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MG MGB Technical - EDIS MAP or TPS

Hi,
Im going to be switching over to the Mega Jolt and Ford EDIS4 system. Ive gone through the archive and cannot seem to find any info on using the MAP. How unsteady is the vacuum at idle that there is a need to fit TPS, I would rather do what is stated http://www.autosportlabs.net/Choosing_between_MAP_or_TPS here in regards to having a small "reseviour" for the vaccuum pressure to stabilize it better. As they state that MAP is more accurate. Does anyone have further information as it would be greatly appreciated and also would be valuable in the future for others in the Archive.

Thanks,
James
JRB Mr

James,

This is an interesting point that you have raised. My advice depends on the induction that you are proposing to use;

If you will be using injectors or a fixed jet carburettor (Weber DCOE etc) then a TPS will give excellent results, the best in my experience. The engine ‘Load’ is determined by the difference between the actual engine rpm and the TPS position. Also some systems look at ‘rate-of-change’ of the TPS to determine the drivers’ intentions and can adjust the timing and fuel accordingly. Again the TPS will also indicate Wide-Open-Throttle (WOT) and Throttle closed positions, allowing for adjustments at these two extremes.

If you propose to use a Constant Depression carburettor (SU etc) then the MAP is the best option as it matches the operation of the carburettor. If you use a try to TPS on an SU carburettor it is almost impossible to interpret either the actual engine load or the predictive values.

The link in your post details a ‘small reservoir’ in series with the MAP sensor, in my opinion this is not required for SUs on a B-Series engine, almost all good EDIS systems will use a software filter to remove the pulsing that occurs at low rpm (approx 15Hz cut-off). The MAP sensor should be connected by a small bore ridged tube and have as small a volume as is practical so that the load can be determined accurately and more importantly quickly. Any reservoir will both dampen and delay the load sensing.

I hope that the above is of some use to you in your project,

Regards, Mike.
MG Mike

James- I have some comments and huge interest in your EDIS switchover. I assume a 36-1 trigger wheel, yes? Did you mount the VR sesor on the timing cover plate. If not, where?
I've never understood why the MS doesn't just use and compare/average both the TPS and the MAP. Seems to me the way to dial that deal in pronto!
I set my trigger wheel behind the H balancer on first attempt: there's about 1/4 inch between H. balancer back face and timing cover, and the trigger wheel is about 1/8, so there you go.
Where the heck does a guy go to get an initial map for the MS? I have some possibly useable maps I've scrounged from the net off "google" searches if you want. Cheers, Vic
vem myers

Vem,

Please find attached a photo of a 60-2 trigger wheel on the B-series engine. The VR sensor is mounted on to the timing cover plate by captive bolts. This works very well and provides a good signal.


MG Mike

Hi Mike- Many thanx for the pix. Regarding your mount on the timing cover plate "by captive bots", just how did you do this? Was the cover removed with the H.Balancer/pulley, and tapped?. Just trying to get a working concept in my head. Thx, Vic
vem myers

Hi,

I marked the position of the mounting bracket on to the cover and drilled the two holes for the 1/4" UNF bolts. Once drilled, two sacrificial nuts and bolts were used to hold the two soon to be captive nuts in the correct place on the inside of the timing chain cover. (the clearance was previously checked using a piece of modelling clay) the two nuts on the inside of the cover were brazed in place to provide a good join and a oil tight seal. When finished, I ran a tap through the captive nuts and re-pained the cover. The bracket also has an oil gasket (just evident in the picture). It works well, is very ridged, doesn’t leak and gives a good signal.

Just one other point, the bracket is aluminium, the first one was steel, I have found that the VRS gives a better signal when fitted to a none magnetic bracket. My crank pulley is also aluminium with a steel trigger wheel.

Regards,

Mike.
MG Mike

Hi James,

Fitted an EDIS-4MGB supplied by Matt Kimmins (www.upgrades4mgs.co.uk/) on my daily driver (66 B GT). Works well, comes complete with program loaded and software, which you can change to suit your car.
Had a light 36-1 tooth ring laser cut from 5mm steel plate which I bolted to the front pulley (will send my profile drawing if required).
Mounted the VRS from a bolt within the fan belt area that also bolts the timing chain cover (close to the alt. adjusting stud). I prefer the VRS within the fan belt area as it greatly reduces the possibility of it being wiped out by the belt if or when it breaks.
I fitted a wire wound pot. as a TPS to the back carb. spindle, it’s simple and fault free. The software reads the engine load as the ratio between the throttle opening and the RPM and adjusts the ignition accordingly.
It's a fun project, have fun.

Regards,
Richard.


RH Davidson

MG Mike very nice. Im curious as to how you had the ehhem "AlYouMinEum" braket made, I must admit it looks lovely. Any dimension? Drawings ?

Vem, I have got as far as buying the parts, minus the Mega Jolt box.

Also from what I have read the Mega Jolt system does not have the TPS and MAP together due to it still being prototyped. They also have in the design a knocking sensor so the timing is not too far advanced.

Now I forgot what they are called but they are precise vacuum fittings I am able to get from my fathers job. The main question is where should it be running from, T connections ? only one vacuum point ? Pretty much Im looking for the ideal. I was thinking from both carbs with a t connection to the sensor. But that just sounds obvious, is their anything I am missing?

Also at http://www.upgrades4mgs.co.uk/ It says not to use MAP on the SU's due to the vacuum not being precise at idle ?

Thanks,
James
James

Hi James,

Drawing attached, if it is unreadable, I can send you a DXF or large JPG to an email address, just let me know.

The bracket is bespoke for my pulley and trigger wheel, you may have to adjust the dimensions to suit your own installation.

The first brackets I made were CNC’d from steel, the one in the picture was CNC’d from aluminium. If you adjust any of the dimensions, don’t forget to subtract the gasket thickness.

As for the MAP sensor, I previously used a MAP with the SU’s to great effect, it suppose it may depend of what EDIS you connect it to. I have fitted MAP sensors to many SU’d motors, Triumph and MGs with no problem. The connection on the MG was just directly to the top one of the inlet ports on the manifold using 4mm push-on vacuum tubing (Norgren).

Regards,

Mike.


MG Mike

Thank for the info ! Its the Ford EDIS4. And going to have the Megajolt box. The deciding factor on using the megajolt is price only. What have u used ?
James

Oh also now that im looking at the picture better, what exactly did you bolt up the machined piece for the VR to? Looks like there were no bolts there to begin with. What edis system did you use? And why did you mount the VR where you did...
James

The system I use is from DDS, made for race car applications, it is a bit overkill for an MGB but it does work very well.
MG Mike

The VRS has a location tag with a 6mm hole in it, the VRS fits in to the bracket and is secured by a 1/4 UNF cap headed bolt and lock washer. You can just see the tag on the original picture and the one attached to this post.

The VRS was mounted there as it was the only easy place to mount it! As far as my system is concerned, it does not matter where the sensor is, as long as it ‘knows’ the relationship between the VRS position and TDC, the system is constantly monitoring the engine speed (each 6 degrees) to determine crank position and engine acceleration/deceleration. The position relationship can be ‘fine-tuned’ to give an accuracy of less than 1/4 of a degree.


MG Mike

Thanks Mike,
Looks great. When I get mine all setup Ill post some pictures as well. Just might be a couple weeks. Still have other things to tend to with my B. But I cant wait. Out of curiousity what else have you done to your MG? Any pictures to share ?

James
James

James- I have 3 MS 2.2 kits, if you wanna go that way. If not, I'd be interested in which ECU you chose. Mike- excellent tip on mounting the VR using an AL bracket for signal clarity!
vem myers

Im just using the mega jolt system for my ignition, no plans of doing EFI, just a beautiful pair of SU's
James

You do mean the mega squirt box right ?
James

FYI - I have been using a Megajolt system on my Moss supercharged MGB engined car for over 5,000 miles. The VR senor picks up a signal from 32-1 ss bolts set into holea drilled into the flywheel. The VR sensor is fitted through a hole drilled into the bell housing and I ues TPS attached to the SU throttle spindle. The Negajolt ECU was designed and built by Matt Kimmins http://www.kimmins.info/

John
J Harle

Hi John- Do either you or Matt Kimmon's site have some pictoral aid for this implant. I have the SC flywheel off now for work. Perhaps your flywheel trigger is a great idea. Any help appreciated. Vic
vem myers

Nothing on Matts site is linking. Does someone have a url for the V4 software download? Vic
vem myers

Hello Vic,

The flywheel and VR sensor was made up and installed by Chris Betson of Octarine http://www.octarine-services.co.uk/ and look on his forum under EDIS for more details, you may have to join the forum to gain access.

I can say that the flywheel trigger set up has worked flawlessly on a car that is driven quite hard at times and has a FIRM suspension set up.

Pics attached of the flywheel and VR sensor installation. As there is a restriction of one pic per posting, I will post two more to follow:

John

J Harle

Vic - second pic.

John

J Harle

Vic - third pic.

John

J Harle

John- Thx, very helpful. He says he tapped and installed bolts? Is that correct? Is that to provide the high portion of the curve, the fly surface being the open portion I guess? Vic
vem myers

Vic,

Yes - the bolt heads form the "teeth" of the ring.
Chris at Octarine Services

Chris- With a lightened fly, will those 35 holes substantial weaken or allow warpage on the flywheel? I believe I will give it a try. Vic
vem myers

So Chris is the only one out there to use the flywheel as a trigger wheel? Vic
vem myers

Vic,

The holes are only 6mm dia and spaced around an inch apart, so there is plenty of strength left in the flywheel and there is no way the wheel can warp.

Because there is one bolt missing in the set the flywheel HAS to be rebalanced after fitting the bolts.
Chris at Octarine Services

Chris- Appropriate tip on the rebalance. Not intending to pick knits, just asking: should the space between the "teeth" be the same radial width as the teeth, or it's not such a huge deal? Regarding the 6mm holes then, I'd assume there's no problem taking the fly down 6-8 pounds in weight huh? Cheers, Vic
vem myers

Vic,

I normally only take about 4 lbs off the late flywheels, 6 lbs off the early ones.

The spacing between the teeth is immaterial as the software just counts the teeth and looks for the missing one to determine TDC.

Pegs could be used instead of hex head screws.

The latest development will use the edge of the flywheel lightening scoop to carry the "teeth" - I'll post pics once I have machined the first flywheel.
Chris at Octarine Services

Chris- Pressed pegs, yes. Then skimmed to true. Any adjust on fly lighten tech due to this wholly holey endevor? Vic
vem myers

Vic,

No, the lightening scoop should finish about 1/2 inch from the outer rim so as to support the ring gear - the pegs can be fitted in the unmachined rim.
Chris at Octarine Services

This thread was discussed between 31/07/2007 and 25/08/2007

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