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MGB 3.4L V6 Swap. Original PCM or Megasquirt ?

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Paul755 Paul H
Fairfax, VA, USA   USA
1974 MG MGB MkIII
1979 MG MGB MkIV "Nemesis"
Im getting all the stuff ready for a 3.4L engine swap. I want to keep the SFI but keeping the original PCM is not my first choice, its a huge lump of 25 year old technology and I cant do my own tuning. Im leaning towards a Megasquirt V3. It lets me use the existing engine sensors, but I can tune the car to my liking. I have used a Megasquirt before and I have Tuner Studio.
Cost is not an issue.
What have you other engine swappers used ?

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Jim Blackwood Avatar
Jim Blackwood * BlownMGB-V8
Gunpowder Rd, Florence, KY, USA   USA
Talk with Brian about it before you make a decision, he's very familiar with the GM controller.

Jim

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V8MGBV8 Avatar
V8MGBV8 Carl Floyd
Kingsport, TN, USA   USA
In reply to # 3887589 by Paul755 Im getting all the stuff ready for a 3.4L engine swap. I want to keep the SFI but keeping the original PCM is not my first choice, its a huge lump of 25 year old technology and I cant do my own tuning. Im leaning towards a Megasquirt V3. It lets me use the existing engine sensors, but I can tune the car to my liking. I have used a Megasquirt before and I have Tuner Studio.

IMO, stay with the factory computer if you plan to stay near stock with the engine.

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BMC Avatar
BMC Gold Member Brian Mc Cullough
Minneapolis, Minnesota, USA   USA
Wouldn't you know it. I had a nice write up on this a few hours ago and MG Experience went down, taking my write up with it when I submitted it.

Custom tuning is not as great as most people make it out to be and OEM is usually better than most think. There is power to be gained with the factory computer, but there is just as much to gain with a slightly better camshaft. There really isn't going to be drastic power changes with aftermarket systems, but I've seen drastic cost increases when moving to these systems, part of that is literally shiny packaging. The draw that new must mean better. Sometimes it is, but not always. Sometimes it's better but not worth the high amount of frustration it causes. This is something that can be answered but,

1) The original question would be served better if we know the scope of the project.

2) 95% of the conversions with the 3.4L V6, the Ford Mustang 5.0L V8 or a Rover 3.5/3.9L V8 factory fuel injection only need stock systems and nothing more, but that's 95%, not 100% so the question is legitimate.

With those two items in mind, tell us about your Whole project. Not just the engine but what else you are going to do with the car so we can give you advice based on your project,
skills,
the 5 minutes or hours a day you get to do your own thing without interruption,
the unheated garage in Northern Canada with a single 60w light bulb swinging from a rope with a pair of vice grips and a 5 pound hammer
OR the fully equipped Air Conditioned 30,000 SF shop on the Gulf of Mexico with every fabricating tool imaginable.
You are a novice, old hat, technically skilled, mechanical aptitude of....
These things do change how we can help.

Examples of what some have said about their plans that would have an effect on how we can better advise you:

lighten it, add wider wheel wells and wheels, produce a 0-60 in under 5, 6, or 15 seconds, 3,500 or 8,000 RPM shift limit, flatten the hills, straighten the curves, autocross, freeway, round the lake car, high speed driving, cruiser at low speed, drag race, strip the interior and get the car down to below 1,500....

Your Plan is better than Our imagination to what we guess your plan is. :-)

-BMC.


Member Services:
Minnesota's only Fully Dedicated British Classic only shop providing Professional Restoration & Services & Specialty Products including- proper L.E.D. tail lights, Wiring looms and Engine and five speed Conversion Kits
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Paul755 Paul H
Fairfax, VA, USA   USA
1974 MG MGB MkIII
1979 MG MGB MkIV "Nemesis"
The project:-
Phase 1
1980 MGB Roadster , spring, summer and fall weekend driver. Occasional run to the NC Outer Banks beaches.
Swap the 1800cc MGB engine and O/D transmission with a 1995 Camaro L32 and its associated T5 transmission. Keep the SFI injection and DIS ignition system.
I have a 70K mile engine that I am rebuilding at the moment. I have an ARI Phase 2 cam kit from a previous unrelated project that is sitting on a shelf. Might as well use it. The Transmission will get a master overhaul kit from the "Gear Box Transmissions" shortly. Not installing A/C.
I will keep the MGB standard instruments, I will use a mechanical speedo driven gear on the transmission ( 10% fast - ~1098 TPM with a 3.9 rear and 14" wheels ). I will use a 2/3 pulse converter for the Tach.
I do have a full Camaro original engine wiring harness in good condition along with the PCM

On the list to buy over the next couple of months.
Lightened flywheel (BMC )
Drive shaft ( BMC)
HTOB ( BMC)
Engine mount & header kit ( BMC or CCE)
Alternator drivers side mounting/idler pulley kit (CCE )
Alloy rocker covers (CCE)
All the bits I dont know I need yet (BMC, CCE, ARI)
New MGB GT 4 pot front calipers ( on order from MGOC the UK). + Mintex Pads
Fab-Tek dropped spindles.
Suplex 8.75" 440 lb springs/ parabolic rear springs.


Phase II - next year
Build a new 3.4L L32 with a bit more HP but a bigger bump in torque
Roll bar - 3/4 maybe..
Dual pipes
Change the rear end . Ratio TBD
Anti tramp bars.
15" x 6" VTO wheels
Andy Jennings dash.

1000 sq ft heated and cooled garage with most tools + MIG and TIG . 3D Printer, engine crane etc.
Now, I just have the MGB, a restored 1977 Triumph Bonneville, and my MV Agusta F4. I have restored 1 MGB, 2 MG TD's and 2 MG TF's over the past 15 years.

I am very comfortable with the Megasquirt, I have used it on several engines with pretty good results. I am wondering about the original GM PCM, its 30 year old technology and it cannot be simply reconfigured or modified. I have to send it to BMC just to get it to work with the 3.4L in the MGB. Not that it is expensive, but I would prefer to have the ability to make my own changes. I also like the ability to use Tuner Studio in the 'Learn" mode and then tweek the maps with my laptop on the fly.

I can modify the existing wiring harness for the Megasquirt or build a new one.

So that's it.









In reply to # 3887700 by BMC Wouldn't you know it. I had a nice write up on this a few hours ago and MG Experience went down, taking my write up with it when I submitted it.

Custom tuning is not as great as most people make it out to be and OEM is usually better than most think. There is power to be gained with the factory computer, but there is just as much to gain with a slightly better camshaft. There really isn't going to be drastic power changes with aftermarket systems, but I've seen drastic cost increases when moving to these systems, part of that is literally shiny packaging. The draw that new must mean better. Sometimes it is, but not always. Sometimes it's better but not worth the high amount of frustration it causes. This is something that can be answered but,

1) The original question would be served better if we know the scope of the project.

2) 95% of the conversions with the 3.4L V6, the Ford Mustang 5.0L V8 or a Rover 3.5/3.9L V8 factory fuel injection only need stock systems and nothing more, but that's 95%, not 100% so the question is legitimate.

With those two items in mind, tell us about your Whole project. Not just the engine but what else you are going to do with the car so we can give you advice based on your project,
skills,
the 5 minutes or hours a day you get to do your own thing without interruption,
the unheated garage in Northern Canada with a single 60w light bulb swinging from a rope with a pair of vice grips and a 5 pound hammer
OR the fully equipped Air Conditioned 30,000 SF shop on the Gulf of Mexico with every fabricating tool imaginable.
You are a novice, old hat, technically skilled, mechanical aptitude of....
These things do change how we can help.

Examples of what some have said about their plans that would have an effect on how we can better advise you:

lighten it, add wider wheel wells and wheels, produce a 0-60 in under 5, 6, or 15 seconds, 3,500 or 8,000 RPM shift limit, flatten the hills, straighten the curves, autocross, freeway, round the lake car, high speed driving, cruiser at low speed, drag race, strip the interior and get the car down to below 1,500....

Your Plan is better than Our imagination to what we guess your plan is. :-)

-BMC.

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BMC Avatar
BMC Gold Member Brian Mc Cullough
Minneapolis, Minnesota, USA   USA
Personally, I think the list helps a ton.

One recommendation I would suggest is make sure that the rear end and suspension items are complete and good while the original engine is in. More power without finishing up all the rest of the items on your list would make it feel like more power would be a waste or you might build another engine to the way the car feels with the stock rear end ratio and suspension handling.

Anyways...
So you're qualified for the MS system and you have the facilities to do it in as well- that can be a step in that direction.

Is it required or will it help in the future? If you are going well and Far beyond what you are listing right now then maybe- but it would have to be quite a way. Right now, unless this cam is vastly over the cams that are sold at Jegs, Summit, Speedway and all the others then maybe, but I doubt it as it sounds like there is not a huge list of improvements to the engine outside of this.

I have not, so far, used the stock PCM for Turbo or supercharger but others have and eventually I will and believe this PCM is capable. (It's also capable of lean burn- something that GM went through their own mini-dieselgate scandal over) We've pulled more power and torque with the stock PCM and they have been stone reliable. I don't think that anyone is going to wake up a lot more power with the aftermarket ECU. Would you build it as it is now- Sequential fire, or move back to batch fire? Would it take a separate system to operate the ignition system? Are there .bin files available for this series of engine or do you start from scratch? Cost of one over the other?

The price is probably about the same when Everything is purchased MS3 considering wiring, plugs, computer, building the computer, solder and all the shop supplies most do not consider in the DIY ECU kit costs vs. BMC which is done, there is more learning factor and extended time building on MS3 when compared to BMC.
- OR you could build the system from the stock GM wiring loom you already possess and the system would be the cost of replacement pigtails that are always broken and some other basic items, the stock system wins on either plug and play (from us) or super inexpensive (when you DIY) system over the MS. That said, the MS is maybe the part of the time factor you want: you want to take time to build your own wiring loom and tune the system and have a sense of accomplishment. There is no "Right" answer for everyone here- the question to figure out what you want is:

How far are you going to take this engine? Very Radical? Maybe MS.
Standard to wild? BMC or DIY GM rebuild wiring/PCM.
How much time do you have and when do you want to be able to Drive the car reliably from coast to coast?
Do you have the time (patience!) in your life to solder a MS3 ECU together and build a wiring loom plus tune the car now?
What would you add that the MS or stock PCM will not drive that would lead you to take a direction in the future?

-BMC.


Member Services:
Minnesota's only Fully Dedicated British Classic only shop providing Professional Restoration & Services & Specialty Products including- proper L.E.D. tail lights, Wiring looms and Engine and five speed Conversion Kits
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Jim Blackwood Avatar
Jim Blackwood * BlownMGB-V8
Gunpowder Rd, Florence, KY, USA   USA
What year is your engine and OEM controller?

I'm no expert on GM controllers, I can assume the V8 and V6 controllers are not interchangeable but don't know if that always applies. However, I've been learning. The 0411 controller used in '01-'03 can be tuned from a laptop, there is info about it in the "Inexpensive EFI" thread:
https://www.mgexp.com/phorum/read.php?40,3879901,page=3

I would think the V6 controllers of the same series would be similar, you might want to look into those. I know it can also be retrofitted to vehicles with the previous "black box" controllers with just a couple of pins swapped. It also has on-the-fly tuning, auto-learn, and data logging capabilities. In short, very likely everything MS has and more. Great strides are presently being made in enthusiast tuning but I believe all of the parameters are known. Not sure about things like 2/3 bar MAP sensors, dual WB-O2 and the full range of input/output capabilities but that could be because I haven't learned about it yet.

Seems to me like a decent option.

Jim

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cstrong45 Avatar
cstrong45 Charles Strong
Bainbridge Island, WA, USA   USA
I have used the GM EFI for 5 years with no ill effects and it came free with the motor. I know of guys that wanna tweak the system but I doubt anyone can do a better job than GM in building EFI controller for their product. jest saying.

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Paul755 Paul H
Fairfax, VA, USA   USA
1974 MG MGB MkIII
1979 MG MGB MkIV "Nemesis"
The other option that is available would be the new FiTech 2 bbl throttle body on top of a CCE upper manifold and Edlebrock lower manifold with possibly a Ford EDIS-6 ignition setup. I have the EDIS4 with a MegaJolt ECU on my current MGB engine and it has been rock solid. I would reuse the MegaJolt ECU for the V6 EDIS6 ignition.
As this is a new product from FiTech, it would be an interesting project. The FiTech does have timing control, and I could use it with something like an MSD CDI and MSD distributor rather than the Ford EDIS6 system. I am usually averse to being a pioneer, it brings images of being face down in the mud with a back full of arrows.
Cost wise the FiTech is $800 and there is the upper and lower manifolds to add to the cost. That will take it to around $1.2K which is comparable with the other options available.
Still thinking which way to go.

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bills Avatar
bills Bill Spohn
W. Vancouver, , BC, Canada   CAN
Agree that unless you are going to do some pretty extensive mods, sticking with the GM ECM is the way to go.



Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (350 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC

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Paul755 Paul H
Fairfax, VA, USA   USA
1974 MG MGB MkIII
1979 MG MGB MkIV "Nemesis"
I have access to an 80K mile 2002 3400 V6 Pontiac Grand Am GT that has been hit up the rear, For my planned phase II engine build, I was thinking of putting the Grand Am 3400 heads and intake on my spare 3.4L RWD short block. The Gen III alloy heads flow much better than the stock 3.4L heads, there will be changes needed to the stock PCM 3.4L tune. If I stay with the original PCM I will get a Tuner Cats OBD I kit, so maybe that is all I need.

In reply to # 3888648 by bills Agree that unless you are going to do some pretty extensive mods, sticking with the GM ECM is the way to go.

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Ichi Avatar
Ichi Scott Martin
Kenora, ON, Canada   CAN
Paul,
It is my understanding that just putting fwd heads and intake on a rwd block will raise your compression ratio far too much to run regular fuel without major problems. You may want to do a full hybrid and just use the rwd block, and through everything from the fwd into it- cam, crank, pistons, rods, head, intake, etc.
Scott
P.s. there is a kit out there that will put an untouched fwd engine in the mg. I may do that if I feel I need more power than the rebuilt 3.4 I am planning on putting in mine. (but I am a mechanic and have more time than money)

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Paul755 Paul H
Fairfax, VA, USA   USA
1974 MG MGB MkIII
1979 MG MGB MkIV "Nemesis"
Thanks for the info. From what I understand there are several Gen III head versions and all have smaller chambers ( 38cc and ??cc ) than the iron heads. I agree that the best way is to just keep the the RWD block and transplant the guts of the 3400 engine. I'm leaning towards using a FiTech TBI with a Megajolt Ford EDIS-6 ignition, the idea appeals to me rather than using the original SFI or a Holly 390CFM carb.


In reply to # 3889475 by Ichi Paul,
It is my understanding that just putting fwd heads and intake on a rwd block will raise your compression ratio far too much to run regular fuel without major problems. You may want to do a full hybrid and just use the rwd block, and through everything from the fwd into it- cam, crank, pistons, rods, head, intake, etc.
Scott
P.s. there is a kit out there that will put an untouched fwd engine in the mg. I may do that if I feel I need more power than the rebuilt 3.4 I am planning on putting in mine. (but I am a mechanic and have more time than money)

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Ray Bee Avatar
Ray Bee Ray B
Cobourg, ON, Canada   CAN
I just completed my 3.4/3500 hybrid build. The following is what I used for parts.
-bottom end from 3.4l (94 Firebird)
-3400 pistons (needed to keep compression at 9.1:1)
-3500 (LX9) aluminum heads and LIM
-3400 UIM , throttle body and DIS
-stock ECM (ODB 1.5) with some initial tuning.
-custom headers similar to what is sold for the 3.4L but with 1.625" primaries.
-custom ground cam.
Lots of info about these kind of builds on the internet. At this moment I have run this engine for about 2 hrs on an engine test stand to allow cam break-in and some initial ECM tuning. Will be installing it into my 79 MGB this summer them complete the ECM tuning.
hope this helps
Ray

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Paul755 Paul H
Fairfax, VA, USA   USA
1974 MG MGB MkIII
1979 MG MGB MkIV "Nemesis"
Thanks, for the info. I will hunt around for an LX9 3500 top end.

In reply to # 3889670 by Ray Bee I just completed my 3.4/3500 hybrid build. The following is what I used for parts.
-bottom end from 3.4l (94 Firebird)
-3400 pistons (needed to keep compression at 9.1:1)
-3500 (LX9) aluminum heads and LIM
-3400 UIM , throttle body and DIS
-stock ECM (ODB 1.5) with some initial tuning.
-custom headers similar to what is sold for the 3.4L but with 1.625" primaries.
-custom ground cam.
Lots of info about these kind of builds on the internet. At this moment I have run this engine for about 2 hrs on an engine test stand to allow cam break-in and some initial ECM tuning. Will be installing it into my 79 MGB this summer them complete the ECM tuning.
hope this helps
Ray

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