MG Sports Cars

That is one scary Piranha! Plan to pump up those air bags a wee bit?

That looks like a nice meal for a speed bump! How tall is your radiator?

I've upgraded the air pump and plan to add a reservoir and solenoid valves so I can get fast ride height changes (and no Carl, I won't be "hopping" it). Yes the spoiler is a smidgen low but once the car is leveled a bit I think it'll be fine. The radiator is 17 x 32 if memory serves, same as in the MG-Roadmaster but mounted nearly 1" lower to give room for the A/C and I/C condensers stacked in front of it. Right now I'm working on the tilt/trim pump (old style Mercruiser) which will power the bonnet lift cylinders. Haven't any of you guys messed with the pressure relief valves in one of those have you? It looks needlessly complicated, with 3 internal and 1 external adjustments.

Still work to do on the spoiler actuators too.

Jim

So I've been working on the hydraulics. No, not the brakes, the lift system for the bonnet. You may recall that I had an old left over Mercruiser Tilt/Trim hydropack which I cannibalized and stuffed into the passenger's side dogleg in the trunk behind the rear tire. For the past week I've had that on the bench sorting out the pressure relief and valving. I made a new external port block and have replaced the internal springs with lighter ones and am now down to 500psi open and 400 psi latching pressures (the pressure is maintained on power off). That's still a little high for my cylinders, I think they are rated for 250 but the #2 lines will be a restriction and my best approach may be to add a pressure relief at the front so I can control the opening and closing rate with the line pressure and then limit the final pressure at the cylinders. But that sounds overly complex and it might be better to just lower the output further and see how fast it operates. The good news is that there is now a cylinder available that is rated for 1300psi at a reasonable cost, so if performance is disappointing I can upgrade.

Is this getting me any closer to Indy? Well, sort of. Having the bonnet lift and the wing attitude adjust working is not as important certainly as tuning the engine and transmission controllers, but then again, I'm not going to drive the car any distance with the wing set to full downforce, and I just simply *want* the bonnet lift to work instead of continuing to raise it by pulling on the front edge of the blower cutout. The grille obviously was necessary to protect the radiator, and so the bumper could be mounted. Unlike some, I'm just not comfortable without them, sometimes I nudge things. (Just fair warning, I don't generally do it intentionally.)

With a little less than 2 month left I feel pretty comfortable that I can make it and will if I can. But if the car isn't quite ready to travel, at least the trailer has new tires.

Jim

Great news! Sounds like the list is getting shorter. Can't wait to see you and your car in Indy.

Capt'n

Quote:

With a little less than 2 month left...

Geez, my math is a little more optimistic!!

78 days, Jim. ;)

Really? I never was good with calendars. Wow, what a relief! I might even have time to install the new air pump...

But before that I suspect I'd better get Lance started on the code mods for the tranny controller.

...and then there is still that oil leak to track down.

I want to thank you guys SO much for giving me this extra time!

Jim

You're Welcome Jim, I can not think of anyone more deserving than you,"piece of cake" :-)

So... it isn't looking good for Indy at the moment. I just spent the last week or so putting in the hydraulic plumbing for the bonnet lift and am not real happy with the results. At low pressure I got nada. So I bumped the pump back up to about the original settings, in this case 2500psi on latch and 2000psi on lift. At those pressures movement was still slow but acceptable, but the pump kept cutting out. Then completely unexpectedly I blew out one of the lift cylinders. Cheap junk anyway right? The baffling thing was that it blew the shaft bushing clean out of the body! Now how the heck does that happen when you're pushing on the other side of the piston??

So I ran some pressure checks. Turns out that #2 line is WAY more restrictive than I counted on, and pressure buildup just from the return line restriction was around 1500psi when I made a loop at the front and connected the gage up there. Well clearly that won't do.

My first thought was to just order up a pair of higher pressure wing cylinders, after all the ones that run off the PS pump are rated for 1300Psi and should work OK. But NO! My cylinders are 8" and the shortest ones available in the higher rating are 10". RATS! (Maybe I can get a pair of "specials"?)

So I ordered 50' of 3/16" Ni/Cu brake line. Guess I'll rip the 1/8" stainless lines back out and make 'em bigger. Mo' money, Mo' time. Hey, it was worth the experiment anyway, but that 1/8" line is just too small. Who'd a thunk it? Sure was fun to run such itty bitty line though.

I'm better off not working to a deadline anyway. Besides, I've got a snow blower to build. That has to be done before it snows again... ACK!! Another DEADLINE!!! YEESH!!

As for Indy, I expect we'll hop in Matt's car and head up. If the MG is far enough along we might trailer or flat tow it but I'm pretty sure it won't be ready to drive that far.

Jim

Any progress to share on the car this weekend, or are you guys going to just focus on the chump car?

We did exclusively work on the racer and I've some photos to upload to that thread later, but I can also do a progress update here as there have been some new developments. First, I was able to get some high pressure wing cylinders for the bonnet lift. I called KSE and it just happened that they had done a run of 18 units to fill an order from Australia and I was able to piggy back onto that order. So I now have a set of their 1300 psi rated cylinders mounted. I was able to adjust the hydropak down to about 900 psi and now have it mounted and plumbed with 1/4" line all the way up to the bulkhead connectors at the cylinders and was waiting on more fittings to add the last 4 short lines. Then I'll be able to test it and provided that works as expected I can then run the control wires and install a switch. At the same time I ran new lines in NiCop and stainless for the air bag front suspension. Starting from the bulkhead fitting by the compressor I have 3/16 NiCop line running to a quick disconnect (for aux air and aux filling) then to the front crossmember where it transitions to some 1/8" stainless line. The 1/8" line is wound into a pair of springs which lay next to the lower control arm pivots and connect to the air bags, allowing for suspension motion while plumbing all the way with high pressure hard line. Another 1/8" line runs inside to the gage. It's now been pressurized for 3 weeks and the gage reading hasn't dropped. In fact the only variations I've seen have been both up and down and are attributed to the ambient temperature. Since bag wear has been a concern with these installations I have lined the recess in the crossmember with a thin teflon sheet bolted in place. The small line also acts as a restriction against air flow from one side to the other during cornering. Once I have the new pump plumbed in and electrically connected I will locate another switch to operate it somewhere in the dash.

Then there is the wing plumbing. Recalling that the car now has IRS, the wing control is more complex than a simple link to the differential and the motions of both sides of the suspension need to be averaged into the wing angle of attack. To do this I'm using a motion cylinder on each lower control arm and a wing cylinder on each wing support. The motion cylinders are plumbed together and then to the wing cylinders, with reservoirs to handle expansion and I have a small electric peristaltic pump to control the wing angle. I've been working on mounting everything and should get back on that tomorrow. As of now I have the motion cylinders mounted and have all the fittings on hand so it should go pretty smoothly, though I do not know how much pressure the small pump will tolerate. I'm thinking probably not much so it should be interesting to see how well it all works.

That leaves the intercooler pump and plumbing for the next job, but soon I hope to be able to get back to tuning the engine.

Here is a photo of the upper motion cylinder mounts:


Jim

Word on the street is that Jim has a new development on the B.....

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Edited 1 time(s). Last edit at 09/02/2015 05:13PM by BlownMGB-V8.

Very nice!

OMG it's a Transformer!

That is very cool!!!

Wow! The Mad Scientist in his lair!

I've made a bit of progress.
Most recent has been work on the wing. Because of the IRS I had to redesign the actuating mechanism. In doing so I needed something that would combine and take the average of wheel movement and convert it to wing movement, and a mechanical linkage seemed way too cumbersome given that the wing is mounted on the trunk lid which has to open normally. So I went to hydraulics, which makes the motion conversion easier and gives on-the-fly wing angle adjustment, but adds the complication of another hydraulic system, and which is a bit tricky in terms of pressure and balance.

So anyway, the use of hydraulics meant mounts had to be built into each of the side struts and to do that the entire structure had to be dismantled. The job cascaded, as they often do, all the way down to the strut mount cushions. While apart I polished and buffed all the stainless parts, buffed the aluminum aerodynamic struts and then anodized them to a burgundy that is a close match to the car color. Not perfect but pretty darned good for an amatuer. I just got it all back together except for the top mounts for the wing cylinders and some of the plumbing. I'll try to post a photo soon. Along with the rest of the plumbing I still need to build a 2 chamber reservoir and test the balance pump which is a small peristaltic unit I'm going to try. It will shift fluid from one chamber to the other to change the wing angle. The challenge is setting a static system pressure that will give the needed system stiffness without blowing out the balance pump. Amazing how tricky these things can become.

The other big development was that I trailered the car down to the annual Megasquirt Megameet in South Carolina last month, where we took it off the trailer and I had the benefit of a couple of experts setting up the initial parameters and evaluating the system. I learned a few important things from this. First, that my coolant temp sensor is not providing a reliable signal, meaning of course that while we had the startup settings working perfectly once the engine is warmed up, it will not do so well cold, until I have that problem fixed. They felt it was a grounding issue.

Grounding the Megasquirt system turns out to not be quite as straightforward as one might think.
The goal is to isolate signal grounds from output grounds and from all the automotive noises that travel back on the return path from every other electrical component in the car. Some of these components, (such as motors, ignition, and alternator) make a LOT of noise.

So here is the basic idea, and it can be used for the sound system as well: The MS has multiple ground leads coming off the controller. It is an easy mistake to tie all of these grounds to our chassis ground point. Instead, the idea is to isolate one lead and tie that to a ground lead that goes all the way back to the battery independently of all other grounds, Then use that lead to provide a ground for all of the sensors. You see what we are doing here? We are giving the sensors an independent path all the way back to the battery post. If the battery has double posts (top and side) even better.

The rest of the MS ground leads can be tied to chassis ground along with the ground strap going to the engine and this provides the ground path for all the outputs and carries all of the noise, thereby isolating it from the inputs. It's not absolutely perfect of course, you have a tie-in at the card junction between the grounds and also at the battery, but since all current flow not generated by the MS is now bypassing the controller power leads it will help a lot. And just maybe that will resolve my noise issues on the CLT temp sensor leg.

That is something I hope to resolve next week. Then it's on to checking the MegaShift inputs and outputs. Plus plumbing of course and then more tuning. After that, plumbing the intercooler, fixing the oil leak, and then the initial A/C plumbing. Still a ways to go, but at least it'll be driveable before too much longer and should be able to make the BritishV8 meet in spring.

Jim

Are the output grounds for a digital signal or are most of these simply a fairly consistent output ( such as temp gauge )?

If the signal is a fairly steady DC, you should also be able to series an inductor / parallel some caps, yes?