Fatman

A mate of mine is restoring an old MG BGT. He's got a 1950cc overbored block, and we're wondering about the possibilities of turbocharging it. Apparently it's been done before (see here - with a TD05 blower, running circa 0.5 bar boost (estimated 174bhp).

The BGT uses a compression ratio of ~9.5:1, so we're considering dropping that a little by use of a thick 'spacer' gasket. This is to avoid expense of new rods. Hopefully the head studs are long enough (or cheap enough if the OEs are too short).

Now, if we're running a low boost pressure (say, 0.5 bar) could we get away without intercooling? Or, is this asking for trouble?

Current idea of parts list...

# Standard 1.75" SU Carb type inlet manifold
# Late type MGB exhaust manifold (modified with Adapter plate)
# 1.75" SU Carburettors (with uprated springs and different needles)
# Turbocharger
# Modified Exhaust downpipe with Turbo adapter plate
# Charge Pipe fabricated
# Boost Hose and Jubilee clips
# Cone type high-flow air filter
# Carburettor adapter plates (fabricated)
# Heat shield
# Exhaust insulating wrap
# Oil feed hoses
# Re-routed fuel lines
# Variable fuel pressure regulator
# Special, extra thick head gasket
# Boost gauge

What else might we have overlooked? Ideas and thoughts appreciated - even if it's "don't do it!", provided you can explain why.

[Edited by Fatman - 10/29/2003 1:57:31 PM]

The Zohan

I haven't heeard of anyone doing it before, used to be a member of the MGOC and MGCC few years back when i had various Sprites.

Most peiople bung in a V8 rover lump. Much lighter and more powerful with huge tuning potential over the 1.8 lump. TBH the brakes and suspension would need work, std BGT set-up is not up to much. They are easy to do, many parts and kits avaliable at reasonable prices.

Has your mate thought about supercharging?

Try the MGOC site
http://www.mgcars.org.uk/cgi-bin/gen5?runprog=mgoc&p=index.html.

Fatman

No, we've not considered supercharging thus far. We'll kick the idea around now, though .

Regarding the basic block, the start-point is the overbored 1800 (to 1950) lump. This was sold as a spare with the car (which has it's own stock 1800). The intention of the project is to do it without substantial outlay of cash.

If V8s are available for little money, then we'll consider it. However, so far - turbocharging the 1950cc seems the best value for money.

Fatman

Choice of turbo

Considering that we're not seeking epic levels of power, what factors should we consider ing choosing the turbo? Bear in mind we're not looking to invest much cash.

Would we be better off using a small turbo, or a larger one at lower pressure?

Paulo P

iTrader: (42)

You would be better off using a small turbo so that it spins up easier.

The big question about turbo charging an MG is WHY

misty

The old MG Metro turbo didn't have an intercooler! and it fed a single sealed S.U. If you found one at a scrappy, you could use that I bet!!
dave

Paulo P

iTrader: (42)

Good thought.

Fatman

...why not?

It's his second MG. The first is being restored to factory spec - completely faithful and original. The second car is just a fun project.

I agree that a smaller turbo would spin up quicker. However for the same boost pressure, would a larger turbo not give a lower charge temperature? That would probably be desirable if we're running without an intercooler - wouldn't it? Or, am I worrying too much about preignition?

Paulo P

iTrader: (42)

Why aren't you planning to run an intercooler?

Fatman

Mainly due to lack of space. Plus, I'm hoping that with low boost pressures we won't actually need one.

Scoob99

iTrader: (1)

try www.moto-build.co.uk they might be able to help as they do all tuning for M.G.'s
Cheers
Colin

Fatman

What about the Maestro Turbo...?

• Did they use carbs or fuel injection?
• Did they use an intercooler?

brickboy

At the low boost pressures you're talking about it's unlikely you'd need an intercooler. At least the plumbing will be easy 'cos it's not a crossflow head

You'll need to plumb in an oil feed to the turbo but you could tap into the oil cooler feed pipe quite easily ...

Sounds like a laugh, go for it!

misty

Fatmans right, my old montego turbo(ok no need to take the ****!!!)had an intercooler and fed a single 1 3/4 S.U. but the manifold is way different on the "O" series than the "B" series.
dave

MGJohn

Some people have successfully fitted O series engines to the MGB. Those 'people' included several Abingdon project cars when the factory were considering replacing the then ageing B series motors with the O series for the MGB. That was back in the mid-1970s and MGB production ceased later so no further progress. However, the O series was switched to later Princesses, Ambassadoors, Maestros and Montegos as well as Leyland Daf vans and diesel applications too. Oh yes, even the humble Morris Ital 1700HL had an in-line O series. I had one of these as a company car back then and it could shift by those day's standards... Some of these in-line O series units have made their way into MGBs with pleasing results.

The 8 valve O series lends itself to successful turbocharging.... witness the Maestro and Montego turbos .... which all have O series engines. O series have extremely strong bottom ends so moderate or higher tuning is rarely a problem. 200 bhp or more reliably obtained by many enthusiasts. In it's mid-1970s 'strangulated for the USA emissions market' rubber bumper form, the MGB produced about half the BHP that my first MG, a 1962 3-bearing UK spec car did in 1962!

The M16 and later T16 Rover engines are virtually O series with DOHC 16 valve heads and turbo versions of these have been tuned to exceed 400 bhp.

My first experience of the O series was back in the late 1970s; a 2000HL Princess. Remember the Wedge shape? Liked it from day one! The O series engine, in all it's various forms has a strong following with enthusiasts and around 25 years later, I'm still one of them... particularly in turbocharged form...

Fatman

I'm encouraged to hear that the bottom ends are strong. Our start-point is an overbored 1800cc B-series engine (to 1950cc). It's had some headwork, so that's what we'd like to stick with. However, I'd like to hear more about the fuelling on the turbocharged B- and O-series. Especially those run on carbs.

MGJohn

Production turbo-charged O series engines were all single carb ones. The later M16 and T16 variants were fuel injected. Why not post your queries here on these sites where there's a wealth of such information and knowledge:

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=41730134504047&mode=tlis t&subject=71

http://www.rovertech.net/forum/viewforum.php?f=1

Good luck with the project.

Dr Hu

As someone else posted earlier, you need a 'sealed' SU carb..... They had to make one specially for the MG Metro Turbo. The std SU's wont work properly as they rely on the Vacuum effect to lift the pistons, obviously as the turbo boosts you lose vacuum and go positive pressure.

They do work, but it has to be the special type.

misty

MGJohn. The bottom ends were very robust, but I seem to remember the oil feed to the cam shaft was very close to the end of the head gasket. Hence a lot of these engines wept oil from the right hand side of the cylinder head, which always needed a gasket change to cure!
dave

MGJohn

Misty Dave - true.... puzzles me why some engines are as dry as a bone there whilst others do leak but usually it's only a weep. I have two O series Turbos and one T16 Turbo which are tight as a .... there. Another leaked copiously - well a steady weep which was more unsightly than a problem because it was particularly noticeable in an otherwise spotless engine compartment. I didn't bother changing the gasket as the rest of the unit was fine. If it aint really broke ... Careful fitment of later spec head gaskets are the answer for this apparently...

Dr Hu is correct. Whilst outwardly similar to N/A SUs, the Turbo SUs are of special design for the turbocharging applications. Those early Montego Turbos are great fun to drive and still of reasonable performance by modern day standards despite being in their 19th year now.... There's still a good few about.

misty

Yes as you say, my Montego wept oil for two years, but I just used to wipe it once a week. My turbo 420gsi (t16) was as dry as a nuns c*nt though!
dave

Fatman

Thanks for the tips, gents. I'll look out for the carb from an early Montego Turbo or a Metro Turbo.

MGJohn

Fatman ....Back on thread:

See following updated post ...

[Edited by MGJohn - 10/31/2003 5:58:20 PM]

MGJohn

Fatman ....Back on thread:

>>The BGT uses a compression ratio of ~9.5:1, so we're considering dropping that a little by use of a thick 'spacer' gasket. This is to avoid expense of new rods. Hopefully the head studs are long enough (or cheap enough if the OEs are too short).<<

You're wise to reduce that CR. The old B series was prone to pink (pre-ign) even in mildly tuned N/A form. I know of one N/A O series EFi car converted to turbo use without lowering the ~9.0:1 compression ratio, but, to avoid melting the N/A pistons, was run on low boosts quite effectively. In any event, the owner was not too worried on that score, O series EFi engines are easy and inexpensive to obtain from breakers should he overdo the boost one day ...

Turbo O series engines have higher spec pistons of German origin IIRC - Mahle? - with compression ratios ~7.5/8.0:1. i.e. considerably lower than 9.5:1 ..

Also WROTE:

>>What about the Maestro Turbo...?

Did they use carbs or fuel injection? ...... CARB
Did they use an intercooler<<............... YES

NOTE:

Montego/Maestro Turbo SU carbs are fairly easy to obtain. Their essential plenums are like the proverbial .... because Mini enthusiasts put Metro Turbo engines in their car conversions but then need the lower angled Montego plenum and outlet because of clearance problems..... one tatty looking Montego plenum went on ebay recently for over 50 quid. Might be expedient to cheaply pick up an old Montego Turbo MoT failure (ensure car/engine is complete) and get all the bits you need from it.

[Edited by MGJohn - 10/31/2003 6:04:48 PM]

Fatman

Did the carb-fed Montego Turbo use an intercooler?

MGJohn

Yes, I have a couple of spares if you can't get fixed up locally ...

Scooby96

Why not stick in the Rover V8 mentioned above and turbo or supercharge that?!?!?!?