6 September 2009
Session 309 - Tow vehicle and trailer
My son is an avid off road fan. For the past for few years he has been using friends rides. I need a tow vehicle, so we put in 50% each and bought a Land Rover Disovery, yes its a V8! Believe it or not this whole vehicle complete with a tow bar was cheaper than a profressionally installed removable towbar for my BMW! The trailer was a purchase off Ebay! Its custom built but very solid twin axle braked trailer. Tyres have plenty of tread but the rubber looks a little old. Going to get some new tyres soon. It's load area is 6ft wide by 12ft long and it is just about spot on for the westfield.
Photo showing westfield just before unloading onto a private lane for some test runs.
Did a number of test runs. Lane not that long and it was rough concrete with grass down the middle so didn't go above 50mph but god it gets to 50mph very quickly. Took my son as a passenger and the skin on his face was pushing back to his ears! Logged the session from the ECU and used to perform some analysis. I shall use the analysis to adjust the fuelling. The fuelling is running a little rich under load. The exhaust note was great but not as long as those sidepipe V8s you hear. The induction noise from the filter was superb though. Each gear change resulted in a growl of air being inducted. The power delivery from start is not really smooth but that is down to my 1-1 pedal to throttle linkage but once underway its awesome. The revs come quick not what you expect from a V8 but this is a light car and I have installed a light flywheel.
7 September 2009
Session 310 - Analysis of tuning data
I logged the engine/ECU data of the runs that I performed yesterday. As I said I can use these data to do some tuning of the engine. Before I did the runs I did adjust the fuelling requirement and the fueling table. The fueling table is known as VE table 1. I basicailly adjusted the cylinder base fueling requiement down and adjusted the VE table up by the proportionate amount. Why? well the fuel requirement I found by gradually changing to get the optimal fuel mixture at idle. Problem with this is that there's a standard calculation to determine this based on the fuel injector flow rate and engine capacity and I want to use this as the base fuel requirement. Using the base fuel requirement may make future upgrade easier, for example if I decided to change the fuel injectors. Also makes comparing fuel tables with other setups easier.
Below is shown the fuel requirement that I had been using before the test runs above.
Selecting the calculate fuel requirement shows the box below. As you can see I entered my details, engine capacity 4.6litres, 8 cylinders and the injector flow rate of 231cc/min. Also the ideal air-fuel ratio of 14.7 or lambda 1.
Accepting the values above sets the one cylinder fuel requirement of 8.3ms.
I scaled up the current VE table 1 by the change, i.e.multipled by 11.3 and then divide by 8.3. This is shown below.
Now for the tuning analysis to work you need to have populated the air-fuel ratio target table. Below is the current AFR target table.
These AFRs are not optimal for the Rover V8, close. Done some research and found the AFRs shown below.
I warmed the engine up before the runs yesterday on the above settings and found the AFR at idle was a little on the low side. low AFR means too rich so I tweaked the fuel requirement down a bit and found 7.8ms was about right. Actually a little lean, the Rover engines actually prefer a rich mixutre of AFR 13.5 but that would not pass the emissions on the IVA test. I can always tweak this up a bit later if so required. This fuel requirement gives an AFR around 14.2.
So now that my base fuel is setup and my AFR targets are completed taking my log files from yesterday I can analyse the log files with a piece of software called megalog viewer and re-calculate the VE1 table. Below showing the analysis being performed.
Accepting the changes above produces the new VE table 1 below.
I haven't actually downloaded this to my ECU as my testing was just up and down the small lane and this would cover no where near the amount of different loads, speeds etc to map the entire fuel map. If you look at the values you can see the places which have been missed, I guess this could make the response a bit lumpy.
I later looked at the logs in more detail and can see some spikes where the fuel mixture went very lean. After about five minutes thought I could see the pattern, low load, throttle position closed and I could see this was happening at the times where I would be braking to come to a stop. This is overrun! I made some enquiries and it is safe to go lean on the mixture when engine not under load .
However Troy from Northampton motor sport said
"
The problem I find with many overrun cut off strategies is that you always get a pop as the fuel switches back on and during certain driving conditions such as picking up the throttle out of a downhill bend you can get a dead spot before the fuel kicks back in. This is only really noticeable when driving gently not hard.
On the dyno I will drive up to close to max rpm in 4th and then back off letting the engine braking slow the rollers. By watching the afr I tweak the fuelling to give between 14.5 and 13.8. This stops all the popping and gives a really smooth clean progression from trailing to leading throttle.
ps running lean on overrun wont hurt the engine "
Once the car has passed its IVA checks I am going to book a session with Northampton Motor Sport to get the suspension set up correctly and tune the engine more scientifically on the rolling road. Will be good to see how much power she makes.
Latest megasquirt .msq file with the above changes is here.
11 September 2009
Received my final vinyl today
This weekend's small project is to strip my new trailer down and re-paint hammerite black. So I spent the rest of today stripping all the bits of it, lights, wheels, etc. I then washed it, washed it, and washed it again to remove years of mud from underneath. Then tomorrow, saturday I shall star the project proper.
12 September 2009
Started at 10:00am. Wire brushed the trailer all over including underneath this is a very messy job. I definetely look dirtier than the trailer! This process took me about 5 hours and the trailer is not that bad. I then swept up all the rust from the floor, all 2 kilos of it! I washed the trailer again paying particular attention to removing all particles from chassis underneath. By the time I had finished is was about 3:00pm. I tried the trailer with some rags and left it air dry in the glorious sunshine we have today. 2 hours later it is dry enought to comtemplate painting. I am ahead of plan I wasn't expecting to start painting until tomorow.
I actually put in 5 hours of painting, I would have gone longer but it is 8:00pm and getting dark! I have completed one coat over about 3/4 of the trailer.
13 September 2009
Started at 10:00am again today. I worked right through to 8:00pm.That means I spent 24hrs this weekend on this. I be glad when I go back to work for a rest. I ended up painting 2 coats of hammerite all over. Almost got away with one coat, typical.
Photo of conmpleted trailer. The ramps not installed they are leaning up against the tree in my front garden drying. I have left the wood flooring at the top of the trailer off. Going to some fresh stuff.
Bottom left of the picture is one of my cats. She has been hanging around this all day making a nusiance of herself!
30 September 2009
The old Rover V8 engines as used in the likes of SD1, TR8, etc used a 74degree thermostat equating to an operating temperature of around 80degrees which is just about optimal for the internal combustion engine certainly higher than this reduces power output. Apparently if the engine reaches 100degrees centigrade then power is reduced by 10%!
On the later V8 engines as used in the Range Rover 4.6 Sport/HSE, etc. Rover changed the thermostat to 88degrees which leads to an operating temperate of around 95degrees. Why? Well engine emissions are reduced at this temperature but as discussed above to the detriment of power! It was also noted by many enthuiasts that as this time when Rover changed the engine operating temperature that engine blocks began failing with cracked blocks. So it would seem that this increase in temperature was to the detriment of reliabilty also.
For this reasons above I decided to address this before it comes a problem for my much loved engine. This modification involves getting hold of one of these older thermostat by order a TR8 one. Never simple, one of the modifications Rover made to the later thermostat is a bleed hole and we want this! So to do this using a pillar drill, drill a 4mm hole in the middle of the flange of the thermostat. It is important that this hole is installed so that it is at the top. This simple mod means that trapped air behind the thermostat can escape. Without this it is possible that the thermostat will not open at all! This hole also means that this is always water circulating through the coolant system.
I started the engine which said it was at 15degrees. It took about 15minutes to reach 87degrees. Previously this took 9minutes. At this point the fan came on. I kept the engine running to see if the temperature stopped rising. The temperature began falling slowly. Being satisified at this point I simple turned the engine off and checked for any leaks.
Dyno time
I am booked into Northampton Motor Sport this friday for a tuning session. I was going to do this after the SVA/IVA however I need to get the emissions down and make sure it does not go to rich otherwise the cats that I need to install could be damaged.
Go to October 2009