MG Midget Forum

Note on water temp gauge sensor:

A contributor on another thread notes that the head is the most accurate place to put a gauge sender--and of course that's right. But that's not possible with this conversion, given the OBD-I ECU's need for 'real time' readings from the head to manage warm-up and also mixture/timing adjustments with a hot engine.

Folks with a stock vertical flow radiator like the '67 test mule once had will have no problem, as they won't move the sender from the radiator's top tank. Those whose gauge sender was in the head and lack a bung in the radiator face my present conundrum.

I do not want water circulating through the heater core during summer, so the hoses to/from that are out. That leaves the top or bottom radiator hoses, or having a bung welded into the radiator near the inlet, as with the OEM radiator.

Radiator top tank - this is problematic with the dual-pass, Ron Davis cross-flow model on the '67 test mule, because the mounts are at the top sides. I could have another bung welded into the rear-facing surface next to the small one for the expansion tank hose, or use an adapter I already have to put the sensor in the top or bottom hose.

Top hose - (i) yields similar readings to the '67 test mule's stock setup, which placed the gauge sender in the OEM radiator's top tank adjacent to the inlet from the cylinder head; (ii) alerts driver to frozen thermostat, for if gauge isn't moving by the time (in my case) I turn onto the blacktop from the dirt road accessing the house, I know there's a problem.

Bottom hose - would measure temp after radiator, so reading would reflect efficiency of cooling system rather than hot water fresh from the thermostat. Also would require fiddling with existing hoses and adapter, resulting in even more hose clamps. Yuck.

I think top hose may be it.

Joel

This is fascinating, a very nice simple setup using tried and true parts. But far as a no tune? I only skimmed everything, this will definaty work best with a custom chip burned for it. Can I assume you have the software and chip burner? Cause while it may run and run ok-ish...the factory ecu didnt have all that much authority in its learning tables. And aside from that, adaptions (integrater and what have you) should really be centered for proper operation.

Im also curious too about this setup with a maniflow manifold. With the side draft webers, these motors make more and more power the longer the runners are. Very cool!

Hi, Mark.

Thanks for the enthusiasm and constrictive critique.

Of course you're right that a custom-burned chip would be best. I do have TunerCat loaded on the old PC laptop, which I saved from the junk pile just in case I want to get a burner and try that route. There's also the option of using a professional tuner I've visited with who is fairly reasonable. The former would take a l-o-t longer due to the learning curve and limited time I have each month for extracurricular; the latter would add cost to what I want to be the cheapest DIY EFI solution out there. Same motivation drove the rear disc brake project.

We'll have to see how far off the maps are--before and after supercharging, of course.

The third option is going Megasquirt II, as all components are compatible. Although that would make for a more expensive conversion and mean starting maps from scratch and pushing back the date when I could offer the solution to others, it would also allow me to provide DIY'ers with 1275-specific files (naturally aspirated and blown) on a flash drive. That is, if I'm understanding how easy it is to export and share Megasquirt driver files.

Joel

Megasquirt has come a long way thats for sure. I had an MS1 V2.2 car I drove for years. Tuning was the easy part, it was the dialing it in that was hard. Cold starts, warm and heat soaking hot starts, acceleration enrichment, etc etc. This was on a boosted application too. Its great if you wanna learn and tinker. But the nice thing bout that GM box and having someone burn a chip for you, is all of that hard work is done and burned in. Most likely all you ll have to change is the fuel and spark table and youll be golden. Starting regardless of temperature, altitude, idle control, its all done and wont need adjustment (most likely) in that stock box. In the MS, those are the things no one thinks about, and its the stuff that IMO makes or breaks a setup. If it doesnt fire when I turn the key and run by itself, if its fussy and cold blooded, what was the point ya know? The whole point of EFI is it will start quickly, easily, always idle correctly and just work under any temperature and condition. But thats just me, haha

Mark - yes, that was the thinking behind this OBD-I conversion.

I intend to proceed like this: (i) test my hypothesis as set forth in post no. 1; (ii) if necessary, explore tweaking this chip, as I've got the broadcast code and can always order another from GM or Autozone; and if that's a bust or for reasons of file exportability and expressions of end-user preference (iii) shift to Megasquirt II, install an Innovate Motorsports 3844 MTX-L Complete All-In-One Air/Fuel Ratio Gauge Kit with the tuning sensor just ahead of the muffler, plug in the laptop, and roll up my sleeves.

Joel

Here is the setup for the OEM gauge sender. Had to drill out the teensy hole it had with a 37/64" silver & deming bit for the NPT tap. Quite a mess, but it should work.

I'll have to revert back to the old vertical flow radiator thermostat neck, and get two 90 degree hoses cut to length to finish things up.

Joel

Also relocated the IAC valve to a simple aluminum bracket that uses the OEM screws holding on the pedal box cover. Much neater and shorter hoses, too. Then installed the fuel pressure regulator with gauge.

Finally, here's a shot of the air cleaner, which you can see I (finally) clamped into place. Neat thing about this setup is not just cool air vented from behind grill, but it doesn't contact the bodywork anywhere, so no rattles!

One reason I relocated the IAC valve was to make room for the '90s Subaru EFI-spec fuel filter, which will go below and just aft of the regulator, in front of the throttle body, kind of--but low on the inner fender well sheet metal (last pic). The bracket has a quick release clip for easy change-out. Cost $5 at the pull-n-pay. Subaru still sells the rubber bushing (not pictured), which keeps the filter snug in the bracket. I bought a Fram filter which was cheaper than Subaru and still decent quality.

Joel



Edited 2 time(s). Last edit at 2017-07-04 05:23 PM by Yankeedriver.

Okay, all fuel system components installed under the bonnet and boot; just need to link them together. Here are photos of the installation of the '90s Subaru fuel filter and bracket, which has a nifty quick-release tab as I'd mentioned. The filter was $9.00 at Autozone; Chinese copy of the Fram but still EFI spec. Goes in and out very easily, without skinning knuckles and the like.

The photos really don't do the setup justice, but it's really pretty tidy and roomy on the exhaust/intake side of the engine bay compared to carburetors with heat shield. I could have done an even neater job with the hoses, but they really aren't bad. Of course, EFI spec 5/6" hose is used from the filter to the throttle body, and thence to regulator; regular 1/4" fuel/evap hose is fine for the return OEM line to the swirl tank in the boot, as there's very little pressure in that line, since overflow from the swirl tank goes into the Spridget's stock tank via the filler neck (see earlier photos).

All clamps are EFI spec, which is not necessary on the return line, but they're nice clamps.

The stainless line and aluminum AN fittings go in later today or tomorrow, and I'll be able to do a pressure/circulation test on the car, rather than mocked up as I'd done before. The fittings you see include one grouping to adapt the steel line to another short run of 5/16" EFI spec hose to the input side of the fuel filter. This is starting to get exciting to finally get this done!

*Oh, sorry - the capped-off lines from the swirl tank are for 1/4" fuel/evap hose. One receives fuel from the OEM 1/4" delivery line--now used as a return, which you can see in the engine bay photo, coming off the regulator's bottom output nipple. Nice short, straight ~7" run. The other receives fuel from the stock fuel pump (or aftermarket Facet, in my case), whose only job is to lift fuel from the OEM tank into the swirl tank.

Neat thing is, none of this conversion require removing the engine or fuel tank. You saw in an earlier post that the swirl tank's overflow goes into the OEM steel filler neck.

Joel



Edited 2 time(s). Last edit at 2017-07-08 11:39 AM by Yankeedriver.

I had earlier shown in post 37, in the air cleaner clearance photo, the output end of the cool air intake--stealth, as it's fed from behind the grill. I couldn't use the racer's method of feeding from a headlight socket, as this is a street legal car and we've got deer and coyote on the two-lane black top from the freeway. Need those Hella halogen lamps when blasting along the twisty road at night!

Here is a view of the intake as seen from the wheel well.

Joel

Here is the cable connector I found, which is used on lots of Beetles, Karmen Ghias and Micro Busses, and costs $1.00. The local aftermarket VW place had them. But you can get them from www.autohausaz.com as well.

There were a few adjustments needed, apart from clipping the cable, slipping it into place, reclipping, etc. a few times to get the length right. There's zero clearance for extra cable sticking out to insert the barrel nut, so you have to get it right--but that's not hard. Took three tries and just a few minutes. Of course, you can also vary the cable housing length to adjust tension.

First, the O.D. was slightly larger than the1/4" hole in the cable cam on the Hitachi throttle body, about 8mm, so I enlarged the hole to 5/16" (with the throttle body still mounted on the car), wiggled the bit around a touch, and she slipped in.

Second, I think the old VW throttle cables were considerably thicker than the universal bike brake cable I've been using on the Spridget for years. Also, they're used on the heater box actuation levers on those vehicles, and those cables may be solid rather than braided as they have to push as well as pull. So, I had to remove the bolt and file down the top a smidge so the bolt would extend farther into the cable's hole and grab the softer, braided bike cable. Another couple of minutes.

Third, I cut a slot into the aluminum cable bracket I had made, which greatly eased cable installation: open throttle, insert barrel nut, slip cable into cam, slide cable through slot in bracket, insert guide tube into bracket. Easy-peasy... and no more ruining cables when R&R'ing the intake--though this setup is designed to be maintenance free (I didn't maintain the throttle body once on my '98 Subaru, which had 250K on it when sold last month and ran like a champ).

Finally, I decided I did want a little more snap on the throttle return. So, I made another bracket that bolted onto two unused bolts on the throttle body and added another spring. The pedal now has a light pull but a very snappy butterfly closure onto the throttle body's stop, and WOT at the butterfly is consistent and easy.

Joel



Edited 3 time(s). Last edit at 2017-07-08 09:02 PM by Yankeedriver.

Finished the fuel system this morning. Took 4.5 hours.

The main goal was to have an unbroken, single stainless feed line all the way from the hi-pressure pump to the engine bay. Mission accomplished. Physically, the most demanding part of the entire conversion. Glad the shoulder was rebuilt recently, as bending stainless line under the car is not easy. My kingdom for a lift...

This post is largely pictorial, and I hope it's useful to whoever wants to go EFI or forced induction (regardless of carbs or EFI), since you need a separate feed and return line for either application. The main innovation here is that the tank is never removed or pierced. Instead, the overflow from the swirl tank goes into the OEM steel filler neck. The OEM 1/4" line becomes the return line, and is more than adequate to ferry excess fuel back into the swirl tank. From there, any overflow to the OEM Spridget tank goes out the top of the swirl tank through 3/8" hose to the filler neck.

I included photos of a template I made for two short pieces that link the OEM (or aftermarket) low-pressure pump and old feed line (now the return) to the swirl tank. They are made from 18" pieces, retaining the natural curve of the coil, which closely approximates the arc of the axle arch. These may be useful to folks.

Oh - and there is an OEM grommet for something I'm unaware of, right next to where I put the hi-pressure pump and swirl tank input lines (from 1/4" return and from OEM or aftermarket low-pressure pump). Perfect for running wire to hi-pressure pump, if I want that lead to go under the car rather than inside. Last photo.

All I've got to do now is finish wiring up the sensors, convert the Lucas distributor, and fire the thing up--but that'll have to wait for another weekend. I'm bushed and the 'honey do' list awaits...

Joel



Edited 2 time(s). Last edit at 2017-07-09 03:17 PM by Yankeedriver.

Looking good Joel , can't wait to see this thing running!

I like your return line solution. I was considering putting my swirl tank under the hood, but your solution has me tempted to reconsider.

Thanks, Steve. I've been inspired by all your hard work - and dearly wish I had your welding skills.

Joel

I understand this is an attempt to make an affordable and DYI installation, but I was wondering if you priced a custom tank that would eliminate the need for the swirl pot and intrusion into the boot space?