine is drawing the coldest air possible. High air inlet temperatures are a major contributing factor to power loss and detonation.
3. Check that your engine has an 82 deg. thermostat with a large orifice (This is a standard TVR part but is not commonly available from other outlets).
4. Check that the heater matrix bypass hose has not been removed. This is necessary to ensure correct coolant flow around the cylinder heads when the heater is turned off.
5. Use the later retracted nose spark plugs.
6. Use the latest distributor which has a more suitable advance curve for lower octane fuels, or better still find someone who can re-tailor your distributor to give less mid range advance but 33 deg total advance. (A mapped ignition system would be the best but most expensive solution).
7. Do not use an engine oil with a relatively high phosphorous content as this leaves combustion chamber deposits that can promote detonation.
8. Use a high quality fuel and alternate between four star and super unleaded if you have a non cat car.
9. Avoid chip tuning companies unless you are 100% confident they know what they are doing Chip changes are only necessary if you have modified your engine. Unless done correctly, chip changes will be diagnosed as faults on TVR or Rover diagnostic equipment. Genuine TVR chips are available for all TVR engine variants for £16.37+vat from the factory.
Rolling Road tuning
If your car is unmodified, has been correctly serviced and is
in good condition a rolling road tune will achieve little other
than relieve you of a large amount of cash. If you have modified
your car it is well worth your while in order to get the best
from your modifications unless your engine has been set up on
a bench dynamorneter. A bench dyno is the most accurate, repeatable
and safe way to test and develop a high output engine. It is probably
also the most cost effective in the long run. Points to bear in
mind if you take your car to a rolling road:
1. How good is the operator. The most expensive high tech equipment is worse than useless unless the guy using it knows what he is doing.
2. Be very careful not to overheat your engine as very few rolling roads can keep water, oil and air temperatures stable to those you actually see on the road. This is essential if any meaningful data is to be gathered and to prevent engine damage. Inertia type dynos are better in this respect as they only load the engine for a short time. Watch out for wheelspin which is sometimes difficult to detect
3. Wheelspin can overheat your tyres so can strapping down too hard to prevent it. It is quite possible to wreck a good set of tyres!
4. Ensure copious cooling air flows around the engine and exhaust to prevent bodywork from overheating, removing the bonnet often helps.
5. Who pay's if something goes wrong? It's usually YOU
6. Don't waste your time and money if you think you have more than 3OObhp. Use a bench dyno.
7. When was the rolling road last calibrated? And by whom?
8. What is the output given as?
You may be forgiven for thinking that all of the above would be the same. They are not! The first is the easiest to understand as it is the power in bhp which is actually measured at the rollers as you do the test. This power will be considerably less than you have at the flywheel and it is what is left to drive your car forward after you have removed all the losses due to friction in the whole of the drive line including the tyres. If you have measured the power whilst accelerating the engine you will have additional losses as power is required to accelerate the engine internals, the whole of the drive line and the rollers.
Some dynos estimate flywheel horsepower by performing a coast-down run which attempts to measure the drive line frictional and inertia losses. These power losses can then be added to the measured power to give you an estimate of the flywheel horsepower. This is much nearer to your engine's real horsepower but still does not account for the power used to accelerate the engine itself or the difference in friction between a lightly loaded transmission in a coast down and that of a lightly loaded one during a power run.
The other four corrected horsepowers are an estimate of what the power would be if it were measured at the temperature, pressure and humidity required by the relevant SAE, DIN or ISO standard. All of which are different, thus give quite different power figures! This correction process is fraught with assumptions and inaccuracies. The only accurate way to obtain values of DIN or SAE horsepower is to measure it on a bench dyno at the required air temperature humidity and pressure. This is both difficult and expensive.
This may lead you to believe that actual measured horse power is the only meaningful number obtained from the rolling road; well think again as this number will change as the air temperature, pressure and humidity changes. "Your power output literally changes with the weather!"
I hope that this has demonstrated some of the difficulties in
measuring and quoting (or misquoting) horsepowers. However the
actual number is not important unless you are a very sad individual,
all that matters is how well your car actually performs.
John Ravenscroft
TVR Engineering Ltd
Firstly, let me make my own position clear in this, for those who do not know me. I have been a specialist purely in Rover V8 Fuel Injection and Ignition systems for approximately six years - I do not deal with any other engines.
My work centres around modified cars, and those with particularly difficult injection problems. Over the years I have modified and fixed over three hundred vehicles. The work covers a large range of variants from Rover Vitesse, Range Rover, TVR, Morgan, and assorted competition and other specials. I can modify, test, and diagnose all Lucas systems from the ACU flap type injection system, through l4CUX "Hotwire" to the latest Range Rover GEMS management system. My background is in High Performance Real Time Aerospace computing found on Tornado and Eurofighter aircraft. The Lucas systems are simple by comparison, but the lack of processing power presents its own special challenges.
Generally I work with specialists such as John Eales (JE Developments 01203 639 647 - NOT to be confused with JE Engineering), V8 Developments (formerly Rovertec 0116 240 4344), Power Engineering (01895 255 699) and Wedge Automotive (0114 281 7507). I also have good relationships with many TVR and Land Rover dealers. I do not work with TVR themselves, for the simple reason that they are doing perfectly well without my help. My service is complementary to, and not a replacement for, the engineering work they do.
Jack Acres is a very active and enthusiastic member of the TVR Car Club, owner of one of the most beautiful and carefully maintained 400SE wedges you're ever likely to see, and a jolly nice chap too! However upon reading Jack's letter, it is open to misinterpretation - one possible view is that 14CUX Hotwire caars are fitted with bog standard Range Rover ECUs. This is definitely not the case and I'm certain that Jack (and TVR for that matter) would wish me to set the record straight. My failure to do this would malign the effort that TVR put into engineering their cars, as they always use the best and most innovative current technology available.
When any Hotwire car is presented for a rolling road session, the first step is always to plug in the laptop PC and perform full diagnostics on the Injection system - the software I use allows me to check those parts of the system beyond the reach of the more normal Fault Code Reader. There's no point in proceeding with a faulty car.
It soon became apparent that Jack's car had a fault. The l4CUX ECU contains several different tune options to cope with different end markets for the host vehicle, and this includes Cat or Non-Cat, Automatic, Manual, and Air Conditioned models to name but a few! The ECU works out that it is in a Manual gearbox vehicle by looking for a particular resistor (which TVR mount below the Fuse Box). In Jack's case this was broken, however I have seen other vehicles where it has been missing altogether (although it certainly left the factory with one there). This causes a fault code to be set in the ECU because it cannot determine the type of transmission fitted, and this in turn affects idle speed behaviour. As standard, a TVR does not think it is an automatic Range Rover.
Having fixed the fault and done some power runs, it soon became apparent that Jack's car was not standard. This showed up as massive under fuelling. Also the profile of the torque and power curves was quite unlike that of many other 400s I have cared for. Since the fuel pressure was not dropping off then the ECU needed attention.
Tailoring the ignition timing, fuel map and overall fuelling level released the 41 bhp quoted in Jack's letter, together with a massive increase in mid range torque.
Two points need to be made here. The first is that unless your car is modified, there is no way you will see such a massive gain on a standard car by tailoring the fuelling. However, it was believed that Jack's car was indeed standard - the truth was only revealed by the rolling road test. He may never have known otherwise. Several non-standard cars have been revealed in this way. A rolling road session will soon show up any problems, and if the car is standard and well maintained then it will not require a new chip unless there is something else you wish to alter.
The power and torque figures for the bulk of the cars I have run on this dyno are stored on the computer. This makes it very easy to determine the results of any modifications, and also to compare the results for similar cars to see whether they are on the pace or not.
When TVR modify the ECU they pay attention to many areas of its behaviour. Just some of these things are removal of the road speed limit (oh yes!), a sensible rev limit, idle speed, etc. As time moved on they made continuous improvements which affected other areas such as warm-up fuel, acceleration fuel, etc. Larger engined models (450 and above, and latterly 430HC models) received further modifications including scaling of the airflow meter input which is vital to achieving good driveability, overrun engine braking, full throttle enrichment point, etc. As later versions of the software and ECU itself became available they used those too. The best technology is seen in their latest Serpentine Cat cars.
All of the above things I can alter as required to suit modified engines. Standard cars can be tailored to suit the owner's preferences and to accommodate the inevitable slight variations between production engines. Any power increase here will be limited to no more than 10-15BHP at best, but may be nothing. This is your decision as the owner. Obviously early cars derive benefit from being upgraded to the latest compatible software with all the latest modifications. Please note that I do not lift the rev limit set by the engine builder for obvious reasons.
On the subject of rev limits, did you know that Land Rover use two settings - for Cat cars it is 5200rpm, and for Non Cat they use the incredible figure of 8500rpm! If any standard Range Rover hat ever achieved this then I expect the pistons are still orbiting Pluto!
It is important not to set too much store by the actual value of the power figures obtained from any dyno - chassis (in car) or engine (out of car). Both types of dyno feature advantages and disadvantages, but at least with a chassis dyno you don't have to take the engine out of the car. There are so many different ways of calibrating and compensating for the figures obtained, that actual figures may vary between dynos by as much as 30 bhp in this power class.
Personally I always use John Eales for Engine dyno, and Power Engineering for Chassis dyno work. Both these use calibrated dynos, both give realistic figures, and both largely agree with each other. However what is important is the differences obtained by any modification process which is one reason why I always use the same installations.
Power Engineering are best known for their work as Cosworth and Ford RS specialists (excellent people to talk to if you have Ford V6 power). They regularly feature in leading magazines, and build many championship winning vehicles (Vectra Ford, Eurosaloons, etc) - the list is too long to put down here. Their facility is a fully computerised, regularly calibrated, state of the art rolling road. This means that a brief single pass is all that is required to record full load figures. This is kinder to the engine, transmission, and tyres, and is unlikely to provoke overheating. It is able to read power at the wheels and also estimate flywheel figures.
One major point comes across from the standard TVR engines I have tested. The absolute power figures do not actually reveal the best part of the story. If there is one thing that marks out a quality engine build, it is consistency. As an example, all the STANDARD 390 engines, and 400 engines, I have tested have produced the same power to within plus or minus 2BHP - which is a spectacular achievement. Also they all serve up a more than generous wad of mid range torque, which after all is what gives you your acceleration. TVR do not promote these two outstanding features enough, although it is difficult since most people like to blah about BHP instead!
I hope this clarifies things, but if you want more details you
can find my number in Helplines.
Mark Adams
Internet Mailing List Nov 96
According to the Land Rover specs for their big Rover V8 engines
which form the basis of the TVR units, the tune resistor value
should be:
Cat models - 3700 to 4100 ohms
Non-cat models - 446 to 494 ohms
Source: Haynes Range Rover manual page 263 para 107
I would guess that TVR have not modified these and these are the
right values although in a couple of other books I have on tuning
Rover V8s, talk about replacing the tune resistor with a variable
one and thus fooling the ECU into thinking the engine temp is
colder than it really is and dumping more fuel in and giving more
power.
Steve Heath
Internet Mailing List Nov 96
On my 500, I measured the resistance at 600 ohms which is rather
odd and perhaps confirms my suspicions about it being wrong. I
felt it was too rich and my engine kept stalling at idle under
normal running temperature. My car is equipped with a variable
tune resistor, which I presume is for tuning to meet emission
regulations here. I turned it up to 1900 K-ohms and found that
it cured the stalling problem but noticeably more drive train
shunting, apparently typical of cat-equipped cars having to run
lean. I'm waiting for more feedback before I do anything further.
I would like to sort this and a leaky manifold problem out before
continuing my evaluation of Superchips.
Kenny Heng
Internet Mailing List Nov 96
I have called the factory and they have advised me, having consulted
with TVR Power, that the tune resistor value for the Griff 500
(which has a cat converter) should be 3900 ohms. This value is
exactly in the middle of the Land Rover specs.
I have adjusted the variable resistor on my car to 3900 ohms,
from 1900 ohms that was set before, and noted stronger exhaust
pulses. Now, the car does not stall at idle (normal running temperature),
the problem which started me on this. This leads me to conclude
that the reason for stalling was too rich a mixture. The idling
remains rough, rocking the car quite a bit. Subjectively, the
engine felt more eager than before to pull from about 3000 rpm
onwards. However, shunting at below 2000 rpm is more pronounced.
I am still curious as to whether the rough idling and shunting
are normal characteristics of the 500. Appreciate comments.
Kenny Heng