festy's Alfa Romeo Alfetta GTV

[festy]

I haven't updated my delco conversion thread in almost a year - I haven't made much progress with the car in that time, and what I have done hasn't really been EFI conversion related anyway so thought I'd start a new thread here.

Cliff notes on the conversion: I bought a parts car about 15 years ago but decided to track it instead of scrapping.
I took it out a few times before deciding I wanted EFI.
Then I parked it and 10 years past - until one day I found it hiding in the back of the shed, and stumbled upon this site.
A few months, a hand full of stuff ups and a lot of home made parts later, I finally had an EFI'd Alfetta.

It's still not ready to take to the track yet, but I'm slowly getting there...

First thing after getting it running on the Delco was the suspension.
While fitting some stiffer rear springs, I found that the Watts link setup was going to need all new bushes - so I cast an alloy center pivot block and made up a pair of adjustable arms fitted with spherical bearings.

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I installed a heavier front swaybar, and replaced the pressed-on link arms and rubber bushes with spherical bearings.
This needed the bar ends to be drilled and tapped, which was a fun job...

ARB_link.jpg (143.17 KiB) Viewed 8053 times

While removing the front torsion bars to fit an uprated set I found that the lower control arm bushes were in a bad way - with the torsion bar removed the arm flopped around everywhere.
After I pressed the bushes out (they're actually spherical bearings from the factory) here's what I found:

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That's not a grinder cut - it's from the outer race wearing away the inner. There was a matching groove worn into the pivot axle:

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While I was sorting that all out I rebuilt the front calipers. I spent a week cleaning the caliper bodies and pistons, just to find when I went to re-assemble them that the small internal o-rings are NLA
After weeks of searching I eventually tracked down some in the correct size and shape, as used in a 70's Kombi caliper.
The brake hoses had seen better days, so they were replaced with a set of Goodridge teflon lined braided hoses when the front suspension was reassembled.
A NOS brake master cylinder was fitted, and the clutch master was rebuilt. I also replaced the bolts that hold the lower control arms to the body because they were all bent
The wheel bearings were re-packed at the same time, I was going to fit a new set but these ones looked brand new. Mabye I replaced them a few years ago? I can't really remember...
While it was all apart I also replaced the steering rack with a good spare. I vaguely remember the front wheels flapping madly at speed last time I drove the car and the rack definately had some play in it, but I don't think the lower control arms would have been helping

front_suspension.jpg (65.09 KiB) Viewed 8053 times

Not much suspension travel there now, I might have to modify the bump stops a bit

[festy]

Here's a before and after pic showing the ride height change:

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[festy]

I knocked together a new switch panel - not fantastic, but better than the bent PC case that it replaced

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Finally got around to removing the distributor, but needed something to plug the hole so came up with this:

dissy_plug1.jpg (204.08 KiB) Viewed 8048 times

installed:

dissy_plug2.jpg (187.67 KiB) Viewed 8048 times

And for an interim solution to mounting my knock sensor, I made a new brass coolant drain plug:

KS_drainplug.jpg (100.5 KiB) Viewed 8048 times

I'm using a Saab knock sensor at the moment because I gave my flat nissan style one to Mrfiat the other day. I'll replace it when my new sensors arrive but it will do for now.

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[festy]

My rear swaybar bushes were falling apart, but I don't think they're replaceable. The two halves of the metal sleeve are peened together, so I assume you're meant to replace the sway bar when the bushes get old.
I got hold of a slightly heavier bar, but it's bushes were almost as bad as mine:

rear_sway1.jpg (74.83 KiB) Viewed 8043 times

I couldn't see a reasonable way to convert the linkage to use rose joints, and I wasn't having any luck sourcing replacements so I made my own poly bushes.

This stuff is a nightmare to machine, and left my lathe looking like Miss Piggy took a dump on it:

poly_bushing.jpg (90.84 KiB) Viewed 8043 times

But they worked out pretty well I think

rear_sway2.jpg (84.93 KiB) Viewed 8043 times

I haven't installed the rear bar yet, because that involves just about dropping the gearbox out

[Holden202T]

nice work there man

[festy]

I've been thinking about cheap options for logging suspension travel over the last few days.
Proper shock pots cost an absolute fortune - more than the car is worth.
Two possible DIY options are string pots or linkage pots - both using normal garden variety linear potentiometers.

With a string pot, the potentiometer is mounted to the car's body with a pulley fitted to it's shaft, and a thin cable is fixed to the pulley and the lower control arm. A tensioned spring acts against the cable. It's very similar to a throttle body with a cable opening and spring closing it.
The resolution of a string pot is pretty good, but the idea of cables and springs everywhere isn't very appealing.

A linkage pot is just a potentiometer mounted to the car's body with a short arm fixed to the shaft perpendicular(ish) to the suspension plane, with a rod linking the arm to the lower wishbone - similar to a drag link steering setup or a carby throttle linkage.
The drawback with this is that you only get about 45* of rotation on the potentiometer, so resolution is not as good as a string pot.
With the linkage set up for +/-100mm travel you'd be lucky to get 1mm steps with a 10 bit ADC - but I'm sure I could live with that.

While I was weighing up the two options I remembered I had a couple of cheap ebay ultrasonic displacement sensors I'd bought a while back, so thought I'd see if there was any way I could use them instead of pots. These are similar to the ones used for parking sensors.

I put together a quick circuit to try one out, and the initial results look promising.

sensor_test.png (369.82 KiB) Viewed 7981 times

It seems to pick up the tyre well (I wasn't sure if it would work too well with rubber) so mounting the sensor in the top of the wheel arch pointing at the tyre might do the trick... but the sensors probably wouldn't last too long being in the path of road debris so maybe pointing at the suspension arm might be a better option.

Here's a quick and dirty plot of me testing the sensor, I was expecting to need to apply some filtering and averaging to the data but it looks surprisingly clean... except where I dropped the sensor at the end of the graph
The sample rate here is roughly 5Hz

suspension_travel_test1.png (16.64 KiB) Viewed 7981 times

I'm not sure whether these sensors will provide accurate enough data to be of much use, but I was able to get to within 1mm resolution at around 100mm so I think it has enough potential to be worth exploring further.
Mainly I'd like to be able to detect bottoming or topping out, and compare left to right sides through corners to gauge the impact of suspension changes so the accuracy of the actual figures isn't as important as the repeatabillity.

[bldnut]

try the wreakers for cheap linkage pots look under statesmans and fairlanes (NF and up) that have level ride suspension in the rear (these have 1 pot in the rear) or v8 toyota soarer and Galant GSR that have the adjustable suspension (these have the pots on all 4 arms)

[festy]

Thanks, I'll check them out if the ultrasonic sensors don't do what I need.
The only OEM sensors I was aware of were the Land Rover D3/D4 ones and they're anything but cheap
These ultrasonic sensors cost about $2 per corner and don't require any linkages, cables or mounts - which is why I'm trying them first

[Holden202T]

wow that's pretty cool

[antus]

Excellent idea. I'll be watching your progress with this. I was thinking about the same thing at a race meet on the weekend. I setup a gopro to watch the suspension travelling, and the results of that are here: https://www.youtube.com/watch?v=8osDp7PyhQk I left it running back through to parking the car to see what it did on the gravel as well as the track. Im pretty happy with how it looks, but theres nothing like logs on all wheels.