Rattling Exhaust

My exhaust has never been the quietest, but recently it has developed a very loud rasping rattle at revs above 3000. Rather than the sound of a purring engine as you pull away, you have the sound of a rattling tin can - not good.
I went up to GBS last weekend and saw Richard@GBS. He said that occasionay the inner sleive within these new single can exhausts, can move backward and rattle against the rear of the outer casing. He gave me a few stainless rivets and told me to place a rivet about 2cm from the seam and somewhere that can't be seen. This should stop the inner sleeve moving.
Well as you can see above (photo taken from below), I have done this and the awful noise is still there.

Update: It helps if you position the rivet in the correct place. I missunderstood the instructions. The rivet should go about 10mm along the tail-pipe section from where it meets the can. Having done this the rattling stopped - not altogether - but much better. Perhaps another rivet will completely fix it, but I am loathe to keeping drilling holes in an expensive exhaust pipe to resolve a GBS design problem.

Pre-Nurburgring Training

Although I have attended a couple of GBS Track Days recently I have never actually taken the car on the track. But this is going to change on 3rd June 2014 when I have registered for a track day at the Nurburgring with GBS and their German distributor. 
The day is a closed session (no public admittance) arranged by the German Pistenclub (pistenclub.de), so I have 8am until 16:30pm to do as many laps as I like along with 100 other cars.
As this is the first drive on a track for many years, I decided to get some professional help to brush up my technique and help me get a feel for my car at track speeds. If you were at Stoneleigh the other day you may have noticed a company called GEM Driver Training ( gemdrivertraining ). I noticed them in the magazine literature because they use an airfield close to me in Stafford. 
Last Sunday I did their Track and Performance Driving Course. I can recommend it for anyone in my position. I wanted to understand some of the theory behind how a car handles on a track, and also brush up my track driving skills. Ewan Morris does an excellent job talking though car dynamics with the aid of some powerpoint. 
He really understands what he is talking about as he has many driving teaching qualifications and many years of race experience. The session was not just theory either. We started in his Rover with some basic assessment and track orientation, but then I arranged for 1:1 tuition in my Zero for 45 minutes. Time to put the theory into practise. It was just what I needed. I now feel safer and more capable of enjoying a full day around the "Ring". Thank you Ewan!!


Here's his Facebook link GEM-Driver-Training

IACV Removal

As I have mentioned in several previous blogs, I have never been happy with the operation of the IACV. I believe the car only starts and idles because of two opposing problems: the first is that the IACV was wired back to front so even though it is turned off in the ECU it still remains circa 70% open when the ignition is on; the second is the diameter of the pipes leading into and out of it physically constrain the air flow. Together, these issues allow just sufficient air to the plenum to allow the car to start and idle (albeit very fast 1250 RPM warm idle). If I am right, then there is a third unseen problem. The airflow via the IACV is constant and un-metered, which means that the engine will be running lean.
The proper answer is to install the IACV correctly along with a Lamda sensor and run closed loop, but I haven't the time or inclination to do that at the moment since I have registered for the GBS Track Day at the Nurburgring in 2 weeks time. My priority is the get the car operating in the most reliable and predictable fashion ready for the trip to Germany. So I have decided to remove the IACV and revert the idle control to a simple throttle stop on the butterfly.
As you can see from the photo, it is quite a straight forward process to remove the threaded lug and replace with a standard bolt and a couple of nuts to lock it into position. The throttle can then be re-installed on the end of the plenum.
The real work in this job isn't mechanical but it is in the trimming of the idle set-up in the ECU for warm idle and cold start. I found some instructions on the Emerald web site for trimming the warm idle:

If you disable the idle stabilisation function (as found in the "Idle control" page) and the overrun fuel cut off function (as found in the "Events" page) it will prevent these functions from hindering rather than helping while you initially get the engine fired up, throttles balanced and the idle set.
Assuming that the ECU is locking onto the crank sensor signal ok, then the main task is to get the engine fired up and up to temperature.  This may (will probably) involve holding the throttle open slightly while you adjust the idle screw to hold the engine at a sensible rpm.

The next bit is a bit of a juggling act - you want to make sure that the fuelling is somewhere right, so just use the fuel trim keys (2 & 3) in the "Live adjustments" screen to add or take away fuel so the engine runs as smoothly as possible.  

Once you're happy that the engine is running smoothly, the engine rpm is ok for a hot idle speed and the throttles are fairly well balanced, you can shut the engine off and re-align the throttle position sensor via the PC software.  Switch the ignition off/on (if you haven't already) just to ensure that everything (e.g. fuel trims) are cleared, and re-start.

You may still need to add/remove fuel to get back to the idle speed you had before, so it may take a couple of goes around the loop but you should be making finer and finer adjustments.  The fuel trim that you end up with that keeps the engine idling correctly will show you how far the base map is from what is needed.  You can change the overall fuelling but adjusting the fuel pressure or changing the MSPB value in the injector scaling screen (accessed from the "additional settings" menu) is a better solution.  Increasing the MSPB number or the fuel pressure will richen the map, and decreasing the MSPB number or fuel pressure will result in a leaner map.

If you make changes to the MSPB number, keep the changes fairly small each time, (say steps of 4 or less) and remember to program the map to the ECU for the MSPB value change to take effect - you can do this with the engine running.  The base map should get you most of the way there but the idle fuelling and very light throttle settings are most sensitive to injector/fuel pressure/engine differences so often require a little more attention and fine tuning.

Here is the link to the technical article on Cold Start Calibration.
Emerald_Cold_start_crib_sheet.pdf

Even though I am not an automotive engineer, following the process resulted in an engine that idles smoothly and starts without a problem from cold - albeit cold equating to 10 degrees at the moment. This may need some more work in the Winter.

Accelerator Pedal Stops

Another small job I have been meaning to do. The pedal position for the accelerator has never been where I expect it to be. Normally it should sit just below the height of the brake pedal so that your foot can move horizontally from brake to accelerator swiftly without having to lift your foot. It should then travel to 100% throttle open and have a physical stop to avoid stretching the accelerator cable. Having taken your foot off the pedal it should return to where it was just below the height of the brake. 
As you can see on the left I have used a small spring to aid the throttle butterfly spring in returning the pedal back up. Then an M4 bolt covered in nylon fuel pipe to act as a pedal stop. The right hand photo shows the pedal box to which the pedal stop in anchored. I used the bulkhead as the final stop for 100% open. Much better.

Unsightly Rust

 As you can see on the left, one seasons Winter driving hasn't done much for the front wishbone bolts. It's only surface rust and nothing that will affect the mechanical integrity of the car, but I don't like it. Now replaced with zinc coated ones that I have sprayed black. Much better

Doors

My Zero has been driving well since my last blog. Now well over 2000 miles on the clock, mainly from short blats around the local Staffordshire countryside. I've found a great route over Blithfield reservoir and up to Uttoxeter but that's for another blog.

I was disappointed not to be able to join the RhoCar crew on their trip around Scotland last week (  ). I was actually in Scotland on holiday with the family, so took advantage of the great weather over the Bank Holiday, but the photos and videos from the RhoCar guys looked superb. Maybe next time.

But back to the main subject of this blog: a new set of doors. The doors have been on order for well over 12 months now, but GBS' supplier seemed to be playing games. Promising new stock each week that never arrived. But they are here now. I had imagined simply taking them out of the packaging and dropping them straight onto the hinges - but were would be the fun in that? They come flat packed and without the hinges attached. The challenge is to bend them to the right shape to fit around the car whilst also positioning the hinges correctly so the doors open around the mirrors and the half-hood, as well as looking aesthetically reasonable at the same time.
Firstly I mounted the lower hinges on the Y-frame on both sides and installed the half-hood. Then I bend the doors into roughly the right shape. There was a helpful post from Simon@GBS recently on the GBS forum, where he explains how to do this (http://www.gbsownersclub.co.uk/forum/technical-talk/doors). I didn't follow it exactly, but it is useful to read though to acclimatise yourself with the complexity of the job. I have reproduced the text below as I am not sure if old posts will be archived on the forum.

"This could become complicated to explain, although relatively easy to do.

the first bend is to the mid bar approx 12 inches (I have never measured it) from the front, bend from the inside over knee. note this tends to bend the top bar slightly so reshape with knee so straight - this is to make the door follow the scuttle line.

The next is to the front edge of the door, approx at the mid bar, again with knee from outside - this produces the bend out for the lower front part of the door. Next a bit of shaping to the lower part of the front bar, again with the knee so that it follows the shape of the scuttle.

Fit roof, if you have one, fix hinges to screen brackets, assume you have holes drilled already, put door part of hinges into screen bracket part. Offer up doors to side of vehicle, align top part of front of door with screen bracket, also the top with the roof gutter, and check rear of door on rear wing, two pairs of hands make it easier.

Make sure the door frame will sit under the door hinge holes and mark the top hinge top mounting hole. Remove door, and door part of the hinge. drill marked hole. and loosely secure top hinge part, fit back onto vehicle, the front of the door will now hang on the fitted hinge, the rear can easily be held in position to check fitting against roof gutter, screen bracket and rear wing. mark one hole of lower hinge, drill and fix loosely.

On refitting door should hang roughly where required, NOT exactly because nothing is tight. check both hinge pins are fully down. you can now twist the rear of the door so the bottom bar sits against the side of the car and the top bar rest against the roof. when happy with fit you then drill and bolt the last two holes.

Place door back into position, take load off hinges by lifting rear of door, if you don't the door pins will be out of alignment and fitting and removal of doors will be trickier. tighten the hinge bolts. tweek door for perfect  fit"

And here is the finished result, although the anchoring straps to keep the doors closed couldn't be fixed because there were no poppers in the door pack. I will call GBS tomorrow. I am sure Will@GBS will drop some in the post for me.
A quick blat down the road and all is well - any excuse!!

IACV revisited

As I have mentioned in previous posts, my IACV has never really worked properly. It buzzes away to itself and allows the car to start and idle but I think this is a combination of a number of wrongs making a right: for a start it is wired incorrectly - to gnd rather than +12v and to the wrong pins. 

Some investigations today.....

Rewired right back to the ECU and double checked the wiring - all OK. Walked back through the set-up advice from Emerald: Wire one pin on the valve to an ignition fed +12v supply.  The other side goes to pin 3 (IACV Valve channel 1) on the Emerald ECU.  In the PC software go to ECU Configuration and "Idle Air Control Valve motor options" and select 300Hz as the PWM value.  If the configuration has to be changed then click the OK button and reset the ECU by switching the ignition on and off.  Read up the map from the ECU and go to the "Idle Control" tab - press F5.  Select “motor control mode” in the top right hand corner of this screen.  Set the mode to “Fixed position manual control."  Re-program the map to the ECU.

From the "live adjustments" tab (F8), and with ignition ON, engine OFF, use the page up/page down keys to alter the motor setting.  The valve is, in effect, an air injector so you should hear the motor buzzing as you increase the IACV position above about 20%.  Note that the valve will not work at very low settings or very high settings - the normal operating range is between 30% and 70%.  You can test this before starting the engine when the valve noise should be very obvious.

Everything behaved exactly as per the above - thought I had finally cracked it....but.......with the engine fired up (cold) the IACV had no effect on the idle regardless of the position (0% through 100%) which remained stubbornly at c 1000RPM. 

• With my finger partially over the inlet pipe it showed that air was passing through the value - I could hear it and feel it and the engine revs dropped accordingly. 
• With my finger completely over the inlet pipe and the engine cut out, so no air leaks into the manifold.

Then I removed the pipe connecting the IACV to the manifold and allowed air directly into the manifold via the pipe i.e. no IACV at all. The revs jumped up to 1200RPM. This looks like the problem. There is simply not enough air being allowed through the IACV due to the diameter of the inlet pipe and bracket. Surprising since this was a GBS design. 

This diagnosis is also supported by that fact that RichardL has his working by connecting directly to the Plenum chamber i.e. no pipes or brackets to restrict the airflow.

So what to do? - not sure. I don't particularly want to remove the manifold to fit the IACV, but I may have to. I'll think on it.